System for synthesizing trichlorosilane

Abstract

The utility model provides a system for synthesizing trichlorosilane. The system for synthesizing trichlorosilane comprises a trichlorosilane synthesis reaction device, a first gas-solid separation unit, a first tail gas treatment unit, a silicon tetrachloride hydrogenation reaction device, a second gas-solid separation unit, a second tail gas treatment unit and a product separation and purification unit. According to the system, through the technological process of fusing the trichlorosilane synthesis reaction and the silicon tetrachloride hydrogenation reaction, efficient utilization of silicon powder, hydrogen and silicon tetrachloride is achieved, the investment and operation cost is saved, and meanwhile the raw material consumption is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of polysilicon production, and particularly relates to a system for synthesizing trichlorosilane. Background Technique

[0002] In the existing polysilicon production process, the synthesis of trichlorosilane and the hydrogenation of silicon tetrachloride are usually carried out in two independent production workshops, and there is basically no connection between them. Moreover, the fine silicon powder that cannot be used in the traditional silicon tetrachloride hydrogenation process is treated as solid waste, but they all use the same raw materials (silicon powder, hydrogen, hydrogen chloride) and similar post-treatment processes (dust removal, quenching and rinsing, condensation, compression, adsorption and purification (this step can be cancelled), rectification, slurry treatment), which results in waste of investment and increases the loss rate of silicon powder.

[0003] Although there are also literature reports on combining the synthesis step of trichlorosilane with the hydrogenation step of silicon tetrachloride, the effect is not very ideal. For example, the existing literature (CN109052410B) discloses a method for producing trichlorosilane and its application. Although it is proposed to use the fine silicon powder entrained in the silicon tetrachloride hydrogen gas tail gas as the raw material for trichlorosilane synthesis to achieve high utilization of silicon powder, in order to achieve the second gas-solid separation, the pressure of the second tail gas needs to be reduced to the same as that of the fourth tail gas. However, from the actual situation, the volume flow rate of the second tail gas is about 180 times that of the fourth tail gas, and the pressure of the second tail gas is about 13 times that of the fourth tail gas. Obviously, it is seriously uneconomical in terms of usage cost to reduce and then increase the pressure of the second tail gas in order to recover some fine silicon powder with little economic value, and it is not practically operable.

[0004] Therefore, it is of great significance to research and develop a synthesis system of trichlorosilane that can reduce the system operation cost and silicon consumption. Content of the Utility Model

[0005] The main purpose of the utility model is to provide a system for synthesizing trichlorosilane to solve the problems of high operation cost of the trichlorosilane synthesis system and large consumption of silicon powder, hydrogen and silicon tetrachloride in the prior art.

[0006] To achieve the above object, the present utility model provides a system for synthesizing trichlorosilane, which system includes: a trichlorosilane synthesis reaction device, a first gas-solid separation unit, a first tail gas treatment unit, a silicon tetrachloride hydrogenation reaction device, a second gas-solid separation unit, a second tail gas treatment unit, and a product separation and purification unit. Among them, the trichlorosilane synthesis reaction device is used to react hydrogen chloride with first silicon powder to generate synthesis tail gas containing trichlorosilane. The trichlorosilane synthesis reaction device is provided with a hydrogen chloride inlet, a first silicon powder inlet, and a synthesis tail gas outlet; the first gas-solid separation unit is provided with a first inlet and a first separated gas outlet; the first inlet is communicated with the synthesis tail gas outlet; the first tail gas treatment unit is used to enrich the chlorosilane contained in the gas discharged from the first separated gas outlet to obtain a first chlorosilane enrichment and a first recycled hydrogen. The first tail gas treatment unit is provided with a second inlet, a first chlorosilane enrichment outlet, and a first recycled hydrogen outlet; the second inlet is communicated with the first separated gas outlet; the silicon tetrachloride hydrogenation reaction device is used to carry out a hydrogenation reaction of silicon tetrachloride with hydrogen to generate hydrogenation tail gas containing trichlorosilane. The silicon tetrachloride hydrogenation reaction device is provided with a first hydrogen inlet, a silicon tetrachloride inlet, a first recycled hydrogen inlet, a hydrogenation tail gas outlet, and an optional supplementary silicon powder inlet; the first recycled hydrogen inlet is communicated with the first recycled hydrogen outlet; the supplementary silicon powder inlet is used to additionally introduce supplementary silicon powder into the silicon tetrachloride hydrogenation reaction device; the second gas-solid separation unit is provided with a hydrogenation tail gas inlet, a first silicon powder outlet, and a second separated gas outlet; the hydrogenation tail gas inlet is communicated with the hydrogenation tail gas outlet; the first silicon powder outlet is communicated with the first silicon powder inlet and is used to provide raw materials for the synthesis reaction of trichlorosilane; the second tail gas treatment unit is used to enrich the chlorosilane contained in the gas discharged from the second separated gas outlet to obtain a second chlorosilane enrichment and a second recycled hydrogen; the second tail gas treatment unit is provided with a third inlet, a second chlorosilane enrichment outlet, and a second recycled hydrogen outlet; the third inlet is communicated with the second separated gas outlet; the second recycled hydrogen outlet is communicated with the first hydrogen inlet; the product separation and purification unit is used to separate and purify the first chlorosilane enrichment and / or the second chlorosilane enrichment to obtain silicon tetrachloride, trichlorosilane, and slag. The product separation and purification unit is provided with a chlorosilane enrichment inlet, a silicon tetrachloride extraction outlet, a trichlorosilane extraction outlet, and a slag discharge port; the chlorosilane enrichment inlet is communicated with the first chlorosilane enrichment outlet and the second chlorosilane enrichment outlet; the silicon tetrachloride extraction outlet is communicated with the silicon tetrachloride inlet.

