A slag slurry impurity removal system for polysilicon production

Abstract

The utility model relates to the polycrystal silicon production technical field discloses a kind of polycrystal silicon production slag slurry impurity removal system, including the sedimentation tank, first filter and hydrolysis tank connected in order along material flow direction, the second import of sedimentation tank is connected with the outlet of phosphorus oxychloride storage tank, the outlet of sedimentation tank is connected with the import of first filter, the first import of first filter is connected with the first outlet of high-boiling tower, the second outlet of first filter is connected with the import of hydrolysis tank, the first outlet of high-boiling tower is connected with the import of first cooler, second import is connected with the outlet of reboiler, second outlet is connected with the import of reboiler;The first outlet of first cooler is connected with the import of waste gas shower device, second outlet is connected with the import of first product liquid tank.The utility model's impurity removal system can dispense with evaporation machine evaporation system, also reduced the amount of metal chloride into reboiler, prolongs the operating cycle of reboiler, and reduces the jam probability of reboiler.

Description

Technical Field

[0001] This utility model relates to the field of polysilicon production technology, and more particularly to the removal of impurities in the slurry treatment process during polysilicon production. More specifically, it relates to a polysilicon production slurry impurity removal system. Background Technology

[0002] In the polysilicon production process, materials containing impurities such as boron, phosphorus, and metal chlorides discharged from the cold hydrogenation, trichlorosilane synthesis, and waste gas treatment units are sent to the settling tank of the slurry treatment unit. After settling and standing for a period of time, the slag at the bottom of the settling tank is discharged to the evaporator for processing, and then the supernatant is collected and sent to the high-boiling point removal tower. The slurry sent to the evaporator is evaporated, and the collected clear liquid is sent to the high-boiling point removal tower for processing. The material containing high concentrations of impurities remaining at the bottom of the evaporator is discharged to the hydrolysis tank for hydrolysis treatment. The material sent to the high-boiling point removal tower is purified by the high-boiling point removal tower, and the condensed and collected clear liquid is sent to the distillation unit. The high-concentration impurity material discharged from the bottom of the high-boiling point removal tower is discharged to the stirring cooling tank for cooling, and then discharged to the hydrolysis tank for hydrolysis treatment.

[0003] The following problems exist in the above slurry treatment process: 1. Metal chlorides dissolve in chlorosilanes, and a large amount of silanes are discharged from the system along with the metal chlorides, resulting in the loss of silicon and chlorine elements. The system has high silicon and chlorine consumption and produces a large amount of acid water, resulting in high pressure on the waste treatment device; 2. The reboiler for removing high-boiling-point waste is prone to clogging in the environment of high concentration of impurities, which leads to a decrease in heat exchange efficiency and the problem of perforation and internal leakage. Summary of the Invention

[0004] To address the problems and shortcomings of the existing technology, this utility model proposes a purification system for the slurry treatment process in polysilicon production. After the slurry containing impurities such as metal chlorides enters the settling tank, it can form a solid adduct with phosphorus oxychloride introduced into the settling tank. After filtration by a filter, the adduct can be removed from the system, eliminating the need for the original evaporator system. At the same time, it can also reduce the amount of metal chlorides entering the reboiler, extend the operating cycle of the reboiler, and reduce the probability of reboiler blockage.

[0005] To achieve the above-mentioned objectives, the technical solution of this utility model is as follows: This invention proposes a polysilicon production slurry impurity removal system, comprising a settling tank, a first filter, and a hydrolysis tank connected sequentially along the material flow direction. The second inlet of the settling tank is connected to the outlet of a phosphorus oxychloride storage tank, the outlet of the settling tank is connected to the inlet of the first filter, the first outlet of the first filter is connected to the first inlet of a high-boiling point removal tower, and the second outlet of the first filter is connected to the inlet of the hydrolysis tank. The high-boiling point removal tower also has a first outlet, a second outlet, and a second inlet. The first outlet of the high-boiling point removal tower is connected to the inlet of a first cooler, the second outlet is connected to the inlet of a reboiler, and the second inlet is connected to the outlet of the reboiler. The first cooler has a first outlet and a second outlet. The first outlet is connected to the inlet of a waste gas scrubbing device, and the second outlet is connected to the inlet of a first product liquid tank.

