A hydrogen chloride recovery system and method for polycrystalline silicon tail gas

Abstract

The present invention provides a recovery system and a recovery method for hydrogen chloride in polysilicon tail gas, comprising a hydrogen chloride recovery absorption tower and a pressure pump; the hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower is communicated with the hydrogen chloride recovery outlet of a tail gas hydrogen chloride desorption tower, and the inlet of the pressure pump is communicated with the hydrogen chloride-silicon chlorosilane outlet of the hydrogen chloride recovery absorption tower; the hydrogen chloride recovery absorption tower has a silicon tetrachloride inlet. This recovery system not only has excellent safety performance, but also can effectively save energy consumption and material consumption in the process of polysilicon tail gas recovery, reduce the production cost of tail gas recovery, and improve the competitiveness of enterprises.

Description

Technical Field

[0001] The present invention relates to a recovery system and a recovery method for hydrogen chloride in polysilicon tail gas, and belongs to the technical field of polysilicon production. Background Art

[0002] Polysilicon is a key material for manufacturing integrated circuits, photovoltaic solar cells and high-purity silicon products. With the rapid development of the electronic information industry and the solar photovoltaic industry, the market demand for polysilicon is increasing continuously. At present, the mainstream process for preparing polysilicon is the improved Siemens process, in which industrial silicon reacts with silicon tetrachloride, hydrogen chloride and hydrogen recovered from the reduction tail gas. After the reaction system is dust-removed, hydrogen and a mixed liquid composed of trichlorosilane generated by the reaction, unreacted silicon tetrachloride, etc. are obtained through condensation and recovery separation. The hydrogen returns to the system to participate in the reaction again, and the mixed liquid is separated by distillation to obtain high-purity trichlorosilane (silicon tetrachloride is purified and then recycled for hydrogenation and utilization), and then the vaporized trichlorosilane and hydrogen are mixed in a certain proportion and introduced into the polysilicon reduction furnace. A voltage is applied to both ends of the rod-shaped silicon core placed in the reduction furnace to generate high temperature. On the surface of the high-temperature silicon core, trichlorosilane is reduced by hydrogen to elemental silicon and deposited on the surface of the silicon core, gradually generating polysilicon rods of the required specifications. Only about 8-12% of the trichlorosilane entering the reduction furnace is converted into polysilicon, and the reduction tail gas contains a large amount of unreacted production raw materials hydrogen (H 2 ), trichlorosilane (SiHCl 3 ), and reaction by-products silicon tetrachloride (SiCl 4 ), hydrogen chloride (HCl), dichlorosilane (SiH 2 Cl 2 ), etc. Through the tail gas recovery device, through "dry" separation and recovery, the separated chlorosilane is sent to distillation and purification, the hydrogen returns to the reduction furnace for recycling, and the hydrogen chloride is sent to the cold hydrogenation device.

[0003] The existing tail gas recovery process adopts dry recovery technology, and basically can completely separate and recover each component in the reduction tail gas. However, with the development of polysilicon technology, there is still a contradiction between improving the quality of the recovered products and increasing energy consumption in the tail gas recovery process. Figure 1 FIG. is a schematic diagram of the polysilicon tail gas recovery process in the prior art; Figure 2 FIG. is a schematic diagram of the polysilicon tail gas recovery system in the prior art. As Figure 1 and Figure 2As shown in the figure, the existing polysilicon tail gas recovery system includes a tail gas condensation unit, a hydrogen compression unit, a tail gas hydrogen chloride absorption unit, a tail gas hydrogen chloride desorption unit, and a hydrogen adsorption unit; among them, the reduction tail gas is initially subjected to gas-liquid separation of hydrogen tail gas (containing hydrogen chloride and a small amount of chlorosilane) and chlorosilane (mainly trichlorosilane and tetrachlorosilane) by the tail gas condensation unit; the non-condensable hydrogen generated by the tail gas condensation unit is sent to the tail gas hydrogen chloride absorption unit (tail gas hydrogen chloride absorption tower 1) after being pressurized by the hydrogen compression unit. In the tail gas hydrogen chloride absorption unit, chlorosilane will absorb hydrogen chloride in the hydrogen tail gas. The hydrogen with hydrogen chloride removed produced by the tail gas hydrogen chloride absorption unit is further purified by the hydrogen adsorption unit to obtain recovered hydrogen with a purity of 99.9999% for use in the reduction unit and other units. The by-product chlorosilane waste liquid regenerated by the hydrogen adsorption unit is sent to the rectification unit; the chlorosilane generated by the tail gas condensation unit and the chlorosilane rich liquid rich in hydrogen chloride output from the tail gas hydrogen chloride absorption unit (tail gas hydrogen chloride absorption tower 1) enter the tail gas hydrogen chloride desorption unit (tail gas hydrogen chloride desorption tower 2) together to desorb hydrogen chloride by heating and reducing pressure. The recovered hydrogen chloride (containing hydrogen chloride, a small amount of hydrogen, and a small amount of dichlorosilane) produced at the top of the tower is sent to the cold hydrogenation unit or the trichlorosilane synthesis unit. A part of the chlorosilane lean liquid at the bottom of the tower is sent to the tail gas hydrogen chloride unit as an absorbent to the tail gas hydrogen chloride absorption unit, and a part is sent to the rectification unit as a recovered product for further treatment.

[0004] At present, the recovered hydrogen chloride produced at the top of the tail gas hydrogen chloride desorption tower 2 is mainly extracted by liquid-phase extraction or gas-phase extraction. Among them, since the normal boiling point of hydrogen chloride is -85°C and the condensation temperature is low, when performing liquid-phase extraction of the recovered hydrogen chloride, a large amount of low-temperature refrigerant is required at the top of the tail gas hydrogen chloride desorption tower 2 to convert the recovered hydrogen chloride into a liquid phase, and a large amount of steam is consumed at the bottom of the tail gas hydrogen chloride desorption tower 2 to provide energy for the tail gas hydrogen chloride desorption tower 2, resulting in relatively high energy consumption; and when performing liquid-phase extraction, it is also necessary to increase the operating pressure of the tail gas hydrogen chloride absorption tower 1 and the tail gas hydrogen chloride desorption tower 2, and have relatively high requirements for the compression ratio and compression power of the hydrogen compression unit; in addition, the saturated vapor pressure of hydrogen chloride is 4225.6 kPa (20°C), which also requires relatively high design pressure for equipment and pipelines, and in order to improve the safety performance of the system, it is also necessary to set safety valves between equipment and valves, resulting in high investment costs.