[0007] Applying the technical solution of the present utility model, the unreacted first silicon powder remaining after the hydrogenation reaction of silicon tetrachloride and hydrogen is discharged through the first silicon powder outlet and sent into the trichlorosilane synthesis reaction device, enabling this part of the silicon powder (i.e., the first silicon powder) to be used as a reaction raw material for synthesizing trichlorosilane, thereby significantly reducing the consumption of supplementary silicon powder and simultaneously reducing the production cost; at the same time, the by-product first recycled hydrogen generated after the trichlorosilane synthesis reaction is recovered and sent into the silicon tetrachloride hydrogenation reaction device for hydrogenation reaction, thereby realizing the recovery of hydrogen, reducing the consumption of supplementary hydrogen, and reducing the production cost; moreover, the unreacted second recycled hydrogen remaining during the hydrogenation reaction is recovered and utilized, and returned as a reaction raw material to the silicon tetrachloride hydrogenation reaction device, which is beneficial to improving the utilization efficiency of hydrogen and facilitating the closed-loop of hydrogen in the system; the unreacted silicon tetrachloride remaining after the silicon tetrachloride hydrogenation reaction is recovered and utilized, and returned as a reaction raw material to the silicon tetrachloride hydrogenation reaction device, which can improve the utilization efficiency of silicon tetrachloride and reduce the consumption of supplementary silicon tetrachloride.

[0008] In summary, the above system of the present application realizes the efficient utilization of silicon powder, hydrogen, and silicon tetrachloride by integrating the process flows of trichlorosilane synthesis reaction and silicon tetrachloride hydrogenation reaction, saves investment and operating costs, and simultaneously reduces the consumption of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The schematic diagrams in the specification forming a part of the present application are used to provide a further understanding of the present utility model. The schematic embodiments and descriptions thereof of the present utility model are used to explain the present utility model and do not constitute an improper limitation to the present utility model. In the drawings:

[0010] Figure 1 shows a schematic structural diagram of a system for synthesizing trichlorosilane in a preferred embodiment of the present application;

[0011] Figure 2 shows a schematic structural diagram of a first gas-solid separation unit in a preferred embodiment of the present application;

[0012] Figure 3 shows a schematic structural diagram of a second gas-solid separation unit in a preferred embodiment of the present application;

[0013] Figure 4 shows a schematic structural diagram of a first tail gas treatment unit in a preferred embodiment of the present application;

[0014] Figure 5 shows a schematic structural diagram of a second tail gas treatment unit in a preferred embodiment of the present application;

[0015] Figure 6 shows a schematic structural diagram of a product separation and purification unit in a preferred embodiment of the present application.

[0016] Among them, the above-mentioned drawings include the following reference numerals:

[0017] 100, trichlorosilane synthesis reaction device; 101, hydrogen chloride inlet; 102, first silicon powder inlet; 103, synthesis tail gas outlet;

[0018] 200, first gas-solid separation unit; 201, first gas inlet; 202, first separated gas outlet; 203, second silicon powder outlet; 204, solid waste outlet; 210, first primary gas-solid separation device; 220, first secondary gas-solid separation device;

[0019] 300, first tail gas treatment unit; 301, second gas inlet; 302, first chlorosilane enrichment product outlet; 303, first recycled hydrogen outlet; 304, first condensed gas outlet; 305, first condensed gas inlet; 306, compressed gas outlet; 307, compressed gas inlet; 308, recycled hydrogen chloride outlet; 310, first condensation device; 320, first compression device; 330, hydrogen chloride adsorption device;

[0020] 400, silicon tetrachloride hydrogenation reaction device; 401, first hydrogen inlet; 402, silicon tetrachloride inlet; 403, first recycled hydrogen inlet; 404, hydrogenation tail gas outlet;

[0021] 500, second gas-solid separation unit; 501, hydrogenation tail gas inlet; 502, first silicon powder outlet; 503, second separated gas outlet; 504, third silicon powder outlet; 510, second primary gas-solid separation device; 520, second secondary gas-solid separation device;

[0022] 600, second tail gas treatment unit; 601, third gas inlet; 602, second chlorosilane enrichment product outlet; 603, hydrogen outlet; 604, second condensed gas outlet; 605, second condensed gas inlet; 610, second condensation device; 620, second compression device;

[0023] 700, product separation and purification unit; 701, chlorosilane enrichment product inlet; 702, silicon tetrachloride extraction outlet; 703, trichlorosilane extraction outlet; 704, slag discharge port; 705, liquid-phase product outlet; 706, liquid-phase product inlet; 710, solid-liquid separation device; 720, rectification device. Detailed implementation manners

[0024] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will describe the present invention in detail with reference to the embodiments.

