Study On Producing Magnesium By Vacuum Aluminothermic Reduction Of Magnesite And Producing High Density Magnesia-alumina Spinel

Magnesium and its alloy have numerous unique properties, such as low density, good vibration damping, superior mechanical properties and recycling property. Magnesium are widely applicable that will be the third engineering material following steel and aluminum. The methods of extracting magnesium are two different technologies:molten salt electrolysis and vacuum thermal reduction of MgO. Pidgeon process is the most important production method of magnesium in China which has high energy consumption, high CO2emissions and its reduction residue cannot be used efficiently. The method preparation of magnesium by vacuum aluminothemic reduction of magnesite and preparation of magnesite-alumina spinel by reduction residue not only reduce raw material consumption and energy consumption, but also can make efficient use of the reduction residue,thus,it is a energy saving and environmental protection green metallurgy technology.The experiment includes two parts, one is study on production of magnesium by vacuum aluminothemic reduction with magnesite as raw material and the other is study on preparation of magnesite-alumina spinel by using the reduction residue.The results showed:(1) Magnesium is preparated with magneiste as raw material and aluminum as reductant according to the chemical reacting equations4MgO+2Al=MgOAl2O3+3Mg. The experimental results show that the best technological condition is reduction temperature for1200℃, reduction time for2hours, briquetting pressure for120MPa, and added amount for reductant is5%. In the condition, reduction rate of magnesium is95%. At the same time the main phases in reduction residue are MgAl2O4, Al2O3and MgO.(2) Adding villiaumite in the reduction process can make reduction rate of magnesium improve3.17%and utilization rate of reductant improve3.18%.(3) Preparation of magnesium with magneiste as raw material and aluminum as reductant according to the chemical reacting equations3MgO+2Al=Al2O3+3Mg. This method’s reduction rate of magnesium is84.7%. It can improve the yield of Mg per unit weight of raw materials but the utilization rate of reductant was decreased.(4) The effects of sintering temperature, sintering time and briquetting pressure on apparent porosity and bulk density are investigated. Preparing magnesite-alumina spinel in the best technological condition which is sintering temperature of1700℃, sintering time of3hours and briquetting pressure of120MPa can get magnesia-alumina spinel which Al2O3content of72%, bulk density of3.204g/cm3, and apparent porosity of1.22%.Energy consumption cost and production cost of vacuum aluminothermic reducion are compared with current Pidgeon process. The former method which has lower energy consumption and nonwaste residue produced has a promising prospect.