Method and system for recycling polycrystalline silicon slag liquid

Abstract

The invention provides a method and a system for recovering polycrystalline silicon slag liquid. The recycling method of the polycrystalline silicon slag liquid comprises the following steps: carrying out distillation treatment on the slag liquid by using a clear liquid distillation tower to obtain a high-boiling-point substance and a low-boiling-point substance; carrying out condensation treatment on the low-boiling-point substance by using a clear liquid distillation tower condenser to obtain recovered chlorosilane; in the clear liquid distillation tower, the tower top temperature is 60-90 DEG C, the tower top pressure is 0.02-0.2 MPaG, the tower kettle temperature is 100-160 DEG C, and the tower kettle pressure is 0.05-0.3 MPaG. According to the recycling method, high value-added components in the polycrystalline silicon slag slurry can be separated, resources are saved, and the recycling method is easy to operate and high in separation efficiency.

Description

Technical Field

[0001] The invention relates to a method and system for recovering polysilicon slag liquid, belonging to the technical field of chemical separation. Background Art

[0002] With the increase in demand, the photovoltaic industry and the integrated circuit industry have developed rapidly. Polysilicon is the core raw material of the photovoltaic industry and the integrated circuit industry, so more and more companies have begun to produce polysilicon.

[0003] At present, almost all polysilicon production enterprises adopt the modified Siemens process, and a large amount of slurry will be generated in the process of producing polysilicon by the modified Siemens process. For example, a certain amount of slurry will be generated in the chlorine hydrogen chemical section of polysilicon production. The slurry mainly includes chlorosilane, silicon powder and metal chloride (for example, AlCl 3 ), etc. The treatment and utilization of slag slurry is a difficult problem that the polysilicon industry must face. At present, there are two main processes for treating slag slurry in the chlorine hydrogen chemical industry. One is to subject the slag slurry to extensive hydrolysis treatment, which results in a large amount of chlorosilane material waste and causes environmental pollution; the other is to send part of the material to a vacuum drum filter, and use the adsorption layer formed by a mixture of diatomaceous earth and chlorosilane to separate the solid and liquid. The separated solid phase is simply treated and sent to the hydrolysis system for treatment, and the liquid phase is further purified and recycled. This method requires high control accuracy and is very likely to cause the adsorption layer to fall off. The device has a short operating time and a high maintenance frequency, which poses a great safety hazard and increases the workload of personnel. In addition, the filtering and adsorption effects of the device are poor, the recovery rate is low, and the high value-added components in the slag slurry are not separated, resulting in serious waste of resources. Summary of the invention

[0004] The invention provides a method for recovering polysilicon slag liquid. The method can separate high value-added components in polysilicon slag slurry, saving resources, and the method is simple to operate and has high separation efficiency.

[0005] The present invention provides a polysilicon slag liquid recovery system, which is used to implement the above recovery method. The recovery system can separate high value-added components in the polysilicon slag slurry, and the recovery system has a simple structure and is suitable for wide promotion and application.

[0006] The present invention provides a method for recovering polysilicon slag liquid, which comprises the following steps:

[0007] Use a clear liquid distillation tower to distill the slag liquid to obtain high-boiling substances and low-boiling substances;

[0008] Using a clear liquid distillation tower condenser to condense low boiling points to obtain recovered chlorosilane;

[0009] In the clear liquid distillation tower, the tower top temperature is 60-90°C, and the tower top pressure is 0.02-0.2MPaG.

[0010] The tower bottom temperature is 100-160°C, and the tower bottom pressure is 0.05-0.3MPaG.

[0011] In the above recovery method, the slag liquid comprises, in terms of mass percentage, 80-99% of chlorosilane and 5-20% of high boiling substances.

[0012] The recovery method as described above, wherein the slag liquid is further subjected to preheating treatment, wherein the preheating treatment comprises:

[0013] In the clear liquid preheater, the slag liquid is preheated by using the low boiling substances.

[0014] The recovery method as described above, wherein the temperature during the condensation process is 40-80° C.; and / or,

[0015] During the preheating treatment, the temperature is 40-100°C.

[0016] The recovery method as described above, wherein, further comprises subjecting the recovered chlorosilane to a cold hydrogenation process.

[0017] The recovery method as described above, wherein, further comprises allowing the recovered chlorosilane to enter the clear liquid distillation tower for distillation treatment.

[0018] The recovery method as described above, wherein, further comprises allowing the recovered chlorosilane to enter a flash tank for flash evaporation treatment.

