Improved siemens method and fluidized bed method combined production process and apparatus

Abstract

An improved Siemens method and fluidized bed method combined production process and apparatus. According to the process, reaction byproducts can be recycled, so that the utilization rate of raw materials can be greatly increased. By means of a steam thermal energy circulation system, steam in a polycrystalline silicon production process can generate high-temperature steam through a waste heat recovery apparatus, meeting steam energy consumption required by an apparatus in a downstream granular silicon production process, and reducing investment in the heat supply apparatus required by the downstream granular silicon production process; steam in the production process of granular silicon of a downstream fluidized bed reactor (FBR) can also generate high-temperature steam through the waste heat recovery apparatus, and the high-temperature steam circulates into a hydrochlorination fluidized bed for reaction heating. Compared with independent and separate construction of granular silicon and polycrystalline silicon productivity projects of the same scale, use of the apparatus and the process can greatly reduce reaction materials and energy consumption.

Description

Improved Siemens process and fluidized bed process combined production process and device Technical Field

[0001] The present invention belongs to the field of new energy material preparation, and specifically relates to a combined production process and device of an improved Siemens method and a fluidized bed method. Background Art

[0002] In line with green and sustainable development strategies, solar photovoltaic power generation technology has become one of the key technologies in the current development of green energy. Polysilicon is one of the primary raw materials for solar photovoltaic power generation. Currently, the mainstream technologies for polysilicon production are the modified Siemens process using trichlorosilane as the raw material and the fluidized bed process using silane as the raw material. During the polysilicon production process, the purity of the raw trichlorosilane must be controlled to produce high-purity polysilicon with a purity of 99.9999%-99.9999999% required for photovoltaic power generation, thereby growing polysilicon rods that meet the requirements.

[0003] The characteristic of the fluidized bed method is that in a fluidized bed reactor (FBR), small-particle granular polysilicon is used as a deposition carrier (seed crystal), the reaction temperature is 500-1200°C, and the reaction medium is silane or chlorosilane and hydrogen, which drives the seed crystal to float and tumble in the reaction medium gas. The raw material undergoes thermal decomposition reaction or reduction reaction on the surface of the seed crystal to generate elemental silicon, and the generated elemental silicon is deposited on the surface of the granular silicon seed crystal. As the reaction proceeds, the particle size of the granular silicon seed crystal gradually increases until it reaches the specified size, and is finally extracted in the form of millimeter-level granular polysilicon.

[0004] In addition, the electronic information industry currently mainly uses electronic-grade polysilicon as raw material, and the requirements for electronic-grade polysilicon raw materials are more stringent. The purity of polysilicon needs to reach 99.9999999999%-99.999999999999% purity.

[0005] Granular silicon production technology doesn't fully achieve a closed-loop material circulation system, so a certain amount of waste gas is generated during the production process. This waste gas primarily originates from silane production and separation, silicon tetrachloride cold hydrogenation, and silane purification. This process waste gas primarily contains chlorosilane, silane, SiCl₄, HCl, H₂, and N₂.

[0006] Granular silicon and polysilicon, the core raw materials for photovoltaic manufacturing, are an accelerator for achieving the "dual carbon" goals. Currently, electricity consumption is a significant cost in the production of high-purity crystalline silicon and silicon wafers. The overall electricity consumption during polysilicon production accounts for over 35% of the manufacturing cost. No prior art technology has yet publicly demonstrated a method for combining the modified Siemens process and the FBR fluidized bed process to produce electronic-grade polysilicon and granular silicon, significantly reducing energy consumption through material and heat circulation.

[0007] Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the defects of the existing technology and provide a granular silicon production method and system that can recycle reaction by-products and improve raw material utilization.

[0009] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0010] A combined production process of improved Siemens process and fluidized bed process:

[0011] (1) Hydrochlorination: Silicon powder, hydrogen chloride, silicon tetrachloride and hydrogen are used as raw materials to react and prepare TCS (SiHCl3);

[0012] (2) TCS purification: The TCS prepared in step (1) is purified by adsorption and distillation to remove impurities;

[0013] (3) TCS reduction reaction: The TCS (SiHCl3) prepared in step (2) is passed into a modified Siemens reduction furnace.

