WO2008059883A1 - Hydrogen purification/collection method and hydrogen purification/collection facility - Google Patents

Abstract

Disclosed are a hydrogen purification/collection method and a facility for the method, which can be connected to a conversion facility for producing trichlorosilane and can purify and collect hydrogen contained in a gas generated by a conversion reaction with efficiency and enables to reuse the hydrogen. Specifically disclosed are a method and a facility for purification/collection of hydrogen, which are characterized in that a mixed gas produced by a conversion reaction for producing trichlorosilane is passed through an active carbon-filled layer to cause the adsorption of a chlorosilane and hydrogen chloride onto the active carbon, thereby separating the chlorosilane and hydrogen chloride from the gas. Preferably, the active carbon-filled layer is formed in a two stage structure composed of a first-stage active carbon-filled layer for adsorbing primarily a chlorosilane thereon and a second-stage active carbon-filled layer for adsorbing primarily hydrogen chloride, and the mixed gas is passed through the first-stage active carbon-filled layer and the second-stage active carbon-filled layer successively, thereby separating the chlorosilane and hydrogen chloride stepwisely.

Description

 Specification

 Hydrogen purification recovery method and hydrogen purification recovery equipment

 Technical field

 [0001] The present invention relates to, for example, a hydrogen purification and recovery method that is connected to a conversion facility that generates trichlorosilane, and that can efficiently purify and recover hydrogen contained in the product gas of the conversion reaction and reuse it. Regarding equipment.

 This application (May 2006, November 14, 2006, Japanese Patent Application No. 2006—308476, filed in Japan, October 24, 2007, Japanese Patent Application No. 2007—276565, filed in Japan The content of this is incorporated herein by reference.

 Background art

 High-purity polycrystalline silicon includes, for example, trichlorosilane (SiHCl: TCS) and hydrogen

 Three

 Is produced by the hydrogen reduction reaction of trichlorosilane represented by the following formula (1) and the thermal decomposition reaction of trichlorosilane represented by the following formula (2).

 SiHCl + H → Si + 3HC1… hi)

 3 2

 4SiHCl → Si + 3SiCl + 2H (2)

 3 4 2…

 [0003] Gases discharged from the above-mentioned formation reaction of polycrystalline silicon include unreacted trichlorosilane and hydrogen, as well as by-produced hydrogen chloride and chlorosilanes such as tetrachlorosilane, dichlorosilane, and hexachlorodisilane. . These chlorosilanes are separated by distillation stepwise according to the boiling point and reused as necessary.

[0004] For example, trichlorosilane can be obtained by a hydrogenation conversion reaction represented by the following formula (3) using tetrachlorosilane recovered by distillation separation from the exhaust gas of the production reaction as a raw material

. Chlorosilanes such as trichlorosilane and tetrachlorosilane contained in the gas produced in the conversion reaction are recovered by cooling and aggregation, and the trichlorosilane is reused as a raw material for producing the polycrystalline silicon.

 SiCl + H → SiHCl + HC1 (3)

 4 2 3

[0005] Since the product gas contains a large amount of unreacted hydrogen, after the chlorosilanes are condensed and separated, the hydrogen in the mixed gas is recovered and converted as a raw material for the conversion reaction. If it is returned to the furnace and reused, the use efficiency of hydrogen can be increased and the cost can be greatly reduced.

[0006] However, the product gas contains hydrogen chloride, and when used as a raw material for the conversion reaction in a state containing hydrogen chloride, there is a problem that the conversion reaction is hindered. In order to recover and reuse hydrogen from wastewater, it is necessary to efficiently remove hydrogen chloride contained in the product gas.

 [0007] As a conventional method for removing hydrogen chloride, for example, a treatment method shown in FIG. 3 is known. In this method, first, the reaction product gas of the converter 1 is led to the cooler 2 to be cooled, the chlorosilans are condensed and collected, and removed from the product gas! /, A mixed gas of hydrogen chloride and hydrogen To. Next, hydrogen chloride is removed by passing a mixed gas of hydrogen chloride and hydrogen through a neutralization tower 3 in which an aqueous solution of caustic soda circulates. Hydrogen chloride and uncondensed silanes contained in the mixed gas react with caustic soda in the neutralization tower 3 to produce sodium chloride and sodium silicate and deposit on the bottom of the tower. To remove.

 On the other hand, the mixed gas in which hydrogen remains passes through the neutralization tower 3 and is introduced into the drying tower 4. The drying tower 4 is filled with zeolite, and is dried while the hydrogen-containing gas passes through the tower. The dried hydrogen is returned to the evaporator 5, mixed with the supplied hydrogen and the supplied STC, introduced into the conversion furnace 1, and recycled (see Patent Document 1).

