WO2011124772A1 - Method for eliminating hydrogen halides in gaseous phase - Google Patents

Abstract

The present invention relates to a method of eliminating at least one hydrogen halide contained in a gaseous feedstock, comprising at least one step consisting in bringing the gaseous feedstock into contact with a material comprising at least one metal oxide under conditions for capturing the hydrogen halides in the form of a solid.

Description

 PROCESS FOR REMOVING GASEOUS PHASE HYDROGEN HALIDES

 The present invention relates to the field of the elimination of the halides in the gas phase, and more particularly to the hydrogen halides in the gas phase, that is to say in the combustion fumes, the synthesis gases, etc.

There are a number of gasification processes for solid fuels (eg thermal power plants) that produce a mixture of carbon monoxide (CO) and hydrogen (H ₂ ) which forms a synthesis gas. These fuels can be coal, coke, asphalt (obtained by deasphalting heavy oil cuts), biomass, or household waste.

 The hot gases leaving the gasification units are sent to exchangers with a water exchanger to produce steam which will drive a turbine to produce energy.

These gasification units can also be used to produce hydrogen. In this case, the synthesis gas is sent to a water gas reaction reactor ("water-gas shift" according to the English terminology).

 Another known technique also using a gasifier is the Integrated Gasification Combined Cycle (IGCC) technology.

 Whatever the origin and the use of these gases, they contain at the output of gasification units a certain number of impurities which will pose different problems:

 - at the level of the heat exchangers where they will be deposited and thus reduce heat exchanges,

 at the level of the catalysts used downstream of the gasification units,

 - corrosion of the devices.

These impurities are of various natures and with different contents depending on the load used in the supply of the gasification units. In particular, halides may be present in these gases. Of these halides, hydrogen halides are widespread. In gases, hydrogen chloride (HCl) seems to predominate whereas hydrogen bromide (HBr) seems to accumulate in the ashes. For example, the typical contents in bromine in the gases resulting from the incineration of household refuse are of the order of 30 to 200 mg / kg whereas for chlorine, the contents are of the order of 3 000 to 6 000 mg / kg. The typical HCI contents of the gases resulting from the gasification of coal are between 50 and 500 ppm.

 One of the most effective means of eliminating hydrogen halides is to wash the gas at the outlet of the gasifier with water and in particular water containing a base. Hydrogen halides dissolve in water and are eliminated. For this, the temperature of the water must be below 50 ° C. After purification, the synthesis gas at 50 ° C should be heated to 200 ° C to 300 ° C for use in the gas-to-water reaction or in a Fischer-Tropsch process. This method can be considered expensive from an energy point of view.

The same problems arise with the gases resulting from combustion and various calcinations and then used as gasification gases.

 It is therefore an object of the present invention to overcome one or more of the disadvantages of the prior art by proposing a simple and inexpensive method which makes it possible to eliminate the hydrogen halides present in the synthesis gases or in the gases coming from the combustion of solid material, liquid (coal, wood, straw, garbage ...).

 For this purpose, the present invention proposes a process for eliminating at least one hydrogen halide contained in a gaseous feedstock comprising at least one step of bringing the gaseous feedstock into contact with a material comprising at least one metal oxide under conditions allowing the capture of hydrogen halides in the form of a solid.

 According to one embodiment of the invention, the contact temperature of the gaseous feed with the material is greater than or equal to 200 ° C.

According to another embodiment of the invention, the gaseous feedstock is brought into contact with the material at a pressure of between 0.1 MPa and 20 MPa and a temperature of between 200 ° C. and 1500 ° C. According to one embodiment of the invention, the hydrogen halide is of general formula HX, in which H represents hydrogen and X is an element belonging to group 17 of the Mendeleev classification, chosen from chlorine, bromine, and iodine.

According to one embodiment of the invention, the metal oxide is of general formula A _m O _n , in which O represents oxygen and A is an element belonging to line 4 of the periodic table of the Mendeleyev classification, selected from calcium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, m and n being positive integers.

According to one embodiment of the invention, the method uses a metal oxide alone or a mixture of oxides of calcium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc .

According to one embodiment of the invention, the solid obtained during the bringing into contact is a halide of formula AX ₂ in the solid state.

According to another embodiment of the invention, the solid obtained during the contacting is a halide of formula AX in the solid state.

 According to one embodiment of the invention, the charge is derived from combustion fumes or synthesis gas.

 Other features and advantages of the invention will be better understood and will appear more clearly on reading the description given hereinafter with reference to the appended figures given by way of example:

 - Figure 1 is a schematic representation of an embodiment of the invention.

 - Figure 2 is a schematic representation of another embodiment of the invention.

 The present invention relates to a process for removing hydrogen halides from a feedstock containing hydrogen halides.