[0014] In the process, it is used as raw material to produce polysilicon through reduction;

[0015] (4) Recover and purify the reduced tail gas from the production process of the improved Siemens reduction furnace to recover DCS (SiH2Cl2)

[0016] and TCS, STC, HCl, H2;

[0017] (5) The DCS (SiH2Cl2) / TCS recovered from the Siemens process in step (4) is passed through a disproportionation device to perform

[0018] Disproportionation reaction produces silane SiH4;

[0019] (6) The silane prepared in step (5) and the hydrogen recovered in step (4) are introduced into the FBR fluidized bed reactor as raw gas to generate product granular silicon by heterogeneous deposition.

[0020] In one embodiment, the STC and DCS purified by the TCS refining and purification device in step (2) can be circulated to the hydrochlorination fluidized bed and the disproportionation device respectively.

[0021] In one embodiment, the hydrogen obtained by purification in step (4) is recovered to the hydrochlorination reactor and / or the fluidized bed reactor for recycling.

[0022] In one embodiment, the tail gas of the FBR fluidized bed reactor is passed through a gas-solid separation device such as a cyclone to remove silicon powder, and the resulting hydrogen is recycled to the hydrochlorination reactor for the production of trichlorosilane.

[0023] In one embodiment, the reduced tail gas in step (3), after recovery and purification, the DCS and TCS can be used for the disproportionation reaction in step (5) to produce silane.

[0024] In one embodiment, the reduction tail gas in step (3) can be recycled to the hydrochlorination reactor after recovery and purification of silicon tetrachloride.

[0025] In one embodiment, the steam produced as a by-product of the reduction furnace in step (3) is circulated to the disproportionation reaction device in step (5) and used for heating the silane gas production device.

[0026] In one embodiment, the steam produced as a by-product in the FBR fluidized bed reactor in step (6) is circulated to the hydrochlorination unit in step (1) for heating.

[0027] In one embodiment, the raw material for the disproportionation reaction in step (5) can also be TCS (SiHCl3) prepared in step (1);

[0028] In one embodiment, the disproportionation reaction in step (5) produces silane, which can be compressed to obtain high-pressure silane gas for sale.

[0029] In one embodiment, the tail gas (including silicon tetrachloride, unreacted trichlorosilane, dichlorosilane and high molecular weight silane polymer, etc.) is reduced in step (4).

[0030] In the present invention, a certain proportion of dichlorosilane is configured in trichlorosilane and hydrogen as a raw material, which is beneficial to improving the yield of silane gas in the disproportionation device.

[0031] Specifically, the present invention also relates to a combined production device of an improved Siemens process and a fluidized bed process, the device comprising a hydrochlorination fluidized bed, a TCS refining and purification device, an improved Siemens reduction furnace, a reduction tail gas recovery and purification device, a disproportionation device, an FBR reactor, and a gas-solid separation device;

[0032] The discharge from the hydrochlorination fluidized bed first enters the TCS refining and purification device for purification, and the purified high-purity TCS enters the improved Siemens reduction furnace to participate in the preparation of polysilicon; the reduction tail gas generated by the improved Siemens reduction furnace is separated and purified by the reduction tail gas recovery and purification device, and TCS and DCS enter the disproportionation device to react and produce SiH4; the SiH4 enters the FBR reactor to generate product granular silicon.

[0033] In one embodiment, the reduction tail gas generated by the improved Siemens reduction furnace is separated and purified by the reduction tail gas recovery and purification device, and then H2 is circulated to the FBR reactor and / or the hydrochlorination fluidized bed, and the STC is circulated to the hydrochlorination fluidized bed.

[0034] In one embodiment, the STC and DCS purified by the TCS refining and purification unit can be circulated to the hydrochlorination fluidized bed and the disproportionation unit respectively.

[0035] In one embodiment, the tail gas of the FBR reactor passes through a gas-solid separation device to separate silicon powder and H2, and the H2 can be recycled.

[0036] In one embodiment, the disproportionation device is connected to the feed port of the hydrochlorination fluidized bed, so as to circulate the STC produced as a by-product in the disproportionation device to the hydrochlorination fluidized bed for reaction.