 Patent Document 1: Japanese Patent Laid-Open No. 48-40625 (Page 4, upper right column, Fig. 1)

 Disclosure of the invention

 Problems to be solved by the invention

In the conventional hydrogen recovery technology shown in FIG. 3, hydrogen chloride in the reaction product gas is converted to sodium chloride and removed, so that it is treated as waste without being effectively used. Processing costs increase. Also, the product gas extracted from the converter is cooled to a very low temperature, and the ability to separate condensed chlorosilanes. Even if cooled to a very low temperature, uncondensed black silanes remain in the product gas, thus removing hydrogen chloride. For this reason, when this is neutralized, the uncondensed chlorosilanes are also neutralized and become waste, which poses a problem that chlorosilanes cannot be used effectively. Furthermore, there is a disadvantage that a lot of caustic soda is consumed as a neutralizing agent. [0010] The present invention solves the above-described problems in conventional hydrogen recovery technology, and efficiently removes hydrogen chloride and chlorosilanes from a gas containing chlorosilanes and hydrogen chloride together with hydrogen, for example, a product gas of a converter. Provide a hydrogen purification and recovery method and equipment that separates and removes and recovers purified hydrogen gas that can be reused for the conversion reaction, and separates hydrogen chloride and chlorosilanes in a form that can be effectively used to prevent waste loss.

 Means for solving the problem

 [0011] The present invention relates to a method for purifying and recovering hydrogen that has solved the above problems by having the configuration shown in the following [1] to [5].

 [1] A hydrogen purification method in which a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen is passed through an activated carbon packed bed, and the chlorosilanes and hydrogen chloride are adsorbed on the activated carbon and separated from the gas.

 [2] The mixed gas generated in the conversion reaction in which tetrachlorosilane reacts with hydrogen to produce trichlorosilane is passed through the activated carbon packed bed, and chlorosilanes and hydrogen chloride are adsorbed on the activated carbon and separated from the gas. [1] The hydrogen purification and recovery method of [1].

 [3] It is formed in two stages: a pre-stage activated carbon packed bed that mainly adsorbs chlorosilanes and a post-stage activated carbon packed bed that mainly adsorbs hydrogen chloride, and the mixed gas is applied to the pre-stage activated carbon packed bed and the post-stage activated carbon packed bed. The method for purifying and recovering hydrogen according to the above [1] or [2], wherein the chlorosilanes and hydrogen chloride are separated stepwise by passing continuously.

[0012] The present invention relates to a hydrogen purification and recovery facility that has solved the above-described problems by having the configurations shown in the following [4] to [6].

 [4] An adsorption device having an activated carbon packed bed that adsorbs chlorosilanes and hydrogen chloride, and a pipe for introducing a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen to the adsorption device. Hydrogen purification and recovery equipment.

 [5] An adsorption device having a pre-stage activated carbon packed bed mainly adsorbing chlorosilanes and a post-stage activated carbon packed bed mainly adsorbing hydrogen chloride, and introducing a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen to the adsorber The hydrogen purification and recovery equipment according to [4] above, further comprising a pipe line that flows through the pre-stage activated carbon packed bed and the post-stage activated carbon packed bed.

[6] Contact with a conversion facility that reacts tetrachlorosilane with hydrogen to produce trichlorosilane. The above-mentioned [4] or [5], further comprising a circulation pipe for introducing the mixed gas generated in the conversion reaction to the adsorption device and returning the purified hydrogen via the adsorption device to the conversion equipment. Hydrogen purification and recovery equipment.

 The invention's effect

 [0013] According to the method of [1] and the equipment of [4] above, a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen is passed through the activated carbon packed bed, and the chlorosilanes and hydrogen chloride are adsorbed on the activated carbon. And purified hydrogen gas containing almost no chlorosilanes and hydrogen chloride can be recovered. In addition, chlorosilanes and hydrogen chloride adsorbed on activated carbon can be recovered by a desorption method such as passing hydrogen gas under heating to activated carbon, so there is no waste loss.

 [0014] According to the method of [3] and the equipment of [5] above, the activated carbon packed bed is formed in two stages, chlorosilanes are mainly adsorbed and separated in the former stage, and hydrogen chloride is mainly adsorbed and separated in the latter stage. Because

It is excellent in the separation effect of chlorosilanes and hydrogen chloride, and a purified hydrogen gas substantially free of chlorosilanes and hydrogen chloride can be obtained.

[0015] According to the method of [2] and the equipment of [6], the purification is performed by removing chlorosilanes and hydrogen chloride from the mixed gas generated in the conversion reaction in which tetrachlorosilane and hydrogen are reacted to generate trichlorosilane. Hydrogen gas can be recovered efficiently and recycled as part of the raw material for the conversion reaction. Thereby, raw material cost can be reduced.

 [0016] As described above, according to the hydrogen purification and recovery method and the hydrogen purification and recovery facility according to the present invention, the reaction product gas generated in the conversion reaction to trichlorosilane is passed through activated carbon to adsorb hydrogen chloride and chlorosilanes. Therefore, after adsorption, it can be desorbed and recovered, and hydrogen chloride that has been discarded in the past can be effectively reused. In addition, traditionally used as a neutralizing agent, it has been necessary to use caustic soda.

