Method for production of pure silicon
AssigneeElkem a/s
InventorGunnar Halvorsen
Life of this patent
Estimating the term…
Abstract
Pure silicon metal is produced from a silicon metal which contains 1-10% Ca and which is cast into molds with relatively slow rate of cooling. The cast metal is pre-crushed and thereupon subjected to a purification process consisting of two leaching steps where in the first leaching step there is employed an aqueous solution of FeCl.sub.3 or FeCl.sub.3 +HCl which causes a disintegration of the metal. The fines are washed away in place thereof, and the metal is further leached in the second leaching step with an aqueous HF+HNO.sub.3 solution. The necessary amount of calcium is supplied in the smelting furnace in the form of CaO or other suitable Ca compound.
Claims5
A process for purifying metallurgical grade silicon which comprises the steps of adding one or more calcium compounds to molten metallurgical grade silicon in an amount sufficient to provide molten silicon containing about 1.0 to about 10.0% by weight of calcium, casting the molten silicon into molds and cooling the molten silicon at a sufficiently slow rate to obtain solid silicon having a grain size not over about 1.0 mm, precrushing the resulting silicon and leaching it in a first step with an aqueous solution of FeCl.sub.3 or an aqueous solution containing FeCl.sub.3 and HCL which cause disintegration of silicon, washing away fines from the leached silicon and in a second step leaching the silicon with an aqueous solution containing HF and HNO.sub.3.
Dependencies are inferred from the claim text.