CN115838175A - Method and system for removing carbon impurities in chlorosilane - Google Patents
Method and system for removing carbon impurities in chlorosilane Download PDFInfo
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- CN115838175A CN115838175A CN202211362206.XA CN202211362206A CN115838175A CN 115838175 A CN115838175 A CN 115838175A CN 202211362206 A CN202211362206 A CN 202211362206A CN 115838175 A CN115838175 A CN 115838175A
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- chlorosilane
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- 239000005046 Chlorosilane Substances 0.000 title claims abstract description 135
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical compound Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 title claims abstract description 135
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- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 121
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 44
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- YGZSVWMBUCGDCV-UHFFFAOYSA-N chloro(methyl)silane Chemical compound C[SiH2]Cl YGZSVWMBUCGDCV-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims abstract description 29
- 238000009833 condensation Methods 0.000 claims abstract description 23
- 230000005494 condensation Effects 0.000 claims abstract description 23
- 239000005055 methyl trichlorosilane Substances 0.000 claims abstract description 22
- JLUFWMXJHAVVNN-UHFFFAOYSA-N methyltrichlorosilane Chemical compound C[Si](Cl)(Cl)Cl JLUFWMXJHAVVNN-UHFFFAOYSA-N 0.000 claims abstract description 22
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- 238000004519 manufacturing process Methods 0.000 claims abstract description 18
- 238000002156 mixing Methods 0.000 claims abstract description 12
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- 239000000203 mixture Substances 0.000 claims description 20
- 230000002209 hydrophobic effect Effects 0.000 claims description 18
- 239000002808 molecular sieve Substances 0.000 claims description 14
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 8
- 238000004821 distillation Methods 0.000 claims description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 7
- 239000003607 modifier Substances 0.000 claims description 7
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- 235000021355 Stearic acid Nutrition 0.000 claims description 5
- 238000005341 cation exchange Methods 0.000 claims description 5
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical class O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 5
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims description 5
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 claims description 5
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 claims description 5
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims description 5
- 239000008117 stearic acid Substances 0.000 claims description 5
- KWIUHFFTVRNATP-UHFFFAOYSA-N Betaine Natural products C[N+](C)(C)CC([O-])=O KWIUHFFTVRNATP-UHFFFAOYSA-N 0.000 claims description 4
- KWIUHFFTVRNATP-UHFFFAOYSA-O N,N,N-trimethylglycinium Chemical compound C[N+](C)(C)CC(O)=O KWIUHFFTVRNATP-UHFFFAOYSA-O 0.000 claims description 4
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- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 4
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 4
- 229920000136 polysorbate Polymers 0.000 claims description 4
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- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 claims description 3
- 238000003786 synthesis reaction Methods 0.000 claims description 3
- 239000007789 gas Substances 0.000 abstract description 93
- KTQYJQFGNYHXMB-UHFFFAOYSA-N dichloro(methyl)silicon Chemical compound C[Si](Cl)Cl KTQYJQFGNYHXMB-UHFFFAOYSA-N 0.000 abstract description 23
- 239000005048 methyldichlorosilane Substances 0.000 abstract description 23
- 239000002994 raw material Substances 0.000 abstract description 16
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- 239000005049 silicon tetrachloride Substances 0.000 description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
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Abstract
The invention provides a method and a system for removing carbon impurities in chlorosilane, wherein the method comprises the following steps: mixing carbon-containing chlorosilane and reduction tail gas in the production process of polycrystalline silicon so as to enable materials in the carbon-containing chlorosilane and the reduction tail gas to react, condensing the reacted mixed material so as to enable the chlorosilane in the reacted mixed material to be condensed into liquid, adsorbing gas generated by condensation so as to remove methane in the liquid, and rectifying the liquid generated by condensation so as to remove methyltrichlorosilane in the liquid. According to the invention, on the premise of not needing a catalyst and/or raw material concentration, the reaction of the methyldichlorosilane is promoted by using the waste heat of the reduction tail gas, so that the methyldichlorosilane is converted into the methyltrichlorosilane with higher boiling point and the methane gas with lower boiling point, the technical means is simple, the separation efficiency of trichlorosilane and methylchlorosilane impurities can be improved, the separation energy consumption is reduced, and a new idea is provided for the utilization of the heat energy of the reduction tail gas.
Description
Technical Field
The invention relates to the technical field of chlorosilane purification, in particular to a method and a system for removing carbon impurities in chlorosilane.
Background
Crystalline silicon (polysilicon and monocrystalline silicon) is an important component material of solar cells and electronic components, and with the rapid promotion of energy strategy and the rapid development of semiconductor technology, the demand of the domestic polysilicon market is rapidly increased, but higher requirements are also put forward on the quality of the polysilicon. Carbon exists in single crystal or polycrystalline silicon in a form of substitutional carbon, oxygen precipitation is easy to promote to form, and lattice distortion and formation of polycrystalline crystal boundary deep energy level composite centers are caused due to the fact that lattice constants of carbon and oxygen are different from that of silicon, so that the regular arrangement of silicon atoms is influenced, and the single crystal forming rate is influenced. Moreover, carbon atoms can induce dislocation and secondary defect of stacking fault, and deep energy level recombination center is formed, which affects minority carrier lifetime. Researches show that methyl chlorosilane in trichlorosilane is a main source of carbon impurities in polycrystalline silicon, at present, a rectification method is mainly adopted in the industry to remove the methyl chlorosilane impurities in chlorosilane, the boiling point of the methyl chlorosilane impurities is close to that of trichlorosilane, in order to further reduce the content of the methyl chlorosilane, the number of purification towers needs to be increased, or the reflux ratio needs to be improved, and the equipment investment and the operation energy consumption are greatly increased.
