WO2008072392A1 - Method of treating discharge gas and apparatus therefor - Google Patents

Abstract

A single method of discharge gas treatment in which chlorine and sulfur hexafluoride can be efficiently removed without fail from a discharge gas without using a liquid alkali agent; and an apparatus for the method. The method of discharge gas treatment comprises purifying a discharge gas (F) containing at least one of chlorine and sulfur hexafluoride, and is characterized in that the discharge gas (F) is reacted at a high temperature with at least one of water vapor and oxygen and then washed with water and the discharge gas (F) washed with water is brought into contact with an alkali ion water (A) through gas/liquid contacting. Due to such constitution, the chlorine and sulfur hexafluoride contained in a discharge gas (F), which have conventionally been removed by respective separate methods, can be removed by a single method to a value not higher than a TLV without using an alkali chemical such as caustic soda.

Description

 Specification

 Exhaust gas treatment method and apparatus

 Technical field

 The present invention relates to an exhaust gas treatment method and apparatus for exhausting exhaust gas containing at least one of chlorine and sulfur hexafluoride as a safe gas.

 Background art

 [0002] Chlorine and sulfur hexafluoride used in the semiconductor manufacturing process are discharged as exhaust gas in a mixed state with other gases (for example, PFCs). Chlorine contained in such exhaust gas is extremely toxic to the human body, and sulfur hexafluoride has low toxicity to the human body, but its global warming potential (GWP) is tens of thousands of times that of CO. In addition to atmospheric life

 2

 Since the life is long, even if it is released into the atmosphere in a small amount, the effect is enormous. Therefore, conventionally used chlorine and sulfur hexafluoride are detoxified from the exhaust gas, and the amount of chlorine and sulfur hexafluoride etc. discharged into the atmosphere is determined by the TLV value [American Industrial Hygiene Experts Meeting Various technologies have been developed to reduce the concentration to less than the acceptable concentration for occupational health specified by (ACGIH).

 [0003] Here, as a method of removing such exhaust gas, an adsorption fixed type in which a component to be removed is adsorbed on a solid adsorbent, a heating decomposition type using a fuel flame, an electric heater, atmospheric pressure plasma, or the like. Many methods are used, such as a reaction decomposition method using a chemical reaction and a wet method using water or a chemical solution.

 [0004] Of these, when chlorine is the target of detoxification, absorption treatment is generally performed with a wet scrubber using alkaline chemicals such as caustic soda and ammonia as chemicals. On the other hand, when the object to be removed is sulfur hexafluoride, the fluorine-sulfur bond is broken by a combustion flame, an electric heater, or atmospheric pressure plasma, and this is reacted with water vapor, oxygen, etc. to fluorinate. Hydrogen and sulfur oxides (SOx) represented by sulfur dioxide are generated. The generated hydrogen fluoride and sulfur oxide are generally absorbed by a wet scrubber using an alkaline chemical solution.

[0005] Thus, different detoxification processes are used to detoxify chlorine and sulfur hexafluoride. However, since each abatement process uses alkaline chemicals such as caustic soda and ammonia, a high concentration and a large amount of alkaline chemicals must be prepared near the exhaust gas treatment device. Absent. However, in a tailored room environment where semiconductors are manufactured, there is a problem that it is very difficult to store alkaline chemicals because contamination of the indoor environment by alkaline chemicals must be avoided.

 [0006] Therefore, as a technique for efficiently removing sulfur oxides, which are decomposition products of chlorinated hexafluorosulfur and sulfur in exhaust gas, without using such an alkaline agent, as a chemical solution, A technique has been proposed in which exhaust gas is brought into gas-liquid contact with alkaline ionized water using a wet scrubber that uses alkaline ionized water (reducing electrolyzed water).

 [0007] According to powerful technology, chlorine, sulfur oxides, etc. in exhaust gas can be absorbed and detoxified without using alkaline chemicals such as caustic soda and ammonia as chemicals. Emissions into the atmosphere can be significantly reduced.

