METHOD OF PRODUCTION OF POLYCRYSTALLINE SILICON Russian patent published in 2006 - IPC C01B33/03 C01B33/35 

FIELD: chemical industry; methods of production of polycrystalline silicon by hydrogenous reduction of trichlorosilane.

SUBSTANCE: the invention is pertaining to the field of chemical industry, in particular, to the method of production of polycrystalline silicon by hydrogenous reduction of trichlorosilane within the closed technological cycle with regeneration of silicon tetrachloride from the withdrawn gaseous phase by hydrogenation till production of trichlorosilane. The method includes: preparation of the initial steam-gas mixture in the evaporator by bubbling hydrogen through the layer of the trichlorosilane at maintaining the permanent temperature and pressure in the evaporator; compression of the components of the steam-gas mixture withdrawing from the recovery reactor and creation of pressure in the closed system of the apparatuses ensuring recirculation of the unreacted trichlorosilane and hydrogen; the fractional condensation of chlorosilanes and hydrogen chloride; separation by the rectification of trichlorosilane and silicon tetrachloride from the products of condensation; separation of gaseous components of hydrogen chloride and hydrogen; synthesis of trichlorosilane from the produced silicon tetrachloride and recirculation of the synthesized trichlorosilane to the phase of preparation of the steam-gas mixture for recovery. At preparation of the initial steam-gas mixture in the evaporator maintain the temperature and the pressure corresponding to reception of the molar ratio of hydrogen and trichlorosilane of (3.6-6.0): 1. The steam-gas mixture being withdrawn after recovery of trichlorosilane is cooled to temperature of -45 - -47°C with condensation of the main amount of the silicon tetrachloride and partially - of trichlorosilane and other chlorosilanes; compression of the being withdrawn steam-gas mixture after separation of silicon tetrachloride condensate conduct up to the pressure of 7.5 8.0 gage atmospheres at maintaining the temperature of -45 - -47°C with condensation of the main amount of trichlorosilane and other chlorosilanes; from the produced after the rectification silicon tetrachloride by hydrogen hydrogenation produce trichlorosilane. The process of hydrogenation is conducted at preparation of the initial mixture in the evaporator by bubbling of hydrogen through the layer of silicon tetrachloride at the temperature and the pressure ensuring the molar ratio of hydrogen and silicon tetrachloride of (1-3 : 1). Then sequentially realize separation of the components of the steam-gas mixture being withdrawn after hydrogenation. First condensate silicon tetrachloride and return it to the phase of preparation of the initial mixture for hydrogenation. Then the steam-gas mixture is compressed, trichlorosilane is separated by condensation and it is returned to the phase of preparation of the initial mixture for the hydrogen recovery of the polycrystalline silicon; the hydrogen chloride is separated by absorption by trichlorosilane and direct for production of trichlorosilane, but hydrogen is separated by adsorption on the activated charcoal and it is returned for preparation of the initial mixture for hydrogenation of silicon tetrachloride by hydrogen; hydrogenation and separation of the components of the steam-gas mixture being withdrawn after hydrogenation is realized in the unified recirculation circuit, for creation of which the initial and the regenerated silicon tetrachloride, the initial and the regenerated hydrogen are directed into the evaporator under pressure formed in the system of apparatuses by compression of the steam-gas mixture being withdrawn after hydrogenation. The technical result of the invention is reduction of the power input and the prime cost of the polycrystalline silicon.

EFFECT: the invention ensures reduction of the power input and the prime cost of the polycrystalline silicon.

4 cl, 2 dwg, 1 ex