Recycling system and method for polycrystalline silicon slag slurry

Abstract

The invention provides a system and a method for recycling polycrystalline silicon slag slurry. The polycrystalline silicon slag slurry recovery system comprises a flash tank, a settling tank, a drying machine, a drying machine condenser, a washing tower and a clear liquid tank, slag slurry enters the flash tank through an inlet of the flash tank, a gas phase outlet of the flash tank is communicated with an inlet of the clear liquid tank, a solid-liquid mixture outlet of the flash tank is communicated with an inlet of the settling tank, and a solid-liquid mixture outlet of the settling tank is communicated with an inlet of the drying machine. An outlet of the clear liquid tank is communicated with a liquid phase inlet of the washing tower, a gas phase outlet of the drying machine is communicated with a gas phase inlet of the washing tower, a liquid phase outlet of the washing tower is communicated with an inlet of the clear liquid tank, a gas phase outlet of the washing tower is communicated with an inlet of the drying machine condenser, and an outlet of the drying machine condenser is communicated with an inlet of the clear liquid tank. According to the recovery system, solid and liquid phases in the slag slurry can be efficiently separated, chlorosilane and dry powder in the slag slurry can be recovered, and the problem of silicon powder blockage of follow-up equipment can be avoided.

Description

Technical Field

[0001] The invention relates to a polysilicon slurry recovery system and method, 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 method. In the process of producing polysilicon by the modified Siemens method, a large amount of slurry is generated. The slurry mainly includes silicon powder, metal chloride, polychlorosilane, silicon tetrachloride, trichlorosilane and dichlorosilane. At present, there are two main ways to treat the polysilicon slurry. One is to carry out extensive hydrolysis treatment on the slurry, which causes a large amount of chlorosilane material waste and pollutes the environment. The other is to send part of the slurry to a vacuum drum filter, and use the adsorption layer formed by the mixture of diatomaceous earth and chlorosilane for solid-liquid separation. The separated solid phase is simply treated and sent to the hydrolysis system for treatment. The liquid phase is further purified and recycled. This method requires high control accuracy, which is very easy to cause the adsorption layer to fall off. The device has a short operating time and a high maintenance frequency. There are great safety hazards and the workload of personnel is increased. 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 slurry are not separated, resulting in serious waste of resources. Summary of the invention

[0004] The present invention provides a polysilicon slurry recovery system, which can efficiently separate the solid and liquid phases in the slurry, realize the recovery of chlorosilane and dry powder in the slurry, and the recovery system can also avoid the silicon powder clogging problem of subsequent equipment.

[0005] The present invention provides a method for recovering polysilicon slurry, which is carried out using the above-mentioned recovery system. The recovery method is simple to operate and is suitable for wide promotion and application.

[0006] The present invention provides a polysilicon slurry recovery system, which includes: a flash tank, a settling tank, a dryer, a dryer condenser, a washing tower and a clear liquid tank;

[0007] The slurry enters the flash tank through the inlet of the flash tank, the gas phase outlet of the flash tank is connected to the inlet of the clear liquid tank, the solid-liquid mixture outlet of the flash tank is connected to the inlet of the settling tank, and the solid-liquid mixture outlet of the settling tank is connected to the inlet of the dryer;

[0008] The outlet of the clear liquid tank is communicated with the liquid phase inlet of the washing tower, the gas phase outlet of the dryer is communicated with the gas phase inlet of the washing tower, the liquid phase outlet of the washing tower is communicated with the inlet of the clear liquid tank, the gas phase outlet of the washing tower is communicated with the inlet of the dryer condenser, and the outlet of the dryer condenser is communicated with the inlet of the clear liquid tank.

[0009] The recovery system as described above, wherein, further comprises: a clear liquid filter,

[0010] The supernatant outlet of the sedimentation tank is communicated with the inlet of the clear liquid filter, the filter residue outlet of the clear liquid filter is communicated with the inlet of the dryer, and the liquid phase outlet of the clear liquid filter is communicated with the inlet of the clear liquid tank.

[0011] The recovery system as described above, wherein, further comprises: a flash condenser;

[0012] The gas phase outlet of the flash tank is communicated with the inlet of the flash condenser, the liquid phase outlet of the flash condenser is communicated with the flash tank, and the gas phase outlet of the flash condenser is communicated with the inlet of the clear liquid tank.