 Patent Document 1: Japanese Unexamined Patent Publication No. 2000-157830

 Disclosure of the invention

 Problems to be solved by the invention

[0008] However, when the concentration of chlorine or sulfur hexafluoride in the exhaust gas is high or the amount of exhaust gas discharged is large, a large amount of alkaline ionized water is required. The electrolyzed water production apparatus to be produced had to be enlarged, and there was a problem that the equipment cost and running cost increased significantly.

[0009] In addition, as described above, conventionally, chlorine and sulfur hexafluoride in exhaust gas have been detoxified by separate processes! However, a single exhaust gas treatment that can detoxify them together. Development of a method was desired.

 [0010] Therefore, the main subject of the present invention is a single exhaust gas treatment method capable of efficiently and reliably removing chlorine and sulfur hexafluoride from exhaust gas without using an alkaline chemical as the chemical. And to provide the device.

 Means for solving the problem

[0011] The invention described in claim 1 is an "exhaust gas treatment method for purifying exhaust gas (F) containing at least one of chlorine and sulfur hexafluoride, wherein the exhaust gas (F) is heated at a high temperature. With water vapor Alternatively, after reacting with at least one of oxygen, washing with water, the washed exhaust gas (F) is further brought into gas-liquid contact with the alkaline ionized water (A) ”.

 [0012] In the present invention, firstly, the exhaust gas (F) containing at least one of chlorine and sulfur hexafluoride is reacted with at least one of water vapor and oxygen at a high temperature, so that chlorine in the exhaust gas is converted into water. It is easily dissolved in salty hydrogen or chloric acid, and sulfur hexafluoride in the exhaust gas (F) is converted into hydrogen fluoride that is soluble in water and sulfur dioxide that is difficult to dissolve in neutral water. Converted. Therefore, by washing the exhaust gas (F) containing these products with water, 90% or more of hydrogen chloride or chlorine oxide in the exhaust gas (F), most of the hydrogen fluoride, and a part of sulfur dioxide are exhausted. (F) It can be removed from the inside.

 [0013] Since the washed exhaust gas (F) is further brought into gas-liquid contact with the alkaline ionized water (A), chlorine remaining in the exhaust gas (F) and components derived from this chlorine or soot are neutral. Almost all of the sulfur dioxide that is hardly soluble in water is absorbed by alkaline ionized water (A) and can be removed from the exhaust gas (F).

 [0014] The invention described in claim 2 relates to an exhaust gas treatment device (10) capable of carrying out the exhaust gas treatment method described in claim 1, wherein "exhaust gas (F) and steam or A reactor (12) for reacting at least one of oxygen at high temperature, a water scrubber (14) for washing exhaust gas (F) treated in the reactor (12), and an electrolysis for producing alkaline ionized water (A) Gas-liquid contact means for bringing the Al-ion reion water (A) produced by the electrolyzed water production device (16) into gas-liquid contact with the water production device (16) and the exhaust gas (F) washed with water scrubber (14) ( 18) ”is an exhaust gas treatment device (10).

[0015] The invention described in claim 3 is the exhaust gas treatment device (10) according to claim 2, wherein either of "reactor (12) force normal pressure plasma (P) or electric heater" is used. `` Or the combustion flame is used as a heat source '', and when either the atmospheric pressure plasma (P) or the electric heater is used as the heat source, only electricity and water are used in the exhaust gas (F). It can reliably remove chlorine and sulfur hexafluoride to a safe level. On the other hand, when a combustion flame is used as a heat source, by-product gases such as sulfur oxides are separated from substances generated by the decomposition of exhaust gas (F) when a combustion flame is generated by burning a fuel such as natural gas. Although this occurs, such a by-product gas can also be absorbed by the alkaline water (A) and removed from the exhaust gas (F). The invention's effect

 [0016] According to the present invention, chlorine and sulfur hexafluoride in exhaust gas, each of which has been conventionally detoxified by a separate method without using an alkaline chemical solution such as caustic soda, can be reduced to a TLV value or less by a single method. Can be reduced.

