METHOD FOR PRODUCTION OF MULTI- AND MONOCRYSTALLINE SILICON Russian patent published in 2001 - IPC

FIELD: chemical engineering. SUBSTANCE: process is conducted in three stages. Quartz containing impurities of the order of 10^-4 % is reduced in sealed reactor to gaseous monoxide by the aid of chemically purified industrial-grade silicon and own silicon ingot scrap containing no more than 10^-3 % impurities. First-stage reactor leaves pure gaseous monoxide, all the impurities being retained in condensed state in crucible. Gas product is conveyed into the second sealed reactor wherein it is reduced into elementary silicon by fine carbon black supplied with carbon monoxide flow. Gas leaving the second-stage reactor passes dust catching system and freed from carbon dioxide. Part of gas consisting of carbon monoxide is fed into catalytic decomposition apparatus to be converted into carbon black. Carbon dioxide formed in this process is subjected to plasma-chemical processing to give carbon black and oxygen discharged into atmosphere. Second part of carbon monoxide serves as gas carrier for carbon black supplied to reduction reactor. Thus closed cycle for carbon is created. Liquid silicon product is pumped directly into furnace assemblies for production of multi- and monocrystalline silicon ingots. Silicon purity in treated ingots exceeds 99.9995%. Ingot scrap is utilized in the first-stage reactor as reducing agent. Dust from dust catching system is also utilized in the first-stage reactor together with initial raw material thus closing cycle for silicon-containing materials. EFFECT: improved environmental condition and reduced loss of product. 11 cl, 1 dwg