阅读说明：本技术 一种氯基SiC-CVD晶体与薄膜生长制程尾气中C2+与氯硅烷FTrPSA分离方法 (Method for separating C2+ and chlorosilane FTrPSA in tail gas in growth process of chlorine-based SiC-CVD crystal and film ) 是由 汪兰海 钟娅玲 钟雨明 陈运 唐金财 蔡跃明 于 2020-12-23 设计创作，主要内容包括：本发明公开了一种氯基SiC-CVD晶体与薄膜生长制程尾气中C2+与氯硅烷FTrPSA分离方法,通过预处理、氯硅烷喷淋吸收、中温变压吸附浓缩、浅冷油吸收、多级蒸发/压缩/冷凝、HCl精制与氯硅烷中浅冷精馏工序,将氯基SiC-CVD晶体与外延薄膜生长制程尾气中的C2+与氯硅烷进行清晰分离与净化,并满足SiC-CVD制程所需的前驱物-C2+及氯硅烷原料要求而加以返回循环再利用,解决了氯基SiC-CVD制程尾气中最难且最关键的分离与净化的技术瓶颈,使得尾气或提氢或全组分回收H2、C2+、HCl及氯硅烷并返回到SiC-CVD制程中循环使用成为可能,既实现尾气的回收再利用,又减少了尾气排放,弥补了氯基SiC-CVD晶体或薄膜生长制程尾气处理技术的空白。(The invention discloses a method for separating C2+ and chlorosilane FTrPSA from tail gas in a chlorine-based SiC-CVD crystal and film growth process, which clearly separates and purifies C2+ and chlorosilane in the tail gas in the chlorine-based SiC-CVD crystal and epitaxial film growth process through the working procedures of pretreatment, chlorosilane spray absorption, medium-temperature pressure swing adsorption concentration, shallow cold oil absorption, multistage evaporation/compression/condensation, HCl refining and shallow cold rectification in the chlorosilane, meets the requirements of a precursor-C2 + and a chlorosilane raw material required by the SiC-CVD process, returns the precursor-C2 + and the chlorosilane raw material for recycling, solves the technical bottleneck of the most difficult and most critical separation and purification in the tail gas in the chlorine-based SiC-CVD process, enables the tail gas or hydrogen extraction or full component recycling of H2, C2+, HCl and chlorosilane in the SiC-CVD process to be possible, realizes the recycling of the tail gas, and the tail gas emission is reduced, and the blank of the tail gas treatment technology in the process of growing the chlorine-based SiC-CVD crystal or film is made up.)

1. A method for separating C2+ and chlorosilane FTrPSA in tail gas in a chlorine-based SiC-CVD crystal and film growth process is characterized by comprising the following steps:

raw material gas, carbon (C) source mainly comprising a light hydrocarbon component (C2 +) containing two or more carbon atoms such as ethylene (C2H 4) or (C3H 8), silicon (Si) source mainly comprising a chlorosilane (SiHmCln) such as trichlorosilane (SiHCl 3) or dichlorosilane (SiH 2Cl 2) or silicon tetrachloride (SiCl 4), and silicon (Si) source, and Chemical Vapor Deposition (CVD) of silicon carbide (SiC) crystals or chlorine-based SiC-CVD crystals grown epitaxially on a thin film on a substrate and off-gas in the process of growing the thin film by adding hydrogen chloride (HCl) and hydrogen (H2) as carrier gases, wherein the main components are C2+, SiHmCln, HCl, and small amounts of methane (CH 2), SiH4, chloroalkane (CHmCln), chloroalkene (VCM), and trace amounts of carbon monoxide (CO), carbon dioxide (CO 383), water (H3884) and silicon dioxide (685) 685 42 in addition to a large amount of hydrogen (H2), Si/C fine particles at normal pressure or low pressure and normal temperature.

2. And (2) pretreating, namely pressurizing the raw material gas, feeding the raw material gas into a pretreatment unit consisting of a dust remover, a particle removing filter and an oil mist removing catcher, sequentially removing dust, particles, oil mist, part of high chlorosilane, high chloroalkane and high hydrocarbon impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, and feeding the formed purified raw material gas into the next process, namely chlorosilane spraying absorption.

3. And (2) chlorosilane spray absorption, namely pressurizing the purified feed gas from the pretreatment process to 0.6-1.0 MPa, performing cold heat exchange to 80-160 ℃, allowing the purified feed gas to enter from the bottom of a spray absorption tower, spraying the purified feed gas from the top of the spray absorption tower by using a chlorosilane and HCl mixed liquid as an absorbent, performing reverse mass transfer exchange with the purified feed gas, allowing an absorption liquid enriched in chlorosilane and HCl to flow out from the bottom of the chlorosilane spray absorption tower, allowing the absorption liquid to enter a subsequent multistage evaporation/compression/condensation process, outputting a small amount of residual particles, high chlorosilane, high-chloroalkane and high-hydrocarbon impurities flowing out from the bottom of the tower, performing environment-friendly treatment, allowing non-condensable gas to flow out from the top of the spray absorption tower, and directly allowing the non-condensable gas.

4. The intermediate temperature pressure swing adsorption concentration, the noncondensable gas from the chlorosilane spray absorption process enters the intermediate temperature pressure swing adsorption concentration process consisting of 4 and more than 4 adsorption towers, the adsorption concentration is carried out at the operating temperature of 80-160 ℃ and the operating pressure of 0.4-0.8 MPa, the adsorption waste gas rich in hydrogen flows out from the top of the adsorption tower, the adsorption waste gas is washed by water, or is taken as fuel gas or is taken as raw material gas for extracting hydrogen to be output, the concentrated gas extracted from the bottom of the adsorption tower by vacuumizing in the desorption process enters the next process, namely shallow cold oil absorption, after cold-heat exchange and pressurization.

5. The method comprises the steps of shallow cold oil absorption, wherein concentrated gas from a medium-temperature pressure swing adsorption concentration process enters from the bottom of an absorption tower of the shallow cold oil absorption process after being subjected to heat exchange to 5-15 ℃ and compressed to 2.5-3.5 MPa, C4 (normal butane, isobutane or mixed butane) liquid solvent with the temperature of 5-15 ℃ and the pressure of 2.5-3.5 MPa is used as an absorbent, the gas is sprayed and absorbed from top to bottom, non-condensable gas flowing out of the top of the absorption tower is used as fuel gas after being subjected to heat exchange, C2+ rich liquid flows out of the bottom of the absorption tower and enters a desorption tower, C2+ gas flows out of the top of the absorption tower and is refined by an ethylene and propane rectification tower to respectively prepare ethylene or propane or other C2+ light hydrocarbon components, the ethylene or the propane directly returns to a SiC-CVD process for recycling, the C4 absorbent flows out of the bottom of the desorption tower and returns to the.

