Patent ID: 8329133

Claim:
A process for refining metallurgical grade silicon in a reactor including a heat zone and means for controlling the temperature and pressure in the reactor, said process reducing the levels of impurities including at least one of phosphorus and boron impurities in the metallurgical grade silicon and comprising the steps of: A) selecting a calcium-based agent for reducing a level of the at least one of the phosphorous and boron impurities, B) loading the silicon and the selected agent into a crucible to produce a mixture, C) placing the loaded crucible into the reactor heat zone, D) refining the mixture of the silicon and the selected agent by elevating the temperature in the reactor heat zone to at least the melting point for the mixture in a non-oxidizing environment at a pressure of 50-100 bar, and then further reducing the pressure in the reactor heat zone to cause and control bubbling in the melted mixture thereby to produce a melted refined material, and E) thereafter directionally solidifying the melted refined material produced in step D) in the same crucible and reactor thereby to segregate impurities during said directional solidification whereupon there is produced silicon with reduced levels of impurities including the at least one impurity of phosphorus and boron.