Study on Dolomite reduction by Fe-Si-Al for Mg production in the Pidgeon process

Abstract

Magnesium consumption has grown considerably during the past decades due to its lightness and outstanding specific strength, which help industries reduce their energy consumption and environmental restriction. Most of the magnesium is worldwidely produced through Silicothermic reduction, or the so-called Pidgeon process, in which dolomite experiences a reduction process by the reducing agent of ferrosilicon. The Mg production of Silico-thermic reduction of dolomite requires a lot of energy consumption, and the production of ferrosilicon generates a large emission of carbon dioxide. Thus, this research explores the silico-alumino-thermic reduction of dolomite utilizing the commercially available, ferrosilicon-aluminum(Fe-Si-Al) as a reducing agent, hoping to reduce those faults involved in the Pidgeon process. The processing parameters of the aluminum/silicon ratio in Fe-Si-Al and the operation temperature were considered to evaluate the introduction of Al into Fe-Si as a reducing agent on the kinetics of MgO reduction. The ferrosilicon-aluminum reduction of MgO outweighed ferrosilicon reduction in terms of reduction kinetics and reduction ratio of MgO. The reduction reaction between dolomite and ferrosilicon-aluminum had thermodynamically a lower Gibbs free energy change of reaction than that between dolomite and ferrosilicon, resulting in a higher vapor pressure. Also, the decomposition temperature of ferrosilicon-aluminum mixed phase(880°C) lower than the melting point of ferrosilicon(1210°C), enhancing the reaction between solid(dolomite)/liquid(reducer) phases. The phases of ferrosilicon-aluminum according to the stoichmetry of aluminum/silicon were found to be a influencing parameter for the improvement on reduction capability.