| 摘要 |
PROBLEM TO BE SOLVED: To efficiently include steam in a plasma gas and improve the removal of boron by blowing steam at an angle within a prescribed range from the flow direction formed by the plasma gas when blowing the plasma gas comprising an inert gas to which the steam is added on the molten silicon surface of metallic silicon kept in a molten state. SOLUTION: The angle θ1 of a nozzle 12, provided at the tip surface of a torch 3 for generating a plasma gas 2 to melt metallic silicon 1 and used for blowing out steam from the central axis of the torch 3 which is the flow direction formed of the plasma gas 2 is kept within the range satisfying sin θ1 <C(VP/VH) (VP is the flow velocity of the plasma gas 2; VH is the flow velocity of the steam; C is a constant of about tan 10 deg.). The height (d) of a steam blowing port 12 from the melt surface is preferably (d)<=R/tanθ1 (R is the distance between the center of a plasma flame spot 13 on the melt surface and the foot of a perpendicular drawn from the blowoff port 12. |
