Tail gas treatment system for polycrystalline silicon production
By recycling hydrogen from polysilicon production through a tail gas treatment system, the problem of wasting unreacted hydrogen has been solved, and safety and economic benefits have been improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- XINJIANG CENT HESHENG SILICON IND CO LTD
- Filing Date
- 2025-02-28
- Publication Date
- 2026-04-17
AI Technical Summary
In polysilicon production, unreacted hydrogen is directly emitted into the reaction tail gas, resulting in wasted electrolytic hydrogen, increased production costs, and reduced economic benefits.
The exhaust gas treatment system includes an exhaust gas scrubbing tower, a buffer tank, a compressor, a hydrogen buffer tank, a hydrogen chloride synthesis furnace, a falling film absorption device, a silicon tetrachloride drying tower, and a trichlorosilane synthesis unit, etc., to recover and utilize hydrogen through steps such as pressurization, scrubbing, drying, and synthesis.
This improved hydrogen recovery rate, enhanced the safety and environmental friendliness of the production process, and reduced production costs, thereby increasing economic benefits.
Smart Images
Figure CN224127240U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of polysilicon production technology, specifically to a waste gas treatment system for polysilicon production. Background Technology
[0002] Currently, polysilicon production is a crucial link in the photovoltaic and semiconductor industries, with production processes primarily including the modified Siemens process and the silane fluidized bed process. Among these, the modified Siemens process is the most mature and widely used, accounting for over 85% of global polysilicon production capacity. One of the core processes of the modified Siemens process is the reaction of hydrogen chloride with industrial silicon powder to produce trichlorosilane (SiHCl3). The generated trichlorosilane is then purified by distillation and reduced with hydrogen at high temperature to produce high-purity polysilicon. The hydrogen chloride synthesis process involves electrolyzing brine to generate hydrogen and chlorine, which are then mixed in a 1.05:1 ratio and burned to produce hydrogen chloride gas.
[0003] However, after using excess hydrogen in the hydrogen chloride synthesis reaction, the remaining unreacted hydrogen is usually mixed in with the reaction tail gas and directly emitted into the atmosphere, making it difficult to recover and reuse. This results in a significant waste of electrolyzed hydrogen, further increasing production costs and reducing economic efficiency. Summary of the Invention
[0004] One objective of this application is to provide a tail gas treatment system for polysilicon production that helps increase hydrogen recovery, improves the safety of the production process, and further reduces environmental pollution.
[0005] Another objective of this application is to provide a tail gas treatment system for polysilicon production that is simple to operate, improves production efficiency, reduces production costs, and increases economic benefits.
[0006] To achieve the above objectives, the technical solution adopted in this application is: a tail gas treatment system for polycrystalline silicon production, used to treat the tail gas after falling film absorption, comprising:
[0007] Tail gas scrubbing tower is used to remove hydrogen chloride from tail gas;
[0008] The exhaust gas buffer tank is used to process exhaust gas that is suitable for input into the exhaust gas buffer tank.
[0009] The exhaust gas compressor is used to pressurize the exhaust gas in the exhaust gas buffer tank, and the pressurized exhaust gas can be recycled.
[0010] In some embodiments, the exhaust gas treatment system further includes a hydrogen buffer tank, to which the exhaust gas pressurized by the exhaust gas compressor is adapted to be delivered.
[0011] In some embodiments, the hydrogen buffer tank is further provided with a hydrogen replenishment pipeline, through which electrolyzed hydrogen enters the hydrogen buffer tank.
[0012] In some embodiments, the exhaust gas treatment system further includes a hydrogen chloride synthesis furnace, the gas in the hydrogen buffer tank is adapted to be input into the hydrogen chloride synthesis furnace, the hydrogen chloride synthesis furnace is also provided with a chlorine delivery pipeline, and chlorine and hydrogen are synthesized into hydrogen chloride in the hydrogen chloride synthesis furnace.