[0005] Regarding the gas-phase extraction scheme for recovering hydrogen chloride, under normal circumstances, the pressure of the gas-phase hydrogen chloride recovered from the tail gas hydrogen chloride stripping column 2 is 0.4 - 0.9 MPaG. In order to enable the gas-phase hydrogen chloride recovered from the top of the tail gas hydrogen chloride stripping column 2 to enter the cold hydrogeneration unit for polysilicon production, it is necessary to pressurize the gas-phase hydrogen chloride recovered from the top of the tail gas hydrogen chloride stripping column 2 according to the pressure of the cold hydrogeneration unit (3.5 MPaG and above). Therefore, it is necessary to add a compressor to pressurize the gas-phase hydrogen chloride recovered from the top of the tail gas hydrogen chloride stripping column 2. However, if the gas-phase hydrogen chloride recovered from the top of the tail gas hydrogen chloride stripping column 2 is pressurized alone, a diaphragm compressor needs to be used. However, the diaphragm compressor has a small compressor delivery capacity, large gas delivery pressure pulsation, high cost, and in practical applications, the diaphragm compressor also has defects such as easy corrosion of the connecting rod and unstable operation, and even problems such as frequent failures leading to frequent shutdowns. Since the hydrogen gas generated by the hydrogen adsorption unit after regeneration can also enter the cold hydrogeneration unit to participate in the cold hydrogeneration reaction, the regenerated hydrogen and the gas-phase tail gas hydrogen chloride generated by the tail gas hydrogen chloride stripping column 2 can be mixed and pressurized. Since the content of hydrogen gas in the compressed gas after mixed pressurization is relatively high and the content of hydrogen chloride is relatively low (below 15%), a hydrogen compressor can be used for pressurization. The commonly used hydrogen compressor is a reciprocating compressor. Although the use of a reciprocating compressor can overcome the disadvantages of a diaphragm compressor, this scheme also has corresponding defects. On the one hand, since the pressure of the regenerated hydrogen is relatively low (less than 0.05 MPaG), in order to mix the regenerated hydrogen and the gas-phase recovered hydrogen chloride, it is necessary to depressurize the gas-phase recovered hydrogen chloride to make the pressure of the gas-phase recovered hydrogen chloride close to that of the regenerated hydrogen. Therefore, the pressure of the gas-phase recovered hydrogen chloride will be wasted and the energy consumption will increase. On the other hand, due to the certain degree of fluctuation in the content of the gas-phase recovered hydrogen chloride and the regenerated hydrogen, it will also have an adverse impact on the normal operation of the reciprocating compressor.

[0006] Therefore, it is necessary to provide a recovery system for hydrogen chloride in polysilicon tail gas with excellent safety performance and energy conservation. Summary of the Invention

[0007] The present invention provides a recovery system for hydrogen chloride in polysilicon tail gas. This recovery system not only has excellent safety performance, but also can effectively save energy consumption and material consumption in the process of polysilicon tail gas recovery, reduce the production cost of tail gas recovery, and improve the competitiveness of enterprises.

[0008] The present invention provides a method for recovering hydrogen chloride in polysilicon tail gas, which is carried out using the above-mentioned recovery system. Therefore, this recovery method has the advantages of excellent safety performance, low energy consumption, and low material consumption, and is suitable for wide promotion and application.

[0009] The present invention provides a recovery system for hydrogen chloride in polysilicon tail gas, which includes a hydrogen chloride recovery absorption tower and a pressure pump;

[0010] The hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower is communicated with the hydrogen chloride recovery outlet of the tail gas hydrogen chloride stripping tower, and the inlet of the pressure pump is communicated with the hydrogen chloride-chlorosilane outlet of the hydrogen chloride recovery absorption tower;

[0011] The hydrogen chloride recovery absorption tower has an inlet for silicon tetrachloride.

[0012] The recovery system as described above, further includes a hydrogen chloride recovery stripping tower;

[0013] The outlet of the pressure pump is communicated with the hydrogen chloride-chlorosilane inlet of the hydrogen chloride recovery stripping tower.

[0014] The recovery system as described above, further includes a first heat exchanger;

[0015] The hydrogen chloride recovery outlet of the tail gas hydrogen chloride stripping tower is communicated with the hot medium inlet of the first heat exchanger, and the hydrogen outlet of the hydrogen chloride recovery absorption tower is communicated with the cold medium inlet of the first heat exchanger;

[0016] The hot medium outlet of the first heat exchanger is communicated with the hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower.

[0017] The recovery system as described above, wherein the silicon tetrachloride outlet of the rectification unit is communicated with the silicon tetrachloride inlet of the hydrogen chloride recovery absorption tower.

[0018] The recovery system as described above, further includes a second heat exchanger;

[0019] The outlet of the pressure pump is communicated with the cold medium inlet of the second heat exchanger, and silicon tetrachloride enters the second heat exchanger through the hot medium inlet of the second heat exchanger;

[0020] The hot medium outlet of the second heat exchanger is communicated with the silicon tetrachloride inlet of the hydrogen chloride recovery absorption tower.

[0021] The recovery system as described above, further includes a first cooler;

[0022] The hot medium inlet of the first cooler is communicated with the hot medium outlet of the second heat exchanger;

[0023] The hot medium outlet of the first cooler is communicated with the silicon tetrachloride inlet of the hydrogen chloride recovery absorption tower.

[0024] The recovery system as described above, further includes a third heat exchanger;

[0025] The hot medium inlet of the third heat exchanger is communicated with the chlorosilane outlet of the recovered hydrogen chloride stripping tower, and the cold medium inlet of the third heat exchanger is communicated with the cold medium outlet of the second heat exchanger;

[0026] The cold medium outlet of the third heat exchanger is communicated with the hydrogen chloride-chlorosilane inlet of the recovered hydrogen chloride stripping tower.

[0027] The recovery system as described above, wherein the absorption temperature of the recovered hydrogen chloride absorption tower is -30 to -40 °C, and the pressure is greater than or equal to 0.4 MPaG;

[0028] In the recovered hydrogen chloride absorption tower, the mass ratio of silicon tetrachloride absorption liquid to the recovered hydrogen chloride is (15 - 30):1.

[0029] The recovery system as described above, wherein the bottom temperature of the recovered hydrogen chloride stripping tower is 98 to 140 °C, and the pressure is greater than or equal to 0.7 MPaG.

[0030] The present invention also provides a method for recovering hydrogen chloride in polysilicon tail gas, wherein the above-described recovery system is used.

