WO2014100705A1

WO2014100705A1 - Conserved off gas recovery systems and processes

Info

Publication number: WO2014100705A1
Application number: PCT/US2013/077174
Authority: WO
Inventors: Mark William Dassel
Original assignee: CENTROTHERM PHOTOVOLTAICS USA Inc
Current assignee: CENTROTHERM PHOTOVOLTAICS USA Inc
Priority date: 2012-12-21
Filing date: 2013-12-20
Publication date: 2014-06-26
Anticipated expiration: 2015-06-21

Abstract

A process whereby vent gas from a polysilicon production reactor, the vent gas containing hydrogen, hydrogen chloride, silicon tetrachloride and possibly other components, is treated to provide components and reactants thereof useful as feedstock(s) for a polysilicon production reactor, which process avoids the use of multiple off gas recovery systems by, for example, directing substantially all of the hydrogen present in the vent gas into a converter, where the converter converts silicon tetrachloride to one or more of trichlorosilane and dichlorosilane.

Description

CONSERVED OFF GAS RECOVERY SYSTEMS AND PROCESSES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit under 35 U.S.C. § 119(e) of U.S.

Provisional Patent Application No. 61/745,415 filed December 21, 2012, which application is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to chemical processes and the associated equipment for making high purity polysilicon, and for recovering and reusing the by-products of the polysilicon manufacturing process.

BACKGROUND

[0003] The Siemens process is utilized in many commercial plants for the preparation of ultrapure polysilicon. In the Siemens process, high purity silicon rods are exposed to trichlorosilane (HSiCh, TCS) at about 1100°C. The TCS gas decomposes and deposits additional silicon onto the rods. This process produces extremely pure silicon, also called polysilicon or polycrystalline silicon, having impurity levels of less than a few parts per billion when the process is performed under optimal conditions. The Siemens process can be described by the chemical reaction:

4HSiCl₃ => Si + 3SiCl₄ + 2H₂

[0004] As shown by the above equation, silicon tetrachloride (SiCl₄, STC) is a byproduct of the Siemens process. In fact, STC is a byproduct that is generated in significant amounts, and it is essentially a waste material. The successful and economical conversion of STC into a useful material is essential in order for the Siemens process to operate in an economic and environmentally friendly manner. One option is to convert STC back into TCS, in an STC converter ("STC Converter"), so that TCS can re-enter the Siemens process. The desired reaction is: STC + H₂→ TCS + HCl. Unfortunately, the conversion of STC into TCS is typically incomplete and results in an exit stream comprising TCS in combination with DCS, HCl, hydrogen gas, and unreacted STC.

[0005] In a typical plant that operates the Siemens process, the exit streams from the Siemens process and from the STC conversion process are each separated into their component parts in order to effectively utilize those exit streams. Those separation processes are conducted independently, i.e., the equipment that is used to separate the component parts of the Siemens chemical vapor deposition (CVD) reactor off gas, and the equipment that is used to separate the component parts of the STC Converter off gas, are unique pieces of equipment. Thus, typical plants that operate the Siemens process have two off-gas recovery systems, which adds to the capital and operating costs of those plants.

[0006] In current industrial practice, three issues mitigate against feeding CVD off-gas to the STC converter (as currently practiced "Standard STC Converter"). First, quality suffers because hydrogen and TCS separated from the Standard STC Converter off-gas for recycle to the CVD reactor get contaminated with methyl and methyl- chlorosilanes, produced in the Standard STC Converter, which are difficult to remove. When recycled to the CVD reactor, the carbon in these compounds contaminates the silicon produced in the CVD reactor which reduces product utility. Second and third, both HC1 and TCS in the CVD off-gas are also products of the STC conversion reaction. Because the STC conversion reaction - as currently practiced in the Standard STC Converter - is an equilibrium reaction, HC1 and TCS in the CVD off-gas must be removed from the Standard STC Converter feed to obtain economically acceptable levels of conversion to TCS.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Features of the invention, including its nature and various advantages, will be apparent from the accompanying drawings and the following summary and detailed descriptions which identify various embodiments.

[0008] FIG 1 is a flowchart showing a system and process in accordance with the present disclosure.

[0009] FIG 2 is a flowchart showing a system and process in accordance with the present disclosure.

[0010] FIG 3 is a flowchart showing a system and process in accordance with the present disclosure.

[0011] FIG 4 is a flowchart showing a system and process in accordance with the present disclosure. [0012] FIG 5 is a flowchart showing a system and process in accordance with the present disclosure.

[0013] FIG 6 is a flowchart showing a system and process in accordance with the present disclosure.

[0014] FIG 7 is a flowchart showing a system and process in accordance with the present disclosure.

[0015] FIG 8 is a flowchart showing a system and process in accordance with the present disclosure.

[0016] FIG 9 is a flowchart showing a system and process in accordance with the present disclosure.

[0017] FIG 10 is a flowchart showing a system and process in accordance with the present disclosure.

[0018] FIG 11 is a flowchart showing a system and process in accordance with the present disclosure.

[0019] In these drawings and the following descriptions, various operational units are named and discussed, where those operational units are provided with unique reference numbers (Ref. No.) as set forth in the Table below, to aid in the reader's understanding. Corresponding reference numbers indicate corresponding parts throughout the drawings.

[0020]

TABLE

Operational Unit Name Ref. No.

Refrigerator/Decanter 17

Silica Gel Bed 10

STC Absorber Column 12

STC Converter (catalytic) 4

STC Converter (non-catalytic) 15

STC Converter Off-gas Scrubber Column 13

STC Vaporizer 25

STC/TCS Separator Column 7

TCS Absorber Column 3

TCS/DCS Separator Column 9

DESCRIPTION

[0021] The present disclosure provides processes, and manufacturing plants including systems and operational units by which those processes may be performed, that provide advantages in the production of polysilicon. In the present description, various operational units are identified and discussed. Those operational units will be described next in the context of the present disclosure, in order to aid in the reader' s understanding of the description which follows.

Operational Units

[0022] The system embodiments provided herein, and the process embodiments provided herein, each make use of operational units. As used herein, an operational unit receives one or more feedstocks, each comprising one or more chemical components, and acts on those feedstocks to produce one or more exits or vent gases which is/are different from the incoming feedstock(s). Operational units act upon feedstock as a whole or component(s) thereof, to achieve results, for example, the heating or cooling of a feedstock, the complete or partial separation of feedstock components into its components parts, or the conversion of a component of a feedstock into a different chemical entity. Operational units that achieve these results are named according to the results they achieve. As mentioned above, reference numbers have been assigned to various operational units, where those numbers are set forth in the Table above, and are used throughout the present descriptions and drawings.

Reactors

[0023] A reactor receives one or more feedstocks and causes a chemical reaction to occur whereby one or more components parts of the feedstock(s) is/are converted into different chemical entities. Reactors are also referred to as converters, since this type of operational unit converts a feedstock component into a chemically different component. As one example, a reactor may cause a chemical reaction between two components so as to form one or more different components. The systems, plants and processes described herein may make use of the following reactors/converters .

[0024] A Chemical Vapor Deposition (CVD) reactor may be used to perform or operate the Siemens process, as is well known in the art. In the Siemens process, a reactor containing rods formed from polysilicon, sometimes referred to as slim rods, is heated to a temperature in the range of 900-1100°C. TCS and hydrogen are introduced into the reactor, wherein the TCS decomposes and deposits highly pure polysilicon on the polysilicon rods. The by-products from the reaction are hydrogen chloride, STC, unreacted TCS, and usually some DCS

[0025] A Fluidized Bed (FB) reactor may also be used to produce polysilicon from TCS, although it operates differently from a CVD reactor. In an FBR, particles (for example, polysilicon particles) are maintained in a fluidized state while being exposed to TCS and H₂. The TCS decomposes to form a polysilicon coating on the particles. The by-products from the reaction are hydrogen chloride, STC, unreacted TCS, and DCS. The process and systems of the present disclose may be applied, or used, for treating vent gas from CVD or FBR polysilicon production, e.g., vent gas from an FBR fed trichlorosilane reactant. In the present disclosure and Figures, either of a CVD reactor or a FB reactor may be used to create a vent gas for treatment as disclosed herein, and Reactor (1) may be used to refer to either a CVD or FB reactor. While a system and method may be disclosed herein by reference to a CVD reactor for convenience, according to the present disclosure the same system and method may be used with a FBR.

[0026] In the accompanying drawings and description, the reference number (1) is used to specifically refer to each of the CVD Reactor and the Fluidized Bed (FB) Reactor independently, and also refers to any like reactor that produces polysilicon and emits by-products including hydrogen, hydrogen chloride and chlorosilane(s).

[0027] An HC1 Pipeline Reactor (2) converts HC1 and DCS to TCS, and/or converts HCL and TCS to STC. An HC1 Pipeline Reactor (2) is described in, for example, US Patent 5,401,872 where it may be referred to as a chlorination reactor, and the reaction performed therein referred to as a chlorination reaction.

[0028] An STC Converter (4 or 15) receives a feedstock comprising STC and hydrogen gas, optionally in admixture with other component(s), e.g., HC1, and converts some of that STC to TCS and DCS. The STC converter will typically not convert all of the incoming STC into TCS and/or DCS, and so the exit from the STC converter will typically contain some residual STC in addition to TCS and/or DCS. Unconverted STC is typically collected and recycled back to the STC converter. Furthermore, the exit from the STC converter will typically contain unreacted hydrogen gas and HC1. The STC converter may work on various chemical principles, two of which gives rise to embodiments described herein, namely the Catalytic STC Converter and the Standard STC Converter.

[0029] The Catalytic STC Converter (4) provides a relatively low temperature process for converting STC to TCS and other products. The process includes contacting feed gas comprising STC with a catalyst in a reactor, also referred to as a catalytic converter. The catalyst may be a metal catalyst, for example, shaped metal pieces with high aggregate surface area, or a fine wire mesh. The metal catalyst may comprise metal silicides, including without limitation chrome silicide, nickel silicide, and iron silicide. Optionally, the catalyst may be formed in situ, or in other words, the catalyst is formed within the reactor. In one embodiment, the reactor is charged with self-supporting metal, and at least a portion of the surface of that metal is converted to metal catalyst. In another embodiment, the reactor is charged with a fine wire mesh, and a part of or the entirety of the mesh is converted to metal catalyst. The process is run at low temperature, e.g., at a temperature of less than 700°C, for example, a temperature of from 100°C to 700°C, or from 300°C to 600°C, or from 400°C to 500°C, or about 500°C. The hold-up time of the feed gas in the reactor optionally ranges from 0.1 second to 20 seconds, or from 1 second to 10 seconds, or from 2 seconds to 5 seconds, or is about 3 seconds. The pressure within the reactor may range from 0.5 atmospheres absolute to 20 atmospheres absolute, or from 1.0 atmospheres absolute to 12 atmospheres absolute, or is about 6 atmospheres absolute. By selective control of the temperature and hold up time within the Catalytic STC Converter (4), the reaction may be run under non-equilibrium conditions, allowing for increased conversion of STC to TCS. [0030] Because the STC conversion reaction is endothermic, two alternative modes for operating the STC converter may are provided. In the first way, the reactor may be run adiabatically and the temperature of the feed gases is allowed to drop as the gases pass through the reactor and the conversion reaction occurs. In the second way, the reactor may be run isothermally. Isothermal operation requires the addition of heat to the reactor as the reaction occurs. Heat may be added in ways known to those well versed in the art, including passing the gases through metal tubes filled with catalyst and externally heating the tubes in a controlled manner, comprising electrical heating or heating with hot heating fluids or combustion gases. In a preferred embodiment of the Catalytic STC Converter (4), feed gas is formed by diluting STC with H₂ and then the feed gas is heated to within a few degrees centigrade of the exit temperature of the catalytic converter in a heat interchanger; these pre-heated feed gases are then heated to a few degrees above the exit temperature of the catalytic converter in a supplemental heater. The supplemental heater may be heated by means comprising direct fired gases, and electrical heaters, as two options. The hot feed gases are next fed to the catalytic converter where the reaction to gaseous products comprising TCS and HCl occurs. The hot gases exiting the catalytic converter may, in one embodiment, be used to preheat incoming STC and H₂ vapor in the heat interchanger. Alternatively, the exit gases may be cooled by any conventional means known in the art. The cooled product gases exiting the heat interchanger are then separated into constituent parts (e.g., TCS, HCl, and STC) for reuse in, for example, a polysilicon manufacturing plant. The STC separated from the catalytic converter exit gases may be recycled back to the catalytic converter system until completely converted to TCS.

[0031] The Standard STC Converter (15) utilizes high temperature, e.g.,

1100°C, and graphite heating rods to convert STC to TCS according to the following chemistry.

STC + H₂→ TCS + HCl (plus other by-products) This reaction takes place under high temperature (e.g., 1100°C to 1300°C), in capital intensive, electrically driven reactors (a.k.a., "hot converters") specially designed for the purpose. The high temperature is achieved by electrically heating graphite electrodes, located inside the reactors. The hot converters are costly to build and operate because of the required high temperature operation, relatively low conversion per pass (only 15% to 25% of the STC feed is converted to TCS per pass), and high maintenance cost (the electrode and graphite block insulation systems require frequent replacement due to wear and tear). The graphite electrodes also introduce unwanted carbon impurities into the TCS product stream, in the form of methane and/or methyl- chlorosilanes. Unless removed, the methane and/or the methyl-chlorosilanes travel with the regenerated TCS and/or recycle hydrogen back to the CVD reactor, where they can decompose and introduce unwanted carbon into the polysilicon product. Carbon contamination in polysilicon is undesirable because it can render the polysilicon unfit for use in the photovoltaic and semiconductor industries.

[0032] A Direct Chlorination Fluidized Bed Reactor, also referred to herein as

DC-FBR, is a fluidized bed reactor used to achieve a so-called "direct chlorination". In direct chlorination, hydrogen chloride (HCl) is reacted with metallurgic silicon (MGSi) to produce TCS and hydrogen (H₂) according to chemical reaction:

3 HCl + 1 MGSi→ 1 TCS + 1 H₂

Direct chlorination typically takes place in a fluidized bed reactor operating at 3 barg pressure and 300°C temperature. The reaction is catalyzed by molecular species comprising copper trichloride. The reaction proceeds to substantial completion, based on HCl conversion. STC is typically a by-product of the direction chlorination reaction, where the molar ratio of TCS: STC produced is substantially equilibrium controlled - contingent on a fluid bed reactor with sufficient hold up time. A problem faced by plants running the direct chlorination reaction is obtaining the starting HCl reactant in a pure form. According to current industrial practice, all materials in the Reactor off-gas and hot converter off-gas must be separated into substantially pure component streams to avoid co-feeding TCS, STC, and/or hydrogen with the HCl recycle - formed in these units - to the direct chlorination reactor, as co-feeding is thought to have deleterious effects. For example, it is believed that feeding TCS to the direct chlorination reactor results in over-chlorination, resulting in the unwanted production of additional STC. It is believed that feeding STC to the direct chlorination reactor results in the dilution of TCS in the reactor product, thereby necessitating unwanted additional STC/TCS separation distillation downstream of the direct chlorination reactor. It is believed that feeding hydrogen to the direct chlorination reactor complicates the off-gas treatment system, as hydrogen must be separated from TCS in the off-gas. Accordingly, the standard direct chlorination reaction is operated using highly pure HCl, where production of such high purity HC1 from, the off-gas from any of a Siemens' reactor or FB Reactor having TCS feed, or an STC Converter operating at high temperature, is expensive in terms of operating cost and equipment, since that off gas contains many components which must be separated from the HC1.

[0033] A Commutation Reactor (11) may be included within the systems of the present disclosure. Because the process of the present disclosure may, under certain operating conditions, make significant amounts of DCS along with TCS, and because excessive amounts of DCS when fed into a Chemical Vapor Deposition (CVD) or thermal converter may form excessive amounts of unwanted amorphous dust in the converter, a preferred optional embodiment of the present disclosure includes the separation of DCS from TCS as obtained from the converter. Optionally, the separated DCS may be converted to TCS in a Commutation Reactor (11), i.e., a reactor wherein DCS and STC react together to form TCS, optionally using a stoichiometric excess of STC. This process is referred to herein as commutation, although other terms such as redistribution, comproportionation and symproportionation may also be used. This process is essentially the opposite of a disproportionation reaction, wherein two molecules of trichlorosilane disproportionate to form one molecule each of

dichlorosilane and silicon tetrachloride. In the Commutation Reactor (11), two separate compositions may be directed into the reactor. One composition comprises dichlorosilane, for example, is a composition that is at least 50 wt dichlorosilane, while the other composition comprises silicon tetrachloride, for example, is a composition that is at least 50 wt silicon tetrachloride. Alternatively, a single composition is directed into the Commutation Reactor (11), where this single composition contains both dichlorosilane and silicon tetrachloride. The Commutation Reactor (11) is operated under commutation conditions (also known as

comproportionation, symproportionation or redistribution conditions), so that a commutation reaction occurs between the dichlorosilane and the silicon tetrachloride, and trichlorosilane is thereby produced. A catalyst may be present in the Commutation Reactor (11), e.g., a combination of tertiary amine and tertiary amine salt at disclosed in, e.g., U.S. Patent 4,610,858. As disclosed in US 4,610,858, the combination of tertiary amine and tertiary amine salt is used to allow for a disproportionation reaction, which is an equilibrium reaction whereby TCS may be converted to silane (SiH₄) and STC. The commutation reaction of the present disclosure may utilize the same catalyst and operating conditions of temperature and pressure as disclosed in U.S. 4,610,858, however unlike the reaction disclosed in U.S. Patent 4,610,858, the present disclosure introduces STC and DCS into the reactor, and recovers TCS as the product. A fixed bed or fluid bed reactor may be employed in the Commutation Reactor (11). Thus, in one embodiment of the present disclosure, exit streams are refined to provide a stream enriched in DCS. This DCS enriched stream may be directed to a Commutation Reactor (11), i.e., a reactor wherein commutation of DCS and STC to form TCS is accomplished. In one embodiment, the commutation is accomplished by contacting the DCS enriched stream with STC, to thereby form two molecules of TCS for each molecule of DCS and STC that enters the Commutation Reactor (11). In one embodiment, a stoichiometric excess of STC is contacted with the DCS enriched stream, in other words, each mole of DCS from the enriched stream is contacted with more than one mole of STC. In this way, the DCS in the enriched stream is more efficiently converted by STC to TCS. The stream that exits the commutation converter will contain TCS, typically in combination with STC, and also typically in combination with some, but preferably not too much, DCS.

Absorbers & Scrubbers

[0034] The construction and operation of absorbers is well known in the art.

Briefly, an absorber achieves the removal of one or more selected components from a mixture of gases. In one embodiment, referred to as a liquid/gas absorber, a soluble gas (the "solute") is scrubbed from a mixture of gases by means of a liquid, where the liquid may be referred to as the reflux liquid. Absorption columns or towers, also referred to as absorber columns or towers, are commonly used for gas absorption. Suitable design features for an absorber column include: cylindrical column with a gas inlet and distributing space at the bottom; a liquid inlet and distributor at the top; gas and liquid outlets at the top and bottom respectively; column packing to ensure intimate contact between the liquid and the gas (column trays are an alternative option); and packing support to provide strength to the operational unit. The shell of the column may be constructed from metal, ceramic, glass or plastic materials, and may incorporate a corrosion-resistant interior lining. The column should be mounted truly vertically to help uniform liquid distribution. The bed of packing rests on a support plate which desirably has at least 75% free area for the passage of the gas so as to offer as low a resistance as possible. The simplest support is a grid with relatively widely spaced bars on which a few layers of large raschig or partition rings are stacked. The column may include a gas injection plate designed to provide separate passageways for gas and liquid so that they need not compete for passage through the same opening. This is achieved by providing the gas inlets to the bed at a point above the level at which liquid leaves the bed. At the top of a packed bed a liquid distributor of suitable design provides for the uniform irrigation of the packing which is necessary for satisfactory operation. The packing should be selected so as to provide a large surface area for better contact between the gas and liquid. There is preferably an open structure in order to achieve a low resistance to gas flow. The packing should promote uniform liquid distribution on the packing material, and should promote uniform vapor gas flow across the column cross section. The packing may be random or structured. In operation, the inlet liquid, which may be a pure solvent or a dilute solution of solute in the solvent, is distributed over the packing uniformly by the use of distributors. The solute containing gas enters the distributing space below the packing and flows upwards through the spaces in the packing in the counter current to the flow of the liquid. The packing provides a large area of contact between the liquid and gas. The solute is absorbed by the fresh liquid (i.e., the reflux) entering the tower, and dilute gas leaves the top. The liquid reflux is enriched in solute as it flows down the tower, and concentrated liquid leaves the bottom of the tower through the liquid outlet.

[0035] The present disclosure refers to a TCS Absorber Column, identified by reference number (3), where STC and optionally HC1 is added to the column, the column also receiving a feedstock of STC, TCS, DCS, hydrogen and optionally HC1 from the Reactor (1). The present disclosure also refers to an STC Absorber Column, identified by reference number (12), where TCS and optionally DCS is added to the column, the column also receiving a feedstsock of STC, TCS, DCS and hydrogen from HC1 Absorber Column (5). In addition, the present disclosure refers to an HC1 Absorber Column (5) which separates hydrogen from hydrogen chloride, along with achieving partial separation of chlorosilanes. Using the TCS Absorber Column shown in Figure 1 as an illustration, this column receives a gaseous mixture of materials (e.g., STC, TCS, ¾ and optionally DCS) and a liquid "reflux material" which may be pure or multicomponent. In the case of the TCS Absorber Column shown in Figure 1, STC is the reflux material, and it is largely pure although it may contain some amount of TCS depending on, for example, the operating condition of the STC/TCS Separator Column. This STC reflux material may be referred to herein as "fresh STC" to distinguish it from the STC that is introduced into the TCS Absorber Column as a gas mixture, e.g., mixture 2A from the HCl Pipeline Reactor in Figure 1. The TCS Absorber Column will contain packing or multiple trays to assist in separating the components of the gas mixture (e.g., 2A). The higher boiling components of the gas mixture of materials will exit the top of the TCS Absorber Column, which in the present system and method will be hydrogen gas (exit stream 3A in Figure 1). The hydrogen gas that exits the TCS Absorber Column will be saturated with the reflux material, which in the present system and method will be STC. The temperature of the TCS Absorber Column is largely controlled by the temperature of the incoming gaseous mixture of materials and the incoming reflux material(s). At higher operating temperatures, the exit gas from the TCS Absorber Column will tend to contain a relatively greater amount of STC dissolved in the hydrogen. Typical operating temperatures for the TCS Absorber Column are from 20 to 100°C, e.g., 35-50°C where these operating temperatures are maintained by the heat of the incoming gas and liquid components (2A and 7B in Figure 1) such that external heating is not needed. The temperature should not be so hot that the components of the bottoms exit stream (3B in Figure 1) are in the gas phase; these components should be in the liquid phase as they leave the TCS Absorber Column. The pressure within the TCS Absorber Column is typically at or above atmospheric pressure.

