Process for obtaining silicon from fluosilicic acid
AssigneeSRI International
InventorAngel Sanjurjo
Life of this patent
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Abstract
Process for producing low cost, high purity solar grade Si wherein a reduction reaction, preferably the reduction of SiF.sub.4, by an alkali metal (Na preferred) is carried out by jetting a spray of reactants into a reaction chamber at a rate and temperature which causes the reaction to take place far enough away from the entry region to avoid plugging of reactants at the entry region and wherein separation in the melt is carried out continuously from the reaction and the Si can be cast directly from the melt.
Claims13
A process for producing low cost, high purity, solar grade silicon by reaction of gaseous silicon tetrafluoride with sodium in substantially stoichiometric quantities to produce a reaction product consisting essentially of sodium fluoride and silicon from which silicon is recovered and wherein said fluoride gas used in the reaction is obtained by thermal decomposition of sodium fluosilicate which is precipitated from aqueous fluosilicic acid generated from phosphate rock conversion to fertilizer, said process comprising:
- (a) carrying out said reaction inside a reactor including a reaction chamber formed with perforations in the walls thereof, said perforations being of a size such that essentially all of the molten sodium fluoride product of said reaction product freely passes out through the perforations due to the low surface tension of sodium fluoride compared to silicon, and molted silicon is preferentialy contained in the reaction chamber;
- (b) collecting said molten sodium fluoride product of said reaction product passing through said perforations in said reaction chamber in a sodium fluoride product collection and dispensing chamber surrounding said reaction chamber;
- and
- (c) removing the silicon product of said reaction product remaining in the lower portion of said reaction chamber by free flow.
A process for producing low cost, high purity, solar grade silicon by reaction of gaseous silicon tetrafluoride with sodium in substantially stoichiometric quantities to produce a reaction product consisting essentially of sodium fluoride;
- and silicon from which silicon is recovered and wherein said fluoride gas used in the reaction is obtained by thermal decomposition of sodium fluosilicate which is precipitated from phosphate rock conversion to fertilizer, said process comprising:
- (a) jetting a spray of sodium and gaseous silicon tetrafluoride into a reactor including a reaction chamber formed with perforations in the walls thereof which perforations are sized to prevent the flow of molten silicon therethrough but to permit flow of the molten sodium fluoride product of said reaction product freely out of said reaction chamber due to the low surface tension of sodium fluoride compared to silicon;
- (b) collecting the molten sodium fluoride product of said reaction product passing through said perforations in a sodium fluoride product collection and dispensing chamber which surrounds said reaction chamber;
- (c) continuously removing said sodium fluoride reaction products from said sodium fluoride reaction product collection and dispensing chamber for recycling in the procee;
- and
- (d) continuously removing the molten product remaining in said reaction chamber into casting member thereby to cast silicon directly from the process;
Dependencies are inferred from the claim text.