Impurity removal process and system for polycrystalline silicon production

Abstract

The invention discloses an impurity removal process and system for polycrystalline silicon production, the impurity removal system comprises a slurry treatment unit, a packed tower and a cold hydrogenation unit, a discharge port of the slurry treatment unit is connected with the packed tower, the packed tower is at least provided with a tower top discharge port, a side line extraction port and a tower kettle discharge port, the side line extraction port is provided with the cold hydrogenation unit, and the tower kettle discharge port is provided with a tower bottom discharge port. And the tower top discharge port and the tower kettle discharge port are connected with a slag slurry treatment unit. According to the impurity removal system for polycrystalline silicon production, a brand-new process route is designed, components with high impurity content are fed into the slag slurry treatment unit for centralized treatment, the packed tower is designed at the front end of the cold hydrogenation unit, and materials extracted from the side line of the packed tower enter the cold hydrogenation unit, so that the introduction amount of impurities in the cold hydrogenation unit is effectively reduced, and the production efficiency is improved. Therefore, the quality of trichlorosilane in the hydrogenation purification tower of the rectification unit is improved, and high-purity polycrystalline silicon rods are obtained.

Description

Technical Field

[0001] The present application relates to the field of polysilicon production, and specifically to a polysilicon production impurity removal process and system. Background Art

[0002] As a key basic material for semiconductor integrated circuits and solar photovoltaic cells, electronic-grade polysilicon has a wide range of applications, covering multiple strategic emerging industries such as electronics, communications, and new energy. Driven by modern technology, the market demand for electronic-grade polysilicon continues to grow, and it plays a vital role in improving the performance of electronic equipment, promoting the development of the photovoltaic industry, and helping to achieve the "dual carbon" goals.

[0003] The purity of electronic-grade polysilicon products has a decisive influence on their performance and application effects. In semiconductor integrated circuits, a small amount of impurities may cause a significant decline in device performance or even failure; while in solar photovoltaic cells, high-purity polysilicon can significantly improve the photoelectric conversion efficiency. Therefore, the purity requirements for electronic-grade polysilicon are extremely high, usually need to reach more than 99.9999%.

[0004] At present, the modified Siemens method is the mainstream process for producing polysilicon. Its main production processes include trichlorosilane synthesis, cold hydrogenation, distillation, reduction, tail gas, slurry, waste gas treatment, finished product post-processing, etc. Among them, the distillation production process is to separate and purify the crude trichlorosilane from the residual materials of the cold hydrogenation reaction, and the purified high-purity trichlorosilane is sent to the reduction furnace of the reduction process for vapor deposition to produce polysilicon rods. The unreacted materials enter the tail gas workshop with the reduced tail gas for condensation, compression, absorption, and analytical separation, and the separated materials are sent to the cold hydrogenation for recycling. In order to reduce the content of metals and carbon and phosphorus impurities in refined materials, the industry generally uses tail gas, reduction, distillation, cold hydrogenation, adsorption columns for reaction adsorption, or increasing the residual discharge to remove the introduced impurities.

[0005] Although the impurity content can be reduced to a certain extent through multi-stage distillation and other means, it is difficult to deeply remove key impurities such as boron and phosphorus in trichlorosilane due to its complex process flow and equipment limitations. In addition, the existing process also has problems such as high energy consumption, low material utilization rate and unstable product quality.

[0006] Therefore, controlling the impurity content introduced by the incoming materials, improving the efficiency of distillation purification and separation, and continuously improving the technical process route to reduce the impurity content in polysilicon are considered to be the most important focus in polysilicon production and even the entire industry. Summary of the invention

[0007] The purpose of the present application is to provide a polysilicon production process with low impurity content.

[0008] In order to achieve the above objectives, the technical solution adopted in the present application is: to provide an impurity removal system for polysilicon production, comprising a slurry treatment unit, a packed tower and a cold hydrogenation unit, wherein the discharge port of the slurry treatment unit is connected to the packed tower, and the packed tower is at least equipped with a top discharge port, a side line production port and a bottom discharge port, the side line production port is connected to the cold hydrogenation unit, and the top discharge port and the bottom discharge port are connected to the slurry treatment unit.

[0009] As a preferred embodiment, the slurry treatment unit includes a flash evaporator, a distillation tower and a high boiling tank, the discharge port of the flash evaporator is connected to the distillation tower, the light component discharge port of the distillation tower is connected to the packed tower, the tower top discharge port is connected to the flash evaporator, and the tower bottom discharge port is connected to the high boiling tank.

