WO2024113632A1

WO2024113632A1 - Polysilicon tail gas recovery method

Info

Publication number: WO2024113632A1
Application number: PCT/CN2023/088209
Authority: WO
Inventors: 沈琛; 王舒; 姚又省; 李超; 刘继三; 王波; 柯曾鹏; 骆彩萍; 陈维平
Original assignee: 华陆工程科技有限责任公司
Priority date: 2022-11-29
Filing date: 2023-04-13
Publication date: 2024-06-06
Also published as: CN115849383A

Abstract

Provided in the present application is a polysilicon tail gas recovery method, comprising the following steps: implementing first condensation-heat exchange treatment on a tail gas to be recovered so as to obtain a first condensate liquid and a first low-temperature gas, the first condensation-heat exchange treatment comprising first condensation treatment and first heat exchange treatment, which are alternately performed; and after the first low-temperature gas is circulated as a cooling medium to participate in the first heat exchange treatment, the first low-temperature gas being heated up to become a first purified tail gas, and implementing hydrogen separation treatment on the first purified tail gas, wherein the material flow direction in which the first low-temperature gas participates in the first heat exchange treatment as a cooling medium is opposite to the material flow direction in which said tail gas is subjected to the first condensation-heat exchange treatment. The recovery method can effectively save on energy consumption and material consumption during a polysilicon tail gas recovery process, thereby reducing the production cost of tail gas recovery, and improving the competitiveness of enterprises.

Description

A method for recovering polysilicon tail gas

This application claims the priority of the Chinese patent application filed with the China Patent Office on November 29, 2022, with application number 202211511182.X and application name “A Method for Recovering Polysilicon Tail Gas”, the entire contents of which are incorporated by reference in this application.

Technical Field

The present application relates to a method for recovering polysilicon tail gas, and belongs to the technical field of polysilicon production.

Background technique

Polysilicon is a key material for manufacturing integrated circuits, photovoltaic solar cells and high-purity silicon products. With the rapid development of the electronic information industry and the solar photovoltaic industry, the market demand for polysilicon continues to increase. At present, the mainstream process for preparing polysilicon is the modified Siemens method, which reacts industrial silicon with silicon tetrachloride, hydrogen chloride and hydrogen recovered from the reduction tail gas. After dust removal, the reaction system is condensed, recovered and separated to obtain hydrogen and a mixed liquid composed of trichlorosilane generated by the reaction and unreacted silicon tetrachloride. The hydrogen returns to the system to participate in the reaction again, and the mixed liquid is separated by distillation to obtain high-purity trichlorosilane (silicon tetrachloride is purified and then hydrogenated and recycled). The vaporized trichlorosilane and hydrogen are mixed in a certain proportion and introduced into the polysilicon reduction furnace. A voltage is applied to both ends of the rod-shaped silicon core placed in the reduction furnace to generate high temperature. On the surface of the high-temperature silicon core, trichlorosilane is reduced to elemental silicon by hydrogen and deposited on the surface of the silicon core, gradually generating polysilicon rods of the required specifications. Only about 8-12% of the trichlorosilane entering the reduction furnace is converted into polysilicon, and the reduction tail gas contains a large amount of unreacted production raw materials hydrogen ( _H2 ), trichlorosilane ( _SiHCl3 ) and reaction by-products silicon tetrachloride ( _SiCl4 ), hydrogen chloride (HCl), _{dichlorodihydrogen} silicon ( _SiH2Cl2 ), etc. Through the tail gas recovery device, the "dry method" separation and recovery, the separated chlorosilane is distilled and purified, the hydrogen is returned to the reduction furnace for recycling, and the hydrogen chloride is sent to the cold hydrogenation device. This process realizes a completely closed-loop production.

The existing tail gas recovery process uses dry recovery technology, which can basically separate and recover all components in the tail gas. However, with the development of polysilicon technology, the tail gas recovery process still has a contradiction between improving the quality of the recovered product and increasing energy consumption.

Summary of the invention

The present application provides a method for recovering polysilicon tail gas, which can effectively save energy consumption and material consumption in the process of recovering polysilicon tail gas, reduce the production cost of tail gas recovery, and improve the competitiveness of the enterprise.

The present application provides a method for recovering polysilicon tail gas, comprising the following steps:

Performing a first condensation-heat exchange treatment on the tail gas to be recovered to obtain a first condensate and a first low-temperature gas; the first condensation-heat exchange treatment includes alternating first condensation treatment and first heat exchange treatment;

After the first low-temperature gas is circulated as a cooling medium to participate in the first heat exchange treatment, the first low-temperature gas is heated to become a first purified tail gas, and a hydrogen separation treatment is performed on the first purified tail gas;

The logistics direction of the first low-temperature gas as a cooling medium participating in the first heat exchange treatment is opposite to the logistics direction of the tail gas to be recovered undergoing the first condensation-heat exchange treatment.

The recovery method as described above, wherein the steps are included: the step of performing hydrogen separation treatment on the first purified tail gas comprises:

compressing the first purified tail gas to obtain first compressed purified tail gas;

Performing a second condensation-heat exchange treatment on the first compressed and purified tail gas to obtain a second condensate and a second low-temperature gas; the second condensation-heat exchange treatment includes alternating second condensation treatment and second heat exchange treatment;

The second low-temperature gas is subjected to hydrogen chloride absorption treatment to obtain hydrogen gas and chlorosilane-rich liquid;

The hydrogen is used as a cooling medium to participate in the second heat exchange process and then collected and processed;

The logistics direction of the hydrogen as a cooling medium participating in the second heat exchange treatment is opposite to the logistics direction of the first purified tail gas undergoing the second condensation-heat exchange treatment.

The recovery method as described above, wherein the second condensation-heat exchange treatment comprises:

The first condensate and the first compressed purified tail gas are subjected to a gas-liquid heat exchange treatment, the first condensate after the temperature is increased is subjected to a hydrogen chloride analysis treatment, and the first compressed purified tail gas after the temperature is decreased is subjected to the second condensation-heat exchange treatment.

The recovery method as described above, wherein, before the first condensation-heat exchange treatment, it also includes subjecting the purified hydrogen to gas-to-gas heat exchange treatment with the tail gas to be recovered, and subjecting the tail gas to be recovered after cooling to the first condensation-heat exchange treatment;

The purified hydrogen is the product of the hydrogen obtained by the collection and treatment after the hydrogen is purified. thing.

The recovery method as described above, wherein, before the gas-to-gas heat exchange treatment, it also includes a gas-solid separation treatment of the tail gas to be recovered;

The gas phase obtained by the gas-solid separation process is subjected to the gas-gas heat exchange process.

