A method and system for recovering polysilicon slurry

Abstract

The application provides a polysilicon slurry recovery method and system. The polysilicon slurry recovery method comprises the following steps: performing flash treatment on the slurry to obtain a first solid-liquid mixture and a first gaseous chlorosilane; performing sedimentation treatment on the first solid-liquid mixture to obtain a second solid-liquid mixture and supernatant; performing first drying treatment on the second solid-liquid mixture to obtain a first dry powder and a second gaseous chlorosilane; and collecting the first gaseous chlorosilane and the second gaseous chlorosilane. The recovery method can efficiently separate the solid and liquid phases in the slurry, and realizes recovery of chlorosilane and dry powder in the slurry, thereby improving resource utilization efficiency.

Description

Technical Field

[0001] This invention relates to a method and system for recovering polycrystalline silicon slag slurry, belonging to the field of chemical separation technology. Background Technology

[0002] With increasing demand, the photovoltaic and integrated circuit industries have experienced rapid development. Polysilicon is a core raw material for both industries, leading to a surge in polysilicon production by various companies.

[0003] Currently, almost all polysilicon manufacturers use the modified Siemens process, which generates a large amount of slurry during polysilicon production. This slurry mainly consists of silicon powder, metal chlorides, polychlorosilanes, silicon tetrachloride, trichlorosilane, and dichlorosilanes. Currently, there are two main methods for treating polysilicon slurry. One method involves coarse hydrolysis, which results in significant waste of chlorosilanes and environmental pollution. The other method involves sending a portion of the slurry to a vacuum drum filter, where a solid-liquid separation is achieved using an adsorption layer composed of diatomaceous earth and chlorosilanes. The separated solid phase is then simply processed before being sent to a hydrolysis system, while the liquid phase is further purified and recycled. This method requires high precision control, is prone to adsorption layer detachment, has short operating times, requires frequent maintenance, poses significant safety hazards, and increases workload. Furthermore, this method has poor filtration and adsorption effects, low recovery rates, and fails to separate high-value components from the slurry, resulting in severe resource waste. Summary of the Invention

[0004] This invention provides a method for recycling polycrystalline silicon slag slurry. This method can efficiently separate the solid and liquid phases in the slag slurry and recover chlorosilanes and dry powders from the slag slurry, thereby improving resource utilization efficiency.

[0005] This invention provides a polycrystalline silicon slag slurry recovery system for implementing the above-mentioned recovery method. The recovery system has a simple structure and can efficiently separate the solid and liquid phases in the slurry, thereby recovering chlorosilanes and dry powders from the slurry and improving resource utilization efficiency.

[0006] This invention provides a method for recycling polycrystalline silicon slag slurry, comprising the following steps:

[0007] The slurry is subjected to flash evaporation to obtain a first solid-liquid mixture and a first gas phase;

[0008] The first solid-liquid mixture is subjected to sedimentation treatment to obtain a second solid-liquid mixture and a supernatant.

[0009] The second solid-liquid mixture is subjected to a first drying treatment to obtain a first dry powder and a second gas phase;

[0010] Collect the first gas phase and the second gas phase.

[0011] The recycling method described above further includes:

[0012] The supernatant is subjected to a first filtration process to obtain a first liquid phase and filter residue;

[0013] The filter residue is subjected to a second drying treatment to obtain the second dry powder and the third gas phase;

[0014] Collect the first liquid phase and the third gas phase.

[0015] The recycling method described above further includes:

[0016] The first gas phase is subjected to a first condensation treatment to obtain the fourth gas phase and the second liquid phase. The fourth gas phase is collected, and the second liquid phase alkane is subjected to flash evaporation treatment; and / or,

[0017] The second gas phase is subjected to a second condensation treatment to obtain the third liquid phase, and the third liquid phase is collected; and / or,

[0018] The third gas phase is subjected to a third condensation treatment to obtain the fourth liquid phase, and the fourth liquid phase is collected.

[0019] The recycling method described above further includes:

[0020] The first liquid phase, the fourth gas phase, the third liquid phase, and the fourth liquid phase are all introduced into a clear liquid tank to obtain a fifth liquid phase and a fifth gas phase;

[0021] The fifth gas phase is subjected to a fourth condensation treatment to obtain a sixth gas phase and a sixth liquid phase;

[0022] The sixth gas phase is washed to return the sixth liquid phase to the clear liquid tank.

[0023] The recycling method described above further includes:

[0024] The fifth liquid phase is subjected to a second filtration process to obtain a seventh liquid phase, which is then distilled to obtain silicon tetrachloride.

[0025] The recycling method described above, wherein the silicon tetrachloride is involved in the sedimentation process.

[0026] In the recovery method described above, the flash evaporation treatment is performed at a temperature of 35–165°C and a pressure of 0.05–1.5 MPaG; and / or,

[0027] In the sedimentation treatment, the temperature is 0–35℃, the time is 2–8 hours, and the pressure is 0.05–0.7 MPaG; and / or,

[0028] In the first drying process, the temperature is 70–120°C, the time is 2–8 hours, and the pressure is 0.02–0.08 MPaG; and / or,

[0029] In the second drying process, the temperature is 70–120°C, the time is 2–8 hours, and the pressure is 0.02–0.08 MPaG; and / or,

[0030] In the first filtration process, the filtration accuracy is 1–3 μm, the temperature is 0–35 °C, and the pressure is 0.1–0.7 MPaG; and / or,

[0031] In the first condensation process, the temperature is 80–40°C, and the pressure is 0.04–1.5 MPaG; and / or,

[0032] In the second condensation process, the temperature is 120–40°C, and the pressure is 0.02–0.08 MPaG; and / or,

[0033] In the third condensation process, the temperature is 120–40°C, and the pressure is 0.02–0.08 MPaG; and / or,

[0034] In the fourth condensation process, the temperature is -15 to 40°C, and the pressure is 0.02 to 0.08 MPaG; and / or,

[0035] In the second filtration process, the filtration accuracy is 1–3 μm, the temperature is 0–50 °C, and the pressure is 0.1–1.5 MPaG; and / or,

[0036] In the distillation process, the temperature is 80–150°C and the pressure is 0.08–0.2 MPaG.

