Metallurgical Viability, Inc.

The production of solar grade silicon requires an application of basic pyrometallurgical techniques to purify the metallurgical grade silicon. In addition, the silica used for production of the metallurgical grade must be very pure especially with regard to boron and phosphorus. The silica can be either very pure from the mine or it can be purified by standard techniques known to hydrometallurgists. Of course, optimizing the system to produce solar grade silicon economically is the challenge. The process can be carried out in traditional electric arc furnaces with careful design of their configuration.

Distribution coefficients are defined as the ratio of the concentration of an impurity in the slag to the concentration of the impurity in the metal (Si). This concept is essential in the successful design of a pyrometallurgical system to make solar grade silicon.

One final concept, zone refining/direction cooling. Zone refining and/or direction cooling has been used to remove trace impurities in the silicon metal from the refining furnace.