Patent ID: 7854784
Filing Date: 2010-12-21
Classification: C01B,C21C,Y02P

Abstract:
1. A method for making solar grade silicon from metallurgical grade silicon comprising, treating a calcium-silicate based slag with a molten ferrosilicon alloy in a first vessel, whereby phosphorous in the calcium-silicate based slag is transferred to the ferrosilicon alloy producing a calcium-silicate based slag containing less than 3 ppmw phosphorous; obtaining the calcium-silicate based slag containing less than 3 ppmw phosphorous from the first vessel; treating a molten metallurgical grade silicon in a second vessel with the calcium-silicate based slag containing less than 3 ppmw phosphorous to reduce the content of phosphorous, boron and iron in the metallurgical grade silicon and produce a solar grade silicon; and removing the solar grade silicon from the second vessel.