[0010] As another preference, the packed tower is a partition wall packed tower, and the packing is a metal wire mesh.

[0011] As another preference, the cold hydrogenation unit comprises a cold hydrogenation coarse fraction tower, the side line outlet is connected to the cold hydrogenation coarse fraction tower, and the outlet of the cold hydrogenation coarse fraction tower is connected to the distillation unit.

[0012] As another preference, the distillation unit comprises a primary crude distillation tower and a high-low boiling system, the discharge port of the cold hydrogenation crude fraction tower is connected to the primary crude distillation tower, and the discharge port of the high-low boiling system is connected to the packed tower.

[0013] As another preference, the cold hydrogenation unit further comprises a high boiling cracking system, the discharge port of the high boiling cracking system is connected to the flash evaporator, and the light component discharge port of the high boiling tank is connected to the high boiling cracking system.

[0014] As another preferred embodiment, the impurity removal system further comprises a trichlorosilane synthesis unit and a three-waste unit, the heavy fraction discharge port of the trichlorosilane synthesis unit is connected to the slurry treatment unit, and the heavy fraction discharge port of the three-waste unit is connected to the slurry treatment unit.

[0015] As another preferred embodiment, the distillation unit further comprises a mixing tank and a light and heavy miscellaneous tank, the discharge port of the mixing tank is connected to the flash evaporator, the discharge port of the high and low boiling system is connected to the light and heavy miscellaneous tank, and the discharge port of the light and heavy miscellaneous tank is connected to the packed tower.

[0016] The present application also provides an impurity removal process for polysilicon production, wherein the heavy components in the trichlorosilane synthesis unit and the three waste units enter the slurry treatment unit, and the heavy components are initially purified in the slurry treatment unit to obtain a distilled clear liquid, and the distilled clear liquid enters a packed tower for further purification, and the packed tower is configured to have at least a tower top discharge port, a side line production port, and a tower bottom discharge port, the crude trichlorosilane produced by the side line production port enters a cold hydrogenation unit and a distillation unit for further purification, the light components produced by the tower top discharge port are refluxed to the slurry treatment unit for re-purification, and the heavy components produced by the tower bottom discharge port are refluxed to the slurry treatment unit for re-purification.

[0017] Further preferably, the slurry treatment unit is configured to have a flash evaporator, a distillation tower and a high boiling tank, the heavy components in the trichlorosilane synthesis unit and the three waste units enter the flash evaporator and the distillation tower in turn, and a distillate is obtained after purification. The distillate enters the packed tower, the light components extracted from the top discharge port of the tower are refluxed to the flash evaporator for re-purification, and the heavy components extracted from the bottom discharge port of the tower are refluxed to the high boiling tank for purification and separation; the cold hydrogenation unit is configured to have a cold hydrogenation crude fraction tower and a high boiling cracking system, the crude trichlorosilane extracted from the side line outlet enters the cold hydrogenation crude fraction tower and the distillation unit for further purification, the heavy impurities extracted from the high boiling tank enter the high boiling cracking system for decomposition, and the product extracted from the high boiling cracking system re-enters the flash evaporator for purification.

[0018] Compared with the prior art, the beneficial effects of this application are:

[0019] (1) In the impurity removal system for polysilicon production of the present application, materials with high impurity content in each workshop are sent to the slurry treatment unit for unified purification treatment, and then the crude trichlorosilane component is extracted from the side line of the packed tower and sent to the cold hydrogenation unit, thereby reducing the operating load of the cold hydrogenation unit and effectively removing impurities in the crude trichlorosilane;

[0020] (2) The present application takes into account that the impurity content in the extracted materials of the high-low boiling system is low, so the extracted materials directly enter the packed tower, reducing the operating load of the slurry processing unit and reducing resource waste;

[0021] (3) The material extracted from the top outlet of the packed tower of the present application enters the flash evaporator, and the material extracted from the bottom outlet of the tower enters the high boiling tank, which effectively circulates and separates, thereby improving the separation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A doping system for polysilicon production according to an embodiment of the present application;

[0023] Figure 2 A doping system for polysilicon production according to another embodiment of the present application;

[0024] In the figure: 1. Slurry treatment unit; 11. Flash evaporator; 12. Distillation tower; 13. High boiling tank; 2. Packing tower; 3. Cold hydrogenation unit; 31. Cold hydrogenation coarse fractionation tower; 32. High boiling cracking system; 4. Distillation unit; 41. First distillation tower; 42. High and low boiling systems; 43. Mixing tank; 44. Light and heavy miscellaneous tanks; 5. Trichlorosilane synthesis unit; 6. Three waste units. DETAILED DESCRIPTION

[0025] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0026] In the description of the present application, it should be noted that directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating directions and positional relationships are based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of narrating the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of the present application.

