A method and apparatus for recycling heavy materials from a fresh material system

Abstract

This invention discloses a method and apparatus for recovering heavy impurities from a fresh feed system, relating to the technical field of polysilicon production equipment. The main technical solution of this invention is as follows: A method for recovering heavy impurities from a fresh feed system involves feeding a mixture of oxysilanes and chlorosilanes, along with heavy impurities generated from the fresh feed system, into a distillation column. Liquid-phase oxysilanes and gaseous heavy impurities form a countercurrent flow and undergo mass and heat transfer, separating heavy oxysilanes and light chlorosilanes. The heavy oxysilanes enter the column bottom, while the light chlorosilanes are cooled and recovered. This method not only recovers chlorosilanes mixed in with high-boiling-point cracked oxysilanes but also utilizes oxysilanes to remove complexes from the heavy impurities, thereby achieving the recovery of chlorosilanes and thus saving energy and improving raw material utilization. This invention is mainly used for separating chlorosilanes.

Description

Technical Field

[0001] This invention relates to the field of polysilicon production equipment technology, and in particular to a method and apparatus for recovering heavy impurities from a fresh material system. Background Technology

[0002] In the process of producing polycrystalline silicon using the Siemens process, oxysilane is produced as a byproduct. Oxysilane and silane have similar boiling points. During the high-boiling cleavage of silane, oxysilane mixed in cannot be cleaved and will gradually accumulate. Once it reaches a certain level, it will affect the high-boiling cleavage reaction. Regularly eliminating oxysilane is a necessary condition to meet the requirements of the high-boiling cleavage reaction.

[0003] In the process of producing polysilicon, the separation and purification of trichlorosilane is a critical step that directly determines the quality grade of the produced polysilicon. Currently, distillation is used to separate and purify trichlorosilane in the production process. Some processes add adsorption and impurity removal devices to further remove some light components and trace impurities that are difficult to remove by distillation, and directly hydrolyze concentrated heavy impurities.

[0004] In existing technologies, the main method for treating mixtures of oxysilanes and chlorosilanes, as well as concentrated heavy impurities, is periodic hydrolysis. Periodic hydrolysis can effectively treat mixtures of oxysilanes and chlorosilanes, as well as complexes in concentrated heavy impurities. However, this method leads to yield loss. At the same time, hydrolysis also wastes water resources. Taking a polysilicon production capacity of 45,000 tons per year as an example, the fresh feed system generates 1.2 tons of heavy impurities per hour, which are directly hydrolyzed, resulting in yield loss. Hydrolyzing 300 kg of oxysilanes per hour will bring out 300 kg of chlorosilanes along with the oxysilanes to participate in the reaction, causing yield loss and thus increasing the production cost and energy consumption of polysilicon. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a method and apparatus for recovering heavy impurities in a fresh feed system. The main objective is to provide a method for recovering heavy impurities in a fresh feed system that can recover and utilize mixtures of oxysilanes and chlorosilanes as well as complexes in concentrated heavy impurities.

[0006] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0007] On one hand, embodiments of the present invention provide a method for recycling reprocessing of fresh materials in a system, the method comprising:

[0008] A mixture of oxysilanes and chlorosilanes, along with heavy impurities generated from the fresh feed system, is fed into the distillation column;

[0009] Liquid-phase oxysilanes and gas-phase heavy hybrids form countercurrents and transfer mass and heat to each other, separating the heavy component oxysilanes and the light component chlorosilanes.

[0010] The recombined oxygen-silane enters the bottom of the column;

[0011] The light component, chlorosilane, is extracted and recovered after cooling.

[0012] Furthermore, the mixture of oxysilane and chlorosilane is fed into the top feed inlet of the distillation column;

[0013] The heavy impurities generated in the fresh feed system are concentrated and then fed into the lower feed inlet of the distillation column;

[0014] The heavy impurities are heated in a reboiler to form gaseous heavy impurities, which then rise.