[0037] The present invention provides a recycling system for implementing the recycling method described above, comprising: a flash tank, a settling tank, a dryer, and a clarified liquid tank;

[0038] The slurry enters the flash tank through the inlet of the flash 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;

[0039] The gas phase outlet of the flash evaporator is connected to the inlet of the clear liquid tank, and the gas phase outlet of the dryer is connected to the inlet of the clear liquid tank.

[0040] The recycling system described above further includes: a clarified liquid filter.

[0041] The supernatant outlet of the settling tank is connected to the inlet of the clear liquid filter, the filter residue outlet of the clear liquid filter is connected to the inlet of the dryer, and the liquid phase outlet of the clear liquid filter is connected to the inlet of the clear liquid tank.

[0042] The recovery system described above further includes: a flash condenser;

[0043] The vapor phase outlet of the flash evaporator is connected to the inlet of the flash condenser, the liquid phase outlet of the flash condenser is connected to the flash evaporator, and the vapor phase outlet of the flash condenser is connected to the inlet of the clear liquid tank; and / or,

[0044] Also includes: dryer condenser;

[0045] The gas phase outlet of the dryer is connected to the inlet of the dryer condenser, and the outlet of the dryer condenser is connected to the inlet of the clear liquid tank; and / or,

[0046] It also includes: cryogenic equipment and exhaust gas scrubbing tower;

[0047] The gas phase outlet of the clarified liquid tank is connected to the inlet of the cryogenic unit, the gas phase outlet of the cryogenic unit is connected to the tail gas scrubbing tower, and the liquid phase outlet of the cryogenic unit is connected to the clarified liquid tank; and / or,

[0048] It also includes: a clear liquid distillation column filter and a clear liquid distillation column;

[0049] The liquid phase outlet of the clear liquid tank is connected to the inlet of the clear liquid distillation tower filter, the liquid phase outlet of the clear liquid distillation tower filter is connected to the clear liquid distillation tower, and the silicon tetrachloride outlet of the clear liquid distillation tower is connected to the settling tank.

[0050] The present invention discloses a method for recovering polycrystalline silicon slurry, comprising sequentially performing flash evaporation, sedimentation, and drying treatments on the slurry, and recovering the products from each treatment step. This recovery method can efficiently separate the solid and liquid phases in the slurry and recover chlorosilanes and dry powders from the slurry, thereby improving resource utilization efficiency.

[0051] The polycrystalline silicon slag slurry recovery system of the present invention is used to implement the above-mentioned recovery method. The recovery system has a simple structure and can efficiently separate the solid and liquid phases in the slurry, realize the recovery of chlorosilanes and dry powders in the slurry, and improve the resource utilization efficiency. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the polycrystalline silicon slag slurry recycling process in some embodiments of the present invention.

[0054] Explanation of reference numerals in the attached figures:

[0055] 1: Flash evaporator;

[0056] 2: Flash condenser;

[0057] 3: Settling tank;

[0058] 4: Clear liquid filter;

[0059] 5: Dryer;

[0060] 6: Dryer condenser;

[0061] 7: Clear liquid tank;

[0062] 8: Cryocooler;

[0063] 9: Clear liquid pump;

[0064] 10: Clear liquid distillation tower filter. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Figure 1 This is a schematic diagram illustrating the polycrystalline silicon slag slurry recycling process in some embodiments of the present invention. For example... Figure 1 As shown, a first aspect of the present invention provides a method for recycling polycrystalline silicon slag slurry, comprising the following steps:

[0067] The slurry is subjected to flash evaporation to obtain a first solid-liquid mixture and a first gas phase;

[0068] The first solid-liquid mixture was subjected to sedimentation treatment to obtain a second solid-liquid mixture and a supernatant;

[0069] The second solid-liquid mixture is subjected to a first drying treatment to obtain a first dry powder and a second gas phase;

[0070] Collect the first gas phase and the second gas phase.

[0071] This invention does not specifically limit the slurry; the slurry can be generated from any stage of the polycrystalline silicon preparation process. For example, the slurry can originate from at least one of the following: a quench tower, a roughing tower, a distillation unit, and a synthesis unit. The slurry may include silicon powder, metal chlorides, polychlorosilanes, silicon tetrachloride, trichlorosilane, and dichlorosilane. In some embodiments, the slurry may include, by mass percentage: 0.5–3 wt% silicon powder, 0.1–5.0 wt% metal chlorides, 0.5–10 wt% polychlorosilanes, 70–95 wt% silicon tetrachloride, 3–15 wt% trichlorosilane, and 0–0.5 wt% dichlorosilane.