In recent years, the industry develops novel carbon removal technologies such as adsorption and reactive distillation, effectively improves the separation efficiency of trichlorosilane and methyl chlorosilane, reduces energy consumption, and provides a new idea for removing carbon impurities in high-purity trichlorosilane. Patent CN 111115637A discloses a method and apparatus for adsorption carbon removal, which utilizes the affinity adsorption of a resin type adsorbent rich in amino and methyl chlorosilane under the action of a platinum catalyst to reduce carbon impurities in the chlorosilane to below 50ppb, but has limited adsorption capacity, only has good removal effect on low-concentration trichlorosilane materials (the total methyl content is 20-70 ppm), and affects the large-scale application thereof, and the platinum catalyst provided by the invention is expensive.
In order to effectively solve the purification problem of chlorosilane with high carbon impurities, a great deal of research work is carried out in the industry. The Chinese patent application CN 109179426A provides a device and a method for removing methyldichlorosilane in trichlorosilane by reactive distillation, which consists of a silicon tetrachloride pretreatment device, a trichlorosilane raw material pretreatment device containing methyldichlorosilane and a reactive distillation tower, and the specific reaction is as follows: under the catalytic action of an alkaline catalyst, silicon tetrachloride and methyl dichlorosilane undergo redistribution reaction of chlorine atoms to generate trichlorosilane and methyl trichlorosilane with high boiling point (66.4 ℃), then carbon impurities in the trichlorosilane are removed by means of rectification and de-weight, in order to avoid catalyst poisoning, the chlorosilane material needs to be subjected to impurity removal pretreatment, and the process route is complex. Chinese invention patent CN 102791630B proposes that a mixture containing methyldichlorosilane, silicon tetrachloride and trichlorosilane is rectified and enriched, then silicon tetrachloride and methyldichlorosilane are subjected to chlorine atom redistribution reaction to generate high-boiling-point methylchlorosilane, and then separation of methyltrichlorosilane, silicon tetrachloride and trichlorosilane is realized through rectification and de-heavy treatment to obtain high-purity trichlorosilane; however, the raw materials need to be concentrated, which results in high energy consumption, and the concentrated raw materials contain only hundreds of ppm of methylchlorosilane, which still has low concentration and affects the reaction rate.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for removing carbon impurities in chlorosilane, which improves the separation efficiency of trichlorosilane and methyl chlorosilane impurities, reduces the separation energy consumption, and provides a new idea for the utilization of heat energy of reduction tail gas, and a system for realizing the method.
The technical scheme adopted for solving the technical problem of the invention is as follows:
the invention provides a method for removing carbon impurities in chlorosilane, which comprises the following steps: mixing carbon-containing chlorosilane and reduction tail gas in the production process of polycrystalline silicon so as to enable materials in the carbon-containing chlorosilane and the reduction tail gas to react, condensing the reacted mixed material so as to enable the chlorosilane in the reacted mixed material to be condensed into liquid, adsorbing gas generated by condensation so as to remove methane in the liquid, and rectifying the liquid generated by condensation so as to remove methyltrichlorosilane in the liquid.
Optionally, the carbon-containing chlorosilane is one or a mixture of more of chlorosilane produced in synthesis/rough distillation, chlorosilane produced in cold hydrogenation/rough distillation and high carbon-containing trichlorosilane produced in a high yield in a tower bottom discharge of a rectification system.
Optionally, the carbon-containing chlorosilane comprises the following components in parts by mass:
2% -5% SiH 2 Cl 2 88% -94% SiHCl 3 3% -8% of SiCl 4 And 0.02% -1% of methylchlorosilane, said methylchlorosilane comprising CH 3 SiHCl 2 And CH 3 SiCl 3 。
Optionally, the reduction tail gas comprises the following components in percentage by mass:
5% -15% of H 2 0.5 to 3 percent of HCl and 35 to 45 percent of SiHCl 3 35% -45% of SiCl 4 And 3% -10% SiH 2 Cl 2 And the temperature of the reduction tail gas is 500-650 ℃.
Optionally, before mixing the carbon-containing chlorosilane with the reduction tail gas in the polycrystalline silicon production process, heating the carbon-containing chlorosilane to vaporize the carbon-containing chlorosilane.
Optionally, the carbochlorosilane and the reduction tail gas are mixed and reacted under the action of an adsorbent, and the adsorbent is used for adsorbing the methylchlorosilane in the carbochlorosilane.
Optionally, the adsorbent is one or a mixture of more of activated carbon, silica gel, molecular sieve, activated alumina and modified compounds thereof.
Optionally, the volume flow ratio of the vaporized carbochlorosilane to the reduction tail gas is 1:3-1:7, and the reaction temperature of the carbochlorosilane and the reduction tail gas after mixing is 500-580 ℃.
Optionally, a second adsorbent is used to adsorb the gas produced by the condensation,
the second adsorbent is a mixture of one or more of a cation exchange modified zeolite molecular sieve, porous magnesium oxide, an aluminum phosphate molecular sieve, modified silica gel, modified activated carbon and modified alumina with hydrophobic characteristics, and the surface of the second adsorbent is subjected to hydrophobic modification through a hydrophobic modifier so as to have the hydrophobic characteristics; the hydrophobic modifier is one or a mixture of two of stearic acid, sodium dodecyl benzene sulfonate, betaine, fatty glyceride, span and tween.
The invention also provides a system for realizing the method for removing carbon impurities in chlorosilane, which comprises the following steps: a fixed bed reactor, a condensing device, an adsorption device and a rectification device,
the fixed bed reactor is respectively communicated with a reduction tail gas source and a carbon-containing chlorosilane source and is used for receiving the reduction tail gas and the carbon-containing chlorosilane so as to enable the reduction tail gas and the carbon-containing chlorosilane to be mixed and react,
the condensing device is connected with the fixed bed reactor and is used for receiving the mixed material after reaction in the fixed bed reactor and condensing the mixed material so as to condense chlorosilane in the mixed material after reaction into liquid,
the adsorption device is connected with the gas outlet of the condensing device and is used for adsorbing the gas generated by condensation to remove methane in the gas,
the rectifying device is connected with a liquid outlet of the condensing device and is used for rectifying liquid generated by condensation to remove methyltrichlorosilane in the liquid.