[0031] The recovery system for hydrogen chloride in polysilicon tail gas of the present invention adds a recovered hydrogen chloride absorption tower after the tail gas hydrogen chloride stripping tower, so that the recovered hydrogen chloride generated by the tail gas hydrogen chloride stripping tower is absorbed by the silicon tetrachloride solution in the recovered hydrogen chloride absorption tower to obtain a hydrogen chloride-chlorosilane solution. The formed hydrogen chloride-chlorosilane solution can be pressurized and withdrawn by a pressure pump, and the pressure pump can make the pressure of the hydrogen chloride-chlorosilane solution meet the pressure of the cold hydrogenation unit. The recovery system of the present invention uses the recovered hydrogen chloride absorption tower to separate the hydrogen in the recovered hydrogen chloride and convert the recovered hydrogen chloride into a liquid phase that can be pressurized and withdrawn by a pressure pump. Using a pressure pump to pressurize the liquid phase instead of a diaphragm compressor to pressurize the gas phase avoids the disadvantages of low reliability and stability of the diaphragm compressor, high safety risks and investment, and large maintenance workload. This recovery system not only has excellent safety performance, but also can effectively save energy consumption and material consumption in the process of recovering polysilicon tail gas, reduce the production cost of tail gas recovery, and improve the competitiveness of enterprises.

[0032] The method for recovering hydrogen chloride in polysilicon tail gas of the present invention is carried out using the above-described recovery system. Therefore, this recovery method has the advantages of excellent safety performance, low energy consumption, and low material consumption, and is suitable for wide promotion and application. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of a polysilicon tail gas recovery process in the prior art;

[0034] Figure 2 It is a schematic diagram of a polysilicon tail gas recovery system in the prior art;

[0035] Figure 3 Schematic diagram of the hydrogen chloride recovery system in the polysilicon tail gas in the first embodiment of the present invention;

[0036] Figure 4 Schematic diagram of the hydrogen chloride recovery system in the polysilicon tail gas in the second embodiment of the present invention.

[0037] Description of the reference numerals:

[0038] 1: Tail gas hydrogen chloride absorption tower;

[0039] 2: Tail gas hydrogen chloride stripping tower;

[0040] 3: Recovered hydrogen chloride absorption tower;

[0041] 4: Pressure pump;

[0042] 5: First heat exchanger;

[0043] 6: Second heat exchanger;

[0044] 7: First cooler;

[0045] 8: Second cooler;

[0046] 9: Third cooler;

[0047] 10: Fourth cooler;

[0048] 11: Recovered hydrogen chloride stripping tower;

[0049] 12: Third heat exchanger;

[0050] 13: First condenser;

[0051] 14: Fourth heat exchanger;

[0052] 15: Return pump;

[0053] 16: Second condenser;

[0054] 17: Third condenser;

[0055] 18: Return tank;

[0056] 19: Reboiler. Detailed implementation manners

[0057] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0058] Figure 3 It is a schematic diagram of a hydrogen chloride recovery system in the tail gas of polysilicon in the first embodiment of the present invention; Figure 4 It is a schematic diagram of a hydrogen chloride recovery system in the tail gas of polysilicon in the second embodiment of the present invention. As Figure 3-4 shown, a first aspect of the present invention provides a hydrogen chloride recovery system in the tail gas of polysilicon, including a hydrogen chloride recovery absorption tower 3 and a pressure pump 4;

[0059] The hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower 3 is communicated with the hydrogen chloride recovery outlet of the tail gas hydrogen chloride analysis tower 2, and the inlet of the pressure pump 4 is communicated with the hydrogen chloride-chlorosilane outlet of the hydrogen chloride recovery absorption tower 3;

[0060] The hydrogen chloride recovery absorption tower 3 has a silicon tetrachloride inlet.

[0061] In a specific embodiment, the polysilicon tail gas can obtain recovered hydrogen chloride through a tail gas condensation unit, a hydrogen compression unit, a tail gas hydrogen chloride absorption tower 1, and a tail gas hydrogen chloride analysis tower 2 in sequence. The recovered hydrogen chloride mainly includes hydrogen chloride, and also includes a small amount of hydrogen and a small amount of dichlorosilane (dichlorodisilane).

[0062] In the present invention, the recovered hydrogen chloride generated by the tail gas hydrogen chloride stripping tower 2 is output through the recovered hydrogen chloride outlet of the tail gas hydrogen chloride stripping tower 2 and enters the recovered hydrogen chloride absorption tower 3 through the recovered hydrogen chloride inlet of the recovered hydrogen chloride absorption tower 3, and the silicon tetrachloride enters the recovered hydrogen chloride absorption tower 3 through the silicon tetrachloride inlet of the recovered hydrogen chloride absorption tower 3. Since there are differences in the solubility of hydrogen chloride, hydrogen, and dichlorosilane in the recovered hydrogen chloride in silicon tetrachloride (hydrogen chloride and dichlorosilane are soluble in silicon tetrachloride, and hydrogen is insoluble in silicon tetrachloride), in the recovered hydrogen chloride absorption tower 3, silicon tetrachloride will absorb hydrogen chloride and dichlorosilane in the recovered hydrogen chloride to obtain a hydrogen chloride-chlorosilane solution (containing hydrogen chloride, silicon tetrachloride, and dichlorosilane) and hydrogen. The generated hydrogen can be output through the hydrogen outlet of the recovered hydrogen chloride absorption tower 3; the generated hydrogen chloride-chlorosilane solution can be output through the hydrogen chloride-chlorosilane outlet of the recovered hydrogen chloride absorption tower 3 and enter the pressure pump 4 through the inlet of the pressure pump 4. The pressure pump 4 pressurizes the hydrogen chloride-chlorosilane solution to make the pressure of the hydrogen chloride-chlorosilane solution meet the operating pressure of the downstream process, and then transports the hydrogen chloride-chlorosilane solution to the downstream process for recycling. For example, the pressure pump 4 can be used to pressurize the hydrogen chloride-chlorosilane solution to make the pressure of the hydrogen chloride-chlorosilane solution meet the operating pressure of the cold hydrogenation unit, and then transport the hydrogen chloride-chlorosilane solution to the cold hydrogenation unit.

[0063] In the present invention, the pressure pump 4 can be selected according to the pressure and temperature of the hydrogen chloride-chlorosilane solution. In some embodiments, in order to reduce energy consumption, improve reliability, simplify operation steps, and save daily maintenance costs, the pressure pump 4 can be a canned motor pump or a magnetic pump.