[0027] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0028] The terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0029] like Figure 1 As shown, the impurity removal system for polysilicon production of the present application includes a slurry treatment unit 1, a packing tower 2, a cold hydrogenation unit 3, a distillation unit 4, a trichlorosilane synthesis unit 5 and a three-waste unit 6. The heavy impurity liquid outlets in the trichlorosilane synthesis unit 5 and the three-waste unit 6 are connected to the slurry treatment unit 1, the clear liquid outlet of the slurry treatment unit 1 is connected to the packing tower 2, and the product outlet after purification by the packing tower 2 is connected to the cold hydrogenation unit 3, and the crude trichlorosilane outlet of the cold hydrogenation unit 3 is connected to the distillation unit 4. In addition, the heavy impurity component outlets of the packing tower 2, the cold hydrogenation unit 3 and the distillation unit 4 are connected to the slurry treatment unit 1 for re-purification.

[0030] In the impurity removal system for polysilicon production of the present application, through the design of the slurry processing unit 1 and the packed tower 2, the components containing metal impurities and phosphorus impurities are further purified before entering the cold hydrogenation, thereby improving the separation efficiency of impurities, effectively improving the quality of the distillation refined material, and improving the quality of the polysilicon rods.

[0031] In some embodiments, the clear liquid outlet of the slurry treatment unit 1 is connected to the packed tower 2, the side line outlet of the packed tower 2 is connected to the cold hydrogenation unit 3, and the top outlet and the bottom outlet of the packed tower 2 are connected to the slurry treatment unit 1.

[0032] In some preferred embodiments, the packed tower 2 is preferably a partition wall packed tower 2. The partition wall packed tower 2 has the advantage of multi-component separation. The material is Q345R. The filler is a metal wire mesh. It is designed by taking advantage of its high porosity and low pressure drop. The content of the component trichlorosilane is high, while the boiling point is relatively low. It is designed by pressurized distillation. The gas phase at the top of the tower is cooled by a combination of air cooling and water cooling. The feed and its production port are designed in two sections respectively. According to the change of the component, different parts can be used for production and the feed port can be adjusted and controlled in time to achieve the best separation effect. Two coil refluxes are designed for the feed on both sides of the partition. The feed amount on both sides is controlled by controlling the opening of the regulating valves on both sides to ensure that the pressure difference on both sides is close to the same. The heat source is 0.4MPa steam heating. The tower pressure drop is controlled by controlling the steam volume and the tower pressure is stabilized by gas replenishment and pressure relief.

[0033] In the prior art, the impurity content in the material entering the distillation unit 4 from the cold hydrogenation unit 3 is too high. The core problem is that the products in each system are directly connected to the cold hydrogenation unit 3. These materials contain a large amount of impurities that cannot be effectively removed. Therefore, more impurities are introduced into the cold hydrogenation unit 3, resulting in a high impurity content in the distillation unit 4 and the final polysilicon rod product.

[0034] In the impurity removal system for polysilicon production of the present application, materials with high impurity content in each workshop are first sent to the slurry treatment unit 1 for purification treatment, and then components with low impurity content are extracted from the side line of the partition wall packing tower 2 and enter the cold hydrogenation unit 3. At this time, the amount of impurities introduced into the cold hydrogenation unit 3 has been reduced, and the purification difficulty of the cold hydrogenation unit 3 is reduced, so that the impurity content in the produced crude trichlorosilane is further reduced.

[0035] like Figure 2 As shown, in some embodiments, the slurry processing unit 1 includes a flash evaporator 11, a distillation tower 12 and a high boiling tank 13. The outlet of the flashed material of the flash evaporator 11 is connected to the distillation tower 12, the outlet of the distilled clear liquid is connected to the partition wall packing tower 2, and the outlet of the heavy fraction after distillation is connected to the high boiling tank 13.