[0015] Furthermore, some of the light chlorosilane components enter the fresh feed system, while some of the light chlorosilane components are refluxed to the top of the distillation column.

[0016] Furthermore, a portion of the recombinant oxysilane is introduced into the pipeline containing the mixture of oxysilane and chlorosilane.

[0017] On the other hand, embodiments of the present invention also provide an apparatus for recycling heavy impurities in a fresh material system, the apparatus comprising:

[0018] A distillation unit, comprising a distillation column, a mixture line, and a heavy / unnecessary line, wherein the mixture line is connected to the upper feed inlet of the distillation column, and the heavy / unnecessary line is connected to the lower feed inlet of the distillation column;

[0019] A heating element, which is connected to the bottom of the distillation column;

[0020] A cooling component, the cooling component being connected to the top of the distillation column;

[0021] A collection component is attached to the bottom of the distillation column.

[0022] Furthermore, the cooling component includes a cooler, a reflux tank, and an output pipe. One end of the cooler is connected to the top of the distillation column, and the other end is connected to the reflux tank. The output pipe is connected to the reflux tank.

[0023] Furthermore, the reflux component includes a reflux pump and a reflux pipeline. One end of the reflux pump is connected to the reflux tank, and the other end is connected to the reflux pipeline. The reflux pipeline is connected to the top of the distillation column, and the output pipeline is connected to the middle of the reflux pipeline.

[0024] Furthermore, the extraction component includes a bottom pump and an extraction pipeline, with one end of the bottom pump connected to the bottom of the distillation column and the other end connected to the extraction pipeline.

[0025] Furthermore, the extraction component also includes a connecting pipe, one end of which is connected to the middle of the extraction pipe, and the other end is connected to the mixture pipeline.

[0026] Furthermore, on / off valves are respectively installed on the mixture pipeline, the heavy mixture pipeline, and the connecting pipeline.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] In the technical solution provided by the embodiments of the present invention, a mixture of oxysilane and chlorosilane, along with heavy impurities generated from the fresh feed system, is fed into a distillation column. The liquid-phase oxysilane and the gaseous heavy impurities form a countercurrent flow and transfer mass and heat to each other, separating the heavy oxysilane and the light chlorosilane. The heavy oxysilane enters the bottom of the column, while the light chlorosilane is cooled and collected for recovery. This method not only recovers the chlorosilane mixed in the high-boiling-point cracking residual oxysilane but also removes complexes from the heavy impurities using oxysilane, thereby achieving the recovery of chlorosilane and thus achieving the technical effects of saving energy and improving the utilization rate of raw materials. Attached Figure Description

[0029] Figure 1 A flowchart of a method for recycling heavy impurities in a fresh material system provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of a device for recycling heavy impurities in a fresh material recycling system, provided as an embodiment of the present invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0032] Before describing the specific embodiments, it is necessary to explain some of the terms used in this specification, as follows:

[0033] Heavy impurities mainly refer to impurities that are difficult to remove by distillation from the fresh feed system. In this technical solution, they mainly refer to a mixture of chlorosilanes and complexes containing boron and phosphorus, wherein the boron and phosphorus complexes are aggregated in the chlorosilanes.

[0034] The mixture of oxysilanes and chlorosilanes mainly refers to the mixture of oxysilanes and chlorosilanes produced during the high-boiling cracking of silanes, where chlorosilanes refer to the mixture of trichlorosilane and silicon tetrachloride.

[0035] On one hand, embodiments of the present invention provide a method for recycling reprocessing of fresh materials in a system, the method comprising:

[0036] A mixture of oxysilanes and chlorosilanes, along with heavy impurities generated from the fresh feed system, is fed into the distillation column;

[0037] Liquid-phase oxysilanes and gas-phase heavy hybrids form countercurrents and transfer mass and heat to each other, separating the heavy component oxysilanes and the light component chlorosilanes.

