FIELD: chemical or physical processes.
SUBSTANCE: invention relates to chemical technology of producing polycrystalline silicon by hydrogen reduction of trichlorosilane with hydrogen to silicon core bars in a waste-free mode. Method involves preparation of initial vapor-gas mixture in evaporator SiHCl3 1 by hydrogen bubbling through a layer of trichlorosilane with molar ratio H2:SiHCl3 = (3.0–3.5):1 with its further supply to reduction reactor 2, where polycrystalline silicon is deposited on heated to 1100–1150 °C silicon rods, supply of vapor-gas mixture recovery reactor 2, consisting of hydrogen, silicon tetrachloride, trichlorosilane and hydrogen chloride, into waste heat reactor 3, in which at temperature of 315–350 °C separation of hydrogen chloride from the vapor-gas mixture leaving reduction reactor 2 to obtain a mixture of hydrogen, trichlorosilane and silicon tetrachloride in ratio SiHCl3/SiCl4= 50 %/50 %, then obtained mixture is fed into membrane separation unit 4 for separation of hydrogen on polymer membranes at heating temperature of up to 100 °C and pressure drop of 8 atm, which is returned to the evaporator of SiHCl3 1, and mixture of trichlorosilane and silicon tetrachloride is subjected to condensation 5 and rectification 6, after which trichlorosilane is returned to the evaporator of SiHCl3 1, and silicon tetrachloride is supplied to the evaporator of SiCl4 7, in which hydrogen is bubbled through a layer of silicon tetrachloride to form a vapor-gas mixture with molar ratio H2:SiCl4 = (3.0–6.5):1, which is then fed into plasma-chemical reactor 8 for synthesis of trichlorosilane, wherefrom a gas-vapor mixture consisting of hydrogen, silicon tetrachloride, trichlorosilane and hydrogen chloride, is directed to a waste heat reactor 3 for separation of hydrogen chloride. Therefore, all components are used in production without generation of wastes or emissions into atmosphere.
EFFECT: result is reduced power consumption, increased quality of silicon, environmental safety, reduced consumption of reagents per unit of production.
3 cl, 1 dwg, 1 ex
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Authors
Dates
2020-12-22—Published
2018-10-23—Filed