Transformations in the Si-O-Ca system: Silicon-calcium via solar energy

Abstract

The production of silicon-calcium alloy is energy intensive (>10,000 kWh/t). This means that energy cost has a relevant influence in the price of the alloy. The utilization of concentrated solar energy in the synthesis of silicon-calcium alloy is proposed in this paper. Metallurgical quality silicon and limestone are used as starting materials (25 wt.%, 50 wt.% and 75 wt.% Si). After a 12 min treatment under power values of around 1 kW and without using special atmosphere, silicon-calcium was detected in all samples, although mixed with the products of reaction (Ca3Si2O7, Ca10O25Si6, SiO2). This last question means that there was not proper separation metal-slag, and it should be improved in future investigations. However, the basic knowledge presented in this paper could be of great interest for an industrial process based on the solar energy. This way, the energy costs could be reduced, the pollutant emissions could be minimized, and the competitiveness of the ferroalloys industry could be increased.