Silicon consumption reduction process suitable for polycrystalline silicon production and polycrystalline silicon production process

Abstract

The invention belongs to the technical field of polycrystalline silicon production, and discloses a silicon consumption reduction process suitable for polycrystalline silicon production and a polycrystalline silicon production process, and the silicon consumption reduction process at least comprises the following operations: collecting waste gas from a rectification process, a recovery process, a reduction process, a trichlorosilane synthesis process and a cold hydrogenation process; feeding a material obtained by pressurizing and cryogenic cooling the waste gas into a system rectifying tower for treatment; the method comprises the following steps: feeding hydrogen chloride gas produced by a hydrogen chloride synthesis furnace in a trichlorosilane synthesis process into a high-boiling cracking kettle of a system to participate in catalytic cracking reaction of high-boiling residues; and fine silicon powder overflowing from the cold hydrogenation fluidized bed reaction furnace is collected for secondary reuse. On the basis of the existing polycrystalline silicon production process flow, different wastes of silicon and silicon compounds are effectively recovered and utilized, so that the silicon consumption and chlorine consumption of the system can be effectively reduced, and the aims of saving energy, reducing consumption and reducing the production cost of polycrystalline silicon are fulfilled.

Description

Technical Field

[0001] The present invention relates to a silicon consumption reduction process and a polysilicon production process suitable for polysilicon production, and specifically relates to a control method for reducing silicon consumption by recycling waste silicon and its compounds during the polysilicon production process, and a polysilicon production process using the control method, belonging to the technical field of polysilicon production. Background Art

[0002] Based on the current competitive situation of the photovoltaic industry at home and abroad, in order to meet the changes in the polysilicon market demand in the photovoltaic industry chain, the competition in the polysilicon industry has continued to intensify, and it is necessary to maintain competitiveness by reducing costs and improving efficiency. Therefore, for polysilicon companies, the high cost of polysilicon production will be a major challenge faced by the company's sustainable development.

[0003] In the polysilicon production process, trichlorosilane (SiHCl3, TCS) is the main production raw material, and its cost control directly affects the entire polysilicon production cost. Currently, there are three methods for synthesizing TCS:

[0004] Cold hydrogenation: Si+H2+SiCl4→SiHCl3(550℃)

[0005] Anti-disproportionation: SiH2Cl2+SiCl4→SiHCl3(60℃)

[0006] Direct synthesis: Si+HCl→SiHCl3 (280-320℃)

[0007] In industrial production, cold hydrogenation is mainly used to make silicon powder (Si) contact with SiCl4 and H2 in a synthesis furnace to synthesize SiHCl3. A large amount of silicon powder is consumed in the synthesis process. In the prior art, the waste silicon powder generated by the synthesis furnace is often screened and then recycled. Although it can reduce the consumption of silicon powder raw materials to a certain extent, it is still necessary to purchase a large amount of new silicon powder as a supplement. These consumed silicon powders may usually exist in synthetic materials or chlorosilane materials in other ways, and exist in various links of polysilicon production through the recycling of materials. Therefore, in order to cope with the increasingly fierce competition in polysilicon, it is very important to provide a method that can realize comprehensive recovery of silicon materials in the polysilicon production process to reduce silicon consumption for high cost control of polysilicon production. Summary of the invention

[0008] The purpose of the present invention is to provide a silicon consumption reduction process and a polysilicon production process suitable for polysilicon production. On the basis of the existing polysilicon production process, the waste in the three states of "solid", "liquid" and "gas" of silicon and silicon compounds is effectively recovered and utilized, which can effectively reduce the silicon consumption and chlorine consumption of the system, achieve energy saving and consumption reduction, and reduce the production cost of polysilicon.