[0036] The outlet of the light component extracted from the top of the intermediate wall packed tower 2 is connected to the flash evaporator 11, the outlet of the side line extracted material of the intermediate wall packed tower 2 is connected to the cold hydrogenation unit 3, and the outlet of the heavy component extracted from the bottom of the intermediate wall packed tower 2 is connected to the high boiling tank 13.

[0037] The heavy liquid outlet of the trichlorosilane synthesis workshop 5 is connected to the flash evaporator 11. The mixed gas of the trichlorosilane synthesis furnace in the trichlorosilane synthesis workshop 5 enters the flash evaporator 11 through the crude trichlorosilane liquid phase produced by the reflux tank of the washing tower, and the residual liquid discharged from the ground tank of the trichlorosilane synthesis workshop 5 enters the flash evaporator 11.

[0038] The heavy liquid outlet of the three waste systems 6 is connected to the flash evaporator 11. The dusty waste gas, washing tower liquid, other floor trough replacement residual liquid in the three waste systems 6 enter the flash evaporator 11, and the floor trough residual liquid of the tail gas recovery workshop is also sent to the flash evaporator 11.

[0039] The heavy impurity component outlet of the cold hydrogenation unit 3 is connected to the flash evaporator 11, and the heavy impurity component outlet of the distillation unit 4 is connected to the flash evaporator 11. The heavy impurity components produced by the cold hydrogenation unit 3 and the distillation unit 4 are sent back to the flash evaporator 11 for purification and re-purification cycle.

[0040] like Figure 2 As shown, in some embodiments, the cold hydrogenation unit 3 includes a cold hydrogenation crude fractionation tower 31 and a high-boiling cracking system 32, the side line material outlet of the partition wall packing tower 2 is connected to the cold hydrogenation crude fractionation tower 31, and the top material outlet of the cold hydrogenation crude fractionation tower 31 is connected to the distillation unit 4.

[0041] The heavy impurity component outlet of the high boiling cracking system 32 is connected to the flash evaporator 11, and the heavy impurity material outlet of the high boiling tank 13 is connected to the high boiling cracking system 32. The light component material in the high boiling tank 13 is cracked in the high boiling cracking system 32 to obtain low boiling point monomers which enter the flash evaporator 11 for re-purification.

[0042] In some embodiments, the distillation unit 4 includes a crude distillation primary tower 41, a high-low boiling system 42, a mixing tank 43, and a light-heavy miscellaneous tank 44. The crude trichlorosilane outlet of the cold hydrogenation unit 3 is connected to the crude distillation primary tower 41, the discharge port of the mixing tank 43 is connected to the slurry unit 1, the discharge port of the high-low boiling system 42 is connected to the light-heavy miscellaneous tank 44, and the discharge port of the light-heavy miscellaneous tank 44 is connected to the partition wall packing tower 2.

[0043] Specifically, the outlet of the crude trichlorosilane extracted from the top of the cold hydrogenation crude fraction tower 31 is connected to the crude distillation primary tower 41 , and the outlet of the mixing tank 43 is connected to the flash evaporator 11 .

[0044] The synthetic furnace pipeline and filter cleaning replacement material from the trichlorosilane plant, the drain liquid from the waste gas treatment, and the replacement residual liquid from each system in the tail gas recovery tank enter the mixing tank 43, are mixed and buffered in the mixing tank 43, and then enter the flash evaporator 11 for purification.

[0045] The discharge from the distillation tower kettle or the top of the distillation tower in the distillation unit 4 enters the high-low boiling system 42. The light and heavy impurities tank 44 includes a light impurities tank and a heavy impurities tank. The light component impurity outlet of the high-low boiling system 42 is connected to the light impurities tank, and the light impurities tank stores these light components in a centralized manner for subsequent treatment or recycling. The heavy component impurity outlet of the high-low boiling system 42 is connected to the heavy impurities tank, and the heavy impurities tank stores these heavy components in a centralized manner for subsequent treatment or recycling. The extraction outlets of the light impurities tank and the heavy impurities tank are both connected to the packed tower 2.

[0046] The cold hydrogenation unit 3 and the distillation unit 4 also include other conventional devices, which are used for the cold hydrogenation and distillation treatment of trichlorosilane respectively. This application only lists the devices related to the slurry treatment unit 1 and the packed tower 2.