[0038] The recombined oxygen-silane enters the bottom of the column;

[0039] The light component, chlorosilane, is extracted and recovered after cooling.

[0040] In the technical solution provided by the embodiments of the present invention, a mixture of oxysilane and chlorosilane, along with heavy impurities generated from the fresh feed system, is fed into a distillation column. The liquid-phase oxysilane and the gaseous heavy impurities form a countercurrent flow and transfer mass and heat to each other, separating the heavy oxysilane and the light chlorosilane. The heavy oxysilane enters the bottom of the column, while the light chlorosilane is cooled and collected for recovery. This method not only recovers the chlorosilane mixed in the high-boiling-point cracking residual oxysilane but also removes complexes from the heavy impurities using oxysilane, thereby achieving the recovery of chlorosilane and thus achieving the technical effects of saving energy and improving the utilization rate of raw materials.

[0041] Example 1

[0042] Specifically, such as Figure 1 and Figure 2 As shown, this technical solution discloses a method for recycling heavy impurities in a fresh material system, which includes the following steps:

[0043] 101. Pass the mixture of oxysilane and chlorosilane into the top feed port of the distillation column.

[0044] In the Siemens process for producing polysilicon, oxysilanes are produced as a byproduct. Because oxysilanes and chlorosilanes have similar boiling points, oxysilanes cannot be decomposed during the high-boiling silane cracking process, leading to their accumulation in chlorosilanes. When the amount of oxysilanes reaches a certain level, it will affect the high-boiling silane cracking reaction. Therefore, it is necessary to periodically remove the oxysilanes by introducing a mixture of oxysilanes and chlorosilanes into the upper feed port of the distillation column, so that the mixture of oxysilanes and chlorosilanes is located in the upper part of the heavy impurities.

[0045] 102. Concentrate the heavy impurities generated in the fresh feed system and then introduce them into the lower feed inlet of the distillation column.

[0046] The fresh feed system mainly processes fresh feed, which generates heavy impurities during the process. These heavy impurities mainly include boron and phosphorus complexes. After the heavy impurities are concentrated, they are fed into the feed inlet of the distillation column, so that the heavy impurities are located at the bottom of the mixture of oxysilanes and chlorosilanes.

[0047] 103. Heavy impurities are heated in a reboiler to form gaseous heavy impurities and rise.

[0048] The heavy impurities are heated in a reboiler, causing them to rise in the gaseous phase and enter the mixture of oxysilanes and chlorosilanes.

[0049] 104. Liquid-phase oxysilanes and gas-phase heavy hybrids form countercurrents and transfer mass and heat to each other, separating the heavy component oxysilanes and the light component chlorosilanes.

[0050] After heating, the gaseous heavy impurities and the liquid mixture of oxysilanes and chlorosilanes undergo mass and heat transfer with each other. The heavy oxysilane component is discharged from the bottom of the distillation column, while the light chlorosilane component is discharged from the top of the distillation column.

[0051] 105. The heavy component oxysilane enters the bottom of the column.

[0052] Some of the heavy oxysilane fractions are discharged from the bottom of the distillation column and then enter the bottom of the column for subsequent processes.

[0053] 106. Pass a portion of the heavy component oxysilane into the pipeline containing the mixture of oxysilane and chlorosilane.

[0054] A portion of the heavy silane fraction is introduced into the mixture pipeline of silane and chlorosilane. This is because silane, as a byproduct of the formation process, has a low yield and may experience flow interruptions during equipment operation. This could lead to the heavy impurities entering the distillation column without contacting the silane and being discharged directly from the top of the distillation column, thus directly entering the fresh feed system and affecting product quality. Therefore, a portion of the silane is introduced into the mixture pipeline of silane and chlorosilane to ensure that sufficient silane enters the distillation column from the top feed inlet and fully contacts and reacts with the vaporized heavy impurities.

[0055] 107. Some of the light component chlorosilanes enter the fresh feed system, and some of the light component chlorosilanes are refluxed to the top of the distillation column.