The recovery method as described above, wherein the chlorosilane rich liquid and the second condensate are subjected to a third heat exchange treatment, and the heated chlorosilane rich liquid and the second condensate are subjected to a hydrogen chloride decomposition treatment to obtain a chlorosilane lean liquid and hydrogen chloride;

Circulating the chlorosilane lean liquid as a heat medium to participate in the third heat exchange treatment;

The logistics direction of the chlorosilane lean liquid as a heat medium circulating in the third heat exchange treatment is opposite to the logistics direction of the chlorosilane rich liquid and the second condensate in the third heat exchange treatment.

In the recovery method as described above, during the process in which the chlorosilane lean liquid is circulated as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is subjected to a first cooling treatment.

The recovery method as described above, wherein, after the chlorosilane lean liquid is circulated as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is subjected to a second cooling treatment;

The low-temperature chlorosilane lean liquid after the second cooling treatment is used as an absorption medium to participate in the hydrogen chloride absorption treatment.

In the recovery method as described above, during the process in which the chlorosilane lean liquid is circulated as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is distilled to obtain a chlorosilane pure liquid.

The recovery method as described above, wherein the hydrogen chloride is subjected to a dehydrogenation treatment.

The polysilicon tail gas recovery method of the present application is to perform the first condensation treatment and the first heat exchange treatment alternately in the first condensation-heat exchange treatment of the tail gas to be recovered to gradually reduce the temperature of the tail gas to be recovered, thereby preliminarily achieving the preliminary gas-liquid separation of the tail gas to be treated, and obtaining the first condensate (a mixed liquid phase of chlorosilane and hydrogen chloride), and the first low-temperature gas (a low-temperature mixed gas phase of hydrogen, chlorosilane and hydrogen chloride). In the process of continuously entering the first condensation-heat exchange treatment of the tail gas to be recovered, the heat exchange medium (cooling medium) in the first heat exchange treatment comes from the first low-temperature gas phase of the previously fed tail gas to be recovered that has undergone the first condensation-heat exchange treatment. The present application reduces the energy consumption in the tail gas recovery process by reducing the consumption of the low-temperature cooling medium by using the first low-temperature gas phase as the heat exchange medium to participate in the first heat exchange treatment in the first condensation-heat exchange treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a device for implementing a method for recovering polysilicon tail gas provided in the present application;

FIG. 2 is a schematic diagram of an apparatus for implementing another method for recovering polysilicon tail gas provided in the present application.

Detailed ways

In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in combination with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

The recovery method of the present application is mainly used to recover the tail gas generated in the production process of polysilicon. Based on the high temperature requirement of the reduction reaction process of polysilicon production, after the reduction tail gas is utilized for thermal energy, the tail gas temperature is still above 120°C, mainly including a mixture of hydrogen, hydrogen chloride, and chlorosilane (tetrachlorosilane, trichlorosilane, dichlorodihydrosilane). The recovery method of the present application is mainly used to separate hydrogen, hydrogen chloride and chlorosilane from the tail gas with low energy consumption.

The first condensation-heat exchange treatment of the present application includes an alternating first condensation treatment and a first heat exchange treatment. The present application does not limit the specific types of the initial treatment and the final treatment in the first condensation-heat exchange treatment. In a specific embodiment, the first condensation-heat exchange treatment includes an alternating first condensation treatment and a first heat exchange treatment, and both the initial treatment and the final treatment are the first condensation treatment. The specific number of the first condensation treatment and the first heat exchange treatment in the first condensation-heat exchange treatment can be selected according to actual needs.

Taking the first condensation-heat exchange treatment including the alternating first condensation treatment and the first heat exchange treatment, and the initial treatment and the final treatment are both the first condensation treatment as an example, each time the tail gas to be recovered undergoes a first condensation treatment and a first heat exchange treatment, gas-liquid separation will occur, and the liquid phase obtained by separation at this time is the first condensate, and the gas phase continues to undergo the next level of first condensation treatment or the first heat exchange treatment until the last treatment (first condensation treatment) is completed, and the gas phase that has not been liquefied is obtained, which is the first low-temperature gas. In this process, part of the low-boiling chlorosilane and hydrogen chloride in the tail gas to be recovered are condensed and heat-exchanged to become the first condensate, so compared with the tail gas to be recovered, the purity of hydrogen in the first low-temperature gas is significantly increased.

The first low-temperature gas will circulate as a cooling medium to participate in the first heat exchange treatment, and the logistics direction of the first low-temperature gas participating in the first heat exchange treatment as a cooling medium (i.e., the flow direction of the cooling medium) is opposite to the logistics direction of the tail gas to be recovered for the first condensation-heat exchange treatment (i.e., the flow direction of the tail gas to be recovered). Specifically, in the direction opposite to the flow direction of the tail gas to be recovered, the first low-temperature gas passes through multiple first heat exchange units in sequence to cool down the gas phase in the first heat exchange units until the first low-temperature gas completes the last first heat exchange treatment.

After multiple first heat exchange treatments, the first low-temperature gas is heated to become a first purified tail gas (the chemical composition of the first purified tail gas is the same as that of the first low-temperature gas, but the temperature is higher than that of the first low-temperature gas). The first purified tail gas includes hydrogen in the tail gas to be treated and a mixed gas of chlorosilane and hydrogen chloride that has not become the first condensate, so the first purified tail gas is subjected to hydrogen separation treatment to separate the hydrogen therein.

It is obvious that the first condensation-heat exchange treatment in the recovery method of the present application can not only realize the condensation and cooling of the exhaust gas to be treated, but also effectively utilize the cold energy of the cooled gas as the cold energy supply for condensation and cooling, thereby realizing the gradient recovery and utilization of cold energy and reducing the cold energy consumption in the exhaust gas recovery process.

The present application does not limit the specific working parameters in the first condensation-heat exchange treatment, which can be determined specifically based on the working pressure and working temperature of the tail gas to be recovered from the reduction furnace (polysilicon reactor). In detail, the higher the working pressure of the tail gas to be recovered, the more conducive it is to the condensation separation of the first condensation-heat exchange unit used for the first condensation-heat exchange treatment. When the working pressure of the reduction furnace is above 0.55MPaG, the inlet pressure of the first condensation-heat exchange unit is controlled to be above 0.48MPaG. Furthermore, the pressure drop of the tail gas to be recovered in the first condensation-heat exchange unit is controlled to be within 30kpa; when the working pressure of the reduction furnace reaches 0.6MPaG, control the inlet pressure of the first condensation-heat exchange unit to be above 0.53MPaG; in the flow direction of the exhaust gas to be recovered, the working temperature of each first condensation treatment interval (i.e., the temperature of the exhaust gas after being cooled) is reduced in sequence, illustratively, 15±5℃, -10±5℃, -35±5℃, -65±5℃. The present application does not limit the cooling medium used in each first condensation treatment. For example, when the working temperature is 15±5℃, 7℃ chilled water can be selected; when the working temperature is -10±5℃, -15±5℃ Freon refrigerant or -20℃ ethylene glycol refrigerant can be selected; when the working temperature is -35±5℃, -40±5℃ Freon refrigerant can be selected; when the working temperature is -65±5℃, -70±5℃ Freon refrigerant can be selected.