[0072] Specifically, the recycling method of the present invention includes: flash evaporation of the slurry to obtain a first gas phase (mainly comprising chlorosilanes and a small amount of polychlorosilanes) and a first solid-liquid mixture mainly comprising silicon powder, metal chlorides, polychlorosilanes, and chlorosilanes; then sedimentation of the first solid-liquid mixture to separate the solid and liquid phases, thereby obtaining a second solid-liquid mixture (mainly comprising chlorosilanes, silicon powder, metal chlorides, and a small amount of polychlorosilanes) and a supernatant (mainly comprising chlorosilanes, polychlorosilanes, and trace amounts of silicon powder); next, a first drying treatment of the second solid-liquid mixture to evaporate the liquid phase, obtaining a second gas phase (mainly comprising chlorosilanes and a small amount of metal chlorides and polychlorosilanes) and a first dry powder (mainly comprising silicon powder, metal chlorides, and a small amount of polychlorosilanes), wherein the first dry powder can be recycled, and the first and second gas phases can be collected and reused.

[0073] In this invention, the flash evaporation process can be either continuous flash evaporation or intermittent flash evaporation.

[0074] The present invention discloses a method for recovering polycrystalline silicon slurry, comprising sequentially performing flash evaporation, sedimentation, and drying treatments on the slurry, and recovering the products from each treatment step. This recovery method can efficiently separate the solid and liquid phases in the slurry and recover chlorosilanes and dry powders from the slurry, thereby improving resource utilization efficiency.

[0075] In some embodiments of the present invention, the recycling method further includes:

[0076] The supernatant is subjected to a first filtration process to obtain a first liquid phase (mainly including chlorosilane and polychlorosilane) and filter residue;

[0077] The filter residue is subjected to a second drying process to obtain a second dry powder and a third gas phase;

[0078] Collect the first liquid phase and the third gas phase.

[0079] Since a small amount of solid phase remains in the supernatant obtained after sedimentation, the supernatant can be subjected to a first filtration process to remove the small amount of solid phase, thereby obtaining a first liquid phase (mainly containing chlorosilanes, polychlorosilanes, and metal chlorides) and filter residue. Then, the filter residue can be subjected to a second drying process to evaporate the liquid phase in the filter residue, obtaining a second dry powder and a third gas phase. The obtained second dry powder can be recycled, and the obtained first liquid phase and third gas phase can be collected and reused.

[0080] In this invention, the first filtration process is continuous filtration.

[0081] In this invention, the first drying process and the second drying process may be the same or different. In some embodiments, the filter residue may be mixed with the second solid-liquid mixture and then dried to obtain dry powder and gas phase. The dry powder may be recycled, and the gas phase and the first clear liquid may be collected and reused.

[0082] This invention obtains higher purity liquid chlorosilanes by performing a first filtration and a second drying process on the supernatant obtained after sedimentation, thus fully recovering the chlorosilanes in the slurry.

[0083] In some embodiments of the present invention, the recycling method further includes:

[0084] The first gas phase is subjected to a first condensation treatment to obtain a fourth gas phase and a second liquid phase (mainly containing chlorosilane and polychlorosilane). The fourth gas phase is collected, and the second liquid phase participates in the flash evaporation treatment.

[0085] Since the first gas phase obtained by flash evaporation still contains some impurities, the first gas phase can be subjected to a first condensation treatment to convert it into a fourth gas phase with higher purity and a second liquid phase containing some impurities. The obtained fourth gas phase can be collected and reused, and the obtained second liquid phase can be returned to participate in flash evaporation treatment to further obtain gas phase chlorosilane with higher purity.

[0086] The present invention can further improve the purity of gaseous chlorosilanes through a first condensation process, thereby improving the efficiency of resource recycling.

[0087] In some embodiments of the present invention, the recovery method further includes: subjecting the second gas phase (mainly containing chlorosilanes, small amounts of metal chlorides and polychlorosilanes) to a second condensation treatment to obtain a third liquid phase, and collecting the third liquid phase; and / or,

[0088] The third gas phase is subjected to a third condensation process to obtain a fourth liquid phase, which is then collected.

[0089] Specifically, the second gas phase is subjected to a second condensation treatment to condense the second gas phase into a third liquid phase, and the third liquid phase is collected; and / or, the third gas phase is subjected to a third condensation treatment to condense the third gas phase into a fourth liquid phase, and the fourth liquid phase is collected.

[0090] In this invention, the second condensation process can be the same as or different from the first. In some embodiments, the second gas phase and the third gas phase can be mixed and then condensed to obtain liquid chlorosilane, which is then collected.

[0091] This invention facilitates the collection of chlorosilanes by condensing the second and third gas phases into liquid chlorosilanes respectively.

[0092] In some embodiments of the present invention, the recycling method further includes:

[0093] The first liquid phase, the fourth gas phase, the third liquid phase, and the fourth liquid phase are all introduced into the clear liquid tank 7 to obtain five liquid phases (mainly including chlorosilane, polychlorosilane, and a small amount of metal chloride and trace amount of silicon powder) and the fifth gas phase;

[0094] The fifth gas phase is subjected to a fourth condensation process to obtain a sixth gas phase and a sixth liquid phase.

[0095] The sixth gas phase is washed to return the sixth liquid phase to the clear liquid tank 7.

[0096] Specifically, the first liquid phase, the fourth gas phase, the third liquid phase, and the fourth liquid phase all enter the clear liquid tank 7. Since the temperatures of the first liquid phase, the fourth gas phase, the third liquid phase, and the fourth liquid phase are different, a fifth liquid phase and a fifth gas phase will be formed in the clear liquid tank 7. Under normal circumstances, the fifth gas phase still contains some impurities. The fifth gas phase can be subjected to a fourth condensation treatment to condense the high-purity chlorosilane in the fifth gas phase into a sixth liquid phase. The sixth liquid phase is returned to the clear liquid tank 7, while the uncondensed phase forms the sixth gas phase. The sixth gas phase can be washed to further remove impurities from the sixth gas phase.

