A raw material recycling system for polysilicon production

Abstract

This utility model relates to the technical field of polysilicon production equipment, and particularly to a raw material recycling system for polysilicon production. The system includes a tail gas section connected to a reduction section; a raw material storage tank connected to the tail gas section; a feed inlet of reduction tower one connected to the raw material storage tank; a feed inlet of reduction tower two connected to reduction tower one; a liquid phase outlet of reduction tower two connected to reduction tower one; a high-purity storage tank connected to the side outlet of reduction tower two; a high-purity storage tank connected to the feed inlet of the reduction section via pipeline three; pressure, density, and temperature sensors installed on pipeline three; a disproportionation reactor connected to reduction tower two via pipeline four; pipeline four and pipeline two connected via pipeline five; a flow regulating valve installed on pipeline five; and a control system connected to the sensors and the flow regulating valve. This utility model fully utilizes the reduction tail gas to monitor and control the dichlorosilane content in the high-purity chlorosilane supplied to the reduction section.

Description

Technical Field

[0001] This utility model relates to the technical field of polysilicon production equipment, and in particular to a raw material recycling system for polysilicon production. Background Technology

[0002] Currently, the main method for producing polycrystalline silicon is the modified Siemens process. This process introduces trichlorosilane (TCS) and hydrogen into a reduction furnace, where polycrystalline silicon is deposited on a silicon core at 1100°C. Due to conversion limitations, trichlorosilane cannot react completely, and the unreacted material is called reduction tail gas. The main components of the reduction tail gas are hydrogen, hydrogen chloride, and chlorosilanes, including dichlorosilane (DCS), trichlorosilane, and silicon tetrachloride (STC). In the polycrystalline silicon production process, a certain proportion of dichlorosilane is usually added to the trichlorosilane during the feeding process in the reduction section to accelerate the reaction rate and reduce energy consumption. However, dichlorosilane has a double-edged sword effect: too low a proportion will reduce the reaction efficiency and increase energy consumption; too high a proportion will result in amorphous silicon powder. Excessive silicon powder adheres to the surface of the silicon rod, forming a dark brown interlayer, leading to uneven silicon rod deposition or structural defects. It can also adhere to the area between the chassis and electrodes, causing the reduction furnace to ground and shut down.

[0003] In existing technologies, the reduction tail gas is usually separated, purified, and stored separately. When raw materials are needed, they are supplied by purchasing or recycling raw materials. The content of dichlorodihydrosilane in trichlorosilane is detected by gas chromatography. However, gas chromatography has strict requirements for detection conditions, especially the temperature of the material. The temperature of the material needs to be adjusted for detection. Furthermore, polysilicon production facilities are generally explosion-proof areas. Although explosion-proof chromatographs meet the explosion-proof requirements, they are large, have poor heat dissipation, have a high failure rate in high-temperature environments (>40℃), require long-term maintenance, and have high energy consumption. Building an independent explosion-proof analysis cabin requires an infrastructure investment of over 500,000 yuan, which is costly. Utility Model Content

[0004] In view of this, the present invention provides a raw material recycling system for polysilicon production. The main purpose is to make full use of the reduction tail gas, reduce dependence on purchased raw materials, realize real-time monitoring and stable control of the dichlorosilane content in the high-purity chlorosilane supplied in the reduction section, and achieve low detection and control costs.

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

[0006] An embodiment of this utility model provides a raw material recycling system for polysilicon production, comprising: System 1; System 1 includes: a reduction section, a tail gas section, a raw material storage tank, a reduction tower 1, a reduction tower 2, a high-purity storage tank, a disproportionation reactor, and a control system;

[0007] The reduction section uses chlorosilane raw materials to produce polycrystalline silicon through vapor deposition reaction in a reduction furnace.

[0008] The exhaust gas section is connected to the reduction section and is used to recover the exhaust gas discharged from the reduction section.

[0009] The reducing material storage tank is connected to the tail gas section and is used to store the chlorosilane recovered by the tail gas section;

[0010] The feed inlet of the reduction tower is connected to the raw material storage tank via a pipeline; a delivery pump is installed on the pipeline.