[0013] The recovery system as described above, wherein, further comprises: a clear liquid distillation tower filter and a clear liquid distillation tower;

[0014] The outlet of the clear liquid tank is communicated with the inlet of the clear liquid distillation tower filter, the liquid phase outlet of the clear liquid distillation tower filter is communicated with the clear liquid distillation tower, and the silicon tetrachloride outlet of the clear liquid distillation tower is communicated with the sedimentation tank.

[0015] In the recovery system as described above, the temperature in the flash tank is 35 to 165° C. and the pressure is 0.05 to 1.5 MPaG.

[0016] The recovery system as described above, wherein in the settling tank, the temperature is 0-35°C, the time is 2-8 hours, and the pressure is 0.05-0.7 MPaG.

[0017] The recovery system as described above, wherein in the dryer, the temperature is 70-120°C, the time is 2-8 hours, and the pressure is 0.02-0.08 MPaG.

[0018] The recovery system as described above, wherein the filter of the clear liquid has a filtration accuracy of 1 to 3 μm, a temperature of 0 to 35° C., and a pressure of 0.1 to 0.7 MPaG; and / or

[0019] In the flash condenser, the temperature is 40-90°C and the pressure is 0.04-1.5 MPaG.

[0020] In the recovery system as described above, the temperature in the washing tower is 15-100° C. and the pressure is 0.02-0.08 MPaG.

[0021] The present invention provides a method for recovering polysilicon slurry, wherein the recovery method is carried out by the recovery system as described above.

[0022] The polysilicon slurry recovery system of the present invention can achieve efficient separation of solid and liquid phases in the slurry through the organic connection of a flash tank, a settling tank, a dryer, a dryer condenser, a washing tower and a clear liquid tank, thereby recovering chlorosilane and dry powder in the slurry, improving resource utilization efficiency, and the recovery system can also avoid the problem of silicon powder clogging in subsequent equipment.

[0023] The polysilicon slurry recovery method of the present invention is carried out using the above-mentioned recovery system. The recovery method can efficiently separate the solid and liquid phases in the slurry, realize the recovery of chlorosilane and dry powder in the slurry, improve the resource utilization efficiency, and the recovery method can also avoid the silicon powder clogging problem of subsequent equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] Figure 1 Schematic diagram of a polysilicon slurry recovery system in some embodiments of the present invention.

[0026] Description of reference numerals:

[0027] 1: Flash tank;

[0028] 2: Flash condenser;

[0029] 3: Sedimentation tank;

[0030] 4: Clear liquid filter;

[0031] 5: Dryer;

[0032] 6: Dryer condenser;

[0033] 7: Liquid tank;

[0034] 8: Scrubber;

[0035] 9: Clean liquid pump;

[0036] 10: Clear liquid distillation tower filter. DETAILED DESCRIPTION

[0037] 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.

[0038] Figure 1 Schematic diagram of a polysilicon slurry recovery system in some embodiments of the present invention. Figure 1 As shown, the first aspect of the present invention provides a polysilicon slurry recovery system, comprising: a flash tank 1, a settling tank 3, a dryer 5, a dryer condenser 6, a washing tower 8 and a clear liquid tank 7;

[0039] The slurry enters the flash tank 1 through the inlet of the flash tank 1, the gas phase outlet of the flash tank 1 is connected to the inlet of the clear liquid tank 7, the solid-liquid mixture outlet of the flash tank 1 is connected to the inlet of the settling tank 3, and the solid-liquid mixture outlet of the settling tank 3 is connected to the inlet of the dryer 5;

[0040] The outlet of the clear liquid tank 7 is connected to the liquid phase inlet of the washing tower 8, the gas phase outlet of the dryer 5 is connected to the gas phase inlet of the washing tower 8, the liquid phase outlet of the washing tower 8 is connected to the inlet of the clear liquid tank 7, the gas phase outlet of the washing tower 8 is connected to the inlet of the dryer condenser 6, and the outlet of the dryer condenser 6 is connected to the inlet of the clear liquid tank 7.