Further, the performing of hydrogen separation treatment on the first purified tail gas comprises:

The compression process of the present application is used to compress and increase the pressure of the first purified tail gas, thereby facilitating the second condensation-heat exchange process.

The second condensation-heat exchange treatment of the present application includes an alternately performed second condensation treatment and a second heat exchange treatment. The present application does not limit the specific types of the initial treatment and the final treatment in the second condensation-heat exchange treatment. In a specific embodiment, the second condensation-heat exchange treatment includes an alternately performed first condensation treatment and a first heat exchange treatment, and the initial treatment is the first condensation treatment and the final treatment is the second heat exchange treatment. The present application also does not limit the specific number of the second condensation treatment and the second heat exchange treatment in the second condensation-heat exchange treatment, which can be selected according to actual needs.

Taking the second condensation-heat exchange treatment including the second condensation treatment and the second heat exchange treatment performed alternately, and the initial treatment being the second condensation treatment and the final treatment being the second heat exchange treatment as an example, when the first compressed purified tail gas undergoes each second condensation treatment and the second heat exchange treatment, gas-liquid separation will occur. At this time, the liquid phase obtained by separation is the second condensate, and the gas phase continues to undergo the second condensation treatment or the second heat exchange treatment of the next stage until the last treatment (the second heat exchange treatment) is completed to obtain the gas that has not been liquefied. Phase, that is, the second low temperature gas.

Since part of the hydrogen chloride and chlorosilane in the first compressed and purified tail gas is cooled and condensed into the second condensate in the second condensation-heat exchange treatment, hydrogen accounts for a large proportion in the second low-temperature gas. In order to separate the hydrogen from the second low-temperature gas, the second low-temperature gas obtained by the second condensation-heat exchange treatment is subjected to a hydrogen chloride absorption treatment. In the hydrogen chloride absorption treatment, the lower absorption temperature can further dissolve the hydrogen chloride in the liquefied chlorosilane, thereby completing the separation of hydrogen and obtaining hydrogen and a chlorosilane-rich liquid containing a large amount of hydrogen chloride. At this time, the separated hydrogen has a lower temperature, so it participates in the second heat exchange treatment as a cooling medium.

Specifically, hydrogen is circulated as a cooling medium to participate in the second heat exchange treatment, and the logistics direction of hydrogen as a cooling medium to participate in the second heat exchange treatment (i.e., the flow direction of hydrogen) is opposite to the logistics direction of the first compressed and purified tail gas undergoing the second condensation-heat exchange treatment (i.e., the flow direction of the first compressed and purified tail gas). In detail, in the direction opposite to the flow direction of the first compressed and purified tail gas, hydrogen is sequentially used as a cooling medium to cool the first compressed and purified tail gas in the second heat exchange treatment until the hydrogen completes the last second heat exchange treatment.

After multiple second heat exchange treatments, the hydrogen is heated up and collected for treatment. At this point, the recovery and utilization of the hydrogen in the tail gas to be recovered is basically completed.

Obviously, the above arrangement can utilize the coldness of the low-temperature hydrogen separated in the hydrogen chloride absorption treatment to perform the second condensation-heat exchange treatment on the tail gas to be recovered (more specifically, the first compressed purified tail gas), and further realize the gas-liquid separation in the tail gas to be recovered in combination with the hydrogen chloride absorption treatment, so as to obtain the second condensate, the hydrogen separated by the hydrogen chloride absorption unit, and the low-temperature chlorosilane rich liquid obtained by the hydrogen chloride absorption treatment. Thus, the step-by-step heat exchange between the high-temperature gas phase and the low-temperature hydrogen is realized, the consumption of the cooling medium for the second condensation-heat exchange treatment of the tail gas to be recovered is saved, and the hydrogen recovery in the tail gas to be recovered is realized with lower coldness consumption.

The present application does not limit the specific working parameters of the compression treatment, the second condensation-heat exchange treatment, and the hydrogen chloride absorption treatment. For example, the working pressure of the compression treatment (which can be understood as the inlet pressure of the device used to perform the compression treatment) is greater than or equal to 0.45MPaG, and the temperature is -10°C to room temperature. At this time, the molar composition of hydrogen in the gas phase is greater than 95%, and it meets the requirements for normal and stable operation of the compression treatment, and no condensation will occur during the compression process. Further, when the inlet pressure of the first condensation-heat exchange unit is above 0.53MPaG, the inlet pressure of the compression unit is 0.5MPaG; the pressure of the first compressed purified tail gas treated by the compression treatment and the inlet pressure of the second condensation-heat exchange treatment are 0.92-1.05MPaG; the hydrogen chloride absorption treatment The working pressure is 0.9-1.02MPaG; in the flow direction of the first compressed and purified exhaust gas, the target temperature of each second condensation treatment interval (the temperature of the first compressed and purified exhaust gas after being cooled) is reduced successively by the second heat exchange treatment, exemplarily, 15±5℃, -10±5℃, -35±5℃, -65±5℃; the absorption temperature of the hydrogen chloride absorption treatment is -69～-60℃.

The present application does not limit the cooling medium in each second condensation process, and for example, the cooling medium in the aforementioned first condensation process may be selected.

In order to further save energy consumption in the exhaust gas recovery process, the present application further includes, before the first compressed and purified exhaust gas is subjected to the second condensation-heat exchange treatment, subjecting the first condensate and the first compressed and purified exhaust gas to a gas-liquid heat exchange treatment, subjecting the heated first condensate to a hydrogen chloride analysis treatment, and subjecting the cooled first compressed and purified exhaust gas to the second condensation-heat exchange treatment.

Hydrogen chloride desorption treatment is mainly used to separate the mixture of hydrogen chloride and chlorosilane at high temperature by utilizing the difference in boiling points and relative volatility of components such as chlorosilane and hydrogen chloride to obtain chlorosilane-lean liquid (i.e., chlorosilane solution without hydrogen chloride) and hydrogen chloride gas phase.

Exemplarily, the working pressure of the hydrogen chloride decomposition treatment is 0.48-0.6 MPaG, and the decomposition temperature is 98-112°C.

