A system and method for recycling polycrystalline silicon slag slurry

Abstract

This invention provides a system and method for recovering polycrystalline silicon slurry. The polycrystalline silicon slurry recovery system includes: a flash tank, a settling tank, a dryer, a dryer condenser, a scrubbing tower, and a clarified liquid tank. The slurry enters the flash tank through its inlet; the flash tank's gas phase outlet is connected to the clarified liquid tank's inlet; the flash tank's solid-liquid mixture outlet is connected to the settling tank's inlet; the settling tank's solid-liquid mixture outlet is connected to the dryer's inlet; the clarified liquid tank's outlet is connected to the scrubbing tower's liquid phase inlet; the dryer's gas phase outlet is connected to the scrubbing tower's gas phase inlet; the scrubbing tower's liquid phase outlet is connected to the clarified liquid tank's inlet; the scrubbing tower's gas phase outlet is connected to the dryer condenser's inlet; and the dryer condenser's outlet is connected to the clarified liquid tank's inlet. This recovery system can efficiently separate the solid and liquid phases in the slurry, recovering chlorosilanes and dry powder from the slurry, and also avoids silicon powder clogging problems in subsequent equipment.

Description

Technical Field

[0001] This invention relates to a polycrystalline silicon slag slurry recovery system and method, 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 polycrystalline silicon slag slurry recovery system. This recovery system can efficiently separate the solid and liquid phases in the slurry, realize the recovery of chlorosilanes and dry powder in the slurry, and also avoid silicon powder clogging problems in subsequent equipment.

[0005] This invention provides a method for recycling polycrystalline silicon slag slurry using the aforementioned recycling system. This recycling method is simple to operate and suitable for widespread application.

[0006] This invention provides a polycrystalline silicon slag slurry recycling system, comprising: 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. 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 connected to the liquid phase inlet of the washing tower, the gas phase outlet of the dryer is connected to the gas phase inlet of the washing tower, the liquid phase outlet of the washing tower is connected to the inlet of the clear liquid tank, the gas phase outlet of the washing tower 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.

[0009] The recycling system described above further includes: a clarified liquid filter.

[0010] 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.

[0011] The recovery system described above further includes: a flash condenser;

[0012] 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.

[0013] The recovery system described above further includes: a clear liquid distillation tower filter and a clear liquid distillation tower;

[0014] The 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.

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

[0016] In the recycling system described above, the temperature in the settling tank is 0–35°C, the time is 2–8 hours, and the pressure is 0.05–0.7 MPaG.

[0017] In the recovery system described above, the dryer is maintained at 70–120°C for 2–8 hours and at a pressure of 0.02–0.08 MPaG.

[0018] In the recovery system described above, the clarified liquid filter has a filtration accuracy of 1–3 μm, a temperature of 0–35 °C, and a pressure of 0.1–0.7 MPaG; and / or,

[0019] The flash condenser operates at 40–90°C and a pressure of 0.04–1.5 MPaG.

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

[0021] This invention provides a method for recycling polycrystalline silicon slag slurry, wherein the recycling method is carried out using a recycling system as described above.

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

[0023] The polycrystalline silicon slag slurry recovery method of the present invention uses the above-mentioned recovery system. This recovery method can efficiently separate the solid and liquid phases in the slurry, realize the recovery of chlorosilanes and dry powder in the slurry, improve the resource utilization efficiency, and also avoid the silicon powder blockage problem in subsequent equipment. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a schematic diagram of a polycrystalline silicon slag slurry recycling system in some embodiments of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1: Flash evaporator;

[0028] 2: Flash condenser;

[0029] 3: Settling tank;

[0030] 4: Clear liquid filter;

[0031] 5: Dryer;

[0032] 6: Dryer condenser;

[0033] 7: Clear liquid tank;

[0034] 8: Scrubber tower;

[0035] 9: Clear liquid pump;

[0036] 10: Clarified liquid distillation tower filter. Detailed Implementation

[0037] 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.

