2016-Sustainable Industrial Processing Summit
SIPS 2016 Volume 8: Non-ferrous, Rotary Kiln, Ferro-alloys, Rare Earth, Coal
| Editors: | Kongoli F, Xueyi G, Shumskiy V, Kozlov P, Capiglia C, Silva AC, Turna T |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2016 |
| Pages: | 350 pages |
| ISBN: | 978-1-987820-50-8 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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The Effect of Na2O on the Removal of Boron and Phosphorus from Silicon Using CaO-SiO2 Flux
Guoyu Qian1; Zhi Wang1; Jianwei Cao1; Qingchao Zhao1; Xuzhong Gong2;1INSTITUTE OF PROCESS ENGINEERING. CHINESE ACADEMY OF SCIENCES, Beijing, China; 2INSTITUTE OF PROCESS ENGINEERING, CHINESE ACADEMY OF SCIENCES, Beijing, China;
Type of Paper: Regular
Id Paper: 73
Topic: 6
Abstract:
Interface mass-transfer dynamics control and thermodynamics restriction of interphase distribution coefficient are the common problems in the process of producing high-purity silicon at present, especially for low concentration impurities B and P with high harmfulness. Traditional metallurgical purification method is difficult to remove impurities B and P simultaneously, which can lead to low efficiency and high energy consumption problem. Flux treatment can be efficient to remove B from silicon, but not for P due to the weaken ability to combine with oxygen. In order to efficiently remove P under the condition of slagging remove B, the addition of Na2O into slags were carried out to improve the oxidizability of slag for the simultaneous removal of B and P. Metallurgical grade silicon was subjected to refining by liquid CaO-SiO2-(Na2O) slags at 1823K(1550ˇć). The removal efficiency of B and P was examined under a range of slag compositions with different amount of Na2O. The results showed that the removal efficiency of B and P increased with the addition of Na2O to slags. For the slag without Na2O, the removal efficiency of B and P were 40% and 57%, respectively. When the Na2O in slag increased to 30%, the removal efficiency of B and P increased to 85% and 67%, respectively. A thermodynamic evaluation of the slags system showed that the addition of Na2O led to a substantial increase of free oxygen ion activity and oxygen partial pressure, which enhanced the removal of impurity B and P.
Keywords:
Alloys; Materials; Slag; Smelting; Sustainability;References:
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