Optionally, the system also comprises a first regulation control module, a third regulation control module, a second regulation control module and a temperature sensor,
a first regulating valve and a first flowmeter are arranged on a pipeline of the fixed bed reactor connected with a reduction tail gas source, a first regulating control module is respectively and electrically connected with the first regulating valve and the first flowmeter,
a second regulating valve and a second flowmeter are arranged on a pipeline of the fixed bed reactor connected with the carbon-containing chlorosilane source, a third regulating control module is respectively and electrically connected with the second regulating valve and the second flowmeter,
the temperature sensor is arranged in the fixed bed reactor and is electrically connected with the second adjusting and controlling module, the second adjusting and controlling module is respectively and electrically connected with the first adjusting and controlling module and the third adjusting and controlling module and is used for generating a first control signal and transmitting the first control signal to the first adjusting and controlling module and generating a second control signal and transmitting the second control signal to the third adjusting and controlling module according to the flow signal of the reduction tail gas transmitted by the first flowmeter, the flow signal of the carbon-containing chlorosilane transmitted by the second flowmeter and the temperature signal of the fixed bed reactor transmitted by the temperature sensor,
the first adjusting control module adjusts the opening degree of the first adjusting valve according to the first control signal, and the third adjusting control module adjusts the opening degree of the second adjusting valve according to the second control signal, so that the reaction temperature in the fixed bed reactor is controlled to be 500-580 ℃.
Optionally, a heater is further disposed on a pipeline connecting the fixed bed reactor and the carbon-containing chlorosilane source, and is used for heating the carbon-containing chlorosilane to vaporize the carbon-containing chlorosilane.
Optionally, the fixed bed reactor has a bed height of 5-15m and is filled with an adsorbent for adsorbing methylchlorosilane in the carbochlorosilane.
The invention abandons the technical idea of improving the conversion of methyl dichlorosilane into high-boiling methyl trichlorosilane by means of catalysts, raw material concentration and the like in the prior art, provides the technical idea of mixing the reduction tail gas and carbon-containing chlorosilane in the production process of polycrystalline silicon, and promotes the reaction of the methyl dichlorosilane by using the waste heat of the reduction tail gas on the premise of not needing catalysts and/or raw material concentration so as to convert the methyl dichlorosilane into higher-boiling methyl trichlorosilane and lower-boiling methane gas.
Drawings
Fig. 1 is a schematic structural diagram of a system for removing carbon impurities from chlorosilanes, provided in embodiment 2 of the present invention.
In the figure: 1-reduction tail gas buffer tank; 2-a first regulating valve; 3-a first flow meter; 4-a carbochlorosilane-containing storage tank; 5-a heater; 6-a second regulating valve; 7-a second flow meter; 8-a temperature sensor; 9-fixed bed reactor; 10-a condensing unit; 11-an adsorption device; 12-a first regulation control module; 13-a third regulation control module; 14-a second regulation control module.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present invention.
In the description of the present invention, it should be noted that the indication of orientation or positional relationship, such as "up" or the like, is based on the orientation or positional relationship shown in the drawings, and is only for convenience and simplicity of description, and does not indicate or imply that the device or element referred to must be provided with a specific orientation, constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected," "disposed," "mounted," "fixed," and the like are to be construed broadly, e.g., as being fixedly or removably connected, or integrally connected; either directly or indirectly through intervening media, or may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases for those skilled in the art.
The invention provides a method for removing carbon impurities in chlorosilane, which comprises the following steps: mixing carbon-containing chlorosilane and reduction tail gas in the production process of polycrystalline silicon so as to enable materials in the carbon-containing chlorosilane and the reduction tail gas to react, condensing the reacted mixed material so as to enable the chlorosilane in the reacted mixed material to be condensed into liquid, adsorbing gas generated by condensation so as to remove methane in the liquid, and rectifying the liquid generated by condensation so as to remove methyltrichlorosilane in the liquid.
The invention also provides a system for realizing the method for removing carbon impurities in chlorosilane, which comprises the following steps: a fixed bed reactor, a condensing device, an adsorption device and a rectification device,
the fixed bed reactor is respectively communicated with a reduction tail gas source and a carbon-containing chlorosilane source and is used for receiving the reduction tail gas and the carbon-containing chlorosilane so as to enable the reduction tail gas and the carbon-containing chlorosilane to be mixed and react,
the condensing device is connected with the fixed bed reactor and is used for receiving the mixed material after reaction in the fixed bed reactor and condensing the mixed material so as to condense chlorosilane in the mixed material after reaction into liquid,
the adsorption device is connected with the gas outlet of the condensing device and is used for adsorbing the gas generated by condensation to remove methane in the gas,
the rectifying device is connected with a liquid outlet of the condensing device and is used for rectifying liquid generated by condensation to remove methyltrichlorosilane in the liquid.
Example 1:
the embodiment provides a method for removing carbon impurities in chlorosilane, which comprises the following steps: mixing carbon-containing chlorosilane and reduction tail gas in the production process of polycrystalline silicon so as to enable materials in the carbon-containing chlorosilane and the reduction tail gas to react, condensing the reacted mixed material so as to enable the chlorosilane in the reacted mixed material to be condensed into liquid, adsorbing gas generated by condensation so as to remove methane in the liquid, and rectifying the liquid generated by condensation so as to remove methyltrichlorosilane in the liquid.
In this embodiment, the carbon-containing chlorosilane is one or a mixture of several of chlorosilane produced by synthesis/rough distillation, chlorosilane produced by cold hydrogenation/rough distillation, and high-carbon-containing trichlorosilane produced at the bottom of the rectification system.