[0047] The present application also provides a polysilicon production impurity removal process:

[0048] The heavy liquid impurities in the trichlorosilane synthesis unit 5 and the three wastes unit 6 enter the slurry treatment unit 1, and the distilled clear liquid with phosphorus and metal impurities enters the packed tower 2 for purification. The packed tower 2 is configured to have at least three outlets, namely, a top extraction pipe of the packed tower 2, a bottom extraction pipe of the packed tower 2, and a side line extraction pipe of the packed tower 2. The material purified by the packed tower 2 is extracted through the side line to the cold hydrogenation unit 3 for further purification, and the remaining material of the packed tower 2 is sent to the slurry treatment unit 1 for re-purification.

[0049] The side-line material of the packed tower 2 is purified in the cold hydrogenation unit 3 and then enters the distillation unit 4 for distillation. The heavy component materials in the cold hydrogenation unit 3 and the distillation unit 4 enter the slurry treatment unit 1 for re-purification.

[0050] The impurity removal process for polysilicon production of the present application collects materials with high impurity content in various links of the polysilicon production system to the slurry treatment unit 1 for centralized treatment, opening up a new process route, and a packing tower 2 is arranged between the slurry treatment unit 1 and the cold hydrogenation unit 3, so as to reduce the impurity content from the raw materials entering the cold hydrogenation unit 3, thereby improving the separation effect of the cold hydrogenation unit 3 and the distillation unit 4, and finally controlling the impurities of the refined material product of the polysilicon rod to be below the level of B≤0.01PPb, P≤0.01PPb, metal impurities≤1PPb, and carbon≤0.5PPm, so that the quality of polysilicon is improved to the industry advanced value and reaches the level of electronic first-class products.

[0051] In a more specific impurity removal process, heavy component liquids with high impurity content such as materials recovered from the waste gas treatment dust removal washing tower, crude trichlorosilane produced by the mixed gas of the trichlorosilane synthesis furnace through the reflux tank of the washing tower, trichlorosilane tank filter cleaning and pipeline replacement discharge residual liquid, tail gas recovery tank filter cleaning and pipeline replacement discharge residual liquid, cold hydrogenation high-boiling cracking distillation reflux tank liquid, etc. enter the flash evaporator 11 of the slurry treatment unit 1.

[0052] The components of crude trichlorosilane material include: 83.58% TCS, 0.05% DCS, 16.04% STC and 0.03% high boiling substances, and the impurity content is about: B≤1785.5PPb, P≤1.7PPb, metal impurities≤2881.43PPb, and Ti content is about 1539.22PPb. The components of cold hydrogenation high boiling cracking and distillation reflux tank liquid include: 36.83% TCS, 40.34% STC, 0.05% DCS and 0.13% high boiling substances, and the impurity content is about: B≤181PPb, P≤14PPb, metal impurities≤76089PPb, and AI content is about 74236PPb.

[0053] The material treated by the flash evaporator 11 in the slurry treatment unit 1 enters the distillation tower 12 for distillation, and the distillation tower 12 distills to obtain a distillation clear liquid material containing phosphorus and metal impurities, wherein the impurities contained in the distillation clear liquid material generally include: B≤153PPb, P≤31.76PPb, metal impurities≤13209PPb, and Al content is about 12085PPb. The heavy component material of the distillation tower 12 enters the high boiling tank 13 for treatment.

[0054] The distillation clear liquid obtained by distillation in the distillation tower 12 enters the packed tower 2 for purification, the material extracted from the side line of the packed tower 2 enters the cold hydrogenation unit 3 and the distillation unit 4 to generate the target product, the material extracted from the top of the packed tower 2 enters the flash evaporator 11 for recovery and re-purification, and the material extracted from the bottom of the packed tower 2 enters the high boiling tank 13.

[0055] The packing tower 2 is preferably a partition wall packing tower 2, made of Q345R, and the packing is a metal wire mesh. The design of the partition wall packing tower 2 can adjust the extraction port and the feed port to achieve the best separation effect.

[0056] The design of the slurry treatment unit 1 and the intermediate wall packed tower 2 of the present application, through the improvement of the process route, crudely distills the high-content impurities before entering the cold hydrogenation unit 3, the top impurity B content of the intermediate wall packed tower 2 is relatively high, and enters the flash evaporator 11 for flash evaporation treatment, the bottom of the intermediate wall packed tower 2 contains high content of metal impurities and carbon impurities, and the discharge from the bottom of the tower enters the high boiling tank 13 for purification and cracking treatment.

