A slag slurry high-boiling recovery system

Abstract

The utility model provides a kind of slurry high-boiling recovery system, it is related to polysilicon production technical field.The utility model includes the sedimentation unit of sequential intercommunication, high-boiling removal unit, high-boiling cracking and rectification unit, the high-boiling removal unit includes high-boiling removal tower, the sedimentation unit is to high-boiling settlement and after filtration liquid is sent to the high-boiling removal tower, the high-boiling cracking and rectification unit includes the agitator tank, reaction tank, rectification tower of sequential pipeline intercommunication, the agitator tank with the high-boiling removal tower bottom pipeline intercommunication, the agitator tank top is connected with catalyst pipe, the reaction tank outside is equipped with jacket, the reaction tank bottom is connected with air inlet pipe, and the reaction tank and the agitator tank are all equipped with stirring mechanism.The utility model improves slurry recovery rate, reduces comprehensive silicon consumption, reduces production cost.

Description

Technical Field

[0001] This utility model relates to the field of polycrystalline silicon production technology, specifically to a slurry high-boiling point recovery system. Background Technology

[0002] Currently, the technology used in my country's polysilicon production is primarily the modified Siemens process, accounting for over 80% of the country's total polysilicon output. A crucial step in the modified Siemens process is cold hydrogenation. Cold hydrogenation involves mixing and heating hydrogen and silicon tetrachloride in a fluidized bed reactor at 530℃-560℃ and 2.5MPa-3.0MPa, where they undergo an endothermic reaction with silicon powder. This reaction requires the addition of a certain proportion of catalyst to improve the conversion rate. The exhaust gas from the reaction undergoes heat recovery, dust removal, washing, and condensation to obtain chlorosilane products, which are then sent to the distillation process for further processing. Unreacted hydrogen is compressed and reused using a circulating hydrogen compressor. The advent of cold hydrogenation effectively converts silicon tetrachloride into trichlorosilane, solving the closed-loop chlorine cycle problem and reducing the overall power consumption of polysilicon production. It is a significant cost-reduction approach in the modified Siemens process for polysilicon production. After the tail gas from the cold hydrogenation reaction is washed by a scrubbing tower, the silicon powder, metal chlorides, high boiling points, etc. in the tail gas are discharged from the bottom of the scrubbing tower to the slurry treatment unit.

[0003] In existing technologies, the high-boiling-point substances emitted from the scrubbing tower cannot be fully recovered by simple distillation technology. The high-boiling-point substances at the bottom of the distillation tower and in the settling tank contain a large amount of chlorosilanes. These two parts undergo hydrolysis, resulting in a slurry recovery rate of about 92%, which is low. This leads to high overall silicon consumption, high water consumption, and a large amount of solid waste generated, resulting in high production costs. Utility Model Content

[0004] The purpose of this invention is to develop a high-boiling point slurry recovery system that improves slurry recovery rate, reduces overall silicon consumption, and lowers production costs.

[0005] This utility model is achieved through the following technical solution:

[0006] A high-boiling-point slurry recovery system, comprising:

[0007] Sequentially connected settling unit, high-boiling point removal unit, high-boiling point cracking and distillation unit;

[0008] The high-boiling point removal unit includes a high-boiling point removal tower. The sedimentation unit sends the liquid to the high-boiling point removal tower after sedimentation and filtration of the high-boiling point. The high-boiling point cracking and distillation unit includes a stirred tank, a reaction tank, and a distillation tower connected in sequence by pipelines. The stirred tank is connected to the bottom of the high-boiling point removal tower by a pipeline. A catalyst tube is connected to the top of the stirred tank. The reaction tank is equipped with a jacket on the outside and an air inlet pipe is connected to the bottom of the reaction tank. Both the reaction tank and the stirred tank are equipped with stirring mechanisms.

[0009] Optionally, the top of the high-boiling point removal tower is sequentially connected to a first condenser and a first recovery tank, and the top of the high-boiling point removal tower is connected to a first material pipe. The first recovery tank is connected to the first material pipe and a first pump is installed on the pipe.