[0064] In the method for recovering hydrogen chloride from the polysilicon tail gas of the present invention, the recovered hydrogen chloride absorption tower 3 is used to absorb and process the recovered hydrogen chloride to obtain a hydrogen chloride-chlorosilane solution, and then the pressure pump 4 is used to pressurize and extract the hydrogen chloride-chlorosilane solution, and the liquid-phase pressurization energy consumption is low; at the same time, the reliability and stability of the recovered hydrogen chloride absorption tower 3 and the pressure pump 4 are excellent, which can reduce the investment in pipelines and their accessories and save costs. It is worth mentioning that the present invention uses the recovered hydrogen chloride absorption tower 3 with silicon tetrachloride as the absorbent to absorb and process the recovered hydrogen chloride, which can separate the hydrogen in the recovered hydrogen chloride without introducing new media, greatly reduce the hydrogen content in the recovered hydrogen chloride, obtain a hydrogen chloride-chlorosilane solution almost free of hydrogen, and the obtained hydrogen chloride-chlorosilane solution better meets the requirements of the downstream process. Moreover, the obtained hydrogen can also be transported to the downstream process, significantly saving production costs.

[0065] The hydrogen chloride recovery system of the present invention can achieve 100% utilization of various materials in the polysilicon tail gas, reduce material losses, and improve economic benefits. The purity of the hydrogen gas output from the hydrogen chloride recovery absorption tower 3 of the present invention is greater than 99.75% (mol), and the recovery rate of hydrogen gas by the hydrogen chloride recovery absorption tower 3 is 97%.

[0066] In the present invention, the hydrogen chloride-chlorosilane solution can be separated according to the requirements of the downstream process to obtain high-purity hydrogen chloride. As Figure 4 shown, in some embodiments of the present invention, the recovery system of the present invention further includes a hydrogen chloride recovery stripping tower 11;

[0067] The outlet of the pressure pump 4 is communicated with the hydrogen chloride-chlorosilane inlet of the hydrogen chloride recovery stripping tower 11.

[0068] Specifically, in the present invention, the hydrogen chloride-chlorosilane solution is output from the outlet of the pressure pump 4 and enters the hydrogen chloride recovery stripping tower 11 through the hydrogen chloride-chlorosilane inlet of the hydrogen chloride recovery stripping tower 11. In the hydrogen chloride recovery stripping tower 11, the hydrogen chloride-chlorosilane solution will be separated to obtain high-purity hydrogen chloride (without hydrogen gas and dichlorosilane) and chlorosilane. The obtained high-purity hydrogen chloride can be output through the hydrogen chloride outlet of the hydrogen chloride recovery stripping tower 11, and the obtained chlorosilane solution can enter the rectification unit. Since the chlorosilane solution does not contain hydrogen chloride, it can reduce the impact on the downstream device and reduce the losses of device energy consumption and material consumption.

[0069] The purity of the hydrogen chloride output from the hydrogen chloride recovery stripping tower 11 of the present invention is greater than 98.8% (mol), and the recovery rate of hydrogen chloride is 100%; trace hydrogen chloride detection and trace hydrogen gas detection are carried out on the chlorosilane output from the hydrogen chloride recovery stripping tower 11, and no trace hydrogen chloride is detected and no trace hydrogen gas is detected.

[0070] In the present invention, the pressure of the hydrogen chloride-chlorosilane solution can be adjusted by the pressure pump 4, and then the pressure of the high-purity hydrogen chloride obtained after the hydrogen chloride recovery stripping tower 11 can be adjusted to make the pressure of the high-purity hydrogen chloride more in line with the requirements of the downstream process.

[0071] In the present invention, the flow rate of the non-condensable hydrogen gas at the top of the hydrogen chloride recovery absorption tower 3 can be adjusted according to the top pressure of the hydrogen chloride recovery absorption tower 3 to maintain the stability of the recovery system. The flow rate of the hydrogen chloride-chlorosilane solution can also be adjusted by the liquid level of the bottom of the hydrogen chloride recovery absorption tower 3, and then the stability of the recovery system can be maintained. The flow rate of the high-purity hydrogen chloride at the top outlet can be adjusted according to the top pressure of the hydrogen chloride recovery stripping tower 11 to maintain the stability of the hydrogen chloride stripping system.

[0072] As Figure 3-4 shown, in some embodiments of the present invention, the recovery system of the present invention further includes a first heat exchanger 5;

[0073] The hydrogen chloride recovery outlet of the tail gas hydrogen chloride stripping tower 2 is communicated with the hot medium inlet of the first heat exchanger 5, and the hydrogen outlet of the hydrogen chloride recovery absorption tower 3 is communicated with the cold medium inlet of the first heat exchanger 5;

[0074] The hot medium outlet of the first heat exchanger 5 is communicated with the hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower 3.

[0075] Specifically, the recovered hydrogen chloride is output from the outlet of the tail gas hydrogen chloride stripping tower 2, enters the first heat exchanger 5 through the hot medium inlet of the first heat exchanger 5, the hydrogen is output from the hydrogen outlet of the hydrogen chloride recovery absorption tower 3, enters the first heat exchanger through the cold medium inlet of the first heat exchanger 5. After the hydrogen and the recovered hydrogen chloride exchange heat in the first heat exchanger 5, the cooled recovered hydrogen chloride is output from the hot medium outlet of the first heat exchanger 5, and enters the hydrogen chloride recovery absorption tower 3 through the hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower 3, while the hydrogen can be output from the cold medium outlet of the first heat exchanger 5.

[0076] In the present invention, the material with a higher temperature in the heat exchanger is called the hot medium, and the material with a lower temperature is called the cold medium. For example, among the two materials of hydrogen and recovered hydrogen chloride, the temperature of hydrogen is lower, so hydrogen is the cold medium, and the temperature of the recovered hydrogen chloride is higher, so the recovered hydrogen chloride is the hot medium.

[0077] The present invention enables the hydrogen generated by the hydrogen chloride recovery absorption tower 3 to exchange heat with the recovered hydrogen chloride generated by the tail gas hydrogen chloride stripping tower 2 in the first heat exchanger 5, uses the cold energy of hydrogen to cool the recovered hydrogen chloride, and can make the temperature of the recovered hydrogen chloride more in line with the operating temperature of the hydrogen chloride recovery absorption tower 3 while saving energy consumption, and improves the absorption efficiency of the hydrogen chloride recovery absorption tower 3.

