Study On Comprehensive Utilization Of Aluminum, Iron And Sodium From Bayer High Iron Red Mud

A great amount of red mud generated from Bayer alumina production has to be piled, which not only occupies land but also pollutes soil, underground water and air. It is an effective method to realize the harmlessness and reduction of red mud through the high efficient utilization of valuable elements in red mud.In this paper, high iron red mud from Bayer process was taken to recover alumina, sodium oxide and ferric oxide by the process of reduction sintering, leaching and magnetic beneficiation. The theory and technology of this process were researched. The mechanism and conditions of the growth of ferrite grains in the reduction sintering process with coal base have been clarified in this paper. The methods to control the amount of liquid phase in the reduction sintering process and to widen the width of sintering temperature were proposed. The suitable conditions of reduction sintering and magnetic beneficiation were determined.The main results obtained are as follows:1) Na2O-Fe2O3which is more readily reduced by carbon is rapidly formed by the reaction of ferric oxide and sodium carbonate, lowing the initial reduction temperature of Fe2O3-Na2CO3-C system and accelerating the reaction. Na2O·Fe203also can promotes the growth of ferrite grains in the reduction products which favors the magnetic separation.2) The amount of liquid phase in the reduction sintering process is controlled and the width of sintering temperature is widened by adjusting the composition of raw material. Experimental results indicate that the recovery of alumina and sodium can reach90%respectively with calcium ratio of2.0, alkali ratio of1.0and sintering temperature of1100℃～1200℃.3) The iron in leaching residues can be extracted efficiently by twice magnetic beneficiation process containing one roughing operation and one cleaning operation. The iron recovery can reach90%with the iron content in concentrate of70%under the suitable conditions of reduction sintering and magnetic beneficiation process.4) The amount of the final residue is approximately30%of red mud after recovering the alumina, ferric oxide and sodium oxide. The rare metals present in high iron red mud such as scandium, titanium, tantalum and niobium are enriched in magnetic tailings, laying the foundation for the further comprehensive utilization of the residues.