[0036] The present disclosure also refers to an STC Converter Off-gas Scrubber

Column (13). In general, a scrubber (or scrubber column), commonly called a wet scrubber, contacts an incoming gas stream with a liquid solution to remove unwanted component(s) from the gas stream without a chemical reaction taking place. The unwanted components in the gas stream can be a solid, liquid or gas. When the unwanted components are solids then the removal mechanism is normally from adhesion of the fines solids to the surface of the liquid. When the unwanted

components are liquids and/or gases the removal mechanism is normally from absorption into the bulk liquid phase and the solubility of the unwanted component into the liquid solution is a critical factor. The contacting of the liquid and gas can be achieved with different methods including orifices, venturi sections, impingement plates, sprays nozzles, packing or distillation trays. The STC Converter Off-gas Scrubber Column removes TCS from the hydrogen stream using STC reflux. This enables efficient removal of substantially all chlorosilane from the hydrogen recycle stream to the Reactor by refrigeration where the refrigeration temperature does not have to be so cold as it would need to be if TCS or DCS were present because STC has a relatively much higher boiling point. The HC1 Absorber (5) removes the HC1 from the hydrogen recycle stream. The ability to remove chlorosilanes and hydrogen chloride from the hydrogen gas is required to achieve high quality polysilicon in the CVD (Chemical Vapor Deposition) reactor.

Separators

[0037] A separator acts on a mixture of component parts of a feedstock to separate the components from one another. The design and operation of a separator will depend on the physical properties of the component that is being utilized to achieve the separation, and the component that is being separated. For example, the separator may be able to separate the component parts based on the boiling points of the components. In this case, the separator is commonly called a distillation unit. The plants and processes described herein may make use of the following separators.

[0038] An STC/TCS separator achieves the separation of STC and TCS based on the difference in the boiling points of the two components. STC has a boiling point of 57.65°C while TCS has a boiling point of 31.8°C. These two components may therefore be separated using a distillation unit having a suitable number of theoretical stages. The design, manufacture and operation of distillation units, also known as distillation columns, is well known in the art. A convenient form for the STC/TCS separator is a column, and accordingly the term STC/TCS Separator Column is used herein to identify the STC/TCS separator, which is also identified by reference number (7). Likewise, a TCS/DCS separator achieves the separation of TCS and DCS based on the difference in the boiling points of the two components, and is conveniently in the form of a column. The terms TCS/DCS Separator Column is used herein to identify a TCS/DCS separator, which is also identified by reference number (9).

[0039] A decanter is a type of separator which in the present disclosure is used to separate liquids condensed from a non-condensable gas stream (e.g., hydrogen). Decanters are normally designed for continuous operation, and the Decanter disclosed herein preferably operates in a continuous mode. A great variety of vessel shapes is used for decanters, but for most applications a cylindrical vessel will be suitable, and will be the cheapest shape. Typical designs are the vertical decanter and the horizontal decanter. The feedstock may be cooled in order to achieve liquefaction of all or much of the condensable components of the feedstock, and a Refrigerator/Decanter refers to a decanter which is in fluid communication with a refrigeration unit such that the condensable components in the feedstock going to the decanter are cooled to a liquid state. The design, manufacture and operation of decanters are well known in the art. The present disclosure refers to a Refrigerator/Decanter (17).

[0040] An HCl recovery column functions to separate hydrogen chloride from chlorosilanes using distillation. Distillation is a method of separating mixtures based on differences in those components boiling temperature at the same pressure. This is a physical separation process where no chemical reaction occurs. Furthermore, this is a continuous distillation process in which the liquid mixture is continuously fed into the process and the separated fractions are removed continuously as output streams as time passes during the operation. Continuous distillation produces at least two output fractions, including at least one overhead distillate fraction and one bottom fraction. The distillate fraction being the lighter component that boils at a lower temperature is removed as a vapor and the bottoms fraction which boils at a higher temperature is removed from the bottom as a liquid. According to the present disclosure, there are at least three reasons why it is desirable to remove the hydrogen chloride from the chlorosilanes. First, the chlorosilanes can be used as the liquid feed solution to an HCl absorber column to remove hydrogen chloride from hydrogen gas and thus the hydrogen chloride content in the chlorosilanes must be reduced in order for the chlorosilanes to have the ability to absorber more hydrogen chloride. Second, chlorosilanes are recycled to two other unit operations, namely a CVD Reactor (or FB Reactor) and an STC Converter, where the presence of hydrogen chloride is undesirable because it negatively effects quality and or productively. Lastly, once hydrogen chloride is separated from chlorosilane(s) it can be recycled to and thereby recovered in unit operations that make chlorosilane, thus reducing production cost. The present disclosure refers to an HCl Recovery Column (6).

[0041] Similar to an HCl Recovery Column is an HCl Stripper Column. The

HCl Stripper removes HCl from the bottom stream exiting a preceding column (e.g., the TCS Absorber Column) and recycles it to the preceding column thereby forcing this light material to go overhead in the vapor stream exiting the top of the preceding column. Otherwise a small fraction of the HC1 entering the preceding column would escape out the bottoms of the preceding column (an unwanted event) while most of the HC1 would exit the top of the column (the desired event). Forcing all of the HC1 out the top of the preceding column is advantageous because it consolidates all of the HC1 entering the preceding column (e.g., again the TCS absorber) into one stream - the overhead stream - from whence it may then be isolated and recovered - e.g., in the HC1 Recovery Column - for reuse elsewhere in the process (e.g., in the direct chlorination reactors). The present disclosure refers to a HC1 Stripper Column (8) and in some instances a second HC1 Stripper Column (14).

[0042] A distillation column may be employed to separate one or more components from a mixture on the basis of boiling point. A distillation column heats the mixture such that the more volatile components are separated from the less volatile components. The present disclosure makes reference to a Distillation Column (19).

Adsorption Beds

[0043] A bed, also referred to an adsorption bed, is used to adsorb and remove contaminants from a gas stream. The adsorption bed will contain solid particles, often very small solid particles, which preferentially interact with one or more undesired solutes in a gas stream. Those contaminants bind to the solid particles, thus exiting the gas stream. The gas stream then exits the adsorption bed in a higher purity condition. The choice of solid particles will determine which contaminant(s) may be removed from which gas stream. Variables that must be kept in mind include flow rate of the gas, the thickness of the bed packing material, the void fraction, i.e., the relative volume of the bed that is open space, particle size of the solid particles, and the rate of transfer of a contaminant from the gas stream to the bed. Adsorption beds may be regenerative or non-regenerative. During adsorption, the gas stream passes through a layer or bed of highly porous material referred to as the absorbent. The design, manufacture and operation of adsorption beds are well known in the art.

[0044] The adsorption bed may contain carbon particles, for example activated carbon particles. When the absorption bed contains carbon particles, it is referred to herein as a Carbon Absorption Bed (18). Activated carbon particles interact with organic components of an otherwise inorganic gas stream, thereby removing the organic components and providing a higher purity inorganic gas stream. Activated carbon is commercially available from many sources. It can be prepared by starting with a carbon-containing raw material, such as wood or coconuts, and pyrolyzing the raw material in the absence of air and at very high temperature (e.g., 500°C) to drive off all volatile material. The resulting ash is activated upon exposure to steam, air or carbon dioxide at higher temperature, which enhances the porosity of the ash. The design, manufacture and operation of activated carbon adsorption beds are well known in the art.

[0045] The adsorption bed may contain silica gel, where the silica gel interacts with boron and phosphorous compounds present in a chlorosilane feedstock. When the absorption bed contains silica gel, it is referred to herein as a Silica Gel Bed. The present disclosure refers to a Silica Gel Bed (10). The boron compound(s), e.g., boron trichloride (BCb) is preferentially absorbed into the silica gel bed, thus generating a higher purity chlorosilane feedstock. Silica gels are made from sodium silicate.

Sodium silicate is mixed with sulfuric acid, resulting in a jelly-like precipitant from which the name "gel" comes. This precipitant is then dried and roasted. Different grades can be produced depending on the processes used in manufacturing the gel. Silica gels have surface areas of approximately 750 m²/gm. Silica gels are ineffective at temperatures above 500°F (260°C). The design, manufacture and operation of silica gel adsorption beds are well known in the art.

Compressor & Liquefaction Unit

[0046] A CVD (Chemical Vapor Deposition) reactor for the conversion of chlorosilanes to polysilicon has hydrogen gas as a feedstock as well as an effluent product. The purpose of the hydrogen recycle compressor is to increase the pressure of this effluent hydrogen to overcome the pressure drop of required auxiliary equipment so that the effluent hydrogen can be recycled and returned to the feed of the CVD reactor. The required auxiliary equipment -that creates this pressure drop - includes heat exchangers, cleaning equipment, process piping and values. The ability to recycle hydrogen gas to the CVD reactor greatly reduces the production cost of operating the CVD reactor and is a preferred although not required feature in the systems and processes of the present disclosure. The present disclosure makes reference to a ¾ Recycle Compressor (16). [0047] Liquefaction of gases is a physical conversion of the gas into a liquid phase or state. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling to reduce the temperature. Lower temperature boiling gases such as air or hydrogen require very high pressure and very low temperatures to reach a liquid phase. The present disclosure provides for HC1 liquefaction as an optional step in the systems and processes disclosed herein. The main goal of HC1 liquefaction in these processes is to greatly increase the density of the hydrogen chloride in order to greatly reduce the volume and capital cost of storage tanks. The present disclosure makes reference to an HC1 Liquefaction Unit (20).

Temperature Controller

[0048] Temperature control can be achieved by many methods, and the design, manufacture and operation of temperature controllers is well known in the art. Heat exchangers, cooling towers, chillers, boilers, electric and other types of heaters, and heat pumps are a few of the well-known temperature controllers used in industrial processes, any of which may be used in the systems and methods of the present disclosure. Temperature controllers may be used to cool a fluid or to heat a fluid, including heating or cooling to convert between gaseous and liquid states. For example, a vaporizer may be used to heat a liquid fluid to a gaseous state. One such temperature controller is an STC Vaporizer (25) which heats STC to a temperature such that the STC is entirely in the vapor (gaseous) state. As another example, the systems and methods disclosed herein are, in many instances, described with the inclusion of heat exchangers. Heat exchangers are specifically noted as operational unit numbers (21), (22) and (23) in the drawings and description provided herein. In each of the systems and methods disclosed herein, one or more of those heat exchangers may be omitted. Likewise, additional heat exchangers may be added in instances where it is convenient and desired to transfer heat from a hot fluid to a relatively cool fluid. Heat exchangers come in the plate, spiral and shell-and-tube varieties, any of which may be used to provide heat exchange. While heat exchange is one way to heat up a fluid, alternatively a Heater may be used, where the present disclosure makes reference to Heater (24). Summary Description

[0049] The present disclosure provides systems and process for producing polysilicon that have many advantages. Current industrial practice employs two costly, duplicate vent gas treatment systems, each with its own vent gas cooling, liquid decantation, HCl absorption, gas and liquid refrigeration, HCl recovery, STC and TCS separation, TCS recycle system, and hydrogen gas recompression and recycle systems. The first of these two duplicate systems is used to treat vent gas leaving the CVD reactor(s), and produces separate hydrogen, TCS, and STC streams. The second duplicate system mixes STC separated in the first system with a second hydrogen gas source, and converts the admixture to TCS in an STC Converter. This duplication requires twice as much capital and costs twice as much to operate. The present invention disintermediates current practice by, for example, utilizing a single TCS absorber column, to replace the first of the two aforementioned duplicated systems, and only one vent gas treatment system. In this way, CVD vent gas is fed to the STC Converter.

[0050] The present invention overcomes problems faced by existing processes by at least one or more of the following ways:

• The STC Converter may be operated as a low temperature, catalyzed, non- equilibrium reactor ("Catalytic STC Converter" or STC Converter). Because a reactor of this type employs no carbon or graphite, carbon contamination is avoided. See WO 2013/074425.

• HCl in the CVD off-gas may be reacted to extinction, with DCS and TCS forming TCS and STC, in an HCl Pipeline Reactor located downstream of the CVD or FB Reactor. For reasons already described, this approach is preferable when using a Standard STC Converter. Alternately, the STC Converter may be operated as a Catalytic STC Converter. In this type reactor, HCl normally present in the CVD off-gas is of secondary importance; as a result, HCl in CVD off-gas may be tolerated in the Catalytic STC Converter feed without significant deleterious effect on the efficiency of STC conversion to TCS. This alternate approach is advantageous because none of the TCS in the CVD off-gas is reacted to STC, which STC must in turn be re-converted to TCS in the STC Converter.

• TCS in the CVD off-gas is removed from the hydrogen stream in a TCS absorber column, where TCS is interchanged with STC. This has two beneficial effects: (1) TCS is removed from the STC Converter feed, which could otherwise back-react with HCl produced in the STC conversion process producing unwanted STC, and (2) the interchange of TCS with STC in the hydrogen gas stream exiting the TCS absorber reduces the heat load required to vaporize STC in STC Converter feed. Thus the use of a TCS absorber is a low cost, highly efficient means to remove TCS from STC Converter feed.

[0051] For example, in one aspect, most or all of the hydrogen present in an exit stream from a CVD reactor is directed into an STC Converter. In various embodiments, at least 50%, or at least 60%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 99%, or 100% of the hydrogen leaving a reactor is directed into an STC Converter. The STC converter may work on various chemical principles, two of which gives rise to embodiments described herein, namely the Catalytic STC Converter and the Standard STC Converter. As it exits the reactor, the hydrogen may be in combination with other chemicals, for example, chlorosilane(s) and/or HCl. In various embodiments, the hydrogen leaving the reactor is in

combination with HCl; with chlorosilane(s); with HCl and chlorosilane(s); with STC; with STC and HCl; with STC and TCS; with STC, TCS and HCl; with STC, TCS and DCS; with STC, TCS, DCS and HCl. The hydrogen may be present in an exit stream from a reactor that operates the Siemens process for polysilicon production, which typically also contains HCl and chlorosilane(s). In each of the embodiments disclosed herein, the first and second vent gases may or may not contain DCS. DCS is typically present in a vent gas from a polysilicon-producing reactor or an STC Converter, however under specialized conditions DCS may not be present in appreciable quantities and the systems and processes of the present invention are applicable to vent gases that do or do not contain DCS. The STC Converter receives a feedstock comprising STC and hydrogen gas, optionally in admixture with other component(s), e.g., HCl, and converts some of that STC to TCS and typically DCS. The STC Converter will typically not convert all of the incoming STC into TCS and/or DCS, and so the exit from the STC converter will typically contain some residual STC in addition to TCS and/or DCS. Unconverted STC is typically collected and recycled back to the STC converter. Furthermore, the exit from the STC Converter will typically contain unreacted hydrogen gas and HCl. Optionally, the hydrogen gas exiting the reactor is directed through one or more operational units prior to entering the STC Converter. For example, the hydrogen may be directed through an HCl Pipeline Reactor and/or a TCS Absorber Column and/or a Heat Exchanger; and/or a Refrigerator/Decanter. In one embodiment, the hydrogen passes through an HCl Pipeline Reactor and a TCS

Absorber Column (3) after exiting the reactor and before entering the STC Converter. In another embodiment, the hydrogen passes through an HCl Pipeline Reactor, a TCS Absorber Column, and a Heater after exiting the reactor and before entering the STC Converter. In another embodiment, the hydrogen passes through an HCl Pipeline Reactor, a TCS Absorber Column, a Heat Exchanger and a Heater after exiting the reactor and before entering the STC Converter. In another embodiment, the hydrogen does not pass through an HCl Pipeline Reactor, but does pass through a TCS Absorber Column, and thereafter optionally passes through one or both of a Heater and a Heat Exchanger, before entering the STC Converter. In another embodiment, the hydrogen passes through an HCl Pipeline Reactor, a Refrigerator/Decanter, and optionally one or more Heat Exchangers and Heater, before entering the STC Converter. In all cases, most or all of the hydrogen exiting the CVD or FB Reactor, enters the STC Converter.

[0052] In one aspect, the present disclosure provides a process comprising:

a. producing a first vent gas comprising STC, TCS, HCl and H₂; optionally DCS is also part of the first vent gas; the first vent gas is optionally produced in a Reactor such as a CVD Reactor or a Fluidized Bed Reactor wherein polysilicon is produced and STC, TCS, HCl and H₂ (and optionally DCS) are by-products of the polysilicon producing reaction;

b. separating components of the first vent gas or a portion thereof to provide at least two separate mixtures, one mixture being referred to as the first exit stream and comprising at least 75% of the H₂ present in the first vent gas and also optionally comprising at least 50% of the STC present in the first vent gas, and the other mixture being referred to as the second exit stream and comprising at least 50% of the TCS and optionally at least 50% of the DCS present in the first vent gas; and

c. feeding the first exit stream comprising STC and H₂ to an STC Converter to provide a second vent gas comprising STC, TCS, DCS, HCl and H₂.

[0053] In optional embodiments of this aspect, one or more of the following features may be used to describe the process of the present disclosure: the first vent gas is produced from a CVD reactor to which is fed TCS and wherein is produced polysilicon; the first vent gas is treated to remove (i.e., remove some, most or essentially all of) the HCl from other components of the first vent gas, to provide an HCl-depleted first vent gas (i.e., some amount of the HCl, preferably most of the HCl, is removed from the first vent gas to produce the HCl-depleted first vent gas) which is a portion of the first vent gas; the first exit stream is in the gas phase; the second exit stream is in the liquid phase; the separating comprises feeding the first vent gas or a portion thereof to a TCS Absorber Column where optionally fresh STC is fed into the TCS Absorber Column; the first exit stream comprising at least 75% of the H₂ also comprises HCl in addition to optionally comprising at least 50% of the STC; the second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS is fed into an STC/TCS Separator Column; the second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS also comprises HCl where optionally this mixture is fed into an HCl Stripper Column which provides an HCl- depleted mixture comprising STC and TCS, where optionally the HCl-depleted mixture comprising STC and TCS is fed into an STC/TCS Separator Column; the first exit stream comprising at least 75% of the H₂ present in the first vent gas and optionally also comprising at least 50% of the STC present in the first vent gas is fed into an STC Converter to provide a second vent gas comprising STC, TCS, HCl and H₂, and optionally DCS, where optionally a portion of the STC and TCS of the second vent gas is fed into an STC/TCS Separator Column; the second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS is fed into an STC/TCS Separator Column; the second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS is fed into an STC/TCS Separator Column while a portion of the second vent gas comprising STC and TCS is fed into the STC/TCS Separator Column; the second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS is fed into an HCl Stripper Column to provide an HCl-depleted mixture of TCS and DCS while the HCl-depleted mixture of TCS and DCS is fed into an STC/TCS Separator Column, while a portion of the second vent gas comprising STC and TCS is fed into the STC/TCS Separator Column; the STC Converter comprises metal silicide catalyst and is operated in a non-equilibrium mode. It should be mentioned that when an exit stream or a vent gas is said to be "fed into" an operating unit, this exit stream or vent gas may optionally pass through one or more unspecified operating units before it is fed directly into the named operating unit. For example, the present disclosure provides that the exit stream from the STC Converter is fed into an STC/TCS Separator Column, however, that exit stream from the STC Converter may optionally first pass through an HC1 Absorber Column and then an HC1 Recovery Column, as shown in Figure 1 , before being fed directly into the STC/TCS Separator Column.

[0054] In a related aspect, the present disclosure provides a system comprising:

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor, the Reactor producing polysilicon and a vent gas comprising silicon tetrachloride (STC), trichlorosilane (TCS), hydrogen chloride (HC1) and hydrogen (H₂), and optionally producing dichlorosilane (DCS);

b. a TCS Absorber Column in fluid communication with the Reactor, wherein the TCS Absorber Column receives i) the first vent gas from the Reactor or a portion thereof and ii) a fresh portion of STC from, for example, an STC/TCS Separator Column, and wherein a first exit stream comprising at least 75% of the H₂ and optionally at least 50% of the STC present in the first vent gas, and a second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS present in the first vent gas, both exit the TCS Absorber Column; and

c. an STC Converter in fluid communication with the TCS Absorber Column, where the STC Converter receives the first exit stream from the TCS Absorber Column and provides a second vent gas comprising STC, TCS, HC1 and H₂, and optionally also comprising DCS.

[0055] In optional embodiments of this aspect of the present disclosure, one or more of the following features may be used to further describe the system: an HC1 Pipeline Reactor is located between, and is in fluid communication with each of the Reactor and the TCS Absorber Column; an STC/TCS Separator Column as mentioned in step b. above, is in fluid communication with each of the STC Converter and the TCS Absorber Column, where exit streams or fractions thereof from the STC Converter and the TCS Absorber Column are each fed into the STC/TCS Separator Column; an HC1 Stripper Column is located between, and is in fluid communication with each of the TCS Absorber Column and the STC/TCS Separator Column; the STC Converter is in fluid communication with and provides the second vent gas to an HC1 Absorber Column; the STC Converter is in fluid communication with and provides the second vent gas to an HC1 Absorber Column while the HC1 Absorber Column is in fluid communication with and provides HC1, STC and TCS, and optionally DCS, to an HC1 Recovery Column, while the HCl Recovery Column is in fluid communication with and provides STC and TCS, and optionally DCS, to the STC/TCS Separator Column.