[0011] The feed inlet of the second reduction tower is connected to the gas phase outlet of the first reduction tower; the liquid phase outlet of the second reduction tower is connected to the feed inlet of the first reduction tower.

[0012] The inlet of the high-purity storage tank is connected to the side outlet of the reduction tower 2 via pipeline 2.

[0013] The high-purity storage tank is connected to the feed inlet of the reduction section via pipeline three; a second conveying pump is installed on pipeline three; a pressure sensor, a density sensor, and a temperature sensor are installed on pipeline three.

[0014] The disproportionation reactor is connected to the gas phase outlet of the reduction tower 2 via pipeline 4; a transfer pump 3 is installed on pipeline 4.

[0015] Pipeline 4 is connected to pipeline 2 via pipeline 5; a flow regulating valve is installed on pipeline 5; a delivery pump 4 is installed on pipeline 5.

[0016] The control system is connected to the pressure sensor, density sensor, temperature sensor and flow regulating valve respectively, and is used to receive data from the pressure sensor, density sensor and temperature sensor, calculate and analyze the data and then control the flow regulating valve; the control system has a built-in model based on pressure, density and temperature.

[0017] Furthermore, it also includes: System 2;

[0018] The second system has the same settings as the first system;

[0019] The high-purity storage tank of System 2 is connected to the high-purity storage tank of System 1 via pipeline 7; a transfer pump 5 is installed on pipeline 7.

[0020] Furthermore, it also includes: System Three;

[0021] The settings of System 3 are the same as those of System 1;

[0022] The high-purity storage tank of System 3 is connected to the high-purity storage tanks of System 1 and System 2 via pipeline 8 and pipeline 9; a transfer pump 6 is installed on pipeline 8; and a transfer pump 7 is installed on pipeline 9.

[0023] Furthermore, the disproportionation reactor is provided with a silicon tetrachloride inlet for generating trichlorosilane within the reactor; the outlet of the disproportionation reactor is connected to a distillation system for distilling the extracted trichlorosilane.

[0024] By employing the above technical solution, the raw material recycling system for polysilicon production of this utility model has at least the following advantages:

[0025] It can make full use of the reduction tail gas, reduce dependence on purchased raw materials, and realize real-time monitoring and stable control of the dichlorosilane content in the high-purity chlorosilane supplied to the reduction section, with low detection and control costs.

[0026] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, the preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 A schematic diagram of a raw material recycling system for polysilicon production provided in this embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of a raw material recycling system for polysilicon production, provided as another embodiment of the present invention.

[0029] As shown in the figure:

[0030] 1 is the reduction section, 2 is the tail gas section, 3 is the raw material storage tank, 4 is reduction tower one, 5 is reduction tower two, 6 is the disproportionation reactor, 7 is the high-purity storage tank, and 8 is the control system. Detailed Implementation

[0031] To further illustrate the technical means and effects adopted by this utility model to achieve its intended purpose, the specific implementation methods, structures, features, and effects according to this utility model application are described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0032] like Figure 1As shown, an embodiment of this utility model proposes a raw material recycling system for polysilicon production, comprising: System 1; System 1 includes: reduction section 1, tail gas section 2, raw material storage tank 3, reduction tower 1 4, reduction tower 2 5, high-purity storage tank 7, disproportionation reactor 6, and control system 8;

[0033] The reduction section 1 uses chlorosilane feedstock for vapor deposition reaction in a reduction furnace to produce polycrystalline silicon. The tail gas section 2 is connected to the reduction section 1 and is used to recover the tail gas discharged from the reduction section 1, separating and recovering hydrogen, hydrogen chloride, and chlorosilane. The feedstock storage tank 3 is connected to the tail gas section 2 and is used to store the chlorosilane recovered from the tail gas section 2.