[0009] The present invention is implemented by the following technical solution: A silicon consumption reduction process suitable for polysilicon production, comprising at least the following operations:

[0010] Ⅰ. Collect the waste gas from the distillation process, recovery process, reduction process, trichlorosilane synthesis process and cold hydrogenation process, and send the material obtained by pressurizing the waste gas and deep cooling it into the system distillation tower for treatment;

[0011] Ⅱ. The hydrogen chloride gas produced by the hydrogen chloride synthesis furnace in the trichlorosilane synthesis process is sent to the high-boiling cracking kettle of the system to participate in the catalytic cracking reaction of high-boiling substances;

[0012] III. Collecting the fine silicon powder overflowing from the cold hydrogenation fluidized bed reactor, and sending the fine silicon powder as a reaction raw material to the trichlorosilane synthesis furnace;

[0013] IV. Collect the fine silicon powder overflowing from the cold hydrogenation fluidized bed reactor, mix the fine silicon powder with the reduction by-product silicon powder, smelt it, and then crush it into raw silicon powder for use in the hydrogenation furnace.

[0014] In the operation I,

[0015] Waste gas from the distillation process includes the venting waste gas from the distillation tower, raw material tank, product liquid tank and intermediate tank;

[0016] The waste gas from the recovery process includes the waste gas generated by the shutdown and replacement of the reduction tail gas compressor;

[0017] The waste gas from the reduction process includes the waste gas generated when the reduction furnace is running and shut down;

[0018] The waste gas from the trichlorosilane synthesis process includes the venting waste gas from the hydrogen chloride synthesis furnace, the waste gas generated by the replacement of the trichlorosilane synthesis furnace during shutdown, and the waste gas generated by the replacement before the silicon powder is discharged from the silicon powder receiving tank;

[0019] The waste gas from the cold hydrogenation process includes the waste gas generated by the replacement before the silicon powder is discharged from the silicon powder receiving tank.

[0020] In the operation I, the waste gas includes chlorosilane, hydrogen chloride and hydrogen.

[0021] In the operation I, the collected exhaust gas is pressurized to 0.43-0.52 MPa by a compressor and then sent to a cryogenic heat exchanger for cryogenic cooling.

[0022] In the operation II, hydrogen chloride gas is introduced from the bottom of the high-boiling cracking kettle of the system, and the cracking catalyst is introduced from the top of the high-boiling cracking kettle of the system to carry out catalytic cracking reaction with the high-boiling substances in the kettle.

[0023] In the operation IV, the reduced by-product silicon powder comes from the post-treatment dust collector.

[0024] The particle sizes of the fine silicon powder and the reduced by-product silicon powder are controlled to be 40 to 110 μm, and the mass ratio of the fine silicon powder to the reduced by-product silicon powder is controlled to be 1:1 to 1:2.

[0025] In the operation III, the trichlorosilane synthesis furnace is an external jacket cooling structure, and the temperature of the trichlorosilane synthesis furnace is controlled to be 320-360°C.

[0026] The number of nozzles in the trichlorosilane synthesis furnace is 140, the diameter of the nozzle is 18 mm, and four small holes with a diameter of 4 mm are evenly distributed on the side of the nozzle.

[0027] Furthermore, the present invention also provides a polysilicon production process using the above-mentioned silicon consumption reduction process.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) The present invention can realize the recovery of chlorosilane-containing exhaust gas from the distillation, recovery, reduction, synthesis, cold hydrogenation and other devices in the production of polysilicon. By pressurizing the exhaust gas and then reusing it, the recovery rate of chlorosilane can be improved, and the existing distillation device can be used for purification and reuse, thereby achieving the effect of reducing silicon consumption and chlorine consumption in the system.

[0030] (2) The present invention can improve the cracking efficiency of polychlorosilanes in the slurry residue by sending the hydrogen chloride produced by hydrogen chloride synthesis to high-boiling cracking, thereby improving the recovery rate of chlorosilanes and reducing the loss of chloride hydrolysis, thereby reducing the silicon consumption and chlorine consumption of the system.