In this embodiment, the carbon-containing chlorosilane includes the following components in parts by mass:
2% -5% SiH 2 Cl 2 88% -94% SiHCl 3 3% -8% of SiCl 4 And 0.02% -1% of methylchlorosilane, said methylchlorosilane comprising CH 3 SiHCl 2 And CH 3 SiCl 3 。
In this embodiment, the reduction tail gas includes the following components in percentage by mass:
5% -15% of H 2 0.5-3% of HCl and 35-45% of SiHCl 3 35% -45% of SiCl 4 And 3% -10% SiH 2 Cl 2 And the temperature of the reduction tail gas is 500-650 ℃.
In the embodiment, before mixing the carbon-containing chlorosilane and the reduction tail gas in the production process of the polycrystalline silicon, the method further comprises the step of heating the carbon-containing chlorosilane to 80-250 ℃ to vaporize the carbon-containing chlorosilane, wherein the volume flow ratio of the vaporized carbon-containing chlorosilane to the reduction tail gas is 1:3-1:7.
In the embodiment, the reaction temperature of the mixture of the carbon-containing chlorosilane and the reduction tail gas is 500-580 ℃.
In this embodiment, the carbon-containing chlorosilane and the reduction tail gas are mixed and reacted under the action of the first adsorbent, and the first adsorbent is used for adsorbing methyl chlorosilane in the carbon-containing chlorosilane to improve the concentration of reactants and the reaction rate.
The first adsorbent is one or a mixture of more of activated carbon, silica gel, a molecular sieve, activated alumina and modified compounds thereof.
Reactions occurring in a fixed bed reactor include:
(1)CH 3 SiHCl 2 +SiCl 4 →CH 3 SiCl 3 +SiHCl 3
(2)CH 3 SiHCl 2 +SiHCl 3 →CH 3 SiCl 3 +SiH 2 Cl 2
(3)CH 3 SiHCl 2 +H 2 →CH 4 +SiH 2 Cl 2
(4)CH 3 SiHCl 2 +HCl→CH 4 +SiHCl 3
(5)CH 3 SiCl 3 +H 2 →CH 4 +SiHCl 3 。
after condensation of the reaction product, a chlorosilane material (SiHCl) 3 、SiCl 4 、SiH 2 Cl 2 、 CH 3 SiCl 3 、SiH 2 Cl 2 ) Enters a rectification system, is separated and purified by a rectification device, and is SiHCl 3 、SiCl 4 And SiH 2 Cl 2 Respectively taken as raw materials, extracted and fed into a production system, and the methyltrichlorosilane is discharged as heavy component impurities; gas (H) 2 、HCl、CH 4 Etc.) the components enter an adsorption device, the adsorption device is mainly used for selectively adsorbing methane gas, the second adsorbent is one or a mixture of several of cation exchange modified zeolite molecular sieve, porous magnesium oxide and aluminum phosphate molecular sieve with hydrophobic characteristics, and the selective adsorption of the second adsorbent to methane is enhanced by carrying out hydrophobic modification on the surface of the second adsorbent; the hydrophobic modifier is one or a mixture of two of stearic acid, sodium dodecyl benzene sulfonate, betaine, fatty glyceride, span and tween. The pressure of the adsorption device is 0.8-1.3Mpa, the adsorption temperature is 25-35 ℃, and the gas after adsorption can be used for cold hydrogenation process.
Practice shows that the method can effectively convert the methyldichlorosilane into the methyltrichlorosilane and the methane, the conversion rate of the methyldichlorosilane is more than or equal to 85 percent and can reach 97 percent at most, and the carbon content in the polycrystalline silicon is reduced to less than 200ppb at most.
In conclusion, the invention provides a method for removing methyldichlorosilane in chlorosilane by utilizing reaction-rectification-adsorption, which abandons the technical idea of improving the conversion of methyldichlorosilane into high-boiling-point methyltrichlorosilane by means of catalyst, raw material concentration and the like in the prior art, and provides a method for mixing reduction tail gas and carbon-containing chlorosilane in the production process of polycrystalline silicon, and under the premise of not needing catalyst and/or raw material concentration, the reaction of methyldichlorosilane is promoted by utilizing the waste heat of the reduction tail gas, so that the methyldichlorosilane is converted into higher-boiling-point methyltrichlorosilane and methane gas with lower boiling point.
Example 2:
as shown in fig. 1, this embodiment provides a system for implementing the method for removing carbon impurities in chlorosilane of embodiment 1, including: a fixed bed reactor 9, a condensing device 10, an adsorption device 10 and a rectification device,
the fixed bed reactor 9 is respectively communicated with a reduction tail gas source and a carbon-containing chlorosilane source and is used for receiving the reduction tail gas and the carbon-containing chlorosilane so as to enable the reduction tail gas and the carbon-containing chlorosilane to be mixed and then react,
the condensing device 10 is connected with the fixed bed reactor 9 and is used for receiving the reacted mixed material in the fixed bed reactor 9 and condensing the reacted mixed material so as to condense chlorosilane in the reacted mixed material into liquid,
the adsorption device 10 is connected with the gas outlet of the condensation device 10 and is used for adsorbing the gas generated by condensation to remove methane therein,
the rectifying device is connected with the liquid outlet of the condensing device 10 and is used for rectifying the liquid generated by condensation to remove the methyltrichlorosilane in the liquid.
In this embodiment, still include reduction tail gas buffer tank 1 and carbosilane storage tank 4, reduction tail gas buffer tank 1 is arranged in storing the reduction tail gas in the polycrystalline silicon production process, and carbosilane storage tank 4 is arranged in storing the carbosilane that contains in the polycrystalline silicon production process, specifically, fixed bed reactor 9 communicates with reduction tail gas buffer tank 1 and carbosilane storage tank 4 through the pipeline respectively.