[0097] This invention improves the recovery rate of chlorosilanes by condensing the fifth gas phase in the clear liquid tank 7 to further recover high-purity chlorosilanes from the fifth gas phase chlorosilanes.

[0098] In some embodiments of the present invention, the recycling method further includes:

[0099] The fifth liquid phase is subjected to a second filtration process to obtain a seventh liquid phase (mainly consisting of chlorosilanes and polychlorosilanes). The seventh liquid phase is then distilled to obtain light components such as silicon tetrachloride, trichlorosilane, and dichlorosilane.

[0100] Specifically, the fifth liquid phase undergoes a second filtration process to further remove solid impurities, yielding a seventh liquid phase with higher purity. The seventh liquid phase is then distilled to separate light components such as silicon tetrachloride, trichlorosilane, and dichlorosilane. The obtained light chlorosilane components can be further utilized.

[0101] In this invention, the second filtration process is continuous filtration. The distillation process is continuous distillation.

[0102] This invention utilizes a second filtration and distillation process in the fifth liquid phase of the clarifying tank 7 to separate light components such as silicon tetrachloride, trichlorosilane, and dichlorosilane, thereby further improving resource utilization efficiency and saving production costs.

[0103] Furthermore, light components such as silicon tetrachloride, trichlorosilane, and dichlorosilane can be incorporated into the sedimentation process. This invention, by adding light components such as silicon tetrachloride, trichlorosilane, and dichlorosilane to the sedimentation process, can increase the liquid phase content in the first solid-liquid mixture and can also rinse and dilute the first solid-liquid mixture, promoting the separation of the second solid-liquid mixture from the supernatant during sedimentation and improving the efficiency of the sedimentation process. Moreover, the light components such as silicon tetrachloride, trichlorosilane, and dichlorosilane added to the sedimentation process originate from the slurry, further improving resource utilization efficiency.

[0104] Furthermore, the present invention can also select parameters in each step to further improve recovery efficiency and save production costs. For example, in the flash evaporation process, the temperature is 35–165°C, and the pressure is 0.05–1.5 MPaG; and / or,

[0105] During the settling treatment, the temperature was 0–35℃, the time was 2–8 h, and the pressure was 0.05–0.7 MPaG; and / or,

[0106] In the first drying process, the temperature is 70–120℃, the time is 2–8 hours, and the pressure is 0.02–0.08 MPaG; and / or,

[0107] In the second drying process, the temperature is 70–120℃, the time is 2–8 hours, and the pressure is 0.02–0.08 PaG; and / or,

[0108] In the first filtration process, the filtration accuracy is 1–3 μm, the temperature is 0–35 °C, and the pressure is 0.1–0.7 MPaG; and / or,

[0109] In the first condensation process, the temperature is 40–80°C (reducing the temperature from 80°C to 40°C), and the pressure is 0.04–1.5 MPaG; and / or,

[0110] In the second condensation process, the temperature is 40–120°C (reducing the temperature from 120°C to 40°C), and the pressure is 0.02–0.08 MPaG; and / or,

[0111] In the third condensation process, the temperature is 40–120°C (reducing the temperature from 120°C to 40°C), and the pressure is 0.02–0.08 MPaG; and / or,

[0112] In the fourth condensation process, the temperature is -15 to 40°C (reducing the temperature from 40°C to -15°C), and the pressure is 0.02 to 0.08 MPaG; and / or,

[0113] In the second filtration process, the filtration accuracy is 1–3 μm, the temperature is 0–50 °C, and the pressure is 0.1–1.5 MPaG; and / or,

[0114] During distillation, the temperature is 80–150℃ and the pressure is 0.08–0.2 MPaG.

[0115] like Figure 1 As shown, a second aspect of the present invention provides a recycling system for implementing the recycling method of the first aspect, comprising: a flash tank 1, a settling tank 3, a dryer 5, and a clear liquid tank 7;

[0116] The slurry enters the flash tank 1 through the inlet of the flash tank 1. The solid-liquid mixture outlet of the flash tank 1 is connected to the inlet of the settling tank 3. The solid-liquid mixture outlet of the settling tank 3 is connected to the inlet of the dryer 5.

[0117] The gas phase outlet of flash tank 1 is connected to the inlet of clear liquid tank 7, and the gas phase outlet of dryer 5 is connected to the inlet of clear liquid tank 7.

[0118] Specifically, the slurry enters the flash tank 1 through the inlet of the flash tank 1 and undergoes flash treatment in the flash tank 1 to obtain a first solid-liquid mixture and a first gas phase;

[0119] The first solid-liquid mixture is output from the solid-liquid mixture outlet of flash tank 1 and enters settling tank 3 through the inlet of settling tank 3. Settling is carried out in settling tank 3 to obtain the second solid-liquid mixture and supernatant.

[0120] The second solid-liquid mixture is output from the solid-liquid mixture outlet of the settling tank 3 and enters the dryer 5 through the inlet of the dryer 5, where it is dried to obtain the first dry powder and the second gas phase.

[0121] The first gas phase is output from the gas phase outlet of flash tank 1 and enters clear liquid tank 7 through the inlet of clear liquid tank 7. The second gas phase is output from the gas phase outlet of dryer 5 and enters clear liquid tank 7 through the inlet of clear liquid tank 7.