[0013] In some embodiments, the tail gas treatment system further includes a falling film absorption device, the product of the hydrogen chloride synthesis furnace enters the falling film absorption device, and after the falling film absorption device absorbs the hydrogen chloride in the product, the resulting tail gas is transported to the tail gas scrubbing tower.
[0014] In some embodiments, the hydrogen chloride synthesis furnace is further provided with a hydrogen pipeline, and electrolytic hydrogen is adapted to be directly fed into the hydrogen chloride synthesis furnace through the hydrogen pipeline.
[0015] In some embodiments, the exhaust gas treatment system further includes a silicon tetrachloride drying tower, wherein the exhaust gas pressurized by the exhaust gas compressor is suitable for being delivered to the silicon tetrachloride drying tower for drying.
[0016] In some embodiments, the exhaust gas treatment system further includes a trichlorosilane synthesis unit, to which the pressurized exhaust gas dried by the silicon tetrachloride drying tower is delivered.
[0017] In some embodiments, the exhaust gas buffer tank is provided with an emergency venting line at the top and a sewage discharge line at the bottom.
[0018] In some embodiments, the gas pressure inside the exhaust gas buffer tank is 5-10 kPa, the inlet pressure of the exhaust gas compressor is 5-10 kPa, and the outlet pressure of the exhaust gas compressor is 120-180 kPa.
[0019] Compared with the prior art, the beneficial effects of this application are as follows:
[0020] (1) The tail gas treatment system for polysilicon production provided in this application is beneficial to improving the hydrogen recovery rate, thereby enhancing the safety and environmental protection of the production process and further reducing environmental pollution.
[0021] (2) The exhaust gas treatment system for polysilicon production provided in this application has the advantage of simple operation, which can improve production efficiency and reduce production costs and increase economic benefits. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the exhaust gas treatment system in one embodiment of this application.
[0023] In the diagram: 1. Hydrogen supply pipeline; 2. Hydrogen pipeline; 3. Chlorine pipeline; 100. Hydrogen buffer tank; 200. Hydrogen chloride synthesis furnace; 300. Falling film absorption equipment; 400. Tail gas scrubbing tower; 500. Tail gas buffer tank; 600. Tail gas compressor; 700. Silicon tetrachloride drying tower; 800. Trichlorosilane synthesis unit. Detailed Implementation
[0024] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.
[0025] In the description of this application, it should be noted that the directional terms such as "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this application.
[0026] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.
[0027] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.
[0028] This application provides a tail gas treatment system for polycrystalline silicon production, used to treat tail gas after falling film absorption, comprising:
[0029] The exhaust gas scrubbing tower 400 is used to remove hydrogen chloride from the exhaust gas. The exhaust gas scrubbing tower 400 facilitates the recovery of residual hydrogen chloride in the exhaust gas, enabling resource recycling and further reducing environmental pollution.
[0030] The tail gas buffer tank 500 is used to feed tail gas treated by the tail gas scrubbing tower 400. The tail gas buffer tank 500 ensures a stable supply of tail gas, thereby meeting the needs of subsequent treatment or recycling. In other words, the tail gas buffer tank 500 also serves as a buffer device, reducing fluctuations during tail gas treatment and improving the safety and stability of the production process.
[0031] The exhaust gas in the exhaust gas compressor 600 and the exhaust gas buffer tank 500 is suitable for pressurization by the exhaust gas compressor 600, and the pressurized exhaust gas can be recycled. It can be understood that in the exhaust gas recovery process, selecting an appropriate pressure is beneficial to improving the exhaust gas treatment efficiency, thereby enhancing the hydrogen purity, which is beneficial to further improving the reaction purity in subsequent after-treatment units.
[0032] In some embodiments, the exhaust gas treatment system further includes a hydrogen buffer tank 100, to which the exhaust gas, pressurized by the exhaust gas compressor 600, is suitable for delivery. The hydrogen buffer tank 100 ensures the stability of the hydrogen supply, meeting the hydrogen demand during production while preventing production interruptions due to insufficient hydrogen supply. Furthermore, the hydrogen buffer tank 100 acts as a buffer device, reducing fluctuations in hydrogen supply during production consumption and replenishment, further improving the safety and stability of the production process.
