Fluidized bed silicon deposition from silane

Claim 1

A process for producing silicon comprising the steps of: introducing fluidizing gas into a primary fluidized reactor zone in an amount sufficient to maintain a bed of silicon seed particles in a fluidized introducing a silicon containing gas capable of gas phase thermal decomposition into said primary fluidized reactor zone; heating said primary fluidized reactor zone to a temperature sufficient to thermally decompose the silicon in said silicon containing gas to elemental silicon but not above the melting point temperature of silicon; depositing the elemental silicon formed by said thermally decomposed silicon containing gas on said suspended seed particles; continuously removing said seed particles with elemental silicon deposited thereon from said primary fluidized reactor as silicon product; removing excess fluidizing gas, unreacted silicon containing gas, reaction by-product gases and any entrained silicon particles therein from said primary fluidized reactor zone; continuously reintroducing silicon seed particles into said primary fluidized reactor zone to replace silicon seed particles which are removed as silicon product; and producing a continuous supply of said silicon seed particles for introduction into said primary fluidized reactor zone by thermally decomposing a seed generating gas containing silicon in a pyrolysis seed reactor zone to form precursor seed particles including the steps of; introducing said seed generating gas into said seed reactor zone; heating said pyrolysis seed reactor to a temperature sufficient to thermally decompose the silicon in said seed generating gas to form elemental silicon, but not above the melting point temperature of silicon; passing a protective inert gas inwardly through porous reactor walls to form a protective inert gas boundary to prevent contact of silicon with the porous reactor walls; thermally decomposing the silicon in said seed generating gas to form precursor silicon seed particles; removing said precursor silicon seed particles from said pyrolysis seed reactor zone; separating said precursor silicon seed particles into larger silicon seed particles for introducing into said primary fluidged reactor zone and smaller silicon particles which are recycled back to said pyrolysis seed reactor zone for further growth and introducing said separated larger precursor silicon seed particles into said primary fluidized reactor zone as the silicon seed particles.