[0122] The recycling system of the present invention is used to implement the recycling method of the first aspect. The recycling system has a simple structure, is easy to operate, and can efficiently separate the solid and liquid phases in the slurry, thereby realizing the recovery of chlorosilanes and dry powders in the slurry and improving the utilization efficiency of resources.

[0123] Furthermore, the recovery system also includes: a clear liquid filter 4,

[0124] The supernatant outlet of settling tank 3 is connected to the inlet of clear liquid filter 4, the filter residue outlet of clear liquid filter 4 is connected to the inlet of dryer 5, and the liquid phase outlet of clear liquid filter 4 is connected to the inlet of clear liquid tank 7.

[0125] Specifically, the supernatant is output through the supernatant outlet of the settling tank 3 and enters the supernatant filter 4 through the inlet of the supernatant filter 4, where it undergoes the first filtration treatment to obtain the first liquid phase and filter residue.

[0126] The filter residue is output through the filter residue outlet of the clear liquid filter 4 and enters the dryer 5 through the inlet of the dryer 5. It undergoes a second drying process in the dryer 5 to obtain a second dry powder and a third gas phase.

[0127] The first liquid phase is output from the liquid phase outlet of the clear liquid filter 4 and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0128] The present invention uses a supernatant filter 4 to perform a first filtration treatment on the supernatant, and then uses a dryer 5 to perform a second drying treatment on the filter residue after the first filtration treatment, which can further recover chlorosilanes in the supernatant and improve the recovery rate of chlorosilanes.

[0129] In some embodiments of the present invention, the recovery system further includes: a flash condenser 2;

[0130] The vapor phase outlet of flash tank 1 is connected to the inlet of flash condenser 2, the liquid phase outlet of flash condenser 2 is connected to flash tank 1, and the vapor phase outlet of flash condenser 2 is connected to the inlet of clear liquid tank 7.

[0131] Specifically, the first gas phase is output from the gas phase outlet of flash tank 1 and enters flash condenser 2 through the inlet of flash condenser 2. In flash condenser 2, the first condensation process is carried out to obtain the fourth gas phase and the second liquid phase. The fourth gas phase is output from the outlet of flash condenser 2 and enters clear liquid tank 7 through the inlet of clear liquid tank 7. The second liquid phase is output from the outlet of flash condenser 2 and enters flash tank 1.

[0132] The recovery system also includes: dryer condenser 6;

[0133] The gas phase outlet of dryer 5 is connected to the inlet of dryer condenser 6, and the outlet of dryer condenser 6 is connected to the inlet of clear liquid tank 7.

[0134] Specifically, the second gas phase exits through the gas phase outlet of dryer 5, enters dryer condenser 6 through the inlet of dryer condenser 6, undergoes a second condensation process in dryer condenser 6 to obtain the third liquid phase, and exits through the outlet of dryer condenser 6, enters clear liquid tank 7 through the inlet of clear liquid tank 7; and / or,

[0135] The third gas phase is output from the gas phase outlet of dryer 5 and enters dryer condenser 6 through the inlet of dryer condenser 6. It undergoes a third condensation process in dryer condenser 6 to obtain the fourth liquid phase. The fourth liquid phase is output from the outlet of dryer condenser 6 and enters clear liquid tank 7 through the inlet of clear liquid tank 7.

[0136] Furthermore, the recovery system also includes: a cryogenic cooler 8 and an exhaust gas scrubbing tower;

[0137] The gas phase outlet of the clear liquid tank 7 is connected to the inlet of the cryogenic tank 8, the gas phase outlet of the cryogenic tank 8 is connected to the tail gas scrubbing tower, and the liquid phase outlet of the cryogenic tank 8 is connected to the inlet of the clear liquid tank 7.

[0138] Specifically, the fifth gas phase is output from the gas phase outlet of the clear liquid tank 7 and enters the deep cryostat 8 through the inlet of the deep cryostat 8. It undergoes the fourth condensation treatment in the deep cryostat 8 to obtain the sixth gas phase and the sixth liquid phase. The sixth gas phase is output from the gas phase outlet of the deep cryostat 8 and enters the tail gas scrubbing tower through the inlet of the tail gas scrubbing tower for scrubbing treatment. The sixth liquid phase is output from the liquid phase outlet of the deep cryostat 8 and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0139] Furthermore, the recovery system also includes: a clear liquid distillation column filter 10 and a clear liquid distillation column;

[0140] 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 silicon tetrachloride outlet of the clear liquid distillation tower is connected to the settling tank 3.

[0141] Specifically, the fifth liquid phase is output from 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, undergoes a second filtration process in the clear liquid distillation tower filter 10 to obtain the seventh liquid phase, which is output from the liquid phase outlet of the clear liquid distillation tower filter 10 and enters the clear liquid distillation tower for distillation to obtain silicon tetrachloride, which is output from the silicon tetrachloride outlet of the clear liquid distillation tower and enters the settling tank 3.

[0142] In some embodiments, a clarifying pump 9 is also included, with the liquid phase outlet of the clarifying tank 7 connected to the inlet of the clarifying pump 9, and the outlet of the clarifying pump 9 connected to the inlet of the clarifying distillation column filter 10. The clarifying pump 9 is used to provide pressure to the fifth liquid phase, enabling the fifth liquid phase to enter the clarifying distillation column filter 10.

