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CN-122006397-A - Polysilicon tail gas recovery system and method based on graded absorption and membrane separation coupling

CN122006397ACN 122006397 ACN122006397 ACN 122006397ACN-122006397-A

Abstract

The invention discloses a polysilicon tail gas recovery system and method based on graded absorption and membrane separation coupling, the system comprises a pretreatment unit, a first absorption tower, a second absorption tower, a membrane separation and purification unit, a resolution regeneration unit and a light component membrane removal unit. The pretreatment unit condenses, compresses and separates gas from liquid. The first absorption tower adopts high-purity silicon tetrachloride to remove hydrogen chloride, and the second absorption tower adopts an absorbent rich in trichlorosilane to deeply purify hydrogen. Purifying the purified hydrogen through a membrane separator to obtain electronic grade high-purity hydrogen. The rich liquid from the two absorption towers desorbs hydrogen chloride in the analysis tower, and the light component-rich liquid extracted from the reflux tank of the analysis tower is sent to the pervaporation membrane component to selectively remove light components such as dichlorosilane and the like and then returned to the system. The invention eliminates the traditional adsorption tower, reduces the cryogenic energy consumption through fractional absorption, and solves the industrial problem of light component circulation accumulation while ensuring the high purity of hydrogen and hydrogen chloride products.

Inventors

  • LU KEQIN
  • XIANG LANG
  • MEI PENG
  • ZHANG JIERUI
  • Jin Yankui

Assignees

  • 青海南玻新能源科技有限公司

Dates

Publication Date
20260512
Application Date
20260129

Claims (10)

