Study On Producing Primary Al-Si Alloy From Oil Shale Residue By Electrothermal Reduction And Utilization

Along with the shortage of oil and natural gas resources, oil shale shows its importance as an alternative energy. Oil shale resources reserves reaching118.3billion tons in our country, but the emissions of oil shale residue is0.15billion tons because of the higher slad in oil shale. If the oil shale residue is not be used, it will not only waste the resources, but also pollute the environment. At present, oil shale residue is mainly used to produce some low-value commodities, such as brick, cement. With high economic value and ues value, it is significant for the study on producing primary Al-Si alloy from oil shale residue by electrothermal reduction.In this paper, the process of producing primary Al-Si alloys by using oil shale residue as raw material, and soft coal as reductant in arc furnace was studied. According to the composition of A130%-Si45%in Al-Si alloys, charge ratio was calculated exactly. The results shown that the charge ratio was oil shale residue:soft coal:alumina:pulp powder: water=100:52.3:6.2:14.3:16.2. Based on these, the influences of pressing pressure, dry agglomerant content, moisture content and particle size on the properties of pellets were investigated by single factor using the compressing strength and pore ratio as indexes. The optimum conditions for the properties of pellels are as follows:the materials mixed in an appropriate ratio and ball milling3h, the pressing pressure25MPa, dry agglomerant content9%, moisture content11%. Under the optimum conditions, the compressing strength was26.35MPa, pore ratio is18.15%, meet the smelting requirements. The properities of sintering condition were also investigated. With the temperature rising and sintering time prolonging, the pore ratio of pellets increased, the compressing strength decreased, the decreasing amplitude was great specially the sintering temperature exceeding800℃. When bellowed500℃, the pellets hardly conducted, ather that the resistivity decreased apparently. It’s essential for the electrothermal reduction to have a faster heating speed.The thermodynamic analysis indicated that producing primary Al-Si alloy from oil shale residue by electrothermal reduction needed higher temperature, the temperature was high to2000～2100℃. In the process of smelting operated in arc furnace, the suitable voltage was 24～27V, the suitable current was460-470A, carbon content was94%, the smelting process was successful and high purity alloy was produced. The alloy abtained composed of4phases, including mainly primary Al-Si alloy phases. The Al content was25.4%, Si content was33.6%, Fe content was17.1%. The produced fume was mainly composed of Al2O3and SiO2.The reduction process of producing primary Al-Si alloy in arc furnace was studied. During pellets movement from low temperature areas to high temperature areas, it showed that oil shale residue resolved at lower temperature, then silica reacted with carbon and generated SiC and a little Si. When the pelltes entered the center zone of electric arc, alumina begain to reacte with carbon and generated Al-Si alloy.Primary Al-Si alloy used as reductant for Mg production was tested in the vacuum thermal reduction process, the results indicated that primary Al-Si alloy as thermal reductant is feasible. The pressing pressure30MPa, CaF2content3%, excessive reductant content10%, reduction temperature1200℃, reduction time120min, the reduction rate of magnesium reached to89.92%. Temperature1150℃, reduction time150min, the reduction rate of magnesium reached to84.98%.