[0143] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0144] Example 1

[0145] The polycrystalline silicon slag slurry recycling system of this embodiment is as follows: Figure 1 As shown, it includes: flash tank 1, settling tank 3, dryer 5, clear liquid tank 7, clear liquid filter 4, flash condenser 2, dryer condenser 6, cryothermal unit 8, tail gas scrubbing tower, clear liquid distillation tower filter 10, and clear liquid distillation tower.

[0146] The slurry enters the flash tank 1 through the inlet of the flash tank 1. The solid-liquid mixture outlet of the flash tank 1 is connected to the inlet of the settling tank 3. The solid-liquid mixture outlet of the settling tank 3 is connected to the inlet of the dryer 5.

[0147] The vapor phase outlet of flash tank 1 is connected to the inlet of flash condenser 2, the liquid phase outlet of flash condenser 2 is connected to flash tank 1, and the vapor phase outlet of flash condenser 2 is connected to the inlet of clear liquid tank 7.

[0148] The supernatant outlet of settling tank 3 is connected to the inlet of clear liquid filter 4, the filter residue outlet of clear liquid filter 4 is connected to the inlet of dryer 5, and the liquid phase outlet of clear liquid filter 4 is connected to the inlet of clear liquid tank 7.

[0149] The gas phase outlet of dryer 5 is connected to the inlet of dryer condenser 6, and the outlet of dryer condenser 6 is connected to the inlet of clear liquid tank 7.

[0150] The gas phase outlet of the clear liquid tank 7 is connected to the inlet of the cryogenic tank 8, the gas phase outlet of the cryogenic tank 8 is connected to the tail gas scrubbing tower, and the liquid phase outlet of the cryogenic tank 8 is connected to the clear liquid tank 7.

[0151] 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 silicon tetrachloride outlet of the clear liquid distillation tower is connected to the settling tank 3.

[0152] Example 2

[0153] The method for recycling polycrystalline silicon slag slurry in this embodiment uses the recycling system from Embodiment 1, and specifically includes:

[0154] The slurry enters the flash tank 1 through the inlet and undergoes flash treatment in the flash tank 1 to obtain a first solid-liquid mixture and a first gas phase;

[0155] The first gas phase is output from the gas phase outlet of flash tank 1 and enters flash condenser 2 through the inlet of flash condenser 2. It undergoes first condensation treatment in flash condenser 2 to obtain the fourth gas phase and the second liquid phase. The fourth gas phase is output from the outlet of flash condenser 2 and enters clear liquid tank 7 through the inlet of clear liquid tank 7. The second liquid phase is output from the outlet of flash condenser 2 and enters flash tank 1.

[0156] The first solid-liquid mixture is output from the solid-liquid mixture outlet of flash tank 1 and enters settling tank 3 through the inlet of settling tank 3. Settling is carried out in settling tank 3 to obtain the second solid-liquid mixture and supernatant.

[0157] The second solid-liquid mixture is discharged from the solid-liquid mixture outlet of the settling tank 3 and enters the dryer 5 through the inlet of the dryer 5. It undergoes a first drying process in the dryer 5 to obtain a first dry powder and a second gas phase. The supernatant is discharged from the supernatant outlet of the settling tank 3 and enters the clear liquid filter 4 through the inlet of the clear liquid filter 4. It undergoes a first filtration process in the clear liquid filter 4 to obtain a first liquid phase and filter residue. The filter residue is discharged from the filter residue outlet of the clear liquid filter 4 and enters the dryer 5 through the inlet of the dryer 5. It undergoes a second drying process in the dryer 5 to obtain a second dry powder and a third gas phase. The first liquid phase is discharged from the liquid phase outlet of the clear liquid filter 4 and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0158] The second and third gas phases are output from the gas phase outlet of dryer 5 and enter dryer condenser 6 through the inlet of dryer condenser 6. They undergo second and third condensation treatments in dryer condenser 6 to obtain third and fourth liquid phase alkane. The third and fourth liquid phases are output from the outlet of dryer condenser 6 and enter clear liquid tank 7 through the inlet of clear liquid tank 7.

[0159] The first liquid phase, the fourth gas phase, the third liquid phase, and the fourth liquid phase will form a fifth liquid phase and a fifth gas phase in the clear liquid tank 7;

[0160] The fifth gas phase is output from the gas phase outlet of the clear liquid tank 7 and enters the deep cryostat 8 through the inlet of the deep cryostat 8. It undergoes the fourth condensation treatment in the deep cryostat 8 to obtain the sixth gas phase and the sixth liquid phase. The sixth gas phase is output from the gas phase outlet of the deep cryostat 8 and enters the tail gas scrubbing tower through the inlet of the tail gas scrubbing tower for scrubbing treatment. The sixth liquid phase is output from the liquid phase outlet of the deep cryostat 8 and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0161] The fifth liquid phase is output from the liquid phase outlet of the clear liquid tank 7, enters the clear liquid pump 9 through the inlet of the clear liquid pump 9, and then is output from the outlet of the clear liquid pump 9. It enters the clear liquid distillation tower filter 10 through the inlet of the clear liquid distillation tower filter 10 and undergoes a second filtration process in the clear liquid distillation tower filter 10 to obtain the seventh liquid phase. The seventh liquid phase is output from the liquid phase outlet of the clear liquid distillation tower filter 10 and enters the clear liquid distillation tower for distillation to obtain silicon tetrachloride. The silicon tetrachloride is output from the silicon tetrachloride outlet of the clear liquid distillation tower and enters the settling tank 3.

