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Patents

EA – Process for producing polycrystalline silicon (011971)
EA № 011971
Published: 30.06.2009

 

Patent holder (s):
PJSC “State Research and Design Institute of Rare-Metal Industry “Giredmet”

 

Inventors:
L.S. Ivanov, Y.N. Parkhomenko, A.V. Elyutin, V.V. Mitin, V.G. Levin, Y.N. Nazarov, A.A. Kokh, I.Y. Petrova, A.A. Arkadyev, A.M. Chapygin, V.A. Pekelis, T.V. Simonova, V.A. Kozhemyakin, D.Y. Rovensky, N.I. Dzhus

 

The invention relates to polycrystalline silicon production. Generated from technical silicon and hydrogen chloride during thrichlorosilane production, waste gas-vapor mixture with claimed composition, density and reduced molecular weight is subjected to dry and wet dust cleaning. Thrichlorosilane is cleaned to semiconductor purity and mixed with hydrogen. Received mixture is divided into flows which are injected into reactor equally-spaced from each other while maintaining consumption, temperature and pressure allowing to produce second waste gas-vapor mixture with claimed parameters. Thrichlorosilane is sent to reduction, and silicon tetrachloride - to hydrogenation, while maintaining consumption, temperature and pressure allowing to produce third waste gas-vapor mixture with claimed parameters. Waste gas-vapor mixtures are cooled with set rate before condensation, hydrochloric acid is produced from redundant hydrogen chloride, which is used to clean unreacted silicon before returning it into the process. Waste gas treatment is performed by sodium or calcium carbonate solution, and after that by sodium hydroxide solution. Solid colmatants, recycled water and concentrated sodium chloride solutions sent for electrolysis or calcium chloride used as grouting mortar are produced from cleansing and spent solutions. Polycrystalline silicon is grinded in inert atmosphere washing it with water and producing main product in the form of bars, and secondary product in the form of agglomerated dust. Evaporation is performed to claimed concentration by sodium chloride or calcium chloride. Unreacted silicon is washed with hydrochloric acid after hydrochlorination. Silicon rods are produced by polycrystalline silicon layer deposition at silicon cylindrical work material with claimed diameter and at claimed mole ratio of hydrogen and thrichlorosilane, temperature, pressure and amount of supplied thrichlorosilane per one unit of silicon work material surface. Technological effect is providing fully closed cycle mode with full recirculation of substances used in the process and zero drain, and producing extra marketable products while increasing polycrystalline silicon output and reducing power inputs.


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