[0017] Further, conventionally, the mixed gas is cooled to a very low temperature to condense and separate chlorosilanes and neutralize them. However, since unseparated chlorosilanes remain, avoid this loss of waste. Force S can not. On the other hand, since the chlorosilanes adsorbed on the activated carbon can be desorbed and recovered in the method and equipment of the present invention, it is necessary to cool the mixed gas to a very low temperature and to separate it by condensation, No disposal loss occurs. Brief Description of Drawings

 FIG. 1 is an overall equipment configuration diagram including a piping configuration showing a first embodiment of the method for hydrogen purification and recovery according to the present invention.

 FIG. 2 is an overall equipment configuration diagram including a piping configuration showing a second embodiment of the method and equipment for hydrogen purification and recovery according to the present invention.

 FIG. 3 is a diagram of the entire equipment configuration including piping configuration showing a conventional example of equipment for hydrogen purification and recovery.

 Explanation of symbols

 [0019] 1 · · · Conversion furnace, 7 · · Cooler, 8 · · · Activated carbon packed bed, 8Α · · · Previous activated carbon packed bed, 8Β · · · Post activated carbon packed bed, 9, 29 · · Adsorption Tower (adsorber), 10 ··· second cooler, 11 ··· circulation pipe.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be specifically described based on embodiments. An example of a hydrogen purification / recovery system (method or facility) according to the present invention is shown in FIGS. The illustrated embodiment is an example in which the hydrogen purification and recovery system of the present invention is applied to a conversion facility for generating trichlorosilane by reaction of tetrachlorosilane and hydrogen.

[0021] [Conversion equipment]

 In the illustrated example, a tetrachlorosilane evaporator 5 and a conversion furnace 1 are provided in a conversion facility for generating trichlorosilane. Raw material hydrogen and silicon tetrachloride (STC) are introduced into an evaporator 5, and a raw material gas mixed with these is introduced into a converter 1. Converter 1 is set to an in-furnace temperature of about 800 ° C to about 1300 ° C, and hydrogen and silicon tetrachloride react to produce trichlorosilane, a small amount of dichlorosilane, hexachlorodisilane, etc., and these are mixed. Gas flows out of converter 1. This mixed gas includes, for example, about 2% to about 13% of produced trichlorosilane, about 2% to about 13% of by-produced hydrogen chloride, about 14% to about 60% of unreacted silicon tetrachloride, about hydrogen 20% to about 78% included!

[0022] [Condensation step]

A cooler 7 is connected to the converter 1, and a mixed gas (about 600 ° C. to about 1100 ° C.) generated in the converter 1 is introduced into the cooler 7, and about 50 ° C. to about 50 ° C. After cooling to ° C, chlorosilanes in the gas are condensed and collected, and sent to a distillation process (not shown) to collect chlorosilanes. It is done.

 [0023] Although most of the chlorosilanes are separated from the mixed gas in the condensation step, the mixed gas still contains uncondensed chlorosilanes, hydrogen chloride, and a large amount of hydrogen. This mixed gas is introduced into a hydrogen purification and recovery facility, where hydrogen chloride and uncondensed chlorosilan are separated and the purified hydrogen gas is recovered.

 [Hydrogen purification and recovery equipment]

 The hydrogen purification and recovery equipment includes an adsorption device (adsorption tower) 9 having an activated carbon packed bed 8 and a circulation path 11 from the adsorption tower 9 to the evaporator 5 of the conversion equipment. Further, the hydrogen purification and recovery equipment shown in the figure includes a pipe for introducing desorption gas into the adsorption tower 9, a second cooler 10, a pipe from the adsorption tower 9 through the second cooler 10, and an adsorption tower 9 Desorption means comprising heating means (not shown) is provided.

 [Adsorption process]

 The adsorption tower 9 of the hydrogen purification and recovery facility is connected to the cooler 7, and the mixed gas that has passed through the cooler 7 is introduced into the adsorption tower 9. An activated carbon packed bed 8 is formed inside the adsorption tower 9. This activated carbon may be a commonly used one. The adsorption rates of chlorosilanes, hydrogen chloride, and hydrogen on activated carbon are in the order of chlorosilanes> hydrogen chloride> hydrogen, and the adsorption rate of hydrogen is low.

 [0026] Therefore, when the mixed gas is passed through the adsorption tower 9, the chlorosilanes and hydrogen chloride in the mixed gas are adsorbed on the activated carbon and separated from the gas while the mixed gas passes through the activated carbon packed bed 8. Is done. On the other hand, since the adsorption rate of hydrogen is low, most of the force adsorbed on the activated carbon passes through the activated carbon packed bed 8, so that purified hydrogen gas containing no chlorosilanes and hydrogen chloride can be obtained.