[0162] The flash evaporation process is a continuous flash evaporation process, with a temperature of 70℃ and a pressure of 0.06 MPaG.

[0163] During the settling treatment, the temperature was 15℃, the time was 6 hours, and the pressure was 0.06 MPaG.

[0164] In the first drying process, the temperature was 98℃, the time was 6 hours, and the pressure was 0.05 MPaG.

[0165] In the second drying process, the temperature was 98℃, the time was 6 hours, and the pressure was 0.05 MPaG.

[0166] The first filtration process is a continuous filtration process. In the first filtration process, the filtration accuracy is 1μm, the temperature is 15℃, and the pressure is 0.7MPaG.

[0167] In the first condensation process, the temperature is 40–70°C and the pressure is 0.06 MPaG;

[0168] In the second condensation process, the temperature is 40–98°C and the pressure is 0.04 MPaG;

[0169] In the third condensation process, the temperature is 40–98℃ and the pressure is 0.04 MPaG;

[0170] In the fourth condensation process, the temperature is -15 to 40°C and the pressure is 0.04 MPaG.

[0171] The second filtration process is a continuous filtration process. In the second filtration process, the filtration accuracy is 1μm, the temperature is 40℃, and the pressure is 0.75MPaG.

[0172] The distillation process was continuous, with a temperature of 112℃ and a pressure of 0.08 MPaG.

[0173] The slurry may contain the following components by mass percentage: 1.59% silica fume, 0.5% metal chloride, 5% polychlorosilane, 73.9% silicon tetrachloride, 19% trichlorosilane, and 0.01% dichlorosilane.

[0174] Example 3

[0175] The method for recycling polycrystalline silicon slag slurry in this embodiment includes:

[0176] The slurry enters the flash tank 1 through the inlet and undergoes flash treatment in the flash tank 1 to obtain a first solid-liquid mixture and a first gas phase;

[0177] The first gas phase is output from the gas phase outlet of flash tank 1 and enters flash condenser 2 through the inlet of flash condenser 2. It undergoes first condensation treatment in flash condenser 2 to obtain the fourth gas phase and the second liquid phase. The fourth gas phase is output from the outlet of flash condenser 2 and enters clear liquid tank 7 through the inlet of clear liquid tank 7. The second liquid phase is output from the outlet of flash condenser 2 and enters flash tank 1.

[0178] The first solid-liquid mixture is output from the solid-liquid mixture outlet of flash tank 1 and enters settling tank 3 through the inlet of settling tank 3. Settling is carried out in settling tank 3 to obtain the second solid-liquid mixture and supernatant.

[0179] The second solid-liquid mixture is output from the solid-liquid mixture outlet of the settling tank 3 and enters the dryer 5 through the inlet of the dryer 5. It undergoes the first drying process in the dryer 5 to obtain the first dry powder and the second gas phase. The supernatant is output from the supernatant outlet of the settling tank 3 and enters the clear liquid tank 7 through the inlet of the clear liquid tank 7.

[0180] The second gas phase is output from the gas phase outlet of dryer 5 and enters dryer condenser 6 through the inlet of dryer condenser 6. It undergoes a second condensation process in dryer condenser 6 to obtain the third liquid phase. The third liquid phase is output from the outlet of dryer condenser 6 and enters clear liquid tank 7 through the inlet of clear liquid tank 7.

[0181] The first liquid phase, the fourth gas phase, and the third liquid phase will form a fifth liquid phase and a fifth gas phase in the clear liquid tank 7;

[0182] The fifth gas phase is output from the gas phase outlet of the clear liquid tank 7 and enters the tail gas scrubbing tower through the inlet of the tail gas scrubbing tower for scrubbing treatment.

[0183] The fifth liquid phase is output from the liquid phase outlet of the clear liquid tank 7, enters the clear liquid pump 9 through the inlet of the clear liquid pump 9, and then enters the clear liquid distillation tower through the outlet of the clear liquid pump 9 for distillation treatment to obtain silicon tetrachloride. The silicon tetrachloride is output from the silicon tetrachloride outlet of the clear liquid distillation tower and enters the settling tank 3.

[0184] The flash evaporation process is a continuous flash evaporation process, with a temperature of 73℃ and a pressure of 0.06 MPaG.

[0185] During the settling treatment, the temperature was 40℃, the time was 8 hours, and the pressure was 0.06 MPaG.

[0186] In the first drying process, the temperature was 120℃, the time was 6 hours, and the pressure was 0.05 MPaG.

[0187] In the first condensation process, the temperature is 40–73°C and the pressure is 0.06 MPaG;

[0188] In the second condensation process, the temperature is 40–120°C and the pressure is 0.05 MPaG;

[0189] The distillation process was continuous, and the temperature was 135℃ and the pressure was 0.1 MPaG.

[0190] The slurry may contain the following components by mass percentage: 1.1% silica fume, 3.2% metal chlorides, 2.9% polychlorosilanes, 84.2% silicon tetrachloride, 8.5% trichlorosilane, and 0.1% dichlorosilane.

[0191] Compared to Example 3, Example 2 uses a supernatant filter for the first filtration treatment to obtain filter residue, which is then subjected to a second drying treatment. Furthermore, a supernatant distillation column filter is used for the second filtration treatment before the distillation treatment, and a cryogenic condenser is used for the fourth condensation treatment before the washing treatment. This prevents silica powder in the supernatant from accumulating in the distillation column bottom, reduces corrosion of the reboiler, prevents reboiler heat exchanger tube leakage, extends the reboiler's service life, and reduces the reboiler's replacement frequency. The cryogenic condensation treatment also allows for the recovery of some chlorosilanes, increasing the chlorosilane recovery rate, reducing the scrubbing load on the washing column, and saving washing water. Compared to Example 3, the chlorosilane recovery rate in Example 2 is increased by 11%, and the wastewater volume is reduced by half.