[0041] The present invention does not particularly limit the slurry, and the slurry can be the slurry produced in any section of the polysilicon preparation. For example, the slurry can come from at least one of a quench tower, a coarse fractionation tower, a distillation device, and a synthesis device. The slurry may include silicon powder, metal chloride, polychlorosilane, silicon tetrachloride, trichlorosilane, and dichlorosilane. In some embodiments, the slurry may include, by mass percentage: silicon powder 0.5-3 (wt%), metal chloride 0.1-5.0 (wt%), polychlorosilane 0.5-10 (wt%), silicon tetrachloride 70-95 (wt%), trichlorosilane 3-15 (wt%), and dichlorosilane 0-0.5 (wt%).

[0042] Specifically, the slurry enters the flash tank 1 through the inlet of the flash tank 1, and is flashed in the flash tank 1 to obtain a first solid-liquid mixture (mainly comprising silicon powder, metal chloride, polychlorosilane and chlorosilane) and a first gas phase (mainly comprising chlorosilane and polychlorosilane). The first gas phase is output through the gas phase outlet of the flash tank 1 and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7. The first solid-liquid mixture is output through the solid-liquid mixture outlet of the flash tank 1 and enters the settling tank 3 through the inlet of the settling tank 3. The settling treatment is performed in the settling tank 3 to obtain a second solid-liquid mixture (mainly comprising silicon powder, metal chloride, polychlorosilane and chlorosilane) and a supernatant (mainly comprising chlorosilane, polychlorosilane, trace silicon powder and metal chloride);

[0043] The second solid-liquid mixture is outputted from the solid-liquid mixture outlet of the settling tank 3, enters the dryer 5 through the inlet of the dryer 5, and is dried in the dryer 5 to obtain dry powder (mainly comprising silicon powder, metal chloride and trace polychlorosilane) and a second gas phase (mainly comprising chlorosilane, metal chloride and trace silicon powder). The second gas phase is outputted from the gas phase outlet of the dryer 5, enters the washing tower 8 through the gas phase inlet of the washing tower 8, and the chlorosilane solution is outputted from the outlet of the clear liquid tank 7, enters the washing tower 8 through the liquid phase inlet of the washing tower 8. In the washing tower 8, The second gas phase is washed with the chlorosilane solution to remove the silicon powder in the second gas phase. The chlorosilane solution containing silicon powder formed after the washing treatment is output through the liquid phase outlet of the washing tower 8, and enters the clear liquid tank 7 through the bottom of the clear liquid tank 7. The third gas phase obtained after the washing treatment is output through the gas phase outlet of the washing tower 8, and enters the dryer condenser 6 through the inlet of the dryer condenser 6. It is condensed in the dryer condenser 6 to form liquid chlorosilane. The liquid chlorosilane is output through the outlet of the dryer condenser 6 and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0044] In the present invention, the flash tank can be operated intermittently or continuously. The washing tower is operated continuously.

[0045] It can be understood that in the clear liquid tank 7 , the chlorosilane solution will settle, so that the top of the clear liquid tank 7 is enriched with the chlorosilane solution, and the bottom of the clear liquid tank 7 is enriched with silicon powder.

[0046] The polysilicon slurry recovery system of the present invention can achieve efficient separation of solid and liquid phases in the slurry through the organic connection of the flash tank 1, the settling tank 3, the dryer 5, the dryer condenser 6, the washing tower 8 and the clear liquid tank 7, thereby recovering chlorosilane and dry powder in the slurry, improving the utilization efficiency of resources, and the recovery system can also avoid the problem of silicon powder clogging in subsequent equipment.

[0047] In some embodiments of the present invention, the recovery system further comprises: a clear liquid filter 4,

[0048] The supernatant outlet of the sedimentation tank 3 is communicated with the inlet of the clear liquid filter 4 , the filter residue outlet of the clear liquid filter 4 is communicated with the inlet of the dryer 5 , and the liquid phase outlet of the clear liquid filter 4 is communicated with the inlet of the clear liquid tank 7 .

[0049] A small amount of solid phase still exists in the supernatant obtained by treatment in the sedimentation tank 3, so the supernatant can be output through the supernatant outlet of the sedimentation tank 3, enter the clear liquid filter 4 through the inlet of the clear liquid filter 4, and be filtered in the clear liquid filter 4 to separate the solid and liquid in the supernatant. The obtained filter residue is output through the filter residue outlet of the clear liquid filter 4, enters the dryer 5 through the inlet of the dryer 5, and the obtained liquid chlorosilane is output through the liquid phase outlet of the clear liquid filter 4, enters the clear liquid tank 7 through the inlet of the clear liquid tank 7 for storage.