 [0027] Since general activated carbon is in a high concentration saturated state, the adsorption amount of chlorosilanes is about 50 g of chlorosilanes per 100 g of activated carbon, and the adsorption amount of hydrogen chloride is about 6 g of hydrogen chloride per 100 g of activated carbon. According to the amount of chlorosilanes and hydrogen chloride contained in the mixed gas and the amount of mixed gas introduced, the capacity of the activated carbon packed bed 8 may be determined so as to meet the above adsorption amount. The activated carbon packed bed 8 of the adsorption tower 9 may be used at room temperature.

[0028] [Desorption process] The adsorbed hydrogen chloride and chlorosilanes heat the adsorbed activated carbon packed bed 8 (adsorption tower 9) to about 150 ° C to about 170 ° C, and pass hydrogen through the activated carbon packed bed 8 under this heating. Desorption power by S The heated adsorption tower 9 is passed through desorption gas, cooled to about 35 ° C, and returned to the state of adsorption.

[Separation step]

 On the other hand, the desorption gas can be introduced into the second cooler 10 to separate and recover chlorosilanes and hydrogen chloride. Specifically, the desorption gas flowing out from the adsorption tower 9 is introduced into the second cooler 10, where it is cooled to about 150 ° C. to about 30 ° C. to condense and recover the chlorosilanes. The recovered chlorosilanes can be sent to the process of producing trichlorosilane by reacting hydrogen chloride with metallic silicon and can be reused. On the other hand, since hydrogen chloride flows out from the second cooler 10 as an uncondensed gas, it can be recovered by absorbing it in an aqueous hydrochloric acid solution.

 [0030] As described above, the adsorption tower 9 introduces a mixed gas (adsorption of chlorosilanes and hydrogen chloride) → introduces hydrogen gas under heating (desorption of chlorosilanes and hydrogen chloride) → cools (returns to use) ) Is used according to the cycle. Therefore, in order to perform the adsorption operation continuously, a plurality of adsorption towers 9 (activated carbon packed bed 8) are provided in parallel, and a mixed gas is introduced so that each adsorption tower 9 has a certain adsorption time zone. It is recommended to switch the adsorption tower 9 for use.

 [0031] Thus, according to the hydrogen purification and recovery system of the present invention, the reaction gas generated in the trichlorosilane production reaction of the conversion facility is led to the adsorption tower 9 and passed through the activated carbon to adsorb hydrogen chloride and chlorosilanes. Therefore, hydrogen chloride and chlorosilanes can be efficiently removed from the reaction product gas using activated carbon as an adsorbent, and it is possible to obtain purified hydrogen gas.

[0032] The hydrogen chloride adsorbed on the activated carbon can be desorbed and recovered, and the hydrogen chloride that has conventionally been discarded can be recovered effectively. In addition, since chlorosilanes adsorbed on the activated carbon can be desorbed and recovered, the power of previously disposing of uncondensed chlorosilanes can be greatly reduced according to the present invention. it can. In addition, conventionally, the ability to cool chlorosilanes to cryogenic temperatures in order to condense and collect chlorosilanes as much as possible. According to the present invention, uncondensed chlorosilanes can be recovered after being separated. There is no need to cool to very low temperatures to condense chlorosilanes.

[0033] According to the present invention, the step of drying hydrogen is unnecessary, and no neutralization treatment is performed, so that the caustic soda conventionally used as a neutralizing agent is unnecessary. Furthermore, according to the present invention, the hydrogen gas recovered from the adsorption tower 9 does not contain hydrogen chloride. Therefore, this hydrogen gas is returned to the conversion facility through the circulation pipe 11 to generate a trichlorosilane. Since it can be used as at least part of the raw material gas, the raw material cost can be reduced.

 [Second Embodiment: Two-stage structure of activated carbon packed bed]

 Next, a second embodiment of the hydrogen purification and recovery system according to the present invention will be described. A second embodiment is shown in FIG. In the following description, the same components as those in the first embodiment in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

 [0035] The second embodiment differs from the first embodiment in that in the first embodiment, a force using an adsorption tower 9 having one activated carbon packed layer 8 is used. In the second embodiment, FIG. As shown, the adsorption tower 29 is configured in two stages, that is, a front-stage activated carbon packed bed 8A and a back-stage activated carbon packed bed 8B.

 [0036] In the hydrogen purification facility shown in Fig. 2, the adsorption tower 29 includes a first-stage activated carbon packed bed 8A that mainly adsorbs chlorosilanes and a second-stage activated carbon packed bed 8B that mainly absorbs hydrogen chloride. Layer 8A and post-stage activated carbon packed bed 8B are connected in series. The mixed gas introduced into the adsorption tower 29 is guided to the first preceding activated carbon packed bed 8A, and after passing through this preceding activated carbon packed bed 8A, is guided to the next succeeding activated carbon packed bed 8B.