6. Multistage evaporation/compression/condensation, wherein absorption liquid from a chlorosilane spray absorption process enters multistage evaporation and then enters a condenser, gas-phase crude HCl gas is obtained from the absorption liquid, the crude HCl liquid formed after condensation enters the next process, namely HCl refining, crude chlorosilane liquid flows out from the condenser and enters subsequent chlorosilane middle-shallow cooling rectification.

7, HCl refining, wherein crude HCl liquid from the multistage evaporation/compression/condensation process enters an HCl refining process consisting of an HCl rectifying tower and a vacuum rectifying tower, wherein the operating pressure of the rectifying tower is 0.3-1.0 MPa, the operating temperature is 60-120 ℃, the operating pressure of the vacuum tower is-0.08-0.1 MPa, the operating temperature is 60-120 ℃, HCl product gas with the purity of more than 99.9% flows out of the top of the rectifying tower, one part of the HCl product gas is returned to the SiC-CVD process for recycling, the other part of the HCl product gas is used as an absorbent of a chlorosilane spray absorption process for recycling, the bottom of the tower flows into the vacuum tower, the top gas flowing out of the top of the VCM tower mainly contains VCM and chloralkane, or is directly sent to an incinerator for incineration treatment and discharge, or is sent out for extracting VCM and chlorane, heavy components flowing out of the bottom of the vacuum tower, or returns to the multistage evaporation/compression/condensation process, or returning to the next working procedure, namely a chlorosilane medium-shallow-cooling rectification working procedure.

8. And (2) performing light cold rectification on chlorosilane, mixing crude chlorosilane liquid from a multistage evaporation/compression/condensation process and/or heavy component fluid from the bottom of a vacuum tower of an HCl refining process, then feeding the mixed crude chlorosilane liquid into the chlorosilane light cold rectification process, wherein the operation temperature is-35-10 ℃, the operation pressure is 0.6-2.0 MPa, returning non-condensable gas flowing out of the top of a rectification tower to the pressure swing adsorption concentration process after heat exchange, further recovering C2+, discharging chlorosilane liquid from the bottom of the rectification tower, returning a part of the gasified chlorosilane liquid to the SiC-CVD process for recycling, and directly returning a part of the gasified chlorosilane liquid as an absorbent to the chlorosilane spray absorption process for recycling.

9. The method for separating C2+ from chlorosilane FTrPSA in tail gas in the process of growing chlorine-based SiC-CVD crystals and thin films as claimed in claim 1, wherein the pretreatment is carried out under the condition that the raw gas is waste gas or tail gas containing higher concentration of other impurities including acidic and Volatile Organic Compounds (VOCs), and alkali washing, a neutralization tower, a dryer and others can be added besides a dust remover, a particle filter and an oil mist removal catcher, so as to remove the acidic and Volatile Organic Compounds (VOCs) impurity components which have great influence on the operation of the pressure swing adsorption concentration process.

10. The method for separating C2+ from chlorosilane FTrPSA in tail gas of a chlorine-based SiC-CVD crystal and film growth process according to claim 1, wherein the purification raw material gas contains chlorosilane and HCl with higher concentration, the chlorosilane spray absorption process needs to increase chlorosilane spray absorption for one time, that is, after the purification raw material gas enters the chlorosilane spray absorption process, noncondensable gas flowing out from the top of the absorption tower enters a second chlorosilane spray absorption process, the absorbent of the process is a mixed liquid formed by mainly HCl liquid and a small amount of chlorosilane, the operation conditions of the second chlorosilane spray absorption process are the same as those of the chlorosilane spray absorption process, the noncondensable gas flowing out from the top of the absorption tower of the second chlorosilane spray absorption process enters a medium temperature pressure swing adsorption concentration process, and the chlorosilane spray absorption and the chlorosilane and HCl rich liquid flowing out from the bottom of the absorption tower of the second chlorosilane spray absorption process are mixed and then mixed Entering a multi-stage evaporation/compression/condensation process.

11. The method for separating C2+ from chlorosilane FTrPSA in tail gas from a chlorine-based SiC-CVD crystal and film growth process according to claim 1, wherein the purified feed gas contains C2+ with a high concentration, the purified feed gas firstly enters a medium-temperature pressure swing adsorption concentration process, the formed concentrated gas enters a shallow cold oil absorption process after being subjected to heat exchange and pressurization, the formed non-condensable gas is mixed with the adsorption waste gas flowing out of the medium-temperature pressure swing adsorption concentration process and then enters a chlorosilane spray absorption process, and the non-condensable gas flowing out of the shallow cold oil absorption process is washed by water, or used as fuel gas or used as feed gas for pressure swing adsorption hydrogen extraction.

12. The method for separating C2+ from chlorosilane FTrPSA in tail gas in a chlorine-based SiC-CVD crystal and film growth process of claim 1, wherein in the step of medium-temperature pressure swing adsorption concentration and desorption of the adsorption tower, C2+ gas from the top of the desorption tower in a shallow cold oil absorption process is used for replacement after the adsorption step of the adsorption tower and before the average pressure drop or the sequential release step is started, so that the concentration and the yield of C2+ are improved.

13. The method for FTrPSA separation of C2+ and chlorosilane from tail gas of chlorine-based SiC-CVD crystal and film growth process as claimed in claims 1, 3 and 4, wherein the medium temperature pressure swing adsorption concentration step comprises a two-stage PSA step, wherein the non-condensable gas from the chlorosilane spray absorption or secondary chlorosilane spray absorption step or the purified raw gas from the pretreatment step enters from the bottom of the first PSA adsorption tower (1-stage PSA) in medium temperature pressure swing adsorption, the intermediate mixed gas of the non-adsorbed phase flowing out from the top of the 1-stage PSA adsorption concentration step enters from the bottom of the second PSA adsorption tower (2-stage PSA) in the pressure swing adsorption concentration step, the adsorbed waste gas flows out from the top of the 2-stage PSA adsorption tower, and is washed with water, or used as fuel gas, or used as raw gas for pressure swing adsorption hydrogen extraction, the desorbed gas from the 1-stage PSA and 2-stage PSA, or mixed PSA is pressurized and then enters into the shallow cold oil absorption step, or the desorbed gas of the PSA of the 1 section enters a chlorosilane spray absorption process after being pressurized, and the desorbed gas of the PSA of the 2 section enters a shallow cold oil absorption process.

