Separation method and separation system for hydrogen to be treated in polycrystalline silicon production

Abstract

The invention provides a separation method and a separation system for hydrogen to be treated in polycrystalline silicon production. The method for separating to-be-treated hydrogen in polycrystalline silicon production comprises the following steps: carrying out first absorption treatment on the to-be-treated hydrogen by using a chlorosilane barren solution to obtain a chlorosilane rich solution and intermediate hydrogen; and carrying out second absorption treatment on the intermediate hydrogen by using a silicon tetrachloride solution to obtain absorbed silicon tetrachloride and recovered hydrogen. According to the separation method, the content of chlorosilane in the hydrogen to be treated can be effectively reduced, so that the treatment load of a subsequent treatment unit is reduced, and the equipment investment is saved.

Description

Technical Field

[0001] The invention relates to a method and a system for separating hydrogen to be processed in polysilicon production, belonging to the technical field of chemical separation. Background Art

[0002] Polycrystalline silicon is a key material in the manufacture of integrated circuits, photovoltaic solar cells, and high-purity silicon products. With the rapid development of the electronic information industry and the solar photovoltaic industry, market demand for polycrystalline silicon continues to increase. Currently, the mainstream process for producing polycrystalline silicon is the modified Siemens process, in which industrial silicon reacts with silicon tetrachloride, hydrogen chloride, and hydrogen recovered from the reduction exhaust to produce trichlorosilane. The dust-removed mixed gas is condensed and recovered to separate hydrogen and a liquid mixture consisting of trichlorosilane produced by the reaction and unreacted silicon tetrachloride. The hydrogen is returned to the system to participate in the reaction again, and the liquid mixture is distilled to separate high-purity trichlorosilane (silicon tetrachloride is purified and then hydrogenated for recycling). The vaporized trichlorosilane and hydrogen are then mixed in a specific ratio and introduced into a polysilicon reduction furnace. A voltage is applied across the rod-shaped silicon core within the furnace, generating high temperatures. On the hot silicon core surface, the trichlorosilane is reduced by the hydrogen to elemental silicon, which is then deposited on the core surface, gradually producing polycrystalline silicon rods of the desired specifications. Only about 8-10% of the trichlorosilane entering the reduction furnace is converted into polysilicon. The reduction tail gas contains a large amount of unreacted raw materials: hydrogen (H2) and trichlorosilane (SiHCL3), as well as reaction byproducts such as silicon tetrachloride (SiCl4), hydrogen chloride (HCL), and dichlorosilane (SiH2Cl2). This process is then separated and recovered through a "dry process" in a tail gas recovery unit. The separated chlorosilanes are distilled and purified, the hydrogen is recycled back to the reduction furnace, and the hydrogen chloride is sent to the cold hydrogenation unit. This process achieves a completely closed-loop production process.

[0003] Existing tail gas recovery processes utilize dry recovery technology, which can essentially separate and recover all components in the tail gas without introducing new pollution sources. The recovered product maintains stable quality and is directly returned to the polysilicon production system for reuse. With the development of polysilicon technology, tail gas recovery processes have been continuously optimized and improved, but the contradiction between improving the quality of the recovered product and increasing energy consumption still exists. Figure 1 Schematic diagram of the polysilicon tail gas recovery process in the prior art, such as Figure 1As shown, the existing polysilicon tail gas recovery system includes tail gas condensation, hydrogen compression, hydrogen chloride absorption, hydrogen chloride decomposition and hydrogen adsorption processes. The reduction tail gas is condensed to initially separate hydrogen (containing hydrogen chloride and a small amount of chlorosilane) from chlorosilane (mainly trichlorosilane and silicon tetrachloride) gas and liquid; the condensed chlorosilane and the hydrogen chloride-rich chlorosilane (rich liquid) coming out of the hydrogen chloride absorption tower kettle enter the hydrogen chloride decomposition tower together, and the temperature is increased and the pressure is reduced in the hydrogen chloride decomposition tower to desorb hydrogen chloride. The hydrogen chloride produced at the top of the tower is recovered and sent to cold hydrogenation or trichlorosilane synthesis processes, and part of the chlorosilane (lean liquid) at the bottom of the tower is sent to the hydrogen chloride absorption tower as a hydrogen chloride absorbent, and part is sent to the hydrogen chloride absorption tower. The recovered product is sent to the polysilicon distillation unit; the non-condensable hydrogen after the tail gas is condensed is pressurized by a hydrogen compressor and sent to a hydrogen chloride absorption tower, where chlorosilane is used to absorb the hydrogen chloride in the hydrogen in a low-temperature and high-pressure environment. The hydrogen produced at the top of the hydrogen chloride absorption tower is further purified by a hydrogen adsorption tower to obtain purified hydrogen with a purity of 99.9999% for use in reduction and other devices; the chlorosilane waste liquid by-product of the regeneration process of the hydrogen adsorption tower is sent to the distillation unit for further treatment, and the regenerated hydrogen is sent to the cold hydrogenation unit as supplementary hydrogen.