[0033] In some embodiments, the hydrogen buffer tank 100 is further provided with a hydrogen replenishment pipeline 1, through which electrolytic hydrogen enters the hydrogen buffer tank 100. By supplying electrolytic hydrogen to the hydrogen chloride synthesis furnace 200, an excess of hydrogen is ensured in the hydrogen chloride synthesis furnace 200, allowing hydrogen and chlorine to react in a 1.05:1 ratio to generate hydrogen chloride gas through combustion. This further ensures that the hydrogen chloride synthesis reaction proceeds fully, thereby increasing the yield of hydrogen chloride.
[0034] In some embodiments, the exhaust gas treatment system further includes a hydrogen chloride synthesis furnace 200. Gas in the hydrogen buffer tank 100 is suitable for input into the hydrogen chloride synthesis furnace 200. The hydrogen chloride synthesis furnace 200 is also equipped with a chlorine delivery pipeline. Chlorine and hydrogen are synthesized into hydrogen chloride within the hydrogen chloride synthesis furnace 200. It is understood that the hydrogen chloride synthesis furnace 200 is a key piece of equipment for the reaction of hydrogen and chlorine to produce hydrogen chloride, enabling the reaction to proceed at high temperatures and improving reaction efficiency. On the other hand, the hydrogen chloride synthesis furnace 200 can also serve as a heat recovery system, using the heat generated by the reaction for other production processes, further reducing energy consumption during production.
[0035] In some embodiments, the tail gas treatment system further includes a falling film absorber 300. The product from the hydrogen chloride synthesis furnace 200 enters the falling film absorber 300. After the falling film absorber 300 absorbs the hydrogen chloride in the product, the resulting tail gas is transported to the tail gas scrubbing tower 400. It is understood that the falling film absorber 300 can effectively absorb hydrogen chloride gas to generate hydrochloric acid with a mass fraction of 30 wt.% to 35 wt.%, exhibiting high absorption efficiency and suitability for large-scale production. Furthermore, the cooling system of the falling film absorber 300 can effectively remove the heat released during the absorption process, avoiding the risk of overheating in the production system.
[0036] In some embodiments, the hydrogen chloride synthesis furnace 200 is further provided with a hydrogen pipeline 2, through which electrolyzed hydrogen is directly fed into the hydrogen chloride synthesis furnace 200. Supplying hydrogen to the hydrogen chloride synthesis furnace 200 via the hydrogen pipeline 2 further ensures that there is an excess of hydrogen in the furnace, allowing hydrogen and chlorine to react in a 1.05:1 ratio to generate hydrogen chloride gas. This ensures that the hydrogen chloride synthesis reaction proceeds fully, thereby increasing the yield of hydrogen chloride.
[0037] In some embodiments, the hydrogen chloride synthesis furnace 200 is further provided with a chlorine pipeline 3, through which electrolytic chlorine gas is directly fed into the hydrogen chloride synthesis furnace 200. Supplying chlorine gas to the hydrogen chloride synthesis furnace 200 via the chlorine pipeline 3 further ensures that there is sufficient chlorine gas in the hydrogen chloride synthesis furnace 200 to react with hydrogen gas to generate hydrogen chloride gas, thereby ensuring that the hydrogen chloride synthesis reaction proceeds fully and thus improving the yield of hydrogen chloride.
[0038] In some embodiments, the exhaust gas treatment system further includes a silicon tetrachloride drying tower 700, to which the exhaust gas, pressurized by the exhaust gas compressor 600, is suitable for drying. The silicon tetrachloride drying tower 700 removes water molecules from the gas, thereby increasing the purity of the hydrogen and enabling its recycling.