[0010] Optionally, the top of the distillation column is sequentially connected to a second condenser and a second recovery tank, and the top of the distillation column is connected to a second material pipe. The second recovery tank is connected to the second material pipe and a second pump is installed on the pipe.

[0011] Optionally, the side and top of the reaction vessel are respectively provided with pipelines that connect to the bottom of the distillation column.

[0012] Optionally, the settling unit includes a collection tank, a settling tank, and a filter connected in sequence by pipelines, and the filter is connected to the pipeline of the deboiling tower.

[0013] Optionally, the filter is provided with multiple layers of filter screens, which are inclined at a 45° angle to the horizontal plane.

[0014] Optionally, the mesh size of the filter screen is 50 mesh to 200 mesh.

[0015] Optionally, the settling tank is connected to the filter at the bottom of the filter screen, the deboiling tower is connected to the filter pipeline at the top of the filter screen, and a backflushing mechanism is provided inside the filter at the top of the filter screen.

[0016] Optionally, the bottom pipeline of the settling tank and filter is connected to a dryer.

[0017] Optionally, the top of the dryer is sequentially connected to a third condenser, a third recovery tank, and a third pump, and the third pump is connected to the pipeline of the high-boiling point removal tower.

[0018] The beneficial effects of this utility model are:

[0019] This invention first removes metal chlorides and silicon powder by settling and filtering high-boiling-point materials. Then, tetrasilicon and trisilicon are removed from the top of the high-boiling-point removal tower, and the purity of high-boiling-point materials at the bottom of the tower reaches more than 90%. Then, a catalyst is added to crack the high-boiling-point materials into small-molecule high-boiling-point substances. The cracked high-boiling-point mixture is then distilled, which solves the problem of high-boiling-point recovery. The overall slurry yield is increased to 99%, which significantly reduces the overall silicon consumption and lowers the production cost. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a system structure diagram of the present invention.

[0022] Reference numerals: 1. Collection tank; 2. Settling tank; 3. Dryer; 4. Filter; 5. Third condenser; 6. Third recovery tank; 7. Third pump; 8. High-boiling point removal tower; 9. First condenser; 10. First recovery tank; 11. First pump; 12. First material pipe; 13. Stirred tank; 14. Reaction tank; 15. Distillation column; 16. Second condenser; 17. Second recovery tank; 18. Second pump; 19. Second material pipe. Detailed Implementation

[0023] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0024] In this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0025] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0026] like Figure 1 As shown, this utility model discloses a high-boiling-point slurry recovery system, including a settling unit, a high-boiling-point removal unit, a high-boiling-point cracking and distillation unit. The settling unit settles and filters the high-boiling-point slurry to remove metal chlorides and silicon powder. Then, the high-boiling-point removal unit removes silicon tetrachloride (tetrasilicon) and trichlorosilane (trisilicon), so that the high-boiling-point purity reaches more than 90%. Finally, the high-boiling-point pyrolysis and distillation unit cracks the high-boiling-point slurry, and then distills the cracked high-boiling-point mixture.

[0027] The settling unit includes a collection tank 1, a settling tank 2, a dryer 3, a third condenser 5, and a third recovery tank 6, which are connected by sequential pipelines. The collection tank 1 collects high-boiling-point materials, which enter the settling tank 2 from the bottom of the collection tank 1 for 1-3 hours of settling. The bottom of the settling tank 2 contains a large amount of silica powder and metal chloride solids, which enter the dryer 3 for processing. The dryer 3 uses 0.4-0.6 MPa steam to heat and evaporate the internal materials. The gas phase at the top of the dryer 3 enters the third condenser 5 and condenses into liquid, which then enters the third recovery tank 6. The slag-containing solids at the bottom of the dryer 3 are sent for hydrolysis treatment.