[0050] In some embodiments, the serum filter is operated continuously.

[0051] The present invention provides a clear liquid filter 4 to filter the supernatant, so that the solid phase and the liquid phase in the supernatant can be better separated, and the obtained liquid chlorosilane can be reused. The obtained filter residue is dried to obtain dry powder, which can also be recycled to improve the utilization efficiency of resources.

[0052] In some embodiments of the present invention, the recovery system further comprises: a flash condenser 2;

[0053] The gas phase outlet of the flash tank 1 is communicated with the inlet of the flash condenser 2 , the liquid phase outlet of the flash condenser 2 is communicated with the flash tank 1 , and the gas phase outlet of the flash condenser 2 is communicated with the inlet of the clear liquid tank 7 .

[0054] Specifically, the first gas phase is output through the gas phase outlet of the flash tank 1, enters the flash condenser 2 through the inlet of the flash condenser 2, the first gas phase is condensed in the flash condenser 2, the non-condensable gas containing chlorosilane obtained after the condensation treatment is output through the gas phase outlet of the flash condenser 2, enters the clear liquid tank 7 through the inlet of the clear liquid tank 7, the liquid chlorosilane containing some impurities obtained after the condensation treatment is output through the liquid phase outlet of the flash condenser 2, enters the flash tank 1 through the inlet of the flash tank 1 to participate in the flash evaporation treatment.

[0055] Since some impurities still exist in the first gas phase obtained by the flash treatment in the flash tank 1, the flash condenser 2 can be used to condense the first gas phase to convert the first gas phase into non-condensable gas containing chlorosilane and liquid chlorosilane containing some impurities. The obtained gaseous chlorosilane can be collected and reused, and the obtained liquid chlorosilane can be returned to the flash tank 1 to participate in the flash treatment to further obtain gaseous chlorosilane with higher purity.

[0056] In some embodiments of the present invention, the recovery system further comprises: a clear liquid distillation tower filter 10 and a clear liquid distillation tower;

[0057] The liquid phase outlet of the clear liquid tank 7 is connected to the inlet of the clear liquid distillation tower filter 10, the liquid phase outlet of the clear liquid distillation tower filter 10 is connected to the clear liquid distillation tower, and the light component outlets of silicon tetrachloride, trichlorosilane, etc. of the clear liquid distillation tower are connected to the sedimentation tank 3.

[0058] Specifically, liquid chlorosilane is output through the liquid phase outlet of the clear liquid tank 7, enters the clear liquid distillation tower filter 10 through the inlet of the clear liquid distillation tower filter 10, and is filtered in the clear liquid distillation tower filter 10 to obtain pure liquid chlorosilane. The pure liquid chlorosilane is output through the liquid phase outlet of the clear liquid distillation tower filter 10 and enters the clear liquid distillation tower to be distilled in the clear liquid distillation tower to obtain silicon tetrachloride, trichlorosilane, and other light components. Silicon tetrachloride, trichlorosilane, and other light components are output through the outlet of the clear liquid distillation tower and enter the settling tank 3.

[0059] The present invention utilizes a distillation tower feed filter and a clear liquid distillation tower to process the liquid phase chlorosilane output from the clear liquid tank 7, respectively, so as to separate silicon tetrachloride, trichlorosilane, and other light components in the liquid phase chlorosilane, and further improve the utilization efficiency of resources. Further, silicon tetrachloride, trichlorosilane, and other light components are allowed to enter the sedimentation tank 3 to participate in the sedimentation treatment, so as to increase the liquid phase content in the first solid-liquid mixture, and the first solid-liquid mixture can be rinsed and diluted, so as to promote the separation of the second solid-liquid mixture and the supernatant in the sedimentation treatment, and improve the efficiency of the sedimentation treatment.

[0060] In some embodiments, a clear liquid pump 9 is further included, the liquid phase outlet of the clear liquid tank 7 is connected to the inlet of the clear liquid pump 9, and the outlet of the clear liquid pump 9 is connected to the inlet of the clear liquid distillation tower filter 10. The clear liquid pump 9 is used to provide pressure for the liquid chlorosilane so that the liquid chlorosilane can enter the clear liquid distillation tower filter 10.

[0061] Furthermore, the present invention can also select parameters in each structural unit to further improve the recovery efficiency and save production costs. For example, in some embodiments of the present invention, the temperature in the flash tank 1 is 35-165° C. and the pressure is 0.05-1.5 MPaG.