[0056] Some of the light chlorosilane components are fed into the fresh feed system for subsequent processes, while others are refluxed back into the distillation column to maintain the heat balance within the column and to increase the precision of product separation.

[0057] Taking a 45,000-ton-per-year polysilicon plant as an example, the fresh feed system generates approximately 1.2 tons of heavy impurities per hour, and the byproduct oxysilane is approximately 300 kg / h. After mass and heat transfer between the two in the distillation column, the impurity content at the top of the column is much lower than that in the fresh feed system. The impurity content of boron at the inlet is approximately 0.05 ug / ml, and the impurity content of boron at the top of the column is approximately 0.001 ug / ml; the impurity content of phosphorus at the inlet is approximately 0.01 ug / ml, and the impurity content of phosphorus at the top of the column is approximately 0.002 ug / ml. This embodiment of the invention provides... In this technical solution, a mixture of oxysilanes and chlorosilanes, along with heavy impurities generated from the fresh feed system, is fed into a distillation column. The liquid-phase oxysilanes and the gaseous heavy impurities flow countercurrently and transfer mass and heat to each other, separating the heavy oxysilanes and the light chlorosilanes. The heavy oxysilanes are fed into the bottom of the column, while the light chlorosilanes are cooled and recovered. This method not only recovers the chlorosilanes mixed in with the high-boiling-point cracking residual oxysilanes but also removes complexes from the heavy impurities using oxysilanes, thereby achieving the recovery of chlorosilanes and ultimately saving energy and improving the utilization rate of raw materials.

[0058] On the other hand, such as Figure 2 As shown, this embodiment of the invention also provides an apparatus for recycling heavy impurities in a fresh material system, the apparatus comprising:

[0059] The distillation unit includes a distillation column 11, a mixture line 12, and a heavy and mixed line 13. The mixture line 12 is connected to the upper feed port of the distillation column 11, and the heavy and mixed line 13 is connected to the lower feed port of the distillation column 11.

[0060] A heating element is connected to the bottom of the distillation column 11;

[0061] A cooling component is connected to the top of the distillation column 11;

[0062] A collection component is attached to the bottom of the distillation column 11.

[0063] In this technical solution, the function of the distillation unit is to separate different components. The distillation unit includes a distillation column 11, a mixture pipeline 12, and a heavy impurity pipeline 13. The mixture pipeline 12 is connected to the upper feed inlet of the distillation column 11, and the heavy impurity pipeline 13 is connected to the lower feed inlet of the distillation column 11. The on / off valve 6 is installed on the mixture pipeline 12 and the heavy impurity pipeline 13. The function of the heating unit is to vaporize the heavy impurities, and the heating unit is connected to the bottom of the distillation column 11. The function of the cooling unit is to cool the discharged chlorosilane, and the cooling unit is connected to the top of the distillation column 11. The function of the collection unit is to divert the discharged oxysilane, and the collection unit is connected to the bottom of the distillation column 11. Compared with the prior art, this solution is more effective for mixing and concentrating oxysilanes and chlorosilanes. The main method for treating complexes in heavy impurities is periodic hydrolysis. Periodic hydrolysis can effectively treat mixtures of oxysilanes and chlorosilanes, as well as complexes in concentrated heavy impurities. However, this method leads to yield loss, and hydrolysis also wastes water resources. In this technical solution, the mixture of oxysilanes and chlorosilanes, along with heavy impurities generated from the fresh feed system, is fed into distillation column 11. The liquid-phase oxysilanes and gaseous heavy impurities form a countercurrent flow and transfer mass and heat to each other, separating heavy oxysilanes and light chlorosilanes. The heavy oxysilanes enter the bottom of the column, while the light chlorosilanes are cooled and recovered. This method not only recovers chlorosilanes mixed in with the high-boiling-point cracked oxysilanes but also removes complexes from heavy impurities using oxysilanes, thereby achieving the recovery of chlorosilanes and thus saving energy and improving raw material utilization.