[0056] In one aspect, the present disclosure provides a system comprising:

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor, the Reactor producing a vent gas comprising STC, TCS, HCl and H₂, and optionally also producing DCS;

b. a TCS Absorber Column in fluid communication with the Reactor, wherein the TCS Absorber Column receives i) the first vent gas from the Reactor or a portion thereof and ii) a fresh portion of STC, and wherein a first exit stream comprising at least 75% of the H₂ present in the first vent gas and optionally at least 50% of the STC in the first vent gas, and second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS present in the first vent gas, both exit the TCS Absorber Column; and

c. an STC Converter in fluid communication with the TCS Absorber Column, where the STC Converter receives the first exit stream comprising at least 75% of the H₂ and optionally at least 50% of the STC from the TCS Absorber Column and provides a second vent gas comprising STC, TCS, HCl and H₂, and optionally also DCS.

[0057] In optional embodiments of this aspect, one or more of the following features may be used to describe the system of the present disclosure: an HCl-Pipeline Reactor is located between, and is in fluid communication with each of, the CVD or FBR reactor and the TCS Absorber Column; an STC/TCS Separator Column is in fluid communication with each of the STC Converter and the TCS Absorber Column, where second vent gas from the STC Converter and second exit stream from the Absorber Column are fed into the STC/TCS Separator Column; the first exit stream is in the gas phase; the second exit stream is in the liquid phase; an HCl Stripper Column is located between, and is in fluid communication with each of the TCS Absorber Column and the STC/TCS Separator Column; an STC Converter is in fluid communication with and provides the second vent gas to an HCl Absorber Column; the HCl Absorber Column is in fluid communication with and provides STC and TCS to an HCl Recovery Column; the HCl Recovery Column is in fluid communication with and provides STC and TCS to the STC/TCS Separator Column; the STC Converter comprises metal silicide catalyst. [0058] In yet another aspect, the present disclosure provides a system comprising:

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor which produces a first vent gas comprising STC, TCS, H₂ and optionally DCS, where optionally the reactor contains rod for producing polysilicon;

b. a Refrigerator/Decanter combination, wherein the combination receives the first vent gas from the Reactor or a portion thereof and generates two exit streams, a first exit stream, optionally being in a gas phase and comprising at least 75% of the H2 present in the first vent gas and optionally at least 50% of the STC in the first vent gas, and a second exit stream, optionally being in the liquid phase and comprising at least 50% of the TCS and optionally at least 50% of the DCS present in the first vent gas, both exit streams exiting the Refrigerator/Decanter combination; and

c. an STC Converter, where the STC Converter receives the first exit stream comprising at least 75% of the H₂ present in the first vent gas and optionally at least 50% of the STC present in the first vent gas, and provides a second vent gas comprising STC, TCS, HC1 and H₂, and optionally also DCS,

[0059] In one aspect, the present disclosure provides a process comprising:

a. producing a first vent gas comprising STC, TCS, HC1 and H₂ from a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor; where optionally DCS is also part of the first vent gas; the first vent gas is optionally produced in a Reactor wherein polysilicon is produced and STC, TCS, HC1 and H₂ (and optionally DCS) are by-products of the polysilicon producing reaction;

b. producing a second exit stream comprising STC and TCS but not appreciable amounts of HC1 or H₂ from the first vent gas;

c. feeding the second exit stream into an STC/TCS Separator Column; d. producing a second vent gas comprising STC, TCS, HC1 and H₂, and optionally DCS, from an STC Converter;

e. producing a third exit stream comprising STC and TCS but not appreciable amounts of HC1 or H₂ from the second vent gas;

f. feeding the third exit stream into the STC/TCS Separator Column; and g. separating STC from TCS in the STC/TCS Separator Column. [0060] In optional embodiments of this aspect, one or more of the following features may be used to describe the process of the present disclosure: the Reactor is a CVD reactor that produces polysilicon; the first vent gas is fed into a TCS Absorber Column along with fresh STC and the second exit stream exits the TCS Absorber Column; the second exit stream is fed into an HCl Stripper Column to remove HCl before being fed into the STC/TCS Separator Column; the STC Converter is operated under non-equilibrium conditions; the second vent gas is fed sequentially into an HCl Absorber Column and an HCl Recovery Column to provide the third exit stream comprising STC and TCS but not appreciable amounts of HCl or H₂; STC from the STC/TCS Separator Column is fed into a TCS Absorber Column, where the first vent gas is also fed to the TCS Absorber Column.

[0061] In a related aspect, the present disclosure provides a system comprising:

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor which produces a first vent gas comprising STC, TCS, HCl and H₂, and optionally producing DCS; the Reactor optionally producing polysilicon and receiving a feedstock comprising TCS;

b. a TCS Absorber Column in fluid communication with the Reactor, wherein the TCS Absorber Column receives i) the first vent gas or a portion or a byproduct thereof from the Reactor and separates H₂ from the first vent gas to provide a second exit stream, optionally in liquid phase, comprising STC and TCS and not containing appreciable amounts of H₂ or HCl; however, where optionally there may be located an HCl Pipeline Reactor between the Reactor and the TCS Absorber Column to remove HCl from the first vent gas;

c. an STC/TCS Separator Column in fluid communication with the TCS Absorber, where the STC/TCS Separator Column receives an exit stream comprising STC and TCS from the TCS Absorber, however where optionally there may be located an HCl Stripper Column between the TCS Absorber and the STC/TCS Separator Column in order to remove HCl from the mixture entering the STC/TCS Separator Column;

d. an STC Converter in fluid communication with the TCS Absorber Column, where the STC Converter receives a feed of H₂ from the TCS Absorber and STC, and generates a second vent gas comprising STC, TCS, HCl and H₂, and optionally also comprising DCS. e. an HCl Absorber Column in fluid communication with the STC Converter, where the HCl Absorber Column receives the second vent gas from the STC Converter, and generates a mixture comprising STC, TCS and HCl that does not contain appreciable amounts of H₂;

f. an HCl Recovery Column in fluid communication with the HCl Absorber Column, where the HCl Recovery Column receives the mixture comprising STC, TCS and HCl that does not contain appreciable amounts of H₂, and generates a third exit stream comprising STC and TCS which does not contain appreciable amounts of HCl or H₂.

[0062] In another aspect, the present invention provides a process comprising: a) feeding H₂ and TCS into a CVD or FB Reactor (Reactor) to produce polysilicon and a first vent gas comprising at least a portion of the H₂ (the first portion of H₂); and

b) feeding some or all of the first portion of H₂ and STC into an STC Converter to produce TCS and a second vent gas, the second vent gas comprising a portion of the first portion of H₂ (the second portion of H₂). Optionally, the process further comprises

c) feeding some or all of the second portion of H₂ along with TCS into the Reactor to produce polysilicon.

[0063] The details of one or more embodiments are set forth in the description below. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Other features, objects and advantages will be apparent from the description, the drawings, and the claims. In addition, the disclosures of all patents and patent applications referenced herein are incorporated by reference in their entirety.

Detailed Description

[0064] The present disclosure provides new approaches to producing polysilicon. In one aspect the present disclosure provides a process wherein the components of a Reactor vent gas, which may be either a CVD Reactor or FB Reactor vent gas, are not completely separated from one another so as to provide pure component streams. For example, the components of the Reactor vent gas are partially separated into an H₂/STC stream and a TCS/DCS stream. The H₂ from the vent gas is left in contact with STC, and that H₂/STC mixture is fed into an STC converter. A system to operate the process is also provided.

[0065] For example, the present disclosure provides a process which includes producing a first vent gas comprising STC, TCS, HC1 and H₂, and optionally also includes DCS. This first vent gas may be produced by, for example, operation of the Siemens reaction, whereby a feed including primarily TCS and H₂ is directed into a Chemical Vapor Deposition (CVD) reactor operating at high temperature, so as to deposit polysilicon inside the Reactor and generate the first vent gas that includes unreacted TCS and H₂, typically some DCS, and byproducts STC and HC1. Other methods which generate polysilicon may also create a vent gas that may be used in this process, e.g., a Fluidized Bed (FB) Reactor. Optionally, some of the first vent gas may be diverted to other parts of the plant, rather than be used in the present process. In this optional embodiment, only a portion of the first vent gas is utilized in the presently disclosed process. Accordingly, reference to the first vent gas includes the entire first vent gas or a portion thereof.

[0066] Optionally, the first vent gas leaving the Reactor may be treated so as to remove some or all of the HC1. Such HC1 removal may be accomplished by using an HC1 Pipeline Reactor which is operated as described in U.S. Patent 5,401,872. In this optional embodiment, the first vent gas is delivered to an HC1 Pipeline Reactor containing a chlorination catalyst at a temperature within the range of 30-400°C thereby effecting substitution of silicon-bonded hydrogen from a hydrosilane (for example, TCS or DCS) to form a more highly chlorinated silane (for example, STC or TCS, respectively). A chlorination catalyst is present in the HC1 Pipeline Reactor where suitable chlorination catalysts include metals such as palladium, platinum, rhodium, nickel, osmium, as well as compounds thereof, e.g., salts and oxides of the listed metals. Fresh hydrosilane may optionally be fed into the HC1 Pipeline Reactor, in addition to the first vent gas, in order to assist in consuming all or most of the HC1. Accordingly, in an optional step, the first vent gas is stripped of HC1 to provide an HC1 depleted first vent gas having less than, for example, 10% or 5% or 4% or 3% or 2% or l% by weight of HC1.

[0067] In an alternative option, HC1 is not stripped from the first vent gas, but instead is present in the first vent gas during the partial separation step. In the partial separation step, all or a majority amount, i.e., at least 60%, or at least 70%, or at least 80%, or at least 90% of the HC1 present in the first vent gas may be included in the first exit stream that also includes H₂ and STC. None, or a minority amount, i.e., less than 20%, or less than 15%, or less than 10%, or less than 5% of the HCl in the first vent gas is included in the second exit stream, i.e., the mixture that includes TCS, DCS and may also include some STC.

[0068] The components of the first vent gas or an HCl-depleted version thereof are partially separated. In one embodiment, the first vent gas or an HCl-depleted version thereof is separated into at least two different mixtures, optionally one mixture being in the gas phase and the other mixture being in the liquid phase: one mixture contains STC and H₂ and is referred to herein as a first exit stream (this mixture optionally being in the gas phase) while the other mixture contains TCS and optionally DCS and is referred to herein as a second exit stream (this mixture optionally being in the liquid phase). The formation of a first exit stream and a second exit stream may be accomplished by various methods as will be exemplified herein. The separation of the components of the first vent gas need not be perfect or complete. For example, some STC may be present in both of the first and second exit streams. However, the exit stream that contains STC and H₂ will contain at least 75% of the H₂ that is present in the first vent gas or an HCl-depleted version thereof, and in optional embodiments contains at least 80% or at least 85% or at least 90% or at least 95% of that H₂. After the partial separation, some of the STC present in the first vent gas or present in the HCl-depleted version thereof is in combination with the H2 that exits the TCS Absorber Column as the first exit stream. It is desirable for as much STC as practical to remain in contact with the H₂, because the mixture comprising H₂ and STC will, in a later step, be delivered to an STC Converter Reactor wherein the STC is converted to more useful material(s).

[0069] The partial separation will also provide a mixture, preferably a liquid mixture, that contains TCS and typically also DCS, optionally also containing relatively minor amounts of STC and perhaps very minor amounts of H₂ and HCl. This mixture is referred to herein as a second exit stream, and it may be produced in various manners as exemplified herein. After a second exit stream is produced, that stream may be further refined and/or fractionated to remove components thereof, but so long as it contains TCS and optionally DCS, it may still be referred to herein as a second exit stream. In optional embodiments, at least 50% of the TCS and optionally at least 50% of the DCS present in the vent gas or the HCl-depleted version thereof, is present together in the second exit stream after the partial separation. In various embodiments, at least 60%, or at least 70% or at least 80% or at least 90% or at least 95% of the TCS and/or DCS as present in the first vent gas or the HCl-depleted version thereof is, after the partial separation, present together in the second exit stream. In one embodiment, the partial separation achieves two mixtures, where one mixture referred to as the first exit stream and which is optionally a gas mixture, contains at least 95% of the hydrogen and at least 80% of the STC present in the first vent gas or HCl-depleted version thereof, while the other mixture referred to as the second exit stream and which is optionally a liquid mixture, contains at least 80% of each of the TCS and DCS present in the first vent gas or HCl-depleted version thereof.

[0070] The first exit stream containing H₂ and STC is fed into an STC

Converter. Optionally, fresh H₂ and/or fresh STC may be added to the first exit stream prior to its delivery into the STC Converter. Inside the STC Converter, the STC will be converted to TCS along with some DCS, but in addition byproduct HC1 will be produced. Thus, the vent gas from the STC Converter, which will be referred to herein as the second vent gas, will contain unreacted STC in the ordinary course of operation, as well as products TCS and optionally DCS, unreacted H₂ and byproduct HC1. In the ordinary course of operation, the conversion of the STC will be in the range of 20-35%, so the second vent gas will contain significant amounts of STC.

[0071] Besides a process, in a related aspect the present disclosure also provides a system that includes a Reactor which produces a vent gas comprising STC, TCS, HC1 and H₂, and optionally DCS (a first vent gas). This Reactor may be a typical CVD reactor used in the Siemens process for polysilicon manufacture, or it may be a Fluidized Bed (FB) Reactor as discussed later herein.

[0072] Optionally, the system includes an HC1 Pipeline Reactor. The HC1

Pipeline Reactor contains a metal catalyst and is operated at a temperature in the range of 30-400°C. The HC1 Pipeline Reactor consumes HC1 by transferring the chlorine thereof to a hydrosilane, preferably to a hydrochlorosilane such as TCS and/or DCS, to thereby produce more highly chlorinated silane species. Exiting the HC1 Pipeline Reactor will therefore be the first vent gas that has been largely or entirely depleted of HC1. Thus, in an optional embodiment, the HC1 Pipeline Reactor is in fluid

communication with the Reactor.

[0073] In addition, the system includes an absorber column, where the absorber column receives i) the vent gas from the Reactor or an HCl-depleted version thereof or a portion thereof and ii) a fresh portion of STC. At least two streams exit the absorber column. One stream is referred to as a first exit stream and is a mixture of primarily H₂ and STC and is optionally a gas stream, while the other stream is referred to as a second exit stream and is TCS or a mixture of TCS and DCS, which will also typically contain substantial amounts of STC, and is optionally a liquid stream. This absorber column is referred to herein as a TCS Absorber Column.

[0074] In addition, the system includes an STC Converter. The STC Converter receives the mixture comprising STC and H₂ from the TCS Absorber Column and creates a vent gas, referred to herein as the second vent gas, which comprises STC, TCS, HC1 and H₂, and also may contain some DCS.

[0075] Optionally, the system may include one or more temperature controllers and heat exchangers. For example, a temperature controller may be placed at the inlet to the STC Converter, to adjust the temperature of the first exit stream prior to its entry into the STC Converter. Also, or alternatively, a heat exchanger may be placed at the outlet of the TCS Absorber Column, where the heat exchanger will also be in contact with the second vent gas, to thereby achieve transfer of heat from the second vent gas to the first exit stream. In another optional embodiment, the second vent gas may be directed through a temperature controller after the second vent gas exits a heat exchanger. This temperature controller may act on the second vent gas so as to cool it to a lower temperature.

[0076] In a related aspect, the partial separation of the components of the first vent gas or the HCl-depleted version thereof is accomplished by use of a system including a Refrigerator/Decanter combination. In this aspect, a Reactor that produces polysilicon also produces a first vent gas that contains STC, TCS, HC1 and H₂, and optionally some DCS. This first vent gas may optionally be directed through an HC1 Pipeline Reactor to remove HC1 and produce chlorosilane(s) as described elsewhere herein, to thereby provide an HCl-depleted first vent gas. The first vent gas or an HCl- depleted version thereof is fed into a Refrigerator/Decanter combination, wherein the H₂ is separated from the other components of the feed and is an example of a first exit stream. The STC and TCS which exit the Refrigerator/Decanter combination, which is another example of a second exit stream, are fed into an STC/TCS Separator Column to provide pure streams of TCS and STC. The STC is combined with the H₂ from the Refrigerator/Decanter combination, and fed into an STC Converter. Optionally, the system may include one or more temperature controllers and heat exchangers. For example, a temperature controller may be placed at the inlet to the STC Converter, to adjust the temperature of the gas mixture comprising H₂ and STC prior to its entry into the STC Converter. Also, or alternatively, a heat exchanger may be placed at the inlet to the Refrigerator/Decanter combination, where that heat exchanger is also in combination with one or both of the outlet streams from the Refrigerator/Decanter combination. In this way, heat from the relatively hot first vent gas or HCl-depleted version thereof may be transferred to either the first exit stream or the second exit stream from the Refrigerator/Decanter combination.

[0077] In embodiments of the processes and systems disclosed herein, the components of the first vent gas or an HCl-depleted version thereof are partially, rather than completely, separated from one another by various means as exemplified herein. For example, the first vent gas or an HCl-depleted version thereof may be separated into at least two different mixtures: a first exit stream contains STC and H₂ and is typically a gas phase mixture while a second exit stream contains TCS and STC, and optionally DCS, and is typically a liquid phase mixture. The mixture that contains STC and H₂ may be directed into an STC Converter whereupon TCS is produced and present in the second vent gas. In one embodiment of the present disclosure, an HCl-depleted version of the first vent gas is not the feed to the STC Converter, and instead the feed to the STC Converter contains HC1. Such a feed may be obtained during the partial separation of the components of the first vent gas, where the mixture that contains STC and H₂ additionally contains HC1.

[0078] In various embodiments, the STC Converter that receives the mixture of

STC and H₂, optionally in admixture with HC1, is operated in a non-equilibrium mode, a low-temperature mode preferably with a catalyst, or a non-equilibrium and low temperature mode preferably with a catalyst. In one embodiment, the STC Converter yields TCS at a supra-equilibrium level, that is, at a level that exceeds the level of TCS produced when the STC Converter is operated under equilibrium conditions at the same temperature and pressure. The use of a mixture of H₂ and STC, optionally in admixture with HC1, as a feed gas for the STC Converter, in addition to operating the STC Converter in a non-equilibrium and/or low temperature mode, may together provide for supra-equilibrium levels or yields of TCS. [0079] The inclusion of HCl in the feed to the STC Converter is an aspect of the present disclosure that is contrary to current teaching/practice. Current teaching is that: (a) the reaction producing TCS from STC is: STC + H₂→ TCS + HCl, and (b) the equilibrium amount of TCS produced by this reaction is lowered if HCl is present in the feed to the reactor. However, according to the present disclosure, STC conversion may be increased compared to that obtained when the STC Converter is operated under equilibrium conditions without the presence of HCl, by an order of at least 1.5X, or at least 2X, or at least 3X. While not intending to be bound by theory, the following is suggested to explain this result.

[0080] TCS may be formed from STC in an STC Converter (4) containing metal silicide catalyst, where the metal used comprises nickel, iron, and chrome in pure or alloyed form. At least two reactions are important in the conversion chemistry. One of those two reactions is the formation of silicon-enriched silicide from STC and metal- enriched silicide, which is a relative fast reaction. The reaction proceeds according to the following chemistry shown in steps a, b and c, where Ni₂Si is used as an exemplary metal-enriched silicide, with the understanding that alternative silicides of nickel, and indeed other silicides that may or may not contain or include nickel, could be substituted for the Ni₂Si:

a. Ni₂Si + SiCl₄ → [(Ni₂Si)SiCl₂]Cl₂

b. [(Ni₂Si)SiCl₂]Cl₂ + H₂ → (Ni₂Si)SiCl₂ + 2HC1 c. (Ni₂Si)SiCl₂ + H₂ → 2NiSi + 2HC1

[0081] The reverse reaction, i.e., the decomposition reaction of silicon-enriched silicide with HCl to form metal-enriched silicide and TCS is relatively slow, and proceeds according to the following chemistry shown in steps d and e:

d. 2NiSi + 2HCl → (Ni₂Si)SiCl₂ + H₂

e. (Ni₂Si)SiCl₂ + HCl → Ni₂Si + S1HCI3

[0082] The reaction of STC to form silicide is fast, but the decomposition of the silicide so formed to TCS is slow. Furthermore, the decomposition reaction requires 3 molecules of HCl to proceed, while the reaction producing silicide from STC produces 4 molecules of HCl. According to current commercial practice and theory (see, e.g., Roewer et al. in DE 4 041 644, DE 4 108 614, US 5,716,590 and US Publication 2009/0035205), these 4 molecules of HC1 that are produced by the STC conversion process are removed from the silicide phase into a reaction gas phase containing primarily ¾ and STC (which are the reactants introduced into the STC Converter) and relatively low amounts of HC1. This is intentionally done in an effort to maximize equilibrium conversion of STC to TCS. However, the present disclosure observes that including HC1 in the feed to the STC Converter can unexpectedly and substantially increase STC conversion resulting in supra-equilibrium amounts of TCS in the converter product stream. In order to manifest this effect, it is desired to operate the STC Converter in a catalytic mode, with a limited hold-up time in the STC Converter, as explained next.

[0083] The operation of an STC Converter (4) in a catalytic mode entails converting STC to TCS and other products by contacting feed gas comprising STC, ¾ and optionally HC1 with a catalyst in a reactor, the reactor also referred to as a catalytic converter. The catalyst may be a metal catalyst, for example, shaped metal pieces with high aggregate surface area, or a fine wire mesh. The metal catalyst may comprise metal silicides, including without limitation chrome silicide, nickel silicide, and iron silicide. Optionally, the catalyst may be formed in situ, or in other words, the catalyst is formed within the reactor. In one embodiment, the reactor is charged with self- supporting metal, and at least a portion of the surface of that metal is converted to metal catalyst. In another embodiment, the reactor is charged with a fine wire mesh, and the entirety of the mesh is converted to metal catalyst. The process is run at low temperature, e.g., at a temperature of less than 700°C, for example, a temperature of from 100°C to 700°C, or from 300°C to 600°C, or from 400°C to 500°C, or about 500°C. The hold-up time of the feed gas in the reactor optionally ranges from 0.1 second to 20 seconds, or from 1 second to 10 seconds, or from 2 seconds to 5 seconds, or is about 3 seconds. The pressure within the reactor may range from 0.5 atmospheres absolute to 20 atmospheres absolute, or from 1.0 atmosphere absolute to 12

atmospheres absolute, or is about 6 atmospheres absolute. By selective control of the temperature and hold up time within the reactor, the reaction may be run under non- equilibrium conditions, allowing for increased conversion of STC to TCS relative to the conversion obtained in a non-catalyzed reaction, e.g., a reaction run in a thermal reactor in the absence of catalyst at a high temperature, typically in excess of 1,000°C. An advantage of using catalyst in an STC Converter is that when the STC Converter is operated in a non-equilibrium mode (as compared to running the STC Converter with catalyst in an equilibrium mode) relatively high conversion can be achieved. For example, it is possible to achieve a conversion at a low temperature in a non- equilibrium, catalytic STC converter that is as great as or even larger than the conversion which can be achieved in a thermal equilibrium reactor (no catalyst - i.e., in a Standard STC Converter) run at high temperature (in excess of 1,000°C). This may be due to the fact that the conversion of STC to TCS and other materials is

endothermic, which means that the temperature must be raised to 1,100C to 1,300 C to achieve an equilibrium conversion in the range of 20% to 30%. In comparison, this level of conversion may be achieved at lower temperature, e.g., 500°C to 700°C, in a catalytic STC Converter operated in a non-equilibrium manner.

