Fundmental Study On Reduction-Dressing New Process Of High-iron Gibbsite Based On Hot Briquette

With the rapid development of steel and alumina industry, the lacking iron ore and aluminum source have been important bottlenecks of steel and alumina industry respectively. As a complex mineral containing Fe and Al, the development and utilization of high-iron gibbsite have been an important issue. As for the comprehensive utilization of high-iron-gibbsite, many researches have been carried out, and several treatments have been presented successively including the flotation of Al and Fe, Al first then Fe and first Fe then Al. Owing to the disseminated agglutination and paragenesis of Fe and Al in high-iron gibbsite, dressing Fe or Al from high-iron gibbsite is extremely difficulty. So far, the high-iron-gibbsite still hasn’t been unutilized efficiently.Aiming at the material characteristics and current research situation high-iron gibbsite, a new process of reduction-dressing for high-iron gibbsite based on hot pressing is given in this study. Through the study on preparing high-iron gibbsite CCB, the influences of carbon ratio, particle size of bauxite and soft coal on its compression strength have been researched. And the reasonable processing parameters have also been determined. In reduction-dressing research, the influence rules of the processing parameters, including the magnetic field strength, temperature and time of reduction, carbon ratio on process indexes are all considered. Several conclusions are obtained as follows:(1) Through the process based on hot briquette of reduction-dressing process, the high-iron gibbsite can be separated of Fe and Al. The yield both are over85%.(2) The effect of carbon ratio on high-iron gibbsite CCB compression strength is shown observable. With the increasing of carbon ratio, a remarkable improvement of compression strength can be obtained. Refining of high-iron gibbsite powder is contributed to enhance the compression strength signally. By refining of soft coal, the compression strength can be improved, but in a small extent. Generally as for compression strength, appropriate processing parameters have been gained:the carbon ratio is not less than1.00, the particle size of high-iron gibbsite powder and soft coal both are not more than100mesh. Under these conditions, the compression strength is more than1000N per one.(3) Appropriate processing parameters of high-iron gibbsite CCB reduction-dressing are obtained:the carbon ratio is1.00, the particle size of high-iron gibbsite powder and soft coal both are not more than100mesh, reduction temperature is not less than1350℃, reduction time is not less than70min, the magnetic field strength is selected at45mT. Under these all conditions, indexes of the new process are given as follows:the grade of dressing product is78.46%, the metallization is achieved91.29%, the yield of iron reaches87.01%, besides the grade and yield of alumina is55.03%and86.21%separately in tailings.(4) The product of dressing is the iron powder with high metallization, through the further disposition, which can be used in steel production. The tailings of dressing are high grade sources containing alumina, which can also be used as superior raw material in alumina industry.(5) The thermodynamic analysis showed carbon thermal reduction of high-iron gibbsite requires a higher temperature and higher concentration of CO; At the end of reduction, the iron phase mainly exists in the form of elemental iron, and a small amount of iron in the form of Fe3C and the presence of very small amount of Fe in Al1.98Fe0.02O5Si; aluminum-containing phase exist in the form of Al2O3, Al2.272O4.864Si0.728, Al1.98Fe0.0205Si.