 [Adsorption of chlorosilanes]

 When a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen is passed through activated carbon, chlorosilanes are more easily adsorbed than hydrogen chloride, so that the adsorption of chlorosilane proceeds and hydrogen chloride is absorbed even after most of the chlorosilane is adsorbed. Remains in the gas. Therefore, the activated carbon packed bed is formed in two stages, and the mixed gas is introduced into the preceding activated carbon packed bed 8A to mainly adsorb chlorosilanes.

 [0038] [Adsorption of chlorine and hydrogen]

Introduce the mixed gas via the pre-stage activated carbon packed bed 8A into the post-stage activated carbon packed bed 8B and mix Hydrogen chloride remaining in the gas is adsorbed on the activated carbon packed bed 8B. The activated carbon in the latter-stage activated carbon filling layer 8B is not adsorbed and saturated by chlorosilanes, and hydrogen chloride can be adsorbed to fresh activated carbon, so that the adsorption effect of hydrogen chloride can be enhanced.

 [0039] When the activated carbon packed bed is formed in two stages, the capacity of the activated carbon packed bed 8A in the preceding stage should be set to a capacity sufficient to mainly adsorb the chlorosilanes contained in the mixed gas. The capacity of the packed bed 8B should be set to a capacity sufficient to mainly adsorb hydrogen chloride contained in the mixed gas.

 [0040] Each of the upstream activated carbon packed bed 8A and the latter activated carbon packed bed 8B is provided with heating means (not shown), and tubes for introducing and removing a desorption gas from these packed beds 8A and 8B. There is a road. A second cooler 10 for condensing and recovering chlorosilanes contained in the desorption gas is connected to the pre-stage activated carbon packed bed 8A.

 [0041] [Desorption recovery of chlorosilanes]

 The pre-stage activated carbon packed bed 8A mainly adsorbing chlorosilanes is heated to about 150 ° C to about 170 ° C, and under this heating, the black silanes are desorbed by passing hydrogen gas through the pre-stage activated carbon packed bed 8A. The The desorption gas containing chlorosilanes is introduced into the second cooler 10 and cooled to about −50 ° C. to about −30 ° C., and the chlorosilanes are condensed and recovered. The heated pre-stage activated carbon packed bed 8A is passed through the desorption gas, then cooled to about 35 ° C and returned to the state of adsorption.

 [0042] [Desorption recovery of hydrogen chloride]

 On the other hand, the latter-stage activated carbon packed bed 8B mainly adsorbing hydrogen chloride is heated to about 150 ° C. to about 170 ° C. Under this heating, hydrogen chloride is passed through the latter-stage activated carbon packed bed 8B, so that hydrogen chloride is formed. Desorbed. This desorption gas containing hydrogen chloride is withdrawn from the latter activated carbon packed bed 8B. Since this desorption gas does not contain chlorosilanes, it can be extracted without going through the second cooler 10. Chlorine hydrogen contained in the desorption gas can be recovered and reused.

[0043] Since the adsorption rate of hydrogen on the activated carbon is small, the hydrogen in the mixed gas introduced into the adsorption tower 29 is hardly adsorbed by the activated carbon and passes through the pre-stage activated carbon packed bed 8A and the post-stage activated carbon packed bed 8B. leak. On the other hand, chlorosilanes and hydrogen chloride in the mixed gas Since it is adsorbed by the activated carbon, the gas extracted from the subsequent activated carbon packed bed 8B does not contain chlorosilanes and hydrogen chloride, and purified hydrogen gas is obtained. The refined hydrogen gas extracted from the post-stage activated charcoal packed bed 8B is returned to the evaporator 5 of the conversion facility through the circulation path 11 and reused as part of the raw material gas for the conversion reaction.

 Thus, in the second embodiment shown in FIG. 2, the reaction gas generated in the conversion reaction is passed through the pre-stage activated carbon packed bed 8A to mainly adsorb chlorosilanes, and further passes through the pre-stage activated carbon packed bed 8A. The chlorosilanes and hydrogen chloride are effectively adsorbed on the activated carbon and separated from the mixed gas by using a two-stage adsorption tower 29 in which the gas is passed through the latter-stage activated carbon packed bed 8B to mainly adsorb hydrogen chloride. And purified hydrogen gas free of hydrogen chloride.

 [0045] Further, chlorosilanes can be desorbed and recovered from the preceding activated carbon packed bed 8A, and further, pure hydrogen chloride containing almost no chlorosilanes can be desorbed and recovered from the subsequent activated carbon packed bed 8B. I'll do it.

 [0046] As described above, the adsorption tower 29 introduces a mixed gas (adsorption of chlorosilanes → adsorption of hydrogen chloride) → introduction of hydrogen gas under heating (desorption of chlorosilanes → desorption of hydrogen chloride) → cooling ( It is used according to the cycle of returning to the use state. Therefore, in order to perform the adsorption operation continuously, a plurality of adsorption towers 29 are provided in parallel, and the adsorption towers 29 for introducing the mixed gas are switched and used so that each adsorption tower 29 has a fixed adsorption time zone. Good.