  1. 1. Polysilicon tail gas recovery system based on graded absorption and membrane separation coupling, characterized by comprising: the pretreatment unit comprises a multistage condenser (101), a compressor (102) and a gas-liquid separator (103) which are communicated in sequence; The device comprises a first absorption tower (200), wherein a first air inlet (201) for receiving the output gas of the gas-liquid separator (103) is arranged at the lower part of the first absorption tower (200), a first air outlet (202) is arranged at the top, a first rich liquid outlet (203) is arranged at the bottom, a first spraying device (204) is arranged at the upper part in the tower, and a first packing layer (205) is arranged below the first spraying device (204); The second absorption tower (300), the lower part of the second absorption tower (300) is provided with a second air inlet (301) communicated with the first air outlet (202), the top is provided with a second air outlet (302), the bottom is provided with a second rich liquid outlet (303), the upper part in the tower is provided with a second spraying device (304), and a second filler layer (305) is arranged below the second spraying device (304); The membrane separation and purification unit comprises a membrane separator (401), wherein the membrane separator (401) is provided with a raw gas inlet (402) communicated with a second gas outlet (302), a first permeation gas outlet (403) for outputting high-purity hydrogen and a permeation residual gas outlet (405) for outputting impurity-rich gas; The analysis regeneration unit comprises an analysis tower (601) and a reflux tank (604), wherein a liquid inlet (602) for receiving absorption rich liquid is formed in the middle upper part of the tower body of the analysis tower (601), a gas phase outlet (603) is formed in the tower top, a lean liquid outlet (605) is formed in the tower bottom, the gas phase outlet (603) is communicated with the top inlet of the reflux tank (604) through a second condenser (610), a reflux port (606) is formed in the lower part of the reflux tank (604) and returns to the top of the analysis tower (601) through a pipeline, and a collecting outlet (607) and a light component collecting outlet (608) are formed in the side wall of the reflux tank; A first absorbent circulation circuit for regenerating and recycling the absorbent of the first absorption tower (200); a second absorbent circulation circuit for regenerating and recycling the absorbent of the second absorption tower (300); The light component membrane removal unit comprises a pervaporation membrane assembly (501), wherein the pervaporation membrane assembly (501) is provided with a feed inlet (502) communicated with a light component extraction outlet (608), a retentate outlet (503) and a second permeate outlet (504) communicated with a light component collection tank (506) through a first condenser (505).
  2. 2. The polysilicon tail gas recovery system based on staged absorption and membrane separation coupling of claim 1, wherein the path of the first absorbent circulation loop is: A first rich liquid outlet (203) at the bottom of the first absorption tower (200) is communicated with a liquid inlet (602) of the analysis tower (601) through a first circulating pump (207) and a first channel of a first lean-rich liquid heat exchanger (208) in sequence; The lean solution outlet (605) of the analysis tower (601) is communicated with the second channel inlet of the first lean-rich solution heat exchanger (208), and the second channel outlet of the first lean-rich solution heat exchanger (208) is communicated with the first spraying device (204) of the first absorption tower (200) sequentially through the first cooler (209) and the first absorbent storage tank (206).
  3. 3. A polysilicon tail gas recovery system based on fractional absorption and membrane separation coupling as set forth in claim 2 wherein in the first absorber circulation loop, rich liquid from the first absorber column (200) flows through a first passage of a first lean-rich liquid heat exchanger (208), lean liquid from the desorber column (601) flows through a second passage of the first lean-rich liquid heat exchanger (208), and two streams are counter-currently exchanged in the first lean-rich liquid heat exchanger (208).
  4. 4. The polysilicon tail gas recovery system based on staged absorption and membrane separation coupling of claim 1, wherein the path of the second absorbent circulation loop is: A second rich liquid outlet (303) at the bottom of the second absorption tower (300) is communicated with a liquid inlet (602) of the analysis tower (601) through a second circulating pump (307) and a first channel of a second lean-rich liquid heat exchanger (308) in sequence; The lean solution outlet (605) of the analysis tower (601) is communicated with the second channel inlet of the second lean-rich solution heat exchanger (308), and the second channel outlet of the second lean-rich solution heat exchanger (308) is communicated with the second spraying device (304) of the second absorption tower (300) sequentially through the cryogenic unit (309) and the second absorbent storage tank (306).
  5. 5. A polysilicon tail gas recovery system based on fractional absorption and membrane separation coupling as set forth in claim 4 wherein the rich liquid from the second absorber column (300) flows through the first pass of the second lean-rich liquid heat exchanger (308) and the lean liquid from the desorber column (601) flows through the second pass of the second lean-rich liquid heat exchanger (308) and the two streams are counter-currently exchanged in the second lean-rich liquid heat exchanger (308) in the second absorber circulation loop.
  6. 6. A polysilicon tail gas recovery system based on fractional absorption and membrane separation coupling as set forth in claim 1, wherein the retentate outlet (405) of the membrane separator (401) is in communication with the second inlet (301) of the second absorption column (300) and the inlet of the compressor (102).
  7. 7. A polysilicon tail gas recovery system based on fractional absorption and membrane separation coupling as set forth in claim 1 wherein the retentate outlet (503) of the light component membrane removal unit is in communication with a first absorber reservoir (206) and a second absorber reservoir (306).
  8. 8. The polysilicon tail gas recovery system based on the coupling of fractional absorption and membrane separation as set forth in claim 1, wherein the liquid inlet (602) of the resolving tower (601) is arranged at 1/3 to 1/2 of the height of the tower body, the rectifying section is formed above the liquid inlet (602), and the stripping section is formed below the liquid inlet.
  9. 9. The method for recovering polysilicon tail gas of the system according to any one of claims 1 to 8, comprising the steps of: S1, pretreatment: The reduction tail gas is cooled by a multistage condenser (101) and compressed by a compressor (102) in sequence, and then enters a gas-liquid separator (103) to separate most of chlorosilane condensate liquid, so as to obtain noncondensable gas mainly containing hydrogen, hydrogen chloride and a small amount of chlorosilane; s2, first-stage absorption: Feeding the noncondensable gas obtained in the step S1 into a first absorption tower (200) from a first air inlet (201), and carrying out countercurrent contact with a high-purity silicon tetrachloride absorbent from a first absorbent storage tank (206) at the temperature of-40 ℃ to-30 ℃ in a first filler layer (205) to remove most of hydrogen chloride to form a first rich solution; s3, second-stage absorption: Feeding the gas treated in the step S2 into a second absorption tower (300) from a second gas inlet (301), and carrying out countercurrent contact with an absorbent rich in trichlorosilane from a second absorbent storage tank (306) at the temperature of-70 ℃ to-60 ℃ in a second packing layer (305), so as to deeply remove chlorosilane impurities and form a second rich solution; s4, membrane separation and purification: Delivering the hydrogen processed in the step S3 into a membrane separator (401) from a raw material gas inlet (402), and discharging the hydrogen from a first permeate gas outlet (403) through a membrane under the driving of pressure difference to obtain high-purity hydrogen; S5, absorbent regeneration and light component removal: The first rich liquid formed in the step S2 and the second rich liquid formed in the step S3 are sent to an analysis tower (601), desorption is carried out under the heating of a reboiler (609), and the desorbed hydrogen chloride gas enters a reflux tank (604) after being condensed by a second condenser (610); Simultaneously, part of liquid is extracted from a light component extraction port (608) of a reflux tank (604) and is sent into a pervaporation membrane assembly (501), so that light components selectively permeate a membrane and are condensed and collected by a first condenser (505), and a retentate after the light components are removed is returned to a first absorbent storage tank (206) or a second absorbent storage tank (306); S6, recycling: The lean solution regenerated at the bottom of the analysis tower (601) is discharged from a lean solution outlet (605), one part exchanges heat with the first rich solution through a first lean-rich solution heat exchanger (208) and is cooled by a first cooler (209), then enters a first absorbent storage tank (206), and the other part exchanges heat with the second rich solution through a second lean-rich solution heat exchanger (308) and is cooled by a cryogenic unit (309), then enters a second absorbent storage tank (306).
  10. 10. The method for recovering polysilicon tail gas based on fractional absorption and membrane separation coupling as set forth in claim 9, wherein in the step S2, the operating pressure of the first absorption tower (200) is 1.2-1.4 MPa; in the step S5, the proportion of the liquid extracted from the reflux tank (604) to the pervaporation membrane module (501) is 5% -20% of the total amount of the liquid in the reflux tank (604), and the operation temperature of the pervaporation membrane module (501) is 40-80 ℃.