[0004] However, in the existing tail gas recovery process, the hydrogen discharged from the top of the hydrogen chloride absorption tower contains a high content of chlorosilane (about 3% to 4% by weight). This results in a large processing load on the downstream hydrogen adsorption tower. It is necessary to increase the number of hydrogen adsorption towers, expand the size of the hydrogen adsorption towers, and increase the amount of activated carbon filled in the hydrogen adsorption towers to meet the processing requirements, which in turn increases the equipment investment. Summary of the Invention

[0005] The present invention provides a method for separating hydrogen to be processed in polysilicon production, which can effectively reduce the chlorosilane content in the hydrogen to be processed, thereby reducing the processing load of subsequent processing units (such as adsorption units) and saving equipment investment.

[0006] The present invention provides a separation system for implementing the above separation method, which can effectively reduce the content of chlorosilane in the hydrogen to be treated, effectively reduce the processing load of subsequent processing units, and reduce equipment investment.

[0007] The present invention provides a method for separating hydrogen to be processed in polysilicon production, which comprises:

[0008] Using the chlorosilane lean liquid to perform a first absorption treatment on the hydrogen to be treated to obtain a chlorosilane rich liquid and intermediate hydrogen;

[0009] The intermediate hydrogen is subjected to a second absorption treatment using a silicon tetrachloride solution to obtain absorbed silicon tetrachloride and recovered hydrogen.

[0010] In the separation method as described above, the silicon tetrachloride solution is obtained by subjecting recovered silicon tetrachloride to cryogenic treatment.

[0011] In the separation method as described above, the silicon tetrachloride solution is obtained by subjecting a mixed solution comprising a recovered silicon tetrachloride solution and a silicon tetrachloride absorption solution to cryogenic treatment.

[0012] The separation method as described above, wherein, before the cryogenic treatment, the method comprises: subjecting the absorbing silicon tetrachloride and the recovered silicon tetrachloride to heat exchange treatment.

[0013] The separation method as described above, wherein, in the first absorption treatment, the temperature is -65 to -60°C and the pressure is 0.8 to 1.5 MPaG; and / or,

[0014] In the second absorption treatment, the temperature is -65 to -50°C and the pressure is 0.8 to 1.5 MPaG; and / or,

[0015] The mass ratio of the recovered silicon tetrachloride to the hydrogen to be treated is (2-25):1.

[0016] The present invention provides a separation system for hydrogen to be processed in polysilicon production for implementing the separation method described above, wherein the system comprises a first absorption unit and a second absorption unit;

[0017] The first absorption unit has a chlorosilane lean solution inlet and a to-be-treated hydrogen inlet. The intermediate hydrogen outlet of the first absorption unit is connected to the intermediate hydrogen inlet of the second absorption unit. The second absorption unit has a silicon tetrachloride inlet.

[0018] The separation system as described above, wherein, further comprises a cryogenic cooler, wherein the heat source outlet of the cryogenic cooler is in communication with the silicon tetrachloride inlet.

[0019] The separation system as described above further includes a heat exchanger, wherein the silicon tetrachloride absorption outlet of the second absorption unit is connected to the cold source inlet of the heat exchanger, the recovered silicon tetrachloride enters the heat exchanger through the heat source inlet of the heat exchanger, and the heat source outlet of the heat exchanger is connected to the heat source inlet of the cryogenic refrigerator.

[0020] In the separation system as described above, the silicon tetrachloride absorption outlet of the second absorption unit and the heat source outlet of the heat exchanger are both connected to the heat source inlet of the cryogenic refrigerator.

[0021] The separation system as described above, wherein the first absorption unit and the second absorption unit are absorption towers respectively; or

[0022] The separation system is an absorption tower, which includes a first absorption unit and a second absorption unit connected to each other, wherein the second absorption unit is located on the top of the first absorption unit.

[0023] The present invention provides a method for separating unprocessed hydrogen in polysilicon production, comprising: performing a first absorption treatment on the unprocessed hydrogen using a chlorosilane-lean solution to obtain intermediate hydrogen; and performing a second absorption treatment on the intermediate hydrogen using a silicon tetrachloride solution to obtain recovered hydrogen. This separation method can reduce the chlorosilane content in the recovered hydrogen, thereby alleviating the processing load and reducing equipment investment in subsequent operating units.

[0024] The present invention provides a separation system for hydrogen to be processed in polysilicon production, which is used to implement the above-mentioned separation method. The separation system includes a first absorption unit and a second absorption unit connected in series. The separation system can not only reduce the chlorosilane content in the recovered hydrogen, thereby alleviating the processing load of subsequent operating units and reducing the equipment investment in subsequent operating units, but also the separation system has a simple structure and is suitable for wide promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0026] Figure 1 Schematic diagram of a polysilicon tail gas recovery process in the prior art;

[0027] Figure 2 Schematic diagram of a process for separating hydrogen to be processed in polysilicon production according to a first embodiment of the present invention;

[0028] Figure 3 Schematic diagram of a separation process for hydrogen to be processed in polysilicon production according to a second embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the separation process of hydrogen to be treated in polysilicon production according to the third embodiment of the present invention.