[0084] In various embodiments, the level of HC1 in the STC converter feed is to be maintained at > 0.2 mole %, at > 0.5 mole %, at > 2 mole %, or at > 3 mole %, or at > 5 mole % HC1 in the feed stream comprising hydrogen and STC. In various embodiments, it may additionally be stated that the molar ratio of hydrogen to STC is selected from > 1, > 2, > 3, or > 4. In various embodiments, it may additionally be stated that the STC converter temperature is within the range 300-1100°C; or is within the range 400-900°C; or is within the range 500-700°C; or is within the range 500- 600°C. In various embodiments, it may additionally be stated that the STC converter pressure is within the range 20-400 PSIG; or within the range 40-300 PSIG; or within the range 60-200 PSIG; or within the range 80-100 PSIG. Specific embodiments of the systems and processes of the present disclosure, often in combination with optional operational units to illustrate how a manufacturing plant might be composed and operated which includes the systems and processes of the present disclosure, are provided elsewhere herein by reference to the accompanying Figures.

[0085] Thus, in one embodiment the present disclosure provides a process comprising:

i. producing a first vent gas comprising STC, TCS, HC1 and H₂ from a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor; where optionally DCS is also part of the first vent gas; the first vent gas is optionally produced in a Reactor wherein polysilicon is produced and STC, TCS, HC1 and H₂ (and optionally DCS) are by-products of the polysilicon producing reaction; ii. separating components of the first vent gas to provide at least two separate mixtures, one mixture comprising at least 50% of the STC and at least 75% of the H₂ present in the first vent gas, and the other mixture comprising at least 50% of the TCS and at least 50% of the DCS present in the first vent gas; and

iii. feeding the gas mixture comprising STC and H₂ to an STC Converter to provide a second vent gas comprising STC, TCS, HCl and H₂, optionally also containing DCS.

[0086] In another embodiment, the present disclosure provides a system comprising:

i. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor which produces a vent gas comprising STC, TCS, HCl and H₂, and optionally also produces DCS, the reactor optionally produces polysilicon and receives TCS as a feedstock;

ii. an absorber column, wherein the absorber column receives i) the first vent gas from the Reactor or a portion thereof and ii) a fresh portion of STC, and wherein one mixture (a first exit stream) comprising an amount equal to at least 50% of the STC and at least 75% of the H₂ present in the first vent gas, and another mixture (a second exit stream) comprising at least 50% of the TCS and optionally at least 50% of the DCS present in the first vent gas, both exit the absorber column; and

iii. an STC Converter, where the Converter receives the mixture comprising at least 50% of the STC and at least 75% of the H₂ present in the first vent gas and provides a vent gas comprising STC, TCS, HCl and H₂, and also optionally contains DCS.

[0087] In yet another embodiment, the present disclosure provides a system comprising:

i. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor which produces a first vent gas comprising STC, TCS, HCl and H₂, where DCS is optionally present in the first vent gas, and where optionally polysilicon is produced in the Reactor from a feedstock comprising TCS;

ii. a Refrigerator/Decanter combination, wherein the combination receives the first vent gas from the Reactor or a portion thereof and generates two mixtures, one mixture, optionally in the gas phase, comprising at least 50% of the STC and at least 75% of the H₂ present in the first vent gas (a first exit stream), and the other mixture, optionally in the liquid phase, comprising at least 50% of the TCS and at least 50% of the DCS present in the first vent gas (a second exit stream), both exit the combination; and iii. an STC Converter, where the Converter receives the mixture comprising and at least 75% of the H₂ present in the first vent gas and optionally at least 50% of the STC present in the first vent gas, and provides a second vent gas comprising STC, TCS, HCl and H₂, and also optionally contains DCS.

[0088] As mentioned previously, the present disclosure provides new approaches to producing polysilicon. In one aspect the present disclosure provides a process wherein a single STC/TCS Separator Column receives vent gas (or portions thereof) from both of a Reactor and an STC Converter, to produce pure or essentially pure streams of STC and TCS, the TCS optionally being in combination with DCS, where those pure streams are beneficially used elsewhere within the plant. A system to operate the process is also provided.

[0089] For example, the present disclosure provides a process that includes: i. producing a first vent gas comprising STC, TCS, HCl and H2 from a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor; where optionally DCS is also part of the first vent gas; the first vent gas is optionally produced in a Reactor wherein polysilicon is produced and STC, TCS, HCl and H2 (and optionally DCS) are by-products of the polysilicon producing reaction; ii. producing a mixture from the first vent gas comprising STC and TCS but not appreciable amounts of HCl or H₂ (this mixture may be referred to as a second exit stream); iii. feeding the mixture from the first vent gas into an STC/TCS Separator Column; iv. producing a second vent gas comprising STC, TCS, DCS, HCl and H₂ from an STC Converter; v. producing a mixture from the second vent gas comprising STC and TCS but not appreciable amounts of HCl or H₂ (this mixture may be referred to as a third exit stream); vi. feeding the mixture derived from the second vent gas into the STC/TCS Separator Column; and vii. separating STC from TCS in the STC/TCS Separator Column.

[0090] In regards to producing a first vent gas comprising STC, TCS, HCl and

H₂ (and optionally DCS) from the Reactor, this may be readily accomplished by practicing the well-known Siemens process for polysilicon manufacture, as one example. The Siemen's process utilizes a Chemical Vapor Deposition (CVD) reactor operated at high temperature. The CVD reactor receives a feedstock including TCS and H₂, and creates a vent gas including STC, TCS, typically DCS, HCl and H₂. Within the CVD reactor there is deposition and thus formation of polysilicon. The vent gas that leaves the CVD reactor will be referred to herein as the first vent gas. Under typical operating conditions, the Siemen's process produces DCS as a component of the vent gas, although under certain conditions DCS is not produced in appreciable amounts.

[0091] In regards to producing a mixture from the first vent gas comprising STC and TCS but not appreciable amounts of either HCl or H₂, which is referred to herein as a second exit stream, this may be accomplished in any of multiple ways. As one optional step, the HCl present in the first vent gas may be converted in an HCl Pipeline Reactor to produce chlorosilanes as discussed elsewhere herein. However, an alternative approach is to direct the entire first vent gas into a TCS Absorber Column, where an exit stream comprising HCl, H₂ and STC is created, while a different exit stream comprising STC, TCS, DCS and a small amount of HCl is also created. The exit stream comprising TCS may optionally be directed through an HCl Stripper Column to remove essentially all of the HCl. This approach creates a mixture from the first vent gas that comprises STC, TCS and DCS, which is a second exit stream. This mixture is then directed into an STC/TCS Separator Column.

[0092] In regards to producing a second vent gas comprising STC, TCS, HCl and H₂, and typically also DCS, from an STC Converter, this can be accomplished in multiple ways. A feed is introduced into an STC Converter, where that feed contains STC and H₂, and optionally contains HCl. This feed may be referred to herein as a first exit stream. The STC Converter acts on this feed to convert the STC into TCS and DCS. Typically, not all of the STC is converted into TCS and DCS and thus the vent gas from the STC Converter, referred to herein as the second vent gas, contains residual STC. HCl is a byproduct of the conversion of STC to TCS and DCS and therefore is present in the second vent gas. The STC Converter may be operated as a thermal equilibrium reactor (i.e., Standard STC Converter, (15)) or non-equilibrium, catalytic reactor (i.e., Catalytic STC Converter, (4)), as discussed elsewhere herein.

[0093] In regards to producing a mixture from the second vent gas comprising

STC and TCS but not appreciable amounts of either HCl or H₂, this may be

accomplished in any of multiple ways. For example, the second vent gas may be fed into an HCl Absorber Column to separate the HCl from the H₂, where each of the HCl and H₂ remain in combination with chlorosilane(s). The HCl-containing stream may then be fed into an HCl Recovery Column, where HCl is separated from chlorosilanes to provide the mixture from the second vent gas comprising STC and TCS but not appreciable amounts of either HCl or H₂.

[0094] These two mixtures, one from the first vent gas and the other from the second vent gas, both of which comprise STC and TCS but not appreciable amounts of either HCl or H₂, are both directed into a single STC/TCS Separator Column. In this way, a plant operating the process of the present disclosure does not need two separate vent gas recovery systems, each having its own STC/TCS Separator Column. After entering the STC/TCS Separator Column, the two mixtures are combined and then are separated into their component parts, generating an exit stream containing largely if not entirely STC and a separate exit stream containing largely if not entirely TCS.

[0095] As used herein, not appreciable amounts of either HCl or H₂ means that the subject gas stream contains less than 5Mol of either of HCl and H₂, and optionally contains even less of those components, for example, less than 4 mol or less than 3 mol or less than 2 mol or less than 1 mol of HCl and less than 4 mol or less than 3 mol or less than 2 mol or less than 1 mol of H₂.

[0096] Thus, in one embodiment the present disclosure provides a process comprising:

i. producing a first vent gas comprising STC, TCS, HCl and H₂ from a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor; where optionally DCS is also part of the first vent gas; the first vent gas is optionally produced in a Reactor wherein polysilicon is produced and STC, TCS, HCl and H₂ (and optionally DCS) are by-products of the polysilicon producing reaction; ii. producing a mixture (a second exit stream) from the first vent gas comprising STC and TCS but not appreciable amounts of HCl or H₂,

iii. feeding the mixture from the first vent gas into an STC/TCS Separator Column; iv. producing a second vent gas comprising STC, TCS, HCl and H₂, and also optionally containing DCS, from an STC Converter;

v. producing a mixture from the second vent gas (a third exit stream) comprising STC and TCS but not appreciable amounts of HCl or H₂,

vi. feeding the mixture from the second vent gas into the STC/TCS Separator Column;

vii. separating STC from TCS in the STC/TCS Separator Column.

[0097] In another embodiment, the present disclosure provides a system comprising: i. a Reactor which produces a first vent gas comprising STC, TCS, HCl and H₂ and optionally comprising DCS; where the Reactor is optionally selected from a CVD Reactor and a FB Reactor; where the Reactor optionally produces polysilicon from a feedstock comprising TCS:

ii. a TCS Absorber Column in fluid communication with the Reactor, where the TCS Absorber Column receives the first vent gas or a portion or byproduct thereof from the Reactor and separates H₂ so as to provide a mixture comprising STC and TCS and optionally not containing appreciable amounts of H₂ or HCl (a second exit stream), the TCS Absorber optionally in fluid communication with an HCl Stripper Column to remove residual HCl from the second exit stream;

iii. an STC/TCS Separator Column in fluid communication with the TCS Absorber Column (3) or the HCl Stripper Column, where the STC/TCS Separator Column receives the mixture from the TCS Absorber Column comprising STC and TCS, where optionally the mixture from the TCS Absorber Column passes through an HCl Stripper Column prior to entering the STC/TCS Separator Column, where HCl is removed from the mixture during passage through the HCl Stripper Column;

iv. an STC Converter in fluid communication with the TCS Absorber Column, where the STC Converter receives a feed of H₂ from the TCS Absorber and STC, and generates a second vent gas comprising STC, TCS, HCl and H₂, and also optionally contains DCS;

v. an HCl Absorber Column in fluid communication with the STC Converter, where the HCl Absorber Column receives the second vent gas from the STC Converter, and generates a mixture comprising STC, TCS and HCl that does not contain appreciable amounts of H₂;

vi. an HCl Recovery Column in fluid communication with the HCl Absorber Column, where the HCl Recovery Column receives the mixture comprising STC, TCS and HCl that does not contain appreciable amounts of H₂, and generates a mixture comprising STC and TCS which does not contain appreciable amounts of HCl or H₂. vii. the STC/TCS Separator Column also being in fluid communication with the HCl Recovery Column, where the mixture comprising STC and TCS which does not contain appreciable amounts of HCl or H₂ as generated by the HCl Recovery Column is directed into the STC/TCS Separator Column. [0098] In the process or system, one or more of the following features may be used to describe the present disclosure: the Reactor is a CVD reactor that produces polysilicon; the Reactor is a Fluidized Bed Reactor; the first vent gas is fed into a TCS Absorber Column along with fresh STC, and a mixture comprising STC, TCS and HCl exits the TCS Absorber Column; the mixture comprising STC, TCS and HCl that exits the TCS Absorber Column is fed into an HCl Stripper Column to remove HCl before being fed into the STC/TCS Separator Column; the STC Converter is operated under non-equilibrium conditions; the second vent gas is fed sequentially into an HCl Absorber Column and an HCl Recovery Column to provide a mixture, optionally a liquid mixture, comprising STC and TCS but not appreciable amounts of HCl or H₂; STC from the STC/TCS Separator Column is fed into a TCS Absorber Column and optionally to the STC Converter, where the first vent gas is also fed to the TCS Absorber Column.

[0099] As mentioned previously, the present disclosure provides new approaches to producing polysilicon. In one aspect the present disclosure provides a process wherein a single portion of hydrogen is delivered to both of a CVD reactor (or FBR) and an STC Converter. A system to operate the process is also provided.

[00100] A typical commercial plant that produces polysilicon utilizes a CVD Reactor or a FB Reactor, collectively a Reactor, to convert TCS into polysilicon and byproduct STC, and an STC Converter to consume the byproduct STC and generate TCS. The TCS generated by the STC Converter may, and desirably is, then used as a feedstock for the Reactor. Hydrogen is used as a component of the feed that goes into both the Reactor and the STC Converter. However, under ordinary operating conditions, each of the Reactor and the STC Converter is associated with its own, independent, vent gas recovery system. Accordingly, the hydrogen that is used as a carrier/reactant in the STC Converter optimally does not come into contact with the hydrogen that is used as a carrier/reactant in the Reactor. The present disclosure does away with this approach to operating a polysilicon production facility, by providing a single stream of hydrogen which is used in both of the Reactor and the STC Converter.

[00101] Thus, in one aspect, the present disclosure provides a process for producing polysilicon, where that process comprises:

i. feeding H₂ and TCS into a first Reactor selected from a Chemical Vapor Deposition Reactor and a Fluidized Bed Reactor to produce polysilicon and a first vent gas comprising at least a portion of the H₂ (the first portion of H₂); ii. feeding some or all of the first portion of H₂ and STC into an STC Converter to produce TCS and a second vent gas, the second vent gas comprising a portion of the first portion of H₂ (the second portion of H₂); and optionally

iii. feeding some or all of the second portion of H₂ along with TCS into a second Reactor selected from a Chemical Vapor Deposition Reactor and a Fluidized Bed Reactor to produce polysilicon. The first and second Reactor may, and preferably are, the same CVD reactor. In other words, there is a portion of the H₂ feedstock that enters the first CVD reactor, where that portion exits unchanged from the first CVD reactor and enters the STC Converter, and furthermore where that portion of H₂ exits unchanged - less amounts consumed in the conversion of STC to TCS - from the STC Converter and is directed into another (or the original) CVD reactor.

[00102] The present disclosure provides a process for producing polysilicon, where that process includes feeding H₂ into a Reactor selected from a Chemical Vapor Deposition Reactor and a Fluidized Bed Reactor along with TCS to produce polysilicon and a first vent gas comprising at least a portion of the H₂ from the feed. Noteworthy in this regards is that a process for producing polysilicon from TCS proceeds according to the following formula:

4HSiCl₃→ Si + 3SiCl₄ + 2H₂

Accordingly, polysilicon production is a net producer of hydrogen. The process of the present disclosure introduces hydrogen along with TCS into a CVD reactor so that the first vent gas will include all or most of the feedstock hydrogen, as well as additional hydrogen that was generated from TCS during the formation of polysilicon. The vent gas hydrogen will therefore comprise a portion that was generated from TCS decomposition and a portion (the first portion) that was originally introduced into the CVD reactor.

[00103] In another step, the process of the present disclosure feeds some or all of the first vent gas, including at least some of the hydrogen which was part of the feedstock to the Reactor, into an STC Converter to produce TCS and a second vent gas. Noteworthy in this regard is that a process for converting STC to TCS proceeds according to the following formula:

STC + H₂→ TCS + HC1 (plus other by-products) Accordingly, STC conversion to TCS is a net consumer of H₂. However, when an excess amount of H₂ is fed into the STC Converter, some of that H₂ will be present in the vent gas (the second vent gas) that exits the STC Converter. The process of the present disclosure introduces excess H₂ along with STC into an STC Converter and produces a vent gas, referred to herein as the second vent gas, which contains H₂. The process of the present disclosure introduces excess H₂ into the STC Converter, so that the second vent gas will include a portion of (i.e., some of) the feedstock hydrogen that was originally introduced into the CVD reactor.

[00104] In summary, according to one embodiment of the process of the present disclosure, a portion of the H₂ which was introduced into the first Reactor is recovered in a first vent gas (the first portion), and at least some of that first portion is introduced into an STC Converter and travels unchanged through the STC Converter and is collected in the exiting second vent gas (the second portion of H₂). Of course, another portion of the hydrogen that enters the STC Converter reacts with STC so as to form TCS, however, not all of the hydrogen entering the STC Converter will react with STC, and that non-reactive hydrogen is the second portion of H₂. Optionally, some or all of the second portion of H₂ may be included as part of the feedstock introduced to a second Reactor, where the second Reactor may be the same unit as the first Reactor. Optionally, some or all of this second portion of H₂, which travels through the second Reactor, may be recovered in a first vent gas from the second Reactor, and may, in turn, be fed into an STC Converter and then into a third Reactor (1) (which may be the same reactor as the first and second Reactor) to continue the loop which may proceed one, two, three, four, five or more cycles.

[00105] A process of the present disclosure may therefore be described as a process comprising (a) feeding H₂ into a Reactor selected from a Chemical Vapor Deposition Reactor and a Fluidized Bed Reactor and recovering there from some or all of the feedstock H₂ (the first H₂ portion); (b) feeding some or all of the first H₂ portion into an STC Converter, and recovering there from a fraction of first H₂ portion (the second H₂ portion); and optionally (c) feeding some or all of the second H₂ portion into a Reactor selected from a Chemical Vapor Deposition Reactor and a Fluidized Bed Reactor and further optionally recovering there from some or all of the second H₂ portion (the third H₂ portion); and still further optionally; (d) feeding some or all of the third H₂ portion into an STC converter, and further optionally recovering there from a fraction of third H₂ portion (the fourth H₂ portion). [00106] Specific embodiments of the systems and processes of the present disclosure, often in combination with optional operational units to illustrate how a manufacturing plant might be composed and operated which includes the systems and processes of the present disclosure, are provided in the accompanying Figures. The systems described herein will include units, each of which will accept one or more streams, also referred to as feedstocks, and will act upon the feedstock(s) to achieve a chemical change or component separation, and will release one or more product(s) that are constituently different from the feedstock(s). Various abbreviations and conventions are used herein, where the meanings of those abbreviations and conventions are as follows: chlorosilane is used to refer to one, or more than one, in other words a mixture of, of DCS, TCS and STC; DCS stands for dichlorosilane; HC1 stands for hydrochloric acid; H₂ is used to refer to hydrogen gas; STC stands for tetrachlorosilane; TCS stands for trichlorosilane.

Figures

[00107] As mentioned previously, the present disclosure provides systems and processes for producing polysilicon that overcome disadvantages of the current practices. Current industrial practice employs two costly, duplicate vent gas treatment systems, each with its own vent gas cooling, liquid decantation, HC1 absorption, gas and liquid refrigeration, HC1 recovery, STC and TCS separation, TCS recycle system, and hydrogen gas recompression and recycle systems. The first of these two duplicate systems is used to treat vent gas leaving the CVD reactor(s), and produces separate hydrogen, TCS, and STC streams. The second duplicate system mixes STC separated in the first system with a second hydrogen gas source, and converts the admixture to TCS in an STC Converter. The present disclosure provides for a single vent gas treatment system which can treat the vent gas from both i) a CVD or FB reactor and ii) an STC Converter operated in either conventional or catalytic mode.

[00108] At its core, and as shown in the accompanying drawings, the system and process includes an HC1 Absorber Column (5), an HC1 Recovery Column (6), and a STC/TCS Separator Column (7). In addition, the system and process includes i) a Reactor (1) that both produces polysilicon and creates an off gas which is treated by the disclosed process and operational units, and ii) an STC Converter (4 or 15) that receives STC and forms an off-gas comprising TCS and other components. These features are shown in Figs. 1-11.

[00109] Also shown in Figs. 1-11 are various optional operational units. For example, Heat Exchangers 21, 22 and 23 are shown in the various drawings, where each of these Heat Exchangers is an optional operational unit, and may be omitted. The presence of a Heat Exchanger generally allows the process to be run more economically since the Heat Exchanger permits unwanted heat present in one fluid to be transferred to a cooler fluid that is desirably at a higher temperature. The present disclosure has recognized locations where Heat Exchanger(s) are desirably placed, and these are shown in the attached drawings.

[00110] Fig. 1 shows the presence of an STC Vaporizer (25) which receives the STC stream that exits the STC/TCS Separator Column (7). This STC Vaporizer (25) is an optional feature of the system illustrated in Fig. 1. Likewise, an STC Vaporizer (25) may optionally be added to any of the systems of Figs. 2-11, at a location that receives the STC stream that exits the STC/TCS Separator Column (7), in analogy to the location shown in Fig. 1.