[0025] As described in the background art, the existing trichlorosilane synthesis system has problems such as high operating costs and large consumption of silicon powder, hydrogen, and silicon tetrachloride. To solve the above technical problems, the present application provides a system for synthesizing trichlorosilane, such as Figure 1As shown in the figure, the system for synthesizing trichlorosilane includes: a trichlorosilane synthesis reaction device 100, a first gas-solid separation unit 200, a first tail gas treatment unit 300, a silicon tetrachloride hydrogenation reaction device 400, a second gas-solid separation unit 500, a second tail gas treatment unit 600, and a product separation and purification unit 700. Among them, the trichlorosilane synthesis reaction device 100 is used to react hydrogen chloride and first silicon powder to generate synthesis tail gas containing trichlorosilane. The trichlorosilane synthesis reaction device 100 is provided with a hydrogen chloride inlet 101, a first silicon powder inlet 102, and a synthesis tail gas outlet 103; the first gas-solid separation unit 200 is provided with a first air inlet 201 and a first separated gas outlet 202; the first air inlet 201 is communicated with the synthesis tail gas outlet 103; the first tail gas treatment unit 300 is used to enrich the chlorosilane in the gas discharged from the first separated gas outlet 202 to obtain a first chlorosilane enrichment and a first recycled hydrogen; the first tail gas treatment unit 300 is provided with a second air inlet 301, a first chlorosilane enrichment outlet 302, and a first recycled hydrogen outlet 303; the second air inlet 301 is communicated with the first separated gas outlet 202; the silicon tetrachloride hydrogenation reaction device 400 is used to carry out a hydrogenation reaction between silicon tetrachloride and hydrogen to generate hydrogenation tail gas containing trichlorosilane. The silicon tetrachloride hydrogenation reaction device 400 is provided with a first hydrogen inlet 401, a silicon tetrachloride inlet 402, a first recycled hydrogen inlet 403, a hydrogenation tail gas outlet 404, and an optional supplementary silicon powder inlet; the first recycled hydrogen inlet 403 is communicated with the first recycled hydrogen outlet 303; the supplementary silicon powder inlet is used to additionally introduce supplementary silicon powder into the silicon tetrachloride hydrogenation reaction device; the second gas-solid separation unit 500 is provided with a hydrogenation tail gas inlet 501, a first silicon powder outlet 502, and a second separated gas outlet 503; the hydrogenation tail gas inlet 501 is communicated with the hydrogenation tail gas outlet 404; the first silicon powder outlet 502 is communicated with the first silicon powder inlet 102 and is used to provide raw materials for the synthesis reaction of trichlorosilane; the second tail gas treatment unit 600 is used to enrich the chlorosilane in the gas discharged from the second separated gas outlet 503 to obtain a second chlorosilane enrichment and a second recycled hydrogen; the second tail gas treatment unit 600 is provided with a third air inlet 601, a second chlorosilane enrichment outlet 602, and a second recycled hydrogen outlet 603; the third air inlet 601 is communicated with the second separated gas outlet 503; the second recycled hydrogen outlet 603 is communicated with the first hydrogen inlet 401; the product separation and purification unit 700 is used to separate and purify the first chlorosilane enrichment and / or the second chlorosilane enrichment to obtain silicon tetrachloride, trichlorosilane, and slag; the product separation and purification unit 700 is provided with a chlorosilane enrichment inlet 701, a silicon tetrachloride extraction outlet 702, a trichlorosilane extraction outlet 703, and a slag discharge port 704; the chlorosilane enrichment inlet 701 is communicated with the first chlorosilane enrichment outlet 302 and the second chlorosilane enrichment outlet 602; the silicon tetrachloride extraction outlet 702 is communicated with the silicon tetrachloride inlet 402.

[0026] The trichlorosilane synthesis reaction device 100 is used to react hydrogen chloride with first silicon powder to generate synthesis tail gas containing trichlorosilane. Using the first gas-solid separation unit 200 to treat the synthesis tail gas can separate the unreacted silicon powder from the gaseous substances, so that the gas-solid mixture (i.e., the first separated gas, mixed with a small amount of silicon powder) is discharged from the first separated gas outlet 202; using the first tail gas treatment unit 300 to enrich the chlorosilane in the first separated gas to obtain a first chlorosilane enrichment (mixed with a small amount of silicon powder) and first recycled hydrogen, and the first recycled hydrogen is discharged from the first recycled hydrogen outlet 303 and sent to the silicon tetrachloride hydrogenation reaction device 400 as a raw material gas to participate in the hydrogenation reaction of silicon tetrachloride; the silicon tetrachloride hydrogenation reaction device 400 is used to react silicon tetrachloride with hydrogen to generate hydrogenation tail gas containing trichlorosilane, and the hydrogenation tail gas is discharged from the hydrogenation tail gas outlet 404 and sent to the second gas-solid separation unit 500; the second gas-solid separation unit 500 is used to screen the silicon powder in a specific particle size range in the hydrogenation tail gas so that it can be used as a reaction raw material for synthesizing trichlorosilane, and at the same time, a gas-solid mixture (i.e., the second separated gas, mixed with a small amount of silicon powder) is separated; using the second tail gas treatment unit 600 to enrich the chlorosilane in the gas discharged from the second separated gas outlet 503 to obtain a second chlorosilane enrichment (mixed with a small amount of silicon powder) and second recycled hydrogen, and the second recycled hydrogen is discharged from the second recycled hydrogen outlet 603 and returned to the silicon tetrachloride hydrogenation reaction device 400 for recycling; using the product separation and purification unit 700 to separate and purify the first chlorosilane enrichment and / or the second chlorosilane enrichment to obtain silicon tetrachloride, trichlorosilane and slag; the silicon tetrachloride is discharged from the silicon tetrachloride extraction outlet 702 and returned to the silicon tetrachloride hydrogenation reaction device 400 for recycling. In addition, since the silicon powder raw material usually contains impurity components (such as oxides of calcium, aluminum and iron), therefore, this part of the impurity components will be converted into metal chlorides (calcium chloride, aluminum chloride and iron chloride) after the trichlorosilane synthesis reaction and enriched in the slag and discharged.

[0027] The following chemical reactions occur in the above-mentioned trichlorosilane synthesis reaction device 100:

[0028] (1) Main reaction: Si + HCl → SiHCl3 + H2;

[0029] (2) Side reaction: Si + HCl → SiCl4 + H2;

[0030] (3) Side reaction: Si + HCl → SiH2Cl2 + H2;

[0031] (4) Side reaction: M + HCl → MCl n (M represents one or more of Ca, Al and Fe, and n represents the valence of the M element).

[0032] In the above-mentioned silicon tetrachloride hydrogenation reaction device 400, the following chemical reactions occur:

[0033] (1) Main reaction: SiCl4 + Si + H2 → SiHCl3

[0034] (2) Side reaction: Si + HCl → SiCl4 + H2

[0035] (3) Side reaction: SiCl4 + SiHCl3 → SiH2Cl2

[0036] (4) Side reaction: M + HCl → MCl n (M represents one or more of Ca, Al, and Fe, and n represents the valence of the M element).