14. The method for separating C2+ from chlorosilane FTrPSA in tail gas of chlorine-based SiC-CVD crystal and film growth process according to claims 1, 3 and 4, wherein the pressure swing adsorption concentration step comprises a two-stage PSA step, wherein the non-condensable gas from the chlorosilane spray absorption or secondary chlorosilane spray absorption step or the purified feed gas from the pretreatment step enters from the bottom of a first PSA adsorption tower (1-stage PSA) with medium temperature and pressure swing adsorption, the adsorption waste gas flowing out from the top of the 1-stage PSA tower is washed with water or used as fuel gas, or used as the feed gas for pressure swing adsorption hydrogen extraction, the intermediate gas flowing out from the bottom of the 1-stage PSA tower is pressurized and then enters from the bottom of a second PSA adsorption tower (2-stage PSA) with pressure swing adsorption concentration step, the non-adsorption phase gas flowing out from the top of the 2-stage PSA tower is mixed with the non-condensable gas or the purified feed gas and then enters into the 1-stage PSA adsorption tower, the desorbed gas from the 2-stage PSA is used as a concentrated gas, and enters a shallow cold oil absorption process after being pressurized.

15. The method for separating C2+ from chlorosilane FTrPSA in tail gas in a chlorine-based SiC-CVD crystal and film growth process according to claim 1, wherein the chlorosilane medium and light cooling rectification process comprises two rectification towers, crude chlorosilane liquid from a multistage evaporation/compression/condensation process and/or heavy component fluid from the bottom of a vacuum tower of an HCl refining process are mixed and then enter the medium and light cooling rectification tower-1 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.0MPa, non-condensable gas of light components flows out from the top of the tower, and after being washed by water or used as fuel gas or subjected to pressure swing adsorption hydrogen extraction, the heavy component fluid flows out from the bottom of the rectification tower-1, then enters the medium and light cooling rectification tower-2 with the operating temperature of-10 to 10 ℃ and the operating pressure of 1.5 to 2.5MPa, the chlorosilane liquid flows out from the bottom of the rectification tower, and one part of the gasified gas is returned to the SiC-CVD process for recycling, the other part of the gasified gas is directly returned to the chlorosilane spray absorption process as an absorbent for recycling, and the overhead gas flowing out of the tower top enters a medium-temperature pressure swing adsorption concentration process after being subjected to heat exchange to further recover C2 +.

16. The method for separating C2+ from chlorosilane FTrPSA in tail gas of chlorine-based SiC-CVD crystal and film growth process of claim 1, wherein the cold and heat exchange between chlorosilane spray absorption or/and secondary chlorosilane spray absorption, medium temperature pressure swing adsorption concentration or/and two-stage medium temperature pressure swing adsorption concentration, shallow cold oil absorption and shallow cold rectification in chlorosilane or/and shallow cold rectification in two towers is realized by using difference of respective operating temperatures and heat exchangers, and adsorbed tail gas or non-condensable gas generated by each process as fuel gas for heating, so as to realize energy conservation of the system or heat supply of external part of the fuel gas, and keep the operating pressure of each process balanced to avoid fluctuation of the operating pressure, wherein when the operating pressure of the medium temperature pressure swing adsorption concentration process is more than 0.6MPa, the pressure changes in the adsorption and desorption cycle operation process, through program control valve and governing valve on the pipeline of connecting between each adsorption tower, realize slowly controlling evenly, prevent that the too big air current that leads to of system pressure variation from scouring the adsorption tower bed and adsorbent powderization production for this process system operation is stable and safe.

Technical Field

The invention relates to separation and purification of a carbon source, namely carbon source and light hydrocarbon components (C2 +) such as ethylene or propane above carbon and carbon dioxide, and a silicon source such as trichlorosilane or silicon tetrachloride, which are commonly used in tail gas in the epitaxial growth process of a third-generation semiconductor material silicon carbide (SiC) crystal and a film, and the environmental protection field of semiconductor manufacturing procedures, in particular to a separation method of C2+ and chlorosilane FTrPSA (full temperature swing adsorption) in tail gas in the chemical vapor deposition of silicon carbide (SiC) -crystal and film growth process.

Background

Silicon carbide (SiC) is used as a third-generation semiconductor material, and has excellent characteristics such as wide forbidden band, high temperature and high pressure resistance, high frequency and high power, and radiation resistance, so that IT has been widely used in IT and electronic consumer products, automobiles, photovoltaic photovoltaics, nuclear reactors, and power electronic devices such as power switches, variable frequency transformers, UPSs, etc. in the fields of aerospace and military where the system operating conditions are harsh, wherein epitaxy is a key production step for the wide application of SiC materials.

The SiC crystal and film epitaxial growth processes include high temperature sublimation (PVT), Chemical Vapor Deposition (CVD), Liquid Phase Epitaxy (LPE), Molecular Beam Epitaxy (MBE), electron cyclotron resonance plasma chemical vapor deposition (ECR-MPCVD), etc., and the CVD processes having low growth temperature, large production lot, good uniformity of crystal or epitaxial film, and easy control of operation are widely used in industry, wherein SiC-CVD crystal or epitaxial processes of organosilicon compounds having no chlorine, and containing C/Si source are classified according to the difference between the silicon (Si) source and the carbon (C) source (referred to as "reaction precursor") involved in the reaction. In the industry, in the SiC-CVD reaction of a silicon-containing precursor with a carbon or carbon-plus-two light hydrocarbon (C2 +) of ethylene or propane as a "C" source, a chlorine-containing compound is generally used as an auxiliary CVD reaction, such as hydrogen chloride (HCl) or chlorosilane, in order to effectively prevent the formation of SiC or Si or C particles in the gas phase and loss with tail gas emission, so that the deposition efficiency is increased or the crystal/epitaxial growth rate is increased. Hydrogen (H2) is used as carrier gas and precursor to enter a CVD reaction furnace (cavity) to react at a certain temperature and pressure, deposited crystals or epitaxial film products on a crystal substrate, and simultaneously, tail gas discharged in a gas phase along with the reaction comprises products which participate in the reaction, such as H2, CH4, C2+, chlorosilane/silane, HCl, a small amount of solid micro-particles, such as Si powder, Si clusters or C powder, C2+, chlorosilane/silane and HCl, such as ethylene or propane, which do not participate in the reaction, carrier gas H2, and trace or trace other impurities, such as carbon monoxide (CO), carbon dioxide (CO 2) and the like. Because the tail gas contains poisonous, harmful, flammable and explosive chlorosilane/silane, hydrogen, methane, C2+ components and corrosive and uneasy HCl, the method for treating the tail gas is special, and particularly the separation between the chlorosilane and the C2+ components becomes one of the key problems of recycling and reusing the tail gas.

The currently used tail gas treatment method for the chlorine-based SiC-CVD crystal or film epitaxial growth process mainly comprises a dry adsorption method and a water washing method.