[0062] In sedimentation tank 3, the temperature is 0-35°C, the time is 2-8h, and the pressure is 0.05-0.7MPaG.

[0063] In the dryer 5, the temperature is 70-120°C, the time is 2-8 hours, and the pressure is 0.02-0.08 MPaG.

[0064] In the clear liquid filter 4, the filtration accuracy is 1 to 3 μm, the temperature is 0 to 35°C, and the pressure is 0.1 to 0.7 MPaG;

[0065] In the flash condenser 2, the temperature is 40 to 90°C (the temperature is reduced from 90°C to 40°C), and the pressure is 0.04 to 1.5 MPaG.

[0066] In the washing tower 8, the temperature is 15 to 100°C and the pressure is 0.02 to 0.08 MPaG.

[0067] A second aspect of the present invention provides a method for recovering polysilicon slurry, which is performed by the recovery system of the first aspect.

[0068] The polysilicon slurry recovery method of the present invention is carried out using the above-mentioned recovery system. The recovery method can efficiently separate the solid and liquid phases in the slurry, realize the recovery of chlorosilane and dry powder in the slurry, improve the resource utilization efficiency, and the recovery method can also avoid the silicon powder clogging problem of subsequent equipment.

[0069] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0070] Example 1

[0071] The polysilicon slurry recovery system of this embodiment is as follows: Figure 1 As shown, it includes: a flash tank 1, a settling tank 3, a dryer 5, a clear liquid tank 7, a clear liquid filter 4, a flash condenser 2, a dryer condenser 6, a washing tower 8, a clear liquid pump 9, a clear liquid distillation tower filter 10 and a clear liquid distillation tower;

[0072] The slurry enters the flash tank 1 through the inlet of the flash tank 1, the gas phase outlet of the flash tank 1 is connected to the inlet of the flash condenser 2, the gas phase outlet of the flash condenser 2 is connected to the inlet of the clear liquid tank 7, the solid-liquid mixture outlet of the flash tank 1 is connected to the inlet of the settling tank 3, and the solid-liquid mixture outlet of the settling tank 3 is connected to the inlet of the dryer 5; the supernatant outlet of the settling tank 3 is connected to the inlet of the clear liquid filter 4, the filter residue outlet of the clear liquid filter 4 is connected to the inlet of the dryer 5, and the liquid phase outlet of the clear liquid filter 4 is connected to the inlet of the clear liquid tank 7;

[0073] The outlet of the clear liquid tank 7 is communicated with the liquid phase inlet of the washing tower 8, the gas phase outlet of the dryer 5 is communicated with the gas phase inlet of the washing tower 8, the liquid phase outlet of the washing tower 8 is communicated with the inlet of the clear liquid tank 7, the gas phase outlet of the washing tower 8 is communicated with the inlet of the dryer condenser 6, and the outlet of the dryer condenser 6 is communicated with the inlet of the clear liquid tank 7;

[0074] The outlet of the clear liquid tank 7 is communicated with the inlet of the clear liquid pump 9, the outlet of the clear liquid pump 9 is communicated with the inlet of the clear liquid distillation tower filter 10, the liquid phase outlet of the clear liquid distillation tower filter 10 is communicated with the clear liquid distillation tower, and the silicon tetrachloride outlet of the clear liquid distillation tower is communicated with the settling tank 3;

[0075] Among them, flash tank 1 is in continuous operation, and the temperature in flash tank 1 is 85°C and the pressure is 0.08MPaG;

[0076] In sedimentation tank 3, the temperature is 25°C, the time is 6h, and the pressure is 0.05MPaG;

[0077] In dryer 5, the temperature is 120°C, the time is 6h, and the pressure is 0.05MPaG;

[0078] The clear liquid filter 4 is for continuous filtration, and the filtration accuracy in the clear liquid filter 4 is 1 μm and the temperature is 25°C;

[0079] In flash condenser 2, the temperature is 50-85°C and the pressure is 0.08MPaG;

[0080] The washing tower 8 is for continuous washing. In the washing tower 8, the temperature is 40°C and the pressure is 0.05 MPaG.

