| 摘要 |
PROBLEM TO BE SOLVED: To rapidly remove boron by mixing a plasma operating gas and gaseous mixture of oxidative gas and reductive gas in a plasma torch and jetting the plasma in an oxidative atmosphere thereby melting a metal silicon to remove boron. SOLUTION: The gaseous mixture 8 of the oxidative gas and the reductive gas is introduced through a gas supply port 7 into a plasma torch 1 in such a manner that the concns. of the oxidative gas and the reductive gas in a plasma operating gas 4 are 1 to 40% and 5 to 90%, respectively, and the mixed gas is sprayed as a plasma jet 2. Copper hollow electrodes are used as the cathode 3 and the anode 5 and the plasma gas is sprayed to the metal silicon in oxidative atmosphere to melt it in the plasma to remove boron. Since the copper hollow electrodes have a wide discharge area and a long time to be exposed to the arc, the service life of the torch can be prolonged and the time required for the production of silicon can be shotened. |
