Thermodynamic analysis of interaction of components in the SIO2-C system: improvement of technical silicon production technological process

Abstract

In order to identify ways to improve the technological process of smelting metallic (crystalline) silicon of technical purity, a thermodynamic analysis of the interaction of components in the SiO2-C system is carried out that reveals the main factor in obtaining high-quality technical silicon is the elimination of superposition of the silicon carbonization process that is possible by carrying out a two-stage carbothermal reduction reaction, in that firstly the incomplete reduction of silica (SiO2) by solid carbon (C) is provided, accompanied by the release of new reacting gas components - SiO and CO, the subsequent interaction of which leads to the formation of the target product - technical silicon that is suitable for the production of modern solar energy converters. It is determined that main condition for highly efficient reduction reactions is the fine fractionness (<1 mm) of the used quartzite ore with keeping of a rational temperature range for its carbothermal reduction (1688-2000 K). It has been shown experimentally that the optimal technical solution for the implementation of this reduction process is to performt melting in a special plasma-chemical furnace-reactor with one liquid-metal subconducting electrode, with a reverse vertical feed of the reaction gases released at the first stage. The degree of extraction of silicon was on average 95%, and the degree of its purity was 97.2%.

Development and investigation of the technological process of plasma carbothermal reduction of slag from secondary metallurgy of aluminum

“…A review of the references mentioned above, on the one hand, and the results of our own theoretical and experimental work on the carbothermal reduction of metal oxides [23,35,36,37], on the other, show that for small-scale production of target alloys, it is more convenient to conduct reduction reactions in a specially modernized plasmachemical arc furnace-reactor, with the possibility of simultaneous supply of solid and gasphase carbonaceous reducing agents.…”

“…A systematic examination of the options for accelerating the recovery process while minimizing the environmental impact revealed that the primary goal is to maximize the efficiency of the application of methane and the synthesis gas released when reacting with metal oxides that have a high potential for recovery under appropriate thermodynamic conditions. In this regard, the mentioned plasma-arc melting technology of special plasma-chemical arc furnace-reactors with one liquid-metal bottom electrode provides the possibility of reverse vertical supply of the mentioned gas reagents [37]. In addition, we added a special side tuyere directed to the high-temperature reaction zone, with the possibility of injection and diffusion of methane in the melt's oxide layer, for the implementation of gas-phase reduction processes in the reactor-furnace (active power 100 kVA).…”