[0030] Description of reference numerals:

[0031] 1: first absorption unit;

[0032] 2: second absorption unit;

[0033] 3: heat exchanger;

[0034] 4: Deep freezer;

[0035] 5: Pressure pump. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Figure 2 Schematic diagram of a separation process for hydrogen to be processed in polysilicon production according to a first embodiment of the present invention; Figure 3 Schematic diagram of a separation process for hydrogen to be processed in polysilicon production according to a second embodiment of the present invention; Figure 4 FIG3 is a schematic diagram of a separation process for hydrogen to be processed in polysilicon production according to a third embodiment of the present invention. Figure 2-4 As shown, the first aspect of the present invention provides a method for separating hydrogen to be processed in polysilicon production, comprising:

[0038] Use chlorosilane lean solution to treat hydrogen ( Figure 2-4 The hydrogen in the solution is subjected to a first absorption treatment to obtain a chlorosilane-rich liquid and intermediate hydrogen;

[0039] The intermediate hydrogen is subjected to a second absorption treatment using a silicon tetrachloride solution to obtain absorbed silicon tetrachloride and recovered hydrogen.

[0040] In the present invention, the hydrogen to be treated refers to the tail gas after condensation treatment, which mainly includes hydrogen, hydrogen chloride and a small amount of chlorosilane; the chlorosilane-lean liquid does not include hydrogen chloride, and mainly includes trichlorosilane, silicon tetrachloride and dichlorosilane.

[0041] The separation method of the present invention specifically comprises: using chlorosilane-lean liquid to perform a first absorption treatment on the hydrogen to be treated, absorbing hydrogen chloride in the hydrogen to be treated, and obtaining a chlorosilane-rich liquid comprising hydrogen chloride, trichlorosilane, silicon tetrachloride and dichlorosilane, as well as intermediate hydrogen from which part of the hydrogen chloride has been removed; then using silicon tetrachloride solution to perform a second absorption treatment on the intermediate hydrogen. Since silicon tetrachloride has excellent mutual solubility with trichlorosilane and dichlorosilane, the silicon tetrachloride solution absorbs trichlorosilane, dichlorosilane and trichlorosilane in the intermediate hydrogen, thereby obtaining recovered hydrogen with a low chlorosilane content and absorbed silicon tetrachloride.

[0042] The present invention utilizes a silicon tetrachloride solution to perform a second absorption treatment on the intermediate hydrogen. Since silicon tetrachloride has a high mutual solubility with trichlorosilane and dichlorosilane, the contents of trichlorosilane and dichlorosilane in the intermediate hydrogen can be significantly reduced, and the content of hydrogen chloride in the intermediate hydrogen can also be reduced, thereby obtaining recovered hydrogen with a low chlorosilane content and a low hydrogen chloride content.

[0043] Compared with the prior art, the separation method of the present invention can reduce the surplus amount of absorption liquid, thereby saving this part of energy consumption and the investment in the expansion of corresponding equipment and pipelines; and the separation method of the present invention can significantly reduce the chlorosilane content in the recovered hydrogen (can be reduced to less than 1.2%wt, only one-third of the original solution), and the hydrogen chloride content in the recovered hydrogen is also significantly reduced (reduced by more than 25%); thereby significantly reducing the processing load of subsequent processing equipment (hydrogen adsorption tower) (the processing load of the hydrogen adsorption tower is reduced by more than 65%), reducing the number of subsequent processing equipment and the amount of activated carbon filling, reducing the investment in the corresponding water system and the consumption of refrigerant (circulating water or evaporative cooling) and steam; and because the chlorosilane content in the recovered hydrogen is relatively large compared to methane and methylsilane, The magnitude of the reduction is reduced, which has a favorable effect on the adsorption selectivity of the activated carbon in the subsequent processing equipment (hydrogen adsorption tower), thereby improving its adsorption capacity for methane and methylsilane, helping to obtain high-quality purified hydrogen, thereby reducing the impurity content in the high-purity silicon product and improving the quality of polysilicon; at the same time, since the chlorosilane components entrained in the recovered hydrogen are changed from the original trichlorosilane and dichlorodihydrosilane to silicon tetrachloride, when the desorption gas obtained after hydrogen adsorption is regenerated, the hydrogen is easier to condense and precipitate, and the amount of this part of chlorosilane is greatly reduced, thereby reducing the refrigerant consumption of the regeneration system; the number of hydrogen adsorption towers is reduced, and the gas processing volume of the regeneration system is also reduced, thereby reducing the investment in regeneration system equipment and pipelines, and reducing the energy consumption of the downstream processing of waste chlorosilane recovered by the regeneration system. It is worth mentioning that the separation method of the present invention uses silicon tetrachloride to absorb dichlorosilane, and the absorption products are mainly silicon tetrachloride and dichlorosilane, which is conducive to downstream processing. The product can be directly sent to the anti-disproportionation device for reaction (replacing the original silicon tetrachloride as the anti-disproportionation reaction raw material with dichlorosilane for anti-disproportionation reaction, anti-disproportionation reaction: SiCl4+SiH2Cl2=SiHCl3) and then distilled, or it can be directly sent to the cold hydrogenation device for silicon tetrachloride hydrogenation reaction (cold hydrogenation main reaction: 3SiCl4+Si+2H2=4SiHCl3). While improving the primary recovery rate of chlorosilane recovered from tail gas, it does not increase downstream energy consumption.