[0057] The design of the partition wall packed tower 2 only retains the components extracted from the side line to enter the cold hydrotreating unit 3, thereby reducing the burden of the cold hydrotreating unit 3 and improving the purity of the final refined product.

[0058] The side-line material of the partition wall packing tower 2 enters the cold hydrogenation crude fraction tower 31 for secondary purification, and the material extracted from the cold hydrogenation crude fraction tower 31 enters the crude distillation primary tower 41 of the distillation unit 4 for crude distillation and subsequent distillation.

[0059] In the prior art, the produced materials of each workshop are connected to the cold hydrogenation crude fractionation tower 31 for purification. At this time, the impurity content of the produced material at the top of the cold hydrogenation crude fractionation tower 31 is relatively high, including components: 3.2% DCS, 96.76% TCS, 0.02% STC, and impurities contained: B≤57.61PPb, P≤23.95PPb and metal impurities≤234.7PPb. In the prior art, the load of the cold hydrogenation crude fractionation tower 31 is relatively high, and the impurities of the materials entering the distillation unit 4 cannot be effectively removed, resulting in excessively high impurity content of the final refined material, which reduces the quality of the polysilicon rods.

[0060] The process design of the slurry treatment unit 1 and the partition wall packing tower 2 of the present application effectively improves the impurity removal effect of the front-end system of the cold hydrogenation unit 3, and improves the purification efficiency of the cold hydrogenation rough fractionation tower 31, and improves the quality of the crude trichlorosilane material. The components of the extracted material of the cold hydrogenation rough fractionation tower 31 of the present application are: 3.2% DCS, 96.76% TCS, 0.02% STC, and the impurity content is: B ≤ 20PPb, P ≤ 0.2PPb, and metal impurities ≤ 5PPb.

[0061] The heavy impurity component material in the high boiling tank 13 enters the high boiling cracking system 32 of the cold hydrogenation unit 3, and the high boiling cracking system 32 is extracted and enters the flash evaporator 11 for re-purification.

[0062] The high-low boiling system 42 of the distillation unit 4 is extracted and enters the light and heavy impurities tank 44, wherein the main component of the material is: 99.8% TCS, the impurity content is: B≤18PPb, P≤1.7PPb, and the metal impurities are ≤168PPb. Considering that the content of impurities in the light and heavy impurities tank 44 is relatively low, the extraction of the light and heavy impurities tank 44 is directly sent to the partition wall packing tower 2 for purification treatment. The actual processing capacity of this pipeline material is about 24t / h. Therefore, after directly entering the partition wall packing tower 2, the processing capacity of the slurry treatment unit 1 is reduced, and the operation load of the slurry treatment unit 1 is reduced.

[0063] The filter cleaning replacement liquid at each point of the distillation unit 4, the residual hydraulic material discharged by pipeline replacement, etc. enter the mixing tank 43 of the distillation unit 4 for mixing. The material components in the mixing tank 43 mainly include: 72% TCS, 6% STC, 2% DCS, and the impurity content is: B≤112PPb, P≤26PPb, and metal impurities≤340PPb. The extraction of the mixing tank 43 is pumped to the flash evaporator 11 for flash evaporation, which further reduces the amount of impurities introduced.

[0064] The impurity removal process for polysilicon production of the present application collects the materials containing high impurities from the trichlorosilane synthesis unit 5, the three waste units 6, the high boiling cracking system 32, and the mixing tank 43 of the distillation unit 4 into the slurry treatment unit 1 for treatment, and finally passes through the high boiling tank 13 for purification and cracking and is discharged. The materials are extracted from the side of the partition wall packing tower 2 to obtain high-quality silane materials that enter the cold hydrogenation unit 3 and the distillation unit 4, and the high-impurity silane materials are repeatedly circulated between the slurry treatment unit 1 and the partition wall packing tower 2, and high-quality silane materials are only obtained from the side, which effectively controls the recovery rate of the materials and the amount of impurities introduced.

[0065] Through the impurity removal process for polysilicon production of the present application, the impurity content in the refined material finally obtained after the distillation unit 4 is controlled within the range of B≤0.01PPb, P≤0.01PPb, metal impurities≤1PPb and carbon impurities≤0.5PPm, which can effectively improve the quality of polysilicon rods.