 Example

 [0047] Examples of the present invention are shown below together with comparative examples. The technical scope of the present invention is not limited to the following embodiments, and various modifications can be made without departing from the spirit of the present invention.

 [0048] In each example, a product gas having the components shown in Table 1 was used as the product gas flowing out of the converter 1. In addition, an adsorption tower having a tower diameter of 1600 mmφ and a packing height of lOOOOmmh (in the second embodiment, a pre-stage activated carbon packed bed 8A and a post-stage activated carbon packed bed 8B) was used.

[0049] [Table 1] [Producted gas components]

[Example 1: Embodiment of FIG. 1]

 In accordance with the hydrogen purification and recovery system shown in Fig. 1, an adsorption tower 9 with three activated carbon packed beds 8 provided in parallel is used.Each activated carbon packed bed 8 is (adsorption) → (heat desorption) → (cooling) → (adsorption). ) → The operation was switched in this order, and the mixed gas that passed through the cooler 7 was continuously introduced into the activated carbon packed bed 8 in the adsorption use state.

 [Example Al]

 (A1) The reaction product gas shown in Table 1 was introduced into the cooler 7 and cooled to −30 ° C. at a pressure of 0.05 MPaG to collect condensed chlorosilanes. The gas passed through the cooler 7 was introduced into the activated carbon packed bed 8 (adsorption tower 9). After 4 hours from the start of gas introduction, chlorosilanes and hydrogen chloride in the exit gas of the activated carbon packed bed 8 were measured, and these gases were not detected and all were adsorbed on the activated carbon. The flow path was switched every 4 hours, and the product gas was introduced into another activated charcoal packed bed 8. The activated carbon packed bed 8 adsorbing chlorosilanes and hydrogen chloride gas was subjected to a heat desorption operation, and the adsorbed chlorosilanes and hydrogen chloride were recovered. The results are shown in Table 2.

[0052] In (A1) above, the activated carbon packed bed 8 adsorbing chlorosilanes and hydrogen chloride gas was heated to 160 ° C, and hydrogen gas was introduced into the activated carbon packed bed 8 at a flow rate of 0.5 m ³ / min. The desorption gas extracted from the activated carbon packed bed 8 was cooled to −40 ° C. with the second cooler 10 to recover 4 kmol of chlorosilanes. The gas that passed through the second cooler 10 was supplied as a raw material to a chlorination furnace in which hydrogen chloride gas and metal silicon were reacted to produce trichlorosilane.

 [Examples A2 to A3]

 The same procedure as in (A1) above was performed, except that the conditions for the condensation process (cooler 7) were set as follows. The results are shown in Table 2.

(A2) Operating pressure: 0.4 MPaG, gas temperature: The product gas cooled to 0 ° C. was supplied to the activated carbon packed bed 8 of the activated carbon adsorption tower 9. Chlorosilane and chloride water in outlet gas of activated carbon packed bed 8 No elementary gas was detected and the entire amount was adsorbed on the activated carbon.

 (A3) Operating pressure: l.OMPaG, gas temperature: The product gas cooled to 20 ° C. was supplied to the activated carbon packed bed 8 of the activated carbon adsorption tower 9. Chlorosilane and hydrogen chloride gas in the outlet gas of the activated carbon packed bed 8 were not detected, and the entire amount was adsorbed on the activated carbon.

[0054] [Table 2]

 (Method) Introducing the introduced gas ¾ is SOkmol / hr ^

 SiCU macrosilanes

[0055] [Comparative Example]

 Hydrogen was recovered by the conventional method shown in Fig. 3. Specifically, the product gas shown in Table 1 is introduced into the cooler 2, and the product gas is cooled to -50 ° C at an operating pressure of 0.05 MPaG and chlorosilane is used.

 Next, the sample is introduced into the neutralization tower where the caustic soda aqueous solution circulates to remove hydrogen chloride gas and uncondensed chlorosilanes! /, And then dried through a drying tower filled with zeolite. It was dried and returned to the converter 1 for recycling. As a result, it was not possible to recover a part of the force trichlorosilane in which TCS = 2.4 kmol / hr and STC = 15.4 kmol / hr were condensed and collected. The neutralization tower consumed 6.1kmol / hr of caustic soda.

[Example 2: Embodiment of FIG. 2]

In accordance with the hydrogen purification and recovery system shown in Fig. 2, each activated carbon is packed using an adsorption tower 29 in which a pair of activated carbon packed beds in which the former activated carbon packed bed 8A and the latter activated carbon packed layer 8B are connected in series are connected in parallel. Switch the operation of layers 8A and 8B in the order of (Adsorption) → (Heat desorption) → (Cooling) → (Adsorption) → ... and the activated carbon packed bed 8A, It was configured to be continuously introduced into 8B. [Example Bl]

 (Bl) The product gas shown in Table 1 was introduced into the cooler 7 and cooled to 10 ° C at a pressure of 0.05 MPaG to condense and collect chlorosilanes. The gas that passed through the cooler 7 was introduced into the pre-stage activated carbon packed bed 8A of the adsorption tower 29 in which the pre-stage activated carbon packed bed 8A and the post-stage activated carbon packed bed 8B were connected in a 2-series series, and then further introduced into the post-stage activated carbon packed bed 8B. .