[0028] A filter 4 is also connected between the settling tank 2 and the dryer 3. The clear liquid at the top of the settling tank 2 enters the filter 4 for filtration, and the solid impurities filtered by the filter 4 are discharged into the dryer 3 for processing.

[0029] The high-boiling-point removal unit includes a high-boiling-point removal tower 8, a filter 4, and a third recovery tank 6 connected to the high-boiling-point removal tower 8 via pipeline. A third pump 7 is installed on the pipeline between the third recovery tank 6 and the high-boiling-point removal tower 8. The clear liquid at the top of the filter 4 enters the high-boiling-point removal tower 8 for treatment, and the liquid in the third recovery tank 6 is pumped into the high-boiling-point removal tower 8 for treatment by the third pump 7.

[0030] Filter 4 is equipped with multiple layers of metal filter screens, which are inclined at a 45° angle to the horizontal plane. The mesh size of the filter screens is 50-200 mesh. The settling tank 2 is connected to the lower part of filter 4, and the high-boiling point removal tower 8 is connected to the upper part of filter 4 via a pipeline. A backflushing mechanism is installed at the top of filter 4 above the filter screen. The backflushing mechanism can backflush the filter screen with nitrogen and clear liquid. High-boiling point particles enter filter 4 from the middle. Solid particles in the high-boiling point are intercepted by the filter screen and deposited at the bottom of filter 4, while clear liquid is discharged upward through the filter screen. To ensure the filtration effect, filter 4 is backflushed periodically with clear liquid and nitrogen, and the deposited and backflushed solid particles are discharged periodically.

[0031] The high-boiling-point removal unit also includes a first condenser 9 and a first recovery tank 10, which are sequentially connected to the top of the high-boiling-point removal tower 8. The top of the high-boiling-point removal tower 8 is connected to a first material pipe 12. The first recovery tank 10 is connected to the first material pipe 12 and a first pump 11 is installed on the pipe. In the high-boiling-point removal tower 8, the material fed in by the settling unit is heated and vaporized, enters the first condenser 9 from the top, condenses into liquid, and then enters the first recovery tank 10. It is then pumped by the first pump 11 to the first material pipe 12. Part of it enters the top of the high-boiling-point removal tower 8 through the first material pipe 12 for re-distillation, and the other part is collected as product. The collected product is silicon tetrachloride and trichlorosilane.

[0032] The high-boiling cracking and distillation unit includes a stirred tank 13, a reaction tank 14, a distillation column 15, a second condenser 16, and a second recovery tank 17, which are connected by sequential pipelines.

[0033] The stirred tank 13 is connected to the bottom pipeline of the high-boiling tower 8, and the top of the stirred tank 13 is connected to the catalyst tube. The high boiling point of about 120-130℃ at the bottom of the high-boiling tower 8 enters the stirred tank 13 and is mixed evenly with the catalyst. The catalyst addition ratio is 1‰~5‰, and the catalyst composition is a mixture of alkylamine and aniline.

[0034] The bottom of the stirred tank 13 is connected to the top of the waste liquid tank via a pipeline. The side and top of the reaction tank 14 are respectively connected to the bottom of the distillation column 15 via pipelines. An inlet pipe is connected to the bottom of the reaction tank 14, and a jacket is installed on the outside of the reaction tank 14. The top of the distillation column 15 is connected to the second condenser 16 via a pipeline. A second material pipe 19 is also connected to the top of the distillation column 15. The second recovery tank 17 is connected to the second material pipe 19 via a pipeline, and a second pump 18 is installed on the pipeline. Both the reaction tank 14 and the stirred tank 13 are equipped with stirring mechanisms.