[00111] In Figs. 1-11, one or more of the HC1 Recovery Column (6) and STC/TCS Separator Column (7) is shown to produce an effluent that is not further treated by any explicitly illustrated operational unit. For example, in Fig. 1 , the HC1 Recovery Column (6) produces an effluent 6A and the STC/TCS Separator Column (7) produces an effluent 7A. In one embodiment of the present disclosure, the effluent 6A (and equivalent effluent 6C in Fig. 2, effluent 6E in Fig. 3, effluent 6G in Fig. 4, effluent 61 in Figs. 5-8, effluent 6K in Fig. 9, effluent 6M in Fig. 10, and effluent 60 in Fig. 11) may be directed into a Fluidized Bed (FB) Reactor wherein a Direct

Chlorination (DC) reaction takes place. In direct chlorination, hydrogen chloride (HC1) is reacted with metallurgic silicon (MGSi) to produce trichlorosilane (TCS) and hydrogen (¾) according to the chemical reaction 3 HC1 + 1 MGSi→ 1 TCS + 1 ¾. Also optionally, as explicitly illustrated in Fig. 11 but as optionally present in each of Figs. 1-10 in the analogous location, the HC1 effluent from the HC1 Recovery Column (6) may be passed through an HC1 Liquefaction Unit (20) which separates HC1 as stream 20A from hydrogen as stream 20B, and then further optionally, the HC1 stream 20A may be directed into a FBR for DC. As another example, in Fig. 1, the STC/TCS Separator Column (7) produces an effluent 7A. In one embodiment of the present disclosure, the effluent 7A, (and equivalent effluent 7A in Fig. 2, effluent 7G in Fig. 5, effluent 7M in Fig. 9, effluent 70 in Fig. 10, and effluent 7Q in Fig. 11) which contains TCS and optionally DCS, may be efficiently utilized by directing it into a Reactor (1) where the TCS and, if present, the DCS, may function as starting materials for the production of polysilicon. In Fig. 10, another optional operational unit is shown for treating the effluent from the STC/TCS Separator Column (7), namely a Distillation Unit (19). This Distillation Unit (19) may be used to separate methyl chlorosilane as stream 19B away from the TCS and DCS as stream 19 A, as this mixture is originally present in the stream 70. This optional Distillation Unit (19) may be included in the system of any of Figs. 2, 5, 9 and 11, in a location analogous to that shown explicitly in Fig. 10. The purified TCS/DCS from the Distillation Unit (19) may optionally be directed into the Reactor (1) in order to convert TCS and DCS into polysilicon.

[00112] Another optional operational unit shown in Figs. 1-11 is the H₂ Recycle Compressor (16). As mentioned previously, a FB (Fluidized Bed) or CVD (Chemical Vapor Deposition) reactor for the conversion of chlorosilanes to polysilicon has hydrogen gas as a feedstock as well as an effluent product. An H₂ Recycle Compressor may be used to increase the pressure of this effluent hydrogen as it is emitted from the HCl Absorber Column (5) or the STC Absorber Column (12), to overcome the pressure drop of required auxiliary equipment so that the effluent hydrogen can be recycled and returned to the feed of the CVD reactor or FBR. However, the effluent from the HCl Absorber Column (5) and STC Absorber Column (12) may be used in alternative manners, and accordingly need not be passed through an H₂ Recycle Compressor (16).

[00113] In Fig. 3, the effluent 9B is produced by the TCS/DCS Separator Column (9), and primarily comprises TCS (the effluent 9 A primarily comprises DCS). The effluent 9B may be directed into the HCl Absorber Column (5) as shown in Fig. 3, however alternatively, or additionally, some or all of the effluent 9B may be directed into a polysilicon production reactor where it is converted into polysilicon. This option is encompassed by the arrow 9B leading from TCS/DCS Separator Column (9).

Similarly, the effluent 9D in Fig. 4, 9F in Fig. 6, and 9H in Figs. 7 and 8, may optionally be directed to a polysilicon manufacturing Reactor (1), although this option is not explicitly illustrated in the Figures.

[00114] The following described Figures illustrate aspects of the invention wherein a collection of operational units, each unit being in fluid communication with at least one other unit, provides in whole or in part a system or chemical manufacturing plant. Two operational units are in fluid communication with one another if there is conduit between the named units such that fluid my flow from one unit to the other unit. As used herein, the term "fluid communication with" includes both direct and indirect fluid communication. For example, in Fig. 1, the Reactor (1) is in direct fluid communication with the HCl Pipeline Reactor (2), and is in indirect fluid

communication with each of the TCS Absorber Column (3), the STC Converter (4), the HCl Absorber Column (5), the HCl Recovery Column (6) and the STC/TCS Separator Column (7). As another example, the STC/TCS Separator Column (7) is in direct fluid communication with each of the HCl Recovery Column (6), the TCS Absorber Column (3), the HCl Absorber Column (5), and the STC Converter (4), while being in indirect fluid communication with each of the Reactor (1), and the HCl Pipeline Reactor (3). As another convention, a downstream operational unit receives fluid from an upstream operational unit. The collection of operational units in fluid communication may provide a plant for manufacturing polysilicon. In one embodiment, the system comprises:

a) A reactor that receives a feedstock comprising TCS and creates an exit stream comprising STC and HCl. Such a reactor may be a Chemical Vapor Deposition (CVD) reactor. Such a reactor may produce polysilicon. Such a reactor may be a reactor that achieves the well-known Siemens reaction for producing polysilicon.

b) An HCl treatment system. In one embodiment, the HCl treatment system consumes HCl that is generated by the reactor. For example, the HCl treatment system may provide reaction conditions whereby HCl reacts with one or more components also present in the HCl treatment system, so that some or all, e.g., at least 95%, or at least 90% of the HCl in the reactor effluent is consumed, i.e., converted into a chemical entity other than HCl. One such HCl treatment system is referred to herein as an HCl Pipeline Reactor (2). Other possible HCl treatment systems are a TCS Absorber Column (3), an HCl Stripper Column, and a combination of a TCS Absorber Column (3) and an HCl Stripper Column. Each of these HCl treatment systems may be used to remove HCl from chlorosilanes from the Chemical Vapor Deposition reactor, e.g., the treatment system may chemically consume the HCl, or the treatment system may physically separate the HCl from the other components, e.g., chlorosilanes, generated in the reactor, e.g., the Chemical Vapor Deposition reactor. c) An STC Converter to convert STC to a mixture of chlorosilanes. The STC Converter may be operated at low temperature, non-equilibrium conditions where a (non- carbon) catalyst is present in the Converter ("Catalytic STC Converter" (4)). Because a reactor of this type employs no carbon or graphite, carbon contamination is avoided. Alternatively, the STC Converter may be operated at high temperature in the presence of graphite rods (15).

d) Optionally present is an STC/TCS Separator Column (7) to separate STC from TCS. In one aspect, this STC/TCS Separator is in fluid communication with, i.e., receives a mixture of STC and TCS from both the first vent gas and the second vent gas. e) Optionally, an HC1 Absorber Column (5) to separate hydrogen from chlorosilanes and HC1.

f) Optionally an HC1 Recovery Column (6) to separate HC1 from chlorosilanes.

[00115] The accompanying Figures illustrate how the above-mentioned operational units may be combined to form a system, or manufacturing plant, for polysilicon production. The accompanying Figures utilize numbers to refer to the various operational units, where the concordance between the numbers and the name given to each operational unit as used herein is provided in a foregoing Table.

[00116] In the Drawings, the convention is used herein that each stream exiting an operating unit is provided with a number + letter combination. The number indicates the operating unit from which the stream directly exits. For example, streams exiting the CVD reactor or a Fluidized Bed (FB) Reactor where the Siemens process is performed are 1, streams exiting the HC1 pipeline reactor are 2, streams exiting the TCS Absorber Column are 3, streams exiting the Catalytic STC Converter are 4 or 15 depending on whether the STC Converter is run catalytically or non-catalytically, streams exiting the HC1 Absorber Column are 5, streams exiting the HC1 Recovery Column are 6, streams exiting the STC/TCS Separator Column are 7, streams exiting the HC1 Stripper Column are 8, streams exiting the TCS/DCS Separator Column are 9, streams exiting the Silica Gel Bed are 10, streams exiting the Commutation Reactor are 11, streams exiting the STC Absorber Column are 12, streams exiting the STC

Converter Off-gas Scrubber Column are 13, streams exiting the HC1 Stripper Column which is in fluid communication with the STC Converter Off-gas Scrubber Column are 14, streams exiting the thermal (non-catalytic) STC Converter are 15, streams exiting the Hydrogen Recycle Compressor are 16, streams exiting the Refrigerator/Decanter are 17, streams exiting the Carbon Absorption Bed are 18, streams exiting the Distillation Column are 19, and streams exiting the HC1 Liquefaction Unit are 20. A letter is used after each of these numbers, in order to distinguish two streams that exit the same reactor but have different chemical compositions or have a different history, or in some way differ from one another. Temperature adjustment operating units may be included at any point throughout the Figures, where by convention streams exiting a temperature adjustment operating unit are not given a unique number or letter since only the temperature, and not the chemical composition, of such a stream is affected by exposure to the temperature adjustment operating unit.

[00117] Fig. 1 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the Siemens reaction may take place. In the CVD reactor, a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, and HC1, in addition to unreacted H₂ and typically also including DCS. Exit stream 1A leaving Reactor (1) is delivered into an HC1 Pipeline Reactor (2), where HC1 is converted to TCS and STC by reaction with DCS (if present) and TCS, respectively. Exit stream 2 A from the HC1 Pipeline Reactor (2) is scrubbed with STC upon delivery into a TCS Absorber Column (3). STC reflux to the TCS Absorber Column (3) removes DCS and TCS, present in the exit stream 2A, from the hydrogen stream 3A exiting the top of the TCS Absorber Column (3). This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3A exiting the top of the STC Absorber Column (12), now saturated with STC and containing only small amounts of residual DCS and TCS, is next sent to the STC Converter (4 or 15, although 4 is shown in Figure 1), where a portion of the STC in said stream is reacted with hydrogen to produce components comprising TCS and HC1. This unit may be a standard type STC converter, employing very hot graphite heating rods, or a special catalytic non-equilibrium converter of the inventor's design (see WO 2013/074425), which is carbon-free. Feed to the STC Converter may be augmented with a portion of recycle STC from stream 7B, which portion may be vaporized by use of an STC Vaporizer (25) before or after mixing with stream 3A. Although STC Vaporizer (25) is explicitly shown only in Figure 1, and is an optional feature of the system illustrated in Figure 1, the STC Vaporizer (25) may optionally be included in any of the systems illustrated in Figures 2- 11 , to assure that the portion of the STC stream leaving the STC/TCS Separator Column (7) and directed to the STC Converter is entirely in the gaseous state. The gas stream 4A exiting the STC converter is heat exchanged with stream 3A, optionally mixed with a portion of stream 7B, to the STC converter. The cooled, but still gaseous, STC Converter product stream 4A is sent to an HCl Absorber Column (5), where HCl is absorbed into chlorosilane reflux. The chlorosilane reflux stream 7 A comprises a mixture of TCS and DCS. Hydrogen exiting the top of the HCl Absorber Column (5), now saturated with equilibrium amounts of TCS and DCS, is identified in Fig. 1 as exit stream 5A. Hydrogen stream 5A may be recycled to the Reactor (1). Optionally, stream 5A may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5B exiting the bottom of the HCl Absorber Column (5) is a mixture comprised of HCl, TCS, DCS, and STC. This stream 5B is sent to an HCl Recovery Column (6) where HCl is removed overhead in exit stream 6A, and STC, TCS, and DCS are removed in the bottoms exit stream 6B. The HCl stream 6 A may be utilized as a feedstock in a direct chlorination fluidized bed reactor. The STC, DCS, and TCS in the HCl Recovery Column (6) bottoms stream 6B is directed to an STC/TCS Separator Column (7), where TCS and DCS are separated into overhead exit stream 7 A, and STC is removed in the bottoms exit stream 7B. A portion of the overhead stream 7 A from the STC/TCS Separator Column (7) is optionally recycled to the Reactor (1). The remainder is used as the reflux on the HCl Absorber Column (5). Returning to the TCS Absorber Column (3), in addition to overhead stream 3A, there is formed a bottoms stream 3B comprising STC, TCS and DCS. This stream 3B is delivered to the STC/TCS Separator Column (7) mentioned previously. Because the HCl Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 7A with the outgoing cold bottoms stream 5B may be optimally employed. Alternately (not shown in Figure 1), cold stream 5B may be heat interchanged with HCl Absorber Column (5) feed stream 4A. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 1, a heat exchanger (21) may be positioned upstream of the STC

Converter (4), with the optional placement of an intermediate Heater (24).

[00118] Thus, in one aspect the present disclosure provides a system and an associated process comprising, as illustrated in Fig. 1 :

a) a Reactor (1) selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor in fluid communication with and providing an exit stream to an HCl Pipeline Reactor (2);

b) the HCl Pipeline Reactor (2) in fluid communication with and providing an exit stream to a TCS Absorber Column (3);

c) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to both of an STC Converter and an STC/TCS Separator Column (7); d) the STC Converter in fluid communication with and providing an exit stream to the HCl Absorber Column (5);

e) the HCl Absorber Column (5) in fluid communication with and providing an exit stream to the HCl Recovery Column (6);

f) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7); and

g) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to both of the TCS Absorber Column (3) and the STC Converter.

[00119] Fig. 2 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the CVD reactor, a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HCl, in addition to unreacted H₂. Exit stream 1A leaving a Siemens CVD reactor is scrubbed with STC upon delivery into a TCS Absorber Column (3). STC reflux stream 7B to the TCS Absorber Column (3) removes DCS and TCS, present in the exit stream 1A, and creates hydrogen stream 3C exiting the top of the TCS Absorber Column (3). This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3C exiting the top of the TCS Absorber Column (3), now saturated with STC and containing HCl, is next sent to the STC Converter (4 or 15, although Figure 2 shows STC Converter (4)), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HC1. This unit may be a standard type STC Converter (15), employing very hot graphite heating rods, or a special catalytic non-equilibrium STC Converter (4) of the inventor's design, which is carbon- free (see WO 2013/074425). Feed to the STC Converter may be augmented with a portion of recycle STC from gas stream 7B, which portion may be in vaporized form, which is assured by the presence of an STC Vaporizer (25) located between the STC/TCS Separator Column (7) and the STC Converter (4 or 15). The gas stream 4B exiting the STC Converter may be heat exchanged with stream 3C, optionally in combination with a portion of stream 7B, to the STC converter, as shown in Fig. 2. The cooled, but still gaseous, STC Converter product stream 4B is sent to an HC1 Absorber Column (5), where HC1 is absorbed into chlorosilane reflux. The chlorosilane reflux, stream 7A, is comprised of a mixture of TCS and DCS. Hydrogen exiting the top of the HC1 Absorber Column (5), now saturated with equilibrium amounts of TCS and DCS, is identified in Fig. 2 as exit stream 5C. Hydrogen stream 5C may be recycled to the Reactor (1). Optionally, stream 5C may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5D exiting the bottom of the HC1 Absorber Column (5) is a mixture comprised of HC1, TCS, DCS, and STC. This stream 5D is sent to an HC1 Recovery Column (6) where HC1 is removed overhead in exit stream 6C, and STC, TCS, and DCS are removed in the bottoms exit stream 6D. The stream 6C may be directed to a fluidized bed reactor where it serves as a feedstock for the direct chlorination reaction. The STC, DCS, and TCS in the HC1 Recovery Column (6) bottoms stream 6D is directed to an STC/TCS Separator Column (7), where TCS and DCS are separated into overhead exit stream 7 A, and STC is removed in the bottoms exit stream 7B. A portion of the overhead stream 7A from the STC/TCS Separator Column (7) is optionally recycled to the Reactors (1). The remainder is used as the reflux on the HC1 Absorber Column (5). Returning to the TCS Absorber Column (3), in addition to overhead stream 3C, there is formed a bottoms stream 3D comprising STC, TCS, DCS and HC1. This stream 3D is delivered to an HC1 Stripper Column, where HC1 is obtained in a purified form in an overhead exit stream 8A, and a mixture of STC, TCS and DCS is obtained in a purified form in a bottoms exit stream 8B. The stream 8 A containing HC1 is sent to the TCS Absorber Column (3). The chlorosilane stream 8B is delivered to the STC/TCS Separator Column (7) discussed above, from which an upper exit stream 7A comprising TCS and DCS is formed, along with a bottoms exit stream 7B comprising STC.

Because the HC1 Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 7A with the outgoing bottoms stream 5D may be optimally employed. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 2, a heat exchanger (21) may be positioned upstream of the STC Converter (4), with the optional placement of an intermediate Heater (24).

[00120] Thus, in one aspect, the present disclosure provides a system and an associated process comprising, as illustrated in Fig. 2:

a) a Reactor (1) selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor in fluid communication with and providing an exit stream to a TCS Absorber Column (3);

b) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to both of an STC Converter (4 or 15) and an HC1 Stripper Column; c) the STC Converter (4 or 15) in fluid communication with and providing an exit stream to the HC1 Absorber Column (5);

d) the HC1 Absorber Column (5) in fluid communication with and providing an exit stream to the HC1 Recovery Column (6);

e) the HC1 Recovery Column (6) in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7);

f) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to both of the TCS Absorber Column (3) and the STC Converter (4 or 15); and

g) the HC1 Stripper Column in fluid communication with and providing an exit stream to the TCS Absorber Column (3) and to the STC/TCS Separator Column (7).

[00121] Fig. 3 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the CVD reactor, a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HCl, in addition to unreacted ¾. Exit stream 1A leaving a Siemens CVD reactor is directed to a TCS Absorber Column (3), where it is scrubbed with STC present in stream 7D. STC reflux to the TCS Absorber Column (3) removes DCS and TCS, present in the exit stream 1A, from the hydrogen stream 3C exiting the top of the column. This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3C exiting the top of the TCS Absorber Column (3), now saturated with STC and containing HCl, is next sent to the STC Converter (4 or 15, although (4) is shown in Figure 3), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HCl. This unit may be a standard type STC converter (15), employing very hot graphite heating rods, or a special catalytic non- equilibrium STC Converter ((4), see WO 2013/074425) of the inventor's design, which is carbon- free. Feed to the STC Converter may be augmented with a portion of recycle STC from stream 7D, which portion may be in vaporized form. The gas stream 4B exiting the STC converter (4 or 15) is heat exchanged with feed 3C entering the STC converter, feed 3C optionally being in combination with a portion of stream 7D. The cooled, but still gaseous, STC converter product stream 4B is sent to the HCl Absorber Column (5), where HCl is absorbed into chlorosilane reflux, stream 9B. The chlorosilane reflux stream 9B comprises primarily TCS as obtained from a TCS/DCS Separator Column (9). Hydrogen exiting the top of the HCl Absorber Column (5), now saturated with equilibrium amounts of TCS, and identified in Fig. 3 as exit stream 5E, may be delivered to the Reactor (1). Optionally, stream 5E may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5F exiting the bottom of the HCl Absorber Column (5) is a mixture comprised of HCl, TCS, DCS, and STC. This stream 5F is sent to an HCl Recovery Column (6) where HCl is removed overhead in exit stream 6E, and STC, TCS, and DCS are removed in the bottoms exit stream 6F. The STC, DCS, and TCS in the HCl Recovery Column (6) bottoms stream 6F are sent to the STC/TCS Separator Column (7), where TCS and DCS are separated overhead in exit stream 7C, and STC is isolated in the bottoms exit stream 7D. The overhead stream 7C from the STC/TCS Separator Column (7) is directed into a TCS/DCS Separator Column (9) to provide exit stream 9 A comprising primarily DCS and exit stream 9B comprising primarily TCS. The exit stream 9B is used, in part, to provide TCS reflux to the HC1 Absorber Column (5), however exit stream 9B can also be sent directly to a CVD reactor. The exit stream 9A, enriched in DCS, is sent to a Silica Gel Bed (10) whereupon boron contaminants in the DCS may be absorbed into the silica, and purified DCS stream 10A exits the Silica Gel Bed (10). The exit stream 10A comprising largely DCS is directed into a

Commutation Reactor (11), where it is combined with a portion of exit stream 7D from the STC/TCS Separator Column (7) comprising largely STC. Optionally (not shown), a portion of the purified DCS in stream 10A may be inventoried in a tank for customized recycle to the CVD reactor. Within the Commutation Reactor (11), a product stream 11A is formed comprising largely TCS, but containing residual DCS and STC. This product stream 11C is directed into the STC/TCS Separator Column (7). Returning to the TCS Absorber Column (3), in addition to overhead stream 3C, there is formed a bottoms stream 3D comprising STC, TCS, DCS and HC1. This stream 3D is delivered to an HC1 Stripper Column, where HC1 is obtained in a purified form in an overhead exit stream 8A, and a mixture of STC, TCS and DCS is obtained in a purified form in a bottoms exit stream 8B. Because the HC1 Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 9B with the outgoing bottoms stream 5F may be optimally employed. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. Relative to the system and process illustrated in Fig. 2, the system and process illustrated in Fig. 3 provides additional unit operations to separate DCS from TCS, to remove boron species and particularly BCb from DCS, and to convert DCS to TCS in a Commutation Reactor (11). Similar to Figs. 1 and 2, it is noted that the foregoing description of Fig. 3 does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 3, a heat exchanger (21) may be positioned upstream of the STC Converter (4 or 15), with the optional placement of an intermediate Heater (24).

[00122] Thus, in one aspect the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 3: a) a Reactor (1) selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor in fluid communication with and providing an exit stream to a TCS Absorber Column (3);

b) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to both of an STC Converter (4 or 15) and an HCl Stripper Column; c) the STC Converter (4 or 15) in fluid communication with and providing an exit stream to the HCl Absorber Column (5);

d) the HCl Absorber Column (5) in fluid communication with and providing an exit stream to the HCl Recovery Column (6);

e) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7);

f) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to each of the TCS Absorber Column (3), the STC Converter (4 or 15), and a TCS/DCS Separator Column (9) and a Commutation Reactor (11);

g) the TCS/DCS Separator Column (9) in fluid communication with and providing an exit stream to both of the HCl Absorber Column (5) and a Silica Gel Bed (10);

h) the Silica Gel Bed (10) in fluid communication with and providing an exit stream to a Commutation Reactor (11);

i) the Commutation Reactor (11) in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7);

j) the HCl Stripper Column in fluid communication with and providing an exit stream to the TCS Absorber Column (3) and to the STC/TCS Separator Column (7).

