Magnesia Vacuum Carbothermal Reduction Of Experimental Research

The development of the domestic magnesium industry, primary magnesium and properties, applications and preparation methods are overviewed in the thesis. It's the opinion of the author that there are grave defects in traditional methods, say, moltensalt electrolysis or silicothermic reduction of oxides. The former process is complex and needs vast investment, and emits toxic gases like chlorine gas; treatment of production wastes is overburden costly; erosion of the production equipments and plant buildings is badly, and maintenance cost overwhelming. The flaws in the process of magnesium extraction by silicothermic reduction of oxides are: (1) high cost of major reductant, ferrosilicon (70%); the boosted production cost accordingly; (2) short service life of reduction retort, which is made of high Ni-Cr alloy; (3) vacuum inside the retort heated under the normal pressure, small-size of the retort, low forced filling rate, low production capacity thermal efficiency, batch production, low productivity and production.In the process of magnesium extraction in vacuum, the reduction temperature needed is lowered, reduction efficiency enhanced, crude magnesium oxidization more difficult. Introduction of vacuum technology in magnesium extraction, high Ni-Cr alloy is substituded by cheaper carbon and reduction retort by internal heating vacuum furnace; scale of vacuum furnace is free of the limit of retort cubic capacity; thermal efficiency and production of single equipment are raised, cost decreased and working conditions improved. Since all reactions take place in the closed vacuum furnace, there is no production wastesproduced and less influence upon environment.Through inter-link retrieve, relevant papers are absent domestic; and abroad is scarce. R.Wind, the most epitomized(reference 31), solved only how to produce magnesium vapor through magnesia reduction by carbon, conditions and devise of condenser used to condense the vapor into liquid or solid critical magnesium was not touched upon.The thesis expounds on the magnesia reduction by carbon theoretically and experimentally. It is observed: the process is feasible; reducing temperature can be decreased by 300℃-400℃; vacuum can not only enhance reaction rate, but exhibit the reverse reaction of magnesium vapor by CO or CO2; condensed mangnesium taken the shape of solid, lump can be obtained successfully on the inner surface of the condenser, during the course of crystallization magnesium develops vertically the shape of coarse fibre, and has solid crystalliform; the condasate grade is above 94%; sampling is safety; change of vacuum vs time takes regular pattern, thus, reduction velocity and rate can be deduced, temperature enhanced and reduction elongated, reduction velocity increased; material treated by briquetting and coking is in favor of reaction rate and velocity; a small amount of fluorine compounds added can accelerate the reaction; impractical flowsheet of magnesia reduction by carbon is developed.