[0019] The recovery method as described above, wherein, further comprises: allowing the recovered chlorosilane to enter a clear liquid distillation condensate tank, using a clear liquid distillation condensate pump to transport the recovered chlorosilane in the clear liquid distillation condensate tank to cold hydrogenation; and / or,

[0020] The recovered chlorosilane is allowed to enter a clear liquid distillation condensate tank, and a clear liquid distillation condensate pump is used to transport the recovered chlorosilane in the clear liquid distillation condensate tank to the clear liquid distillation tower; and / or,

[0021] The recovered chlorosilane is allowed to enter a clear liquid distillation condensate tank, and a clear liquid distillation condensate pump is used to transport the recovered chlorosilane in the clear liquid distillation condensate tank to a flash tank.

[0022] In the recovery method as described above, the temperature in the clear liquid distillation condensate pump is 40-60°C and the pressure is 0.8-2.0MPaG.

[0023] The present invention provides a polysilicon slag liquid recovery system, wherein the recovery system is used to implement the recovery method as described above;

[0024] The recovery system comprises: a clear liquid distillation tower and a clear liquid distillation tower condenser;

[0025] The clear liquid distillation tower has a slag liquid inlet, and the top outlet of the clear liquid distillation tower is communicated with the inlet of the clear liquid distillation tower condenser.

[0026] The present invention provides a method for recovering polysilicon slag liquid, wherein the method uses a clear liquid distillation tower to distill the slag liquid to obtain high-boiling products and low-boiling products, and then condenses the low-boiling products obtained by the distillation process to obtain recovered chlorosilane. The recovery method can separate high value-added components in polysilicon slag slurry (obtaining recovered chlorosilane), save resources, and the recovery method is simple to operate and has a high separation efficiency. In addition, compared with using a still for distillation, using a clear liquid distillation tower for distillation has higher continuity and lower operating temperature, and can improve separation efficiency while saving energy consumption.

[0027] The present invention provides a polysilicon slag liquid recovery system, which is used to implement the above recovery method. The recovery system can separate high value-added components in the polysilicon slag slurry, and the recovery system has a simple structure and is suitable for wide promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 Schematic diagram of the recovery process of polysilicon slag liquid in some embodiments of the present invention.

[0030] Description of reference numerals:

[0031] 1: clear liquid distillation tower;

[0032] 2: Condenser of clear liquid distillation tower;

[0033] 3: clear liquid distillation condensate tank;

[0034] 4: Reboiler;

[0035] 5: High boiling pot;

[0036] 6: Clear liquid preheater;

[0037] 7: Clear liquid distillation condensate pump. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Figure 1 Schematic diagram of the recovery process of polysilicon slag liquid in some embodiments of the present invention. Figure 1 As shown, the first aspect of the present invention provides a method for recovering polysilicon slag liquid, comprising the following steps:

[0040] The slag liquid is distilled using a clear liquid distillation tower 1 to obtain high boiling products and low boiling products;

[0041] Using the clear liquid distillation tower condenser 2 to condense the low boiling point to obtain recovered chlorosilane;

[0042] In the clear liquid distillation tower, the top temperature is 60-90°C, the top pressure is 0.02-0.2MPaG, the bottom temperature is 100-160°C, and the bottom pressure is 0.05-0.3MPaG.

[0043] In the process of polysilicon production, a large amount of slurry is generated, and the slurry mainly includes high boiling substances, silicon powder, chlorosilane and others. In actual production, the slag liquid of the present invention can be obtained by separating the silicon powder in the slurry, that is, the slag liquid of the present invention mainly includes high boiling substances and chlorosilane, and also includes a very small amount of silicon powder and other components.

[0044] The recovery method of the present invention specifically comprises: using a clear liquid distillation tower 1 to distill the slag liquid to separate high-boiling substances and low-boiling substances in the slag liquid, wherein the high-boiling substances flow downward and are output from the bottom of the clear liquid distillation tower 1, and the low-boiling substances flow upward and are output from the top of the clear liquid distillation tower 1;

[0045] Then, the low-boiling substances output from the top of the clear liquid distillation tower 1 are condensed using the clear liquid distillation tower condenser 2 to obtain recovered chlorosilane, which can be reused.