[0037] In the above-mentioned system for synthesizing trichlorosilane provided by the present application, the unreacted first silicon powder remaining after the hydrogenation reaction of silicon tetrachloride and hydrogen is discharged through the first silicon powder outlet 502 and sent into the trichlorosilane synthesis reaction device 100, enabling this part of the silicon powder to be used as a reaction raw material (i.e., the first silicon powder) for synthesizing trichlorosilane, thereby significantly reducing the consumption of supplementary silicon powder and reducing production costs at the same time; meanwhile, the by-product first recycled hydrogen generated after the trichlorosilane synthesis reaction is recovered and sent into the silicon tetrachloride hydrogenation reaction device 400 for hydrogenation reaction, thereby realizing the recovery of hydrogen, reducing the consumption of supplementary hydrogen, and reducing production costs; moreover, the unreacted second recycled hydrogen remaining during the hydrogenation reaction is recovered and utilized, and returned to the silicon tetrachloride hydrogenation reaction device 400 as a reaction raw material, which is beneficial to improving the utilization efficiency of hydrogen and realizing the closed-loop of hydrogen in the system; the unreacted silicon tetrachloride remaining after the silicon tetrachloride hydrogenation reaction is recovered and utilized, and returned to the silicon tetrachloride hydrogenation reaction device 400 as a reaction raw material, which can improve the utilization efficiency of silicon tetrachloride and reduce the consumption of supplementary silicon tetrachloride.

[0038] In summary, the above-mentioned system of the present application realizes the efficient utilization of silicon powder, hydrogen, and silicon tetrachloride by integrating the technological processes of trichlorosilane synthesis reaction and silicon tetrachloride hydrogenation reaction, saves investment and operating costs, and reduces the consumption of raw materials at the same time.

[0039] In a preferred embodiment, the first gas-solid separation unit 200 includes a multi-stage gas-solid separation device with gas phases connected in series, such as Figure 2As shown, it preferably includes a first primary gas-solid separation device 210 and a first secondary gas-solid separation device 220 arranged in series in the gas phase; the first primary gas-solid separation device 210 is provided with a first air inlet 201 and a second silicon powder outlet 203; the second silicon powder outlet 203 is communicated with the first silicon powder inlet 102 for returning at least part of the second silicon powder to the trichlorosilane synthesis reaction device 100; the first secondary gas-solid separation device 220 is provided with a first separated gas outlet 202 and a solid waste outlet 204; the solid waste outlet 204 is used for discharging the remaining silicon powder.

[0040] It should be noted that the term "gas phase in series" in this application means that the gas outlet of the previous-stage gas-solid separation device is communicated with the gas inlet and outlet of the subsequent-stage gas-solid separation device.

[0041] Compared with a single-stage gas-solid separation device, a multi-stage gas-solid separation device with gas phase in series is beneficial to screening silicon powder in different particle size ranges in the synthesis tail gas, so as to facilitate subsequent targeted recycling of silicon powder in different particle size ranges or discharging it as solid waste, which is beneficial to improving the utilization rate of silicon powder. Using the above-mentioned first primary gas-solid separation device 210 and first secondary gas-solid separation device 220 arranged in series in the gas phase is beneficial to minimizing the system operation cost on the basis of improving the utilization rate of silicon powder.

[0042] In a preferred embodiment, the silicon tetrachloride hydrogenation reaction device 400 is further provided with a second silicon powder inlet, and the second gas-solid separation unit 500 includes a multi-stage gas-solid separation device arranged in series in the gas phase, such as Figure 3 As shown, it preferably includes a second primary gas-solid separation device 510 and a second secondary gas-solid separation device 520 arranged in series in the gas phase; the second primary gas-solid separation device 510 is provided with a hydrogenation tail gas inlet 501 and a third silicon powder outlet 504; the third silicon powder outlet 504 is communicated with the second silicon powder inlet for returning at least part of the third silicon powder to the silicon tetrachloride hydrogenation reaction device 400; the second secondary gas-solid separation device 520 is provided with a first silicon powder outlet 502 and a second separated gas outlet 503.

[0043] Compared with a single-stage gas-solid separation device, a multi-stage gas-solid separation device with gas phase in series is beneficial to screening silicon powder in different particle size ranges in the hydrogenation tail gas, so as to facilitate subsequent targeted recycling of silicon powder in different particle size ranges, which is beneficial to improving the utilization rate of silicon powder. Using the above-mentioned first primary gas-solid separation device 210 and first secondary gas-solid separation device 220 arranged in series in the gas phase is beneficial to minimizing the system operation cost on the basis of improving the utilization rate of silicon powder.

[0044] In a preferred embodiment, such as Figure 4As shown, the first tail gas treatment unit 300 includes a first condensation device 310, a first compression device 320, and a hydrogen chloride adsorption device 330. Among them, the first condensation device 310 is provided with a second air inlet 301, a first chlorosilane enriched product outlet 302, and a first condensed gas outlet 304; the first compression device 320 is provided with a first condensed gas inlet 305 and a compressed gas outlet 306; the first condensed gas inlet 305 is communicated with the first condensed gas outlet 304; the hydrogen chloride adsorption device 330 is provided with a compressed gas inlet 307, a first recycled hydrogen outlet 303, and a recycled hydrogen chloride outlet 308; the recycled hydrogen chloride outlet 308 is communicated with the hydrogen chloride inlet 101. The setting of the first condensation device 310 is beneficial to improving the liquefaction rate of the first separated gas, and is beneficial to enriching SiHCl3, SiCl4, and a small amount of SiH2Cl2 in the solid-liquid mixture dispersed with residual silicon powder, while making HCl and H2 form the first condensed gas and exist in a gaseous form, which is beneficial to the subsequent separation and purification of SiHCl3 and SiCl4; the settings of the first compression device 320 and the hydrogen chloride adsorption device 330 are beneficial to the recycling and utilization of HCl and H2, and are beneficial to improving the utilization rates of hydrogen chloride and hydrogen. Returning at least part of the recycled hydrogen chloride to the trichlorosilane synthesis reaction device 100 is beneficial to the efficient utilization of hydrogen chloride gas, reducing the consumption of hydrogen chloride input from the outside by the system, and at the same time is beneficial to reducing the content of hydrogen chloride in the first recycled hydrogen, thereby being beneficial to improving the purity of the first recycled hydrogen.