 [0017] In the treatment of exhaust gas, first, the exhaust gas is reacted with at least one of water vapor and oxygen at high temperature and then washed with water. In other words, most of the chlorine and sulfur hexafluoride in the exhaust gas are converted to substances that are soluble in water and then washed with water. At this stage, most of the chlorine or sulfur hexafluoride in the exhaust gas is removed. Can be removed. Therefore, the harmful components remaining in the exhaust gas can be almost completely removed from the exhaust gas simply by bringing a small amount of alkaline ionized water into gas-liquid contact with the washed exhaust gas. Therefore, the amount of alkaline ionized water can be remarkably reduced, and the exhaust gas treatment device (more specifically, the electrolyzed water producing device used for producing alkaline ionized water) can be made compact. In addition, even an exhaust gas containing a high concentration of chlorine or sulfur hexafluoride or a large volume of exhaust gas can be reliably removed.

 Brief Description of Drawings

FIG. 1 is a schematic view showing an exhaust gas treatment apparatus according to one embodiment of the present invention.

 FIG. 2 is a schematic view showing an exhaust gas treatment apparatus according to another embodiment of the present invention.

 Explanation of symbols

[0019] (10) ... Exhaust gas treatment equipment

 (12)… Reactor

 (12a) ... Reaction tube

 (12b)… Plasma jet torch

 (14)… Water scrubber

 (14b) ... scrubber body

 (14c) Spray nozzle

 (16)… Electrolyzed water production equipment

 (18)… Gas-liquid contact means

(24)… Exhaust gas supply piping (26) ... Exhaust fan

 (28)… Water pipe

 (28a) ... Branch water pipe

 (P)… Atmospheric pressure plasma

 (R) ... Internal space

 BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, the present invention will be described in detail according to the illustrated embodiments. FIG. 1 is a schematic view showing one embodiment of an exhaust gas treatment apparatus (10) for carrying out the exhaust gas treatment method of the present invention. As shown in this figure, the exhaust gas treatment device (10) of this example is roughly composed of a reactor (12), a water scrubber (14), an electrolyzed water production device (16), and a gas-liquid contact means (18). Has been.

 [0021] The reaction furnace (12) is for reacting the exhaust gas (F) containing at least one of chlorine or sulfur hexafluoride, such as semiconductor manufacturing processes, with water vapor or oxygen at a high temperature. And a reaction tube (12a) and a plasma jet torch (12b). Here, the temperature condition for reacting the exhaust gas (F) with water vapor or oxygen is preferably a high temperature of 1000 ° C or higher. If the temperature conditions are strong, the bond between fluorine and sulfur in sulfur hexafluoride can be reliably broken, and even if the exhaust gas (F) contains other PFCs such as CF,

 2 6

 This is because most of them can be pyrolyzed. If the exhaust gas (F) contains CF, which is difficult to dissociate, PFCs have a high temperature of at least about 1,400 to 1,500 ° C.

 Four

 Necessary. The upper limit of the temperature condition depends on the heat resistance of the material constituting the reactor (12).

 [0022] The reaction cylinder (12a) is a straight pipe member formed of a refractory material such as castable, having an internal space (R), and having both ends open. In this embodiment, the reaction cylinder (12a) is erected on a water tank (20) for storing water, and an atmospheric pressure plasma (P) serving as a heat source is placed at the upper end of the reaction cylinder (12a). A plasma jet torch (12b) for generating water is attached so as to close the opening. In addition, one end of an exhaust gas supply pipe (24) for supplying exhaust gas (F) and water vapor or oxygen toward the internal space (R) of the reaction cylinder (12a) is connected to the upper part of the reaction cylinder (12a). It has been.