[0031] (3) The present invention reuses the fine silicon powder overflowing from the cold hydrogenation fluidized bed reactor for a second time. A portion of the fine silicon powder is reacted in a special trichlorosilane synthesis furnace to generate trichlorosilane and tetrachlorosilane. The other portion is mixed with the reduced by-product silicon powder and then smelted and then used in the hydrogenation furnace to produce a gas containing trichlorosilane. After the secondary reuse, the comprehensive utilization rate of the silicon powder can be improved and the silicon consumption of the system can be further reduced.

[0032] (4) In the treatment steps (1) to (3) above, the present invention can also reduce the content of silicon and chlorine in the wastewater by recovering the waste gas, polychlorosilane and fine silicon powder, thereby further reducing the wastewater treatment load, which is beneficial to reducing the wastewater treatment cost, reducing the industrial water consumption of the wastewater treatment device, and reducing the wastewater treatment reagents. At the same time, after the chloride ions entering the wastewater are reduced, the treatment load of the triple-effect evaporator is reduced, the steam usage is reduced, and the purpose of energy saving and consumption reduction is achieved.

[0033] In summary, based on the existing polysilicon production process, the present invention aims at the effective recovery and utilization of wastes in the three states of "solid", "liquid" and "gas" of silicon and silicon compounds, which can effectively reduce the silicon consumption and chlorine consumption of the system, further reduce the polysilicon production cost, and is conducive to the sustainable development of polysilicon production.

[0034] The "solid" mentioned in the present invention refers to fine silicon powder and reduction by-product silicon powder from the post-treatment dust collector; the "liquid" mentioned refers to polychlorosilane in the residual liquid of slurry; and the "gas" mentioned refers to the waste gas containing chlorosilane in the distillation, recovery, reduction, synthesis, cold hydrogenation and other devices in the production of polysilicon. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0036] The invention objectives, technical solutions and beneficial effects of the present invention are further described in detail below.

[0037] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the claimed invention, and unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs.

[0038] The present invention finds through the existing polysilicon production process that the cost factor affecting the production of polysilicon is mainly the consumption of silicon and silicon compounds in the system. To this end, the present invention analyzes the main components of the leaching waste gas in the system and finds that the main components of the leaching waste gas are SiCl4, SiHCl3, SiH2CL2, HCl, H2, N2 and a small amount of metal chloride. If the recovery of silicon, silicon compounds and chlorine in the leaching waste gas can be achieved, then the reduction of silicon consumption and chlorine consumption in the system can be achieved, and the environmental pressure of the system can be improved, and the emission of silane waste gas can be reduced. In order to further reduce the silicon consumption and chlorine consumption, the present invention also specifically recovers the fine silicon powder overflowed from the cold hydrogenation, and sends the hydrogen chloride produced by the hydrogen chloride synthesis furnace to the high-boiling cracking kettle, which can reduce the loss of silicon powder and chloride hydrolysis, thereby reducing the silicon consumption and chlorine consumption.

[0039] Therefore, for the present invention, how to reasonably and effectively solve the recycling of leaching waste gas, overflowed fine silicon powder and loss of chloride hydrolysis in the high-boiling cracking kettle in the system, and thereby reduce the overall silicon consumption and chlorine consumption of the system is very critical. In order to achieve the reduction of silicon consumption and chlorine consumption, the main technical solutions of the present invention can be summarized as follows:

[0040] (I) Reuse of leaching waste gas

[0041] The leaching waste gas in the existing polysilicon system mainly comes from the chlorosilane-containing waste gas of the distillation process, the recovery process, the reduction process, the trichlorosilane synthesis process and the cold hydrogenation process. The present invention first collects the waste gas from these processes, wherein the waste gas from the distillation process includes the venting waste gas of the distillation tower, the raw material tank, the product liquid tank and the intermediate tank; the waste gas from the recovery process includes the waste gas generated by the shutdown and replacement of the reduction tail gas compressor; the waste gas from the reduction process includes the waste gas generated when the reduction furnace is running and shut down; the waste gas from the trichlorosilane synthesis process includes the venting waste gas of the hydrogen chloride synthesis furnace, the waste gas generated by the shutdown and replacement of the trichlorosilane synthesis furnace, and the waste gas generated by the replacement before the silicon powder is discharged from the silicon powder receiving tank.