[0078] Further, as Figure 3As shown, in order to make the temperature of the recovered hydrogen chloride more in line with the operating temperature of the recovered hydrogen chloride absorption tower 3, the recovery system of the present invention may further include: a second cooler 8, a third cooler 9, and a fourth cooler 10; the recovered hydrogen chloride is output from the recovered hydrogen chloride outlet of the tail gas hydrogen chloride stripping tower 2, enters the second cooler 8 through the gas phase inlet of the second cooler 8, the liquid phase obtained by condensation in the second cooler 8 is output from the liquid phase outlet of the second cooler 8 and refluxed to the tail gas hydrogen chloride stripping tower 2, and the cooled gas phase is output from the gas phase outlet of the second cooler 8; enters the third cooler 9 through the gas phase inlet of the third cooler 9, the liquid phase obtained by condensation in the third cooler 9 is output from the liquid phase outlet of the third cooler 9 and refluxed to the tail gas hydrogen chloride stripping tower 2, and the cooled gas phase enters the fourth cooler 10 through the gas phase inlet of the fourth cooler 10, the liquid phase obtained by condensation in the fourth cooler 10 is output from the liquid phase outlet of the fourth cooler 10 and refluxed to the tail gas hydrogen chloride stripping tower 2, and the cooled gas phase is output from the gas phase outlet of the fourth cooler 10 and enters the first heat exchanger 5 through the hot medium inlet of the first heat exchanger 5 to exchange heat with hydrogen.

[0079] In some embodiments of the present invention, the silicon tetrachloride outlet of the rectification unit is communicated with the silicon tetrachloride inlet of the recovered hydrogen chloride absorption tower 3.

[0080] It can be understood that a conventional polysilicon process system includes a rectification unit for separating a chlorosilane mixture. Therefore, the silicon tetrachloride outlet of the rectification unit can be communicated with the silicon tetrachloride inlet of the recovered hydrogen chloride absorption tower 3, and the recovered silicon tetrachloride of the rectification unit is used as the absorbent of the recovered hydrogen chloride absorption tower 3, which can realize the recycling of materials and improve economic benefits.

[0081] As Figure 3-4 As shown, in some embodiments of the present invention, the recovery system for hydrogen chloride in polysilicon tail gas further includes a second heat exchanger 6;

[0082] The outlet of the pressure pump 4 is communicated with the cold medium inlet of the second heat exchanger 6, and the silicon tetrachloride enters the second heat exchanger 6 through the hot medium inlet of the second heat exchanger 6;

[0083] The hot medium outlet of the second heat exchanger 6 is communicated with the silicon tetrachloride inlet of the recovered hydrogen chloride absorption tower 3.

[0084] Specifically, the hydrogen chloride-chlorosilane solution is output from the outlet of the pressure pump 4 and enters the second heat exchanger 6 through the cold medium outlet of the second heat exchanger 6. The silicon tetrachloride enters the second heat exchanger 6 through the hot medium inlet of the second heat exchanger 6. In the second heat exchanger 6, the hydrogen chloride-chlorosilane solution exchanges heat with the silicon tetrachloride (using the cold energy of the hydrogen chloride-chlorosilane solution to cool the silicon tetrachloride and using the silicon tetrachloride to heat the hydrogen chloride-chlorosilane solution). The heated hydrogen chloride-chlorosilane solution can enter the downstream process through the cold medium outlet of the second heat exchanger 6 (for example, the cold hydrogenation unit or the recovered hydrogen chloride stripping tower 11). The cooled silicon tetrachloride can be output from the hot medium outlet of the second heat exchanger 6 and enter the recovered hydrogen chloride absorption tower 3 through the silicon tetrachloride inlet of the recovered hydrogen chloride absorption tower 3.

[0085] In the present invention, by using the cold energy of the hydrogen chloride-chlorosilane solution to cool the silicon tetrachloride and using the silicon tetrachloride to heat the hydrogen chloride-chlorosilane solution, the temperature of the silicon tetrachloride can be made more in line with the operating temperature of the recovered hydrogen chloride absorption tower 3 while saving energy consumption, improving the efficiency of the recovered hydrogen chloride absorption tower 3, making the temperature of the hydrogen chloride-chlorosilane solution more in line with the operating temperature of the downstream process, and improving the efficiency of the downstream process.

[0086] It can be understood that if the silicon tetrachloride is from the rectification unit, the silicon tetrachloride outlet of the rectification unit can be connected to the hot medium inlet of the second heat exchanger 6.

[0087] Furthermore, as Figure 3-4 shown, in order to make the temperature of the silicon tetrachloride more in line with the operating temperature of the recovered hydrogen chloride absorption tower 3, the recovery system of the present invention may further include a first cooler 7; the silicon tetrachloride cooled by the second heat exchanger 6 can be output from the hot medium outlet of the second heat exchanger 6 and enter the first cooler 7 through the cooling material inlet of the first cooler 7. After being cooled by the first cooler 7, it is output from the cooling material outlet of the first cooler 7 and enters the recovered hydrogen chloride absorption tower 3 through the silicon tetrachloride inlet of the recovered hydrogen chloride absorption tower 3.

[0088] As Figure 4 shown, in some embodiments of the present invention, the recovery system for hydrogen chloride in the polysilicon tail gas further includes a third heat exchanger 12;

[0089] The hot medium inlet of the third heat exchanger 12 is connected to the chlorosilane outlet of the recovered hydrogen chloride stripping tower 11, and the cold medium inlet of the third heat exchanger 12 is connected to the cold medium outlet of the second heat exchanger 6;

[0090] The cold medium outlet of the third heat exchanger 12 is connected to the hydrogen chloride-chlorosilane inlet of the recovered hydrogen chloride stripping tower 11.

[0091] Specifically, the hydrogen chloride - chlorosilane solution is output from the cold medium outlet of the second heat exchanger 6 and enters the third heat exchanger 12 through the cold medium inlet of the third heat exchanger 12. The chlorosilane (including silicon tetrachloride and a small amount of dichlorosilane) is output from the chlorosilane outlet of the hydrogen chloride recovery and desorption tower 11 and enters the third heat exchanger 12 through the hot medium inlet of the third heat exchanger 12. In the third heat exchanger 12, the chlorosilane will exchange heat with the hydrogen chloride - chlorosilane solution (using the heat of the chlorosilane to heat the hydrogen chloride - chlorosilane solution). The heated hydrogen chloride - chlorosilane solution can be output from the cold medium outlet of the third heat exchanger 12 and enter the hydrogen chloride recovery and desorption tower 11 through the hydrogen chloride - chlorosilane inlet of the hydrogen chloride recovery and desorption tower 11. By using the heat of the chlorosilane produced by the hydrogen chloride recovery and desorption tower 11 to heat the hydrogen chloride - chlorosilane solution, the present invention can make the temperature of the hydrogen chloride - chlorosilane solution more in line with the operating temperature of the hydrogen chloride recovery and desorption tower 11 and improve the efficiency of the hydrogen chloride recovery and desorption tower 11 while saving energy consumption.