[0035] The high-boiling point is fed into the reaction tank 14 from the bottom of the stirred tank 13 for reaction. 1.2MPa steam is introduced into the jacket of the reaction tank 14 to maintain the reaction temperature at 145-155℃. At the same time, hydrogen chloride gas with a flow rate of 30-80Nm3 / h is introduced from the bottom of the reaction tank 14 through the gas inlet pipe to crack the high-boiling point. The cracked chlorosilane gas enters the second condenser 16 from the top of the distillation column 15 and is condensed into chlorosilane liquid. Then it enters the second recovery tank 17 and is then transported into the second material pipe 19 through the second pump 18. Part of it enters the top of the distillation column 15 through the second material pipe 19 for re-distillation, and the other part is collected as product. The slag solid at the bottom of the reaction tank 14 is sent for hydrolysis treatment.

[0036] This invention first removes metal chlorides and silicon powder by settling and filtering high-boiling-point materials. Then, tetrasilicon and trisilicon are removed from the top of the high-boiling-point removal tower 8, achieving a high-boiling-point purity of over 90% at the bottom. A catalyst is then added to crack the high-boiling-point materials into smaller molecules. The cracked high-boiling-point mixture is then distilled, solving the high-boiling-point recovery problem and increasing the overall slurry yield to 99%. This significantly reduces overall silicon consumption and lowers production costs.

[0037] The above embodiments are merely preferred embodiments of this utility model and are not intended to limit the technical solutions of this utility model. Any technical solution that can be implemented based on the above embodiments without creative effort should be considered to fall within the scope of protection of this utility model patent.

Claims

1. A high-boiling-point slurry recovery system, characterized in that, include: Sequentially connected settling unit, high-boiling point removal unit, high-boiling point cracking and distillation unit; The high-boiling point removal unit includes a high-boiling point removal tower. The sedimentation unit sends the liquid to the high-boiling point removal tower after sedimentation and filtration of the high-boiling point. The high-boiling point cracking and distillation unit includes a stirred tank, a reaction tank, and a distillation tower connected in sequence by pipelines. The stirred tank is connected to the bottom of the high-boiling point removal tower by a pipeline. A catalyst tube is connected to the top of the stirred tank. The reaction tank is equipped with a jacket on the outside and an air inlet pipe is connected to the bottom of the reaction tank. Both the reaction tank and the stirred tank are equipped with stirring mechanisms.

2. The high-boiling point slurry recovery system according to claim 1, characterized in that, The top of the high-boiling point removal tower is sequentially connected to a first condenser and a first recovery tank. The top of the high-boiling point removal tower is connected to a first material pipe. The first recovery tank is connected to the first material pipe and a first pump is installed on the pipe.

3. The high-boiling point slurry recovery system according to claim 1, characterized in that, The top of the distillation column is sequentially connected to a second condenser and a second recovery tank. The top of the distillation column is also connected to a second material pipe. The second recovery tank is connected to the second material pipe and a second pump is installed on the pipe.

4. The high-boiling point slurry recovery system according to claim 1, characterized in that, The reaction vessel is equipped with pipes on its side and top that connect to the bottom of the distillation column.

5. The high-boiling-point slurry recovery system according to claim 1, characterized in that, The settling unit includes a collection tank, a settling tank, and a filter connected in sequence by pipelines, and the filter is connected to the pipeline of the deboiling tower.

6. The high-boiling point slurry recovery system according to claim 5, characterized in that, The filter contains multiple layers of filter screens, which are inclined at a 45° angle to the horizontal plane.

7. The high-boiling point slurry recovery system according to claim 6, characterized in that, The filter screen has a mesh size of 50 to 200 mesh.

8. The high-boiling point slurry recovery system according to claim 6, characterized in that, The settling tank is connected to the filter at the bottom of the filter screen, the deboiling tower is connected to the filter pipeline at the top of the filter screen, and a backflushing mechanism is provided inside the filter at the top of the filter screen.

9. The high-boiling point slurry recovery system according to claim 5, characterized in that, The settling tank and filter are connected to a dryer via bottom pipes.

10. The high-boiling-point slurry recovery system according to claim 9, characterized in that, The top of the dryer is connected to a third condenser, a third recovery tank, and a third pump via sequential piping. The third pump is connected to the high-boiling point removal tower via piping.

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