Method of improving the efficiency of a silicon purification process

Abstract

Methods for Heating a Fluidized Bed Silicon Deposition Apparatus with the steps of: one or more heaters and entries to the reactor for the gas or gases which can be heated without decomposition separate from one or more heaters and entries for the gas or gases which decompose to form silicon when heated, heating the gas or gases which do not decompose to temperatures between 400-2000 C., more preferably 800-1600 C., heating the gases which do decompose thermally to temperatures less than the temperature at which they decompose, typically 25-400 C., preferably 300-350 C., and alternatively or in combination with the above steps also providing a means for removal of the silicon beads, heating the beads to a temperature between 800-1200 C. and preferably to a temperature between 900-1100 C. and returning the beads to the reactor. Providing localized cooling of the entries for the thermally decomposable gases. These two heating methods either alone or in combination can provide all the heat needed to operate the reactor in the desired operating range of 800-1100 C. and can provide the heat at the inlet of the reactor where the cold silicon containing gases need to be raised to the operating temperature of the reactor. Heating the non decomposing gases and the silicon beads outside the reactor can be accomplished easily with a variety of low cost heating techniques. Other benefits include, higher flow rates in the reactor, higher production rates, larger and more spherical beads, increased deposition efficiency and reduced risk of sintering and plugging.