In the embodiment, the device also comprises a first regulation control module 12, a third regulation control module 13, a second regulation control module 14 and a temperature sensor 8,
a first regulating valve 2 and a first flow meter 3 are arranged on a pipeline of the fixed bed reactor 9 connected with a reduction tail gas source, a first regulating control module 12 is respectively and electrically connected with the first regulating valve 2 and the first flow meter 3,
a second regulating valve 6 and a second flow meter 7 are arranged on a pipeline of the fixed bed reactor 9 connected with the carbon-containing chlorosilane source, a third regulating control module 13 is respectively and electrically connected with the second regulating valve 6 and the second flow meter 7,
the temperature sensor 8 is arranged in the fixed bed reactor 9 and is electrically connected with the second adjusting control module 14, the second adjusting control module 14 is respectively electrically connected with the first adjusting control module 12 and the third adjusting control module 13 and is used for generating a first control signal and transmitting the first control signal to the first adjusting control module 12 and generating a second control signal and transmitting the second control signal to the third adjusting control module 13 according to the flow signal of the reducing tail gas transmitted by the first flowmeter 3, the flow signal of the carbon-containing chlorosilane transmitted by the second flowmeter 7 and the temperature signal of the fixed bed reactor 9 transmitted by the temperature sensor 8,
the first regulating control module 12 regulates the opening degree of the first regulating valve 2 according to the first control signal, and the third regulating control module 13 regulates the opening degree of the second regulating valve 6 according to the second control signal, so that the reaction temperature in the fixed bed reactor 9 is controlled to be 500-580 ℃.
In this embodiment, a heater 5 is further disposed on a pipeline connecting the fixed bed reactor 9 and the carbon-containing chlorosilane source, and is used for heating the carbon-containing chlorosilane to vaporize the carbon-containing chlorosilane.
In this embodiment, the fixed bed reactor 9 has a bed height of 5 to 15m and is filled with an adsorbent for adsorbing methylchlorosilane among carbochlorosilane.
After the carbon-containing chlorosilane material is heated by a heater 5 (80-250 ℃), feeding the carbon-containing chlorosilane material and the reduction tail gas according to a certain proportion, wherein the volume flow ratio of the carbon-containing chlorosilane to the reduction tail gas is 1:3-1: 7; the feeding amount of the reduction tail gas and the chlorosilane raw material is controlled by a control unit, and the specific process comprises the following steps: a first adjusting valve 2, a first flow meter 3 and a first adjusting control module 12 (FDC-1) are arranged between the reduction tail gas buffer tank 1 and the fixed bed reactor 9, and the first adjusting valve 2 and the first flow meter 3 are interlocked through the first adjusting control module 12 (FDC-1) to form a first feeding control unit; a second adjusting valve 6, a second flow meter 7 and a third adjusting control module 13 (FDC-3) are arranged between the heater 5 and the fixed bed reactor, and the second adjusting valve 6 and the second flow meter 7 are interlocked through the third adjusting control module 13 (FDC-3) to form a second feeding control unit; a second adjusting control module 14 (FDC-2) is arranged between the first adjusting control module 12 (FDC-1) and the third adjusting control module 13 (FDC-3), the first feeding control unit and the second feeding control unit form linkage through the second adjusting control module to control the ratio of the feeding amount of the reducing tail gas and the carbon-containing chlorosilane, the second adjusting control module 14 (FDC-2) is connected with the temperature sensor 8 and is used for controlling the ratio of the volume flow of the reducing tail gas and the carbon-containing chlorosilane according to the temperature of the fixed bed reactor, and the reaction temperature is controlled between 500 ℃ and 580 ℃.
Through foretell the control unit, can realize the accurate control to reaction process.
The height of the bed layer of the fixed bed reactor is 5-15m, and the fixed bed is filled with a selective modified adsorbent, and the main function of the fixed bed reactor is to adsorb and enrich methyl chlorosilane in trichlorosilane and improve the concentration of reactants and the reaction rate. The adsorbent is one or a mixture of more of activated carbon, silica gel, molecular sieve, activated alumina and modified compounds thereof. Reactions occurring in a fixed bed reactor include:
(1)CH 3 SiHCl 2 +SiCl 4 →CH 3 SiCl 3 +SiHCl 3
(2)CH 3 SiHCl 2 +SiHCl 3 →CH 3 SiCl 3 +SiH 2 Cl 2
(3)CH 3 SiHCl 2 +H 2 →CH 4 +SiH 2 Cl 2
(4)CH 3 SiHCl 2 +HCl→CH 4 +SiHCl 3
(5)CH 3 SiCl 3 +H 2 →CH 4 +SiHCl 3 。
the condensing device 10 is arranged between the fixed bed reactor and the rectification system and between the fixed bed reactor and the gas separation system, and after reaction products are condensed by the condensing device 10, chlorosilane materials (SiHCl) 3 、SiCl 4 、SiH 2 Cl 2 、CH 3 SiCl 3 、SiH 2 Cl 2 ) Enters a rectification system, is separated and purified by a rectification device, and is SiHCl 3 、SiCl 4 And SiH 2 Cl 2 Respectively taken as raw materials, extracted and fed into a production system, and the methyltrichlorosilane is discharged as heavy component impurities; gas (H) 2 、HCl、CH 4 Etc.) the components enter the adsorption device 11, in this embodiment, the adsorption device 11 is an adsorption column which is mainly used for selectively adsorbing methane gas, the adsorbent is one or a mixture of several of a cation exchange modified zeolite molecular sieve, porous magnesium oxide and an aluminophosphate molecular sieve with hydrophobic characteristics, and the selective adsorption of the adsorbent to methane is enhanced by performing hydrophobic modification on the surface of the adsorbent; the hydrophobic modifier is one or a mixture of two of stearic acid, sodium dodecyl benzene sulfonate, betaine, fatty glyceride, span and tween. The pressure of the adsorption column is 0.8-1.3Mpa, the adsorption temperature is 25-35 ℃, and the gas after adsorption can be used for cold hydrogenation process.
