Patent holder (s):
PJSC “State Research and Design Institute of Rare-Metal Industry “Giredmet”
A.V. Elyutin, L.S. Ivanov, V.G. Levin
The invention can be used to produce polycrystalline silicon by thrichlorosilane hydrogen reduction in chemical recirculation regime. Process for producing polycrystalline silicon by thrichlorosilane hydrogen reduction to silicon base rods includes pretreatment of base components – hydrogen and thrichlorosilane, preparation of gas-vapor mixture in evaporator, silicon deposition at heated silicon rods in reduction reactor, regeneration of waste gas-vapor mixture components by chlorosilane and hydrogen chloride fraction condensation and returning unreacted thrichlorosilane and hydrogen to the stage of preparing gas-vapor mixture for silicon reduction. Preparation of reduction gas-vapor mixture is performed by hydrogen bubbling through thrichlorosilane layer in evaporator; before fraction condensation, waste gas-vapor mixture undergoes liquid compressing to create pressure in system, which is necessary for recirculation feeding of gas-vapor mixture to reduction reactor; chlorosilane condensate generated after fraction condensation undergoes rectification separating thrichlorosilane and silicon tetrachloride into single products; feeding of gas-vapor mixture into reduction reactor is performed in amount which is proportional to silicon rod surface area at the feeding moment, amount of gas-vapor mixture is defined by dependence; before reduction, preheating (start heating) of rods by plasma heating is performed using nitrogen as orifice gas; before reduction, silicon base rods undergo etching by hydrogen chloride produced after waste gas-vapor mixture fraction condensation. After finishing reduction, polychlorides produced in the process are removed from reactor walls by silicon tetrachloride and hydrogen mixture at mole rate of 1:1. Power inputs are reduced, and silicon quality, process efficiency and environmental safety are increased, reagent consumption at product unit is reduced.