[0081] Example 2

[0082] The method for recovering polysilicon slurry in this embodiment is carried out using the recovery system in Embodiment 1, and specifically includes:

[0083] The slurry enters the flash tank 1 through the inlet of the flash tank 1, and is flash-treated in the flash tank 1 to obtain a first solid-liquid mixture (mainly comprising chlorosilanes, metal chlorides, polychlorosilanes and silicon powder) and a first gas phase (mainly comprising chlorosilanes and polychlorosilanes). The first gas phase is output through the gas phase outlet of the flash tank 1, and enters the flash condenser 2 through the inlet of the flash condenser 2. The first gas phase is condensed in the flash condenser 2. The non-condensable gas containing chlorosilane obtained after the condensation treatment is output through the gas phase outlet of the flash condenser 2 and is output through the inlet of the clear liquid tank 7. Entering the clear liquid tank 7, the liquid chlorosilane containing some impurities and polychlorosilane obtained after condensation treatment is output through the liquid phase outlet of the flash condenser 2, and enters the flash tank 1 through the inlet of the flash tank 1 to participate in the flash treatment; the first solid-liquid mixture is output through the solid-liquid mixture outlet of the flash tank 1, and enters the settling tank 3 through the inlet of the settling tank 3, and is subjected to sedimentation treatment in the settling tank 3 to obtain the second solid-liquid mixture (mainly containing silicon powder, metal chloride, chlorosilane, and a small amount of polychlorosilane) and the supernatant (mainly containing chlorosilane, polychlorosilane and trace silicon powder);

[0084] The supernatant is outputted through the supernatant outlet of the sedimentation tank 3, enters the clear liquid filter 4 through the inlet of the clear liquid filter 4, and is filtered in the clear liquid filter 4; the obtained filter residue is outputted through the filter residue outlet of the clear liquid filter 4, enters the dryer 5 through the inlet of the dryer 5; the obtained liquid chlorosilane is outputted through the liquid phase outlet of the clear liquid filter 4, enters the clear liquid tank 7 through the inlet of the clear liquid tank 7, and is stored;

[0085] The second solid-liquid mixture is outputted from the solid-liquid mixture outlet of the settling tank 3, enters the dryer 5 through the inlet of the dryer 5, and is dried in the dryer 5 to obtain dry powder (mainly including silicon powder, metal chloride and trace polychlorosilane) and a second gas phase (mainly containing chlorosilane, metal chloride and trace silicon powder). The second gas phase is outputted from the gas phase outlet of the dryer 5, enters the washing tower 8 through the gas phase inlet of the washing tower 8, and the chlorosilane solution is outputted from the outlet of the clear liquid tank 7, enters the washing tower 8 through the liquid phase inlet of the washing tower 8. In the washing tower 8, the chlorosilane solution is outputted from the outlet of the clear liquid tank 7, enters the washing tower 8 through the liquid phase inlet of the washing tower 8, and the chlorosilane solution is outputted from the outlet of the clear liquid tank 7, enters the washing tower 8 through the liquid phase inlet of the washing tower 8. The second gas phase is washed with the silane solution to remove silicon powder in the second gas phase. The chlorosilane solution containing silicon powder formed after the washing treatment is output through the liquid phase outlet of the washing tower 8, and enters the clear liquid tank 7 through the bottom of the clear liquid tank 7. The third gas phase chlorosilane obtained after the washing treatment is output through the gas phase outlet of the washing tower 8, and enters the dryer condenser 6 through the inlet of the dryer condenser 6. The third gas phase chlorosilane is condensed in the dryer condenser 6 to form liquid phase chlorosilane. The liquid phase chlorosilane is output through the outlet of the dryer condenser 6, and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0086] Liquid chlorosilane is outputted through the liquid phase outlet of the clear liquid tank 7, and enters the clear liquid pump 9 through the inlet of the clear liquid pump 9. The clear liquid pump 9 pumps the liquid chlorosilane into the clear liquid distillation tower filter 10. The liquid chlorosilane is filtered in the clear liquid distillation tower filter 10 to obtain pure liquid chlorosilane. The pure liquid chlorosilane is outputted through the liquid phase outlet of the clear liquid distillation tower filter 10 and enters the clear liquid distillation tower for distillation treatment in the clear liquid distillation tower to obtain light components such as silicon tetrachloride and trichlorosilane. The light components such as silicon tetrachloride and trichlorosilane are outputted through the outlet of the clear liquid distillation tower and enter the settling tank 3.