[0038] Figure 1 This is a schematic diagram of a polycrystalline silicon slag slurry recovery system in some embodiments of the present invention. For example... Figure 1 As shown, the first aspect of the present invention provides a polycrystalline silicon slag 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. 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 inlet of the scrubbing tower 8, the gas outlet of the dryer 5 is connected to the gas inlet of the scrubbing tower 8, the liquid outlet of the scrubbing tower 8 is connected to the inlet of the clear liquid tank 7, the gas outlet of the scrubbing 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] 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.

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

[0043] The second solid-liquid mixture is discharged from the solid-liquid mixture outlet of settling tank 3 and enters dryer 5 through the inlet of dryer 5. It undergoes drying in dryer 5 to obtain dry powder (mainly including silicon powder, metal chlorides, and trace amounts of polychlorosilane) and a second gas phase (mainly including chlorosilanes, metal chlorides, and trace amounts of silicon powder). The second gas phase is discharged from the gas phase outlet of dryer 5 and enters scrubbing tower 8 through the gas phase inlet of scrubbing tower 8. The chlorosilane solution is discharged from the outlet of clear liquid tank 7 and enters scrubbing tower 8 through the liquid phase inlet of scrubbing tower 8. In scrubbing tower 8... The second gas phase is washed with a chlorosilane solution to remove silicon powder. The resulting chlorosilane solution containing silicon powder is then output from the liquid phase outlet of the washing tower 8 and enters the clear liquid tank 7 through the bottom. The third gas phase obtained after washing is then output from the gas phase outlet of the washing tower 8 and enters the dryer condenser 6 through the inlet. It is then condensed in the dryer condenser 6 to form liquid chlorosilane. The liquid chlorosilane is then output from the outlet of the dryer condenser 6 and enters the clear liquid tank 7 through the inlet.

[0044] In this invention, the flash tank can operate intermittently or continuously. The scrubbing tower operates continuously.

[0045] It is understandable 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 chlorosilane solution and the bottom of the clear liquid tank 7 is enriched with silicon powder.

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

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

[0048] 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.

[0049] The supernatant obtained after treatment in settling tank 3 still contains a small amount of solid phase. Therefore, the supernatant can be output through the supernatant outlet of settling tank 3 and enter the clear liquid filter 4 through the inlet of clear liquid filter 4 for filtration treatment to separate the solid and liquid in the supernatant. The resulting filter residue is output through the filter residue outlet of clear liquid filter 4 and enters the dryer 5 through the inlet of dryer 5. The resulting liquid chlorosilane is output through the liquid phase outlet of clear liquid filter 4 and enters the clear liquid tank 7 through the inlet of clear liquid tank 7 for storage.

[0050] In some implementations, the clear liquid filter operates continuously.

[0051] This invention uses a supernatant filter 4 to filter the supernatant, which can better separate the solid and liquid phases in the supernatant. The obtained liquid chlorosilane can be reused, and the obtained filter residue can be dried to obtain dry powder, which can also be recycled, thus improving the efficiency of resource utilization.

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

[0053] 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.

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

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

[0056] In some embodiments of the present invention, the recovery system further includes: 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 outlets of the clear liquid distillation tower for light components such as silicon tetrachloride and trichlorosilane are connected to the settling tank 3.

[0058] Specifically, liquid chlorosilane is output from the liquid outlet of the clear liquid tank 7 and enters the clear liquid distillation tower filter 10 through the inlet of the clear liquid distillation tower filter 10. It is filtered in the clear liquid distillation tower filter 10 to obtain pure liquid chlorosilane. The pure liquid chlorosilane is output from the liquid outlet of the clear liquid distillation tower filter 10 and enters the clear liquid distillation tower for distillation to obtain light components such as silicon tetrachloride and trichlorosilane. The light components such as silicon tetrachloride and trichlorosilane are output from the outlet of the clear liquid distillation tower and enter the settling tank 3.