Practice shows that the method and the system can effectively convert the methyldichlorosilane into the methyltrichlorosilane and the methane, the conversion rate of the methyldichlorosilane is more than or equal to 85 percent and can reach 97 percent at most, and the carbon content in the polycrystalline silicon is reduced to less than 200ppb at most.
Compared with the prior art, the invention has the following beneficial effects:
1) The combined application of reaction, rectification and adsorption technologies overcomes the problem that carbon impurities in chlorosilane are difficult to deeply remove by the traditional rectification technology, and effectively improves the quality of the chlorosilane and the polycrystalline silicon;
2) The fixed bed reactor is filled with a selective adsorbent, and the main function is to enrich methyl chlorosilane, improve the concentration of the methyl chlorosilane in the chlorosilane and the reaction rate of a conversion reaction, and further improve the conversion rate of the methyl chlorosilane;
3) By adopting the method, the carbon-containing organic impurities can be converted into methyl trichlorosilane with high boiling point and methane gas with low boiling point, and the energy consumption brought by separation and purification is reduced;
4) The invention does not need to pretreat the material and concentrate and enrich the carbon-containing impurities, thereby simplifying the process flow and reducing the production cost;
5) The method adopts the hydrophobic adsorbent to selectively adsorb and remove the methane in the hydrogen, the adsorption process is not influenced by the content of the hydrogen chloride in the hydrogen, and the hydrogen chloride in the hydrogen is not required to be removed, so the process is simplified, and the energy consumption for separation is reduced;
6) According to the invention, the reaction device is linked with each monitoring unit, so that the reaction process can be accurately controlled;
7) The reaction is promoted by using the waste heat of the reduction tail gas, so that the comprehensive utilization of the heat energy of the reduction tail gas in the production process of the polycrystalline silicon is realized, and the energy consumption is reduced.
In summary, the present invention solves the following technical problems: (1) The boiling points of the methyldichlorosilane and the trichlorosilane are close, and the problem that the carbon impurities in the chlorosilane are difficult to deeply remove by the existing rectification technology is solved; (2) The saturated adsorption quantity is limited, and the application of the adsorption technology in the aspect of purifying chlorosilane containing higher carbon is limited; (3) The concentration of the reactant methylchlorosilane in the chlorosilane is low, so that the reaction rate of the redistribution reaction of the hydrogen chloride is low, and the conversion rate needs to be further improved; (4) In some documents, the distillation technology is used for removing impurities and concentrating and enriching reaction raw materials, so that the problems of long process flow and high energy consumption are caused. The invention (1) effectively improves the quality of trichlorosilane and polycrystalline silicon, and (2) provides a new idea for comprehensive utilization of thermal energy of reduction tail gas in the production process of polycrystalline silicon.
Example 3:
the present embodiment provides an example of implementing carbon impurity removal in chlorosilane by using the method of embodiment 1 and the apparatus of embodiment 2:
in the embodiment, the reaction raw materials are reduction tail gas and carbon-containing chlorosilane, wherein the reduction tail gas is H 2 、HCl、SiHCl 3 、SiCl 4 And SiH 2 Cl 2 The components are respectively 6.8 percent, 1.2 percent, 42.3 percent, 43.1 percent and 6.6 percent by mass percent, and the temperature is 580 ℃; the carbon-containing chlorosilane is high-carbon-containing trichlorosilane which is discharged at the bottom of the rectification system in high yield and is prepared from SiH 2 Cl 2 、SiHCl 3 、 SiCl 4 And methylchlorosilanes (CH) 3 SiHCl 2 And CH 3 SiCl 3 ) The compositions by mass fraction are respectively 2.5%, 93.1%, 4.37% and 0.03% (wherein, CH 3 SiHCl 2 Is 0.03% of, CH 3 SiCl 3 Not detected), the temperature was 73 ℃. The reaction of the two in the fixed bed comprises:
(1)CH 3 SiHCl 2 +SiCl 4 →CH 3 SiCl 3 +SiHCl 3
(2)CH 3 SiHCl 2 +SiHCl 3 →CH 3 SiCl 3 +SiH 2 Cl 2
(3)CH 3 SiHCl 2 +H 2 →CH 4 +SiH 2 Cl 2
(4)CH 3 SiHCl 2 +HCl→CH 4 +SiHCl 3
(5)CH 3 SiCl 3 +H 2 →CH 4 +SiHCl 3 。
the carbon-containing chlorosilane material is heated to 200 ℃ by a heater 5 to be vaporized, then is fed with the reduction tail gas according to the volume flow ratio of 1:3, the feeding amount of the reduction tail gas and the chlorosilane raw material is controlled by a control unit, and the specific process comprises the following steps: a first adjusting valve 2, a first flow meter 3 and a first adjusting control module 12 (FDC-1) are arranged between the reduction tail gas buffer tank 1 and the fixed bed reactor 9, and the first adjusting valve 2 and the first flow meter 3 are interlocked through the first adjusting control module 12 (FDC-1) to form a first feeding control unit; a second regulating valve 6, a second flow meter 7 and a third regulating control module 13 (FDC-3) are arranged between the heater 5 and the fixed bed reactor, and the second regulating valve 6 and the second flow meter 7 are interlocked through the third regulating control module 13 (FDC-3) to form a second feeding control unit; a second adjusting control module 14 (FDC-2) is arranged between the first adjusting control module 12 (FDC-1) and the third adjusting control module 13 (FDC-3), the first feeding control unit and the second feeding control unit form linkage through the second adjusting control module to control the ratio of the feeding amount of the reducing tail gas and the carbon-containing chlorosilane, the second adjusting control module 14 (FDC-2) is connected with the temperature sensor 8 and is used for controlling the ratio of the volume flow of the reducing tail gas and the carbon-containing chlorosilane according to the temperature of the fixed bed reactor, and the reaction temperature is controlled at 550 ℃.