[0045] In a preferred embodiment, as Figure 5 shown, the second tail gas treatment unit 600 includes a second condensation device 610 and a second compression device 620. Among them, the second condensation device 610 is provided with a third air inlet 601, a second chlorosilane enriched product outlet 602, and a second condensed gas outlet 604; the second compression device 620 is provided with a second condensed gas inlet 605 and a hydrogen outlet 603; the second condensed gas inlet 605 is communicated with the second condensed gas outlet 604. The setting of the second condensation device 610 is beneficial to liquefying the second separated gas to obtain unreacted liquid SiCl4 and liquid product HCl, while H2 still exists in a gaseous form, which is beneficial to the subsequent separation and purification of SiCl4; the setting of the first compression device 320 is beneficial to the recycling and utilization of H2, and is beneficial to improving the utilization rate of hydrogen.

[0046] In a preferred embodiment, the third inlet 601 and the second separated gas outlet 503 are communicated through a separated gas delivery pipeline; the system for synthesizing trichlorosilane further includes a heat exchange device; the heat exchange device is arranged on the separated gas delivery pipeline and is used for cooling the second separated gas. The arrangement of the heat exchange device is beneficial to narrowing the temperature difference between the target treatment temperature of the second chlorosilane-rich substance and the second separated gas, thereby being beneficial to reducing the treatment pressure of the second condensation device 610, and thus being beneficial to improving the treatment efficiency and reducing the equipment operation cost.

[0047] In a preferred embodiment, the system for synthesizing trichlorosilane further includes a preheating unit, and the preheating unit includes a first recycled hydrogen preheating device, a second recycled hydrogen preheating device and a silicon tetrachloride preheating device; preferably, the first recycled hydrogen inlet 403 and the first recycled hydrogen outlet 303 are communicated through a first recycled hydrogen delivery pipeline, and the first recycled hydrogen preheating device is arranged on the first recycled hydrogen delivery pipeline; the second recycled hydrogen outlet 603 and the first hydrogen inlet 401 are communicated through a second recycled hydrogen delivery pipeline, and the second recycled hydrogen preheating device is arranged on the second recycled hydrogen delivery pipeline; the silicon tetrachloride extraction outlet 702 and the silicon tetrachloride inlet 402 are communicated through a silicon tetrachloride delivery pipeline, and the silicon tetrachloride preheating device is arranged on the silicon tetrachloride delivery pipeline. Compared with the system without a preheating unit, by using the first recycled hydrogen preheating device, the second recycled hydrogen preheating device and the silicon tetrachloride preheating device in the above preheating unit to preheat the first recycled hydrogen, the second recycled hydrogen and the silicon tetrachloride respectively, it is beneficial to improve the reaction activity of the silicon tetrachloride and hydrogen, and thus beneficial to improving the formation rate of elemental silicon.

[0048] In a preferred embodiment, the system for synthesizing trichlorosilane further includes a hydrogen chloride synthesis device, and the hydrogen chloride synthesis device is used for reacting chlorine and hydrogen to obtain hydrogen chloride. The hydrogen chloride synthesis device is provided with a chlorine inlet, a second hydrogen inlet and a hydrogen chloride outlet, and the hydrogen chloride outlet is communicated with the hydrogen chloride inlet 101. The arrangement of the hydrogen chloride synthesis device is beneficial to providing reaction raw materials for the synthesis reaction of trichlorosilane.

[0049] In a preferred embodiment, the first primary gas-solid separation device 210 is used for separating silicon powder with a particle size > 1 μm; the first secondary gas-solid separation device 220 is used for separating silicon powder with a particle size of 1 - 10 μm. Using the above first primary gas-solid separation device 210 and the first secondary gas-solid separation device 220 respectively is beneficial to improving the separation efficiency of silicon powder in the above particle size range.

[0050] In a preferred embodiment, the second primary gas-solid separation device 510 includes, but is not limited to, a cyclone separator for separating silicon powder with a particle size ≥ 10 μm; the second secondary gas-solid separation device 520 includes, but is not limited to, a filter with a metal sintered filter element for separating silicon powder with a particle size < 10 μm and ≥ 1 μm. Compared with other types of gas-solid separation devices, using the above preferred types of the second primary gas-solid separation device 510 and the second secondary gas-solid separation device 520 is respectively beneficial to improving the separation efficiency of silicon powder in the above particle size range.

[0051] In a preferred embodiment, as Figure 6 shown, the product separation and purification unit 700 includes a solid-liquid separation device 710 and a rectification device 720. Among them, the solid-liquid separation device 710 is used to perform solid-liquid separation on the first chlorosilane enrichment and / or the second chlorosilane enrichment to obtain a liquid-phase product and slag, and the solid-liquid separation device 710 is provided with a chlorosilane enrichment inlet 701, a liquid-phase product outlet 705, and a slag discharge port 704; the rectification device 720 is used to separate and purify the liquid-phase product to obtain trichlorosilane and silicon tetrachloride, and the rectification device 720 is provided with a liquid-phase product inlet 706, a silicon tetrachloride extraction outlet 702, and a trichlorosilane extraction outlet 703. The solid-liquid separation device 710 is used to separate and remove the metal chlorides (such as calcium chloride, aluminum chloride, and iron chloride) and silicon powder dispersed in the chlorosilane enrichment, so as to obtain liquid chlorosilane (i.e., the liquid-phase product), which is beneficial for subsequent separation and purification; the rectification device 720 is used to separate and purify the liquid-phase product to obtain trichlorosilane and silicon tetrachloride.