[0064] Furthermore, the cooling components include a cooler 31, a reflux tank 32, and an output pipe 33. One end of the cooler 31 is connected to the top of the distillation column 11, and the other end is connected to the reflux tank 32. The output pipe 33 is connected to the reflux tank 32. In this embodiment, a cooling component is further defined. One end of the cooler 31 is connected to the top of the distillation column 11, and the other end is connected to the reflux tank 32. The chlorosilane is discharged from the top of the distillation column 11 and enters the cooler 31 for cooling, and then enters the reflux tank 32, thereby achieving the technical effect of reducing the temperature of the chlorosilane. Optionally, a reflux component is added, which includes a reflux pump 51 and a reflux pipe 52. One end of the reflux pump 51 is connected to the reflux tank 32, and the other end is connected to the reflux pipe 52. The reflux pipe 52 is connected to the top of the distillation column 11, and the output pipe 33 is connected to the middle of the reflux pipe 52. Under the action of the reflux pump 51, part of the chlorosilane returns to the distillation column 11 through the reflux pipe 52 to maintain the heat balance in the distillation column 11. At the same time, it can also increase the accuracy of product separation. The remaining part of the chlorosilane enters the fresh feed system, thereby achieving the technical effects of maintaining the heat balance of the distillation column 11 and increasing the accuracy of product separation.

[0065] Furthermore, the extraction component includes a bottom liquid pump 41 and an extraction pipeline 42. One end of the bottom liquid pump 41 is connected to the bottom of the distillation column 11, and the other end is connected to the extraction pipeline 42. In this embodiment, the extraction component is further defined. The bottom liquid pump 41 provides power to transport oxysilane to the bottom of the column through the extraction pipeline 42, thereby achieving the effect of quickly discharging oxysilane. Optionally, the extraction component also includes a connecting pipeline 43. One end of the connecting pipeline 43 is connected to the middle of the extraction pipeline 42, and the other end is connected to the mixture pipeline 12. The on / off valve 6 is installed on the connecting pipeline 43. Since oxysilane is a by-product of the formation and has a low yield, there may be a flow interruption during equipment operation. This may lead to the risk that the heavy impurities entering the distillation column 11 will not come into contact with the oxysilane and will be discharged directly from the top of the distillation column 11, thus directly entering the fresh feed system, thereby affecting the quality of the product. Therefore, some oxysilane is introduced into the mixture pipeline 12 of oxysilane and chlorosilane to ensure that enough oxysilane enters the distillation column 11 from the top feed port and fully contacts and reacts after the heavy impurities are vaporized, thereby achieving the technical effect of reducing the risk.

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for recycling heavy materials from a fresh material system, characterized in that, Includes the following steps: A mixture of oxysilane and chlorosilane is fed into the top inlet of the distillation column; The heavy impurities generated in the fresh feed system are concentrated and then fed into the lower feed inlet of the distillation column; The heavy impurities are heated in a reboiler to form gaseous heavy impurities, which then rise. Liquid-phase oxysilane and gas-phase heavy atom form a countercurrent and transfer mass and heat to each other, separating heavy component oxysilane and light component chlorosilane. The heavy atom recovers the chlorosilane mixed in the high-boiling cracking residual oxysilane, while the oxysilane removes the complexes in the heavy atom. The recombinant oxysilane enters the bottom of the column, and a portion of the recombinant oxysilane is passed into the pipeline containing the mixture of oxysilane and chlorosilane. The light component, chlorosilane, is collected and recovered after cooling. Here, heavy heterogeneous refers to a mixture of chlorosilanes and complexes containing boron and phosphorus, with the boron and phosphorus complexes aggregated in the chlorosilanes.

2. The method according to claim 1, characterized in that, The recovery of the light component chlorosilane after cooling includes: Some of the light chlorosilane components enter the fresh feed system, while some are refluxed to the top of the distillation column.

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