[0087] The slurry may include, by mass percentage, 2.75% silicon powder, 0.13% metal chloride, 0.9% polychlorosilane, 91.14% silicon tetrachloride, 4.88% trichlorosilane, and 0.2% dichlorosilane.

[0088] Comparative Example

[0089] The method for recovering polysilicon slurry in this comparative example is basically the same as that in Example 2, except that:

[0090] Excluding the washing tower, the second gas phase is output through the outlet of the dryer 5, enters the dryer condenser 6 through the inlet of the dryer condenser 6, is condensed in the dryer condenser 6 to form liquid chlorosilane, and the liquid chlorosilane is output through the outlet of the dryer condenser 6, and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0091] Compared with Example 2, the second gas phase that has not been washed by the washing tower gradually precipitates metal chlorides in the pipeline due to temperature changes, blocking the pipeline and further blocking the dryer condenser 6, causing the dryer to operate poorly and requiring frequent replacement of the dryer condenser 6. The service life of the dryer condenser 6 is greatly shortened, and the dryer condenser 6 needs to be replaced and the dryer gas phase pipeline needs to be disassembled in less than a month, which affects the normal operation of the slurry treatment in actual production.

[0092] 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 polysilicon slurry recovery system, characterized in that: include: Flash tanks, settling tanks, dryers, dryer condensers, scrubbers, and clear liquid tanks; The slurry enters the flash tank through the inlet of the flash tank, the gas phase outlet of the flash tank is connected to the inlet of the clear liquid tank, the solid-liquid mixture outlet of the flash tank is connected to the inlet of the settling tank, and the solid-liquid mixture outlet of the settling tank is connected to the inlet of the dryer; The outlet of the clear liquid tank is communicated with the liquid phase inlet of the washing tower, the gas phase outlet of the dryer is communicated with the gas phase inlet of the washing tower, the liquid phase outlet of the washing tower is communicated with the inlet of the clear liquid tank, the gas phase outlet of the washing tower is communicated with the inlet of the dryer condenser, and the outlet of the dryer condenser is communicated with the inlet of the clear liquid tank.

2. The recovery system according to claim 1, characterized in that: Also includes: Clear liquid filter, The supernatant outlet of the sedimentation tank is communicated with the inlet of the clear liquid filter, the filter residue outlet of the clear liquid filter is communicated with the inlet of the dryer, and the liquid phase outlet of the clear liquid filter is communicated with the inlet of the clear liquid tank.

3. The recovery system according to claim 2, characterized in that: Also includes: Flash condenser; The gas phase outlet of the flash tank is communicated with the inlet of the flash condenser, the liquid phase outlet of the flash condenser is communicated with the flash tank, and the gas phase outlet of the flash condenser is communicated with the inlet of the clear liquid tank.

4. The recovery system according to any one of claims 1 to 3, characterized in that: Also includes: Clear liquid distillation tower filter and clear liquid distillation tower; The outlet of the clear liquid tank is communicated with the inlet of the clear liquid distillation tower filter, the liquid phase outlet of the clear liquid distillation tower filter is communicated with the clear liquid distillation tower, and the silicon tetrachloride outlet of the clear liquid distillation tower is communicated with the sedimentation tank.

5. The recycling system according to any one of claims 1 to 4, characterized in that: In the flash tank, the temperature is 35-165° C. and the pressure is 0.05-1.5 MPaG.

6. The recycling system according to any one of claims 1 to 5, characterized in that: In the sedimentation tank, the temperature is 0-35°C, the time is 2-8h, and the pressure is 0.05-0.7MPaG.

7. The recycling system according to any one of claims 1 to 6, characterized in that: In the dryer, the temperature is 70-120°C, the time is 2-8 hours, and the pressure is 0.02-0.08 MPaG.

8. The recovery system according to claim 3, characterized in that: In the clear liquid filter, the filtration accuracy is 1-3 μm, the temperature is 0-35° C., and the pressure is 0.1-0.7 MPaG; and / or, In the flash condenser, the temperature is 40-90°C and the pressure is 0.04-1.5 MPaG.

9. The recycling system according to any one of claims 1 to 8, characterized in that: In the washing tower, the temperature is 15-100° C. and the pressure is 0.02-0.08 MPaG.

10. A method for recovering polysilicon slurry, characterized in that: The recovery method is carried out by the recovery system according to any one of claims 1 to 9.

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