Study On Iron Recovery Process Of Rred Mud On Microwave Carbon Thermal Reduction And Magnetic Separation Methods

Red mud,which is a kind of polluting slag,is produced with the process of alumina production in alumina making enterprises.It brings serious pollution to the ecological environment due to the enormous accumulation of the red mud.Therefore,how to effectively recycle and utilize red mud resources becomes one of the hot topics in recent years.Chemical and phase compositions,the existence state of mineral were studied in this paper by investigating red mud which was produced through bayer process in an alumina enterprise in Shandong.Also,some basic properties of red mud were analyzed in this paper.Microwave direct reduction magnetic separation of red mud was put forward on the basis of studying the microwave absorption characteristics of several experimental raw materials.The four factors,C/O,microwave power,heating time and slag former ratio were studied on the influence of reduction of iron by orthogonal experiment.The reduction products were analyzed by using XRD and other detection methods.The optimum process parameters were obtained with optimized experiment using response surface methodology.The direct reduction of red mud by microwave carbothermal reduction is studied by orthogonal experiment.The maximum reduction degree,average reduction degree and average recovery rate of iron among nine groups of experiments can reach 88,17%,58,14%and 80,76%respectively.The range analysis method is used to analyze the experimental data.The results show that,the effect degree on iron recovery from high to low is microwave power,heating time,C/O and the ratio of addition,which owns the same regular pattern with the grade of iron.Although they both have the same influencing regular pattern,the iron recovery has a larger corresponding range value.So these factors have greater influence on iron recovery than that on iron grade.The analysis of the reduction products by using XRD and SEM shows that almost all Fe₂O₃ in red mud is reduced into Fe₃O₄ and Fe,and the reduction effect is obvious.The experiental is optimized through the response surface method in this paper,which is also redesigned and implemented by Design-Expert experimental design software,and a quadratic model of iron recovery and the influencing factors of C/O ratio,microwave power,heating time are obtained:Y=0.72731+30.55833X₁+0.021267X₂+1.25920X₃+1.38333×10^-3X₁X₂-0.056667X₁X₃+1.32500×10^-5X₂X₃-8.38611X₁²-4.34225×10^-6X₂²-0.011822X₃²The analysis of variance analysis of experimental data shows that the quadratic model is reliability and applicability.The effect of various experimental factors on the iron recovery rate can be observed directly by the response surface model.The optimum technology parameter which obtained by the response surface method is 1.8C/O,2 815 W microwave power,45 min of heating time,which the iron recovery can reach 90,84%.Verified by actual experiments,only 1.85%of the error is existence,which shows that the experiments carried out by the response surface method are successful.