[0037] In one embodiment, the high-purity TCS purified by the TCS refining and purification unit can also be directly introduced into the disproportionation unit for reaction.

[0038] Preferably, the disproportionation device is preferably a reactive disproportionation distillation tower to achieve coupling of disproportionation and distillation.

[0039] Preferably, the gas-solid separation device is a cyclone separator or a membrane separation device, and the membrane is a ceramic membrane.

[0040] The modified Siemens process and fluidized bed process combined production apparatus of the present invention is further provided with a steam thermal energy circulation system. The steam thermal energy circulation system can circulate the by-product steam from the modified Siemens reduction furnace to the disproportionation unit for reaction heating, and circulate the by-product steam from the FBR reactor to the hydrochlorination fluidized bed for reaction heating.

[0041] After adopting the combined production process of the present invention, the steam consumption per kilogram of polysilicon and granular silicon production is reduced by 5 kg compared with the separate processes in the prior art;

[0042] The purity of polysilicon and granular silicon produced by adopting the combined production process of the present invention can reach ≥99.99999999999%.

[0043] Beneficial Effects: The present invention provides a combined production process and apparatus for an improved Siemens process and fluidized bed process. This process can recycle reaction byproducts, significantly improving raw material utilization. This apparatus also reduces investment in production heating equipment through heat circulation between various reaction components, thereby reducing carbon dioxide emissions and energy consumption.

[0044] The present invention utilizes a steam heat energy circulation system to convert steam from the polysilicon production process through a waste heat recovery device to generate high-temperature steam, meeting the steam energy consumption requirements of the downstream granular silicon production process and reducing investment in the required heating equipment for the downstream granular silicon production process. It also converts steam from the downstream FBR reactor granular silicon production process through a waste heat recovery device to generate high-temperature steam, which is then circulated to the hydrochlorination fluidized bed for reaction heating. Compared to independently constructing granular silicon and polysilicon production projects of the same scale, the device and process described in this invention can significantly reduce the amount of reactants and energy consumption.

[0045] The improved Siemens method and fluidized bed method combined production process described in the present invention can significantly reduce the loss of other materials and heat, and recycle them, thereby significantly reducing overall production costs; the production process described in the present invention can reduce 130,000 tons of carbon dioxide emissions at the polysilicon raw material end for 1GW modules, and the industrial chain can reduce carbon dioxide emissions by 47.7%.

[0046] The present invention is described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited to the specific embodiments, but is defined by the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a process flow chart for the joint production of polysilicon and granular silicon. DETAILED DESCRIPTION

[0048] The technical solutions of the present invention are further described in detail below through specific examples. However, it is necessary to point out that the following examples are only used to describe the content of the invention and do not constitute a limitation on the scope of protection of the present invention.

[0049] Example 1:

[0050] A combined production device using a modified Siemens process and a fluidized bed process comprises a hydrochlorination fluidized bed, a TCS refining and purification unit, a modified Siemens reduction furnace, a reduction tail gas recovery and purification unit, a disproportionation unit, a FBR reactor, and a gas-solid separation unit. The discharge from the hydrochlorination fluidized bed first enters the TCS refining and purification unit for purification, after which the purified high-purity TCS enters the modified Siemens reduction furnace to participate in the production of polycrystalline silicon. The reduction tail gas generated by the modified Siemens reduction furnace is separated and purified by the reduction tail gas recovery and purification unit, after which TCS and DCS enter the disproportionation unit to react and produce SiH4. The SiH4 enters the FBR reactor to produce the product granular silicon. The reduction tail gas generated by the modified Siemens reduction furnace is separated and purified by the reduction tail gas recovery and purification unit, after which H2 is circulated to the FBR reactor and / or the hydrochlorination fluidized bed, and STC is circulated to the hydrochlorination fluidized bed. The STC and DCS purified by the TCS refining and purification unit can be circulated to the hydrochlorination fluidized bed and the disproportionation unit, respectively. The FBR reactor tail gas passes through a gas-solid separation unit to separate silicon powder and H2, which can be recycled. The disproportionation unit is connected to the feed port of the hydrochlorination fluidized bed to recycle the STC byproduct from the disproportionation unit to the hydrochlorination fluidized bed reaction. High-purity TCS purified by the TCS refining and purification unit can also be directly fed into the disproportionation unit for reaction. The disproportionation unit is preferably a reactive disproportionation distillation column, achieving coupled disproportionation and distillation.