Firstly, in the tail gas processor with dry adsorption, besides the adsorbent filled with silane, silicon cluster and C2+ as adsorbates, an adsorbent for more polar HCl and chlorosilane (SiHmCln), such as silicon tetrachloride (SiCl 4), trichlorosilane (SiHCl 3), dichlorosilane (SiH 2Cl 2), high chlorosilane, chloroalkane (CHmCln), chloroolefin (VCM) and the like as adsorbates, is added, and the non-adsorbates mainly include H2, CH4 and a small amount of C2+, silane and the like, and are directly discharged after being tested to reach the standard, wherein the adsorbent saturated by adsorption is periodically replaced, generally non-regenerable disposable adsorption is adopted, or Temperature Swing Adsorption (TSA) capable of on-line regeneration of the adsorbent is adopted, adsorption is performed at a lower temperature, adsorbent regeneration is performed at a higher temperature, and a cycle operation is performed, wherein the adsorbent saturated by adsorption is used, during the regeneration operation, the water vapor with higher temperature is used as regeneration carrier gas to desorb adsorbate and flow out of the adsorption tower, and then the mixture of SiO2 slurry, crude HCl, chlorosilane, C2+, etc. is obtained through cooling, condensation, washing, etc. and is output. The adsorption method only carries out harmless purification treatment, the adsorbent is easy to be poisoned, the method is suitable for the working condition that the contents of HCl, silane/chlorosilane and ethylene/C2 + in tail gas are low, the subsequent treatment of SiO2 slurry, crude HCl/chlorosilane and C2+ mixed solution is also very complicated, the emission of adsorbed waste gas still can generate greenhouse effect, or the content of light hydrocarbon components in the adsorbed waste gas exceeds standard and can reach the standard by further catalytic combustion, thereby increasing the cost of tail gas treatment.

Secondly, the water washing method is suitable for the working condition that the content of HCl, chlorosilane and the like in the tail gas is high, firstly, air and water are introduced according to the amount, silane in the tail gas is directly oxidized into SiO2 to be discharged, the chlorosilane and the water are hydrolyzed and react under the action of the air to generate SiO2 and HC1, the SiO2 is directly discharged, HCl waste solution is also discharged to a waste acid treatment unit, meanwhile, part of components such as C2+ and the like and the HCl generate hydrochlorination or oxychlorination reaction under the action of the air oxygen or the water to generate chloralkane (such as dichloroethane (EDC), chloromethane) or chloroalkene (such as chloroethylene carbonate), and the rest of inert gas or H2, CH4 and trace C2 +/silane and the like are output as non-condensable gas to be incinerated, and further, the generated incineration waste gas often contains chloride which does not reach the standard, including VCM and the like, so that secondary pollution is caused and. The water washing method has strong system corrosivity due to the introduction of water, most of the chlorosilane is decomposed into HCl and SiO2, and hydrocarbon impurities such as C2+ and the like are still contained in a gas phase or a liquid phase, so that the investment cost is increased for the treatment of hydrochloric acid waste liquid or the combustion treatment of non-condensable gas. In addition, since oxygen-containing compounds such as air and water are directly introduced, there is a safety problem such as explosion limit for flammable, explosive and even toxic components such as H2, silane/chlorosilane/siloxane/chloromethane, etc., and therefore, a large amount of air or water is required to be introduced to dilute H2 or silane/siloxane to outside the explosion limit range, for example, H2 is 4% or less, and the energy consumption is further increased.

SiC has wide application prospect as a third-generation semiconductor material in the future. However, due to its high cost, it still cannot compete with the conventional Si-based materials in many fields, wherein the SiC-CVD crystal and the precursors such as chlorosilane and C2+ consumed in the epitaxial growth process have high preparation cost and cannot be recycled from the exhaust gas. Therefore, valuable C2+ and chlorosilane are separated and recovered from tail gas of a chlorine-based SiC-CVD crystal and a film epitaxial growth process and purified to be recycled to the raw material gas standard required by the SiC-CVD process, the epitaxial cost can be effectively reduced, secondary pollution can be prevented, and the method is a work beneficial to green development of SiC materials and aims to solve the problem.

Disclosure of Invention

The invention provides a method for separating C2+ (light hydrocarbon components above carbon and carbon two) from chlorosilane in tail gas of a chlorine-based SiC-CVD crystal or epitaxial film growth process (FTrPSA), wherein the FTrPSA is a method which is based on Pressure Swing Adsorption (PSA) and can be coupled with various separation technologies, and uses the differences of Adsorption separation coefficients and physicochemical properties of different material components under different pressures and temperatures, adopts medium-Temperature chlorosilane spray absorption, C2+ shallow cold oil absorption, and coupling between shallow cold rectification and medium-Temperature Pressure Swing Adsorption in chlorosilane, including energy coupling between cold and heat quantity and Pressure, coupling between processes and cyclic operation to separate and purify the required main effective components C2+ and chlorosilane, meanwhile, hydrogen chloride (HCl) can be byproduct, or returned to the SiC-CVD process for recycling, or returned to the absorption, rectification or pressure swing adsorption concentration process for recycling, so that the recycling of process tail gas resources is realized, and the difficulty that C2+ and chlorosilane in the tail gas are difficult to separate is solved:

a method for separating C2+ and chlorosilane FTrPSA in tail gas of a chlorine-based SiC-CVD crystal and film growth process comprises the following steps:

(1) raw material gas, carbon (C) source mainly comprising a light hydrocarbon component (C2 +) containing two or more carbon atoms such as ethylene (C2H 4) or (C3H 8), silicon (Si) source mainly comprising a chlorosilane (SiHmCln) such as trichlorosilane (SiHCl 3) or dichlorosilane (SiH 2Cl 2) or silicon tetrachloride (SiCl 4), and silicon (Si) source, and Chemical Vapor Deposition (CVD) of silicon carbide (SiC) crystals or chlorine-based SiC-CVD crystals grown epitaxially on a thin film on a substrate and off-gas in the process of growing the thin film by adding hydrogen chloride (HCl) and hydrogen (H2) as carrier gases, wherein the main components are C2+, SiHmCln, HCl, and small amounts of methane (CH 2), SiH4, chloroalkane (CHmCln), chloroalkene (VCM), and trace amounts of carbon monoxide (CO), carbon dioxide (CO 383), water (H3884) and silicon dioxide (685) 685 42 in addition to a large amount of hydrogen (H2), Si/C fine particles at normal pressure or low pressure and normal temperature.

(2) And (2) pretreating, namely pressurizing the raw material gas, feeding the raw material gas into a pretreatment unit consisting of a dust remover, a particle removing filter and an oil mist removing catcher, sequentially removing dust, particles, oil mist, part of high chlorosilane, high chloroalkane and high hydrocarbon impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, and feeding the formed purified raw material gas into the next process, namely chlorosilane spraying absorption.

(3) And (2) chlorosilane spray absorption, namely pressurizing the purified feed gas from the pretreatment process to 0.6-1.0 MPa, performing cold heat exchange to 80-160 ℃, allowing the purified feed gas to enter from the bottom of a spray absorption tower, spraying the purified feed gas from the top of the spray absorption tower by using a chlorosilane and HCl mixed liquid as an absorbent, performing reverse mass transfer exchange with the purified feed gas, allowing an absorption liquid enriched in chlorosilane and HCl to flow out from the bottom of the chlorosilane spray absorption tower, allowing the absorption liquid to enter a subsequent multistage evaporation/compression/condensation process, outputting a small amount of residual particles, high chlorosilane, high-chloroalkane and high-hydrocarbon impurities flowing out from the bottom of the tower, performing environment-friendly treatment, allowing non-condensable gas to flow out from the top of the spray absorption tower, and directly allowing the non-condensable gas.