[0039] In some embodiments, the exhaust gas treatment system further includes a trichlorosilane synthesis unit 800, to which pressurized exhaust gas, dried by a silicon tetrachloride drying tower 700, is supplied. The trichlorosilane synthesis unit 800 can efficiently synthesize high-purity trichlorosilane from silicon powder and hydrogen chloride gas under certain temperature and pressure. Introducing high-purity hydrogen gas effectively reduces the introduction of impurities, thereby improving the purity of trichlorosilane. During the synthesis process, the purity of hydrogen gas directly affects the purity of the product. High-purity hydrogen gas helps produce high-purity trichlorosilane, reducing byproducts generated from reactions with impurities, such as silicon tetrachloride. The reduction of byproducts helps increase the yield of trichlorosilane, further reducing production costs.
[0040] In some embodiments, the exhaust gas buffer tank 500 is equipped with an emergency vent line at the top and a drain line at the bottom. Furthermore, the emergency vent line can rapidly release gas when the pressure in the exhaust gas buffer tank 500 is too high, preventing overpressure and ensuring the safety of the equipment and personnel. The drain line can periodically discharge liquid impurities and deposits from the bottom of the exhaust gas buffer tank 500, keeping the inside of the equipment clean.
[0041] In some embodiments, the gas pressure inside the exhaust gas buffer tank 500 is 5–10 kPa, the inlet pressure of the exhaust gas compressor 600 is 5–10 kPa, and the outlet pressure of the exhaust gas compressor 600 is 120–180 kPa. It is understood that in the exhaust gas recovery process, selecting an appropriate pressure is beneficial to improving exhaust gas treatment efficiency, thereby enhancing hydrogen purity, which is conducive to further improving reaction purity in subsequent after-treatment units.
[0042] In some embodiments, the exhaust gas compressor 600 is provided with an inlet and an outlet. The inlet is connected to the exhaust gas scrubbing tower 400 and is adapted to separate the gas conveyed by the exhaust gas scrubbing tower 400. The outlet includes a first outlet and a second outlet, wherein the first outlet is adapted to convey the gas in the exhaust gas compressor 600 to the post-processing unit, and the second outlet is adapted to convey at least a portion of the gas in the exhaust gas compressor 600 to the hydrogen buffer tank 100. The exhaust gas compressor 600 compresses and conveys the recovered hydrogen and a small amount of protective gas, such as nitrogen, from the hydrogen chloride synthesis furnace 200 to the hydrogen buffer tank 100 and the post-processing unit, realizing the reuse of recovered hydrogen, improving the exhaust gas treatment efficiency, and enhancing safety in the production process while improving economic benefits.
[0043] In some embodiments, the pressure of the hydrogen buffer tank 100 is 110 kPa to 120 kPa, and more preferably, the pressure of the hydrogen buffer tank 100 is 112 kPa to 115 kPa. When the pressure in the hydrogen buffer tank 100 is too high, although the amount of hydrogen stored per unit volume can be increased, improving storage efficiency, the risk of hydrogen leakage under high pressure is further increased, potentially leading to safety accidents such as fires or explosions. In other words, when the pressure in the hydrogen buffer tank 100 is too low, although low pressure can significantly reduce the risk of hydrogen leakage and explosion, improve system safety, and further reduce equipment maintenance costs, the amount of hydrogen stored per unit volume is reduced under low pressure, making it difficult to cope with fluctuations in hydrogen demand during production, thus affecting production continuity. Furthermore, if frequent refilling is required to maintain the low pressure level, energy consumption is further increased. Therefore, selecting a suitable pressure for the hydrogen buffer tank 100 is beneficial for reducing costs and improving production efficiency.
