Polycrystalline silicon production waste gas recovery system

Abstract

The utility model provides a polycrystalline silicon production waste gas recovery system, and aims to solve the technical problems that the existing recovery system is low in silane gas recovery efficiency, high in equipment investment and operation cost and high in cooling capacity consumption. The system comprises a tail gas recovery unit used for collecting tail gas generated in the polycrystalline silicon production process; the inlet end of the first condensation unit is communicated with the output end of the tail gas recovery unit; the input end of the compression unit is communicated with the output end of the first condensation unit; the input end of the second condensation unit is communicated with the output end of the compression unit; the input end of the cold hydrogenation unit is communicated with the output end of the second condensation unit. The recycling requirement can be met through the condensation units in front of and behind the compression unit, more silane condensate can be recycled more effectively, the silane consumption of the system is reduced, the use amount of a cooling medium can be saved, the load of a refrigerating unit can be reduced, and meanwhile, the operating cost of the unit and the equipment investment can be saved.

Description

Technical Field

[0001] This utility model relates to the field of polysilicon production technology, and in particular to a polysilicon production waste gas recovery system. Background Technology

[0002] Polycrystalline silicon is a form of elemental silicon, primarily produced by chlorinating dry hydrogen chloride gas and dry silicon powder under specific conditions, followed by condensation, distillation, and reduction. Depending on the application, polycrystalline silicon can be broadly categorized into electronic-grade polycrystalline silicon, solar-grade polycrystalline silicon, and metallurgical-grade polycrystalline silicon. Currently, polycrystalline silicon production processes are maturing, mainly employing methods such as the modified Siemens process, fluidized bed process, gas-liquid deposition process, and silane process.

[0003] Currently, polysilicon production, besides recovering hydrogen from the tail gas system, also requires recovering the desorption gas from the adsorption column and some recyclable tail gas recovered from other devices. In existing technologies, such as... Figure 1 As shown, most waste gas recovery processes involve condensing the recovered gas through three stages before it enters the compressor and is then sent to cold hydrogenation for use. The following are the shortcomings of this waste gas recovery and treatment system: 1. High cooling consumption and a large amount of electricity is required during the production process, especially in the reduction and other stages, where electricity costs account for a large proportion and energy consumption is high; 2. The equipment for producing polysilicon is expensive, with a large initial investment and high subsequent maintenance costs, and the silane gas recovery efficiency is low. Summary of the Invention

[0004] In view of the above situation and to overcome the defects of the prior art, the purpose of this utility model is to provide a polysilicon production waste gas recovery system, which solves the technical problems of low silane gas recovery efficiency, high equipment investment and operating costs, and high cooling consumption in the existing recovery system.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A polysilicon production waste gas recovery system includes: a tail gas recovery unit for collecting tail gas generated during polysilicon production; a first condensation unit with its inlet end connected to the output end of the tail gas recovery unit; a compression unit with its input end connected to the output end of the first condensation unit; a second condensation unit with its input end connected to the output end of the compression unit; and a cold hydrogenation unit with its input end connected to the output end of the second condensation unit.

[0007] The exhaust gas recovered by this invention undergoes preliminary condensation and separation before the compression unit. Then, the compression unit pressurizes the gas after preliminary condensation and condenses it again, effectively improving the condensation effect. At this time, most of the silane gas can be condensed into silane liquid. The condensation after the pressure increase is not only conducive to the collection of silane condensate, but also saves the system's cooling capacity. Compared with the existing three-stage condensation, this system can achieve the reuse requirements through the first and second condensation units before and after the compression unit. It can not only recover more and more silane condensate and reduce the system's silane consumption, but also save the amount of cooling medium used, reduce the load on the refrigeration unit, and save on unit operating costs and equipment investment.

[0008] Optionally, the polysilicon production waste gas recovery system further includes a silane condensate collection unit, wherein the output ends of the first condensation unit and the second condensation unit are both connected to the silane condensate collection unit.

[0009] Optionally, the first condensation unit is connected to the silane condensate collection unit via a first pipeline, and the second condensation unit is connected to the silane condensate collection unit via a second pipeline.

[0010] Optionally, both the first condensing unit and the second condensing unit are equipped with a water inlet pipe and a water outlet pipe.

[0011] Optionally, the first condensation unit cools the silane gas in the exhaust gas to below -25°C under a cooling condition of -40°C before feeding it into the compression unit.

[0012] Optionally, both the first condensing unit and the second condensing unit are condensers, each condenser including a cooling medium pipeline and a heat exchange chamber, the cooling medium being Freon, and the cooling temperature being -40℃.

[0013] Optionally, the compression unit includes a compressor and a pressure regulating device. The compressor is used to pressurize the condensed gas to 0.65 MPa, and the pressure regulating device is used to control the output pressure of the compression unit.

[0014] Optionally, a gas purification device is provided between the first condensation unit and the second condensation unit.