[0092] Furthermore, it also includes the condensation and heat exchange treatment of hydrogen chloride. Hydrogen chloride cools and condenses during the condensation and heat exchange treatment. The liquid phase obtained by condensation is mainly chlorosilane, and the chlorosilane obtained by condensation can be returned to enter the hydrogen chloride recovery and desorption tower 11. The uncondensed gas phase is highly pure hydrogen chloride, which can be sent to the cold hydro - chlorination unit to participate in the cold hydro - chlorination reaction, or sent to the slurry treatment unit to participate in the high - boiling cracking reaction, or sent to the trichlorosilane synthesis unit to participate in the synthesis reaction.

[0093] As Figure 4 shown, in some embodiments of the present invention, the hydrogen chloride recovery system in the polysilicon tail gas further includes a first condenser 13, a reflux pump 15, a second condenser 16, a third condenser 17, and a reflux drum 18. Among them, the hydrogen chloride generated by the hydrogen chloride recovery and desorption tower 11 is output from the gas phase outlet of the hydrogen chloride recovery and desorption tower 11 and enters the first condenser 13 through the gas phase inlet of the first condenser 13. The hydrogen chloride gas is partially condensed in the first condenser 13, and the condensed liquid phase enters the reflux drum 18. The uncondensed hydrogen chloride gas enters the second condenser 16 through the gas phase inlet of the second condenser 16, and the hydrogen chloride condensed into a liquid phase in the second condenser 16 enters the reflux drum 18. The uncondensed hydrogen chloride gas can be output from the gas phase outlet of the second condenser 16 and enter the third condenser 17 through the gas phase inlet of the third condenser 17. The hydrogen chloride condensed into a liquid phase in the third condenser 17 enters the reflux drum 18, and the uncondensed hydrogen chloride gas can be output from the gas phase outlet of the third condenser 17 to the downstream process unit. The reflux pump 15 can pressurize the liquid - phase hydrogen chloride in the reflux drum 18 and send it to the top of the hydrogen chloride recovery and desorption tower 11 as reflux liquid.

[0094] In some embodiments of the present invention, the hydrogen chloride recovery system in the polysilicon tail gas further includes a fourth heat exchanger 14;

[0095] The hydrogen chloride outlet of the hydrogen chloride recovery stripping column 11 is communicated with the hot medium inlet of the fourth heat exchanger 14. In the fourth heat exchanger 14, a part of the hydrogen chloride gas is condensed into a liquid phase. The liquid phase outlet of the fourth heat exchanger 14 is communicated with the inlet of the reflux drum 18, and the hot medium gas phase outlet of the fourth heat exchanger 14 is communicated with the gas phase inlet of the second condenser 16; the cold medium gas phase inlet of the fourth heat exchanger 14 is communicated with the gas phase outlet of the third condenser 17, and the cold medium gas phase outlet of the fourth heat exchanger 14 is communicated with the inlet of the downstream process unit.

[0096] The present invention can utilize the cold energy of the low-temperature high-purity hydrogen chloride extracted from the top of the hydrogen chloride recovery stripping column 11, which helps to further save energy consumption.

[0097] In the present invention, the process parameters of the hydrogen chloride recovery absorption column 3 and the hydrogen chloride recovery stripping column 11 can be further selected to improve the safety performance and efficiency of the hydrogen chloride recovery absorption column 3 and the hydrogen chloride recovery stripping column 11.

[0098] In some embodiments of the present invention, the absorption temperature of the hydrogen chloride recovery absorption column 3 is -30 to -40 °C, and the pressure is greater than or equal to 0.4 MPaG;

[0099] The bottom temperature of the hydrogen chloride recovery stripping column 11 is 98 to 140 °C, and the pressure is greater than or equal to 0.7 MPaG;

[0100] In the hydrogen chloride recovery absorption column 3, when the mass ratio of the silicon tetrachloride absorption liquid to the recovered hydrogen chloride is (15 - 30):1, the hydrogen chloride recovery absorption column 3 and the hydrogen chloride recovery stripping column 11 have more excellent safety performance and working efficiency.

[0101] The second aspect of the present invention provides a method for recovering hydrogen chloride from the above-mentioned polycrystalline silicon tail gas, which is carried out using the above-mentioned recovery system. Since this recovery method is carried out using the above-mentioned recovery system, this recovery method has the advantages of excellent safety performance, low energy consumption and low material consumption, and is suitable for wide promotion and application.

[0102] Hereinafter, the solution of the present invention will be further described in conjunction with specific embodiments.

[0103] Example 1

[0104] The recovery system for hydrogen chloride in the polycrystalline silicon tail gas of this example is as Figure 4 shown, including:

[0105] A hydrogen chloride recovery absorption column 3, a pressure pump 4 (canned motor pump), a first heat exchanger 5, a second heat exchanger 6, and a first cooler 7;

[0106] The recovered hydrogen chloride outlet of the tail gas hydrogen chloride stripping tower 2 is communicated with the hot medium inlet of the first heat exchanger 5, and the hydrogen outlet of the recovered hydrogen chloride absorption tower 3 is communicated with the cold medium inlet of the first heat exchanger 5; the hot medium outlet of the first heat exchanger 5 is communicated with the recovered hydrogen chloride inlet of the recovered hydrogen chloride absorption tower 3;

[0107] The recovered hydrogen chloride inlet of the recovered hydrogen chloride absorption tower 3 is communicated with the hot medium outlet of the first heat exchanger 5, and the inlet of the pressure pump 4 is communicated with the hydrogen chloride-chlorosilane outlet of the recovered hydrogen chloride absorption tower 3;

[0108] The outlet of the pressure pump 4 is communicated with the cold medium inlet of the second heat exchanger 6, and the silicon tetrachloride outlet of the rectification unit is communicated with the hot medium inlet of the second heat exchanger 6;

[0109] The hot medium inlet of the first cooler 7 is communicated with the hot medium outlet of the second heat exchanger 6;

[0110] The hot medium outlet of the first cooler 7 is communicated with the silicon tetrachloride inlet of the recovered hydrogen chloride absorption tower 3.