[0023] Here, the plasma jet torch (12b) is an anode composed of a nozzle and the anode. A plasma jet outlet hole cap at the tip of the anode is provided by applying a discharge voltage between the anode and the force sword and feeding a working gas such as nitrogen into the anode. Also, high temperature atmospheric pressure plasma (P) is ejected.

 [0024] The water scrubber (14) is for washing the exhaust gas (F) treated in the reaction furnace (12) with water, and is provided with an exhaust gas inlet (14a) at the lower end. A straight pipe type scrubber body (14b) through which exhaust gas (F) flows upward, and a downward spray that injects water downward and upward so that the exhaust gas (F) flows in the opposite direction. It consists of a nozzle (14c).

 [0025] This water scrubber (14) is also erected on the water tank (20) in the same manner as the reaction tube (12a), so that the water sprayed from the spray nozzle (14c) is sent to the water tank (20). It has become. A gas-liquid contact means (18), which will be described later, is attached to the upper part of the scrubber body (14b), and the treated exhaust gas (F) is discharged into the atmosphere at the top outlet of the gas-liquid contact means (18). Connected to the exhaust fan (26) that discharges into the interior.

 The electrolyzed water production apparatus (16) is an apparatus for producing alkaline ionized water (A) having an alkaline pH of 11 or more and an acid-reduction potential of −800 mV or less, and a permselective membrane (for example, a positive permeable membrane). It has a reaction vessel (not shown) in which a positive electrode having Pt (platinum) isotropic force and a negative electrode having Pt isotropic force are opposed to each other via ion permeation). Alkaline ionized water (A) is produced by supplying raw water to this reaction tank and supplying power to each electrode.

 [0027] In this example, as raw water for producing alkaline ionized water (A), brine having a pH of about 4 to about LO is used as it is. Here, “boiled water” refers to water that can easily be obtained from the wells such as tap water, well water, and industrial water, and usually contains impurity ions such as sodium and potassium. By using such brine as the raw water, the raw water can be secured and supplied to the electrolyzed water production device (16) easily and simply. The exhaust gas treatment device (10) of this example is provided with a water pipe (28) having one end connected to a city water supply such as water supply or well water and the other end connected to a spray nozzle (14c). The brine is supplied to the electrolyzed water production device (16) through the branch water pipe (28a) branched from the water pipe (28).

[0028] The gas-liquid contact means (18) is provided in the upper part (downstream of the exhaust gas (F) flow direction) in the scrubber body (14b), and is manufactured by the exhaust gas (F) and the electrolyzed water production device (16). Gas and liquid with alkaline ionized water (A) It is for making it contact, and has a porous body filling layer (18a) and an alkali ion water dropping nozzle (18b).

 [0029] The porous material filling layer (18a) is filled with a porous material (30) composed of activated carbon having a fine mesh pores, porous alumina, or hydrophilic sponge having open cells. It is a layer constructed as follows. This porous material packed bed (18a) is attached so that the exhaust gas (F) can be divided through the internal space of the scrubber body (14b), and the alkaline ionized water dripping nozzle (18b) force is also provided. The dropped alkaline ionized water (A) stays in the porous material packed bed (18a) for a certain period. For this reason, when the exhaust gas (F) passes through the porous material packed bed (18a), the alkaline ionized water (A) contained in the micropores of the porous material (30) and the exhaust gas (F) are in a wide contact area. Can be efficiently brought into gas-liquid contact.

 [0030] The alkaline ionized water dropping nozzle (18b) is provided above the porous body packed layer (18a) and drops alkaline ionized water (A) so as to face the exhaust gas (F) flow direction. The nozzle body (32) is connected to a supply pipe (34) for supplying alkaline ionized water (A) produced by the electrolyzed water production apparatus (16) to the nozzle body (32).