[0015] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0016] This invention recovers exhaust gas by condensing silane to below -25 degrees Celsius using a -40 degree Celsius refrigerant stage before the compressor. The condensed silane liquid is then collected by a silane collection unit for further purification and reuse. Condensing the silane gas eliminates the risk of compressor damage caused by silane liquid (the compressor intake air does not contain silane liquid). Then, a second -40 degree Celsius condensation stage after the compressor further enhances the condensation effect, allowing most of the silane gas to be condensed into silane liquid. The pressure before the compressor is approximately 50-100 kPa, and the pressure after the compressor is 0.65 MPa. This increased pressure facilitates silane liquid collection and saves system cooling capacity. Compared to existing three-stage condensation systems, this system achieves reuse requirements through a single stage of condensation before and after the compressor. This not only recovers more silane liquid more effectively, reducing system silane consumption, but also saves on refrigerant usage, reducing the load on the refrigeration unit, and saving on unit operating costs and equipment investment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments 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.

[0018] Figure 1 This is a schematic diagram of the existing technology.

[0019] Figure 2 This is a schematic diagram of the structure of this utility model.

[0020] Reference numerals in the attached drawings: 1. Exhaust gas recovery unit; 2. First condensation unit; 3. Compression unit; 4. Second condensation unit; 5. Cold hydrogenation unit; 6. Silane condensate collection unit; 7. First pipeline; 8. Second pipeline; 9. Water inlet pipe; 10. Water outlet pipe. Detailed Implementation

[0021] 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 embodiments of this utility model application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0022] In the description of the embodiments of this utility model application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", "end", "side" etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, are only for the convenience of describing the embodiments of this utility model application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this utility model application.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this utility model application, "multiple" means two or more, unless otherwise explicitly specified.

[0024] In the embodiments of this utility model application, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this utility model application according to the specific circumstances.

[0025] In the embodiments of this utility model application, unless otherwise explicitly 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 being 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 being 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.

[0026] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of this utility model application. To simplify the disclosure of the embodiments of this utility model application, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of this utility model application. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of this utility model application; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0027] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0028] Currently, polysilicon production, in addition to recovering hydrogen from the exhaust gas system, also requires recovering the desorption gas from the adsorption column and some recyclable exhaust gases recovered from other devices. (Refer to...) Figure 1 As shown, most existing waste gas recovery processes involve condensing the recovered gas through three stages before it enters a compressor and is then sent to cold hydrogenation for reuse. This waste gas recovery system has the following shortcomings: 1. High cooling consumption, and the production process requires a large amount of electricity, especially in reduction and other stages, where electricity costs account for a significant portion of the overall cost, resulting in high energy consumption; 2. The equipment for producing polysilicon is expensive, requiring a large initial investment and incurring high maintenance costs, and the silane gas recovery efficiency is low.

[0029] like Figure 2 As shown in the figure, this utility model application provides a polysilicon production waste gas recovery system to solve the above-mentioned problems. The polysilicon production waste gas recovery system includes a tail gas recovery unit 1, a first condensation unit 2, a compression unit 3, a second condensation unit 4, and a cold hydrogenation unit 5 connected in sequence.

[0030] The exhaust gas recovery unit 1 is used to collect the exhaust gas generated during the polysilicon production process. Its output end is connected to the input end of the first condensation unit 2. After receiving the exhaust gas, the first condensation unit 2 performs preliminary condensation and separation on the exhaust gas. Its output end is connected to the input end of the compression unit 3. The compression unit 3 is used to pressurize the condensed gas. Its output end is connected to the input end of the second condensation unit 4. The second condensation unit 4 is used to further condense and separate the gas pressurized by the compression unit 3. Its output end is connected to the inlet end of the cold hydrogenation unit 5. After the cold hydrogenation unit 5 processes the exhaust gas, its output end is connected to the polysilicon production system.

[0031] This system first performs preliminary condensation (condensing to below -25 degrees Celsius) before compression unit 3. By condensing the silane gas, damage to compression unit 3 caused by the presence of liquid silane is prevented (compression unit 3's intake air does not contain liquid silane). Then, a second condensation at -40 degrees Celsius is performed after compression unit 3 to improve the condensation effect, at which point most of the silane gas can be condensed into liquid silane. During operation, the pressure before compression unit 3 is approximately 50-100 kPa, and the pressure after compression unit 3 is 0.65 MPa. The increased pressure during condensation not only facilitates the collection of silane condensate but also saves system cooling capacity.

[0032] Furthermore, the polysilicon production waste gas recovery system also includes a silane condensate collection unit 6. The output ends of both the first condensation unit 2 and the second condensation unit 4 are connected to the silane condensate collection unit 6. The silane condensate collection unit 6 is used to collect condensed silane liquid for further purification and reuse. Specifically, the output end of the first condensation unit 2 is connected to the silane condensate collection unit 6 through a first pipe 7, and the output end of the second condensation unit 4 is connected to the silane condensate collection unit 6 through a second pipe 8.