Description

Polysilicon tail gas recovery system and method based on graded absorption and membrane separation coupling Technical Field The invention relates to the technical field of polysilicon production, in particular to a polysilicon tail gas recovery system and method based on graded absorption and membrane separation coupling. Background Polysilicon is a core base material for the semiconductor and photovoltaic industries, and currently the mainstream production process is the modified siemens process. In the reduction process of the process, a large amount of tail gas rich in hydrogen, hydrogen chloride, trichlorosilane, silicon tetrachloride, dichlorosilane and other components is generated. In order to realize the recycling of resources and reduce the production cost, the tail gases must be separated and recovered with high efficiency. At present, a dry recovery process combining compression, deep cooling, absorption and adsorption is commonly adopted in industry. Typical processes are described in chinese patent publication No. CN112520697a, in which high purity Silicon Tetrachloride (STC) is used as an absorbent, HCl in the tail gas is absorbed at a low temperature of about-45 ℃ to-55 ℃, and then a trace amount of chlorosilane in the hydrogen is removed by an adsorption tower, so as to finally obtain recovered hydrogen. Although the process can realize material recovery, the following significant defects exist: The method comprises the steps of (1) maintaining extremely low temperature (-55 ℃) in an absorption process to meet the hydrogen quality requirement, so that the energy consumption of a refrigerator is huge, (2) depending on an active carbon adsorption tower for final purification, the adsorbent has a saturation problem, frequent regeneration is needed, the energy consumption and the operation complexity are increased, the hydrogen purity fluctuation is caused when the regeneration is incomplete, the production requirement of electronic grade polycrystalline silicon is difficult to be met stably, and (3) during the system operation, light components such as Dichlorosilane (DCS) are easy to accumulate in an absorption-analysis cycle, the operation stability and the absorption efficiency of the absorption tower are influenced, and part of materials are usually required to be discharged irregularly to control the concentration of the light components, so that the material loss is caused and the subsequent treatment burden is increased. Therefore, the problems of high energy consumption, poor product purity stability, unstable system operation and the like exist in the prior art, and development of a novel tail gas recovery technology capable of realizing higher product purity, lower comprehensive energy consumption and automatically solving the difficult problem of light component accumulation under milder conditions is needed. Disclosure of Invention The invention aims to solve the technical problems of providing a lactic acid cooling crystallization system and a lactic acid cooling crystallization method, and aims to realize comprehensive targets of quality improvement, synergy and consumption reduction by technical integration and process innovation, reducing cryogenic energy consumption, simultaneously canceling an adsorption unit easy to deactivate, actively and continuously removing light components in the system, thereby stably producing electronic grade high-purity hydrogen and high-purity hydrogen chloride. In order to solve the technical problems, the invention adopts the technical scheme that the polysilicon tail gas recovery system is based on the coupling of fractional absorption and membrane separation. The system comprises a pretreatment unit, a first absorption tower, a second absorption tower, a membrane separation and purification unit, a resolution regeneration unit, a first absorbent circulation loop, a second absorbent circulation loop and a light component membrane removal unit. The pretreatment unit comprises a multistage condenser, a compressor and a gas-liquid separator which are sequentially communicated, and is used for carrying out step cooling, supercharging and gas-liquid preliminary separation on the high-temperature reduction tail gas. The lower part of the first absorption tower is provided with a first air inlet communicated with a gas phase outlet of the gas-liquid separator, the top of the first absorption tower is provided with a first air outlet, and the bottom of the first absorption tower is provided with a first rich liquid outlet. The upper part in the tower is provided with a first spraying device, and a first packing layer is arranged below the first spraying device. The first absorption tower is connected with a first absorbent circulation loop which is used for delivering rich liquid after absorbing hydrogen chloride to the analysis tower for regeneration and returning regenerated and cooled lean liquid to the tower for recycling. Specifically, the loop com