[0066] The above describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and the specification only describe the principles of the present application. The present application may have various changes and improvements without departing from the spirit and scope of the present application, and these changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the attached claims and their equivalents.

Claims

1. A doping system for polysilicon production, characterized in that: It includes a slurry treatment unit, a packed tower and a cold hydrogenation unit, wherein the discharge port of the slurry treatment unit is connected to the packed tower, and the packed tower is at least equipped with a top discharge port, a side line outlet and a bottom discharge port, the side line outlet is connected to the cold hydrogenation unit, and the top discharge port and the bottom discharge port are connected to the slurry treatment unit.

2. The impurity removal system for polysilicon production according to claim 1, characterized in that: The slurry treatment unit includes a flash evaporator, a distillation tower and a high boiling tank. The discharge port of the flash evaporator is connected to the distillation tower, the light component discharge port of the distillation tower is connected to the packed tower, the tower top discharge port is connected to the flash evaporator, and the tower bottom discharge port is connected to the high boiling tank.

3. The impurity removal system for polysilicon production according to claim 1, characterized in that: The packed tower is a partition wall packed tower, and the packing is a metal wire mesh.

4. The impurity removal system for polysilicon production according to claim 2, characterized in that: The cold hydrogenation unit comprises a cold hydrogenation coarse fraction tower, the side line outlet is connected to the cold hydrogenation coarse fraction tower, and the discharge port of the cold hydrogenation coarse fraction tower is connected to the distillation unit.

5. The impurity removal system for polysilicon production according to claim 4, characterized in that: The distillation unit comprises a primary crude distillation tower and a high-low boiling system. The discharge port of the cold hydrogenation crude fraction tower is connected to the primary crude distillation tower, and the discharge port of the high-low boiling system is connected to the packed tower.

6. The impurity removal system for polysilicon production according to claim 5, characterized in that: The cold hydrogenation unit further comprises a high boiling cracking system, the discharge port of the high boiling cracking system is connected to the flash evaporator, and the light component discharge port of the high boiling tank is connected to the high boiling cracking system.

7. The impurity removal system for polysilicon production according to claim 6, characterized in that: The impurity removal system also includes a trichlorosilane synthesis unit and a three-waste unit. The heavy fraction discharge port of the trichlorosilane synthesis unit is connected to the slurry treatment unit, and the heavy fraction discharge port of the three-waste unit is connected to the slurry treatment unit.

8. The impurity removal system for polysilicon production according to claim 7, characterized in that: The distillation unit further comprises a mixing tank and a light and heavy miscellaneous tank, the discharge port of the mixing tank is connected to the flash evaporator, the discharge port of the high and low boiling system is connected to the light and heavy miscellaneous tank, and the discharge port of the light and heavy miscellaneous tank is connected to the packed tower.

9. A process for removing impurities in polysilicon production, characterized in that: The heavy components in the trichlorosilane synthesis unit and the three waste units enter the slurry treatment unit, and the heavy components are initially purified in the slurry treatment unit to obtain a distillation clear liquid, and the distillation clear liquid enters a packed tower for further purification. The packed tower is configured to have at least a tower top discharge port, a side line discharge port and a tower bottom discharge port. The crude trichlorosilane produced by the side line discharge port enters a cold hydrogenation unit and a distillation unit for further purification, the light components produced by the tower top discharge port are refluxed to the slurry treatment unit for re-purification, and the heavy components produced by the tower bottom discharge port are refluxed to the slurry treatment unit for re-purification.

10. The impurity removal process for polysilicon production according to claim 9, characterized in that: The slurry treatment unit is configured to have a flash evaporator, a distillation tower and a high boiling tank. The heavy components in the trichlorosilane synthesis unit and the three waste units enter the flash evaporator and the distillation tower in sequence, and a distillate is obtained after purification. The distillate enters the packed tower, and the light components extracted from the tower top outlet are refluxed to the flash evaporator for re-purification, and the heavy components extracted from the tower bottom outlet are refluxed to the high boiling tank for purification and separation. The cold hydrogenation unit is configured to have a cold hydrogenation crude fractionation tower and a high-boiling cracking system. The crude trichlorosilane produced from the side line outlet enters the cold hydrogenation crude fractionation tower and the distillation unit for further purification, the heavy impurities produced from the high-boiling tank enter the high-boiling cracking system for decomposition, and the product produced from the high-boiling cracking system re-enters the flash evaporator for purification.

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