[0042] The above-mentioned waste gas collected mainly contains 1.5-2% chlorosilane (SiCl4, SiHCl3, SiH2CL2), 0.2-0.6% hydrogen chloride and 20-50% hydrogen. Then, the collected waste gas is pressurized to 0.43-0.52Mpa by a compressor, and then sent to a cryogenic heat exchanger for deep cooling. The cryogenic temperature is controlled at -10--20°C, which is used to recover the chlorosilane (SiCl4, SiHCl3, SiH2CL2) in the waste gas and then sent to the existing distillation tower of the system for distillation separation. Among them, trichlorosilane can be directly used; dichlorosilane can enter the anti-disproportionation device to react to generate trichlorosilane; silicon tetrachloride can enter the cold hydrogenation device to react to generate trichlorosilane. Through recycling, the consumption of trichlorosilane in the production of polysilicon products is reduced. The main components of trichlorosilane are silicon and chlorine, so it can play a role in reducing the consumption of silicon and chlorine. The gases that have not been deep-cooled are mainly small amounts of HCl, H2 and N2, which can be treated through the system's existing waste gas washing device, effectively reducing the environmental pressure of the device.

[0043] (II) Recycling of overflowed fine silicon powder

[0044] The conventional method for treating fine silicon powder overflowing from a cold hydrogenated fluidized bed reactor is to send it to a three-waste treatment after hydrolysis, and then send it to a cement company as a raw material for use after neutralization, sedimentation, and filter pressing in the three-waste device. The problems faced include: the hydrolyzed silicon powder reacts with alkaline lime milk in the three-waste treatment device to produce hydrogen, which poses a certain safety risk. In addition, when transporting wastewater containing silicon powder solid particles, the fluidity is poor, which easily causes pipeline blockage and increases the maintenance frequency. At the same time, when transporting wastewater containing silicon powder solid particles through a pipeline, the pipeline and the delivery pump are worn, etc. Therefore, the present invention collects the fine silicon powder overflowing from the cold hydrogenated fluidized bed reactor and reuses the fine silicon powder for a second time.

[0045] Specifically, cold hydrogenation is to react silicon tetrachloride with hydrogen gas in a hydrogenation furnace (fluidized bed reactor) to generate trichlorosilane. The particle size of silicon powder keeps getting smaller during the reaction, and it is carried out of the hydrogenation furnace as the gas flows in the hydrogenation furnace. The silicon powder carried out of the hydrogenation furnace cannot be reused in cold hydrogenation due to its small particle size (fine silicon powder of 60-135 mesh accounts for about 40%; raw silicon powder of 60-200 mesh accounts for about 22%). Through screening, the raw silicon powder can be screened out and reused in the hydrogenation furnace. The remaining fine silicon powder can be mixed with the reduced by-product silicon powder from the post-treatment dust collector, smelted, and then crushed into raw silicon powder (40-110μm) and sent to the trichlorosilane synthesis furnace. During production, the mass ratio of fine silicon powder to reduced by-product silicon powder is controlled at 1:1-1:2, and then the silicon powder with smaller particle size is remade into raw silicon powder through smelting. In the hydrogenation furnace, it replaces part of the raw silicon powder to reduce silicon consumption. At the same time, according to the amount of by-product silicon powder reduced, part of the fine silicon powder is used for smelting, and the remaining fine silicon powder is directly sent to the trichlorosilane (TCS) synthesis furnace for use, replacing the TCS synthesis raw silicon powder.

