Review on the Silicothermic Process for Primary Magnesium Production

Pidgeon process as one of the silicothermic processes is the main method for Mg production. This paper aims at reviewing the research and improvement of the Pidgeon process toward solving three problems encountered in the process: slow chemical reaction rate, low heat transfer efficiency, and semi-continuous production. Specifically, the reaction mechanism and kinetics of generic silicothermic processes are first reviewed along with the influence of various factors (raw materials, temperature, time, etc .) on the reduction process. This is followed by an examination of the different ways to improve the reaction rates. Several methods for enhancing heat transfer in an industrial retort are then discussed, such as integrating calcination and reduction in one retort, adding/introducing convective heat transfer, developing internal heating technologies, and using new-type pellets or retorts. Process development for magnesium production under atmospheric pressure, which is a promising process to achieve continuous Mg production, is also reviewed. Future opportunities in developing cleaner and more efficient magnesium production processes are suggested at the end of the paper.