[0044] In some embodiments, the pressure of the hydrogen chloride synthesis furnace 200 is 70 kPa to 90 kPa, and more preferably, the pressure is 75 kPa to 85 kPa. Since the hydrogen chloride synthesis furnace 200 is used to produce hydrogen chloride gas, when the pressure in the hydrogen chloride synthesis furnace 200 is too high, although high pressure can increase the collision frequency of gas molecules, thereby increasing the reaction rate and helping to improve production efficiency, a high-pressure environment requires more energy consumption, further increasing production costs, and increasing the risk of safety accidents such as leaks and explosions. In other words, when the pressure in the hydrogen chloride synthesis furnace 200 is too low, it may lead to a decrease in the collision frequency between gas molecules, thereby slowing down the reaction rate and further reducing production efficiency. It is understood that selecting a suitable pressure for the hydrogen chloride synthesis furnace 200 can improve reaction efficiency while reducing energy consumption and enhancing equipment safety and service life.
[0045] In some embodiments, the pressure of the falling film absorber 300 is 8 kPa to 65 kPa, and more preferably, the pressure of the falling film absorber 300 is 10 kPa to 60 kPa. It is understood that when the pressure in the falling film absorber 300 is too high, the absorption of hydrogen chloride can be increased, but this may increase energy consumption and production costs. When the pressure in the falling film absorber 300 is too low, the absorption of hydrogen chloride may decrease, thereby increasing the concentration of hydrogen chloride in the exhaust gas, further increasing the difficulty and cost of exhaust gas treatment. In other words, selecting a suitable pressure for the falling film absorber 300 is beneficial to improving the recovery efficiency of hydrogen chloride, reducing the difficulty of exhaust gas post-treatment, and further improving the environmental friendliness and safety of the production system.
[0046] In some embodiments, the pressure of the tail gas scrubbing tower 400 is 10 kPa to 50 kPa, and more preferably, the pressure of the tail gas scrubbing tower 400 is 10 kPa to 40 kPa. It is understood that when the pressure of the tail gas scrubbing tower 400 is too high, it is beneficial to improve the efficiency of removing impurities such as residual hydrogen chloride gas, further enhancing the purity of the recovered hydrogen and increasing economic benefits. When the pressure of the tail gas scrubbing tower 400 is too low, it may lead to a further increase in the concentration of hydrogen chloride in the tail gas, thereby increasing the difficulty and cost of tail gas treatment. Therefore, selecting a suitable pressure for the tail gas scrubbing tower 400 is beneficial to enhancing the purity of the recovered hydrogen and improving the efficiency and reaction purity of subsequent production.
[0047] In some embodiments, the pressure of the silicon tetrachloride drying tower 700 is 40 kPa to 60 kPa. Specifically, the pressure of the silicon tetrachloride drying tower 700 is 40 kPa, 42 kPa, 44 kPa, 46 kPa, 48 kPa, 50 kPa, 52 kPa, 54 kPa, 56 kPa, 58 kPa, or 60 kPa. More preferably, the pressure of the silicon tetrachloride drying tower 700 is 50 kPa. It is understood that when the pressure in the silicon tetrachloride drying tower 700 is too high, it can effectively dry the hydrogen chloride gas and remove moisture, thereby improving drying efficiency. When the pressure in the silicon tetrachloride drying tower 700 is too low, it slows down the drying efficiency, further affecting production efficiency. Therefore, selecting a suitable pressure for the silicon tetrachloride drying tower 700 is beneficial to reduce energy consumption, improve equipment safety, and extend its service life while ensuring drying efficiency.
[0048] In some embodiments, the pressure of the exhaust gas buffer tank 500 is 5 kPa to 10 kPa, specifically, the pressure of the exhaust gas buffer tank 500 is 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, or 10 kPa. It is understood that selecting an appropriate pressure for the exhaust gas buffer tank 500 can improve exhaust gas treatment efficiency while reducing energy consumption and increasing equipment safety and service life.