[0044] In some embodiments of the present invention, when the downstream destination is cold hydrogenation, the silicon tetrachloride solution is obtained by cryogenically treating the recovered silicon tetrachloride.

[0045] In the present invention, the recovered silicon tetrachloride can be a high-purity silicon tetrachloride solution from a distillation device (silicon tetrachloride content ≥99.5wt%, total metal impurities ≤20ppb). The present invention can perform a cryogenic treatment on the high-purity silicon tetrachloride from the distillation device to obtain a silicon tetrachloride solution at a suitable temperature, and then use the silicon tetrachloride solution to perform a second absorption treatment on the intermediate hydrogen, thereby obtaining absorbed silicon tetrachloride and recovered hydrogen.

[0046] The present invention performs cryogenic treatment on recovered silicon tetrachloride to obtain a silicon tetrachloride solution with a suitable temperature, promotes the second absorption treatment, and further obtains recovered hydrogen with higher purity and absorbed silicon tetrachloride, thereby improving the separation efficiency of the hydrogen to be treated.

[0047] In the present invention, considering that the amount of silicon tetrachloride required for deproportionation is less than the amount of silicon tetrachloride solution in the second absorption process, when the downstream destination is deproportionation, the absorbed silicon tetrachloride obtained in the second absorption process can be forcibly circulated to participate in the second absorption process to ensure the amount of silicon tetrachloride solution in the second absorption process, so that the second absorption process can proceed normally. For example, in some embodiments of the present invention, the silicon tetrachloride solution is obtained by cryogenically treating a mixed solution including recovered silicon tetrachloride and absorbed silicon tetrachloride.

[0048] Specifically, the absorbed silicon tetrachloride obtained by the second absorption treatment can be mixed with the recovered silicon tetrachloride to form a mixed liquid, and then the mixed liquid is cryogenically treated to obtain a silicon tetrachloride solution, and the silicon tetrachloride solution is used to perform the second absorption treatment on the intermediate hydrogen.

[0049] In some embodiments of the present invention, the method includes subjecting the absorbed silicon tetrachloride and the recovered silicon tetrachloride to heat exchange treatment before the cryogenic treatment.

[0050] Specifically, before the cryogenic treatment, the process includes: subjecting the absorbed silicon tetrachloride obtained in the second absorption treatment to a heat exchange treatment with the recovered silicon tetrachloride. During the heat exchange treatment, the temperature of the recovered silicon tetrachloride is reduced, while the temperature of the absorbed silicon tetrachloride is increased, and the cold energy is recycled and utilized, thereby further saving energy consumption (through the heat exchange treatment, about 95% of the cold energy in the absorbed silicon tetrachloride can be recovered).

[0051] The present invention can also select specific process parameters for the first absorption treatment and the second absorption treatment to further improve the treatment efficiency of the first absorption treatment and the second absorption treatment to obtain recovered hydrogen with higher purity. For example, in some embodiments of the present invention, in the first absorption treatment, the temperature is -65 to -60°C and the pressure is 0.8 to 1.5 MPaG; and / or,

[0052] In the second absorption treatment, the temperature is -65 to -50°C and the pressure is 0.8 to 1.5 MPaG.

[0053] The inventors found in their research that when the mass ratio of recovered silicon tetrachloride to hydrogen to be treated is (2-25):1, the second absorption treatment can be carried out more efficiently and fully, thereby improving the separation efficiency.

[0054] like Figure 2-3 As shown, the second aspect of the present invention provides a separation system for hydrogen to be treated in polysilicon production for implementing the separation method of the first aspect, comprising a first absorption unit 1 and a second absorption unit 2;

[0055] The first absorption unit 1 has a chlorosilane lean solution inlet and a hydrogen inlet to be treated. The intermediate hydrogen outlet of the first absorption unit 1 is connected to the intermediate hydrogen inlet of the second absorption unit 2. The second absorption unit 2 has a silicon tetrachloride inlet.

[0056] Specifically, the chlorosilane-lean liquid enters the first absorption unit 1 through the chlorosilane-lean liquid inlet of the first absorption unit 1, and the hydrogen to be treated enters the first absorption unit 1 through the hydrogen to be treated inlet of the first absorption unit 1. In the first absorption unit 1, the chlorosilane-lean liquid absorbs the hydrogen chloride in the hydrogen to be treated to obtain a chlorosilane-rich liquid including hydrogen chloride, trichlorosilane, silicon tetrachloride and dichlorodihydrogen silicon, as well as intermediate hydrogen from which part of the hydrogen chloride has been removed; the intermediate hydrogen is output through the intermediate hydrogen outlet of the first absorption unit 1 and enters the second absorption unit 2 through the intermediate hydrogen inlet of the second absorption unit 2. The silicon tetrachloride solution enters the second absorption unit 2 through the silicon tetrachloride inlet of the second absorption unit 2. In the second absorption unit 2, the silicon tetrachloride solution performs a second absorption treatment on the intermediate hydrogen, thereby obtaining recovered hydrogen with a low chlorosilane content and absorbed silicon tetrachloride.

