Making magnesium from low-grade magnesite: Experimental verification and life cycle assessment

• Low-grade magnesite with a high silicon content can be used as a viable raw material for magnesium extraction, showing favorable economic potential. • The negative impact of silica in low-grade magnesite on the process of extracting magnesium can be mitigated by elevating the content of calcium oxide. • A process route is proposed for the extraction of magnesium from low-grade magnesite, incorporating fluidized bed calcination technology. The feasibility of this route has been confirmed through experimental validation and life cycle assessment. China, as the world`s largest producer and exporter of metallic magnesium, there are plenty of manufactures in the western provinces using the silicothermic method known as the Pidgeon process. The raw material used is usually dolomite containing about 20 wt.% element Mg. Liaoning province in the northeast China has up to 87 % of the national magnesite reserves, which contains 2–4 times more element Mg than dolomite does. How to economically produce metallic magnesium using magnesite is thus of significance for not only the local industry but also the flexible production of metal magnesium. This study proposed a process to produce magnesium using low-grade magnesite and further validated the proposal through experiments. Models of life cycle analysis are in turn formulated to evaluate the energy consumption and economic performance of the entire process proposed by taking the required source data from the Chinese Life Cycle Database (CLCD). The data comprehensively consider a variety of process equipment, energy supply pathways and geographical environments. In comparison with the Pidgeon process, the proposed pathway exhibited the best economic performance through its utilizing low-grade magnesite as the raw ore containing Mg and coke oven gas from steelworks as the fuel.