[0052] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0053] Example 1

[0054] Using the system for synthesizing trichlorosilane as Figure 1 shown to synthesize trichlorosilane, including the following process:

[0055] Hydrogen chloride and the first silicon powder are introduced into the trichlorosilane synthesis reaction device 100 for a synthesis reaction to obtain synthesis tail gas containing trichlorosilane; among them, the feeding rate of hydrogen chloride is 1000 kg / h, and the feeding rate of the first silicon powder is 250 kg / h; the temperature of the synthesis reaction is 300 °C;

[0056] The synthesis tail gas is subjected to a first screening in the first gas-solid separation unit 200 to obtain a first separated gas;

[0057] The first tail gas treatment unit 300 is used to enrich the chlorosilane in the first separated gas. The first separated gas is subjected to a first condensation treatment in the first condensation device 310 to obtain a first chlorosilane enrichment and a first condensed gas. The first condensed gas is subjected to a first compression treatment in the first compression device 320 to obtain a compressed gas with a pressure of 0.4 MPa. The compressed gas is subjected to an adsorption treatment by the hydrogen chloride adsorption device 330 to obtain a recovered hydrogen chloride gas and a first recovered hydrogen. Among them, the lowest condensation temperature of the first condensation treatment is -30°C; the temperature of the first chlorosilane enrichment is -25°C; all the obtained recovered hydrogen chloride gas is returned to the trichlorosilane synthesis reaction device 100;

[0058] Silicon tetrachloride, the first recovered hydrogen, supplementary hydrogen, supplementary silicon tetrachloride and supplementary silicon powder are introduced into the silicon tetrachloride hydrogenation reaction device 400 for hydrogenation reaction to obtain hydrogenation tail gas. Among them, the temperature of the hydrogenation reaction is 530°C; the feeding rate of silicon tetrachloride is 60000 kg / h, the total feeding rate of the first recovered hydrogen and supplementary hydrogen is 190 kg / h, the total feeding rate of silicon tetrachloride and supplementary silicon tetrachloride is 60000 kg / h, and the feeding rate of supplementary silicon powder is 1400 kg / h;

[0059] The hydrogenation tail gas is subjected to a second screening in the second gas-solid separation unit 500 to obtain a second separated gas and silicon powder with a particle size ≤ 5 μm. The silicon powder with a particle size ≤ 5 μm is returned to the trichlorosilane synthesis reaction device 100 as the first silicon powder;

[0060] The second separated gas is cooled to -35°C. The second tail gas treatment unit 600 is used to enrich the chlorosilane in the second separated gas. The second separated gas is subjected to a second condensation treatment in the second condensation device 610 to obtain a second chlorosilane enrichment and a second condensed gas. The second condensed gas is subjected to a second compression treatment in the second compression device 620 to obtain a second recovered hydrogen. All the obtained second recovered hydrogen is returned to the silicon tetrachloride hydrogenation reaction device 400. The total feeding rate of the first recovered hydrogen and the second recovered hydrogen is 190.8 kg / h (that is, the hourly feeding amount includes 25.8 kg of the first recovered hydrogen and 165 kg of the second recovered hydrogen);

[0061] The above-obtained first chlorosilane enrichment and second chlorosilane enrichment are introduced into the product separation and purification unit 700 for separation and purification. This process includes: introducing the first chlorosilane enrichment and second chlorosilane enrichment into the solid-liquid separation device 710 to obtain a liquid-phase product and a slag. The slag is discharged from the slag discharge port 704. The obtained liquid-phase product is subjected to rectification treatment by the rectification device 720 to obtain trichlorosilane and silicon tetrachloride. All the silicon tetrachloride obtained by separation and purification is returned to the silicon tetrachloride hydrogenation reaction device 400.

[0062] In Example 1, the total consumption of hydrogen chloride fed into the system through the hydrogen chloride inlet 101 is 1000 kg / h (reaction amount), the total consumption of supplementary hydrogen is 165 kg / h, the total consumption of supplementary silicon tetrachloride is 60000 kg / h, the feeding rate of supplementary silicon powder is 1400 kg / h, and the production amount of trichlorosilane obtained at the trichlorosilane extraction outlet 703 is 57250 kg / h.

[0063] Example 2

[0064] The difference from Example 1 is that the compressed gas is not subjected to adsorption treatment, that is, the hydrogen chloride adsorption device 330 is not provided.

[0065] In Example 2, the total consumption of hydrogen chloride in the system is 1100 kg / h (reaction amount), the total consumption of supplementary hydrogen fed into the system through the supplementary hydrogen inlet is 168 kg / h, the total consumption of supplementary silicon tetrachloride fed into the system through the supplementary silicon tetrachloride inlet is 60000 kg / h, the feeding rate of supplementary silicon powder is 1400 kg / h, and the production amount of trichlorosilane obtained at the trichlorosilane extraction outlet 703 is 57250 kg / h.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that the second recycled hydrogen is not returned to the silicon tetrachloride hydrogenation reaction device 400, and the silicon tetrachloride obtained by separation and purification is not returned to the silicon tetrachloride hydrogenation reaction device 400, that is, the second recycled hydrogen outlet is not connected to the first hydrogen inlet 401, and the silicon tetrachloride extraction outlet 702 is not connected to the silicon tetrachloride inlet 402.

[0068] In Comparative Example 1, the total consumption of hydrogen chloride fed into the system through the hydrogen chloride inlet 101 is 1000 kg / h, the total consumption of supplementary hydrogen fed into the system through the supplementary hydrogen inlet is 3025 kg / h, the total consumption of supplementary silicon tetrachloride fed into the system through the supplementary silicon tetrachloride inlet is 80000 kg / h, the feeding rate of supplementary silicon powder is 1400 kg / h, and the production amount of trichlorosilane obtained at the trichlorosilane extraction outlet 703 is 57250 kg / h.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that except for retaining the shared product separation and purification unit 700 between the trichlorosilane synthesis reaction device 100 and the silicon tetrachloride hydrogenation reaction device 400, the rest are completely separated and there is no material connection, that is, the first silicon powder is not fed into the trichlorosilane synthesis reaction device 100, and the first recycled hydrogen is not fed into the silicon tetrachloride hydrogenation reaction device (the first recycled hydrogen inlet 403 is not connected to the first recycled hydrogen outlet 303).