 In this example, the force shown in the case where the gas-liquid contact means (18) is composed of the porous material packed layer (18a) and the alkali ion water dropping nozzle (18b) is shown in FIG. In this way, instead of the porous material packed bed (18a), a porous plate (36a) that divides the internal space of the scrubber body (14b) is attached, and the size of the pores of the porous plate (36a) and the amount of passing air are balanced. In addition, a bubbling tank (36) for storing alkali ion water (A) dropped from the alkali ion water dropping nozzle (18b) may be provided on the upper surface of the porous plate (36a). Although not shown in the drawing, as with the water scrubber (14), only a downward spray nozzle that injects alkaline ionized water (A) with an upward force so as to oppose the exhaust gas (F) flow direction is provided. Liquid contact means (18) may be used. However, as described above, the gas-liquid contact means (18) is composed of the porous material packed layer (18a) or the publishing tank (36) and the alkaline ionized water dropping nozzle (18b), so that a small amount of alkaline ionized water is used. (A) Even if the amount used, the exhaust gas (F) and the alkaline ionized water (A) can be reliably brought into gas-liquid contact.

Next, a method for removing chlorine and sulfur hexafluoride in the exhaust gas (F) using the exhaust gas treatment device (10) configured as described above will be described. [0033] First, the power source (not shown) of the exhaust gas treatment device (10) is turned on to operate the plasma jet torch (12b), and the atmospheric pressure plasma (12a) becomes a heat source in the reaction tube (12a). P) is ejected.

 [0034] Subsequently, when the temperature of the internal space (R) of the reaction tube (12a) becomes a high temperature atmosphere of 1000 ° C or higher due to the heat of the atmospheric pressure plasma (P), the exhaust fan (26) is operated to Exhaust gas (F) and water vapor or oxygen are supplied to the internal space (R) of the reaction tube (12a) through the feed pipe (24). Then, in the reaction tube (12a), chlorine in the exhaust gas (F) dissolves in salty hydrogen or chlorine oxide, which is easily dissolved in water, and sulfur hexafluoride in the exhaust gas (F) dissolves in water. It is converted into hydrogen fluoride and disulfur disulfide, which are not easily dissolved by neutral water.

 [0035] Here, the method of adding water vapor or oxygen to the internal space (R) of the reaction tube (12a) together with the exhaust gas (F) is (a) water vapor or oxygen adjusted in a separate line from the exhaust gas (F). (B) The exhaust gas (F) is mixed and supplied to the exhaust gas supply pipe (24). (B) The exhaust gas (F) is washed with a water scrubber (not shown) to remove water-soluble components and dust. In addition, water is supplied to the exhaust gas (F) and the exhaust gas (F) containing this water is supplied to the internal space (R) of the reaction tube (12a) (via the exhaust gas supply pipe (24)). It may be a method. However, if the exhaust gas (F) is previously washed with a water scrubber and given to the reaction tube (12a) as in (b), the exhaust gas (F) introduced into the reaction tube (12a) Since water-soluble components and dust are removed, troubles caused by dust and the like can be prevented during the subsequent detoxification treatment.

 [0036] Next, the exhaust gas (F) treated in the internal space (R) of the reaction tube (12a) is given to the water scrubber (14) by the negative pressure generated by the operation of the exhaust fan (26). Water is injected into the exhaust gas (F) from the downward spray nozzle (14c). Then, more than 90% of the chlorine-derived components (specifically, salt-hydrogen or chlorate) converted in the reactor (12), and most of the hydrogen fluoride among the components derived from sulfur hexafluoride. And a part of sulfur dioxide is absorbed by water and removed from the exhaust gas (F). Specifically, a plasma jet torch (12b) using a small power source with an output of less than 15 kW is used, and exhaust gas (F) for a total flow rate of 100 liters Z, including 500 cc of chlorine and 500 cc of sulfur hexafluoride. When treated, the concentration of chlorine and sulfur hexafluoride-derived components in the exhaust gas (F) has been reduced to about lOOppm at the stage when the water scrubber (14) has been washed.