The bed height of the fixed bed reactor is 5.5m, and the selective adsorbent filled in the reactor is modified silica gel.
The condensing device 10 is arranged between the fixed bed reactor and the rectification system and between the fixed bed reactor and the gas separation system, and after reaction products are condensed by the condensing device 10, chlorosilane materials (SiHCl) 3 、SiCl 4 、SiH 2 Cl 2 、CH 3 SiCl 3 、CH 3 SiHCl 2 ) Enters a rectification system, is separated and purified by a multi-stage rectification device, and is SiHCl 3 、SiCl 4 And SiH 2 Cl 2 Respectively taken as raw materials, extracted and fed into a production system, and the methyltrichlorosilane is discharged as heavy component impurities; gas (H) 2 、HCl、CH 4 Etc.) the components enter an adsorption device 11, wherein the adsorption device 11 is an adsorption column which is mainly used for selectively adsorbing methane gas, and an adsorbent in the adsorption column is a stearic acid modified aluminophosphate molecular sieve; the operating pressure of the adsorption column is 0.9MPa, and the temperature of the adsorption column is 28 ℃.
The chlorosilane and the polysilicon before and after the reaction are detected and analyzed, the conversion rate of the methyldichlorosilane is about 90 percent through accounting, and the carbon content in the polysilicon is about 178ppb.
Example 4:
the present embodiment provides an example of implementing carbon impurity removal in chlorosilane by using the method of embodiment 1 and the apparatus of embodiment 2:
the reaction is carried outRaw materials are reduction tail gas and carbochlorosilane, wherein the reduction tail gas is H2, HCl and SiHCl 3 、SiCl 4 And SiH 2 Cl 2 The components are 8.5 percent, 1.2 percent, 42.3 percent, 43.3 percent and 4.7 percent respectively by mass fraction and the temperature is 600 ℃; the carboncontaining chlorosilane is chlorosilane produced by cold hydrogenation/crude distillation, and is made of SiH 2 Cl 2 、SiHCl 3 、SiCl 4 And methylchlorosilanes (CH) 3 SiHCl 2 And CH 3 SiCl 3 ) The compositions by mass fraction are respectively 3.1%, 92.8%, 3.77% and 0.33% (wherein, CH 3 SiHCl 2 And CH 3 SiCl 3 The mass fractions of (A) and (B) were 0.308% and 0.022%, respectively), and the temperature was 75 ℃. The reaction of both in a fixed bed was the same as that of example 3.
The height of the bed layer of the fixed bed reactor is 5.5m, and the selective adsorbent filled in the reactor is modified activated alumina.
The other implementation steps are the same as the embodiment 1, wherein the feeding quantity ratio of the carbochlorosilane to the reduction tail gas is 1:6, and the temperature of the fixed bed reactor is controlled to be 580 ℃. The methane adsorbent is a cation exchange modified zeolite molecular sieve, and the hydrophobic modifier on the surface of the adsorbent is sodium dodecyl benzene sulfonate; the operating pressure of the adsorption column is 1.1MPa, and the temperature of the adsorption column is 30 ℃.
The chlorosilane and the polysilicon before and after the reaction are detected and analyzed, the conversion rate of the methyldichlorosilane is about 97 percent through accounting, and the carbon content in the polysilicon is about 150ppb.
Comparative example 1:
the embodiment provides an example for removing carbon impurities in chlorosilane, wherein the reaction raw materials are reduction tail gas and carbon-containing chlorosilane, and the reduction tail gas is formed by H 2 、HCl、SiHCl 3 、 SiCl 4 And SiH 2 Cl 2 The components are 8.3 percent, 1.4 percent, 41.8 percent, 43.6 percent and 4.9 percent respectively by mass fraction and the temperature is 600 ℃; the carbon-containing chlorosilane is synthesized/crude distillation-produced chlorosilane and is made of SiH 2 Cl 2 、SiHCl 3 、SiCl 4 And methylchlorosilanes (CH) 3 SiHCl 2 And CH 3 SiCl 3 ) Composition, qualityThe fractions were 3.3%, 92.69%, 3.67% and 0.34%, respectively (wherein, CH 3 SiHCl 2 And CH 3 SiCl 3 The mass fractions of (A) and (B) were 0.321% and 0.019%, respectively), and the temperature was 75 ℃. The reaction of both in fixed bed was the same as that of example 1.
The fixed bed reactor had a bed height of 5.5m, and unlike example 1, a quartz packing was packed in the fixed bed reactor.
The other implementation steps are the same as the embodiment 2, the chlorosilane and the polysilicon before and after the reaction are detected and analyzed, and the calculation shows that the conversion rate of the methyldichlorosilane is about 55 percent, and the carbon content in the polysilicon is about 310ppb.
The selective modified adsorbent in example 1 is used as a filler in the fixed bed reactors in examples 3 and 4, and can adsorb and enrich methylchlorosilane in trichlorosilane, so that the reactant concentration and the reaction rate are improved. Thus, the conversion of methyldichlorosilane was higher than that of the comparative example.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (13)
1. A method for removing carbon impurities in chlorosilane is characterized by comprising the following steps: mixing carbonlychlorosilane and reduction tail gas in the production process of polycrystalline silicon so as to enable materials in the carbonlychlorosilane and the reduction tail gas to react, condensing the reacted mixed material so as to enable chlorosilane in the reacted mixed material to be condensed into liquid, adsorbing gas generated by condensation so as to remove methane in the liquid, and rectifying the liquid generated by condensation so as to remove methyltrichlorosilane in the liquid.