[0059] This invention utilizes a distillation column feed filter and a clear liquid distillation column to process the liquid-phase chlorosilane output from the clear liquid tank 7, thereby separating light components such as silicon tetrachloride and trichlorosilane from the liquid-phase chlorosilane, further improving resource utilization efficiency. Furthermore, allowing the silicon tetrachloride, trichlorosilane, and other light components to enter the settling tank 3 for settling treatment increases the liquid content in the first solid-liquid mixture and allows for rinsing and dilution of the first solid-liquid mixture, promoting the separation of the second solid-liquid mixture from the supernatant during settling treatment, and improving the efficiency of the settling process.

[0060] 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 for the liquid chlorosilane, allowing the liquid chlorosilane to enter the clarifying distillation column filter 10.

[0061] Furthermore, the present invention can also select parameters in each structural unit to further improve 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 settling tank 3, the temperature is 0–35℃, the time is 2–8 hours, and the pressure is 0.05–0.7 MPaG.

[0063] In dryer 5, the temperature is 70–120℃, the time is 2–8h, and the pressure is 0.02–0.08MPaG.

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

[0065] In flash condenser 2, the temperature is 40–90℃ (temperature decreases from 90℃ to 40℃), and the pressure is 0.04–1.5 MPaG.

[0066] In scrubbing tower 8, the temperature is 15–100℃ and the pressure is 0.02–0.08 MPaG.

[0067] A second aspect of the present invention provides a method for recycling polycrystalline silicon slag slurry, the recycling method being carried out using the recycling system of the first aspect.

[0068] The polycrystalline silicon slag slurry recovery method of the present invention uses the above-mentioned recovery system. This recovery method can efficiently separate the solid and liquid phases in the slurry, realize the recovery of chlorosilanes and dry powder in the slurry, improve the resource utilization efficiency, and also avoid the silicon powder blockage problem in subsequent equipment.

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

[0070] Example 1

[0071] 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, washing tower 8, clear liquid pump 9, clear liquid distillation tower filter 10, and clear liquid distillation tower.

[0072] The slurry enters the flash tank 1 through the inlet. 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. 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. 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 connected to the liquid phase inlet of the scrubbing tower 8, the gas phase outlet of the dryer 5 is connected to the gas phase inlet of the scrubbing tower 8, the liquid phase outlet of the scrubbing tower 8 is connected to the inlet of the clear liquid tank 7, the gas phase outlet of the scrubbing 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.

[0074] The outlet of the clear liquid tank 7 is connected to the inlet of the clear liquid pump 9, the outlet of the clear liquid pump 9 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.

[0075] Flash tank 1 operates continuously, with a temperature of 85°C and a pressure of 0.08 MPaG.

[0076] In settling tank 3, the temperature was 25℃, the time was 6 hours, and the pressure was 0.05 MPaG;

[0077] In dryer 5, the temperature is 120℃, the time is 6 hours, and the pressure is 0.05 MPaG;

[0078] The clear liquid filter 4 is a continuous filter with a filtration accuracy of 1μm and a temperature of 25℃.

[0079] In flash condenser 2, the temperature is 50–85℃ and the pressure is 0.08 MPaG;

[0080] The washing tower 8 is for continuous washing. The temperature in the washing tower 8 is 40℃ and the pressure is 0.05MPaG.

[0081] Example 2

[0082] The method for recycling polycrystalline silicon slag slurry in this embodiment uses the recycling system from Embodiment 1, and specifically includes:

[0083] The slurry enters flash tank 1 through the inlet and undergoes flash evaporation. The resulting first solid-liquid mixture (mainly comprising chlorosilanes, metal chlorides, polychlorosilanes, and silicon powder) and a first gas phase (mainly comprising chlorosilanes and polychlorosilanes) are then discharged through the gas phase outlet of flash tank 1 and enter flash condenser 2 through the inlet. In flash condenser 2, the first gas phase undergoes condensation treatment. The resulting non-condensable gas containing chlorosilanes is discharged through the gas phase outlet of flash condenser 2 and exits through the inlet of clear liquid tank 7. The liquid phase containing some impurities and polychlorosilane is obtained after condensation in the clear liquid tank 7. It is then output through the liquid phase outlet of the flash condenser 2 and enters the flash tank 1 through the inlet to participate in the flash evaporation process. 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 to undergo settling treatment, resulting in a second solid-liquid mixture (mainly containing silicon powder, metal chloride, chlorosilane, and a small amount of polychlorosilane) and a supernatant (mainly containing chlorosilane, polychlorosilane, and trace amounts of silicon powder).