[0057] The separation system for hydrogen to be processed in polysilicon production of the present invention can be used to implement the separation method of the first aspect. The separation system has a simple structure and is suitable for wide promotion and application.

[0058] The present invention does not specifically limit the specific structures of the first absorption unit 1 and the second absorption unit 2, as long as they can respectively perform the first absorption treatment and the second absorption treatment. Figure 2 and Figure 3 As shown, in some embodiments of the present invention, the first absorption unit 1 and the second absorption unit 2 are absorption towers respectively.

[0059] like Figure 4 As shown, in some embodiments of the present invention, the separation system is an absorption tower, which includes a first absorption unit 1 and a second absorption unit 2 connected to each other, and the second absorption unit 2 is located on the top of the first absorption unit 1.

[0060] In some embodiments, a partition plate and a gas distributor are provided between the second absorption unit 2 and the first absorption unit 1. The present invention can further save equipment investment by making one absorption tower include the second absorption unit 2 and the first absorption unit 1 connected to each other.

[0061] In some embodiments of the present invention, the separation system further comprises a cryogenic cooler 4, and the heat source outlet of the cryogenic cooler 4 is connected to the silicon tetrachloride inlet.

[0062] Specifically, the recovered silicon tetrachloride enters the cryogenic refrigerator 4 through the heat source inlet of the cryogenic refrigerator 4, is cryogenically treated in the cryogenic refrigerator 4, is output from the heat source outlet of the cryogenic refrigerator 4, and enters the second absorption unit 2 through the silicon tetrachloride inlet of the second absorption unit 2.

[0063] The present invention utilizes the cryogenic device 4 to perform cryogenic treatment on the recovered chlorosilane, thereby obtaining a silicon tetrachloride solution at a suitable temperature, promoting the second absorption treatment, and thus more efficiently obtaining recovered hydrogen with a higher purity.

[0064] In some embodiments of the present invention, the separation system further includes a heat exchanger 3, the silicon tetrachloride absorption outlet of the second absorption unit 2 is connected to the cold source inlet of the heat exchanger 3, the recovered silicon tetrachloride enters the heat exchanger 3 through the heat source inlet of the heat exchanger 3, and the heat source outlet of the heat exchanger 3 is connected to the heat source inlet of the cryogenic refrigerator 4.

[0065] Specifically, the absorbed silicon tetrachloride obtained in the second absorption treatment is output through the absorbed silicon tetrachloride outlet of the second absorption unit 2, enters the heat exchanger 3 through the cold source inlet of the heat exchanger 3, and the recovered silicon tetrachloride enters the heat exchanger 3 through the heat source inlet of the heat exchanger 3. In the heat exchanger 3, the absorbed silicon tetrachloride and the recovered silicon tetrachloride are subjected to heat exchange treatment to reduce the temperature of the recovered silicon tetrachloride. The recovered silicon tetrachloride after the temperature is reduced is output through the heat source outlet of the heat exchanger 3, and enters the cryogenic freezer 4 through the heat source inlet of the cryogenic freezer 4 for cryogenic treatment.

[0066] The present invention utilizes the absorbed silicon tetrachloride in the heat exchanger 3 to lower the temperature of recovered silicon tetrachloride, which can fully utilize the cooling capacity of the absorbed silicon tetrachloride and save energy.

[0067] In some embodiments of the present invention, the silicon tetrachloride absorption outlet of the second absorption unit 2 and the heat source outlet of the heat exchanger 3 are both connected to the heat source inlet of the cryogenic refrigerator 4 .

[0068] Specifically, the absorbed silicon tetrachloride obtained by the second absorption treatment can be output through the absorbed silicon tetrachloride outlet and enter the cryogenic refrigerator 4 through the heat source inlet of the cryogenic refrigerator 4, and the recovered silicon tetrachloride after cooling by the heat exchange treatment can be output through the heat source outlet of the heat exchanger 3 and enter the cryogenic refrigerator 4. The absorbed silicon tetrachloride and the recovered silicon tetrachloride after the heat exchange treatment are cryogenically treated together in the cryogenic refrigerator 4 to obtain a chlorosilane solution.

[0069] The present invention allows part of the absorbed silicon tetrachloride to reflux and participate in the second absorption process, thereby ensuring the amount of silicon tetrachloride solution in the second absorption process and allowing the second absorption process to proceed normally.

[0070] The solution of the present invention will be further described below with reference to specific embodiments.