[0034] The feed inlet of reduction tower 4 is connected to the raw material storage tank 3 via pipeline 1 for separating chlorosilanes; a transfer pump 1 is installed on pipeline 1 for conveying materials. The feed inlet of reduction tower 5 is connected to the gas phase outlet of reduction tower 4 for further separation of trichlorosilane and dichlorosilane; the liquid phase outlet of reduction tower 5 is connected to the feed inlet of reduction tower 4, and the reflux liquid continues to be separated. The feed inlet of high-purity storage tank 7 is connected to the side outlet of reduction tower 5 via pipeline 2; dichlorosilane is collected from the top of reduction tower 5; trichlorosilane is collected from the side of reduction tower 5; the residue from the bottom of reduction tower 5 is returned to reduction tower 4; a portion of the dichlorosilane collected from the top of reduction tower 5 enters the disproportionation reactor 6 to react with silicon tetrachloride to produce trichlorosilane; the trichlorosilane produced in the disproportionation reactor 6 can be transported to the distillation system for purification for further utilization. Of the dichlorosilane extracted from the top of reduction tower 25, another portion is diverted to pipeline 2, where it enters high-purity storage tank 7 together with the trichlorosilane extracted from the side of reduction tower 25. The other part of the material entering high-purity storage tank 7 is transferred from other systems. The trichlorosilane and dichlorosilane from the two sources are mixed and stored in high-purity storage tank 7.

[0035] The high-purity storage tank 7 is connected to the feed inlet of the reduction section 1 via pipeline 3; a transfer pump 2 is installed on pipeline 3; a pressure sensor, a density sensor and a temperature sensor are installed on pipeline 3 to detect the pressure, density and temperature of the material in pipeline 3.

[0036] The disproportionation reactor 6 is connected to the gas phase outlet of the reduction tower 2 5 via pipeline 4; a transfer pump 3 is installed on pipeline 4; a silicon tetrachloride inlet is installed on the disproportionation reactor 6 for generating trichlorosilane within the reactor; the outlet of the disproportionation reactor 6 is connected to a distillation system for distilling the collected trichlorosilane. Silicon tetrachloride is introduced into the disproportionation tower, where it reacts with dichlorosilane to generate trichlorosilane. Pipeline 4 is connected to pipeline 2 via pipeline 5; a flow regulating valve and a transfer pump 4 are installed on pipeline 5 to regulate the flow rate of dichlorosilane.

[0037] Control system 8 is connected to pressure sensors, density sensors, temperature sensors, and flow control valves, respectively. It receives data from these sensors, analyzes the data, and then controls the flow control valves. Control system 8 has a built-in model based on pressure, density, and temperature. The mixed density under different dichlorosilane ratios, considering mass fraction weighting and high-pressure compression effects, requires state correction under different pressures and temperatures. By establishing a model, the real-time dichlorosilane content can be obtained. Pressure, density, and temperature sensors monitor the compositional changes of dichlorosilane and trichlorosilane in real time. Simultaneously, interlocks are set in control system 8 to determine the required dichlorosilane ratio. The deviation between the monitored data and the set data is used to adjust the dichlorosilane dosage. This ratio data is also referenced to reduction section 1, which adjusts the reduction reaction formula parameters based on the real-time ratio data to achieve optimal reduction reaction efficiency and reduce energy consumption throughout the polysilicon production process. The control system 8, combined with the stable detection and control of field instruments, can stabilize the reaction rate in the reduction furnace, improve the primary conversion rate, avoid atomization in the reduction furnace, and reduce the number of abnormalities in the reduction furnace, which is of great significance for promoting the reduction of energy consumption in the polysilicon industry.

[0038] An embodiment of this utility model proposes a raw material recycling system for polysilicon production, which can make full use of reduction tail gas, avoid loss of chlorosilane, reduce dependence on purchased raw materials, realize real-time monitoring and stable control of dichlorosilane content in high-purity chlorosilane supplied by reduction section 1, and has low detection and control costs, solving the problems of difficult and expensive implementation of online chromatography.

[0039] refer to Figure 2 An embodiment of this utility model proposes a raw material recycling system for polysilicon production, which further includes: System 2; System 2 is configured the same as System 1; the high-purity storage tank 7 of System 2 is connected to the high-purity storage tank 7 of System 1 through pipeline 7; pipeline 7 is equipped with a transfer pump 5, which can mutually supplement the trichlorosilane and dichlorosilane in System 1 and System 2, enabling material allocation between different production lines and facilitating balanced material supply.