[0037] Subsequently, the exhaust gas (F) washed with the water scrubber (14) passes through the porous body packed bed (18a). At that time, it comes into gas-liquid contact with alkaline ionized water (A). Then, chlorine remaining in the exhaust gas (F) or components derived from it (for example, chloric acid) etc. and neutral water, which is difficult to dissolve in neutral water, is absorbed by alkaline ionized water (A), Most of these exhaust gases (F) are removed. Specifically, chlorine that remained at about lOOppm after passing through the water scrubber (14) was reduced to about 0.1 ppm, and that from about 6 litters that remained at about lOOppm after passing through the water scrubber (14) was reduced to 0. It can be reduced to about 2ppm.

[0038] Thus, according to the exhaust gas treatment device (10) and the exhaust gas treatment method of the present embodiment, exhaust gas (F) that has been conventionally detoxified by separate methods without using an alkaline agent such as caustic soda. Chlorine and sulfur hexafluoride can be reduced below the TLV value by a single method.

 [0039] In the treatment of the exhaust gas (F), first, the exhaust gas (F) is reacted with at least one of water vapor or oxygen at a high temperature and then washed with water, that is, the chlorine in the exhaust gas (F). Futsui 易 Most of the sulfur can be easily dissolved in water, converted into substances, and then washed with water. At this stage, most of the chlorine or sulfur hexafluoride in the exhaust gas (F) is removed. be able to. Therefore, after that, just by bringing a small amount of alkaline ionized water (A) into gas-liquid contact with the washed exhaust gas (F), harmful components remaining in the exhaust gas (F) can be removed almost completely. it can. Therefore, the amount of alkali ion water (A) can be significantly reduced, and the exhaust gas treatment device (10) (more specifically, the electrolyzed water production device (16) used for the production of alkali ion water (A)). Can be made compact. Further, even if the exhaust gas (F) containing a high concentration of chlorine or sulfur hexafluoride is a large-capacity exhaust gas (F), the detoxification treatment can be reliably performed.

 [0040] Although the gas-liquid contact means (18) is incorporated in the water scrubber (14) in the present embodiment, the gas-liquid contact means (18) is independent of the water scrubber (14). It may be provided as a separate item.

[0041] Further, in this embodiment, a case where atmospheric pressure plasma (P) is used as a heat source is shown. However, as long as the internal space (R) of the reaction tube (12a) can be in a high temperature atmosphere, This heat source may be any type, for example, an electric heater or a combustion flame generated by burning fuel such as natural gas. If atmospheric pressure plasma (P) or an electric heater is used as the heat source, chlorine and sulfur hexafluoride in the exhaust gas (F) can be safely removed using only electricity and water. Can be reliably removed to a certain level. On the other hand, when a combustion flame is used as a heat source, when a combustion flame is generated by burning a fuel such as natural gas, sulfur oxides are separated from the substances generated by the decomposition of exhaust gas (F). The force generated by by-products such as such by-products can be absorbed by the alkali ion water (A) and removed from the exhaust gas (F).

Claims

The scope of the claims  [1] An exhaust gas treatment method for purifying exhaust gas containing at least one of chlorine and sulfur hexafluoride,  An exhaust gas treatment method in which the exhaust gas is reacted with at least one of water vapor or oxygen at a high temperature, then washed with water, and the washed exhaust gas is further brought into gas-liquid contact with alkaline ionized water.  [2] A reaction furnace for reacting exhaust gas with at least one of water vapor or oxygen at high temperature, a water scrubber for washing exhaust gas treated in the reaction furnace,  Electrolyzed water production apparatus for producing alkaline ionized water;  An exhaust gas treatment apparatus comprising gas-liquid contact means for bringing the alkaline water produced by the electrolyzed water production apparatus into gas-liquid contact with the exhaust gas washed with the water scrubber. [3] The exhaust gas treatment apparatus according to claim 2, wherein the reaction furnace uses either a normal pressure plasma or an electric heater, or is! / Soot uses a combustion flame as a heat source.