[0071] Example 1

[0072] like Figure 2 As shown, the method for separating hydrogen to be processed in polysilicon production in this embodiment includes:

[0073] The hydrogen to be treated enters the first absorption unit 1 through the hydrogen to be treated inlet of the first absorption unit 1, and the chlorosilane lean liquid enters the first absorption unit 1 through the chlorosilane lean liquid inlet of the first absorption unit 1. In the first absorption unit 1, the chlorosilane lean liquid undergoes a first absorption treatment on the hydrogen to be treated to obtain intermediate hydrogen and chlorosilane rich liquid;

[0074] The intermediate hydrogen is outputted through the intermediate hydrogen outlet at the top of the first absorption unit 1 and enters the second absorption unit 2 through the intermediate hydrogen inlet of the second absorption unit 2;

[0075] The high-purity silicon tetrachloride liquid from the distillation device enters the heat exchanger 3 through the heat source inlet of the heat exchanger 3, undergoes heat exchange treatment and cooling in the heat exchanger 3, is output through the heat source outlet of the heat exchanger 3, enters the cryogenic refrigerator 4 through the heat source inlet, undergoes cryogenic treatment to obtain a silicon tetrachloride solution, is output through the heat source outlet of the cryogenic refrigerator 4, and enters the second absorption unit 2 through the silicon tetrachloride inlet at the top of the tower;

[0076] In the second absorption unit 2, the silicon tetrachloride solution and the intermediate hydrogen are subjected to a second absorption treatment in countercurrent, and the recovered hydrogen is output from the top of the second absorption unit 2 to the downstream hydrogen adsorption process, and the absorbed silicon tetrachloride is output from the silicon tetrachloride absorption outlet of the bottom of the second absorption unit 2, pressurized by the pressure pump 5, and enters the heat exchanger 3 from the cold source inlet of the heat exchanger 3 for heat exchange treatment, and is then sent to the cold hydrogenation device after utilizing the cold energy;

[0077] In the first absorption unit 1, the pressure is 0.9 MPaG and the temperature is -65°C; the intermediate hydrogen comprises, by mass percentage, 96.56% hydrogen, 78.4 PPB hydrogen chloride, 0.89% dichlorosilane, 2.14% trichlorosilane, and 0.40% silicon tetrachloride;

[0078] In the second absorption unit 2, the temperature is -65°C and the pressure is 0.9 MPaG; the mass ratio of high-purity silicon tetrachloride from distillation (net replenishment amount) to the hydrogen to be treated is 10:1.

[0079] In this embodiment, the heat exchanger 3 can recover about 95% of the cooling energy of the absorbed silicon tetrachloride sent out of the boundary area, and the cooling energy consumption of the cryogenic refrigerator 4 is 0.0116kW·h / kg of hydrogen to be treated;

[0080] The recovered hydrogen includes, by mass percentage, 98.85% hydrogen, 47.8ppb hydrogen chloride, <1ppb dichlorosilane, <1ppb trichlorosilane, and 1.15% silicon tetrachloride. After the second absorption treatment, the chlorosilane content in the intermediate hydrogen is reduced from 3.43% to 1.15%, and the hydrogen chloride content is reduced by 39%.

[0081] The processing load of the hydrogen adsorption tower (recovering the amount of chlorosilane and trace amounts of hydrogen chloride, methane, and methylsilane in hydrogen) is reduced by 67.36%. The number of hydrogen adsorption towers can be reduced from 6 sets of 18 units to 2 sets of 6 units. The amount of activated carbon filled in the hydrogen adsorption tower is reduced from 960 tons to 320 tons. The investment in the hydrogen adsorption tower water system and the refrigerant (circulating water or evaporative cooling) and steam consumption are also reduced by two-thirds. The processing capacity, compressor scale, refrigerant consumption and power consumption of the regeneration system are reduced by two-thirds. The regeneration system of the dehydrogenation crude fractionation tower recovers two-thirds of the waste chlorosilane.

[0082] Example 2

[0083] like Figure 3 As shown, the method for separating hydrogen to be processed in polysilicon production in this embodiment includes:

[0084] The hydrogen to be treated enters the first absorption unit 1 through the hydrogen to be treated inlet of the first absorption unit 1, and the chlorosilane lean liquid enters the first absorption unit 1 through the chlorosilane lean liquid inlet of the first absorption unit 1. In the first absorption unit 1, the chlorosilane lean liquid undergoes a first absorption treatment on the hydrogen to be treated to obtain intermediate hydrogen and chlorosilane rich liquid;

[0085] The intermediate hydrogen is outputted through the intermediate hydrogen outlet at the top of the first absorption unit 1 and enters the second absorption unit 2 through the intermediate hydrogen inlet of the second absorption unit 2;

[0086] The high-purity silicon tetrachloride liquid from the distillation device enters the heat exchanger 3 through the heat source inlet of the heat exchanger 3, undergoes heat exchange treatment in the heat exchanger 3, is output through the heat source outlet of the heat exchanger 3, enters the cryogenic refrigerator 4 through the heat source inlet, undergoes cryogenic treatment to obtain a silicon tetrachloride solution, is output through the heat source outlet of the cryogenic refrigerator 4, and enters the second absorption unit 2 through the silicon tetrachloride inlet at the top of the tower of the second absorption unit 2;

