Investigation On Iron Removal From High-iron Bauxite Based On Suspension Magnetization Roasting

As the non-ferrous metal with the largest demand and output,aluminum is the basic material for traditional applications such as aerospace,transportation,electronics,and construction.China is a veritable alumina producing country,but the bauxite resource reserves in the world account for a very low proportion,and most of them are difficult to handle bauxite resources.At present,more than 50%of China’s bauxite is imported,and its dependence on foreign countries has been increasing year by year.Therefore,the effective use of refractory aluminum resources is the only way to ensure the sustainable development of China’s aluminum industry.China’s high-speed iron bauxite resources are abundant,and its prospective reserves are 1 to 1.5 billion tons.However,the aluminum and iron inlays in this type of ore are closely integrated with conventional beneficiation,roasting,and smelting processes.High-speed iron bauxite has become a typical type of difficult-to-treat sluggish ore.Even if the Bayer process is adopted,there are technical and economic problems such as harsh dissolution conditions,large red mud production,and high production costs.Therefore,the development of economical and technically feasible high-speed bauxite aluminum and iron separation technology has important strategic significance and practical value for the healthy and sustainable development of China’s alumina industry.In this paper,a high-iron bauxite from Guangxi is taken as the research object.The content of Al2O3 is 51.66%,the content of TFe is 19.83%,the content of SiO2 is 2.59%,and the ratio of aluminum to silicon exceeds 19.The results of process mineralogical research show that aluminum mainly exists in the form of gibbsite,and partly in the form of gibbsite and kaolinite;iron is mainly present in hematite and goethite with a distribution rate of 96.42%;Stone minerals include quartz,chlorite,clay minerals,etc.The fine particle size increases the difficulty of removing impurities.The boehmite is mainly coarse-grained,the gibbsite and iron minerals are mainly fine-grained,and the aluminum and iron minerals are closely related,and some aluminum(iron)is similar in quality.The form is distributed in iron(aluminum)minerals,which is difficult to separate by physical beneficiation methods.Based on the characteristics of process mineralogy,a laboratory-type suspension roaster was used to carry out a new process of pre-roasting—suspension magnetization roasting—magnetic separation on the effect of aluminum and iron separation on high-speed bauxite.The suitable roasting process parameters for the roasting-suspension magnetization roasting-magnetic separation process are:the fineness of the roasting raw material is-0.074mm,the proportion is 40%,the pre-baking temperature is 750℃,the reduction temperature is 600℃,the total gas volume is 800mL/min,and the hydrogen concentration is 25%,and roasting time 4min.Under the above optimized roasting process parameters,the reduction roasting product can obtain a TFe grade of 5.67%,an Al2O3 content of 77.18%,and an aluminum recovery rate of 80.64 under the sorting conditions of grinding fineness-0.045mm accounting for 70%and magnetic field strength of 114kA/m,Aluminum concentrate products with an iron removal rate exceeding 85%,and high-alumina iron concentrates with a full iron grade of 46.91%and an Al2O3 content of 26.95%.The inspection and analysis of the reduction products and magnetic separation products can be seen that the iron oxide in the original ore is almost completely converted into magnetite,the magnetic moment and specific magnetic coefficient of the unit mass are significantly improved,and the difference in magnetic properties can make the separation of iron and aluminum change.much easier.Thermodynamic calculations and XRD phase analysis show that in the pre-roasting stage,under the condition of sufficient reaction,dehydrated bauxite will undergo dehydration and decomposition to produce α-Al2O3(corundum).Both goethite and limonite will undergo dehydration and decomposition.Hematite is formed;in the reduction and roasting stage,hematite is easily reduced to magnetite by hydrogen.To ensure the reduction of over-reduction to metal iron or bainite,the reduction time and hydrogen concentration should be strictly controlled.The chemical process of iron,magnetic analysis,and microstructure analysis were used to study the mechanism of the pre-roasting stage and magnetization reduction roasting stage of high-iron bauxite.In the pre-roasting stage,the crystallization water and structure water are removed.The released gas makes the ore particles loose and porous,and the interior is full of pores and cracks,which helps the subsequent reduction roasting process.During the magnetization reduction roasting stage,the reducing gas Hydrogen can smoothly contact the iron oxides in the particles through the pores of the particles and react to form magnetite,thereby increasing the magnetic difference between iron oxides and aluminum oxides,and laying a foundation for the efficient separation of iron and aluminum in high iron bauxite.In the end,which opened a new way for the efficient development and utilization of high-speed bauxite.The research results in this paper have enriched the theoretical system of aluminum and iron separation technology for high-speed bauxite,not only providing basis and basic parameters for the development and utilization of new processes for pre-baking,suspension magnetization,and magnetic separation of high-speed bauxite,but also for other complex and difficult-to-select iron The efficient separation and utilization of aluminum-associated resources also has good reference significance.