Study On Magnetic Separation Technology Of Mixed Rare Earth Tailings From Iron Ore Separation By Reduction Roasting With Coal And Calcium

China has become the world’s largest producer of rare earths with its enormous storage, production and supply as well as rare earth is recognized as the most strategic resources around the world. Iron and Steel company of Baotou uses iron ore of baiyunebo as raw materials. However, since it put into production, most of rare earth, niobium and thorium resources of the raw material have been put into the tailings dam, which cause the waste of resources of rare earths, the pollution of environment and the possible hazard of geology. So comprehensive recycling and utilization of mixed rare earth tailings is imminent in the tailings dam. Based on mixed rare earth tailings from iron ore separation as the research object, the experiment studies the technology of reduction roasting - weak magnetic separation to recycle iron of mixed rare earth tailings. To achieve the goal of promoting bastnaesite and monazite decomposition into the rare earth oxides and restraining the fluorine escape during the process of bastnaesite decomposition under the reduction roasting temperature, a new clean recycle technology of mixed rare earth tailings is developed with fluorine fixing materials as additives in the materials.The experiment uses calcium-based reagent to control the transgression of fluorine in the reduction roasting process about mixed rare earth tailings from iron ore separation. This experiment respectively takes CaCO3, Ca(OH)2, CaO as additives to conduct a series of reduction roasting-weak magnetic separation experiments on iron tailings containing mixed rare earth. This experiment investigates the impact of calcination temperature, coal blending quantity, calcination time and additive dosing on magnetization reduction effect, weak magnetic separation effect, mixed rare earth minerals decomposition, and fluorine escape inhibition effect, by the method of XRD, DTA-TG, SEM, etc.This experiment taking CaCO3 as additives shows that:the iron recovery reaches to 80.529% when the roasting temperature is 630℃. With the coal content of 4%, grade of magnetic concentrate reaches to 51.09%. Through the analysis, the reaction of CaCO3 and REOF can prevent the escape of fluorine. CaCO3 can react with monazite. When the roasting temperature of 610℃, roasting time of 120min, CaCO3 content of 30%, the monazite decomposes fully. The highest rare earth recovery in this situation can be 90.471% with the 9.76% rare earth grade.This experiment taking Ca(OH)2 as additives shows that: the iron recovery reaches to 88.641% when the temperature is 630℃. With the coal content of 2.827%, the experiment can get good effect of magnetization and iron recovery of 77.678%. This experiment also shows that the absorption of CO2 by Ca(OH)2 promotes the decompose of the bastnaesite at low roasting temperature, the reaction product of CaCO3 can fix fluorine. The fixed rate of fluorine can be 98% when Ca(OH)2 content of 5%. The highest rate of rare earth recovery in this situation can be 93.176% with the 10.54% rare earth grade.This experiment taking CaO as additives shows that:the iron recovery reaches to 88.525% when the temperature is 630℃. The reaction of CaO and REOF can prevent the escape of fluorine. CaO can react with monazite. When roasting temperature of 610℃, roasting time of 60min, CaO content of 10%, the monazite decomposes fully. The highest rate of rare earth recovery in this situation can be 96.019% with the 11.40% rare earth grade.