 [0058] 2.5 hours after the start of gas introduction, hydrogen chloride gas is contained in the gas at the outlet of the pre-stage activated carbon packed bed 8A.

 However, chlorosilanes were not detected. Even after 4 hours, chlorosilanes were not detected in the gas at the outlet of the pre-stage activated carbon packed bed 8A, and all the chlorosilanes in the gas were adsorbed and collected in the pre-stage activated carbon packed bed 8A. After 4 hours, hydrogen chloride gas was not detected in the gas at the outlet of the latter-stage activated carbon packed bed 8B, and all the hydrogen chloride gas exiting the former stage 8A was adsorbed and collected in the latter-stage activated carbon packed bed 8B. Note that the gas was introduced into another adsorption tower 29 by switching the flow path in 4 hours. The activated carbon packed layers 8A and 8B adsorbing chlorosilanes and hydrogen chloride gas were subjected to a heat desorption operation. The results are shown in Tables 3 and 4.

[0059] In (B1) above, the activated carbon packed beds 8A and 8B adsorbing chlorosilanes and hydrogen chloride are heated to 160 ° C, hydrogen gas is introduced at a flow rate of 0.5 m ³ / min, and chlorosilanes, Hydrogen chloride was desorbed. The desorption gas of the pre-stage activated carbon packed bed 8A was cooled to −40 ° C. by the second cooler 10 to recover 30 kmol of chlorosilanes. The gas that passed through the second cooler 10 was supplied as a raw material for a chlorination furnace for producing trichlorosilane by reacting hydrogen chloride gas with metallic silicon. In addition, the desorption gas from the latter-stage activated carbon packed bed 8B was absorbed into a 21% aqueous hydrochloric acid solution to produce 35% concentrated hydrochloric acid. The amount of hydrogen chloride gas absorbed in the aqueous hydrochloric acid solution was 10 kmol, and no blockage of the equipment due to generation of silica or the like was observed.

 [Example B2]

 The same procedure as in (Bl) above was performed, except that the conditions for the condensation process (cooler 7) were set as follows. The results are shown in Tables 3 and 4.

(B2) The product gas was introduced into the cooler 7 and cooled to -30 ° C at a pressure of 0.05 MPaG to condense and collect chlorosilanes. The gas that passed through the cooler 7 was introduced into the pre-stage activated carbon packed bed 8A and further introduced into the post-stage activated carbon packed bed 8B. [0061] At least 4.0 hours after the start of gas introduction, hydrogen chloride is present in the gas at the outlet of the pre-stage activated carbon packed bed 8A.

 Gas was detected, but chlorosilanes were not detected. Even after 8 hours, chlorosilanes were not detected in the gas at the outlet of the pre-stage activated carbon packed bed 8A, and all the chlorosilanes in the gas were adsorbed and collected in the pre-stage activated carbon packed bed 8A. After 8 hours, hydrogen chloride gas was not detected in the gas at the outlet of the latter-stage activated carbon packed bed 8B, and all the hydrogen chloride gas exiting the former stage was adsorbed and collected in the latter-stage activated carbon packed bed 8B. In 8 hours, the flow path was switched and the gas was introduced into another absorption tower 29. In addition, the activated carbon packed beds 8A and 8B adsorbing chlorosilanes and hydrogen chloride gas were subjected to a heat desorption operation.

[Example B3]

 The condensing step (cooler 7) was carried out in the same manner as (B1) except that the conditions were set as follows. The results are shown in Tables 3 and 4.

 (B3) The produced gas was introduced into the cooler 7 and cooled to 10 ° C with l.OOMPaG pressure to condense and collect chlorosilanes. The gas passed through the cooler 7 was introduced into the pre-stage activated carbon packed bed 8A, and further introduced into the post-stage activated carbon packed bed 8B.

[0063] At least 4.0 hours after the start of gas introduction, hydrogen chloride is contained in the gas at the outlet of the pre-stage activated carbon packed bed 8A

 Gas was detected, but chlorosilanes were not detected. Even after 8 hours, chlorosilanes were not detected in the gas at the outlet of the pre-stage activated carbon packed bed 8A, and all the chlorosilanes in the gas were adsorbed and collected in the pre-stage activated carbon packed bed 8A. After 8 hours, hydrogen chloride gas was not detected in the gas at the outlet of the latter-stage activated carbon packed bed 8B, and all of the hydrogen chloride gas exited from the former stage was adsorbed and collected in the latter-stage activated carbon packed bed 8B. The flow path was switched in 8 hours, and the gas was introduced into another adsorption tower 29. The activated carbon packed bed 8 adsorbing chlorosilanes and hydrogen chloride gas was heated and desorbed.

