Vacuum Carbon Thermal Reduction Of Calcined White Preparation Of Magnesium Metal Experimental Study

Traditionally, we extract magnesium by pyrolytic or electrolytic process. Pidgeon method, one of the pyrolytic process and most widely used, has the merits of popular technology? moderate investment cost and short commissioning cycle, but compared with Bolzano and Magnethem method it costs resource dearlier. The development and research of new?internally heated magnesium extraction technology can reduce operating cost, advance our engineering level and materialize the dream of a magnesium production power.Dolomite reacts with coal in internally> electrically heated vacuum furnace at lower temperature than in the atmosphere, therefore, the method is power economy. Magnesium, condensed directly from liquid, no trouble of smelting, could be obtained. Related research proves the competitive edge over Magnethem process.The paper reviews the physical and chemical properties? manufacturing process of magnesium, magnesium resource, comprehensive utilization of dolomite, application of magnesium and its alloys, etc. Experiments of dolomite calcining and vacuum carbothermic reduction of calcined dolomite are labored on.Vacuum carbothermic reduction requires dolomite be calcined and decomposed completely to cut the burden of pumping and smooth the proceeding of reduction, crystal grain of MgO be fine and no recrystallization, and calcination be porous and have high activity.By means of X-ray diffraction analysis, it is clarified that dolomite decomposition follows the steps of:CaMg (CO3)2=MgO+CaCO3+C02 CaC03=CaO+C02The reaction is comprised of, at the first step, the diffusion of CO the decomposition of C0 to CO and O at the surface, the formation of MgO by Oand Mg and of CaCO by CO and Ca and characterized by the speed control of the diffusion of CO and by the mechanism of interface contraction; at the second step, of the formation of CaO by Caand 0 and the diffusion of CO and characterized by the speed control of the duffusion of C0. The activity of calcined dolomite does not increase simply with the rise of temperature but grows and falls under the condition of rise of the temperature and elongation of retaining time, because with the elongation of retaining time the grain size of MgO and CaO grows and lattice deffect is rectified. The activity of the calcination decreases if exposed long time in the atmosphere. Impurities, such as Si0 A1.Fe. and so forth, in the dolomite should be low. Calcination produced under the condition of 1000'C and retaining time 2 hours meets the requirement of reduction.The degree of completion of the vacuum carbothermic reduction of calcined dolomite is high and volatilization rate of magnesium reaches 88.52% if reaction temperature is above 1500 癈 . If condensation temperature falls between 400?50 and temperature distribution is isostatic, condensate takes the shape of fibre, not powder, and contamination by C from the decomposition of CO on the wall of the condenser becomes omissible. With the proceeding of the reaction, pressure in the furnace fluctuates. At 700'C odd, because of the change of coal, pressure in the furnace climbs high the first time. In order to lower the cost of pumping, coking procedure is prerequisite. The high pressure value comes the second time when the reaction of C with calcined dolomite initiates. Therefore, variation of pressure in the furnace mirrors the proceeding of the reaction.