(4) The intermediate temperature pressure swing adsorption concentration, the noncondensable gas from the chlorosilane spray absorption process enters the intermediate temperature pressure swing adsorption concentration process consisting of 4 and more than 4 adsorption towers, the adsorption concentration is carried out at the operating temperature of 80-160 ℃ and the operating pressure of 0.4-0.8 MPa, the adsorption waste gas rich in hydrogen flows out from the top of the adsorption tower, the adsorption waste gas is washed by water, or is taken as fuel gas or is taken as raw material gas for extracting hydrogen to be output, the concentrated gas extracted from the bottom of the adsorption tower by vacuumizing in the desorption process enters the next process, namely shallow cold oil absorption, after cold-heat exchange and pressurization.

(5) The method comprises the steps of shallow cold oil absorption, wherein concentrated gas from a medium-temperature pressure swing adsorption concentration process enters from the bottom of an absorption tower of the shallow cold oil absorption process after being subjected to heat exchange to 5-15 ℃ and compressed to 2.5-3.5 MPa, C4 (normal butane, isobutane or mixed butane) liquid solvent with the temperature of 5-15 ℃ and the pressure of 2.5-3.5 MPa is used as an absorbent, the gas is sprayed and absorbed from top to bottom, non-condensable gas flowing out of the top of the absorption tower is used as fuel gas after being subjected to heat exchange, C2+ rich liquid flows out of the bottom of the absorption tower and enters a desorption tower, C2+ gas flows out of the top of the absorption tower and is refined by an ethylene and propane rectification tower to respectively prepare ethylene or propane or other C2+ light hydrocarbon components, the ethylene or the propane directly returns to a SiC-CVD process for recycling, the C4 absorbent flows out of the bottom of the desorption tower and returns to the.

(6) Multistage evaporation/compression/condensation, wherein absorption liquid from a chlorosilane spray absorption process enters multistage evaporation and then enters a condenser, gas-phase crude HCl gas is obtained from the absorption liquid, the crude HCl liquid formed after condensation enters the next process, namely HCl refining, crude chlorosilane liquid flows out from the condenser and enters subsequent chlorosilane middle-shallow cooling rectification.

(7) Refining HCl, feeding crude HCl liquid from a multistage evaporation/compression/condensation process into an HCl refining process consisting of an HCl rectifying tower and a vacuum rectifying tower, wherein the operating pressure of the rectifying tower is 0.3-1.0 MPa, the operating temperature is 60-120 ℃, the operating pressure of the vacuum tower is-0.08-0.1 MPa, the operating temperature is 60-120 ℃, HCl product gas with the purity of more than 99.9% flows out of the top of the rectifying tower, one part of the HCl product gas is returned to the SiC-CVD process for recycling, the other part of the HCl product gas is used as an absorbent of a chlorosilane spray absorption process for recycling, the bottom effluent of the rectifying tower enters the vacuum tower, the top gas flowing out of the top of the vacuum tower mainly contains VCM and chloroalkane, or directly enters an incinerator for incineration treatment and discharge, or is sent out for extracting VCM and chloroalkane, heavy components flowing out of the bottom of the vacuum tower, or returns to the multistage evaporation/compression/condensation process, or returning to the next working procedure, namely a chlorosilane medium-shallow-cooling rectification working procedure.

(8) And (2) performing light cold rectification on chlorosilane, mixing crude chlorosilane liquid from a multistage evaporation/compression/condensation process and/or heavy component fluid from the bottom of a vacuum tower of an HCl refining process, then feeding the mixed crude chlorosilane liquid into the chlorosilane light cold rectification process, wherein the operation temperature is-35-10 ℃, the operation pressure is 0.6-2.0 MPa, returning non-condensable gas flowing out of the top of a rectification tower to the pressure swing adsorption concentration process after heat exchange, further recovering C2+, discharging chlorosilane liquid from the bottom of the rectification tower, returning a part of the gasified chlorosilane liquid to the SiC-CVD process for recycling, and directly returning a part of the gasified chlorosilane liquid as an absorbent to the chlorosilane spray absorption process for recycling.

Furthermore, the method for separating C2+ and chlorosilane FTrPSA in tail gas in the process of growing chlorine-based SiC-CVD crystals and thin films is characterized in that pretreatment is carried out under the working condition that the raw gas is waste gas or tail gas containing other impurities with higher concentration including acidic and Volatile Organic Compounds (VOCs), and alkali washing, a neutralization tower, a dryer and other impurities can be added besides a dust remover, a particle filter and an oil mist removal catcher, so that the acidic and Volatile Organic Compounds (VOCs) impurity components which have great influence on the operation of a pressure swing adsorption concentration process are removed.

Furthermore, the method for separating C2+ from chlorosilane FTrPSA in tail gas in the process of growing the chlorine-based SiC-CVD crystal and the film is characterized in that under the working condition that the purified raw material gas contains chlorosilane with higher concentration and HCl, the chlorosilane spray absorption process needs to increase the chlorosilane spray absorption for one time, namely, after the purified raw material gas enters the chlorosilane spray absorption process, the non-condensable gas flowing out of the top of the absorption tower enters the second chlorosilane spray absorption process, the absorbent in the process is a mixed liquid formed by mainly HCl liquid and a small amount of chlorosilane, the operating conditions of the second chlorosilane spray absorption process are the same as those of the chlorosilane spray absorption process, the non-condensable gas flowing out of the top of the absorption tower in the second chlorosilane spray absorption process enters the medium-temperature pressure swing adsorption concentration process, and the chlorosilane spray absorption and the chlorosilane-rich HCl liquid flowing out of the bottom of the absorption tower in the second chlorosilane spray absorption process are mixed and then enter the multi-chlorosilane spray absorption process A stage evaporation/compression/condensation process.

Furthermore, the method for separating C2+ from chlorosilane FTrPSA in tail gas in the process of growing chlorine-based SiC-CVD crystals and films is characterized in that under the working condition that the purified feed gas contains C2+ with higher concentration, the purified feed gas firstly enters a medium-temperature pressure swing adsorption concentration process, the formed concentrated gas enters a shallow cold oil absorption process after being subjected to cold and heat exchange and pressurization, the formed non-condensable gas is mixed with adsorption waste gas flowing out of the medium-temperature pressure swing adsorption concentration process and then enters a chlorosilane spray absorption process, and the non-condensable gas flowing out of the shallow cold oil absorption process is washed by water, or used as fuel gas or used as feed gas for extracting hydrogen through pressure swing adsorption.