[0087] In the second absorption unit 2, the silicon tetrachloride solution and the intermediate hydrogen are subjected to a second absorption treatment in countercurrent, and the recovered hydrogen is output from the top of the second absorption unit 2 and sent to the downstream hydrogen adsorption process, and the absorbed silicon tetrachloride is output from the silicon tetrachloride absorption outlet of the bottom of the second absorption unit 2. After being pressurized by the pressure pump 5, a portion enters the heat exchanger 3 from the cold source inlet of the heat exchanger 3 for heat exchange treatment, and is sent to the anti-disproportionation device after utilizing the cold capacity; the other portion is mixed with the high-purity silicon tetrachloride from the distillation device after heat exchange treatment output from the heat source outlet of the heat exchanger 3, enters the cryogenic refrigerator 4 for cryogenic treatment, and then undergoes the second absorption treatment;

[0088] In the first absorption unit 1, the pressure is 0.9 MPaG and the temperature is -65°C; the intermediate hydrogen comprises, by mass percentage, 96.56% hydrogen, 78.4 PPB hydrogen chloride, 0.89% dichlorosilane, 2.14% trichlorosilane, and 0.40% silicon tetrachloride;

[0089] In the second absorption unit 2, the temperature is -65°C and the pressure is 0.9 MPaG; the mass ratio of high-purity silicon tetrachloride from distillation (net replenishment amount) to the hydrogen to be treated is 6.5:1.

[0090] In this embodiment, the heat exchanger 3 can recover about 95% of the cooling energy of the absorbed silicon tetrachloride sent out of the boundary area, and the cooling energy consumption of the cryogenic refrigerator 4 is 0.008kW·h / kg of hydrogen to be treated;

[0091] The recovered hydrogen includes, by mass percentage, 98.83% hydrogen, 58.7ppb hydrogen chloride, 0.01% dichlorosilane, 55ppb trichlorosilane, and 1.15% silicon tetrachloride. After the second absorption treatment, the chlorosilane content in the intermediate hydrogen is reduced from 3.43% to 1.166%, and the hydrogen chloride content is reduced by 25.1%.

[0092] The processing load of the hydrogen adsorption tower (recovering the amount of chlorosilane and trace amounts of hydrogen chloride, methane, and methylsilane in hydrogen) is reduced by 66.86%. The number of hydrogen adsorption towers can be reduced from 6 sets of 18 units to 2 sets of 6 units. The amount of activated carbon filled in the hydrogen adsorption tower is reduced from 960 tons to 320 tons. The investment in the hydrogen adsorption tower water system and the refrigerant (circulating water or evaporative cooling) and steam consumption are also reduced by two-thirds. The processing capacity, compressor scale, refrigerant consumption and power consumption of the regeneration system are reduced by two-thirds. The regeneration system of the dehydrogenation crude fractionation tower reduces the recovery of waste chlorosilane by two-thirds.

[0093] Example 3

[0094] like Figure 4 As shown, the method for separating hydrogen to be processed in polysilicon production in this embodiment includes:

[0095] The second absorption unit 2 is located on the top of the first absorption unit 1, and a partition and a gas distributor are provided between the first absorption unit 1 and the second absorption unit 2;

[0096] The hydrogen to be treated enters the first absorption unit 1 through the hydrogen to be treated inlet of the first absorption unit 1, and the chlorosilane lean liquid enters the first absorption unit 1 through the chlorosilane lean liquid inlet of the first absorption unit 1. In the first absorption unit 1, the chlorosilane lean liquid undergoes a first absorption treatment on the hydrogen to be treated to obtain intermediate hydrogen and chlorosilane rich liquid;

[0097] The intermediate hydrogen is outputted through the intermediate hydrogen outlet at the top of the first absorption unit 1 and enters the second absorption unit 2 through the intermediate hydrogen inlet of the second absorption unit 2;

[0098] The high-purity silicon tetrachloride liquid from the distillation device enters the heat exchanger 3 through the heat source inlet of the heat exchanger 3, undergoes heat exchange treatment in the heat exchanger 3, is output through the heat source outlet of the heat exchanger 3, enters the cryogenic refrigerator 4 through the heat source inlet, undergoes cryogenic treatment to obtain a silicon tetrachloride solution, is output through the heat source outlet of the cryogenic refrigerator 4, and enters the second absorption unit 2 through the silicon tetrachloride inlet at the top of the tower of the second absorption unit 2;

[0099] In the second absorption unit 2, the silicon tetrachloride solution and the intermediate hydrogen are subjected to a second absorption treatment in countercurrent, and the recovered hydrogen is output from the top of the second absorption unit 2 and sent to the downstream hydrogen adsorption process, and the absorbed silicon tetrachloride is output from the silicon tetrachloride absorption outlet of the bottom of the second absorption unit 2. After being pressurized by the pressure pump 5, a portion enters the heat exchanger 3 from the cold source inlet of the heat exchanger 3 for heat exchange treatment, and is sent to the anti-disproportionation device after utilizing the cold capacity; the other portion is mixed with the high-purity silicon tetrachloride from the distillation device after heat exchange treatment output from the heat source outlet of the heat exchanger 3, enters the cryogenic refrigerator 4 for cryogenic treatment, and then undergoes the second absorption treatment;

[0100] In the first absorption unit 1, the pressure is 0.9 MPaG and the temperature is -65°C; the intermediate hydrogen comprises, by mass percentage, 96.56% hydrogen, 78.4 PPB hydrogen chloride, 0.89% dichlorosilane, 2.14% trichlorosilane, and 0.40% silicon tetrachloride;

[0101] In the second absorption unit 2, the temperature is -65°C and the pressure is 0.9 MPaG; the mass ratio of high-purity silicon tetrachloride from distillation (net replenishment amount) to the hydrogen to be treated is 6.5:1.