The hydrogen halides have the general formula HX, wherein H is hydrogen and X is an element belonging to group 17 of the Mendeleev classification, selected from fluorine, chlorine, bromine, and iodine. The process according to the invention comprises at least one step in which the charge containing the hydrogen halides is brought into contact with a material comprising at least one metal oxide under conditions allowing the capture of the hydrogen halides in the form of a solid.

 The metal oxide used in the context of the invention is of general formula

A _m O _n , in which O represents oxygen and A is an element belonging to line 4 of the periodic table of the Mendeleyev classification, chosen from calcium, vanadium, chromium, manganese, iron, cobalt , nickel, copper, zinc, m and n being positive integers. The contacting is carried out at temperatures greater than or equal to 200 ° C.

 At least a portion of the gaseous stream, containing the hydrogen halides, undergoes this step.

 According to another embodiment of the invention, the entire gas stream, containing the hydrogen halides, undergoes this step.

The principle of the invention is based on the reaction of phase transformations of the metal oxide A _m O _n. according to one of the following reactions given by way of example as a function of the stoichiometric coefficients of the oxide:

 - m <n

A _m O _n (s) + 2m HX (g) -> m AX ₂ (s) + m H ₂ 0 (g) + 0 ₂ (g) - m> n

A _m O _n (s) + m HX (g) -> m AX (s) + m H ₂ 0 (g) + 0 ₂ (g) n and m are positive integers, (s) means that the compound is found in the solid state, (g) means that the compound is in the gaseous state The purpose of this step is to capture all of the halogen in solid form.

To illustrate the invention, certain examples of solids are provided below but are in no way limiting of the invention: - Case where n = m = 1: then AO + 2 HX -> AX ₂ + H ₂ 0

with Ca = calcium, CaO (s) + 2 HCl (g) -> CaCl ₂ (s) + H ₂ O (g)

with V = vanadium, VO (s) + 2HCl (g) -> VCI ₂ (s) + H ₂ O (g)

with Mn = manganese, MnO (s) + 2HCl (g) -> MnCl ₂ (s) + H ₂ O (g)

with Fe = iron, FeO (s) + 2HCl (g) -> FeCl ₂ (s) + H ₂ O (g)

with Co = cobalt, CoO (s) + 2HCl (g) -> CoCl ₂ (s) + H ₂ O (g)

with Ni = nickel, NiO (s) + 2 HCl (g) -> NiCI ₂ (s) + H ₂ O (g)

with Cu = copper, CuO (s) + 2 HCl (g) -> CuCl ₂ (s) + H ₂ O (g)

with Zn = zinc, ZnO (s) + 2HCl (g) -> ZnCl ₂ (s) + H ₂ O (g)

 - where n> m:

with Cr = chromium, Cr ₂ O ₃ (s) + 6 HCl (g) -> 2 CrCl ₃ (s) + 3H ₂ O (g)

with Mn = manganese, MnO ₂ (s) + 2 HCl (g) -> MnCl ₂ (s) + H ₂ O (g) + 0.5 0 ₂ (g) with Mn = manganese, Mn ₂ O ₃ ( s) + 4 HCl (g) -> 2 MnCl ₂ (s) + 2H ₂ 0 (g) + 0.5 0 ₂ (g) with Mn = manganese, Mn ₃ 0 ₄ (s) + 6 HCl (g) ) -> 3 MnCl ₂ (s) + 3 H ₂ 0 (s) + 0.5 0 ₂ (g) with Fe = iron, Fe ₂ O ₃ (s) + 6 HCl (g) -> 2 FeCl ₃ (s) + 3H ₂ O (g)

with Fe = iron, Fe ₃ O ₄ (s) + 6 HCl (g) -> 3 FeCl ₂ (s) + 3H ₂ O (g) + 0.5 0 ₂ (g)

with Co = colbalt, Co ₃ 0 ₄ (s) + 6 HCl (g) -> 3 CoCl ₂ (s) + 3H ₂ O (g) + 0.5 0 ₂ (g)

 - where n <m:

with Cu = copper, Cu ₂ O (s) + 2 HCl (g) -> 2 CuCl (s) + H ₂ O (g)

The metal oxides can be in bulk form, that is to say in pure form, or mixed with each other. For example there may be cited calcium ferrate formula 2CaO.Fe ₂ 0 ₃ (also known as the formula Ca ₂ Fe ₂ 05), zinc ferrate formula ZnO.Fe ₂ 0 ₃ (also known in the formula Fe ₂ ZnO ₄ ), manganese ferrate of formula MnO.Fe ₂ O ₃ (also known as Fe ₂ MnO), delafossite of formula Cu ₂ O.Fe ₂ O ₃ (also known as formula Cu ₂ Fe ₂ O ₄ ). The preferred metal oxides in the context of the invention are copper (Cu), iron (FE), manganese (Mn), alone or e mixture, and in particular a mixture of copper and iron.