[0071] In Comparative Example 2, the total consumption of hydrogen chloride fed into the system through the hydrogen chloride inlet 101 is 1000 kg / h, the total consumption of supplementary hydrogen fed into the system through the supplementary hydrogen inlet is 190 kg / h, the total consumption of supplementary silicon tetrachloride fed into the system through the supplementary silicon tetrachloride inlet is 60000 kg / h, the feeding rate of supplementary silicon powder is 1650 kg / h, and the production amount of trichlorosilane obtained at the trichlorosilane outlet 703 is 57250 kg / h.

[0072] Comparative Example 3

[0073] The difference from Example 1 is that the first silicon powder obtained at the first silicon powder outlet 502 is directly discharged as solid waste, and the silicon powder required for the trichlorosilane synthesis reaction device 100 is completely supplied by supplementary silicon powder.

[0074] In Comparative Example 3, the total consumption of hydrogen chloride fed into the system through the hydrogen chloride inlet 101 is 1000 kg / h (reaction amount), the total consumption of supplementary hydrogen fed into the system through the supplementary hydrogen inlet is 165 kg / h, the total consumption of supplementary silicon tetrachloride fed into the system through the supplementary silicon tetrachloride inlet is 60000 kg / h, the feeding rate of supplementary silicon powder is 1640 kg / h, and the production amount of trichlorosilane obtained at the trichlorosilane outlet 703 is 57250 kg / h.

[0075] Comparative Example 4

[0076] The difference from Example 1 is that the first recycled hydrogen is directly discharged as tail gas, and the hydrogen required for the silicon tetrachloride hydrogenation reaction device 400 is completely provided by supplementary hydrogen.

[0077] In Comparative Example 4, the total consumption of hydrogen chloride fed into the system through the hydrogen chloride inlet 101 is 1000 kg / h (reaction amount), the total consumption of supplementary hydrogen fed into the system through the supplementary hydrogen inlet is 190 kg / h, the total consumption of supplementary silicon tetrachloride fed into the system through the supplementary silicon tetrachloride inlet is 60000 kg / h, the feeding rate of supplementary silicon powder is 1400 kg / h, and the production amount of trichlorosilane obtained at the trichlorosilane outlet 703 is 57250 kg / h.

[0078] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0079] Generally, in the production process of polysilicon, for every 60000 kg of silicon tetrachloride reacted in the silicon tetrachloride hydrogenation reaction device 400, the trichlorosilane synthesis reaction device 100 needs to produce 1000 kg of trichlorosilane to supplement the loss of chlorine elements in the polysilicon production system.

[0080] Comparing Example 1 with Comparative Examples 1, 2 and 4, it can be seen that the consumption of supplementary hydrogen in Comparative Examples 1, 2 and 4 is greater. For the fluidized bed reactor, the circulation amount of the second recycled hydrogen is relatively large, about 13 to 17 times the reaction amount, and the circulation amount of silicon tetrachloride is about 1.3 to 1.4 times the reaction amount. Comparing Example 1 with Comparative Examples 2 and 3, it can be seen that the consumption of supplementary hydrogen and supplementary silicon powder in Comparative Examples 2 and 3 is greater. The technical solution in Example 1 can reduce the emission of three wastes and the cost of treating three wastes, increase the recycling ratio of material recovery, and reduce the consumption of hydrogen, chlorine and silicon. In summary, the above system of the present application realizes the efficient utilization of silicon powder, hydrogen and silicon tetrachloride by integrating the process flows of trichlorosilane synthesis reaction and silicon tetrachloride hydrogenation reaction, saves investment and operation costs, and reduces the consumption of raw materials at the same time.

[0081] Comparing Example 1 and 2, it can be seen that returning at least part of the recycled hydrogen chloride to the trichlorosilane synthesis reaction device 100 is beneficial to the efficient utilization of hydrogen chloride gas, reduces the consumption of hydrogen chloride input from the outside to the system, and is also beneficial to reducing the content of hydrogen chloride in the first recycled hydrogen, thereby being beneficial to improving the purity of the first recycled hydrogen.

[0082] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those described herein.

[0083] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A system for synthesizing trichlorosilane, characterized in that, The system for synthesizing trichlorosilane includes: A trichlorosilane synthesis reaction device (100) for reacting hydrogen chloride with first silicon powder to generate synthesis tail gas containing trichlorosilane. The trichlorosilane synthesis reaction device (100) is provided with a hydrogen chloride inlet (101), a first silicon powder inlet (102), and a synthesis tail gas outlet (103); A first gas-solid separation unit (200). The first gas-solid separation unit (200) is provided with a first gas inlet (201) and a first separated gas outlet (202); the first gas inlet (201) is communicated with the synthesis tail gas outlet (103); A first tail gas treatment unit (300) for enriching chlorosilane in the gas discharged from the first separated gas outlet (202) to obtain a first chlorosilane enrichment and a first recycled hydrogen. The first tail gas treatment unit (300) is provided with a second gas inlet (301), a first chlorosilane enrichment outlet (302), and a first recycled hydrogen outlet (303); the second gas inlet (301) is communicated with the first separated gas outlet (202); A silicon tetrachloride hydrogenation reaction device (400) for reacting silicon tetrachloride with hydrogen to generate hydrogenation tail gas containing trichlorosilane. The silicon tetrachloride hydrogenation reaction device (400) is provided with a first hydrogen inlet (401), a silicon tetrachloride inlet (402), a first recycled hydrogen inlet (403), a hydrogenation tail gas outlet (404), and an optional supplementary silicon powder inlet; the first recycled hydrogen inlet (403) is communicated with the first recycled hydrogen outlet (303); the supplementary silicon powder inlet is used to additionally introduce supplementary silicon powder into the silicon tetrachloride hydrogenation reaction device (400); A second gas-solid separation unit (500). The second gas-solid separation unit (500) is provided with a hydrogenation tail gas inlet (501), a first silicon powder outlet (502), and a second separated gas outlet (503); the hydrogenation tail gas inlet (501) is communicated with the hydrogenation tail gas outlet (404); the first silicon powder outlet (502) is communicated with the first silicon powder inlet (102) and is used to provide raw materials for the synthesis reaction of trichlorosilane; A second tail gas treatment unit (600) for enriching chlorosilane in the gas discharged from the second separated gas outlet (503) to obtain a second chlorosilane enrichment and a second recycled hydrogen. The second tail gas treatment unit (600) is provided with a third gas inlet (601), a second chlorosilane enrichment outlet (602), and a second recycled hydrogen outlet (603); the third gas inlet (601) is communicated with the second separated gas outlet (503); the second recycled hydrogen outlet (603) is communicated with the first hydrogen inlet (401); A product separation and purification unit (700) is used to separate and purify the first chlorosilane enriched material and / or the second chlorosilane enriched material to obtain silicon tetrachloride, trichlorosilane, and slag. The product separation and purification unit (700) is provided with a chlorosilane enriched material inlet (701), a silicon tetrachloride extraction outlet (702), a trichlorosilane extraction outlet (703), and a slag discharge outlet (704); the chlorosilane enriched material inlet (701) is communicated with the first chlorosilane enriched material outlet (302) and the second chlorosilane enriched material outlet (602); the silicon tetrachloride extraction outlet (702) is communicated with the silicon tetrachloride inlet (402).