[0006] Preferably, the slurry impurity removal system further includes a stirring and cooling tank, which has a first inlet and a second inlet. The outlet of the phosphorus oxychloride storage tank is also connected to the second inlet of the stirring and cooling tank, and the first inlet of the stirring and cooling tank is connected to the second outlet of the high-boiling point removal tower.

[0007] Preferably, the slurry impurity removal system further includes a second filter, a pyrolysis reactor, a pyrolysis washing tower, a second cooler, and a second product liquid tank; the outlet of the stirred cooling tank is connected to the first inlet of the second filter, the first outlet of the second filter is connected to the first inlet of the pyrolysis reactor; the second outlet of the second filter is connected to the inlet of the hydrolysis tank; the outlet of the pyrolysis reactor is connected to the inlet of the pyrolysis washing tower, the first outlet of the pyrolysis washing tower is connected to the inlet of the second cooler, the second cooler also has a first outlet and a second outlet, the first outlet is connected to the inlet of the waste gas scrubbing device, and the second outlet is connected to the inlet of the second product liquid tank. Preferably, the pyrolysis vessel also has a hydrogen chloride inlet for receiving hydrogen chloride gas.

[0008] Preferably, the cracking vessel also has a second inlet, which is connected to the outlet of the cracking catalyst storage tank.

[0009] Preferably, the pyrolysis vessel also has a third inlet, which is connected to the second outlet of the pyrolysis scrubbing tower. Preferably, the first filter and the second filter each have a purge gas inlet for receiving purge gas.

[0010] Preferably, the purging gas is nitrogen.

[0011] Preferably, the settling tank has a first inlet for receiving slurry.

[0012] The beneficial effects of this utility model are: 1. This invention introduces phosphorus oxychloride into a settling tank, which forms a solid adduct with the metal chlorosilanes in the chlorosilanes. After filtration, the solid adduct is removed from the system (i.e., the metal chlorides are removed from the slurry treatment system). This removes a large amount of metal chlorides, eliminating the need for evaporation to extract chlorosilanes, thus reducing energy consumption. It also reduces the amount of metal chlorides entering the reboiler, extending its operating cycle and lowering the probability of blockage.

[0013] 2. This invention also adds phosphorus oxychloride to the slag discharged from the bottom of the high-boiling-point tower. This forms a solid adduct with the metallic chlorosilanes in the high-boiling-point material, which is then filtered again. The clean high-boiling-point material after filtration can be directly sent to the cracking reactor for cracking, significantly shortening the process of removing metallic chlorides from chlorosilanes using an evaporator in the original slurry treatment process. Furthermore, the chlorosilanes produced by cracking are collected in the second product tank after being treated by a cracking washing tower and a second cooler, and can be reused in the distillation process, significantly improving the recovery rate and utilization rate of available chlorosilanes in the high-boiling-point material. Attached Figure Description

[0014] The foregoing and hereinafter detailed description of this utility model becomes clearer when read in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the slurry impurity removal system of this utility model; Figure 2 This is a schematic diagram of an existing slurry treatment unit; In the picture: 1. Settling tank; 2. First filter; 3. Hydrolysis tank; 4. Phosphorus oxychloride storage tank; 5. High-boiling point removal tower; 6. Reboiler; 7. First cooler; 8. First product liquid tank; 9. Stirred cooling tank; 10. Second filter; 11. Cracking vessel; 12. Cracking washing tower; 13. Second cooler; 14. Second product liquid tank; 15. Hydrogen chloride inlet; 16. Cracking catalyst storage tank; 17. Evaporator. Detailed Implementation

[0015] To enable those skilled in the art to better understand the technical solutions of this utility model, the following will further illustrate the technical solutions for achieving the purpose of this utility model through several specific embodiments. It should be noted that the technical solutions claimed by this utility model include, but are not limited to, the following embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this utility model.