[0046] In some embodiments, the bottom of the clear liquid distillation tower 1 is further provided with a reboiler 4, which is used to provide energy to the clear liquid distillation tower 1. The high boiling products output from the bottom of the clear liquid distillation tower 1 can be stored in a high boiling tank 5, and then converted into high boiling products, and useful components in the high boiling products can be further recovered to improve the recycling efficiency of resources.

[0047] Illustratively, in the clear liquid distillation tower, the tower top temperature may be any one of 60°C, 70°C, 75°C, 80°C, 85°C, 90°C, and a range consisting of any two thereof, and the tower top pressure may be any one of 0.02 MPaG, 0.03 MPaG, 0.05 MPaG, 0.07 MPaG, 0.1 MPaG, 0.15 MPaG, 0.2 MPaG, and a range consisting of any two thereof;

[0048] The bottom temperature can be any one of 100°C, 105°C, 115°C, 125°C, 130°C, 140°C, 150°C, 160°C, or a range consisting of any two thereof, and the bottom pressure can be any one of 0.05MPaG, 0.07MPaG, 0.1MPaG, 0.15MPaG, 0.2MPaG, 0.25MPaG, 0.3MPaG, or a range consisting of any two thereof.

[0049] The recovery method of the present invention can separate high value-added components in polysilicon slag slurry (obtaining recovered chlorosilane), save resources, and the recovery method is simple to operate and has high separation efficiency. Compared with the distillation treatment using a distillation kettle, the distillation treatment using a clear liquid distillation tower 1 has high continuity and low operating temperature, and can improve the separation efficiency while saving energy consumption.

[0050] In some embodiments of the present invention, when the slag liquid comprises, by mass percentage, 80-99% chlorosilane and 5-20% high boiling substances, the recovery method can more efficiently recover the chlorosilane in the slag liquid and improve resource utilization.

[0051] In some embodiments of the present invention, the recovery method further comprises preheating the slag liquid, and the preheating treatment comprises:

[0052] In the clear liquid preheater 6, the slag liquid is preheated by using low boiling substances.

[0053] Specifically, the recovery method also includes: allowing the low boiling point substance to be output through the top outlet of the clear liquid distillation tower 1, entering the clear liquid preheater 6 through the heat source inlet of the clear liquid preheater 6, allowing the slag liquid to enter the clear liquid preheater 6 through the cold source inlet of the clear liquid preheater 6, in the clear liquid preheater 6, the low boiling point substance and the slag liquid exchange heat to achieve preheating treatment of the slag liquid, the obtained preheated slag liquid enters the clear liquid distillation tower 1 through the slag liquid inlet of the clear liquid distillation tower 1 for distillation treatment, and the low boiling point substance cooled by the clear liquid preheater 6 enters the clear liquid distillation tower condenser 2 for condensation treatment to obtain recovered chlorosilane.

[0054] It can be understood that the low-boiling substances output from the top of the clear liquid distillation tower 1 usually have a higher temperature. The present invention uses low-boiling substances with a higher temperature to preheat the slag liquid, which can utilize the heat of the low-boiling substances and save energy consumption; and the low-boiling substances enter the clear liquid distillation tower condenser 2 after the slag liquid is cooled, which can reduce the load of the clear liquid distillation tower condenser 2 and further save energy consumption; at the same time, by preheating the slag liquid to make the slag liquid have a certain temperature, and then transporting the preheated slag liquid to the clear liquid distillation tower 1 for distillation treatment, the efficiency of the distillation treatment can be improved, thereby more efficiently separating high-boiling substances and low-boiling substances.

[0055] The inventors also found in their research that when the temperature during the condensation process is 40-80°C, low-boiling substances can be more fully condensed into recovered chlorosilanes while saving energy, thereby increasing the yield of recovered chlorosilanes.

[0056] Illustratively, during the condensation process, the temperature may be any one of 40° C., 50° C., 60° C., 70° C., 75° C., and 80° C., or a range consisting of any two of them.

[0057] When the temperature is 40-100°C during the preheating treatment, the heat of low-boiling substances can be more fully utilized to save energy; and the slag liquid can be fully preheated to improve the efficiency of the distillation treatment.

[0058] Illustratively, during the preheating treatment, the temperature may be any one of 40° C., 50° C., 60° C., 70° C., 75° C., 80° C., 90° C., and 100° C., or a range consisting of any two of these.

[0059] In some embodiments of the present invention, the recovery method further comprises allowing the recovered chlorosilane to enter a cold hydrogenation process to participate in a cold hydrogenation reaction to achieve resource recycling.