[0192] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. The above are merely 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 within the scope of protection of the present invention.

Claims

1. A method for recycling polycrystalline silicon slag slurry, characterized in that, Includes the following steps: The slurry is subjected to flash evaporation to obtain a first solid-liquid mixture and a first gas phase; The first solid-liquid mixture is subjected to sedimentation treatment to obtain a second solid-liquid mixture and a supernatant. The second solid-liquid mixture is subjected to a first drying treatment to obtain a first dry powder and a second gas phase; Collect the first gas phase and the second gas phase; The supernatant is subjected to a first filtration process to obtain a first liquid phase and filter residue; The filter residue is subjected to a second drying treatment to obtain a second dry powder and a third gas phase; Collect the first liquid phase and the third gas phase; The first gas phase is subjected to a first condensation treatment to obtain a fourth gas phase and a second liquid phase. The fourth gas phase is collected, and the second liquid phase is allowed to participate in flash evaporation treatment. And / or, The second gas phase is subjected to a second condensation treatment to obtain a third liquid phase, and the third liquid phase is collected. And / or, The third gas phase is subjected to a third condensation treatment to obtain a fourth liquid phase, and the fourth liquid phase is collected. The first liquid phase, the fourth gas phase, the third liquid phase, and the fourth liquid phase are all introduced into a clear liquid tank to obtain a fifth liquid phase and a fifth gas phase; The fifth gas phase is subjected to a fourth condensation treatment to obtain a sixth gas phase and a sixth liquid phase; The sixth gas phase is washed to return the sixth liquid phase to the clear liquid tank; The fifth liquid phase is subjected to a second filtration process to obtain a seventh liquid phase, and the seventh liquid phase is subjected to distillation to obtain silicon tetrachloride; The silicon tetrachloride is then involved in the sedimentation process.

2. The recycling method according to claim 1, characterized in that, In the flash evaporation process, the temperature is 35~165℃ and the pressure is 0.05~1.5MPaG; and / or, In the sedimentation treatment, the temperature is 0~35℃, the time is 2~8h, and the pressure is 0.05~0.7MPaG; And / or, In the first drying process, the temperature is 70~120℃, the time is 2~8h, and the pressure is 0.02~0.08MPaG; And / or, In the second drying process, the temperature is 70~120℃, the time is 2~8h, and the pressure is 0.02~0.08MPaG; And / or, In the first filtration process, the filtration accuracy is 1~3μm, the temperature is 0~35℃, and the pressure is 0.1~0.7MPaG; and / or, In the first condensation process, the temperature is 40~80℃, and the pressure is 0.04~1.5MPaG; and / or, In the second condensation process, the temperature is 40~120℃ and the pressure is 0.02~0.08MPaG; and / or, In the third condensation process, the temperature is 40~120℃ and the pressure is 0.02~0.08MPaG; and / or, In the fourth condensation process, the temperature is -15~40℃ and the pressure is 0.02~0.08MPaG; And / or, In the second filtration process, the filtration accuracy is 1~3μm, the temperature is 0~50℃, and the pressure is 0.1~1.5MPaG; and / or, In the distillation process, the temperature is 80~150℃ and the pressure is 0.08~0.2MPaG.

3. A recycling system for implementing the recycling method according to any one of claims 1-2, characterized in that, include: Flash tanks, settling tanks, dryers, and clarified liquid tanks; The slurry enters the flash tank through the inlet of the flash 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 gas phase outlet of the flash evaporator is connected to the inlet of the clear liquid tank, and the gas phase outlet of the dryer is connected to the inlet of the clear liquid tank.

4. The recycling system according to claim 3, characterized in that, Also includes: Clear liquid filter, The supernatant outlet of the settling tank is connected to the inlet of the clear liquid filter, the filter residue outlet of the clear liquid filter is connected to the inlet of the dryer, and the liquid phase outlet of the clear liquid filter is connected to the inlet of the clear liquid tank.

5. The recycling system according to claim 3 or 4, characterized in that, Also includes: Flash condenser; The gas phase outlet of the flash tank is connected to the inlet of the flash condenser, the liquid phase outlet of the flash condenser is connected to the flash tank, and the gas phase outlet of the flash condenser is connected to the inlet of the clear liquid tank. And / or, Also includes: dryer condenser; The gas phase outlet of the dryer is connected to the inlet of the dryer condenser, and the outlet of the dryer condenser is connected to the inlet of the clear liquid tank; and / or, It also includes: cryogenic equipment and exhaust gas scrubbing tower; The gas phase outlet of the clarified liquid tank is connected to the inlet of the cryogenic unit, the gas phase outlet of the cryogenic unit is connected to the tail gas scrubbing tower, and the liquid phase outlet of the cryogenic unit is connected to the clarified liquid tank; and / or, It also includes: a clear liquid distillation column filter and a clear liquid distillation column; The liquid phase outlet of the clear liquid tank is connected to the inlet of the clear liquid distillation tower filter, the liquid phase outlet of the clear liquid distillation tower filter is connected to the clear liquid distillation tower, and the silicon tetrachloride outlet of the clear liquid distillation tower is connected to the settling tank.

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