[0016] This utility model proposes a polycrystalline silicon production slurry impurity removal system, such as... Figure 1As shown, the system includes a settling tank 1, a first filter 2, a hydrolysis tank 3, a phosphorus oxychloride storage tank 4, a high-boiling point removal tower 5, a reboiler 6, a first cooler 7, a first product liquid tank 8, a stirred cooling tank 9, a second filter 10, a pyrolysis reactor 11, a pyrolysis washing tower 12, a second cooler 13, a second product liquid tank 14, and a pyrolysis catalyst storage tank 16; wherein, The settling tank 1 has a first inlet, a second inlet, and an outlet. The first inlet is used to receive impurities containing boron, phosphorus, and metal chlorides discharged from the cold hydrogenation, trichlorosilane synthesis, and waste gas treatment units. These impurities can be collectively referred to as slurry. The second inlet of the settling tank 1 is connected to the outlet of the phosphorus oxychloride storage tank 4 and is used to receive liquid phosphorus oxychloride discharged from the phosphorus oxychloride storage tank 4. The outlet of the settling tank 1 is connected to the inlet of the first filter 2. The first filter 2 also has a first outlet and a second outlet, the first outlet being connected to the first inlet of the high-boiling-point tower 5, and the second outlet of the first filter 2 being connected to the first inlet of the hydrolysis tank 3. The high-boiling-point removal tower 5 also has a first outlet, a second outlet, and a second inlet. The first outlet of the high-boiling-point removal tower 5 is connected to the inlet of the first cooler 7. The first outlet discharges chlorosilane gas into the first cooler 7 for condensation. The second outlet of the high-boiling-point removal tower 5 is connected to the inlet of the reboiler 6. The outlet of the reboiler 6 is connected to the second inlet of the high-boiling-point removal tower 5. Thus, the material at the bottom of the high-boiling-point removal tower 5 enters the reboiler 6 from the bottom pipeline. After being heated by the reboiler 6, it enters the high-boiling-point removal tower 5 again from the top outlet of the reboiler 6 and the second inlet of the high-boiling-point removal tower 5. The outlet of the high-boiling-point removal tower 5 is also connected to the first inlet of the stirring cooling tank 9 for periodic slag discharge to prevent high-boiling-point substances and polychlorosilane from accumulating in the tower bottom. The first cooler 7 also has a first outlet and a second outlet. The first outlet of the first cooler 7 is connected to the inlet of the exhaust gas scrubbing device and is used to send the material discharged from the top of the cooler into the exhaust gas scrubbing device for processing. The second outlet of the first cooler 7 is connected to the inlet of the first product liquid tank 8 and is used to discharge the chlorosilane condensed in the cooler into the first product liquid tank 8 for storage. The stirring and cooling tank 9 also has a second inlet and an outlet. The second inlet is connected to the outlet of the phosphorus oxychloride storage tank 4 to receive liquid phosphorus oxychloride discharged from the phosphorus oxychloride storage tank 4, and the outlet is connected to the inlet of the second filter 10. The second filter 10 has two outlets. Its first outlet is connected to the second inlet of the hydrolysis tank 3, and its second outlet is connected to the first inlet of the pyrolysis vessel 11. The pyrolysis vessel 11 also has a second inlet, a third inlet, and an outlet. The outlet of the pyrolysis vessel 11 is connected to the inlet of the pyrolysis washing tower 12. The second inlet of the pyrolysis vessel 11 is connected to the outlet of the pyrolysis catalyst storage tank 16 for receiving the pyrolysis catalyst discharged from the pyrolysis catalyst storage tank 16. The third inlet of the pyrolysis vessel 11 is connected to the second outlet at the bottom of the pyrolysis washing tower 12. The pyrolysis scrubbing tower 12 also has a first outlet, which is connected to the inlet of the second cooler 13; the second cooler 13 also has a first outlet and a second outlet, the first outlet of the second cooler 13 is connected to the inlet of the waste gas scrubbing device, and the second outlet is connected to the inlet of the second product liquid tank 14, and the chlorosilane condensed in the second cooler 13 is discharged into the second product liquid tank 14 for storage.