 The metal oxides may be supported on support materials such as silicas, or aluminas, or silica-aluminas, or any other type of solid support. Solid support materials such as natural or synthetic zeolites can be used in the context of the present invention. By way of example, mention may be made of faujasites, mordenites, zeolites X and Y .... The initial metal oxides may also be placed on support materials such as natural or synthetic clays, aluminates, silicates , titanates, spinel structures. The metal content of the initial metal oxides supported is between 0.01% by weight and 15% by weight, preferably between 0.01% by weight and 7% by weight, more preferably 0.01% and 5% by weight. .

The metal oxides can be on a mixing material. The mixing material comprises the support as well as compounds involved in the preparation of the support, such as, for example, binders, additives, diluents, blowing agents. By way of non-limiting example, lubricant additives may be used (stearic acid, graph, etc.), additives (starch, etc.), clay additives (montmorillonite, kaolinite, etc.) or any other known additive of the skilled person. When the initial metal oxide is in a mixing material, the mixing material preferably comprises more than 15% by weight of metal oxide, more preferably more than 50% by weight of metal oxide, more preferably more than 90% by weight. % by weight of metal oxide.

The metal oxides can be in solid or liquid form, in the form of powder, beads or extrudates. The invention does not require any particular restriction as to the shape of the metal oxide used.

The material comprising at least one metal oxide with which the charge is placed in contact can thus comprise between 0.01% by weight and 100% by weight of metal oxide. The feedstock of the process according to the invention contains between 0.0001% by volume and 100% by volume of hydrogen halides in gaseous form, preferably between 0.0001% by volume and 50% by volume of hydrogen halides, and more preferably preferential between 0.0001% by volume and 10% by volume of hydrogen halides. The feed may be a hydrocarbon partial redox effluent.

The conditions for carrying out the reaction between the metal oxide and the gaseous feedstock containing the hydrogen halides are chosen so as to keep the initial and final solid, derived from the capture of the halogen, in solid form. The temperature of use of the metal oxides will depend on the melting point of the solid halide, for example in the case of zinc oxide (ZnO), one must not exceed 280 ° C because the melting point of the chloride zinc (ZnC) is 283 ° C, in the case of cuprous oxide (CU2O), do not exceed 420 ° C because the melting point of copper (CuCl) chloride is 430 ° C, in the case of cupric oxide (CuO) must not exceed 610 ° C because the melting point of cupric chloride CuC is 620 ° C, in the case of manganese oxide (MnO, Μηθ2, Μη2θ3 and Μη ₃ θ ₄₎ , do not exceed 640 ° C because the melting point of the manganese chlotride (MnCl ₂ ) is 650 ° C, in the case of iron oxide (FeO or Fe30 ₄ ) it do not exceed 660 ° C because the melting point of iron (FeC) chloride is 670 ° C, in the case of calcium oxide (CaO), do not exceed 760 ° C as the calcium chloride (CaCb) fusion is 7 At 72 ° C, for nickel oxide (NiO), the temperature can reach 990 ° C because the melting point of nickel chloride (NiCl ₂ ) is 1001 ° C.

In general, the contact between the charge comprising hydrogen halides and the metal oxide can be carried out under the conditions of availability of the charge, at a pressure of between 0.1 MPa and 20 MPa, preferably between 0, 1 MPa and 7 MPa and a temperature of between 200 ° C and 1500 ° C, preferably between 500 ° C and 1100 ° C. In the case of hydrogen halides produced during the incineration, the contacting between the charge comprising the hydrogen halides and the initial metal oxide can be carried out at a pressure of between 0.1 MPa and 1 MPa. , and preferably at a pressure between 0.1 MPa and 0.3 MPa, and at a temperature between 200 ° C and 1500 ° C, and preferably at a temperature between 500 ° C and 1100 ° C. The treatment according to the process of the invention of other gaseous feeds such as gases originating from gasifiers can be carried out under pressure conditions of between 0.1 MPa and 20 MPa, and preferably at a pressure of between 0.1 MPa and 7 MPa, and temperatures between 200 ° C and 1500 ° C and preferably at temperatures between 500 ° C and 1100 ° C.

 The contact between the initial metal oxide of formula AxOy and the feed containing the hydrogen halides can be carried out in multiple ways.

This contacting can be carried out in a gas-solid or liquid-solid contacting column. The initial solid metal oxide may be attached to the column members, for example on the distributor trays or on the column packing, or used as such as a packing member of the column.

 One embodiment of the invention is illustrated in FIG. 1. The feedstock comprising the hydrogen halide arrives via the feed inlet conduit (2) and is brought into contact with the initial AmOn metal oxide in suspension. in a liquid solvent agitated by an agitator (10) contained in an enclosure (5). The purified gases and possibly part of the non-captured hydrogen halides are discharged through the conduit (4) from the top of the enclosure (5). The solvent containing the converted metal oxide is discharged through the conduit (3) from the bottom of the enclosure (5).