2. The method for removing carbon impurities in chlorosilane as claimed in claim 1, wherein the carbon-containing chlorosilane is one or a mixture of more of synthesis/crude distillation produced chlorosilane, cold hydrogenation/crude distillation produced chlorosilane and high carbon-containing trichlorosilane produced at the bottom of a rectification system.
3. The method for removing carbon impurities in chlorosilane according to claim 1, wherein the carbon-containing chlorosilane comprises the following components in parts by mass:
2% -5% SiH 2 Cl 2 88% -94% SiHCl 3 3% -8% of SiCl 4 And 0.02% -1% of methylchlorosilane, said methylchlorosilane comprising CH 3 SiHCl 2 And CH 3 SiCl 3 。
4. The method for removing carbon impurities in chlorosilane according to claim 1, wherein the reduction tail gas comprises the following components in parts by mass:
5% -15% of H 2 0.5 to 3 percent of HCl and 35 to 45 percent of SiHCl 3 35% -45% of SiCl 4 And 3% -10% SiH 2 Cl 2 And the temperature of the reduction tail gas is 500-650 ℃.
5. The method for removing carbon impurities in chlorosilane of claim 1, further comprising heating the carbon-containing chlorosilane to vaporize the carbon-containing chlorosilane before mixing the carbon-containing chlorosilane with the reduction tail gas in the production process of polycrystalline silicon.
6. The method for removing carbon impurities in chlorosilane as claimed in claim 5, wherein the carbon-containing chlorosilane and the reduction tail gas are mixed and reacted under the action of a first adsorbent, and the first adsorbent is used for adsorbing methyl chlorosilane in the carbon-containing chlorosilane.
7. The method for removing carbon impurities in chlorosilane as claimed in claim 6, wherein the first adsorbent is one or a mixture of activated carbon, silica gel, molecular sieve, activated alumina and modified compounds thereof.
8. The method for removing carbon impurities in chlorosilane as claimed in any one of claims 5 to 7, wherein the volume flow ratio of the vaporized carbon-containing chlorosilane to the reduction tail gas is 1:3-1:7, and the reaction temperature of the carbon-containing chlorosilane and the reduction tail gas after mixing is 500-580 ℃.
9. The method for removing carbon impurities in chlorosilane according to any one of claims 5 to 7, wherein gas generated by condensation is adsorbed by using a second adsorbent,
the second adsorbent is a mixture of one or more of a cation exchange modified zeolite molecular sieve, porous magnesium oxide, an aluminum phosphate molecular sieve, modified silica gel, modified activated carbon and modified alumina with hydrophobic characteristics, and the surface of the second adsorbent is subjected to hydrophobic modification through a hydrophobic modifier so as to have the hydrophobic characteristics; the hydrophobic modifier is one or a mixture of two of stearic acid, sodium dodecyl benzene sulfonate, betaine, fatty glyceride, span and tween.
10. A system for implementing the method for removing carbon impurities in chlorosilane according to any one of claims 1 to 9, comprising: a fixed bed reactor (9), a condensing device (10), an adsorption device (10) and a rectification device,
the fixed bed reactor (9) is respectively communicated with a reduction tail gas source and a carbon-containing chlorosilane source and is used for receiving the reduction tail gas and the carbon-containing chlorosilane to mix and react the reduction tail gas and the carbon-containing chlorosilane,
the condensing device (10) is connected with the fixed bed reactor (9) and is used for receiving the reacted mixed material in the fixed bed reactor (9) and condensing the reacted mixed material so as to condense chlorosilane in the reacted mixed material into liquid,
the adsorption device (10) is connected with a gas outlet of the condensation device (10) and is used for adsorbing gas generated by condensation to remove methane,
the rectifying device is connected with a liquid outlet of the condensing device (10) and is used for rectifying the liquid generated by condensation to remove the methyltrichlorosilane in the liquid.
11. The system according to claim 10, further comprising a first regulation control module (12), a third regulation control module (13), a second regulation control module (14) and a temperature sensor (8),
a first regulating valve (2) and a first flowmeter (3) are arranged on a pipeline of the fixed bed reactor (9) connected with a reduction tail gas source, a first regulating control module (12) is respectively and electrically connected with the first regulating valve (2) and the first flowmeter (3),
a second regulating valve (6) and a second flowmeter (7) are arranged on a pipeline of the fixed bed reactor (9) connected with the carbon-containing chlorosilane source, a third regulating control module (13) is respectively and electrically connected with the second regulating valve (6) and the second flowmeter (7),
the temperature sensor (8) is arranged in the fixed bed reactor (9) and is electrically connected with the second adjusting control module (14), the second adjusting control module (14) is respectively electrically connected with the first adjusting control module (12) and the third adjusting control module (13) and is used for generating a first control signal and then transmitting the first control signal to the first adjusting control module (12) and generating a second control signal and then transmitting the second control signal to the third adjusting control module (13) according to the flow signal of the reduction tail gas transmitted by the first flowmeter (3), the flow signal of the carbon-containing chlorosilane transmitted by the second flowmeter (7) and the temperature signal of the fixed bed reactor (9) transmitted by the temperature sensor (8),
the first adjusting control module (12) adjusts the opening degree of the first adjusting valve (2) according to the first control signal, and the third adjusting control module (13) adjusts the opening degree of the second adjusting valve (6) according to the second control signal, so that the reaction temperature in the fixed bed reactor (9) is controlled at 500-580 ℃.
12. The system according to claim 10, characterized in that the fixed bed reactor (9) is further provided with a heater (5) on a pipeline connected with the carbon-containing chlorosilane source for heating the carbon-containing chlorosilanes to vaporize the carbon-containing chlorosilanes.
13. The system according to any one of claims 10-12,
the height of the bed layer of the fixed bed reactor (9) is 5-15m, and the fixed bed reactor is filled with an adsorbent,
used for adsorbing methyl chlorosilane in carbochlorosilane.
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