[0102] In this embodiment, the heat exchanger 3 can recover about 95% of the cooling energy of the absorbed silicon tetrachloride sent out of the boundary area, and the cooling energy consumption of the cryogenic refrigerator 4 is 0.008kW·h / kg of hydrogen to be treated;

[0103] The recovered hydrogen includes, by mass percentage, 98.83% hydrogen, 58.7ppb hydrogen chloride, 0.01% dichlorosilane, 55ppb trichlorosilane, and 1.15% silicon tetrachloride. After the second absorption treatment, the chlorosilane content in the intermediate hydrogen is reduced from 3.43% to 1.166%, and the hydrogen chloride content is reduced by 25.1%.

[0104] The processing load of the hydrogen adsorption tower (recovering the amount of chlorosilane and trace amounts of hydrogen chloride, methane, and methylsilane in hydrogen) is reduced by 66.86%. The number of hydrogen adsorption towers can be reduced from 6 sets of 18 units to 2 sets of 6 units. The amount of activated carbon filled in the hydrogen adsorption tower is reduced from 960 tons to 320 tons. The investment in the hydrogen adsorption tower water system and the refrigerant (circulating water or evaporative cooling) and steam consumption are also reduced by two-thirds. The processing capacity, compressor scale, refrigerant consumption and power consumption of the regeneration system are reduced by two-thirds. The regeneration system of the dehydrogenation crude fractionation tower reduces the recovery of waste chlorosilane by two-thirds.

[0105] Each embodiment in this specification is described in a related manner. Similar parts between the embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences from other embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for separating hydrogen to be processed in polysilicon production, characterized in that: include: Using the chlorosilane lean liquid to perform a first absorption treatment on the hydrogen to be treated to obtain a chlorosilane rich liquid and intermediate hydrogen; The intermediate hydrogen is subjected to a second absorption treatment using a silicon tetrachloride solution to obtain absorbed silicon tetrachloride and recovered hydrogen.

2. The separation method according to claim 1, wherein The silicon tetrachloride solution is obtained by performing cryogenic treatment on recovered silicon tetrachloride.

3. The separation method according to claim 2, characterized in that The silicon tetrachloride solution is obtained by subjecting a mixed solution comprising a recovered silicon tetrachloride solution and a silicon tetrachloride absorption solution to cryogenic treatment.

4. The separation method according to claim 2 or 3, characterized in that Before the cryogenic treatment, the method includes subjecting the absorbed silicon tetrachloride and the recovered silicon tetrachloride to heat exchange treatment.

5. The separation method according to claim 4, characterized in that In the first absorption treatment, the temperature is -65 to -60°C and the pressure is 0.8 to 1.5 MPaG; and / or, In the second absorption treatment, the temperature is -65 to -50°C and the pressure is 0.8 to 1.5 MPaG; and / or, The mass ratio of the recovered silicon tetrachloride to the hydrogen to be treated is (2-25):

1.

6. A system for separating hydrogen to be processed in polysilicon production for implementing the separation method according to any one of claims 1 to 5, characterized in that: comprising a first absorption unit and a second absorption unit; The first absorption unit has a chlorosilane lean solution inlet and a to-be-treated hydrogen inlet. The intermediate hydrogen outlet of the first absorption unit is connected to the intermediate hydrogen inlet of the second absorption unit. The second absorption unit has a silicon tetrachloride inlet.

7. The separation system according to claim 6, characterized in that It also includes a cryogenic cooler, wherein the heat source outlet of the cryogenic cooler is connected to the silicon tetrachloride inlet.

8. The separation system according to claim 7, characterized in that It also includes a heat exchanger, the silicon tetrachloride absorption outlet of the second absorption unit is connected to the cold source inlet of the heat exchanger, the recovered silicon tetrachloride enters the heat exchanger through the heat source inlet of the heat exchanger, and the heat source outlet of the heat exchanger is connected to the heat source inlet of the cryogenic refrigerator.

9. The separation system according to claim 8, characterized in that The silicon tetrachloride absorption outlet of the second absorption unit and the heat source outlet of the heat exchanger are both in communication with the heat source inlet of the cryogenic refrigerator.

10. The separation system according to any one of claims 6 to 9, characterized in that: The first absorption unit and the second absorption unit are absorption towers respectively; or, The separation system is an absorption tower, which includes a first absorption unit and a second absorption unit connected to each other, wherein the second absorption unit is located on the top of the first absorption unit.

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