Specifically, the first condensate is a low-temperature liquid phase, which can be used as a cooling medium to exchange heat with the first compressed and purified tail gas in the gas-liquid heat exchange process. In the gas-liquid heat exchange process, the first compressed and purified tail gas with a higher temperature (the high temperature is the result of the first heat exchange process) is heat exchanged with the low-temperature first condensate, and the first compressed and purified tail gas is subjected to the second condensation-heat exchange process after the temperature is reduced, and the first condensate is subjected to the hydrogen chloride analysis process after the temperature is increased.

The gas-liquid heat exchange treatment provides the cold energy in the first condensate to the first compressed purified tail gas that is about to enter the second condensation-heat exchange treatment, which not only saves the cold energy consumption in the second condensation-heat exchange treatment, but also increases the temperature of the first condensate used for hydrogen chloride decomposition treatment, saving the heat consumption in the hydrogen chloride decomposition treatment.

Exemplarily, after the gas-liquid heat exchange treatment, the temperature of the first condensate rises to 85-100°C and is then subjected to a hydrogen chloride decomposition treatment, and the temperature of the first compressed purified tail gas drops to below 40°C and is then subjected to a second condensation-heat exchange treatment.

In a specific embodiment, before the first condensation-heat exchange treatment, the purified hydrogen and the tail gas to be recovered are subjected to gas-to-gas heat exchange treatment, and the tail gas to be recovered after cooling is subjected to the first condensation-heat exchange treatment;

The purified hydrogen is a product obtained by subjecting the collected hydrogen to a hydrogen purification process.

As mentioned above, after the second low-temperature gas is treated by hydrogen chloride absorption, the low-temperature hydrogen obtained is used as a cooling medium for the second heat exchange treatment, and the temperature of the hydrogen is increased and collected for treatment. In order to further obtain hydrogen with higher purity, the collected hydrogen can be purified, and trace impurities in the hydrogen are adsorbed to obtain purified hydrogen.

The purified hydrogen is used as a cooling medium to cool down the exhaust gas to be recovered during the gas-to-gas heat exchange process. Subsequently, the exhaust gas to be recovered after cooling is subjected to a first condensation-heat exchange process. The purified hydrogen is collected and used after absorbing the heat of the exhaust gas to be recovered and heated up. For example, it can be used as a hydrogen reduction furnace in a polysilicon reaction.

The above-mentioned hydrogen purification treatment and gas-to-gas heat exchange treatment settings provide the cold energy of the purified hydrogen to the exhaust gas to be recovered that is about to enter the first condensation-heat exchange treatment, effectively saving the cold energy consumption of the first condensation-heat exchange unit, and further saving the energy consumption used for condensation and cooling in the exhaust gas recovery process.

Illustratively, after the gas-to-gas heat exchange treatment, the temperature of the tail gas to be recovered drops to 60-70°C, and the temperature of the purified hydrogen rises to 100-110°C.

In the process of producing polysilicon, some solid phases are inevitably mixed in the tail gas to be recovered. In order to prevent the mixed solid phases from clogging the equipment in the recovery process and causing a decrease in recovery efficiency or even equipment failure, the recovery method of the present application also includes a gas-solid separation process. Specifically, after the tail gas to be recovered is output from the polysilicon production system, it is first subjected to a gas-solid separation process. The solid phase obtained by the gas-solid separation process is discharged, and the gas phase is subjected to a gas-to-gas heat exchange process. In the gas-solid separation process, the pressure drop of the tail gas to be recovered is controlled to be below 20kpa.

Furthermore, the method further includes performing a third heat exchange treatment on the chlorosilane rich liquid and the second condensate, and performing a hydrogen chloride decomposition treatment on the heated chlorosilane rich liquid and the second condensate to obtain a chlorosilane lean liquid and hydrogen chloride;

The third heat exchange treatment refers to using heat medium to heat up the second condensate from the second condensation-heat exchange treatment and the chlorosilane rich liquid from the hydrogen chloride absorption treatment. The present application does not limit the number of the third heat exchange treatment. In order to optimize the heat exchange efficiency, the number of the third heat exchange treatment is N (N>1). That is, the third heat exchange treatment is performed multiple times on the second condensate and the chlorosilane rich liquid.

Taking the third heat exchange treatment as an example, the second condensate and the chlorosilane rich liquid are heated each time they undergo the third heat exchange treatment until the last third heat exchange treatment is completed to obtain the heated second condensate and the chlorosilane rich liquid. The heated second condensate and the chlorosilane rich liquid are used as the analysis objects of the hydrogen chloride analysis treatment, and are purified and separated in the hydrogen chloride analysis treatment to obtain high-temperature hydrogen chloride gas and high-temperature chlorosilane lean liquid. At this time, the high-temperature chlorosilane lean liquid is returned as a heat medium to participate in the third heat exchange treatment.

Specifically, the high-temperature chlorosilane lean liquid is returned as a heat medium to participate in the third heat exchange treatment, and the logistics direction of the high-temperature chlorosilane lean liquid as a heat medium to participate in the third heat exchange treatment (i.e., the flow direction of the high-temperature chlorosilane lean liquid) is opposite to the logistics direction of the second condensate and the chlorosilane rich liquid in the third heat exchange treatment (i.e., the flow direction of the second condensate and the chlorosilane rich liquid). In detail, in the direction opposite to the flow direction of the second condensate and the chlorosilane rich liquid, the high-temperature chlorosilane lean liquid serves as a heat medium to heat the second condensate and the chlorosilane rich liquid in the third heat exchange treatment until the last third heat exchange treatment is completed.

After the third heat exchange treatment, the high-temperature chlorosilane lean liquid is cooled and can then be used as an absorption medium to participate in the hydrogen chloride absorption treatment.

Obviously, the above arrangement can utilize the coldness of the second condensate and the chlorosilane rich liquid, and the heat of the chlorosilane lean liquid obtained in the hydrogen chloride decomposition treatment, to realize the step-by-step heat exchange of the high-temperature chlorosilane lean liquid, and the low-temperature second condensate and the chlorosilane rich liquid, thereby saving the heat consumption in the chlorosilane decomposition treatment and the coldness consumption in the chlorosilane absorption treatment, and realizing the recovery of hydrogen chloride and chlorosilane in the exhaust gas to be recovered with lower energy consumption.

Furthermore, when the second condensation-heat exchange treatment includes multiple second heat exchange treatments separated by second condensation treatments, and the last treatment is the second heat exchange treatment, the second condensate includes front-end condensate and rear-end condensate. The rear-end condensate refers to the liquid produced by cooling and condensing hydrogen (derived from the hydrogen chloride absorption treatment) during the last second heat exchange treatment, and the front-end condensate refers to the liquid condensed in all second condensation treatments and second heat exchange treatments except the last second heat exchange treatment.