Furthermore, the method for separating C2+ and chlorosilane FTrPSA in tail gas in the process of growing chlorine-based SiC-CVD crystals and films is characterized in that in the step of medium-temperature pressure swing adsorption and concentration and desorption of an adsorption tower, C2+ gas from the top of the desorption tower in the process of shallow cold oil absorption is adopted for replacement after the adsorption step of the adsorption tower and before the average pressure drop or the sequential release step is started, so that the concentration and the yield of C2+ are improved.

Furthermore, the method for separating C2+ from chlorosilane FTrPSA in tail gas in the process of growing chlorine-based SiC-CVD crystals and films is characterized in that the medium-temperature pressure swing adsorption concentration process comprises a process consisting of two stages of PSA, wherein non-condensable gas from a chlorosilane spray absorption process or a secondary chlorosilane spray absorption process or purified raw gas from a pretreatment process enters from the bottom of a first PSA adsorption tower (1 stage of PSA) in medium-temperature pressure swing adsorption, intermediate mixed gas of non-adsorption phases flowing out from the top of the 1 stage of PSA tower enters from the bottom of a second PSA adsorption tower (2 stage of PSA) in the pressure swing adsorption concentration process, adsorption waste gas flows out from the top of a 2 stage of adsorption tower, and the waste gas is washed by water, or used as fuel gas, or used as raw gas for pressure swing adsorption hydrogen extraction, desorbed gas from the 1 stage of PSA and the 2 stage of PSA, or mixed and pressurized gas enters a shallow cold oil absorption process, or desorbed gas of the 1 stage of PSA enters a chlorosilane spray absorption process after pressurization, and the desorbed gas of the 2-stage PSA enters a shallow cold oil absorption process.

Furthermore, the method for separating C2+ from chlorosilane FTrPSA in tail gas in the process of growing chlorine-based SiC-CVD crystals and films is characterized in that the pressure swing adsorption concentration process comprises a process consisting of two stages of PSA, wherein non-condensable gas from the chlorosilane spray absorption or secondary chlorosilane spray absorption process or purified raw gas from the pretreatment process enters from the bottom of a first PSA adsorption tower (1 stage of PSA) for medium-temperature pressure swing adsorption, adsorption waste gas flowing out of the top of the 1 stage of PSA tower is washed by water or used as fuel gas or used as raw gas for pressure swing adsorption hydrogen extraction, intermediate gas flowing out of the bottom of the 1 stage of PSA tower is pressurized and then enters from the bottom of a second PSA adsorption tower (2 stages of PSA) for the pressure swing adsorption concentration process, non-adsorption phase gas flowing out of the top of the 2 stage of adsorption tower is mixed with the non-condensable gas or the purified raw gas and then enters the 1 stage of PSA adsorption tower, the desorbed gas from the 2-stage PSA is used as a concentrated gas, and enters a shallow cold oil absorption process after being pressurized.

Furthermore, the method for separating C2+ from chlorosilane FTrPSA in tail gas in a chlorine-based SiC-CVD crystal and film growth process is characterized in that a chlorosilane middle and light cooling rectification process consists of two rectification towers, crude chlorosilane liquid from a multistage evaporation/compression/condensation process and/or heavy component fluid from the bottom of a vacuum tower in an HCl refining process are mixed and then enter a middle and light cooling rectification tower-1 with the operating temperature ranging from-35 ℃ to-10 ℃ and the operating pressure ranging from 1.0MPa to 2.0MPa, non-condensable gas of light components flows out from the top of the tower, is washed by water or is used as fuel gas or is subjected to pressure swing adsorption hydrogen extraction, the heavy component fluid flows out from the bottom of the rectification tower-1, then enters a middle and light cooling rectification tower-2 with the operating temperature ranging from-10 ℃ to 10 ℃ and the operating pressure ranging from 1.5 MPa to 2.5MPa, and the chlorosilane liquid flows out from the bottom of the middle and light cooling rectification tower, and one part of the gasified gas is returned to the SiC-CVD process for recycling, the other part of the gasified gas is directly returned to the chlorosilane spray absorption process as an absorbent for recycling, and the overhead gas flowing out of the tower top enters a medium-temperature pressure swing adsorption concentration process after being subjected to heat exchange to further recover C2 +.

Furthermore, the method for separating C2+ from chlorosilane FTrPSA in tail gas in the process of growing chlorine-based SiC-CVD crystals and films is characterized in that the method is characterized in that the cold and heat exchange between chlorosilane spray absorption or/and secondary chlorosilane spray absorption, medium-temperature pressure swing adsorption concentration or/and two-stage medium-temperature pressure swing adsorption concentration, shallow cold oil absorption and shallow cold rectification in chlorosilane or/and shallow cold rectification in two towers is realized, through the difference of respective operating temperatures and a heat exchanger, and the adsorbed tail gas or non-condensable gas generated in each process is used as fuel gas for heating, so that the energy conservation of the system or the heat supply of part of the fuel gas output is realized, the operating pressure of each process is kept balanced, and the fluctuation of the operating pressure is avoided, wherein when the operating pressure of the medium-temperature pressure swing adsorption concentration process is more than 0.6MPa, the pressure in the cyclic operating process of adsorption and desorption changes, through program control valve and governing valve on the pipeline of connecting between each adsorption tower, realize slowly controlling evenly, prevent that the too big air current that leads to of system pressure variation from scouring the adsorption tower bed and adsorbent powderization production for this process system operation is stable and safe.

The invention has the beneficial effects that:

(1) by the method, C2+ and chlorosilane can be separated, purified and recovered from tail gas in a chlorine-based SiC-CVD crystal or film epitaxial growth process and returned to the process or a tail gas separation system for recycling, the technical bottleneck of the most difficult and critical separation and purification in the chlorine-based SiC-CVD tail gas is solved, hydrogen is extracted from the tail gas or H2, C2+, HCl and chlorosilane are recovered from all components and returned to the SiC-CVD process for recycling, the tail gas is recycled, the tail gas emission is reduced, and the blank of the tail gas treatment technology in the chlorine-based SiC-CVD crystal or film growth process is made up;

(2) according to the invention, by utilizing the physical chemistry and relative absorption, adsorption and rectification separation coefficient characteristics of C2+, chlorosilane, HCl and H2 components in tail gas in the ranges of medium temperature (60-160 ℃) and medium and shallow cold temperature (-35-10 ℃) and low pressure (0.2-1.0 MPa) or medium pressure (1.0-2.5 MPa), the components HCl and chlorosilane with strong absorptivity are selectively separated from non-condensable gas containing H2, C2+ and the like through medium temperature chlorosilane spray absorption by taking chlorosilane/HCl mixed liquid as an absorbent, then the C2+ component with strong adsorbability is adsorbed by a medium temperature pressure swing adsorption concentration process to form concentrated gas rich in C2+, C2+ is extracted and separated through shallow cold oil absorption, and HCl is separated through a rectification separation method, so that the invention is based on the Full Temperature Pressure Swing Adsorption (FTPSA) coupling and separation technology as the basis of medium and shallow cold temperature ranges based on various adsorption and rectification/absorption separation technologies ) The cyclic operation of C2+ adsorption/absorption and regeneration/desorption and chlorosilane absorption/rectification separation of the system is realized, and the technical bottleneck that the traditional adsorption separation process is difficult to simultaneously separate and recover C2+, HCl and chlorosilane for recycling is solved;

