Patent ID: 9243311
Filing Date: 2016-01-26
CPC Classification: C01B,C22B,C22C

Claim Text:
1. A process for removing phosphorous and boron from metallurgical grade silicon, the method comprising: a) heating a mixture of aluminum, metallurgical grade silicon, and at least one of calcium, titanium, vanadium, zirconium, chromium, hafnium, silicon dioxide, and sodium chloride, with greater than the eutectic composition of silicon, to form a melt, wherein the metallurgical grade silicon comprises about 14-135 ppmwt phosphorus and about 4-50 ppmwt boron; b) cooling the melt to a temperature above the solidus temperature; c) contacting the melt with a gas comprising oxygen, present in about 15 wt. % to about 75 wt. % of the gas, such that a vortex is formed in the melt, wherein the vortex is at least at the surface of the melt, wherein the gas is injected using a rotary impeller, wherein the oxygen contacts the melt, without chlorine, and, d) removing dross present in the melt; wherein the process removes boron and phosphorus from silicon, wherein the phosphorus is reduced to about 0.1-20 ppmwt, and the boron is reduced to about 0.1-10 ppmwt, wherein the process optionally further removes at least one of calcium, lithium, magnesium, strontium, aluminum, and titanium contained in the metallurgical grade silicon, wherein the silicon that is obtained from the process is used in the manufacture of solar cells.