[0060] Specifically, the process also includes: allowing the recovered chlorosilane to enter the clear liquid distillation condensate tank 3, and using the clear liquid distillation condensate pump 7 to transport the recovered chlorosilane in the clear liquid distillation condensate tank 3 to the cold hydrogenation.

[0061] The recovery method of the present invention further comprises: allowing the recovered chlorosilane to be output through the outlet of the clear liquid distillation tower condenser 2, entering the clear liquid distillation condensate tank 3 through the inlet of the clear liquid distillation condensate tank 3, and being stored in the clear liquid distillation condensate tank 3; then using the clear liquid distillation condensate pump 7 to pump out the recovered chlorosilane stored in the clear liquid distillation condensate tank 3, allowing the recovered chlorosilane to enter the cold hydrogenation to participate in the cold hydrogenation reaction, thereby realizing the reuse of the recovered chlorosilane.

[0062] In some embodiments of the present invention, the recovery method further comprises allowing the recovered chlorosilane to enter the clear liquid distillation tower 1 for distillation treatment.

[0063] In the present invention, the recovered chlorosilane obtained can be again sent to the clear liquid distillation tower 1 for distillation treatment to further remove high boiling points and other components in the recovered chlorosilane, thereby improving the purity of the recovered chlorosilane.

[0064] Specifically, the method further includes: allowing the recovered chlorosilane to enter the clear liquid distillation condensate tank 3 , and using the clear liquid distillation condensate pump 7 to transport the recovered chlorosilane in the clear liquid distillation condensate tank to the clear liquid distillation tower 1 .

[0065] The recovery method of the present invention further comprises: allowing the recovered chlorosilane to be output through the outlet of the clear liquid distillation tower condenser 2, entering the clear liquid distillation condensate tank 3 through the inlet of the clear liquid distillation condensate tank 3, and being stored in the clear liquid distillation condensate tank 3; then using the clear liquid distillation condensate pump 7 to pump out the recovered chlorosilane stored in the clear liquid distillation condensate tank 3, allowing the recovered chlorosilane to enter the clear liquid distillation tower 1, and participate in the distillation reaction again, so as to further remove high boiling points and other components in the recovered chlorosilane, and improve the purity of the recovered chlorosilane.

[0066] In some embodiments of the present invention, the recovered chlorosilane may be fed into a flash tank for flash treatment.

[0067] In the present invention, the recovered chlorosilane is put into a flash tank for flash treatment to further remove silicon powder in the recovered chlorosilane and improve the purity of the recovered chlorosilane.

[0068] Specifically, the recovered chlorosilane is allowed to enter the clear liquid distillation condensate tank 3 , and the clear liquid distillation condensate pump 7 is used to transport the recovered chlorosilane in the clear liquid distillation condensate tank 3 to the flash tank.

[0069] The recovery method of the present invention further comprises: allowing the recovered chlorosilane to be output through the outlet of the clear liquid distillation tower condenser 2, entering the clear liquid distillation condensate tank 3 through the inlet of the clear liquid distillation condensate tank 3, and being stored in the clear liquid distillation condensate tank 3; then using the clear liquid distillation condensate pump 7 to pump out the recovered chlorosilane stored in the clear liquid distillation condensate tank 3, allowing the recovered chlorosilane to enter the flash tank for flash treatment, so as to further remove the silicon powder in the recovered chlorosilane and improve the purity of the recovered chlorosilane.

[0070] Furthermore, when the clear liquid is distilled in the condensate pump 7, the temperature is 40-60° C. and the pressure is 0.8-2.0 MPaG, the recovered chlorosilane can be better reused.

[0071] For example, in the clear liquid distillation condensate pump 7, the temperature may be 40°C, 50°C, 55°C, 60°C, or any one of them or a range consisting of any two thereof;

[0072] The pressure may be any one of 0.8 MPaG, 1 MPaG, 1.2 MPaG, 1.3 MPaG, 1.5 MPaG, and 2.0 MPaG, or a range consisting of any two of them.

[0073] A second aspect of the present invention provides a polysilicon slag liquid recovery system, the recovery system is used to implement the recovery method of the first aspect;

[0074] The recovery system comprises: a clear liquid distillation tower 1 and a clear liquid distillation tower condenser 2;

[0075] The clear liquid distillation tower 1 has a slag liquid inlet, and the top outlet of the clear liquid distillation tower 1 is connected to the inlet of the clear liquid distillation tower condenser 2.