(3) the method has the advantages that while the separation, purification, recovery and reutilization of C2 +/chlorosilane are realized, chlorine-based SiC-CVD crystals or thin film epitaxial growth processes and sensitive oxygen-containing compounds thereof, especially O2, H2O, CO and the like are not introduced into the system, so that the whole process of recovery and reutilization is stable, and the influence on SiC crystals or epitaxial quality is reduced to zero;

(4) the invention makes use of the difference of the operating temperature of each process, and makes full use of the cold and heat of the whole operating system by arranging a reasonable cold and heat exchange system;

(5) the invention can recycle the non-condensable gas or the concentrated gas which flows out from the middle-temperature spray absorption and middle-temperature pressure swing adsorption concentration process and the non-condensable gas which is absorbed by light cold oil and rectified by medium and light cold, not only can directly or indirectly exchange heat and cold to realize full utilization of energy, but also can improve the yield of C2+ and chlorosilane and the like.

Drawings

FIG. 1 is a schematic flow chart of example 1 of the present invention.

Fig. 2 is a schematic flow chart of embodiment 2 of the present invention.

Fig. 3 is a schematic flow chart of embodiment 3 of the present invention.

Fig. 4 is a schematic flow chart of embodiment 4 of the present invention.

FIG. 5 is a schematic flow chart of embodiment 5 of the present invention.

Fig. 6 is a schematic flow chart of embodiment 6 of the present invention.

FIG. 7 is a flowchart illustrating an embodiment 7 of the present invention.

Detailed Description

In order to make those skilled in the art better understand the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention.

Example 1

As shown in FIG. 1, a method for separating C2+ and chlorosilane FTrPSA from tail gas of a chlorine-based SiC-CVD crystal and film growth process includes the following steps,

(1) raw material gas, using ethylene (C2H 4) as a main carbon (C) source, using trichlorosilane (SiHCl 3) as a main silicon (Si) source, and adding hydrogen chloride (HCl) and hydrogen (H2) as carrier gases to carry out Chemical Vapor Deposition (CVD) to prepare silicon carbide (SiC) crystals or chlorine-based SiC-CVD crystals based on film epitaxial growth on a substrate and tail gas in a film growth process, wherein the raw material gas mainly comprises C2H4, chlorosilane (SimCHln), HCl, and small amounts of methane (CH 4), SiH4, chloroalkane (CHmCln), chloroalkene (VCM), and trace amounts of carbon monoxide (CO), carbon dioxide (CO 2), water (H2O), silicon dioxide (SiO 2) and Si/C fine particles besides a large amount of hydrogen (H2), and normal temperature.

(2) And (2) pretreating, namely pressurizing the raw material gas, feeding the raw material gas into a pretreatment unit consisting of a dust remover, a particle removal filter and an oil mist removal catcher, sequentially removing dust, particles, oil mist, part of high chlorosilane, high chloroalkane and high hydrocarbon impurities under the operating conditions of 0.2-0.3 MPa pressure and normal temperature, and feeding the formed purified raw material gas into a chlorosilane spray absorption process.

(3) Chlorosilane spray absorption, wherein purified feed gas from a pretreatment process is pressurized to 0.6-1.0 MPa, and enters from the bottom of a spray absorption tower after being subjected to heat exchange to 80-160 ℃, a mixed liquid of chlorosilane and HCl is used as an absorbent, the mixed liquid is sprayed from the top of the spray absorption tower and performs reverse mass transfer exchange with the purified feed gas, an absorption liquid enriched in chlorosilane and HCl flows out from the bottom of the chlorosilane spray absorption tower and enters a multistage evaporation/compression/condensation process, a small amount of residual particles, high chlorosilane, high-chloroalkane and high-hydrocarbon impurities flowing out from the bottom of the tower are output for environment-friendly treatment, and non-condensable gas flows out from the top of the spray absorption tower and directly enters a medium-temperature pressure swing adsorption concentration process.

(4) And (2) medium-temperature pressure swing adsorption concentration, wherein non-condensable gas from a chlorosilane spray absorption process enters a medium-temperature pressure swing adsorption concentration process consisting of 5 adsorption towers, the adsorption concentration is carried out at the operating temperature of 80-160 ℃ and the operating pressure of 0.4-0.8 MPa, hydrogen-rich adsorption waste gas flows out of the top of the adsorption tower and is used as fuel gas after being washed by water, and concentrated gas pumped out of the bottom of the adsorption tower by vacuumizing is adopted in desorption and enters a shallow cold oil absorption process after cold heat exchange and pressurization.

(5) The method comprises the steps of shallow cold oil absorption, wherein concentrated gas from a medium-temperature pressure swing adsorption concentration process enters from the bottom of an absorption tower of the shallow cold oil absorption process after being subjected to heat exchange to 5-15 ℃ and compressed to 2.5-3.5 MPa, C4 (n-butane, isobutane or mixed butane) liquid solvent with the temperature of 5-15 ℃ and the pressure of 2.5-3.5 MPa is used as an absorbent, the gas is sprayed and absorbed from top to bottom, non-condensable gas flowing out of the top of the absorption tower is used as fuel gas after being subjected to heat exchange, ethylene-rich liquid flows out of the bottom of the absorption tower and enters a desorption tower, ethylene gas flows out of the top of the absorption tower, ethylene and other C2+ light hydrocarbon components are respectively prepared after being refined by an ethylene rectification tower, the ethylene directly returns to a SiC-CVD process for recycling, the C4 absorbent flows out of the bottom of the desorption tower and.

(6) And (2) multistage evaporation/compression/condensation, wherein absorption liquid from the chlorosilane spray absorption process enters multistage evaporation, then enters a condenser, gas-phase crude HCl gas is obtained from the absorption liquid, the crude HCl liquid formed after condensation enters an HCl refining process, crude chlorosilane liquid flows out from the condenser, and the crude chlorosilane liquid enters a chlorosilane middle-shallow cooling rectification process.