 In other embodiments of the invention the contacting can be carried out in beds.

 As illustrated in FIG. 2, the contacting can be carried out by scanning the effluent comprising hydrogen halides arriving via the feed inlet pipe (8) in a reactor (6) containing the metal oxide. AmOn disposed as fixed beds (7). The gaseous effluent "clean" or depleted of hydrogen halides is removed from the reactor (6) by the conduit (9) from the top of the reactor (6).

In another form of implementation of the method, it is possible to use the technique of the moving bed. In this case, the charge comprising the halides hydrogen is contacted in a reactor with the metal oxide in the form of powder or particles. The circulation of the charge makes it possible to drive the particles maintaining a homogeneous and disjoint distribution of the particles of metal oxides of formula A _m O _n .

The examples given below make it possible to illustrate the invention but are in no way limiting.

 Examples:

 Example 1 according to the invention

 This example was carried out in a fixed bed pilot unit. The reactor is filled with the adsorbent. A nitrogen bottle containing 0.00015 g of gaseous HCl / liter makes it possible to inject the hydrogen halide into the unit. 23 g of CuO are loaded into the reactor. This reactor is heated to 400 ° C., a flow rate of 25 ml / min of the nitrogen and HCI gas mixture is injected for 24 hours. At the exit of the pilot unit the line plunges into a tray filled with water in order to dissolve the gaseous HCI not retained by the adsorbent. The chlorine content of this water will then be determined by atomic spectroscopy. Knowing the amount of HCI injected and the amount dissolved in the water, it can be deduced the amount captured by the adsorbent.

 Under the conditions of Example 1, no chlorine was detected in the wash water of the gases after 24 hours of experimentation. The adsorbent retained all of the HCl injected at 400 ° C.

 Example 2 according to the invention

In the same pilot unit as Example 1, 33.5 g of FeO was charged to the reactor. The reactor was heated at 550 ° C for 24 hours. The same gas (nitrogen gas + HCI) is injected into the system as in Example 1. Release of the gas washing water is analyzed and the chlorine content is 10 ^"5 g.

 Iron oxide captured 99.8% of the total HCl injected into the system.

 Example 3 according to the invention

In the same pilot unit as Example 1, 32.7 g of an equi-weight mixture of CuO and FeO is charged to the reactor. The reactor is heated to 400 ° C. After 24 hours of experimentation, the analysis of the washing water makes it possible to verify that the adsorbent mixture made it possible to capture 100% of the HCl injected into the system.

 Example 4 according to the invention

In the same pilot unit as Example 1, 28.6 g of MnO was charged to the reactor. The reactor was heated at 550 ° C for 24 hours. The same gas (nitrogen + HCI gas) is injected into the system as in the previous examples. The exit gas wash water is analyzed and the chlorine content is 1, 2 × 10 ^-5 g.

 Manganese oxide captured 99.7% of the total HCl injected into the system.

 The above 4 examples illustrate the fact that the process according to the invention makes it possible to capture almost all of the hydrogen halide present in the initial charge.

The present invention should not be limited to the details given above and allows embodiments in many other forms without departing from the scope of the invention.

Claims

A method of removing at least one hydrogen halide contained in a gaseous feedstock comprising at least one step of contacting the gaseous feedstock with a material, comprising at least one metal oxide, under conditions, including pressure between 0.1 MPa and 20 MPa and a temperature between 200 ° C and 1500 ° C, allowing the capture of hydrogen halides in the form of a solid.  A process for removing at least one hydrogen halide according to claim 1, wherein the hydrogen halide is of the general formula HX, wherein H is hydrogen and X is a member of group 17 of the Mendeleev classification, selected from fluorine, chlorine, bromine, and iodine. 3. Process for removing at least one hydrogen halide according to one of claims 1 to 2, characterized in that the metal oxide is of general formula A _m O _n , wherein O represents oxygen and A is an element belonging to row 4 of the periodic table of the Mendeleev classification, selected from calcium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, m and n being positive integers. 4. Process for eliminating hydrogen halides according to one of claims 1 to 3, using a metal oxide alone or a mixture of oxides of calcium, vanadium, chromium, manganese, iron, cobalt, nickel , copper, and zinc. 5. Process for removing at least one hydrogen halide according to one of claims 1 to 4, wherein the solid obtained during the contacting is a halide of formula AX ₂ in the solid state. 6. Process for removing at least one hydrogen halide according to one of claims 1 to 5, wherein the solid obtained during the contacting is a halide of formula AX in the solid state. 7. A method of removing at least one hydrogen halide according to one of claims 1 to 6, wherein the feed is derived from combustion fumes or synthesis gas.