[0076] Specifically, the slag liquid enters the clear liquid distillation tower 1 through the slag liquid inlet of the clear liquid distillation tower 1, and is distilled in the clear liquid distillation tower 1 to obtain high boiling products and low boiling products. The obtained high boiling products are output through the tower bottom outlet of the clear liquid distillation tower 1, and the obtained low boiling products are output through the tower top outlet of the clear liquid distillation tower 1, and enter the clear liquid distillation tower condenser 2 through the inlet of the clear liquid distillation tower condenser 2. The low boiling products are cooled in the clear liquid distillation tower condenser 2 to obtain recovered chlorosilane.

[0077] The recovery system of the present invention is used to implement the above recovery method. The recovery system can separate high value-added components in polysilicon slag slurry, and the recovery system has a simple structure and is suitable for wide promotion and application.

[0078] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0079] Example 1

[0080] The polysilicon slag liquid recovery system of this embodiment is as follows Figure 1 As shown, it includes: a clear liquid distillation tower 1, a clear liquid distillation tower condenser 2, a clear liquid preheater 6, a clear liquid distillation condensate tank 3, a clear liquid distillation condensate pump 7, a reboiler 4 and a high boiling tank 5;

[0081] The clear liquid distillation tower 1 has a slag liquid inlet;

[0082] The top outlet of the clear liquid distillation tower 1 is communicated with the heat source inlet of the clear liquid preheater 6, the slag liquid enters the clear liquid preheater 6 through the cold source inlet of the clear liquid preheater 6, the heat source outlet of the clear liquid preheater 6 is communicated with the inlet of the clear liquid distillation tower condenser 2, the outlet of the clear liquid distillation tower condenser 2 is communicated with the inlet of the clear liquid distillation condensate tank 3, the outlet of the clear liquid distillation condensate tank 3 is communicated with the inlet of the clear liquid distillation condensate pump 7, the outlet of the clear liquid distillation condensate pump 7 is communicated with a pipeline, the first outlet of the pipeline is communicated with the cold hydrogenation process, the second outlet of the pipeline is communicated with the inlet of the clear liquid distillation tower 1, and the third outlet of the pipeline is communicated with the flash tank;

[0083] The bottom outlet of the clear liquid distillation tower 1 is communicated with the reboiler 4, and the bottom outlet of the clear liquid distillation tower 1 is communicated with the high boiling tank 5;

[0084] In the clear liquid distillation tower, the top temperature was 65°C, the top pressure was 0.04 MPaG, the bottom temperature was 103°C, and the bottom pressure was 0.06 MPaG.

[0085] Example 2

[0086] The method for recovering polysilicon slag liquid in this embodiment is carried out using the recovery system of Embodiment 1, and specifically comprises:

[0087] The slag liquid is used to enter the slag liquid distillation tower through the slag liquid inlet of the clear liquid distillation tower 1, and the slag liquid is distilled to obtain high-boiling products and low-boiling products, wherein the high-boiling products flow downward, are output through the tower kettle outlet of the clear liquid distillation tower 1, and enter the high-boiling tank 5 through the inlet of the high-boiling tank 5 for storage, and the reboiler 4 of the tower kettle of the clear liquid distillation tower 1 is used to provide energy for the clear liquid distillation tower 1;

[0088] The low boiling substances go upward, are outputted from the top of the clear liquid distillation tower 1, and enter the clear liquid preheater 6 through the heat source inlet of the clear liquid preheater 6. The slag liquid enters the clear liquid preheater 6 through the cold source inlet of the clear liquid preheater 6. In the clear liquid preheater 6, the low boiling substances and the slag liquid exchange heat to achieve preheating treatment of the slag liquid. The obtained preheated slag liquid enters the clear liquid distillation tower 1 through the slag liquid inlet of the clear liquid distillation tower 1 for distillation treatment. The low boiling substances cooled by the clear liquid preheater 6 enter the clear liquid distillation tower condenser 2 for condensation treatment to obtain recovered chlorosilane;

[0089] The recovered chlorosilane is outputted through the outlet of the clear liquid distillation tower condenser 2, enters the clear liquid distillation condensate tank 3 through the inlet of the clear liquid distillation condensate tank 3, and is stored in the clear liquid distillation condensate tank 3. The recovered chlorosilane stored in the clear liquid distillation condensate tank 3 is pumped out using a clear liquid distillation condensate pump 7, and the recovered chlorosilane enters the flash tank, the recovered chlorosilane enters the clear liquid distillation tower 1, and the recovered chlorosilane enters the cold hydrogenation process;

[0090] The slag liquid includes, by mass percentage: 90% chlorosilane and 10% high boiling substances;

[0091] In the clear liquid distillation tower, the tower top temperature is 65°C, the tower top pressure is 0.04MPaG, the tower bottom temperature is 103°C, and the tower bottom pressure is 0.06MPaG;

[0092] During the condensation process, the temperature is 45°C;

[0093] During the preheating treatment, the temperature was 61°C;

[0094] In the clear liquid distillation condensate pump 7, the temperature is 45°C and the pressure is 1.5 MPaG.