[0046] In order to meet the TCS synthesis process after the fine silicon powder is recycled, the present invention redesigns a trichlorosilane synthesis furnace, and designs the trichlorosilane synthesis furnace as an outer jacket cooling structure. According to the composition of the raw silicon powder, the heat exchange area of ​​the equipment can be ensured to meet the use. At the same time, the number of nozzles of the trichlorosilane synthesis furnace is set to 140, the diameter of the nozzle is 18 mm, and four small holes with a diameter of 4 mm are evenly distributed on the side of the nozzle, so that the gas volume distribution can be reasonably controlled to avoid the channel flow phenomenon during operation, resulting in impurity accumulation and reduced conversion rate. Then, by increasing the head of the hot water pump and reducing the jacket water vaporization rate, the temperature in the furnace is controlled at 320-360° C., which can effectively promote the increase of trichlorosilane production and reduce the scouring of the upper pipeline of the jacket by steam and water. By adding a high-efficiency cyclone, the silicon powder utilization rate can be further increased from 80% to 92%, and the utilization rate of the fine silicon powder is maximized.

[0047] (III) Control of chloride hydrolysis loss in high boiling cracking kettle

[0048] The process principle of high-boiling cracking is that under the action of a catalyst, hydrogen chloride cracks the silicon-silicon bond in the high-boiling product (the high-boiling product in the cracking reaction refers to hexachlorodisilane Si2Cl6), and the hydrogen atoms and chloride ions in the hydrogen chloride are added to two silicon atoms respectively to generate trichlorosilane and silicon tetrachloride. The hydrogen chloride used for high-boiling cracking in the prior art comes from hydrogen chloride produced as a byproduct of polysilicon production. The purity of hydrogen chloride is low (50-60% purity), and the amount produced changes with the change of polysilicon production load. The present invention changes the hydrogen chloride from high-boiling cracking to be supplied by the hydrogen chloride synthesis process. The purity of the hydrogen chloride can reach 80-85%, and the flow rate can be adjusted, which can improve the cracking efficiency and reduce the loss of chloride hydrolysis. The waste gas (chlorosilane and hydrogen chloride) generated by high-boiling cracking is sent to cold hydrogenation for continued use after being pressurized by a compressor.

[0049] In the present invention, the hydrogen chloride gas produced by the hydrogen chloride synthesis furnace in the trichlorosilane synthesis process is introduced from the bottom of the system high-boiling cracking kettle, and the cracking catalyst is introduced from the top of the system high-boiling cracking kettle to carry out catalytic cracking reaction with the high-boiling substances in the kettle. After the high-boiling substances are cracked, silicon tetrachloride and trichlorosilane are generated, and steam is introduced into the cracking tank to evaporate the low-boiling silicon tetrachloride and trichlorosilane. The evaporated silane is cooled to a buffer tank by a water cooler and deep cooling, and then returned to the silicon tetrachloride high-boiling tower for purification again. Due to the introduction of hydrogen chloride, the yield of cracking products can be improved, and the trichlorosilane in the cracking product is used as the raw material of the reduction process after rectification and purification, and silicon tetrachloride is used as the raw material of the cold hydrogenation process. Trichlorosilane is produced after the cold hydrogenation reaction, thereby reducing the loss of chloride hydrolysis during cracking, and further reducing silicon consumption and chlorine consumption.

[0050] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0051] Embodiment 1:

[0052] This embodiment relates to a polysilicon production process using the above-mentioned silicon consumption reduction process, specifically including the recycling of leaching waste gas, the recycling of overflowed fine silicon powder, and the process improvement of controlling the hydrolysis loss of chloride in the high-boiling cracking kettle. In the actual production process, the waste gas treatment amount and the amount of hydrogen chloride, etc., are reasonably adjusted according to the actual production needs. The parameters and data that need to be specifically controlled are as follows (the remaining control parameters only need to be controlled within the required range):

[0053] The screened fine silicon powder is mixed with the reduced by-product silicon powder for smelting and then crushed into raw silicon powder of 40-110 mesh and then sent to the hydrogenation furnace for use, wherein the mass ratio of the fine silicon powder to the reduced by-product silicon powder is controlled at 1:1.

[0054] Embodiment 2:

[0055] This embodiment also relates to a polysilicon production process using the above-mentioned silicon consumption reduction process, and the difference between this embodiment and the first embodiment is only the difference in the following control parameters:

[0056] The screened fine silicon powder is mixed with the reduced by-product silicon powder for smelting and then crushed into raw silicon powder of 40-110 mesh and then sent to the hydrogenation furnace for use, wherein the mass ratio of the fine silicon powder to the reduced by-product silicon powder is controlled at 1:2.