When performing the third heat exchange treatment multiple times, the rear condensate and the chlorosilane rich liquid in the second condensate are sequentially subjected to the third heat exchange treatment multiple times, and the front condensate in the second condensate has a higher temperature than the rear condensate and the chlorosilane rich liquid. Therefore, in order to ensure the efficiency of the third heat exchange treatment, in a specific embodiment, the front condensate does not participate in the first third heat exchange treatment, but serves as the third heat exchange treatment. The logistics of the third heat exchange treatment undergoes a third heat exchange treatment with the chlorosilane lean liquid.

In order to further optimize the heat exchange network, on the basis of heat balance, the high-temperature chlorosilane lean liquid has a lower temperature after participating in the third heat exchange treatment as a heat medium. In the process of the chlorosilane lean liquid circulating as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is also subjected to a first cooling treatment.

For example, when the third heat exchange treatment is performed once, the chlorosilane-lean liquid may be subjected to a first cooling treatment before the chlorosilane-lean liquid participates in the third heat exchange treatment.

For another example, when the number of third heat exchange treatments is N, the chlorosilane-lean liquid may be subjected to a first cooling treatment before participating in the third heat exchange treatment, or after participating in at least one third heat exchange treatment and before entering the next third heat exchange treatment.

The setting of the first cooling treatment helps to output the chlorosilane lean liquid at a lower temperature after the third heat exchange treatment, thereby further optimizing the economic accounting of equipment investment and operating costs.

In addition, in the recovery method of the present application, after the chlorosilane lean liquid is circulated as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is subjected to a second cooling treatment;

The chlorosilane lean liquid after the second cooling treatment is used as an absorption medium to participate in the hydrogen chloride absorption treatment.

That is, after the chlorosilane lean liquid has completed the third heat exchange treatment, it is subjected to a second cooling treatment to further reduce its temperature, and then participates in the hydrogen chloride absorption treatment as an absorption medium.

The second cooling process is used to further cool the absorption medium in the hydrogen chloride absorption process, so as to achieve efficient hydrogen chloride absorption process. Exemplarily, after the second cooling process, the temperature of the low-temperature chlorosilane lean solution is -69°C to -60°C.

In one embodiment, the mass ratio of the chlorosilane lean solution participating in the hydrogen chloride absorption treatment to the hydrogen in the tail gas to be recovered is (20-30):1.

In another embodiment, the mass ratio of the chlorosilane lean solution participating in the hydrogen chloride absorption treatment to the tail gas to be recovered is (1.5-2):1.

The chlorosilane lean liquid output from the hydrogen chloride analysis treatment not only participates in the third heat exchange treatment as a heat medium and finally serves as an absorbent for hydrogen chloride, but also a part is sent out as a recovered chlorosilane product, which can be further treated by distillation to obtain high-purity dichlorosilane, trichlorosilane and silicon tetrachloride, which are sent to the reduction, cold hydrogenation, anti-disproportionation and other processes as raw materials to participate in polysilicon production again. Specifically, in the third heat exchange treatment, part of the chlorosilane lean liquid is sent to the distillation process as a heat medium for separation and purification In the application process, in order to make the temperature of the chlorosilane lean liquid higher than the bubble point temperature corresponding to the working pressure in the distillation process, thereby avoiding the vaporization of the chlorosilane lean liquid in the distillation process, the node where the chlorosilane lean liquid is distilled can be controlled. Specifically, when the number of the third heat exchange treatment is N, the chlorosilane lean liquid can directly enter the distillation unit for distillation after participating in the third heat exchange treatment once.

After the chlorosilane analysis treatment, the separated hydrogen chloride may still contain a small amount of hydrogen, which makes the separated hydrogen chloride gas phase difficult to liquefy, and may even affect the subsequent high-boiling cracking operation involving hydrogen chloride. Therefore, the recovery method of the present application also includes dehydrogenating the hydrogen chloride obtained by hydrogen chloride analysis and separation. Specifically, the dehydrogenation treatment element uses silicon tetrachloride as a solvent, and utilizes the difference in solubility of hydrogen and hydrogen chloride in silicon tetrachloride to achieve the separation of hydrogen chloride and hydrogen. Exemplarily, the dehydrogenation pressure of the dehydrogenation treatment is 0.47 to 0.59 MPaG.

Furthermore, before the dehydrogenation treatment is implemented, the fourth condensation-heat exchange treatment of hydrogen chloride is also included. The fourth condensation-heat exchange treatment includes a plurality of fourth condensation treatments and fourth heat exchange treatments that are performed alternately, and the specific number of the fourth condensation treatment and the fourth heat exchange treatment can be selected according to actual needs. Hydrogen chloride is cooled and condensed in the fourth condensation-heat exchange treatment, and the liquid phase obtained by condensation is mainly chlorosilane. The chlorosilane obtained by condensation can be returned to participate in the hydrogen chloride analysis treatment, and the uncondensed gas phase enters the dehydrogenation treatment as a dehydrogenation object. The silicon tetrachloride solution containing hydrogen chloride obtained by separation through the dehydrogenation treatment can be sent to participate in the cold hydrogenation reaction, or it can be sent to the slurry treatment to participate in the high-boiling cracking reaction. The hydrogen separated by the dehydrogenation treatment can be used as a cooling medium to participate in the fourth heat exchange treatment. After the fourth heat exchange treatment is completed, the heated hydrogen can be compressed together with the first low-temperature gas, and then participate in the second condensation-heat exchange treatment.

Of course, whether to set up dehydrogenation treatment depends on the use occasion and adjustment of downstream recovered hydrogen chloride. When dehydrogenation treatment is not set up, the hydrogen chloride separated by hydrogen chloride analysis treatment is directly subjected to the above-mentioned fourth condensation-heat exchange treatment. The liquid phase obtained by condensation is mainly chlorosilane, which can be returned to participate in the hydrogen chloride analysis treatment, and the uncondensed gas phase can be used as a heat exchange medium to participate in the fourth heat exchange treatment. The gas phase after heat exchange is gas phase hydrogen chloride, which can directly enter the downstream process. At this time, low boiling substances are taken out by hydrogen chloride, and high boiling substances are taken out by the recovered chlorosilane sent to the distillation treatment; low boiling substances enter the cold hydrogenation reactor with hydrogen chloride, react at high temperature and high pressure, and are discharged from the system in the subsequent dust removal unit; high boiling substances enter the distillation with the recovered chlorosilane, and after distillation separation, they enter the slurry treatment and high boiling cracking unit for further treatment.