[0095] Comparative Example

[0096] The method for recovering the polysilicon slag liquid in this comparative example is basically the same as that in Example 2, except that:

[0097] The distillation treatment was carried out using an evaporator. During the distillation treatment, the temperature was 180° C. and the pressure was 0.4 MPaG.

[0098] After testing, the recovery rate of the light component chlorosilane in Example 2 can reach more than 98%. The top distillate of the clear liquid distillation tower mainly contains 97wt% of silicon tetrachloride and 2wt% of trichlorosilane, as well as trace amounts of other light components and high boiling products. Under the condition of consuming the same heat source, the comparative example can only concentrate the high boiling products to 60%, while more light component chlorosilane is extracted from the tower bottom, and the recovery rate of chlorosilane is poor. The reason is that the heat exchange efficiency of the evaporator is not as high as that of the reboiler. Under the condition of processing the same materials, the requirements for steam consumption and equipment are higher, and the processing efficiency is lower.

[0099] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for recovering polysilicon slag liquid, characterized in that: The following steps are involved: Use a clear liquid distillation tower to distill the slag liquid to obtain high-boiling substances and low-boiling substances; Using a clear liquid distillation tower condenser to condense low boiling points to obtain recovered chlorosilane; In the clear liquid distillation tower, the top temperature is 60-90°C, the top pressure is 0.02-0.2MPaG, the bottom temperature is 100-160°C, and the bottom pressure is 0.05-0.3MPaG.

2. The recycling method according to claim 1, characterized in that: The slag liquid comprises, in terms of mass percentage, 80-99% of chlorosilane and 5-20% of high boiling substances.

3. The recovery method according to claim 1 or 2, characterized in that: The slag liquid is also subjected to a preheating treatment, wherein the preheating treatment comprises: In the clear liquid preheater, the slag liquid is preheated by using the low boiling point substances.

4. The recycling method according to claim 3, characterized in that: During the condensation process, the temperature is 40-80°C; and / or, During the preheating treatment, the temperature is 40-100°C.

5. The recycling method according to any one of claims 1 to 4, characterized in that: The method also includes allowing the recovered chlorosilane to enter a cold hydrogenation process.

6. The recycling method according to any one of claims 1 to 5, characterized in that: The method also includes allowing the recovered chlorosilane to enter the clear liquid distillation tower for distillation treatment.

7. The recycling method according to any one of claims 1 to 6, characterized in that: The method also includes allowing the recovered chlorosilane to enter a flash tank for flash treatment.

8. The recycling method according to any one of claims 4 to 7, characterized in that: Also includes: The recovered chlorosilane is allowed to enter a clear liquid distillation condensate tank, and a clear liquid distillation condensate pump is used to transport the recovered chlorosilane in the clear liquid distillation condensate tank to cold hydrogenation; and / or, The recovered chlorosilane is allowed to enter a clear liquid distillation condensate tank, and a clear liquid distillation condensate pump is used to transport the recovered chlorosilane in the clear liquid distillation condensate tank to the clear liquid distillation tower; and / or, The recovered chlorosilane is allowed to enter a clear liquid distillation condensate tank, and a clear liquid distillation condensate pump is used to transport the recovered chlorosilane in the clear liquid distillation condensate tank to a flash tank.

9. The recycling method according to claim 8, characterized in that: In the clear liquid distillation condensate pump, the temperature is 40-60°C and the pressure is 0.8-2.0MPaG.

10. A polysilicon slag liquid recovery system, characterized in that: The recycling system is used to implement the recycling method according to any one of claims 1 to 9; The recovery system comprises: a clear liquid distillation tower and a clear liquid distillation tower condenser; The clear liquid distillation tower has a slag liquid inlet, and the top outlet of the clear liquid distillation tower is communicated with the inlet of the clear liquid distillation tower condenser.

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