2. The system for synthesizing trichlorosilane according to claim 1, wherein The first gas-solid separation unit (200) includes a multi-stage gas-solid separation device with gas phases connected in series, including a first primary gas-solid separation device (210) and a first secondary gas-solid separation device (220) with gas phases connected in series; The first primary gas-solid separation device (210) is provided with the first air inlet (201) and a second silicon powder outlet (203); the second silicon powder outlet (203) is communicated with the first silicon powder inlet (102) and is used to return at least part of the second silicon powder to the trichlorosilane synthesis reaction device (100); The first secondary gas-solid separation device (220) is provided with the first separated gas outlet (202) and a solid waste outlet (204); the solid waste outlet (204) is used to discharge the remaining silicon powder.

3. The system for synthesizing trichlorosilane according to claim 1, wherein The silicon tetrachloride hydrogenation reaction device (400) is further provided with a second silicon powder inlet. The second gas-solid separation unit (500) includes a multi-stage gas-solid separation device with gas phases connected in series, including a second primary gas-solid separation device (510) and a second secondary gas-solid separation device (520) with gas phases connected in series; The second primary gas-solid separation device (510) is provided with the hydrogenation tail gas inlet (501) and a third silicon powder outlet (504); the third silicon powder outlet (504) is communicated with the second silicon powder inlet and is used to return at least part of the third silicon powder to the silicon tetrachloride hydrogenation reaction device (400); The second secondary gas-solid separation device (520) is provided with the first silicon powder outlet (502) and the second separated gas outlet (503).

4. The system for synthesizing trichlorosilane according to any one of claims 1 to 3, characterized in that, The first tail gas treatment unit (300) includes: A first condensation device (310), the first condensation device (310) is provided with the second air inlet (301), the first chlorosilane enriched material outlet (302), and a first condensed gas outlet (304); A first compression device (320), the first compression device (320) is provided with a first condensed gas inlet (305) and a compressed gas outlet (306); the first condensed gas inlet (305) is communicated with the first condensed gas outlet (304); Hydrogen chloride adsorption device (330), the hydrogen chloride adsorption device (330) is provided with a compressed gas inlet (307), the first recovered hydrogen outlet (303) and a recovered hydrogen chloride outlet (308); the recovered hydrogen chloride outlet (308) is communicated with the hydrogen chloride inlet (101).

5. The system for synthesizing trichlorosilane according to any one of claims 1 to 3, characterized in that, The second tail gas treatment unit (600) includes: A second condensation device (610), the second condensation device (610) is provided with the third inlet (601), the second chlorosilane enriched product outlet (602) and a second condensed gas outlet (604); A second compression device (620), the second compression device (620) is provided with a second condensed gas inlet (605) and the second recovered hydrogen outlet (603); the second condensed gas inlet (605) is communicated with the second condensed gas outlet (604).

6. The system for synthesizing trichlorosilane according to claim 5, wherein, The third inlet (601) is communicated with the second separated gas outlet (503) through a separated gas delivery pipeline; the system for synthesizing trichlorosilane further includes a heat exchange device; the heat exchange device is arranged on the separated gas delivery pipeline for cooling the second separated gas.

7. The system for synthesizing trichlorosilane according to claim 1, wherein The system for synthesizing trichlorosilane further includes a hydrogen chloride synthesis device for reacting chlorine and hydrogen to obtain hydrogen chloride, the hydrogen chloride synthesis device is provided with a chlorine inlet, a second hydrogen inlet and a hydrogen chloride outlet; the hydrogen chloride outlet is communicated with the hydrogen chloride inlet (101).

8. The system for synthesizing trichlorosilane according to claim 2, wherein The first primary gas-solid separation device (210) is used for separating silicon powder with a particle size > 1 μm; the first secondary gas-solid separation device (220) is used for separating silicon powder with a particle size of 1 - 10 μm.

9. The system for synthesizing trichlorosilane according to claim 3, wherein The second primary gas-solid separation device (510) is selected from a cyclone separator for separating silicon powder with a particle size ≥ 10 μm; The second secondary gas-solid separation device (520) is selected from a filter with a metal sintered filter element for separating silicon powder with a particle size < 10 μm and ≥ 1 μm.

10. The system for synthesizing trichlorosilane according to claim 1, wherein, The product separation and purification unit (700) includes: A solid-liquid separation device (710) for performing solid-liquid separation treatment on the first chlorosilane enriched product and / or the second chlorosilane enriched product to obtain a liquid-phase product and slag, the solid-liquid separation device (710) is provided with a chlorosilane enriched product inlet (701), a liquid-phase product outlet (705) and a slag discharge port (704); A rectification device (720) for separating and purifying the liquid-phase product to obtain trichlorosilane and silicon tetrachloride, the rectification device (720) is provided with a liquid-phase product inlet (706), a silicon tetrachloride extraction outlet (702) and a trichlorosilane extraction outlet (703).

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