The present application does not limit the specific device structure for each process, and all can be commonly used devices in the art. For example, the gas-solid separation process can be carried out by using a gas-solid filter, or a combination of a gas-solid filter and a cyclone dust collector in any order. In the process of gas-solid separation, the filtering and back-blowing processes can be controlled by a sequential control program; each condensation process and cooling process can be carried out by using a condenser; each heat exchange process can be carried out by using a gas-gas heat exchanger, a liquid-liquid heat exchanger or a gas-liquid heat exchanger (it can be understood that any type of heat exchanger has two independent pipelines for the heat exchange flow and the heat exchange medium to flow in reverse. During the reverse flow, the heat exchange flow and the heat exchange medium do not contact each other and only exchange heat); the compression process can be carried out by using a compressor; the hydrogen chloride absorption process can be carried out by using a hydrogen chloride absorption tower (packed tower or plate tower); the hydrogen chloride analysis process can be carried out by using a hydrogen chloride analysis tower (packed tower or plate tower); the hydrogen purification process can be carried out by using a purification adsorption tower (filled with activated carbon or other adsorbents); the distillation process can be carried out by using a distillation tower (packed tower or plate tower); the dehydrogenation process can be carried out by using a dehydrogenation tower (packed tower or plate tower).

The tail gas recovery method of the present application is used to recover the tail gas in the polysilicon production process, without material loss, and the comprehensive utilization rate of each component is 100%; each recovered material is calculated separately: the purity of hydrogen recovered in the hydrogen chloride absorption treatment is greater than 99.9% (mol), and the purity of purified hydrogen recovered after hydrogen purification treatment is greater than 99.999996% (mol); the hydrogen chloride and hydrogen contents in the chlorosilane lean solution obtained by hydrogen chloride analysis treatment are trace and undetectable; the hydrogen recovery rates in the hydrogen chloride absorption treatment are 99.8% (chloride) and 99.999996% (mol). The recovery rate of chlorosilane in the chlorosilane lean liquid sent to distillation after hydrogen chloride decomposition treatment is 99.76%, and the recovery rate of hydrogen chloride in the recovered hydrogen chloride is 100% (the combination of hydrogen chloride absorption treatment and hydrogen chloride decomposition treatment, or the combination of hydrogen chloride absorption treatment, hydrogen chloride decomposition treatment and dehydrogenation treatment is 100%, because no hydrogen chloride is detected in the hydrogen separated by dehydrogenation treatment).

Example 1

FIG1 is a schematic diagram of an apparatus for implementing a method for recovering polysilicon tail gas provided in the present application.

As shown in FIG1 , the device includes a gas-solid filter 1, a gas-gas heat exchanger 2, a first condensation-heat exchange unit, a first condensate collection tank 8, a compressor 10, a gas-liquid heat exchanger 11, a second condensation-heat exchange unit, a second condensate collection tank 18, a purification adsorption tower (not shown), a hydrogen chloride absorption tower 19, a third heat exchange unit, a first lean liquid cooler 25, a second lean liquid cooler 26, a chlorosilane refiner, and a second heat exchange unit. distillation tower (not shown), hydrogen chloride analysis tower 20, dehydrogenation tower 36, fourth condensation-heat exchange unit.

Among them, the gas-solid filter 1, the gas-gas heat exchanger 2, and the first condensation-heat exchange unit are connected end to end in sequence according to the direction of the tail gas (the feeding direction of the tail gas to be recovered); the first condensation exchange unit includes the first condenser 3, the first heat exchanger 4, the first condenser 5, the first heat exchanger 6 and the first condenser 7 which are connected end to end through the gas phase port in sequence according to the direction of the tail gas, and in the direction of the medium, the first condenser 7, the first heat exchanger 6 and the first heat exchanger 4 are connected end to end in sequence through the heat exchange medium port, and the heat exchange medium outlet of the first heat exchanger 4 is connected to the gas phase inlet of the compressor 10. In addition, the liquid phase outlets of the first condenser 3, the first heat exchanger 4, the first condenser 5, the first heat exchanger 6 and the first condenser 7 are respectively connected to the liquid phase inlet of the first condensate collection tank 8. The heat exchange medium inlet of the gas-gas heat exchanger 2 is connected to the purification outlet of the purification adsorption tower, and the heat exchange medium outlet of the gas-gas heat exchanger 2 is connected to the downstream unit that needs hydrogen (such as the reduction furnace in the figure).

The compressor 10, the gas-liquid heat exchanger 11, and the second condensation-heat exchange unit are connected end to end in the direction of the gas phase; the second condensation-heat exchange unit includes the second condenser 12, the second heat exchanger 13, the second condenser 14, the second heat exchanger 15, the second condenser 16, and the second heat exchanger 17, which are connected end to end through the gas phase port in the direction of the gas phase, and the gas phase outlet of the second heat exchanger 17 is connected to the absorption inlet of the hydrogen chloride absorption tower. In the direction of the hydrogen medium, the hydrogen outlet of the hydrogen chloride absorption tower 19, the second heat exchanger 17, the second heat exchanger 15, and the second heat exchanger 13 are connected end to end in sequence through the heat exchange medium port, and the heat exchange medium outlet of the second heat exchanger 13 is connected to the purification inlet of the purification adsorption tower. In addition, the liquid phase outlets of the second condenser 12, the second heat exchanger 13, the second condenser 14, the second heat exchanger 15, and the second condenser 16 are respectively connected to the liquid phase inlet of the second condensate collection tank 18. The liquid phase outlet of the first condensate collecting tank 8 is connected to the heat exchange medium inlet of the gas-liquid heat exchanger 11 through the pressure pump 9 , and the heat exchange medium outlet of the gas-liquid heat exchanger 11 is connected to the decomposition inlet of the hydrogen chloride decomposition tower 20 .

The rich liquid outlet of the hydrogen chloride absorption tower 19 and the liquid phase outlet of the second heat exchanger 17 are respectively connected to the chlorosilane rich liquid inlet of the third heat exchange unit. The third heat exchange unit includes a third heat exchanger 21, a third heat exchanger 22, a third heat exchanger 23, and a third heat exchanger 24, which are connected end to end through the chlorosilane rich liquid inlet in the direction of the rich liquid, and the chlorosilane rich liquid outlet of the third heat exchanger 24 is connected to the decomposition inlet of the hydrogen chloride decomposition tower 20. The liquid phase outlet of the second condensate collection tank 18 is connected to the chlorosilane rich liquid inlet of the third heat exchanger 22. In the direction of the lean liquid medium, the lean liquid outlet of the hydrogen chloride decomposition tower 20, the third heat exchanger 24, the third heat exchanger 23, the third heat exchanger 22, and the third heat exchanger 21 are connected end to end in sequence through the chlorosilane lean liquid inlet, and the chlorosilane lean liquid outlet of the third heat exchanger 21 is connected to the lean liquid inlet of the hydrogen chloride absorption tower 19. The chlorosilane lean liquid outlet of the third heat exchanger 23 is connected to the chlorosilane lean liquid inlet of the third heat exchanger 22 through the circulation pump 27 and the first lean liquid cooler 25; the chlorosilane lean liquid outlet of the third heat exchanger 24 is also connected to the distillation inlet of the chlorosilane distillation tower through the booster pump 28. In addition, the hydrogen chloride analysis tower 20 is provided with a reboiler 29.