[0040] An embodiment of this utility model proposes a raw material recycling system for polysilicon production, which further includes: System 3; System 3 is configured the same as System 1; the high-purity storage tank 7 of System 3 is connected to the high-purity storage tanks 7 of System 1 and System 2 through pipelines 8 and 9; a transfer pump 6 is installed on pipeline 8; a transfer pump 7 is installed on pipeline 9, which can mutually supplement trichlorosilane and dichlorosilane in System 1, System 2 and System 3, realize material allocation for different production lines, and facilitate balanced material supply.

[0041] To further clarify, while the terms "first," "second," etc., may be used herein to describe various elements, these terms should not limit the elements. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element; these terms are used only to distinguish one element from another. This does not depart from the scope of the exemplary embodiments. Similarly, "element one," "element two," and so on do not represent the order of elements; these terms are used only to distinguish one element from another. As used herein, the term "and / or" includes any and all combinations of one or more associated listed items.

[0042] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing" 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 or an electrical 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 this utility model based on the specific circumstances.

[0043] All standard parts used in this utility model can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here.

[0044] 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, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the scope of the technical solution of the present utility model.

Claims

1. A raw material recycling system for polysilicon production, characterized in that, Includes: System 1; System 1 includes: reduction section, tail gas section, raw material storage tank, reduction tower 1, reduction tower 2, high-purity storage tank, disproportionation reactor and control system; The reduction section uses chlorosilane raw materials to produce polycrystalline silicon through vapor deposition reaction in a reduction furnace. The exhaust gas section is connected to the reduction section and is used to recover the exhaust gas discharged from the reduction section. The reducing material storage tank is connected to the tail gas section and is used to store the chlorosilane recovered by the tail gas section; The feed inlet of the reduction tower is connected to the raw material storage tank via a pipeline; a delivery pump is installed on the pipeline. The feed inlet of the second reduction tower is connected to the gas phase outlet of the first reduction tower; the liquid phase outlet of the second reduction tower is connected to the feed inlet of the first reduction tower. The inlet of the high-purity storage tank is connected to the side outlet of the reduction tower 2 via pipeline 2. The high-purity storage tank is connected to the feed inlet of the reduction section via pipeline three; a second conveying pump is installed on pipeline three; a pressure sensor, a density sensor, and a temperature sensor are installed on pipeline three. The disproportionation reactor is connected to the gas phase outlet of the reduction tower 2 via pipeline 4; a transfer pump 3 is installed on pipeline 4. Pipeline 4 is connected to pipeline 2 via pipeline 5; a flow regulating valve is installed on pipeline 5; a delivery pump 4 is installed on pipeline 5. The control system is connected to the pressure sensor, density sensor, temperature sensor and flow regulating valve respectively, and is used to receive data from the pressure sensor, density sensor and temperature sensor, calculate and analyze the data and then control the flow regulating valve; the control system has a built-in model based on pressure, density and temperature.

2. The raw material recycling system for polycrystalline silicon production according to claim 1, characterized in that, Also includes: System 2; The second system has the same settings as the first system; The high-purity storage tank of System 2 is connected to the high-purity storage tank of System 1 via pipeline 7; a transfer pump 5 is installed on pipeline 7.

3. The raw material recycling system for polycrystalline silicon production according to claim 2, characterized in that, Also includes: System 3; The settings of System 3 are the same as those of System 1; The high-purity storage tank of System 3 is connected to the high-purity storage tanks of System 1 and System 2 via pipeline 8 and pipeline 9; a transfer pump 6 is installed on pipeline 8; and a transfer pump 7 is installed on pipeline 9.

4. The raw material recycling system for polycrystalline silicon production according to claim 1, characterized in that, The disproportionation reactor is equipped with a silicon tetrachloride inlet for generating trichlorosilane within the reactor; the outlet of the disproportionation reactor is connected to a distillation system for distilling the extracted trichlorosilane.

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