[00123] Fig. 4 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the CVD reactor, a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HCl, in addition to unreacted ¾. Exit stream 1A leaving a Siemens CVD reactor is scrubbed with STC upon delivery into a TCS Absorber Column (3). STC reflux stream 7F delivered to the TCS Absorber Column (3) removes DCS and TCS, present in the exit stream 1A, from the hydrogen stream 3C exiting the top of the column. This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3C exiting the top of the TCS Absorber Column (3), now saturated with STC and containing HCl, is next sent to the STC Converter (4 or 15, although STC Converter (4) is shown in Figure 4), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HCl. This unit may be a standard type STC Converter (15), employing very hot graphite heating rods, or a special catalytic non-equilibrium converter ((4), see WO 2013/074425) of the inventor's design, which is carbon- free. Feed to the STC Converter may be augmented with recycle STC from stream 7F. The gas stream 4B exiting the STC converter (4 or 15) is heat exchanged with stream 3C which enters the STC converter, where stream 3C may optionally be mixed with stream 7F. The cooled, but still gaseous, STC converter product stream 4B is sent to the HCl Absorber Column (5), where HCl is absorbed into chlorosilane reflux. The chlorosilane reflux comprises a mixture of STC, TCS and DCS as obtained from an HCl Recovery Column (6) as stream 6H. Hydrogen exiting the top of the HCl Absorber Column (5), now containing STC, TCS and DCS, and identified in Fig. 4 as exit stream 5G, may be delivered to the Reactor (1). Because stream 5G is very cold, for example -50°C, the amount of STC in 5G approaches de minimis levels such that recycle to the Reactor (1) poses no operational issues.

Optionally, stream 5G may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5H exiting the bottom of the HCl Absorber Column (5) is a mixture comprising HCl, TCS, DCS, and STC. This stream 5H is sent to an HCl Recovery Column (6) where HCl is removed overhead in exit stream 6G while STC, TCS, and DCS are removed in the bottoms exit stream 6H. The exit stream 6G may function as a feedstock for a direct chlorination process conducted in a fluidized bed reactor. A portion of the STC, DCS and TCS in the HCl Recovery Column (6) bottoms stream 6H is sent to an STC/TCS Separator Column (7), where TCS and DCS are separated overhead in exit stream 7E, and STC is isolated in the bottoms exit stream 7F. The remainder is used as reflux on the HCl Absorber Column (5). The overhead stream 7E from the STC/TCS Separator Column (7) is directed into a TCS/DCS Separator Column (9) to provide exit stream 9C comprising primarily DCS and exit stream 9D comprising primarily TCS. The exit stream 9D may be sent directly to a CVD reactor as shown in Fig. 4. The exit stream 9C, enriched in DCS, is sent to a Silica Gel Bed (10) whereupon boron contaminants in the DCS may be absorbed into the silica, and purified DCS stream 10B exits the Silica Gel Bed (10). The exit stream 10B comprising largely DCS is directed into a

Commutation Reactor (11), where it is combined with a portion of exit stream 7F from the STC/TCS Separator Column (7) comprising largely STC. Within the Commutation Reactor (11), a product stream 11B is formed comprising largely TCS, but containing residual DCS and STC. This product stream 11B is directed into the STC/TCS

Separator Column (7). Because the HCl Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 6H with the outgoing bottoms stream 5H may be optimally employed. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. Returning to the TCS Absorber Column (3), in addition to forming exit stream 3C comprising H₂ in combination with STC and HCl, there is also formed a bottoms exit stream 3D comprising STC, TCS, DCS and HCl. This stream 3D is sent to an HCl Stripper Column, to create an overhead exit stream 8A comprising HCl, where this HCl is present in the gas stream at a higher concentration than in the feed to the HCl Stripper column, although it is still in combination with a mixture of chlorosilanes, and a bottoms exit stream 8B comprising STC, TCS and DCS. The overhead exit stream 8 A is sent to the TCS Absorber Column (3). The bottoms exit stream 8B is delivered to the STC/TCS Separator Column (7) discussed previously. It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 4, a heat exchanger (21) may be positioned upstream of the STC Converter (4 or 15), with the optional placement of an intermediate Heater (24).

[00124] Thus, in one aspect, the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 4:

b) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to both of an STC Converter (4 or 15) and an HCl Stripper Column; c) the STC Converter (4 or 15) in fluid communication with and providing an exit stream to the HCl Absorber Column (5); d) the HCl Absorber Column (5) in fluid communication with and providing an exit stream to the HCl Recovery Column (6);

e) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to both of the STC/TCS Separator Column (7) and the HCl Absorber Column (5);

g) the TCS/DCS Separator Column (9) in fluid communication with and providing an exit stream to a Silica Gel Bed (10);

j) the HCl Stripper Column in fluid communication with and providing an exit stream to the TCS Absorber and to the STC/TCS Separator Column (7).

[00125] Fig. 5 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the CVD reactor, a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HCl, in addition to unreacted ¾. Exit stream 1A leaving a Siemens CVD reactor is delivered into an HCl Pipeline Reactor (2), where HCl is converted to TCS and STC by reaction with DCS and TCS, respectively. Exit stream 2A from the HCl Pipeline Reactor (2) is scrubbed with STC upon delivery into a TCS Absorber Column (3). STC reflux provided as stream 7H is delivered to the TCS Absorber Column (3) and removes DCS and TCS, present in the exit stream 2A, from the hydrogen stream 3A exiting the top of the column. This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3A exiting the top of the TCS Absorber Column (3), now saturated with STC and containing only small amounts of residual DCS and TCS, is next sent to the STC Converter (4 or 15, although STC Converter (4) is illustrated in Figure 5), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HCl. This unit may be a standard type STC Converter (15), employing very hot graphite heating rods, or a special catalytic non- equilibrium converter of the inventor's design (4), which is carbon-free (see WO 2013/074425). Feed to the STC Converter (4 or 15) may be augmented with recycle STC from stream 7H. The gas stream 4A exiting the STC Converter is heat exchanged with feed to the STC converter. The cooled, but still gaseous, STC Converter product stream 4 A is sent to the HCl Absorber Column (5), where HCl is absorbed into chlorosilane reflux. The chlorosilane reflux is stream 6J, comprised of a mixture of TCS, DCS, and STC. Hydrogen exiting the top of the HCl Absorber Column (5), now saturated with equilibrium amounts of TCS, DCS, and STC, and identified in Fig. 5 as exit stream 51, is scrubbed with TCS and DCS reflux in an STC Absorber Column (12). This removes STC from the hydrogen stream leaving the top of the absorber as exit stream 12A. The hydrogen stream 12A leaving the top of the STC Absorber Column (12) is now saturated with equilibrium amounts of TCS and DCS, instead of a mixture of TCS, STC, and DCS as present in the exit stream from the HCl Absorber Column (5) as provided in alternative embodiments disclosed herein. This improves the efficiency of the CVD reaction step, because TCS - and to a lesser extent DCS - is the reactant in this step, and STC is the reaction by-product. The hydrogen stream 12A leaving the top of the STC Absorber Column (12) is recycled to the Reactor (1), or alternately is purified in a carbon-bed absorber to remove carbon impurities (refinement, if any, is needed only if the case where the STC converters employ graphite heating rods).

Optionally, stream 12A may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5J exiting the bottom of the HCl Absorber Column (5) is a mixture comprised of HCl, TCS, DCS, and STC. This stream is sent to the HCl Recovery Column (6) where HCl is removed overhead in exit stream 61, and STC, TCS, and DCS are removed in the bottoms exit stream 6J. The HCl stream 61 may be used as a feedstock in a direct chlorination process, conducted in a fluidized bed reactor. Most of the STC, DCS, and TCS in the HCl Recovery Column (6) bottoms stream 6J is recycled to the HCl Absorber Column (5), where it is used as column reflux. A portion of the STC, DCS, and TCS in the HCl Recovery Column (6) bottoms stream 6J may be sent to the STC/TCS/TCS Separator Column, where TCS and DCS are separated overhead in exit stream 7G, and STC is removed in the bottoms exit stream 7H. The bottoms stream 12B from the STC Absorber Column (12) is also sent to the STC/TCS Separator Column (7). A portion of the overhead stream 7G from the STC/TCS Separator Column (7) is recycled to the Reactors (1). The remainder is used as the reflux on the STC Absorber Column (12). Because the HCl Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange (not shown in figure) of the incoming reflux stream 6J with the outgoing bottoms stream 5J may be optimally employed. Additional cooling of the reflux stream 6J and/or gas geed stream 5J, if required, may be performed using a refrigerant-cooled heat exchanger. It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 5, a heat exchanger (21) may be positioned upstream of the STC Converter (4 or 15), with the optional placement of an intermediate Heater (24).

[00126] Thus, in one aspect, the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 5:

c) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to both of an STC Converter (4 or 15) and an STC/TCS Separator Column (7);

d) the STC Converter (4 or 15) in fluid communication with and providing an exit stream to the HCl Absorber Column (5);

e) the HCl Absorber Column (5) in fluid communication with and providing an exit stream to both of the HCl Recovery Column (6) and an STC Absorber Column (12);

f) the STC Absorber Column (12) in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7);

g) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to both of the STC/TCS Separator Column (7) and the HCl Absorber Column (5); and h) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to each of the TCS Absorber Column (3), the STC Converter (4 or 15), and the STC Absorber Column (12).

[00127] Fig. 6 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the CVD reactor, a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HC1, in addition to unreacted H₂. Exit stream 1A leaving a Siemens CVD reactor is delivered into an HC1 Pipeline Reactor (2), where HC1 is converted to TCS and STC by reaction with DCS and TCS, respectively. Exit stream 2A from the HC1 Pipeline Reactor (2) is scrubbed with STC upon delivery into a TCS Absorber Column (3). The STC is delivered to the TCS Absorber Column (3) via stream 7J from an STC/TCS Separator Column (7). STC reflux to the TCS Absorber Column (3) removes DCS and TCS, present in the exit stream 2A, from the hydrogen stream 3A exiting the top of the column. This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3 A exiting the top of the STC Absorber Column (12), now saturated with STC and containing only small amounts of residual DCS and TCS, is next sent to the STC Converter (4 or 15), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HC1. The bottom stream 3B from the TCS Absorber is sent to the STC/TCS Separator Column (7). The STC Converter unit may be a standard type STC Converter (15), employing very hot graphite heating rods, or a catalytic non-equilibrium STC Converter (4). In each of the embodiments shown herein, the catalytic STC Converter (4) may be fitted with filters (not shown) to remove catalyst particles, if any, from the exit stream, which is carbon- free. Feed to the STC converter (4 or 15) may be augmented with recycle STC from stream 7 J. The gas stream 4A exiting the STC converter may be heat exchanged with stream 3A to the STC converter, where stream 3A may optionally be combined with recycle STC from stream 7J. The cooled, but still gaseous, STC converter product stream 4 A is sent to the HC1 Absorber Column (5), where HC1 is absorbed into a chlorosilane reflux. The chlorosilane reflux comprises of a mixture of TCS, DCS, and STC, and is obtained as an exit stream 6J from an HC1 Recovery Column (6). Hydrogen exiting the top of the HC1 Absorber Column (5), now saturated with equilibrium amounts of TCS, DCS, and STC, and identified in Fig. 6 as exit stream 51, is scrubbed with TCS reflux (stream 9F from a TCS/DCS Separator Column (9)) in an STC Absorber Column (12). This removes STC from the hydrogen stream leaving the top of the STC Absorber Column (12) as exit stream 12C. The hydrogen stream 12C leaving the top of the STC Absorber Column (12) is now saturated with relatively pure TCS, instead of a mixture of TCS, STC, and DCS as present in the exit stream from the HC1 Absorber Column (5) as provided in alternative embodiments disclosed herein. This improves the efficiency of the CVD reaction step, because TCS is the reactant in this step, and STC is the reaction by-product. The hydrogen stream 12C leaving top of the STC Absorber Column (12) is recycled to the Reactor (1), or alternately is refined to remove carbon impurities (refinement, if any, is needed only if the case where the STC converters employ graphite heating rods). Optionally, stream 12C may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5J exiting the bottom of the HC1 Absorber Column (5) is a mixture comprising HC1, TCS, DCS, and STC. This stream is sent to the HC1 Recovery Column (6) where HC1 is removed overhead in exit stream 61, and STC, TCS, and DCS are removed in a bottoms exit stream 6J. The HC1 stream 61 may be used as a feedstock in a direct chlorination process, conducted in a fluidized bed reactor. Most of the STC, DCS, and TCS in the HC1 Recovery Column (6) bottoms stream 6J is recycled to the HC1 Absorber Column (5), where it is used as column reflux. A portion of the STC, DCS, and TCS in the stream 6J may be sent to the STC/TCS Separator Column (7), where TCS and DCS are separated overhead in exit stream 71, and STC is removed in a bottoms exit stream 7J. The bottoms stream 12D from the STC Absorber Column (12) is also sent to the STC/TCS Separator Column (7). The overhead stream 71 from the STC/TCS Separation Column is directed into a TCS/DCS Separator Column (9) to provide exit stream 9E comprising primarily DCS and exit stream 9F comprising primarily TCS. The exit stream 9F is used, in part, to provide TCS reflux to the STC Absorber Column (12), however exit stream 9F can also be sent to a CVD reactor. The exit stream 9E, enriched in DCS, is sent to a Silica Gel Bed (10) wherein boron contaminants in the DCS may be absorbed into the silica, and purified DCS stream IOC exits the Silica Gel Bed (10). The exit stream IOC comprising largely DCS is directed into a Commutation Reactor (11), where it is combined with a portion of exit stream 7J from the STC/TCS Separator Column (7) comprising largely STC. Within the Commutation Reactor (11), a product stream 11C is formed comprising largely TCS, but containing residual DCS and STC. This product stream 11C is directed into the STC/TCS Separator Column (7). Because the HCl Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 6J with the outgoing bottoms stream 5J may be optimally employed. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 6, a heat exchanger (21) may be positioned upstream of the STC Converter (4 or 15), with the optional placement of an intermediate Heater (24).

[00128] Thus, in one aspect, the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 6:

c) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to both of the STC Converter (4 or 15) and the STC/TCS Separator Column (7);

g) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to both of the STC/TCS Separator Column (7) and the HCl Absorber Column (5); h) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to each of the TCS Absorber Column (3), the STC Converter (4 or 15), and a TCS/DCS Separator Column (9) and a Commutation Reactor (11);

i) the TCS/DCS Separator Column (9) in fluid communication with and providing an exit stream to both of the STC Absorber Column (12) and a Silica Gel Bed (10);

j) the Silica Gel Bed (10) in fluid communication with and providing an exit stream to a Commutation Reactor (11); and

k) the Commutation Reactor (11) in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7).

[00129] Relative to the system and process illustrated in Fig. 5, the system and process illustrated in Fig. 6 provides additional unit operations to separate DCS from TCS, to remove boron species and particularly BCI3 from DCS, and to convert DCS to TCS in a Commutation Reactor (11). In addition, mixed chlorosilane reflux as delivered to the top of the STC Absorber is replaced with relatively pure TCS in the embodiment of Figure 6. Lastly, hydrogen exiting the top of the STC Absorber is now saturated with equilibrium amounts of TCS, instead of a mixture of TCS and DCS. This improves the efficiency of the CVD reaction step, because TCS is the principal reactant in this step.

[00130] Fig. 7 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the Reactor (1), a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HC1, in addition to unreacted H₂. Exit stream 1A leaving a Siemens CVD reactor is scrubbed with STC upon delivery into a TCS Absorber Column (3). STC reflux to the TCS Absorber Column (3), delivered via stream 7L from an STC/TCS Separator Column (7), removes DCS and TCS, present in the exit stream 1A, from the hydrogen stream 3C exiting the top of the TCS Absorber Column (3). This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3C exiting the top of the TCS Absorber Column (3), now saturated with STC and still containing virtually all the HC1 fed to the TCS Absorber Column (3) in stream 1A, is next sent to the STC Converter (4 or 15), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HCl. This unit may be a standard type STC Converter (15), employing very hot graphite heating rods, or a special catalytic non-equilibrium STC Converter (4) of the inventor's design, which is carbon- free (see WO 2013/074425). Feed to the STC Converter (4 or 15) may be augmented with recycle STC via stream 7L from an STC/TCS Separator Column (7). The gas stream 4B exiting the STC converter may be heat exchanged with stream 3C, and optionally a portion of stream 7L preferably in vaporized form, entering the STC converter. The cooled, but still gaseous, STC converter product stream 4B is sent to an HCl Absorber Column (5), where HCl is absorbed into chlorosilane reflux. The chlorosilane reflux is comprised of a mixture of TCS, DCS, and STC, and is denoted as stream 6J. Hydrogen exiting the top of the HCl Absorber Column (5), now saturated with equilibrium amounts of TCS, DCS, and STC, and identified in Fig. 7 as exit stream 51, is delivered to an STC Absorber Column (12) where it is scrubbed with TCS reflux (stream 9H). This removes STC from the hydrogen stream leaving the top of the STC Absorber Column (12) as exit stream 12E. The hydrogen stream 12E is saturated with relatively pure TCS, instead of a mixture of TCS, STC, and DCS as present in the exit stream from the STC Absorber Column (12) as provided in alternative

embodiments disclosed herein. This improves the efficiency of the CVD reaction step, because TCS is the reactant in this step, and STC is the reaction by-product. The hydrogen stream 12E leaving top of the STC Absorber Column (12) may be recycled to the Reactor (1), or alternately it may be refined to remove carbon impurities

(refinement, if any, is needed only if the case where the STC converters employ graphite heating rods). Optionally, stream 12E may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5J exiting the bottom of the HCl Absorber Column (5) is a mixture comprising HCl, TCS, DCS, and STC. This stream 5J is sent to an HCl Recovery Column (6) where HCl is removed overhead in exit stream 61, and STC, TCS, and DCS are removed in the bottoms exit stream 6J. The HCl stream 61 may be used as a feedstock in a direct chlorination process, conducted in a fluidized bed reactor. Most of the STC, DCS, and TCS in the HCl Recovery Column (6) bottoms stream 6J is recycled to the HCl Absorber Column (5), where it is used as column reflux. A portion of the bottoms stream 6J may be sent to the STC/TCS Separator Column (7), where TCS and DCS are separated overhead in exit stream 7K, and STC is removed in the bottoms exit stream 7L. The bottoms stream 12F from the STC Absorber Column (12) is also sent to the STC/TCS Separator Column (7). The overhead stream 7K from the STC/TCS Separator Column (7) is directed into a TCS/DCS Separator Column (9) to provide overhead exit stream 9G comprising primarily DCS and bottoms exit stream 9H comprising primarily TCS. The exit stream 9H is used, in part, to provide TCS reflux to the STC Absorber Column (12), however exit stream 9H may also be sent directly to a Reactor (1). The exit stream 9G, enriched in DCS, is sent to a Silica Gel Bed (10) wherein boron contaminants in the DCS may be absorbed into the silica, and purified DCS stream 10D exits the Silica Gel Bed (10). The exit stream lOd comprising largely DCS is directed into a Commutation Reactor (11), where it is combined with exit stream 7L from the STC/TCS Separator Column (7) comprising largely STC. Within the Commutation Reactor (11), a product stream 11D is formed comprising largely TCS, but containing residual DCS and STC. This product stream 11D is directed into the STC/TCS Separator Column (7). Because the HC1 Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 6J with the outgoing bottoms stream 5J may be optimally employed. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. Returning to the TCS Absorber Column (3), in addition to the overhead stream 3C comprising largely STC, HC1 and H₂, there is also produced a bottoms exit stream 3D comprising largely STC/TCS/DCS/HC1. The stream3D is directed to an HC1 Stripper Column for separation of the HC1 in an overhead exit stream 8A and a bottoms stream 8B comprising STC, TCS and DCS. The bottoms stream 8B is directed to the STC/TCS Separator Column (7) discussed previously. The overhead stream 8A is directed to the TCS Absorber Column (3). It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 7, a heat exchanger (21) may be positioned upstream of the STC Converter (4 or 15), with the optional placement of an intermediate Heater (24).

[00131] Thus, in one aspect, the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 7: a) a Reactor (1) selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor in fluid communication with and providing an exit stream to a TCS Absorber Column (3);

b) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to the STC Converter (4 or 15) and an HCl Stripper Column;

c) the HCl Stripper Column in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7) and the TCS Absorber Column (3); d) the STC Converter (4 or 15) in fluid communication with and providing an exit stream to the HCl Absorber Column (5);

g) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to both of the STC/TCS Separator Column (7) and the HCl Absorber Column (5);

h) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to each of the TCS Absorber Column (3), the STC Converter (4 or 15), and a TCS/DCS Separator Column (9) and a Commutation Reactor (11);

[00132] Fig. 8 illustrates an embodiment of the present manufacturing plant and a process of operating the same, which is identical to the plant and process illustrated in Fig. 7, with one exception. As mentioned in the discussion of Fig. 7, because the HCl Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 6J with the outgoing bottoms stream 5J may be optimally employed. This embodiment employed heat interchange between streams 5J and 6J is illustrated in Fig. 8. In general, heat interchange may or may not be provided in any of the embodiments shown in Figures 1-11, between streams entering or exiting any of the HCl Absorber Column (5) and the HCl Recovery Column (6).