According to the discharge direction of hydrogen chloride of the hydrogen chloride analysis tower 20, the hydrogen chloride outlet of the hydrogen chloride analysis tower 20 is connected to the fourth condensation-heat exchange unit and the dehydrogenation inlet of the dehydrogenation tower 36 in sequence. The fourth condensation-heat exchange unit includes a fourth condenser 30, a fourth heat exchanger 31, a fourth condenser 32, and a fourth condenser 33 connected in sequence through a gas phase port in the discharge direction of hydrogen chloride, and the gas phase outlet of the fourth condenser 33 is connected to the dehydrogenation inlet of the dehydrogenation tower. The hydrogen outlet of the dehydrogenation tower 36 is connected to the heat exchange medium inlet of the fourth heat exchanger 31 according to the discharge direction of hydrogen, and the heat exchange medium outlet of the fourth heat exchanger 31 is connected to the compression inlet of the compressor 10. The liquid phase outlets of the fourth heat exchanger 31, the fourth condenser 32, and the fourth condenser 33 are respectively connected to the fourth condensate collection tank 34, and the liquid phase outlet of the fourth condensate collection tank 34 is connected to the chlorosilane reflux port of the hydrogen chloride analysis tower 20 through a reflux pump 35.

After being cooled by heat exchanger 37 and condenser 38, silicon tetrachloride enters dehydrogenation tower 36, and the hydrogen chloride outlet of dehydrogenation tower 36 is connected to the heat exchange medium inlet of heat exchanger 37, so that the silicon tetrachloride hydrogen chloride solution output from dehydrogenation tower 36 is used as a cooling medium to cool the silicon tetrachloride solution. The heat exchange medium outlet of heat exchanger 37 is connected to the cold hydrogenation reactor to provide silicon tetrachloride hydrogen chloride solution to the cold hydrogenation reactor.

Specifically, after the tail gas to be recovered enters the gas-solid filter 1 for gas-solid separation, the gas phase enters the gas-to-gas heat exchanger 2 for gas-to-gas heat exchange treatment with the cold pure hydrogen from the purification adsorption tower. During the gas-to-gas heat exchange treatment, the cold pure hydrogen is heated to become hot pure hydrogen and sent to the reduction furnace to participate in the polysilicon reaction, and the gas phase after cooling enters the first condensation-heat exchange unit for the first condensation-heat exchange treatment. The first condenser 3, the first heat exchanger 4, the first condenser 5, the first heat exchanger 6 and the first condensate in the first condenser 7 enter the first condensate collection tank 8. The first low-temperature gas in the first condenser 7 serves as a cooling medium and sequentially enters the first heat exchanger 6 and the first heat exchanger 4 to participate in the first heat exchange treatment to become the first purified tail gas.

The first purified tail gas is output from the first heat exchanger 4 and enters the compression unit for compression treatment to obtain the first compressed purified tail gas. The first compressed purified tail gas undergoes gas-liquid heat exchange treatment with the first condensate from the first condensate collection tank 8. The heated first condensate enters the hydrogen chloride analysis tower 20 for hydrogen chloride analysis. The cooled first compressed purified tail gas enters the second condensation-heat exchange unit for The second condensation-heat exchange treatment, the second condensate (front condensate) in the second condenser 12, the second heat exchanger 13, the second condenser 14, the second heat exchanger 15, and the second condensate 16 enters the second condensate collection tank 18, and the second low-temperature gas in the second heat exchanger 17 enters the hydrogen chloride absorption tower 19 for hydrogen chloride absorption treatment. The low-temperature hydrogen output from the top of the hydrogen chloride absorption tower 19 enters the second heat exchanger 17, the second heat exchanger 15, and the second heat exchanger 13 in sequence as a cooling medium to participate in the second heat exchange treatment. After the second heat exchange treatment is completed, the hydrogen enters the purification adsorption tower for hydrogen purification treatment to obtain purified hydrogen. The purified hydrogen participates in the gas-to-gas heat exchange treatment in the gas-to-gas heat exchanger 2 as cold pure hydrogen.

The chlorosilane rich liquid output from the bottom of the hydrogen chloride absorption tower 19 and the condensate (rear-end condensate) output from the second heat exchanger 17 enter the third heat exchange unit for the third heat exchange treatment. The chlorosilane rich liquid and the rear-end condensate pass through the third heat exchanger 21, the third heat exchanger 22, the third heat exchanger 23, and the third heat exchanger 24 in sequence, and undergo the third heat exchange treatment with the chlorosilane lean liquid from the bottom of the hydrogen chloride decomposition tower 20 in the third heat exchanger 21, the third heat exchanger 22, the third heat exchanger 23, and the third heat exchanger 24. The chlorosilane rich liquid and the rear-end condensate are heated and enter the hydrogen chloride decomposition tower 20, and undergo hydrogen chloride decomposition treatment in the hydrogen chloride decomposition tower 20 together with the first condensate after the gas-liquid heat exchange treatment. The chlorosilane lean liquid output from the bottom of the hydrogen chloride analysis tower 20 enters the third heat exchanger 24, the third heat exchanger 23, the third heat exchanger 22 and the third heat exchanger 21 as a heat medium in sequence to participate in the third heat exchange treatment, wherein, after the chlorosilane lean liquid is output through the heat exchange medium outlet of the third heat exchanger 23, it enters the first lean liquid cooler 15 through the action of the circulation pump 27 for the first cooling treatment, and then enters the third heat exchanger 22 for the third heat exchange treatment. After the chlorosilane lean liquid is output through the third heat exchanger 21, it enters the second lean liquid cooler 26 for the second cooling treatment, and then enters the hydrogen chloride absorption tower 19 as an absorption medium to participate in the hydrogen chloride absorption treatment.

In addition, the front condensate in the second condensate collection tank 18 enters through the liquid phase inlet of the third heat exchanger 22 and continues to exchange heat after being mixed with the chlorosilane rich liquid and the rear condensate.

The hydrogen chloride outputted from the top of the hydrogen chloride decomposition tower 20 enters the fourth condensation-heat exchange unit for the fourth condensation-heat exchange treatment. The condensate in the fourth heat exchanger 31, the fourth condenser 32, and the fourth condenser 33 enters the fourth condensate collection tank 34, and then under the action of the reflux pump 35, enters the hydrogen chloride decomposition tower 20 through the fourth condensate collection tank 34 for hydrogen chloride decomposition treatment, and the gas phase outputted from the fourth condenser 33 enters the dehydrogenation tower 36 for dehydrogenation treatment.