[0033] Optionally, both the first condensing unit 2 and the second condensing unit 4 are provided with a water inlet pipe 9 and a water outlet pipe 10. The water inlet pipe 9 is used to introduce cooling medium into the condensing unit, and the water outlet pipe 10 is used to discharge the cooling medium.

[0034] Optionally, the first condensation unit 2 cools the silane gas in the exhaust gas to below -25°C under a cooling condition of -40°C before feeding it into the compression unit 3.

[0035] Optionally, both the first condensing unit 2 and the second condensing unit 4 employ exhaust gas condensers. The condenser includes a cooling medium pipeline and a heat exchange chamber. The cooling medium pipeline is connected to the heat exchange chamber to facilitate heat exchange between the exhaust gas and the cooling medium. In use, Freon can be introduced into the cooling medium pipeline as the cooling medium; the Freon's temperature is -40℃.

[0036] Optionally, the cooling medium input temperature of the first condensing unit 2 is 7°C and the output temperature is 7°C. Preliminary condensation through the first condensing unit 2 helps to reduce the overall energy consumption of the system.

[0037] Optionally, the cooling medium input temperature of the second condensation unit 4 is -40℃, and the output temperature is -40℃. By performing deep condensation of the compressed gas through the second condensation unit 4, silane and silicon tetrachloride in the exhaust gas can be recovered to the maximum extent, reducing resource waste.

[0038] Optionally, the compression unit 3 includes a compressor and a pressure regulating device, which is used to control the output pressure of the compression unit. In use, the compressor is used to pressurize the condensed gas to 0.65 MPa. The increased pressure facilitates the collection of silane condensate and also saves system cooling capacity.

[0039] Optionally, the output of the cold hydrogenation unit 5 is connected to a product separation device.

[0040] Optionally, a gas purification device is provided between the first condensation unit 2 and the second condensation unit 4 to remove impurities in the exhaust gas, which is beneficial to improving the efficiency of the cold hydrogenation reaction.

[0041] In operation, the recovered exhaust gas first enters the first condensation unit 2 (before the compressor) for a first-stage -40°C Freon condensation of the silane to below -25°C. The silane liquid is then collected by the silane condensate collection unit 6 for further purification and reuse. Condensing the silane gas eliminates the risk of compressor damage caused by silane liquid (the compressor intake does not carry silane liquid). Then, after the compressor (first condensation unit 2), it undergoes another -40°C condensation to improve the condensation efficiency, at which point most of the silane gas is condensed into silane liquid. During system operation, the pressure before the compressor is approximately 50-100 kPa, and the pressure after the compressor is 0.65 MPa. The increased pressure facilitates silane condensate collection and saves system cooling capacity. This transforms the previous three-stage condensation into a single-stage condensation before and after the compressor, achieving the reuse requirement. This not only allows for more efficient recovery of silane condensate and reduces system silane consumption, but also saves on refrigerant usage, reducing the refrigeration unit load. Furthermore, it saves on unit operating costs and equipment investment.

[0042] Any aspects not described in detail in this embodiment are techniques known in the art.

[0043] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this utility model, and these should all be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A polysilicon production waste gas recovery system, characterized in that, The application relates to a polysilicon production exhaust gas recovery system. The polysilicon production exhaust gas recovery system comprises a tail gas recovery unit for collecting tail gas generated in a polysilicon production process; a first condensing unit, an input end of which is connected with an output end of the tail gas recovery unit; a compression unit, an input end of which is connected with an output end of the first condensing unit; a second condensing unit, an input end of which is connected with an output end of the compression unit; and a cold hydrogenation unit, an input end of which is connected with an output end of the second condensing unit. The polysilicon production exhaust gas recovery system further comprises a silane condensate collecting unit, and the output ends of the first condensing unit and the second condensing unit are connected with the silane condensate collecting unit. The first condensing unit is connected with the silane condensate collecting unit through a first pipeline, and the second condensing unit is connected with the silane condensate collecting unit through a second pipeline. The first condensing unit and the second condensing unit are both provided with water inlet pipes and water outlet pipes. The first condensing unit is used for cooling silane gas in the tail gas to below -25 DEG C under the cooling condition of -40 DEG C and then inputting the silane gas into the compression unit.

2. The polysilicon production waste gas recovery system according to claim 1, characterized by, The first condensing unit and the second condensing unit are both condensers, and the condensers comprise cooling medium pipelines and heat exchange cavities.

3. The polysilicon production waste gas recovery system according to claim 2, wherein The compression unit comprises a compressor and a pressure adjusting device.

4. The polysilicon production waste gas recovery system according to claim 1, wherein The first condensing unit and the second condensing unit are provided with a gas purifying device.

5. The polysilicon production waste gas recovery system according to any one of claims 1 to 4, characterized by, The first condensing unit and the second condensing unit are provided with a gas purifying device.

6. The polysilicon production waste gas recovery system according to claim 5, wherein ​ 7. The polysilicon production waste gas recovery system according to claim 5, wherein ​ 8. The polysilicon production waste gas recovery system according to claim 1, wherein ​

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