[0049] In some embodiments, the pressure at the inlet of the exhaust gas compressor 600 is 5 kPa to 10 kPa. Specifically, the pressure at the inlet of the exhaust gas compressor 600 is 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, or 10 kPa. More preferably, the pressure at the inlet of the exhaust gas compressor 600 is 5 kPa. The pressure of the exhaust gas output from the exhaust port of the exhaust gas compressor 600 is 140 kPa to 160 kPa. Specifically, the pressure of the exhaust gas output from the exhaust port of the exhaust gas compressor 600 is 140 kPa, 142 kPa, 144 kPa, 146 kPa, 148 kPa, 150 kPa, 152 kPa, 154 kPa, 156 kPa, 158 kPa, or 160 kPa. More preferably, the pressure of the exhaust gas output from the exhaust port of the exhaust gas compressor 600 is 150 kPa. Understandably, in the tail gas recovery process, selecting an appropriate pressure is beneficial to improving tail gas treatment efficiency, thereby enhancing hydrogen purity, which is conducive to further improving reaction purity in subsequent post-treatment units.
[0050] In some embodiments, the pressure of the hydrogen buffer tank 100 is 112 kPa to 115 kPa, the pressure of the hydrogen chloride synthesis furnace 200 is 75 kPa to 85 kPa, the pressure of the falling film absorption device 300 is 10 kPa to 60 kPa, and the pressure of the tail gas scrubbing tower 400 is 10 kPa to 40 kPa. It is understood that selecting an appropriate pressure in the tail gas recovery process is beneficial to improving tail gas treatment efficiency, thereby enhancing hydrogen purity, and further improving reaction purity in subsequent post-treatment units.
[0051] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.
Claims
1. A polysilicon production off-gas treatment system for treating off-gas after falling film absorption, characterized by, include: Tail gas scrubbing tower is used to remove hydrogen chloride from tail gas; The exhaust gas buffer tank is used to process exhaust gas that is suitable for input into the exhaust gas buffer tank. The exhaust gas compressor is used to pressurize the exhaust gas in the exhaust gas buffer tank, and the pressurized exhaust gas can be recycled.
2. The off-gas treatment system according to claim 1, characterized by, It also includes a hydrogen buffer tank, to which the exhaust gas, pressurized by the exhaust gas compressor, is suitable for delivery.
3. The off-gas treatment system of claim 2, wherein, The hydrogen buffer tank is also equipped with a hydrogen replenishment pipeline, through which electrolyzed hydrogen enters the hydrogen buffer tank.
4. The off-gas treatment system of claim 2, wherein, It also includes a hydrogen chloride synthesis furnace, wherein the gas in the hydrogen buffer tank is suitable for input into the hydrogen chloride synthesis furnace, and the hydrogen chloride synthesis furnace is also equipped with a chlorine gas delivery pipeline, wherein chlorine and hydrogen are synthesized into hydrogen chloride in the hydrogen chloride synthesis furnace.
5. The off-gas treatment system according to claim 4, characterized by It also includes a falling film absorption device, the product of the hydrogen chloride synthesis furnace enters the falling film absorption device, and after the falling film absorption device absorbs the hydrogen chloride in the product, the generated tail gas is transported to the tail gas scrubbing tower.
6. The off-gas treatment system of claim 4, wherein, The hydrogen chloride synthesis furnace is also equipped with a hydrogen pipeline, and electrolytic hydrogen is suitable for being directly fed into the hydrogen chloride synthesis furnace through the hydrogen pipeline.
7. The off-gas treatment system of claim 1, wherein, It also includes a silicon tetrachloride drying tower, to which the exhaust gas, pressurized by the exhaust gas compressor, is suitable for drying.
8. The off-gas treatment system according to claim 7, characterized by It also includes a trichlorosilane synthesis unit, to which pressurized tail gas dried by the silicon tetrachloride drying tower is transported.
9. The exhaust gas treatment system according to any one of claims 1-8, characterized in that, The exhaust gas buffer tank is equipped with an emergency venting pipeline at the top and a sewage discharge pipeline at the bottom.
10. The off-gas treatment system of claim 1, wherein, The gas pressure inside the exhaust gas buffer tank is 5~10 kPa, the inlet pressure of the exhaust gas compressor is 5~10 kPa, and the outlet pressure of the exhaust gas compressor is 120 kPa~180 kPa.