[0057] Embodiment 3:

[0058] This embodiment also relates to a polysilicon production process using the above-mentioned silicon consumption reduction process, and the difference between this embodiment and the first embodiment is only the difference in the following control parameters:

[0059] The screened fine silicon powder is mixed with the reduced by-product silicon powder for smelting and then crushed into raw silicon powder of 40-110 mesh and then sent to the hydrogenation furnace for use, wherein the mass ratio of the fine silicon powder to the reduced by-product silicon powder is controlled at 1:1.

[0060] According to the polysilicon production process of Example 1, the existing 20,000-ton polysilicon production line is transformed. Figure 1 After the equipment installation and pipeline transformation of the process flow, a polysilicon production trial run was carried out for three months. The trichlorosilane consumption, cold hydrogenated trichlorosilane synthesis benefits, silicon powder saving benefits, high boiling cracking efficiency improvement benefits, etc. during the trial run were compared and analyzed with the existing polysilicon production process.

[0061] (1) Chlorosilane saving benefits

[0062] In order to meet the requirements of the modified process flow, the polysilicon production line added a compressor and matched deep cooling and adsorption devices in the waste gas leaching process. The recovery amount and benefits of chlorosilane (main components are 50% trichlorosilane and 50% silicon tetrachloride) before and after the modification are shown in Table 1 below.

[0063] Table 1 Comparison of chlorosilane saving benefits before and after transformation

[0064]

[0065] As can be seen from Table 1, the present invention can increase the output of trichlorosilane and silicon tetrachloride in the trichlorosilane synthesis furnace by reducing the silicon consumption and chlorine consumption of the polysilicon production system, and can create a profit of 9.9842 million yuan for polysilicon production.

[0066] The present invention can further reduce the consumption of lime powder in the system, save 1549 tons of lime per year, and save 900,000 yuan in raw material costs.

[0067] (2) Silica powder saving benefits

[0068] According to the amount of fine silicon powder produced as a byproduct of reduction, during the trial operation, part of the fine silicon powder overflowing from the cold hydrogenation fluidized bed reactor was used in the hydrogenation furnace after being melted with the byproduct silicon powder in proportion to the reduction, and the trichlorosilane synthesis furnace was transformed, and the other part of the fine silicon powder was directly reused. This was compared with the method of using new silicon powder before the transformation, as shown in Table 2 below.

[0069] Table 2 Comparison of silicon powder saving benefits before and after transformation

[0070] Dosage(t / a) Silicon powder utilization rate Unit price (Yuan) Total cost (ten thousand yuan) Recycling of fine silicon powder 1533.42 92％ 11340 1599.79 Use new silica powder 1485 95％ 14000 1975.05 change 0.42 3％ 2660 375.26

[0071] As can be seen from Table 2, the present invention reuses the fine silicon powder under the sieve, and the price of the fine silicon powder under the sieve is 81% of the normal silicon powder price, which is 11,340 yuan / ton, which is 2,660 yuan lower than the price of new silicon powder, and can create a benefit of 3.7526 million yuan.

[0072] (3) High boiling cracking efficiency improvement

[0073] The present invention utilizes a hydrogen chloride synthesis furnace to supply hydrogen chloride gas to a high-boiling pyrolysis reactor, which can reduce the loss of chlorosilane during pyrolysis. Before the transformation, polysilicon is used to produce by-product hydrogen chloride. After the transformation, the high-boiling pyrolysis efficiency can be improved by changing the supply of hydrogen chloride gas, while reducing the loss of chlorosilane, as shown in Table 3 below.