[0051] The modified Siemens process and fluidized bed process combined production apparatus of the present invention is further provided with a steam thermal energy circulation system. The steam thermal energy circulation system can circulate the by-product steam from the modified Siemens reduction furnace to the disproportionation unit for reaction heating, and circulate the by-product steam from the FBR reactor to the hydrochlorination fluidized bed for reaction heating.

[0052] Table 1 Reaction parameters of a combined production device of improved Siemens process and fluidized bed process

[0053] Example 2:

[0054] The process flow of the improved Siemens process and fluidized bed process combined production process of the present invention is shown in FIG1 .

[0055] A combined production process of an improved Siemens process and a fluidized bed process comprises the following steps:

[0056] Step (1): Hydrochlorination: Silicon powder, hydrogen chloride, silicon tetrachloride and hydrogen are used as raw materials to react and prepare TCS (SiHCl3);

[0057] Step (2): TCS refining and purification: The TCS prepared in step (1) is purified by adsorption and distillation to remove impurities; the STC and DCS purified by the TCS refining and purification device can be recycled to the hydrochlorination fluidized bed and the disproportionation device respectively.

[0058] Step (3): TCS reduction reaction: The TCS (SiHCl3) prepared in step (2) is introduced into a modified Siemens reduction furnace as a raw material for reduction to produce polysilicon; the reduction tail gas, after recovery and purification, the DCS and TCS can be used for the disproportionation reaction in step (5) to produce silane; the silicon tetrachloride can be recycled to the hydrochlorination reactor;

[0059] Step (4): recovering and purifying the reduction tail gas from the production process of the modified Siemens process reduction furnace to recover DCS (SiH2Cl2) and TCS, STC, HCl, and H2; and recycling the purified hydrogen to the hydrochlorination reactor and / or the fluidized bed reactor for recycling;

[0060] Step (5): passing the DCS (SiH2Cl2) / TCS recovered from the Siemens process in step (4) into a disproportionation device for disproportionation reaction to obtain silane SiH4;

[0061] Step (6): The silane prepared in step (5) and the hydrogen recovered in step (4) are introduced as feed gases into a FBR fluidized bed reactor to generate heterogeneous deposition to produce granular silicon. The FBR fluidized bed reactor tail gas is passed through a gas-solid separation device such as a cyclone to remove silicon powder, and the resulting hydrogen is recovered to a hydrochlorination reactor for use in the production of trichlorosilane.

[0062] The steam produced as a by-product of the reduction furnace in step (3) is circulated to the disproportionation reaction device in step (5) and used to heat the silane gas production device. The steam produced as a by-product of the FBR fluidized bed reactor in step (6) is circulated to the hydrochlorination device in step (1) for heating.

[0063] The power consumption of fluidized bed granular silicon deposition using this method is less than 3kWh / kg; the comprehensive power consumption is less than 15kWh / kg; the purity of polysilicon and granular silicon produced by the combined production process of the present invention can reach ≥99.99999999999%, and the total metal impurity content is less than 1ppbw.

Claims

1. A combined production process of improved Siemens process and fluidized bed process, characterized in that: The process comprises the following steps: (1) Hydrochlorination: Silicon powder, hydrogen chloride, silicon tetrachloride and hydrogen are used as raw materials to react and prepare TCS (SiHCl3); (2) TCS refining and purification: The TCS prepared in step (1) is purified by adsorption and distillation to remove impurities; (3) TCS reduction reaction: The TCS (SiHCl3) prepared in step (2) is introduced into a modified Siemens reduction furnace as a raw material to reduce and produce polysilicon; (4) Recovering and purifying the reduction tail gas in the production process of the improved Siemens reduction furnace to recover DCS (SiH2Cl2) and TCS, STC, HCl, and H2; (5) passing the DCS (SiH2Cl2) / TCS recovered from the Siemens process in step (4) into a disproportionation device for disproportionation reaction to obtain silane SiH4; (6) The silane prepared in step (5) and the hydrogen recovered in step (4) are introduced into the FBR fluidized bed reactor as raw gas to generate product granular silicon by heterogeneous deposition.

