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Analysis of Magnesia Carbothermic Reduction Process in Vacuum
YANG TIAN, BAO-QIANG XU, CHENG-BO YANG, BIN YANG, TAO QU, HONG-XIANG LIU, YONG-NIAN DAI, and DA-CHUN LIU
The mechanism of magnesia carbothermic reduction was investigated experimentally in a reduction reaction process in vacuum. The thermodynamic calculation results showed that the initial reduction temperature between MgO and C was 1500 K (1227 C) at 50 Pa. Other reduction reactions did not occur between the temperature 300 K and 1900 K (27 C and 1627 C) and 30 to 100 Pa. Based on the analysis of experimental results, the initial reduction reaction temperature was 1553 K (1280 C), and it matched well with the thermodynamic calculations. The gassolid reaction between MgO and CO did not occur at 1723 K (1450 C), 30 to 100 Pa. Therefore, the main reduction reaction was MgO(s) + C(s) = Mg(g)+ CO(g) in vacuum. This reaction belonged to the solidsolid reaction type, the condensing product was obtained in the condensation zone, and the main component of the product was metal magnesium. A little magnesia was also obtained in the condensing product due to the reverse reaction.
DOI: 10.1007/s11663-014-0106-z The Minerals, Metals & Materials Society and ASM International 2014
I. INTRODUCTION
MAGNESIUM is produced by two main processes: electrolysis of molten magnesium chloride and thermal reduction of magnesia.[1] Electrolysis is the predominant route in Western countries, accounting for about 77 pct of total production in these countries, but this process is characterized by high-energy requirements.[2] More than 95 pct of Chinas production of magnesium is based on the pidgeon process, which uses the silicothermic reduction of dolomitic ores. Even though the pidgeon process is energy intensive and labor intensive, it is simple and has low capital cost.[3] Carbothermic reduction is an alternative to both the silicothermic and electrolytic processes for the production of magnesium.[4,5] The
reaction between MgO and C may provide a new route toward the production of magnesium. But for the carbothermic reduction reaction type, one point of view was that the main reaction is a solidsolid reaction, whereas the other was that the main reaction is a gas solid reaction.[68] Researchers have proposed that in the incipient stage, CO and magnesium vapors are formed
through the reaction MgO(s) + C(s) =...