Patent ID: 8802046
Filing Date: 2014-08-12
Classification: C01B,Y10T

Abstract:
1. A process for producing a granular polycrystalline silicon in a fluidized bed reactor, comprising: fluidization of silicon seed particles by a gas flow in a fluidized bed which is heated by a heating apparatus, addition of a silicon- and halogen-containing reaction gas resulting in pyrolytic deposition of elemental silicon on heated surfaces of the seed particles, forming the granular polycrystalline silicon, with removal from the reactor of particles whose diameter has grown as a result of deposition and an offgas comprising hydrogen halide, and metered addition of fresh seed particles, wherein: (a) a concentration of hydrogen halide in the offgas is determined as a controlled variable; (b) and a rate of the metered addition of fresh seed particles and a heating output of the heating apparatus are controlled as manipulated variables, in order to keep the hydrogen halide concentration in the offgas within a defined range during operation; (c) the granular polycrystalline silicon has a chlorine content of 10-40 ppmw; and (d) the granular polycrystalline silicon comprises particles having a convexity of 0.850-1.000.