[0074] Table 3 Data on high boiling cracking efficiency and saving of chlorosilane after transformation

[0075] Silane loss t / d Annual silane loss t / y Price (Yuan / ton) Benefit (ten thousand yuan) High boiling cracking 3 990.00 4080.00 403.92 Gas phase recovery 0.8 264.00 4080.00 107.71

[0076] As can be seen from Table 3, high-boiling cracking efficiency improvement can save 3 t / d of chlorosilane, and gas-phase silane recovery can save 0.8 t / d of chlorosilane. In total, 1,254 tons of chlorosilane can be saved per year. The price of silane is calculated at 4,080 yuan per ton, which can reduce costs by 5.116 million yuan.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A silicon consumption reduction process suitable for polysilicon production, characterized in that: At least the following operations are included: Ⅰ. Collect the waste gas from the distillation process, recovery process, reduction process, trichlorosilane synthesis process and cold hydrogenation process, and send the material obtained by pressurizing the waste gas and deep cooling it into the system distillation tower for treatment; Ⅱ. The hydrogen chloride gas produced by the hydrogen chloride synthesis furnace in the trichlorosilane synthesis process is sent to the high-boiling cracking kettle of the system to participate in the catalytic cracking reaction of high-boiling substances; III. Collecting the fine silicon powder overflowing from the cold hydrogenation fluidized bed reactor, and sending the fine silicon powder as a reaction raw material to the trichlorosilane synthesis furnace; IV. Collect the fine silicon powder overflowing from the cold hydrogenation fluidized bed reactor, mix the fine silicon powder with the reduction by-product silicon powder, smelt it, and then crush it into raw silicon powder for use in the hydrogenation furnace.

2. The silicon consumption reduction process according to claim 1, characterized in that: In the operation I, Waste gas from the distillation process includes the venting waste gas from the distillation tower, raw material tank, product liquid tank and intermediate tank; The waste gas from the recovery process includes the waste gas generated by the shutdown and replacement of the reduction tail gas compressor; The waste gas from the reduction process includes the waste gas generated when the reduction furnace is running and shut down; The waste gas from the trichlorosilane synthesis process includes the venting waste gas from the hydrogen chloride synthesis furnace, the waste gas generated by the replacement of the trichlorosilane synthesis furnace during shutdown, and the waste gas generated by the replacement before the silicon powder is discharged from the silicon powder receiving tank; The waste gas from the cold hydrogenation process includes the waste gas generated by the replacement before the silicon powder is discharged from the silicon powder receiving tank.

3. The silicon consumption reduction process according to claim 1, characterized in that: In the operation I, the waste gas includes chlorosilane, hydrogen chloride and hydrogen.

4. The silicon consumption reduction process according to claim 1, characterized in that: In the operation I, the collected exhaust gas is pressurized to 0.43-0.52 MPa by a compressor and then sent to a cryogenic heat exchanger for cryogenic cooling.

5. The silicon consumption reduction process according to claim 1, characterized in that: In the operation II, hydrogen chloride gas is introduced from the bottom of the high-boiling cracking kettle of the system, and the cracking catalyst is introduced from the top of the high-boiling cracking kettle of the system to carry out catalytic cracking reaction with the high-boiling substances in the kettle.

6. The silicon consumption reduction process according to claim 1, characterized in that: In the operation IV, the reduced by-product silicon powder comes from the post-processing dust collector.

7. The silicon consumption reduction process according to claim 6, characterized in that: The particle sizes of the fine silicon powder and the reduced by-product silicon powder are controlled to be 40 to 110 μm, and the mass ratio of the fine silicon powder to the reduced by-product silicon powder is controlled to be 1:1 to 1:

2.

8. The silicon consumption reduction process according to claim 1, characterized in that: In the operation III, the trichlorosilane synthesis furnace is an external jacket cooling structure, and the temperature of the trichlorosilane synthesis furnace is controlled to be 320-360°C.

9. The silicon consumption reduction process according to claim 6, characterized in that: The number of nozzles in the trichlorosilane synthesis furnace is 140, the diameter of the nozzle is 18 mm, and four small holes with a diameter of 4 mm are evenly distributed on the side of the nozzle.

10. A polysilicon production process using the silicon consumption reduction process according to any one of claims 1 to 9.

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