[0084] The supernatant is output from the supernatant outlet of the settling tank 3, enters the supernatant filter 4 through the inlet of the supernatant filter 4, and is filtered in the supernatant filter 4. The resulting filter residue is output from the filter residue outlet of the supernatant filter 4, enters the dryer 5 through the inlet of the dryer 5, and the resulting liquid chlorosilane is output from the liquid phase outlet of the supernatant filter 4, enters the supernatant tank 7 through the inlet of the supernatant tank 7 and is stored therein.

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

[0086] Liquid chlorosilane is output from the liquid 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 output from the liquid outlet of the clear liquid distillation tower filter 10 and enters the clear liquid distillation tower for distillation to obtain light components such as silicon tetrachloride and trichlorosilane. The light components such as silicon tetrachloride and trichlorosilane are output from the outlet of the clear liquid distillation tower and enter the settling tank 3.

[0087] The slurry, by mass percentage, may include: 2.75% silica fume, 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 polycrystalline silicon slag slurry in this comparative example is basically the same as that in Example 2, except that:

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

[0091] Compared to Example 2, the second gas phase, which was not washed in the scrubbing tower, caused metal chlorides to gradually precipitate in the pipeline due to temperature changes, clogging the pipeline and further clogging the dryer condenser 6. This resulted in poor dryer operation and frequent replacement of the dryer condenser 6. The service life of the dryer condenser 6 was greatly shortened, requiring replacement and disassembly of the dryer gas phase pipeline in less than a month, which affected the normal operation of slurry treatment in actual production.

[0092] 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 polycrystalline silicon slag slurry recycling system, characterized in that, include: Flash tanks, settling tanks, dryers, dryer condensers, scrubbing towers, 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. 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 connected to the liquid phase inlet of the washing tower, the gas phase outlet of the dryer is connected to the gas phase inlet of the washing tower, the liquid phase outlet of the washing tower is connected to the inlet below the clear liquid tank, the gas phase outlet of the washing tower is connected to the inlet of the dryer condenser, and the outlet of the dryer condenser is connected to the inlet above the clear liquid tank. In the washing tower, a chlorosilane solution washes the second gas phase output from the gas phase outlet of the dryer to remove silicon powder from the second gas phase; In the clear liquid tank, the chlorosilane solution settles, so that the top of the clear liquid tank is enriched with chlorosilane solution and the bottom is enriched with silicon powder.

2. The recycling system according to claim 1, 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.

3. The recycling system according to claim 2, 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.

4. The recycling system according to any one of claims 1-3, characterized in that, Also includes: Clarified liquid distillation column filter and clear liquid distillation column; The 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.

5. The recycling system according to any one of claims 1-3, characterized in that, The flash tank has a temperature of 35~165℃ and a pressure of 0.05~1.5MPaG.

6. The recycling system according to any one of claims 1-3, characterized in that, The settling tank is maintained at a temperature of 0-35°C for 2-8 hours and a pressure of 0.05-0.7 MPaG.

7. The recycling system according to any one of claims 1-3, characterized in that, The dryer is set at 70~120℃ for 2~8 hours and at a pressure of 0.02~0.08 MPaG.

8. The recycling system according to claim 3, characterized in that, The clarified liquid filter has a filtration accuracy of 1~3μm, a temperature of 0~35℃, and a pressure of 0.1~0.7MPaG; and / or, The flash condenser operates at 40~90℃ and a pressure of 0.04~1.5MPaG.

9. The recycling system according to any one of claims 1-3, characterized in that, The temperature in the washing tower is 15~100℃ and the pressure is 0.02~0.08MPaG.

10. A method for recycling polycrystalline silicon slag slurry, characterized in that, The recycling method is carried out using the recycling system described in any one of claims 1-9.

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