[0064] The chlorosilanes are not included at the inlet of the latter-stage activated carbon packed bed 8B! / To obtain a mixed gas of hydrogen chloride gas and hydrogen gas, do not destroy the chlorosilanes in the first-stage activated carbon packed bed 8A! / It was necessary, and the force that could be adsorbed for 8 hours in the above example (B2XB3) The adsorbing operation was 4 hours under the condition (B1) with a large chlorosilane load. [0065] [Table 3]

 (Law) The amount of precious gas introduced is fiOtoiiol lir, SiCl

 Industrial applicability

 [0066] According to the method of [1] above and the equipment of [4] above, a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen is passed through the activated carbon packed bed, and the chlorosilanes and hydrogen chloride are adsorbed to the activated carbon. And purified hydrogen gas containing almost no chlorosilanes and hydrogen chloride can be recovered. In addition, chlorosilanes and hydrogen chloride adsorbed on activated carbon can be recovered by a desorption method such as passing hydrogen gas under heating to activated carbon, so there is no waste loss.

 [0067] According to the method of [3] and the equipment of [5] above, the activated carbon packed bed is formed in two stages, chlorosilanes are mainly adsorbed and separated in the former stage, and hydrogen chloride is mainly adsorbed and separated in the latter stage. Because

It is excellent in the separation effect of chlorosilanes and hydrogen chloride, and a purified hydrogen gas substantially free of chlorosilanes and hydrogen chloride can be obtained.

[0068] According to the method of [2] and the equipment of [6], the purification is carried out by removing chlorosilanes and hydrogen chloride from the mixed gas produced in the conversion reaction in which tetrachlorosilane and hydrogen are reacted to produce trichlorosilane. Hydrogen gas can be recovered efficiently and recycled as part of the raw material for the conversion reaction. Thereby, raw material cost can be reduced.

[0069] As described above, according to the hydrogen purification and recovery method and the hydrogen purification and recovery facility according to the present invention, The reaction product gas generated by the conversion reaction to trichlorosilane is separated by adsorbing hydrogen chloride and chlorosilanes through activated carbon, which can be desorbed and recovered after adsorption. Hydrogen chloride can be reused effectively. In addition, traditionally used as a neutralizing agent, it has been necessary to use caustic soda.

 Furthermore, conventionally, the mixed gas is cooled to an extremely low temperature to condense and separate chlorosilanes and neutralize them. However, unseparated chlorosilanes remain, so it is impossible to avoid waste loss. . On the other hand, since the chlorosilanes adsorbed on the activated carbon can be desorbed and recovered in the method and equipment of the present invention, it is necessary to cool the mixed gas to a very low temperature and to separate the condensed gas, and also to reduce the chlorosilanes. No disposal loss occurs.

Claims

The scope of the claims  [1] A hydrogen purification and recovery method in which a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen is passed through an activated carbon packed bed, and the chlorosilanes and hydrogen chloride are adsorbed on the activated carbon and separated from the gas.  [2] The mixed gas produced in the conversion reaction in which tetrachlorosilane and hydrogen are reacted to form trichlorosilane is passed through the activated carbon packed bed, and chlorosilanes and hydrogen chloride are adsorbed on the activated carbon and separated from the gas. Hydrogen purification and recovery method.  [3] A two-stage activated carbon packed bed that mainly adsorbs chlorosilanes and a second activated carbon packed bed that mainly adsorbs hydrogen chloride are formed in two stages, and the mixed gas is mixed into the first activated carbon packed bed and the second activated carbon packed bed. The method for purifying and recovering hydrogen according to claim 1 or claim 2, wherein the chlorosilanes and hydrogen chloride are separated stepwise by passing continuously.  [4] Adsorption device with an activated carbon packed bed that adsorbs chlorosilanes and hydrogen chloride, and a pipe for introducing a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen to the adsorption device! .  [5] An adsorber having a pre-stage activated carbon packed bed that mainly adsorbs chlorosilanes and a post-stage activated charcoal packed bed that mainly adsorbs hydrogen chloride, and a mixed gas containing chlorosilanes and hydrogen chloride together with hydrogen into the adsorber. 5. The hydrogen purification and recovery facility according to claim 4, further comprising a conduit for guiding and flowing through the pre-stage activated carbon packed bed and the post-stage activated carbon packed bed.  [6] It is connected to a conversion facility that reacts tetrachlorosilane with hydrogen to generate trichlorosilane, and the mixed gas generated in the conversion reaction is led to an adsorption device, and the purified hydrogen is passed through the adsorption device to the above-described hydrogen. The hydrogen purification / recovery facility according to claim 4 or 5, further comprising a circulation pipe for returning to the conversion facility.