[0017] It is understandable that the first inlet of the high boiling point removal tower 5 is the material inlet, the first outlet at the top of the high boiling point removal tower 5 is the gas phase outlet, and the liquid material at the bottom of the high boiling point removal tower 5 flows to the reboiler 6 through the second outlet at the bottom of the high boiling point removal tower 5 and the pipeline. After being heated by the reboiler 6, it enters the high boiling point removal tower 5 from the top outlet of the reboiler 6.

[0018] In some embodiments, the deboiling tower 5 and the pyrolysis washing tower 12 are typically also provided with a spray liquid inlet, which is connected to a spray pipeline.

[0019] In some embodiments, the pyrolysis vessel 11 typically also has a hydrogen chloride inlet 15 for receiving hydrogen chloride gas.

[0020] The working principle of the above-mentioned slurry impurity removal system is as follows: Impurities containing boron, phosphorus, and metal chlorides discharged from the cold hydrogenation, trichlorosilane synthesis, and waste gas treatment units are sent to the settling tank 1 in the slurry treatment unit. Then, liquid phosphorus oxychloride from the phosphorus oxychloride storage tank 4 is added to the settling tank 1, causing it to form a solid adduct with the metal chlorides in the settling tank 1. The solid-liquid mixture in the settling tank 1 is then sent to the first filter 2. After filtration by the first filter 2, the clear liquid is sent to the high-boiling point removal tower 5 for purification through the first inlet of the high-boiling point removal tower 5. The solid adduct filtered out by the first filter 2 is in powder or flake form, which is then pressed into the hydrolysis tank 3 for hydrolysis. The substances entering the high-boiling-point de-isolated column 5, including low-boiling-point chlorosilanes, are discharged from the first outlet at the top into the first cooler 7. During the purification process, the substances enter the reboiler 6 through the second outlet of the high-boiling-point de-isolated column 5, are heated, and then flow back into the high-boiling-point de-isolated column 5 for further purification. Finally, metal chlorides and high-boiling-point substances such as hexachlorodisilane, hexachlorodisiloxane, and polychlorosilane are left at the bottom of the column.

[0021] After purification, the high-boiling-point substances at the bottom of the high-boiling-point tower 5 are discharged through the second outlet at the bottom and sent to the stirred cooling tank 9 for stirring and cooling. Simultaneously, phosphorus oxychloride is added to the stirred cooling tank 9 to form a solid adduct with the remaining metal chlorides. After filtration through the second filter 10, the supernatant is sent to the pyrolysis reactor 11 for further processing. The filtered solids are then sent to the hydrolysis tank 3. The pyrolysis-treated material enters the pyrolysis washing tower 12 and is finally cooled by the second cooler 13 before being stored in the second product liquid tank 14.

[0022] In the embodiments described in this utility model, in previous slurry treatment processes, metal chlorides were dissolved in chlorosilanes. The boiling point difference between chlorosilanes and metal chlorides required an evaporator to evaporate the chlorosilanes, leaving the metal chlorides, thus achieving the effect of removing metal chlorides. However, in the impurity removal system of this utility model, since the metal chlorides and phosphorus oxychloride form a solid substance, they can be removed by filtration, thus eliminating the need for an evaporator.

[0023] In the embodiments described in this utility model, because the content of metal chlorides in the material entering the high-boiling point removal tower 5 is greatly reduced, the temperature of the high-boiling point removal tower 5 can be further increased, thereby increasing the concentration of polychlorosilane, hexachlorodisilane, and hexachlorodisiloxane in the bottom of the tower and decreasing the concentration of silicon tetrachloride. Simultaneously, because the content of metal chlorides in the material entering the high-boiling point removal tower 5 is greatly reduced, the enrichment of metal chlorides in the reboiler 6 is decreased, which can prolong the clogging frequency of the reboiler 6 and reduce the probability of internal corrosion and leakage.

