Method for preparing silicon from composite molten salt electrolyte

Abstract

The invention provides a method for preparing silicon from a composite molten salt electrolyte. The method comprises the following steps of: adding calcium oxide-calcium chloride (CaO-CaCl2) serving as the molten salt electrolyte into silica or silicon dioxide (SiO2) serving as a raw material until the mass ratio of the SiO2 to the CaO in the mixture is 2-30:1, wherein the CaO mass content of the CaO-CaCl2 molten salt electrolyte accounts for 1 to 15 percent of that of the CaO-CaCl2 molten salt electrolyte; and raising the temperature to 600 to 1,000 DEG C under a protective gas environment and performing electrolytic reduction so as to obtain elementary substance silicon. The silica or the silicon dioxide serving as the raw material is not under the control of shapes and can be in the form of blocks, particles or powder; and the electrolyte CaO-CaCl2 serves as a mixed molten salt system for silicon electrolysis, so that the silicon dioxide can be dissolved directly, silicon yield is increased, current efficiency in an electrolytic process is improved, electrolysis temperature and energy consumption are low, product recovery is high and greenhouse gases and impurities are not produced.

Description

technical field [0001] The invention relates to a method for preparing silicon with a composite molten salt electrolyte, belonging to the field of electrochemical metallurgy. Background technique [0002] Silicon mainly exists in the form of oxides and silicates in nature. The production of silicon at home and abroad uses silica as raw material and carbon as reducing agent. It is smelted at high temperature in an electric furnace. The melting temperature in the production process reaches 2000 ° C. High consumption, large greenhouse gas emissions, and high impurity content. [0003] Since G.Z.Chen and D.J.Fray of the University of Cambridge successfully prepared titanium by direct electrolytic reduction of solid titanium dioxide by the molten salt electrolysis method, the research on the electrolytic reduction of various metal oxides by the molten salt electrolysis method has become a major research hotspot. In 2003, Professor Yasuhiko Ito of Kyoto University in Japan propos...

AI Technical Summary

Problems solved by technology

[0005] In order to overcome the problems of high energy consumption, large greenhouse gas emissions, and high impurity content when preparing high-purity silicon, the present invention provides a method for preparing silicon with a composite molten salt electrolyte to reduce the temperature and energy consumption in the silicon production process