[0111] The method for recovering hydrogen chloride in the polysilicon tail gas of this embodiment is carried out using the above recovery system, including:

[0112] The recovered hydrogen chloride is output through the recovered hydrogen chloride outlet of the tail gas hydrogen chloride stripping tower 2, enters the first heat exchanger 5 through the hot medium inlet of the first heat exchanger 5, and the hydrogen generated by the recovered hydrogen chloride absorption tower 3 is output through the hydrogen outlet of the recovered hydrogen chloride absorption tower 3 and enters the first heat exchanger 5 through the cold medium inlet of the first heat exchanger 5. In the first heat exchanger 5, the hydrogen will cool down the recovered hydrogen chloride;

[0113] The cooled recovered hydrogen chloride is output through the hot medium outlet of the first heat exchanger 5, enters the recovered hydrogen chloride absorption tower 3 through the recovered hydrogen chloride inlet of the recovered hydrogen chloride absorption tower 3. The hydrogen chloride in the recovered hydrogen chloride will be absorbed by the chlorosilane in the recovered hydrogen chloride absorption tower 3 to obtain a hydrogen chloride-chlorosilane solution. The hydrogen chloride-chlorosilane solution is output through the hydrogen chloride-chlorosilane outlet of the recovered hydrogen chloride absorption tower 3 and enters the pressure pump through the inlet of the pressure pump 4;

[0114] After being pressurized by the pressure pump 4, the hydrogen chloride-chlorosilane solution enters the second heat exchanger 6 through the cold medium inlet of the second heat exchanger 6, and the silicon tetrachloride produced by the rectification unit enters the second heat exchanger 6 through the hot medium inlet of the second heat exchanger 6. In the second heat exchanger 6, the hydrogen chloride-chlorosilane solution will cool down the silicon tetrachloride, and the hydrogen chloride-chlorosilane solution will be heated by the silicon tetrachloride. The heated hydrogen chloride-chlorosilane solution is output through the cold medium outlet of the second heat exchanger 6 and enters the downstream process;

[0115] The temperature-reduced silicon tetrachloride is output from the hot medium outlet of the second heat exchanger 6, enters the first cooler 7 through the hot medium inlet of the first cooler 7, is cooled in the first cooler 7, and then is output from the hot medium outlet of the first cooler 7 and enters the hydrogen chloride recovery absorption tower 3 through the silicon tetrachloride inlet of the hydrogen chloride recovery absorption tower 3;

[0116] Among them, the absorption temperature of the hydrogen chloride recovery absorption tower 3 is -35°C, and the pressure is 0.48 MPaG;

[0117] In the hydrogen chloride recovery absorption tower 3, the mass ratio of the silicon tetrachloride absorption liquid to the recovered hydrogen chloride is 23.2:1.

[0118] In this embodiment, the recovery rate of hydrogen chloride by the hydrogen chloride recovery absorption tower 3 is 100%; calculated based on the amount of recovered hydrogen chloride being 1000 Nm 3 / h, and considering the usage amount of the absorption liquid silicon tetrachloride, the power of the pressure pump 4 in this embodiment is not higher than 5 kW. In the prior art, the power of the diaphragm compressor is 58 kW. Therefore, this embodiment can reduce energy consumption.

[0119] And compared with the prior art, the pressure pump 4 (canned motor pump) in this embodiment has excellent reliability and safety, and can solve the drawbacks such as frequent maintenance, high maintenance requirements, and difficulty in ensuring inherent safety of the diaphragm compressor.

[0120] Embodiment 2

[0121] The hydrogen chloride recovery system in the polysilicon tail gas of this embodiment is basically the same as the recovery system in Embodiment 1. The difference is that, as Figure 4 shown, it further includes: a hydrogen chloride recovery stripping tower 11, a third heat exchanger 12, a reboiler 19, a first condenser 13, a fourth heat exchanger 14, a second condenser 16, a third condenser 17, a reflux drum 18, and a reflux pump 15;

[0122] The hot medium inlet of the third heat exchanger 12 is communicated with the chlorosilane outlet of the hydrogen chloride recovery stripping tower 11, and the cold medium inlet of the third heat exchanger 12 is communicated with the cold medium outlet of the second heat exchanger 6;

[0123] The cold medium outlet of the third heat exchanger 12 is communicated with the hydrogen chloride-chlorosilane inlet of the hydrogen chloride recovery stripping tower 11, and the hot medium outlet of the third heat exchanger 12 is communicated with the downstream process unit inlet;

[0124] The chlorosilane outlet of the hydrogen chloride recovery stripping tower 11 is communicated with the inlet of the reboiler 19, and the reboiler 19 provides heat for the hydrogen chloride recovery stripping tower 11;

[0125] The hydrogen chloride outlet of the hydrogen chloride recovery stripper 11 is communicated with the gas phase inlet of the first condenser 13. The gas phase outlet of the first condenser 13 is communicated with the hot medium inlet of the fourth heat exchanger 14. The hot medium gas phase outlet of the fourth heat exchanger 14 is communicated with the gas phase inlet of the second condenser 16. The gas phase outlet of the second condenser 16 is communicated with the gas phase inlet of the third condenser 17. The gas phase outlet of the third condenser 17 is communicated with the cold medium inlet of the fourth heat exchanger 14. The cold medium outlet of the fourth heat exchanger 14 is communicated with the inlet of the downstream process unit;

[0126] The hot medium liquid phase outlet of the fourth heat exchanger 14, the liquid phase outlet of the second condenser 16, and the liquid phase outlet of the third condenser 17 are respectively communicated with the inlet of the reflux drum 18;

[0127] The outlet of the reflux drum 18 is communicated with the inlet of the reflux pump 15. The reflux pump 15 pressurizes the liquid phase hydrogen chloride to provide the top reflux liquid for the hydrogen chloride recovery stripper 11.

[0128] The method for recovering hydrogen chloride in the polysilicon tail gas of this embodiment is basically the same as the recovery method in Embodiment 1, except that the recovery system in Embodiment 2 is used for:

[0129] The heated hydrogen chloride-chlorosilane solution is output from the cold medium outlet of the second heat exchanger 6, enters the third heat exchanger 12 through the cold medium inlet of the third heat exchanger 12. A part of the chlorosilane solution generated by the hydrogen chloride recovery stripper 11 is output from the chlorosilane outlet of the hydrogen chloride recovery stripper 11, enters the third heat exchanger 12 through the hot medium inlet of the third heat exchanger 12. In the third heat exchanger 12, the chlorosilane and the hydrogen chloride-chlorosilane solution perform heat and cold exchange to further increase the temperature of the hydrogen chloride-chlorosilane solution;

[0130] The further heated hydrogen chloride-chlorosilane solution is output from the cold medium outlet of the third heat exchanger 12, enters the hydrogen chloride recovery stripper 11 through the hydrogen chloride-chlorosilane inlet of the hydrogen chloride recovery stripper 11. The hydrogen chloride-chlorosilane solution is stripped in the hydrogen chloride recovery stripper 11 to obtain a chlorosilane solution and hydrogen chloride gas;