[0024] Furthermore, the first filter 7 and the second filter 10 each have a purge gas inlet for receiving purge gas and a purge gas outlet for discharging purge gas.

[0025] Once the two filters are full, they are disconnected from the slurry removal system. Nitrogen or other purging gases are then introduced into the filters through the designated purging gas inlet to purge them. After purging, the filters are reconnected to the slurry removal system. The purging gas is discharged through the purging gas outlet on the filter.

[0026] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this utility model.

[0027] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0028] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A polycrystalline silicon production slurry impurity removal system, characterized in that, The system includes a settling tank (1), a first filter (2), and a hydrolysis tank (3) connected sequentially along the material flow direction. The second inlet of the settling tank (1) is connected to the outlet of the phosphorus oxychloride storage tank (4). The outlet of the settling tank (1) is connected to the inlet of the first filter (2). The first outlet of the first filter (2) is connected to the first inlet of the high-boiling point removal tower (5). The second outlet of the first filter (2) is connected to the inlet of the hydrolysis tank (3). The high-boiling point removal tower (5) also has a first outlet, a second outlet, and a second inlet. The first outlet of the high-boiling point removal tower (5) is connected to the inlet of the first cooler (7). The second outlet is connected to the inlet of the reboiler (6). The second inlet is connected to the outlet of the reboiler (6). The first cooler (7) has a first outlet and a second outlet. The first outlet is connected to the inlet of the waste gas scrubbing device. The second outlet is connected to the inlet of the first product liquid tank (8).

2. The polycrystalline silicon production slurry impurity removal system according to claim 1, characterized in that, The slurry impurity removal system also includes a stirring and cooling tank (9), which has a first inlet and a second inlet. The outlet of the phosphorus oxychloride storage tank (4) is also connected to the second inlet of the stirring and cooling tank (9), and the first inlet of the stirring and cooling tank (9) is connected to the second outlet of the high-boiling point removal tower (5).

3. The polycrystalline silicon production slurry impurity removal system according to claim 2, characterized in that, The slurry removal system also includes a second filter (10), a pyrolysis vessel (11), a pyrolysis washing tower (12), a second cooler (13), and a second product liquid tank (14); the outlet of the stirring cooling tank (9) is connected to the first inlet of the second filter (10), the first outlet of the second filter (10) is connected to the first inlet of the pyrolysis vessel (11), and the second outlet of the second filter (10) is connected to the inlet of the hydrolysis tank (3); the outlet of the pyrolysis vessel (11) is connected to the inlet of the pyrolysis washing tower (12), the first outlet of the pyrolysis washing tower (12) is connected to the inlet of the second cooler (13), the second cooler (13) also has a first outlet and a second outlet, the first outlet is connected to the inlet of the waste gas scrubbing device, and the second outlet is connected to the inlet of the second product liquid tank (14).

4. The polycrystalline silicon production slurry impurity removal system according to claim 3, characterized in that, The pyrolysis vessel (11) also has a hydrogen chloride inlet (15) for receiving hydrogen chloride gas.

5. A polycrystalline silicon production slurry impurity removal system according to claim 3, characterized in that, The cracking vessel (11) also has a second inlet, which is connected to the outlet of the cracking catalyst storage tank (16).

6. A polycrystalline silicon production slurry impurity removal system according to claim 3, characterized in that, The pyrolysis vessel (11) also has a third inlet, which is connected to the second outlet of the pyrolysis washing tower (12).

7. A polycrystalline silicon production slurry impurity removal system according to claim 3, characterized in that, The first filter (2) and the second filter (10) each have a purge gas inlet for receiving purge gas.

8. A polycrystalline silicon production slurry impurity removal system according to claim 7, characterized in that, The purging gas is nitrogen.

9. A polycrystalline silicon production slurry impurity removal system according to claim 1, characterized in that, The settling tank (1) has a first inlet for receiving slurry.

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