2. The improved Siemens method and fluidized bed method combined production process according to claim 1, characterized in that: The STC and DCS purified by the TCS refining and purification device in step (2) can be circulated to the hydrochlorination fluidized bed and the disproportionation device respectively.

3. The improved Siemens method and fluidized bed method combined production process according to claim 1, characterized in that: The hydrogen purified in step (4) is recycled to the hydrochlorination reactor and / or the fluidized bed reactor for cyclic utilization.

3. The improved Siemens process and fluidized bed process combined production process according to claim 1, characterized in that the tail gas of the FBR reactor is separated into silicon powder and hydrogen by a gas-solid separation device.

4. The combined production process of polycrystalline silicon and granular silicon according to claim 1, characterized in that: The reduced tail gas in step (3), after being recovered and purified, DCS and TCS can be used for the disproportionation reaction in step (5) to produce silane.

5. The combined production process of polycrystalline silicon and granular silicon according to claim 1, characterized in that: The reduced tail gas in step (3) can be recycled to the hydrochlorination reactor after recovery and purification of silicon tetrachloride.

6. The combined production process of polysilicon and granular silicon according to claim 1, characterized in that: The steam produced as a by-product of the reduction furnace in step (3) is circulated to the disproportionation reaction device in step (5) and used for heating the silane gas production device.

7. The combined production process of polycrystalline silicon and granular silicon according to claim 1, characterized in that: The steam produced as a by-product in the FBR fluidized bed reactor in step (6) is circulated to the hydrochlorination in step (1) for heating the raw materials.

8. The combined production process of polycrystalline silicon and granular silicon according to claim 1, characterized in that: The raw material for the disproportionation reaction in step (5) can also be TCS (SiHCl3) prepared in step (1).

9. The combined production process of polycrystalline silicon and granular silicon according to claim 1, characterized in that: In the step (5), silane is prepared by disproportionation reaction and can be compressed to obtain high-pressure silane gas.

10. A combined production device of improved Siemens process and fluidized bed process, characterized in that: The device comprises a hydrochlorination fluidized bed, a TCS refining and purification device, an improved Siemens reduction furnace, a reduction tail gas recovery and purification device, a disproportionation device, an FBR reactor, and a gas-solid separation device; The discharge of the hydrochlorination fluidized bed first enters the TCS refining and purification device for purification, and the purified high-purity TCS enters the improved Siemens reduction furnace to participate in the preparation of polysilicon; the reduction tail gas generated by the improved Siemens reduction furnace is separated and purified by the reduction tail gas recovery and purification device, and TCS and DCS enter the disproportionation device to react and produce SiH4; the SiH4 enters the FBR reactor to generate product granular silicon.

11. The improved Siemens process and fluidized bed process combined production device according to claim 10, characterized in that: After the reduction tail gas generated by the improved Siemens reduction furnace is separated and purified by the reduction tail gas recovery and purification device, H2 is circulated to the FBR reactor and / or the hydrochlorination fluidized bed, and STC is circulated to the hydrochlorination fluidized bed.

12. The improved Siemens process and fluidized bed process combined production device according to claim 10, characterized in that: The tail gas of the FBR reactor passes through a gas-solid separation device to separate silicon powder and H2, and the H2 can be recycled.

13. The improved Siemens process and fluidized bed process combined production device according to claim 10, characterized in that: The high-purity TCS purified by the TCS refining and purification device can also be directly introduced into the disproportionation device for reaction.

14. The improved Siemens process and fluidized bed process combined production device according to claim 10, characterized in that: The combined production device is also provided with a steam heat energy circulation system. The by-product steam of the improved Siemens reduction furnace can be used for heating the disproportionation device; the by-product steam of the FBR reactor can be used for heating the hydrochlorination fluidized bed.

15. The improved Siemens process and fluidized bed process combined production device according to claim 10, characterized in that: The disproportionation device is preferably a reactive disproportionation distillation tower to achieve coupling of disproportionation and distillation.

16. The improved Siemens process and fluidized bed process combined production device according to claim 10, characterized in that: The gas-solid separation device is a cyclone separator or a membrane separation device, and the membrane is a ceramic membrane.

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