[0131] Another part of the chlorosilane solution generated by the hydrogen chloride recovery stripper 11 is output from the chlorosilane outlet of the hydrogen chloride recovery stripper 11, enters the reboiler 19 through the inlet of the reboiler 19, and provides heat for the hydrogen chloride recovery stripper 11 through the reboiler 19;

[0132] The hydrogen chloride generated by the hydrogen chloride stripping tower 11 is output through the hydrogen chloride outlet of the hydrogen chloride stripping tower 11, enters the first condenser 13 through the gas-phase inlet of the first condenser 13 for condensation, and then is output through the gas-phase outlet of the first condenser 13 and enters the fourth heat exchanger 14 through the hot medium gas-phase inlet of the fourth heat exchanger 14. In the fourth heat exchanger 14, the hydrogen chloride exchanges heat with high-purity hydrogen chloride. The high-purity hydrogen chloride produced at the cold medium outlet of the fourth heat exchanger 14 enters the downstream processes such as high-boiling cracking that require high-purity hydrogen chloride. The liquid-phase hydrogen chloride generated after heat exchange in the fourth heat exchanger 14 is output through the liquid-phase outlet of the fourth heat exchanger 14 and enters the reflux drum 18;

[0133] The hydrogen chloride output through the hot medium gas-phase outlet of the fourth heat exchanger 14 enters the second condenser 16 through the gas-phase inlet of the second condenser 16. After condensation in the second condenser 16, the generated liquid-phase hydrogen chloride is output through the liquid-phase outlet of the second condenser 16 and enters the reflux drum 18;

[0134] The gaseous hydrogen chloride generated by the second condenser 16 is output through the gas-phase outlet of the second condenser 16, enters the third condenser 17 through the gas-phase inlet of the third condenser 17. After condensation in the third condenser 17, the generated liquid-phase hydrogen chloride is output through the liquid-phase outlet of the third condenser 17 and enters the reflux drum 18. The gaseous hydrogen chloride is output through the gas-phase outlet of the third condenser 17 and enters the fourth heat exchanger 14 through the cold medium inlet of the fourth heat exchanger 14;

[0135] The liquid-phase hydrogen chloride in the reflux drum 18 is output through the outlet of the reflux drum 18, enters the reflux pump 15 through the inlet of the reflux pump 15, and then returns to the hydrogen chloride stripping tower 11 under pressure by the reflux pump 15 as the top reflux liquid;

[0136] Among them, the bottom temperature of the hydrogen chloride stripping tower 11 is 139.3 °C and the pressure is 0.7 MPaG.

[0137] The purity of the hydrogen chloride generated by the hydrogen chloride stripping tower 11 in this embodiment is greater than 98.8% (mol), and the recovery rate of hydrogen chloride is 100%; trace hydrogen chloride detection and trace hydrogen detection are carried out on the chlorosilane output from the hydrogen chloride stripping tower 11, and no trace hydrogen chloride is detected and no trace hydrogen is detected.

[0138] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A recovery system for hydrogen chloride in polysilicon tail gas, characterized in that, it includes a hydrogen chloride recovery absorption tower, a pressure pump, a hydrogen chloride recovery stripping tower, a first heat exchanger, a second heat exchanger and a third heat exchanger; The hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower is communicated with the hydrogen chloride recovery outlet of the tail gas hydrogen chloride stripping tower, and the inlet of the pressure pump is communicated with the hydrogen chloride-chlorosilane outlet of the hydrogen chloride recovery absorption tower; The recovered hydrogen chloride includes hydrogen chloride, hydrogen and dichlorosilane; The hydrogen chloride recovery absorption tower has a silicon tetrachloride inlet, and the hydrogen chloride recovery absorption tower is used to absorb hydrogen chloride and dichlorosilane in the recovered hydrogen chloride through silicon tetrachloride to obtain a hydrogen chloride-chlorosilane solution; The outlet of the pressure pump is communicated with the hydrogen chloride-chlorosilane inlet of the hydrogen chloride recovery stripping tower; The hydrogen chloride recovery stripping tower is used to separate the hydrogen chloride-chlorosilane solution to obtain hydrogen chloride and chlorosilane; The hydrogen chloride recovery outlet of the tail gas hydrogen chloride stripping tower is communicated with the hot medium inlet of the first heat exchanger, and the hydrogen outlet of the hydrogen chloride recovery absorption tower is communicated with the cold medium inlet of the first heat exchanger; The hot medium outlet of the first heat exchanger is communicated with the hydrogen chloride recovery inlet of the hydrogen chloride recovery absorption tower; The outlet of the pressure pump is communicated with the cold medium inlet of the second heat exchanger, and silicon tetrachloride enters the second heat exchanger through the hot medium inlet of the second heat exchanger; The hot medium outlet of the second heat exchanger is communicated with the silicon tetrachloride inlet of the hydrogen chloride recovery absorption tower; The hot medium inlet of the third heat exchanger is communicated with the chlorosilane outlet of the hydrogen chloride recovery stripping tower, and the cold medium inlet of the third heat exchanger is communicated with the cold medium outlet of the second heat exchanger; The cold medium outlet of the third heat exchanger is communicated with the hydrogen chloride-chlorosilane inlet of the hydrogen chloride recovery stripping tower.

2. The recovery system according to claim 1, characterized in that, The silicon tetrachloride outlet of the rectification unit is communicated with the silicon tetrachloride inlet of the hydrogen chloride recovery absorption tower.

3. The recovery system according to claim 1, characterized in that, it further includes a first cooler; The hot medium inlet of the first cooler is communicated with the hot medium outlet of the second heat exchanger; The hot medium outlet of the first cooler is communicated with the silicon tetrachloride inlet of the hydrogen chloride recovery absorption tower.

4. The recovery system according to any one of claims 1-3, characterized in that, The absorption temperature of the hydrogen chloride recovery absorption tower is -30~-40°C, and the pressure is greater than or equal to 0.4MPaG; In the hydrogen chloride recovery absorption tower, the mass ratio of the silicon tetrachloride absorption liquid to the recovered hydrogen chloride is (15-30):

1.

5. The recovery system according to any one of claims 1-3, characterized in that, The bottom temperature of the hydrogen chloride recovery stripping tower is 98~140°C, and the pressure is greater than or equal to 0.7MPaG.

6. A method for recovering hydrogen chloride in polysilicon tail gas, characterized in that, it is carried out by using the recovery system according to any one of claims 1-5.

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