(7) HCl refining, crude HCl liquid from a multistage evaporation/compression/condensation process enters an HCl refining process consisting of an HCl rectifying tower and a vacuum rectifying tower, wherein the operating pressure of the rectifying tower is 0.3-1.0 MPa, the operating temperature is 60-120 ℃, the operating pressure of the vacuum tower is-0.08-0.1 MPa, the operating temperature is 60-120 ℃, HCl product gas with the purity of more than 99.9% flows out of the top of the rectifying tower, one part (50%) of the HCl product gas is returned to the SiC-CVD process for recycling, one part (50%) of the HCl product gas is used as an absorbent of a chlorosilane spray absorption process for recycling, the bottom effluent of the rectifying tower enters the vacuum tower, the top gas flowing out of the top of the tower mainly contains VCM and chloralkane or is directly sent to an incinerator for incineration treatment and discharge, the heavy component flowing out of the bottom of the vacuum tower, and one part (40%) of the HCl liquid returns to the multistage evaporation/compression/condensation process, and returning a part (60%) of the product to the chlorosilane middle light-cooling rectification process.

(8) And (2) performing light cold rectification on chlorosilane, mixing crude chlorosilane liquid from a multistage evaporation/compression/condensation process and heavy component fluid from the bottom of a vacuum tower of an HCl refining process, then entering the chlorosilane medium light cold rectification process, wherein the operating temperature is-35-10 ℃, the operating pressure is 0.6-2.0 MPa, returning noncondensable gas flowing out of the top of a rectifying tower to a pressure swing adsorption concentration process after heat exchange, further recovering C2H4, flowing out of the bottom of the rectifying tower, returning part (40%) of the chlorosilane liquid to the SiC-CVD process for recycling after gasification, and returning part (60%) of the chlorosilane liquid to the SiC-CVD process for recycling as an absorbent directly.

Example 2

As shown in fig. 2, on the basis of example 1, under the condition that the purified raw material gas contains chlorosilane and HCl with higher concentration, if greater than 6%, the chlorosilane spray absorption process needs to add chlorosilane spray absorption once, that is, after the purified raw material gas enters the chlorosilane spray absorption process, the non-condensable gas flowing out from the top of the absorption tower enters the second chlorosilane spray absorption process again, wherein the absorbent is a mixed liquid formed by mainly HCl liquid and a small amount of chlorosilane, the operating conditions of the second chlorosilane spray absorption process are the same as those of the chlorosilane spray absorption process, the non-condensable gas flowing out from the top of the absorption tower of the second chlorosilane spray absorption process enters the medium temperature pressure swing adsorption concentration process again, and the chlorosilane spray absorption and the rich chlorosilane and HCl liquid flowing out from the bottom of the absorption tower of the second chlorosilane spray absorption process are mixed and then enter the multi-stage evaporation/compression/condensation process, wherein, no solid impurities are discharged from the bottom of the secondary chlorosilane spray absorption tower.

Example 3

As shown in fig. 3, in example 1, under the condition that the purified raw material gas contains C2+ with a high concentration, for example, the concentration of C2+ is greater than 8%, the purified raw material gas firstly enters the medium-temperature pressure swing adsorption concentration step, the formed concentrated gas enters the shallow cold oil absorption step after being subjected to heat and pressure exchange, the formed non-condensable gas is mixed with the adsorption waste gas flowing out of the medium-temperature pressure swing adsorption concentration step, and then enters the chlorosilane spray absorption step, and the non-condensable gas flowing out of the chlorosilane spray absorption step is washed with water and then used as fuel gas.

Example 4

As shown in fig. 4, in the adsorption column desorption step of the medium temperature pressure swing adsorption concentration step in addition to example 1, C2+ gas from the top of the desorption column in the shallow cold oil absorption step was used for substitution after the adsorption step of the adsorption column and before the pressure equalization or the sequential step was started, so as to increase the concentration and yield of C2+ in the adsorbed phase gas in the adsorption column.

Example 5

As shown in fig. 5, in examples 1 and 2, the medium temperature pressure swing adsorption concentration step is a step consisting of two-stage PSA, in which non-condensable gas from a chlorosilane spray absorption or secondary chlorosilane spray absorption step or purified raw material gas from a pretreatment step is introduced from the bottom of a first PSA adsorption tower (1-stage PSA) in the medium temperature pressure swing adsorption, intermediate mixed gas of a non-adsorbed phase flowing out from the top of the 1-stage PSA tower is introduced from the bottom of a second PSA adsorption tower (2-stage PSA) in the pressure swing adsorption concentration step, and an adsorption waste gas flows out from the top of the 2-stage PSA tower, and is used as fuel gas after being washed with water, and desorption gas from the 1-stage PSA and the 2-stage PSA is mixed and pressurized and then introduced into a light cold oil absorption step, thereby further recovering effective components.

Example 6

As shown in fig. 6, in examples 1 and 2, the pressure swing adsorption concentration step is a step consisting of two-stage PSA, in which non-condensable gas from a chlorosilane spray absorption step or a second chlorosilane spray absorption step or purified raw material gas from a pretreatment step is introduced from the bottom of a first PSA adsorption tower (1-stage PSA) for medium temperature pressure swing adsorption, an adsorption waste gas flowing out from the top of the 1-stage PSA tower is used as a fuel gas after being washed with water, an intermediate gas flowing out from the bottom of the 1-stage PSA tower is introduced from the bottom of a second PSA adsorption tower (2-stage PSA) for pressure swing adsorption concentration step after being pressurized, a non-adsorption phase gas flowing out from the top of the 2-stage adsorption tower is mixed with the non-condensable gas or the purified raw material gas and then introduced into the 1-stage PSA adsorption tower to further recover effective components, and a desorption gas from the 2-stage PSA as a concentrated gas is pressurized and then introduced into a shallow cold oil absorption step.

Example 7

As shown in fig. 7, based on example 1, the chlorosilane middle and light cooling rectification process comprises two rectification towers, wherein the crude chlorosilane liquid from the multistage evaporation/compression/condensation process and the heavy component fluid from the bottom of the vacuum tower of the HCl purification process are mixed and then enter a middle and light cooling rectification tower-1 with the operating temperature of-35 to-10 ℃ and the operating pressure of 1.0 to 2.0MPa, the non-condensable gas of the light component flows out of the tower top and is used as fuel gas after being washed with water, the heavy component fluid flowing out of the tower bottom of the rectification tower-1 enters a middle and light cooling rectification tower-2 with the operating temperature of-10 to 10 ℃ and the operating pressure of 1.5 to 2.5MPa, the chlorosilane liquid flows out of the tower bottom, one part (40%) is gasified and then returned to the SiC-CVD process for recycling, and the other part (60%) is directly returned to the chlorosilane spray absorption process for recycling as absorbent, the overhead gas flowing out from the top of the column is subjected to heat exchange and then enters a medium-temperature pressure swing adsorption concentration process, and C2+ (ethylene) is further recovered.

It should be apparent that the above-described embodiments are only some, but not all, of the embodiments of the present invention. All other embodiments and structural changes that can be made by those skilled in the art without inventive effort based on the embodiments described in the present invention or based on the teaching of the present invention, all technical solutions that are the same or similar to the present invention, are within the scope of the present invention.