Silicon tetrachloride passes through heat exchanger 37 and condenser 38 for cooling before entering dehydrogenation tower 36 for dehydrogenation. The hydrogen gas output from the top of dehydrogenation tower 36 enters fourth cooler 31 as cooling medium for dehydrogenation. After the fourth condensation-heat exchange treatment, it enters the compression unit 10. The hydrogen chloride and silicon chloride mixed liquid output from the bottom of the dehydrogenation tower 36 is used as the cooling medium of the heat exchanger 37 to cool the tetrachlorosilane under the action of the pressure pump 39, and then sent to the cold hydrogenation reactor.

Example 2

The device shown in FIG. 2 is substantially the same as the device shown in FIG. 1 , except that the device in FIG. 2 does not include a dehydrogenation tower.

Specifically, according to the discharge direction of hydrogen chloride of the hydrogen chloride analysis tower 20, the hydrogen chloride outlet of the hydrogen chloride analysis tower 20 is connected to the fourth condensation-heat exchange unit in sequence. The fourth condensation-heat exchange unit includes a fourth condenser 30, a fourth heat exchanger 31, a fourth condenser 32, a fourth condenser 33, and a fourth condenser 36, which are connected to each other in sequence through a gas phase port in the discharge direction of hydrogen chloride, and the gas phase outlet of the fourth condenser 36 is connected to the heat exchange medium inlet of the fourth heat exchanger 31, and the heat exchange medium outlet of the fourth heat exchanger 31 is connected to the cold hydrogenation unit to provide hydrogen chloride to the cold hydrogenation unit. The liquid phase outlets of the fourth heat exchanger 31, the fourth condenser 32, the fourth condenser 33, and the fourth condenser 36 are respectively connected to the fourth condensate collection tank 34, and the liquid phase outlet of the fourth condensate collection tank 34 is connected to the chlorosilane reflux port of the hydrogen chloride analysis tower 20 through a reflux pump 35.

The difference of the recovery method of Example 2 is that the hydrogen chloride output from the top of the hydrogen chloride analysis tower 20 enters the fourth condensation-heat exchange unit for the fourth condensation-heat exchange treatment. The condensate in the fourth heat exchanger 31, the fourth condenser 32, and the fourth condenser 33 enters the fourth condensate collection tank 34, and then under the action of the driving pump 35, enters the hydrogen chloride analysis tower 20 through the fourth condensate collection tank 34 for hydrogen chloride analysis treatment, and the gas phase output from the fourth condenser 36 enters the fourth heat exchanger 31 as a cooling medium to participate in the fourth condensation-heat exchange treatment, and then enters the cold hydrogenation reactor.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

A method for recovering polysilicon tail gas comprises the following steps:

Performing a first condensation-heat exchange treatment on the tail gas to be recovered to obtain a first condensate and a first low-temperature gas; the first condensation-heat exchange treatment includes alternating first condensation treatment and first heat exchange treatment;

After the first low-temperature gas is circulated as a cooling medium to participate in the first heat exchange treatment, the first low-temperature gas is heated to become a first purified tail gas, and a hydrogen separation treatment is performed on the first purified tail gas;

The logistics direction of the first low-temperature gas as a cooling medium participating in the first heat exchange treatment is opposite to the logistics direction of the tail gas to be recovered undergoing the first condensation-heat exchange treatment.
The recovery method according to claim 1, wherein the steps of: performing hydrogen separation treatment on the first purified tail gas comprises:

compressing the first purified tail gas to obtain first compressed purified tail gas;

Performing a second condensation-heat exchange treatment on the first compressed and purified tail gas to obtain a second condensate and a second low-temperature gas; the second condensation-heat exchange treatment includes alternating second condensation treatment and second heat exchange treatment;

The second low-temperature gas is subjected to hydrogen chloride absorption treatment to obtain hydrogen gas and chlorosilane-rich liquid;

The hydrogen is used as a cooling medium to participate in the second heat exchange process and then collected and processed;

The logistics direction of the hydrogen as a cooling medium participating in the second heat exchange treatment is opposite to the logistics direction of the first purified tail gas undergoing the second condensation-heat exchange treatment.
The recovery method according to claim 2, wherein the second condensation-heat exchange treatment comprises:

The first condensate and the first compressed purified tail gas are subjected to a gas-liquid heat exchange treatment, the first condensate after the temperature is increased is subjected to a hydrogen chloride analysis treatment, and the first compressed purified tail gas after the temperature is decreased is subjected to the second condensation-heat exchange treatment.
The recovery method according to claim 2 or 3, wherein before the first condensation-heat exchange treatment, it also includes subjecting the purified hydrogen to gas-to-gas heat exchange treatment with the tail gas to be recovered, and subjecting the tail gas to be recovered after cooling to the first condensation-heat exchange treatment;

The purified hydrogen is a product obtained by subjecting the collected hydrogen to a hydrogen purification process.
The recovery method according to claim 4, wherein before the gas-to-gas heat exchange treatment, it also includes performing gas-solid separation treatment on the tail gas to be recovered;

The gas phase obtained by the gas-solid separation process is subjected to the gas-gas heat exchange process.
The recovery method according to any one of claims 2 to 5, wherein the chlorosilane rich liquid and the second condensate are subjected to a third heat exchange treatment, and the heated chlorosilane rich liquid and the second condensate are subjected to a hydrogen chloride decomposition treatment to obtain a chlorosilane lean liquid and hydrogen chloride;

Circulating the chlorosilane lean liquid as a heat medium to participate in the third heat exchange treatment;

The logistics direction of the chlorosilane lean liquid as a heat medium circulating in the third heat exchange treatment is opposite to the logistics direction of the chlorosilane rich liquid and the second condensate in the third heat exchange treatment.
The recovery method according to claim 6, wherein, during the process in which the chlorosilane lean liquid is circulated as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is subjected to a first cooling treatment.
The recovery method according to claim 6 or 7, wherein after the chlorosilane lean liquid is circulated as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is subjected to a second cooling treatment;

The low-temperature chlorosilane lean liquid after the second cooling treatment is used as an absorption medium to participate in the hydrogen chloride absorption treatment.
The recovery method according to any one of claims 6 to 8, wherein, during the process in which the chlorosilane lean liquid is circulated as a heat medium to participate in the third heat exchange treatment, the chlorosilane lean liquid is distilled to obtain a chlorosilane pure liquid.
The recovery method according to claim 6, wherein the hydrogen chloride is subjected to a dehydrogenation treatment.