[00133] Fig. 9 illustrates an embodiment of the present manufacturing plant and a process of operating the same. The plant comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the reactor (1), a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HCl, in addition to unreacted ¾. Exit stream 1A leaving a reactor (1) is scrubbed with STC upon delivery into a TCS Absorber Column (3). STC reflux to the TCS Absorber Column (3), delivered via stream 7N from an STC/TCS Separator Column (7), removes DCS and TCS, present in the exit stream 1A, from the hydrogen stream 3C exiting the top of the TCS Absorber Column (3). This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3C exiting the top of the STC Absorber Column (12), now saturated with STC and containing HCl, is next sent to the STC Converter (4 or 15), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HCl. This unit may be a standard type STC Converter (15), employing very hot graphite heating rods, or a special catalytic non-equilibrium STC Converter ((4), see WO 2013/074425) of the inventor's design, which is carbon-free. Feed to the converter may be augmented with recycle STC via feed 7N from an STC/TCS Separator Column (7). The gas stream 4B exiting the STC Converter (4 or 15) may be heat exchanged with stream 3C to the STC converter (4 or 15), where stream 3C may optionally be combined with stream 7N. The cooled, but still gaseous, STC converter product stream 4B is sent to the STC Converter Off-gas Scrubber Column (13), and is scrubbed with STC from stream 7N. The STC Converter Off-gas Scrubber Column (13) is also in fluid communication with an HCl Stripper Column, where bottoms stream 13B exits the STC Converter Off-gas Scrubber Column (13) and enters the HCl Stripper Column, and overhead stream 14A exits the HCl Stripper Column and enters the STC Converter Off-gas Scrubber Column (13) while bottoms stream 14B comprising STC, TCS and DCS exits the HCl Stripper Column and enters the STC/TCS Separator Column (7). Overhead exit stream 13A comprising STC, HCl and hydrogen exits the STC Converter Off-gas Scrubber Column (13) and enters an HCl Absorber Column (5). In the HCl Absorber Column (5), HCl is absorbed into chlorosilane reflux 6L obtained from an HCl Recovery Column (6). The chlorosilane reflux 6L comprises mainly STC. Hydrogen exits the top of the HCl Absorber Column (5), now saturated with STC, and identified in Fig. 9 as exit stream 5K. The stream 5K may be directly fed into the Reactor (1). Optionally, stream 5K may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). The liquid stream 5L exiting the bottom of the HCl Absorber Column (5) is a mixture comprising HCl and STC. This stream 5L is sent to an HCl Recovery Column (6) where HCl is removed overhead in exit stream 6K, and STC is removed in the bottoms exit stream 6L. The HCl stream 6K may be used as a feedstock in a direct chlorination process, conducted in a fluidized bed reactor. The STC in the HCl Recovery Column (6) bottoms stream 6L is recycled to the HCl Absorber Column (5), where it is used as column reflux. Turning now to the STC/TCS Separator Column (7), this column receives a mixture of STC, TCS and DCS from each of the STC Converter Off-gas Scrubber Column (13), the HCl Recovery Column (6), and the HCl Stripper discussed below. From the STC/TCS Separator Column (7) there is obtained an overhead exit stream 7M comprising largely TCS and DCS, where this stream 7M may be directly used as a feedstock to a Reactor (1). The STC/TCS Separator Column (7) also provides a bottoms exit stream 7N, which may be utilized in one or more of the following ways: as reflux to the TCS Absorber Column (3), as co- feed to the STC Converter (4 or 15), and as reflux to the STC Converter Off-gas Scrubber Column (13). Because the HCl Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 6L with the outgoing bottoms stream 5L may be optimally employed. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. Returning to the TCS Absorber Column (3), in addition to the overhead stream 3C comprising largely STC, HCl and H₂, there is also produced a bottoms stream 3D comprising largely STC/TCS/DCS/HC1. The stream3D is directed to an HCl Stripper Column for separation of the HCl into an overhead exit stream 8A and a bottoms stream 8B comprising STC, TCS and DCS. The bottoms stream 8B is directed to the STC/TCS Separator Column (7) discussed previously, while the exit stream 8A is directed to the TCS Absorber Column (3). It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 9, a heat exchanger (21) may be positioned upstream of the STC Converter (4 or 15), with the optional placement of an intermediate Heater (24).

[00134] Thus, in one aspect, the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 9:

b) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to an STC Converter (4 or 15) and an HCl Stripper Column;

c) the HCl Stripper Column in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7) and the TCS Absorber Column (3); d) the STC Converter (4 or 15) in fluid communication with and providing an exit stream to an STC Converter Off-gas Scrubber Column (13);

e) the STC Converter Off-gas Scrubber Column (13) in fluid communication with and providing an exit stream to and receiving an exit stream from the HCl Stripper Column, where the HCl Stripper Column is also in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7);

f) the STC Converter Off-gas Scrubber Column (13) in fluid communication with an providing an exit stream to the HCl Absorber Column (5);

g) the HCl Absorber Column (5) in fluid communication with and providing an exit stream to the HCl Recovery Column (6);

h) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to the HCl Absorber Column (5) and an exit stream to the STC/TCS Separator Column (7); and

i) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to each of the TCS Absorber Column (3), the STC Converter (4 or 15), and the Off-gas Scrubber Column.

[00135] Fig. 10 illustrates an embodiment of the present manufacturing plant and a process of operating the same. In Figures 1-9, an STC Converter operating in a catalytic manner is illustrated ((4), see WO 2013/074425). However, in any of those Figures, the Catalytic STC Converter (4) may be replaced with a standard STC

Converter (15). The use of a standard STC Converter (15) is specifically illustrated in Fig. 10. As shown in Fig. 10, there is provided a plant comprising a Reactor (1), which as always herein may be either a CVD reactor or FBR, wherein the well-known Siemens reaction takes place. In the Reactor (1), a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HCl, in addition to unreacted H₂. Exit stream 1A leaving the Siemens CVD reactor is scrubbed with STC upon delivery into a TCS Absorber Column (3). STC reflux to the TCS Absorber Column (3), delivered via stream 7P from an STC/TCS Separator Column (7), removes DCS and TCS, present in the exit stream 1A, from the hydrogen stream 3C exiting the top of the TCS Absorber Column (3). This improves the efficiency of the STC conversion step, because STC is the reactant in this step, and TCS and DCS are products. The hydrogen stream 3C exiting the top of the STC Absorber Column (12), now saturated with STC and containing HCl, is next sent to the standard STC Converter (15), where a portion of the STC in said stream is reacted with hydrogen to produce TCS and HCl. This unit is the standard type STC Converter (15), employing very hot graphite heating rods. Feed to the converter may be augmented with recycle STC via feed 7P from an STC/TCS Separator Column (7). The gas stream 15A exiting the standard STC Converter (15) may be heat exchanged with stream 3C, and optionally a portion of stream 7P, to the standard STC Converter (15). The cooled, but still gaseous, STC Converter (15) product stream 15A is sent to the STC Converter Off-gas Scrubber Column (13). A Carbon Absorption Bed (18), located downstream of the HCl Absorber Column (5), is used to remove carbon contaminants produced in the standard STC Converter (15) and STC from stream 5M, where those carbon contaminants and STC content may exit the Carbon Absorption Bed (18) as a methyl and STC purge shown as stream 18B. The bulk of the stream 5M, entering the Carbon Absorption Bed (18) exits the Carbon Absorption Bed (18) as stream 18 A, comprising hydrogen, and is recycled to the Reactor (1). Optionally, stream 18A may be passed through a Hydrogen Recycle Compressor (16) to provide a stream 16A that is recycled to the Reactor (1). Also entering the STC Converter Off-gas Scrubber Column (13) is a reflux feed 7P comprising STC, which is obtained from an STC/TCS Separator Column (7). The STC Converter Off-gas Scrubber Column (13) generates an overhead stream 13C comprising H₂, HC1 and STC which enters the bottom of an HC1 Absorber Column (5). The STC Converter Off-gas Scrubber Column (13) is also in fluid communication with an HC1 Stripper Column, where bottoms stream 13D exits the STC Converter Off-gas Scrubber Column (13) and enters the HC1 Stripper Column, and overhead stream 14C exits the HC1 Stripper Column and enters the STC Converter Off-gas Scrubber Column (13), while bottoms stream 14D exits the HC1 Stripper Column and enters the STC/TCS Separator Column (7). In the HC1 Absorber Column (5), HC1 is absorbed into chlorosilane reflux 6N. The chlorosilane reflux 6N is comprised primarily of STC and is generated as a bottoms exit stream from an HC1 Recovery Column (6). Hydrogen exits the top of the HC1 Absorber Column (5), now saturated with STC, and identified in Fig. 10 as exit stream 5M. The stream 5M is preferentially fed to the aforementioned Carbon Absorption Bed (18) to remove methyl and other carbon impurities and STC content, or may optionally be directly fed into the Reactor (1). The liquid stream 5N exiting the bottom of the HC1 Absorber Column (5) is a mixture comprising HC1 and STC. This stream 5N is sent to an HC1 Recovery Column (6) where HC1 is removed overhead in exit stream 6M, and STC is removed in the bottoms exit stream 6N. A portion of stream 6N may be purged to the STC/TCS Separator Column (7) to maintain the STC balance in the HC1 Absorber Column (5) and HC1 Recovery Column (6) System. The HC1 stream 6M may be used as a feedstock in a direct chlorination process, conducted in a fluidized bed reactor. The STC in the HC1 Recovery Column (6) bottoms stream 6N is recycled to the HC1 Absorber Column (5), where it is used as column reflux. Because the HC1 Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 6N with the outgoing bottoms stream 5N may be optimally employed.

Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. Returning to the TCS Absorber Column (3), in addition to the overhead stream 3C comprising largely STC, HC1 and H₂, there is also produced a bottoms stream 3D comprising largely STC/TCS/DCS/HCl. The stream 3D is directed to an HC1 Stripper Column for separation of the HC1 in an overhead exit stream 8A and a bottoms stream 8B comprising STC, TCS and DCS. The bottoms stream 8B is directed to an STC/TCS Separator Column (7), from which there is produced a bottoms stream 7P comprising largely STC. The overhead stream 70 from the STC/TCS Separator Column (7) comprises largely TCS and DCS, and this stream 70 may be directly used in a Reactor (1). Optionally, 70 may be directed to a

Distillation Column (19) for removal of methyl and other carbon impurities, and then used in the Reactor (1). The overhead exit stream 8A, comprising HCl, is directed into the TCS Absorber Column (3). It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 10, a heat exchanger (21) may be positioned upstream of the STC Converter (15), with the optional placement of an intermediate Heater (24).

[00136] Thus, in one aspect, the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 10:

b) the TCS Absorber Column (3) in fluid communication with and providing an exit stream to the STC Converter (15) and an HCl Stripper Column;

c) the HCl Stripper Column in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7) and the TCS Absorber Column (3); d) the STC Converter (15) in fluid communication with and providing an exit stream to an STC Converter Off-Gas Scrubber;

f) the STC Converter Off-gas Scrubber Column (13) in fluid communication with and providing an exit stream to the HCl Absorber Column (5);

g) the HCl Absorber Column (5) in fluid communication with and providing an exit stream to the HCl Recovery Column (6) and an exit stream to a Carbon Absorption Bed (18);

h) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to the HCl Absorber Column (5) and an exit stream to the STC/TCS Separator Column (7); and i) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to each of the TCS Absorber Column (3), the STC Converter (15), the STC Converter Off-gas Scrubber Column (13), and optional distillation equipment.

[00137] Fig. 11 illustrates an embodiment of the present manufacturing plant and a process of operating the same. In the embodiments illustrated in Figures 1-10, a TCS Absorber Column (3), optionally in combination with an HC1 Stripper Column, was used to create a hydrogen enriched overhead stream and a chlorosilane enriched bottoms stream. An alternative approach to separating hydrogen from chlorosilane in the off-gas from the Reactor (1), which may be used in any of the configurations of Figures 1-10, is specifically illustrated in Figure 11. The plant illustrated by Figure 11 comprises a CVD reactor or FBR (1) wherein the well-known Siemens reaction takes place. In the Reactor (1), a feedstock comprising hydrogen (H₂) and TCS is exposed to polysilicon rods in a high temperature environment. The TCS decomposes to polysilicon, while creating an exit stream 1A comprising byproduct STC, unreacted TCS, DCS and HC1, in addition to unreacted H₂. Exit stream 1A leaving the Siemens CVD reactor is delivered into an HC1 Pipeline Reactor (2), where HC1 is converted to TCS and STC by reaction with DCS and TCS, respectively. Exit stream 2A from the HC1 Pipeline Reactor (2) is delivered to a Refrigerator/ Decanter (17) from which an overheads stream 17A enriched in H₂ is obtained, while simultaneously there is obtained a bottoms stream 17B enriched in STC, TCS and DCS. Optionally, either or both of the streams 17A and 17B may be heat exchanged using a Heat Exchanger (23) with the feedstock gas stream 2 A, as shown in Fig. 11. Refrigeration is applied to the stream 2A prior to and/or during the decanter- facilitated separation of H₂ from chlorosilanes, in order to increase the efficiency of the separation; temperatures as low as -80°C may be employed. Hydrogen, if any, in stream 17B and/or stream 7Q may be separated as a gas in a decanter (not shown) and be sent to the STC Converter Off-gas Scrubber Column (13). The chlorosilane stream 17B is delivered to an STC/TCS Separator Column (7), from which an overhead stream 7Q comprising TCS and DCS is obtained, while simultaneously there is obtained a bottoms stream 7R comprising largely purified STC. The STC stream 7R is, in part, combined with hydrogen stream 17A and the mixture delivered to an STC Converter (4 or 15). A portion of the STC from streams 17A and 7R is reacted with hydrogen to produce STC, TCS, DCS, HC1 and hydrogen. This unit may be a standard type STC converter (15), employing very hot graphite heating rods, or a special catalytic non-equilibrium STC Converter (4) which is carbon-free (see WO 2013/074425). Feed to the STC Converter (4 or 15), i.e., the combination of streams 17A and a portion of stream 7R, may be heat exchanged with exit stream 4C from the STC Converter. The cooled, but still gaseous, STC Converter product stream 4C is sent to an STC Converter Off-gas Scrubber Column (13), and is scrubbed with STC from stream 7R. The STC Converter Off-gas Scrubber Column (13) is also in fluid communication with an HCl Stripper Column (14), where bottoms stream 13F exits the STC Converter Off-gas Scrubber Column (13) and enters the HCl Stripper Column (14), and overhead stream 14E exits the HCl Stripper Column and enters the STC Converter Off-gas Scrubber Column (13), while bottoms stream 14F exits the HCl Stripper Column and enters the STC/TCS Separator Column (7). Overhead stream 13E consisting of STC, HCl and hydrogen exits the STC Converter Off-gas Scrubber Column (13) and enters an HCl Absorber Column (5). In the HCl Absorber Column (5), HCl from stream 13E is absorbed into chlorosilane reflux 6P obtained from an HCl Recovery Column (6). The chlorosilane reflux 6P is comprised primarily of STC. Hydrogen exits the top of the HCl Absorber Column (5), now saturated with STC, and identified in Fig. 11 as exit stream 50. The stream 50 may be directly fed into the Reactor (1), or it may optionally pass through an H₂ recycle compressor (16) to provide stream 16A which is directly fed into the Reactor (1). The liquid stream 5P exiting the bottom of the HCl Absorber Column (5) is a mixture comprising HCl and STC. This stream 5P is sent to an HCl Recovery Column (6) where HCl is removed overhead in exit stream 60, and STC is removed in the bottoms exit stream 6P. The HCl stream 60 may be used as a feedstock in a direct chlorination process, conducted in a fluidized bed reactor. Optionally, the stream 60 may be fed into an HCl Liquifaction Unit (20) to provide an exit stream 20A which is fed into a direct chlorination process conducted in a fluidized bed reactor, and an exit stream 20B which is a hydrogen purge. The STC in the stream 6P is recycled back to the HCl Absorber Column (5), where it is used as column reflux. Optionally, the exit stream 6P may be fed into the STC/TCS Separator Column (7). The embodiment of Figure 11 also provides an STC/TCS Separator Column (7), which receives mixture comprising STC and TCS from each of the Decanter mentioned previously, and the STC Converter Off-gas Scrubber Column (13) also mentioned previously, and the STC purge stream 6P. The overhead stream 7Q from the STC/TCS Separator Column (7) comprises largely TCS and DCS, and this stream 7Q may be directly used in a Reactor (1). The bottoms stream 7R comprising largely STC may be used as co-feed to the STC

Converter (4 or 15), and as column reflux in the STC Converter Off-gas Scrubber Column (13). Because the HCl Absorber Column (5) may be operated at very low temperatures, to improve absorption efficiency, heat interchange of the incoming reflux stream 6P with the outgoing bottoms stream 5P may be optimally employed, although the heat exchanger (22) is an optional operating unit. Additional cooling of the reflux stream, if required, may be performed using a refrigerant-cooled heat exchanger. It is noted that the foregoing description does not include all necessary or optional heat exchange equipment which a person well versed in the art would understand is essential or optimal for operation. For example, as shown in Fig. 11, a heat exchanger (21) may be positioned upstream of the STC Converter (4 or 15), with the optional placement of an intermediate Heater (24).

[00138] Thus, in one aspect, the present disclosure provides a system, and an associated process, comprising, as illustrated in Fig. 11 :

b) the HCl Pipeline Reactor (2) in fluid communication with and providing an exit stream to a Refrigerated Decanter (17);

c) the Refrigerated Decanter (17) in fluid communication with and providing an exit stream to the STC Converter (4 or 15) and the STC/TCS Separator Column (7); d) the STC Converter (4 or 15) in fluid communication with and providing an exit stream to an STC Converter Off-gas Scrubber Column (13);

e) the STC Converter Off-gas Scrubber Column (13) in fluid communication with and providing an exit stream to and receiving an exit stream from an HCl Stripper Column, where the HCl Stripper Column is also in fluid communication with and providing an exit stream to the STC/TCS Separator Column (7);

g) the HCl Absorber Column (5) in fluid communication with and providing an exit stream to the HCl Recovery Column (6); h) the HCl Recovery Column (6) in fluid communication with and providing an exit stream to the HCl Absorber Column (5) and an exit stream to the STC/TCS Separator Column (7); and

i) the STC/TCS Separator Column (7) in fluid communication with and providing an exit stream to each of the STC Converter (4 or 15) and the STC Converter Off-gas Scrubber Column (13).

[00139] A system or plant as provided herein may also include one or more operational units that control, e.g., raise or lower or maintain, the temperature within an operational unit or a conduit that provides for transfer of a chemical from one operational unit to another operational unit. For example, heat exchangers, cooling towers, and the like.

Embodiments

[00140] The following are some specific numbered embodiments of the systems and processes disclosed herein. These embodiments are exemplary only. It will be understood that the invention is not limited to the embodiments set forth herein for illustration, but embraces all such forms thereof as come within the scope of the above disclosure.

1) A process comprising:

a. producing a first vent gas from a Reactor, the first vent gas comprising STC, TCS, HCl and H₂; optionally DCS may be a component of the first vent gas; optionally the Reactor produces poly silicon; optionally the Reactor is a CVD Reactor, optionally the Reactor is a FB Reactor;

optionally the Reactor receives TCS as a feedstock in order to produce the polysilicon;

b. separating components of the first vent gas or a portion thereof to

provide at least two separate exit streams, a first exit stream comprising at least 50% of the STC and at least 75% of the H₂ present in the first vent gas, and a second exit stream comprising at least 50% of the TCS and at least 50% of the DCS present in the first vent gas; and c. feeding the first exit stream comprising STC and H₂ to an STC Converter to provide a second vent gas comprising STC, TCS, DCS, HCl and H₂. ) The process of embodiment 1 wherein the first vent gas is produced from the Reactor to which is fed TCS and wherein is produced polysilicon.

) The process of any of embodiments 1-2 wherein the first vent gas is treated to remove the HCl from other components of the first vent gas, to provide an HQ- depleted first vent gas which is a portion of the first vent gas.

) The process of any of embodiments 1-3 wherein the separating comprises feeding the first vent gas or a portion thereof to a TCS Absorber Column.) The process of embodiment 4 wherein fresh STC is fed into the TCS Absorber Column.

) The process of embodiment 4 wherein the first exit stream also comprises HCl.) The process of any of embodiments 1-6 wherein the second exit stream or a fraction thereof is fed into an STC/TCS Separator Column.

) The process of any of embodiments 1-7 wherein the second exit stream also comprises HCl.

) The process of embodiment 8 wherein the second exit stream is fed into an HCl Stripper Column which provides an HCl-depleted mixture comprising STC and TCS.

0) The process of embodiment 9 wherein the HCl-depleted mixture comprising STC and TCS is fed into an STC/TCS Separator Column.

1) The process of any of embodiments 1-10 wherein the STC Converter comprises metal silicide catalyst and is operated in a non-equilibrium mode.

2) The process of any of embodiments 1-11 wherein

a. the second exit stream is fed into an STC/TCS Separator Column; and b. a portion of the second vent gas comprising STC and TCS is also fed into the STC/TCS Separator Column.

3) The process of any of embodiments 1-12 wherein

a. the second exit stream is fed into an HCl Stripper Column to provide an HCl-depleted mixture of TCS and DCS;

b. the HCl-depleted mixture of TCS and DCS is fed into an STC/TCS Separator Column; and

c. a portion of the second vent gas comprising STC and TCS is also fed into the STC/TCS Separator Column.

4) A system comprising: a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor, the Reactor producing a vent gas comprising STC, TCS, HC1 and H₂, the vent gas optionally containing DCS; the Reactor optionally producing polysilicon from a feedstock comprising TCS;

b. a TCS Absorber Column in fluid communication with the Reactor, wherein the TCS Absorber Column receives i) the first vent gas from the Reactor or a portion thereof and ii) a fresh portion of STC, and wherein a first exit stream comprising at least 50% of the STC and at least 75% of the H₂ present in the first vent gas, and a second exit stream comprising at least 50% of the TCS and at least 50% of the DCS present in the first vent gas, both exit the TCS Absorber Column; and

c. an STC Converter in fluid communication with the TCS Absorber

Column, where the STC Converter receives the first exit stream from the TCS Absorber Column (3) and provides a second vent gas comprising STC, TCS, DCS, HC1 and H₂.

) The system of embodiment 14 wherein an HCl-Pipeline Reactor is in located between, and is in fluid communication with each of, the reactor and the STC Absorber Column.

) The system of embodiment 14 wherein an STC/TCS Separator Column is in fluid communication with each of the STC Converter and the TCS Absorber Column, where exit streams or fractions thereof from the STC Converter and the Absorber Column are each fed into the STC/TCS Separator Column.

) The system of embodiment 14 wherein an HC1 Stripper Column is located between, and is in fluid communication with each of the TCS Absorber Column and the STC/TCS Separator Column.

) The system of embodiment 14 wherein the STC Converter is in fluid communication with and provides the second vent gas to an HC1 Absorber Column.

) The system of embodiment 18 wherein the HC1 Absorber Column is in fluid communication with and provides HC1, STC and TCS, and optionally DCS, to an HC1 Recovery Column. ) The system of embodiment 19 wherein the HCl Recovery Column is in fluid communication with and provides HCl, STC and TCS, and optionally DCS, to the STC/TCS Separator Column.

) The system of embodiment 14 wherein the STC Converter comprises catalyst.) A system comprising:

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor which produces a first vent gas comprising STC, TCS, HCl and H₂, where the first vent gas optionally also contains DCS; where the Reactor optionally produces polysilicon from a feedstock comprising TCS;

b. a Refrigerator/Decanter combination, wherein the combination receives i) the first vent gas from the Reactor or a portion thereof and generates a first exit stream and a second exit stream, the first exit stream

comprising at least 50% of the STC and at least 75% of the H₂ present in the first vent gas, and the second exit stream comprising at least 50% of the TCS and at least 50% of the DCS present in the first vent gas;

c. an STC Converter, where the STC Converter receives the first exit

stream and provides a second vent gas comprising STC, TCS, DCS, HCl and H₂.

) A process comprising:

a. producing a first vent gas comprising STC, TCS, HCl and H₂ from a Reactor, optionally selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor; where optionally DCS is also part of the first vent gas; the first vent gas is optionally produced in a Reactor wherein polysilicon is produced and STC, TCS, HCl and H₂ (and optionally DCS) are by-products of the polysilicon producing reaction; b. producing a second exit stream comprising STC and TCS but not appreciable amounts of HCl or H₂ from the first vent gas;

c. feeding the second exit stream into an STC/TCS Separator Column; d. producing a second vent gas comprising STC, TCS, DCS, HCl and H₂ from an STC Converter;

e. producing a third exit stream comprising STC and TCS but not appreciable amounts of HCl or H₂ from the second vent gas; f. feeding the third exit stream into the STC/TCS Separator Column; and g. separating STC from TCS in the STC/TCS Separator Column.

) The process of embodiment 23 wherein the reactor is a CVD reactor that produces polysilicon.

) The process of embodiment 23 wherein the first vent gas is fed into a TCS Absorber Column along with fresh STC and the second exit stream exits the TCS Absorber Column.

) The process of embodiment 23 wherein the second exit stream is fed into an HC1 Stripper Column to remove HC1 before being fed into the STC/TCS Separator Column.

) The process of embodiment 23 wherein the STC Converter is operated under non-equilibrium conditions.

) The process of embodiment 23 wherein the second vent gas is fed sequentially into an HC1 Absorber Column and an HC1 Recovery Column to provide a third exit stream comprising STC and TCS but not appreciable amounts of HC1 or H₂.) The process of embodiment 23 wherein STC from the STC/TCS Separator Column is fed into a TCS Absorber Column, where the first vent gas is also fed into the TCS Absorber Column.

) A system comprising:

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor which produces a first vent gas comprising STC, TCS, HC1 and H₂, where the first vent gas optionally also includes DCS, where the Reactor optionally produces polysilicon from a feedstock comprising TCS;

b. a TCS Absorber Column in fluid communication with the Reactor, where the TCS Absorber Column receives the first vent gas or a portion thereof from the Reactor and separates H₂ from a second exit stream comprising STC and TCS and not containing appreciable amounts of H₂ or HC1; c. an STC/TCS Separator Column in fluid communication with the TCS Absorber, where the STC/TCS Separator Column receives the second exit stream or a fraction thereof comprising STC and TCS from the TCS Absorber; d. an STC Converter in fluid communication with the TCS Absorber Column, where the STC Converter receives a feed of H₂ and STC from the TCS Absorber, and generates a second vent gas comprising STC, TCS, DCS, HCl and H₂;

e. an HCl Absorber Column in fluid communication with the STC Converter, where the HCl Absorber Column receives the second vent gas from the STC Converter, and generates a mixture comprising STC, TCS and HCl that does not contain appreciable amounts of H₂; and f. an HCl Recovery Column in fluid communication with the HCl Absorber Column, where the HCl Recovery Column receives the mixture comprising STC, TCS and HCl that does not contain appreciable amounts of H₂, and generates a third exit stream comprising STC and TCS which does not contain appreciable amounts of HCl or H₂.

) A process comprising:

a. feeding H₂ and TCS into a Reactor to produce polysilicon and a first vent gas comprising at least some of the H₂; and

b. feeding some or all of the first vent gas and additional H₂ into an STC Converter to produce TCS and a second vent gas, the second vent gas comprising some of the H₂ that was fed into the Reactor.

) The process of embodiment 31 further comprising

feeding at least some of the H₂ from the second vent gas and TCS from the second vent gas into the Reactor to produce polysilicon.

) The process of embodiment 32 comprising feeding the first vent gas into an HCl Pipeline Reactor to remove at least most of the HCl from the first vent gas.) A system for polysilicon production, the system comprising:

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor, to produce polysilicon and a first vent gas comprising HCl and chlorosilanes;

b. an HCl treatment system to separate the HCl from the chlorosilanes present in the first vent gas, the HCl treatment system selected from

i. an HCl Pipeline Reactor, and

ii. a combination of a TCS Absorber Column and an HCl Stripper Column; c. an STC Converter to convert STC to a mixture of chlorosilanes; and the system optionally further comprising one or more of:

d. an HCl Absorber Column to separate hydrogen from chlorosilanes and HCl;

e. an HCl Recovery Column to separate HCl from chlorosilanes; and f. an STC/TCS Separator Column to separate STC from TCS.

) The system of embodiment 34 wherein the HCl treatment system is an HCl Pipeline Reactor comprising a catalyst to convert HCl and one or both of reactants DCS and TCS to one or both of products comprising TCS and STC.) The system of embodiment 35 further comprising a TCS Absorber Column to separate hydrogen from TCS and DCS.

) The system of embodiment 35 further comprising a TCS Absorber Column to pre- vaporize STC in hydrogen feed to the STC Converter.

) The system of embodiment 34 wherein the HCl treatment system is a TCS Absorber Column.

) The system of embodiment 34 wherein the HCl treatment system is an HCl Stripper Column.

) The system of embodiment 34 wherein the HCl treatment system is a combination of a TCS Absorber Column and an HCl Stripper Column.

) The system of embodiment 34 comprising an HCl Absorber Column which separates hydrogen recycle to the CVD reactor from STC.

) The system of embodiment 34 comprising an HCl Absorber Column which separates hydrogen recycle to the CVD reactor from STC and DCS.

) The system of embodiment 34 comprising an HCl Absorber Column which is operated at an overhead temperature ranging from -5°C to -80°C to separate hydrogen recycle to the CVD reactor from TCS, DCS, and STC.

) The system of embodiment 34 comprising an HCl Absorber Column which accepts a reflux which is a mixture of DCS and TCS.

) The system of embodiment 34 comprising an HCl Absorber Column which accepts a reflux which comprises TCS.

) The system of embodiment 34 comprising an HCl Absorber Column which accepts a reflux which comprises STC. ) The system of embodiment 34 comprising an HC1 Absorber Column which accepts a reflux which is a mixture of DCS, TCS, and STC.

) The system of embodiment 34 comprising a TCS/DCS Separator Column to separate TCS from DCS.

) The system of embodiment 34 further comprising a Silica Gel Bed to absorb boron species from a chlorosilane stream.

) The system of embodiment 34 further comprising a Commutation Reactor to produce TCS from a mixture of STC and DCS.

) The system of embodiment 34 further comprising an STC Absorber Column to separate hydrogen from STC.

) The system of embodiment 34 further comprising an STC Absorber Column to separate hydrogen from STC and DCS.

) The system of embodiment 34 comprising a combination of an STC Absorber Column (12) using either DCS and TCS or TCS only as reflux, and an HC1 Absorber Column using a mixture of STC, TCS, and DCS as reflux to remove HC1 and STC from ¾ recycle gas to the Reactor.

) The system of embodiment 34 further comprising an STC Absorber Column to pre-vaporize TCS in hydrogen recycle to the CVD reactor.

) The system of embodiment 34 further comprising an STC Converter Off-gas Scrubber Column to separate hydrogen recycle to the CVD reactor from TCS and DCS.

) The system of embodiment 34 further comprising an STC Converter Off-gas Scrubber Column in fluid communication with the HC1 Stripper Column.) The system of embodiment 34 further comprising a Carbon Absorption Bed to remove carbonaceous compounds, such as methyl chlorosilane and methane, from ¾ recycle to the CVD reactor.

) The system of embodiment 34 further comprising a Distillation Column to remove carbonaceous compounds, such as methyl chlorosilanes, from TCS recycle to the CVD reactor.

) The system of embodiment 34 which does not have a TCS Absorber Column which receives STC reflux. ) The system of embodiment 34 which does not contain two hydrogen recycle loops, each comprising a compressor and a means to separate chlorosilanes from hydrogen.

) The system of embodiment 34 which contains only a single unit or single set of units that separates hydrogen from chlorosilane(s).

) The system of embodiment 34 comprising a CVD Reactor in fluid

communication with a TCS Absorber Column, the TCS Absorber Column in fluid communication with an STC Converter, the STC Converter in fluid communication with an HC1 Absorber Column, the HC1 Absorber Column in fluid communication with an Compressor, the Compressor in fluid

communication with the CVD Reactor.

) The system of embodiment 34 comprising conduit whereby hydrogen which is supplied to the CVD reactor and collected in a first vent gas is fed into the STC reactor.

) The system of embodiment 34 comprising: [Based on Figure 1]

a. the Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor is in fluid communication with and provides an exit stream to an HC1 Pipeline Reactor;

b. the HC1 Pipeline Reactor is in fluid communication with and provides an exit stream to a TCS Absorber Column;

c. the TCS Absorber Column is in fluid communication with and provides an exit stream to both of an STC Converter and an STC/TCS Separator Column;

d. the STC Converter is in fluid communication with and provides an exit stream to the HC1 Absorber Column;

e. the HC1 Absorber Column is in fluid communication with and provides an exit stream to the HC1 Recovery Column;

f. the HC1 Recovery Column is in fluid communication with and provides an exit stream to the STC/TCS Separator Column; and

g. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to both of the TCS Absorber Column and the STC Converter.

) The system of embodiment 34 or 38 comprising: [Based on Figure 2] a. the Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor is in fluid communication with and provides an exit stream to a TCS Absorber Column;

b. the TCS Absorber Column is in fluid communication with and provides an exit stream to both of an STC Converter and an HC1 Stripper Column; c. the STC Converter is in fluid communication with and provides an exit stream to the HC1 Absorber Column;

d. the HC1 Absorber Column is in fluid communication with and provides an exit stream to the HC1 Recovery Column;

e. the HC1 Recovery Column is in fluid communication with and provides an exit stream to the STC/TCS Separator Column;

f. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to both of the TCS Absorber Column and the STC Converter; and

g. the HC1 Stripper Column is in fluid communication with and provides an exit stream to the TCS Absorber Column and to the STC/TCS Separator Column.

) The system of embodiment 34 or 38 comprising: [Based on Figure 3]

a. the Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor is in fluid communication with and provides an exit stream to a TCS Absorber Column;

f. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to each of the TCS Absorber Column, the STC Converter, and a TCS/DCS Separator Column and a Commutation Reactor; g. the TCS/DCS Separator Column is in fluid communication with and provides an exit stream to both of the HCl Absorber Column and a Silica Gel Bed;

h. the Silica Gel Bed is in fluid communication with and provides an exit stream to a Commutation Reactor;

i. the Commutation Reactor is in fluid communication with and provides an exit stream to the STC/TCS Separator Column;

j . the HCl Stripper Column is in fluid communication with and provides an exit stream to the TCS Absorber Column and to the STC/TCS Separator Column.

) The system of embodiment 34 or 38 comprising: [Based on Figure 4]

b. the TCS Absorber Column is in fluid communication with and provides an exit stream to both of an STC Converter and an HCl Stripper Column; c. the STC Converter is in fluid communication with and provides an exit stream to the HCl Absorber Column;

d. the HCl Absorber Column is in fluid communication with and provides an exit stream to the HCl Recovery Column;

e. the HCl Recovery Column is in fluid communication with and provides an exit stream to both of the STC/TCS Separator Column and the HCl Absorber Column;

f. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to each of the TCS Absorber Column, the STC Converter, the TCS/DCS Separator Column, and the Commutation Reactor;

g. the TCS/DCS Separator Column is in fluid communication with and provides an exit stream to a Silica Gel Bed;

h. the Silica Gel Bed (10) is in fluid communication with and provides an exit stream to a Commutation Reactor;

i. the Commutation Reactor is in fluid communication with and provides an exit stream to the STC/TCS Separator Column; j . the HCl Stripper Column is in fluid communication with and provides an exit stream to the TCS Absorber and to the STC/TCS Separator Column.) The system of embodiment 34 or 38 comprising: [Based on Figure 5]

a. the Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor is in fluid communication with and provides an exit stream to an HCl Pipeline Reactor;

b. the HCl Pipeline Reactor is in fluid communication with and provides an exit stream to a TCS Absorber Column;

d. the STC Converter is in fluid communication with and provides an exit stream to the HCl Absorber Column;

e. the HCl Absorber Column is in fluid communication with and provides an exit stream to both of the HCl Recovery Column and an STC Absorber Column;

f. the STC Absorber Column is in fluid communication with and provides an exit stream to the STC/TCS Separator Column;

g. the HCl Recovery Column is in fluid communication with and provides an exit stream to both of the STC/TCS Separator Column and the HCl Absorber Column; and

h. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to each of the TCS Absorber Column, the STC Converter, and the STC Absorber Column.

) The system of embodiment 34 or 38 comprising: [Based on Figure 6]

c. the TCS Absorber Column is in fluid communication with and provides an exit stream to both of the STC Converter and the STC/TCS Separator Column; d. the STC Converter is in fluid communication with and provides an exit stream to the HCl Absorber Column;

g. the HCl Recovery Column is in fluid communication with and provides an exit stream to both of the STC/TCS Separator Column and the HCl Absorber Column;

h. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to each of the TCS Absorber Column, the STC Converter, the TCS/DCS Separator Column, and the Commutation Reactor;

i. the TCS/DCS Separator Column is in fluid communication with and provides an exit stream to both of the STC Absorber Column and a Silica Gel Bed;

j. the Silica Gel Bed is in fluid communication with and provides an exit stream to a Commutation Reactor; and

k. the Commutation Reactor is in fluid communication with and provides an exit stream to the STC/TCS Separator Column.

) The system of embodiment 34 or 38 comprising: [Based on Figure 7]

b. the TCS Absorber Column is in fluid communication with and provides an exit stream to the STC Converter and an HCl Stripper Column;

c. the HCl Stripper Column is in fluid communication with and provides an exit stream to the STC/TCS Separator Column and the TCS Absorber Column;

d. the STC Converter is in fluid communication with and provides an exit stream to the HCl Absorber Column; e. the HC1 Absorber Column is in fluid communication with and provides an exit stream to both of the HC1 Recovery Column and an STC Absorber Column;

g. the HC1 Recovery Column is in fluid communication with and provides an exit stream to both of the STC/TCS Separator Column and the HC1 Absorber Column;

71) The system of embodiment 34 or 38 comprising: [Based on Figure 9]

b. the TCS Absorber Column is in fluid communication with and provides an exit stream to the STC Converter and an HC1 Stripper Column;

c. the HC1 Stripper Column is in fluid communication with and provides an exit stream to the STC/TCS Separator Column and the TCS Absorber Column;

d. the STC Converter is in fluid communication with and provides an exit stream to an STC Converter Off-gas Scrubber Column;

e. the STC Converter Off-gas Scrubber Column is in fluid communication with and provides an exit stream to and receives an exit stream from the HC1 Stripper Column, where the HC1 Stripper Column is also in fluid communication with and provides an exit stream to the STC/TCS Separator Column;

f. the STC Converter Off-gas Scrubber Column is in fluid communication with an provides an exit stream to the HC1 Absorber Column; g. the HC1 Absorber Column is in fluid communication with and provides an exit stream to the HC1 Recovery Column;

h. the HC1 Recovery Column is in fluid communication with and provides an exit stream to the HC1 Absorber Column and an exit stream to the STC/TCS Separator Column; and

i. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to each of the TCS Absorber Column, the STC Converter, and the STC Converter Off-gas Scrubber Column.

72) The system of embodiment 34 or 38 comprising: [Based on Figure 10]

a. a Reactor selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor is in fluid communication with and provides an exit stream to a TCS Absorber Column;

f. the STC Converter Off-gas Scrubber Column is in fluid communication with and provides an exit stream to the HC1 Absorber Column; g. the HC1 Absorber Column is in fluid communication with and provides an exit stream to the HC1 Recovery Column and an exit stream to a Carbon Absorption Bed (18); h. the HC1 Recovery Column is in fluid communication with and provides an exit stream to the HC1 Absorber Column and an exit stream to the STC/TCS Separator Column; and

i. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to each of the TCS Absorber Column, the STC Converter, the STC Converter Off-gas Scrubber Column, and optional distillation equipment.

73) The system of embodiment 34 or 38 comprising: [Based on Figure 11]

b. the HC1 Pipeline Reactor is in fluid communication with and provides an exit stream to a Refrigerated Decanter;

c. the Refrigerated Decanter is in fluid communication with and provides an exit stream to the STC Converter and the STC/TCS Separator Column; d. the STC Converter is in fluid communication with and provides an exit stream to an STC Converter Off-gas Scrubber Column;

e. the STC Converter Off-gas Scrubber Column is in fluid communication with and provides an exit stream to and receives an exit stream from an HC1 Stripper Column, where the HC1 Stripper Column is also in fluid communication with and provides an exit stream to the STC/TCS Separator Column;

f. the STC Converter Off-gas Scrubber Column is in fluid communication with and provides an exit stream to the HC1 Absorber Column; g. the HC1 Absorber Column is in fluid communication with and provides an exit stream to the HC1 Recovery Column;

i. the STC/TCS Separator Column is in fluid communication with and provides an exit stream to each of the STC Converter and the STC Converter Off-gas Scrubber Column.

41] Any of the various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, PCT application publications, foreign patents, foreign patent applications and non-patent publications referred to in this specification, are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

CLAIMS What is claimed is:

1. A process comprising:

a. in a Reactor (1), producing a first vent gas comprising silicon tetrachloride (STC), trichlorosilane (TCS), hydrogen chloride (HCl) and hydrogen (H₂); b. separating components of the first vent gas or a portion thereof to provide at least two separate exit streams, a first exit stream comprising at least 50% of the STC and at least 75% of the H₂ present in the first vent gas, and a second exit stream comprising at least 50% of the TCS and at least 50% of the DCS present in the first vent gas; and

c. feeding the first exit stream comprising STC and H₂ to an STC Converter (4 or 15) to provide a second vent gas comprising STC, TCS, DCS, HCl and H₂.

2. The process of claim 1 wherein the first vent gas is produced in the Reactor (1) to which is fed TCS and wherein is produced polysilicon.

3. The process of claim 1 wherein the first vent gas is treated to remove the HCl from other components of the first vent gas, to provide an HCl-depleted first vent gas which is a portion of the first vent gas.

4. The process of claim 1 wherein the separating comprises feeding the first vent gas or a portion thereof to a TCS Absorber Column (3).

5. The process of claim 4 wherein fresh STC is fed into the TCS Absorber Column (3).

6. The process of claim 1 wherein the second exit stream or a fraction thereof is fed into an STC/TCS Separator Column (7).

7. The process of claim 1 wherein the STC Converter (4) comprises metal silicide catalyst and is operated in a non-equilibrium mode.

8. The process of claim 1 wherein

a. the second exit stream is fed into an STC/TCS Separator Column (7); and b. a portion of the second vent gas comprising STC and TCS is also fed into the STC/TCS Separator Column (7).

9. The process of claim 1 wherein

a. the second exit stream is fed into an HCl Stripper Column (8) to provide an HCl-depleted mixture of TCS and DCS; b. the HCl-depleted mixture of TCS and DCS is fed into an STC/TCS Separator Column (7); and

c. a portion of the second vent gas comprising STC and TCS is also fed into the STC/TCS Separator Column (7).

10. A system comprising:

a. a Reactor (1) selected from a Chemical Vapor Deposition (CVD) Reactor and a Fluidized Bed (FB) Reactor, the Reactor (1) producing polysilicon and a vent gas comprising silicon tetrachloride (STC), trichlorosilane (TCS), hydrogen chloride (HC1) and hydrogen (H₂);

b. a TCS Absorber Column (3) in fluid communication with the Reactor (1), wherein the TCS Absorber Column (3) receives i) the first vent gas from the Reactor (1) or a portion thereof and ii) a fresh portion of STC, and wherein a first exit stream comprising at least 75% of the H₂ and optionally at least 50% of the STC present in the first vent gas, and a second exit stream comprising at least 50% of the TCS and optionally at least 50% of the DCS present in the first vent gas, both exit the TCS Absorber Column (3); and

c. an STC Converter (4 or 15) in fluid communication with the TCS

Absorber Column (3), where the STC Converter (4 or 15) receives the first exit stream from the TCS Absorber Column (3) and provides a second vent gas comprising STC, TCS, HC1 and H₂, and optionally DCS.

11. The system of claim 10 wherein an HC1 Pipeline Reactor (2) is located between, and is in fluid communication with each of the Reactor (1) and the TCS Absorber Column (3).

12. The system of claim 10 wherein an STC/TCS Separator Column (7) is in fluid communication with each of the STC Converter (4 or 15) and the TCS Absorber Column (3), where exit streams or fractions thereof from the STC Converter (4 or 15) and the TCS Absorber Column (3) are each fed into the STC/TCS Separator Column (7).

13. The system of claim 10 wherein an HC1 Stripper Column (8) is located between, and is in fluid communication with each of the TCS Absorber Column (3) and the STC/TCS Separator Column (7).

14. The system of claim 10 wherein the STC Converter (4 or 15) is in fluid communication with and provides the second vent gas to an HCl Absorber Column (5).

15. The system of claim 14 wherein the HCl Absorber Column (5) is in fluid communication with and provides HCl, STC and TCS, and optionally DCS, to an HCl Recovery Column (6), and the HCl Recovery Column (6) is in fluid communication with and provides STC and TCS, and optionally DCS, to the STC/TCS Separator Column (7).