Study On The Recovery Of Iron In Iron Tailings By Magnetized Roasting-magnetic Selection Process

In recent years,the share of China's crude steel production in the world has continued to rise,and by 2019 the share of crude steel production has exceeded 50%.With the continuous expansion of the iron and steel industry,domestic mining has been unable to meet the demand,and the degree of external dependence has reached about 80%,and the development of iron ore resources is imminent.As of 2017,the total stock of iron tailings has exceeded 75×10⁹t,and has not been effectively used,but because of its large amount and rich in iron,it has been given new recycling value.The traditional magnetic roasting-magnetic separation process uses coal as an industrial reducing agent,which not only has high cost,high pollution,and serious air pollution.In this paper,biomass/char is used as a reducing agent instead of coal,and the effect of these on the magnetization roasting-magnetic separation process of Dabaoshan iron tailings was studied.In this paper,starting from the basic properties of Dabaoshan iron tailings,the iron element in the iron tailings is recovered through the magnetization roasting-magnetic separation process.X-ray fluorescence analysis,electron scanning microscope,X-ray diffraction,vibration sample magnetometer and other analysis methods.The main components of iron tailings,surface morphology,mineral composition and magnetic size were analyzed.While the influence of roasting conditions on iron concentrate grade and iron recovery was explored.The main results of the study are as follows:The main elements in the iron tailings sample include:Fe,Si and Al,the iron-containing phases are mainly hematite(Fe₂O₃)and goethite(Fe(OOH)),and the gangue minerals are mainly quartz(Si O₂)and oxidation Aluminum(Al₂O₃).The iron grade in the iron tailings sample is 31.79%,which belongs to iron-poor ore.When activated carbon is used as a reducing agent,it is found through orthogonal experiments that the roasting temperature has the greatest influence on the magnetization roasting-magnetic separation process.Further,through the single factor test,the optimal roasting conditions for iron recovery from the magnetization roasting-magnetic separation process were determined as follows:roasting temperature 800?,roasting time 40 min and activated carbon addition 8%.The grade of magnetic concentrate is(56.05±0.18)%,and the iron recovery rate is(94.89±0.37)%.Phase analysis found that the iron-bearing phase in iron concentrate is mainly magnetite(Fe₃O₄).It shows that when activated carbon is used as a reducing agent,the iron elements in iron tailings ccould be effectively recycled,which provides basic data support for the subsequent research on iron recovery.When coal,straw,coffee grounds and activated carbon are used as reducing agents,comprehensive considerations are obtained when the roasting conditions are as follows:roasting temperature 800?,roasting time 40 min and reducing agent addition amount 12%.The resulting iron concentrate grades are(52.46±0.52)%,(54.41±0.29)%,(57.77±0.44)%and(58.62±0.32)%.The iron recovery rates are(82.12±1.91)%,(93.16±1.81)%,(92.64±1.48)%and(91.48±0.79)%,respectively.Thermogravimetric analysis shows that straw and coffee residue can form fixed carbon at 600?,indicating that the reduction process could occur when the temperature exceeds 600?.Compared with coal and activated carbon,the required roasting temperature has decreased.The magnetic analysis results show that the saturation magnetization of the iron concentrate could be effectively improved,making the subsequent weak magnetic separation process easier to implement.Considering the cost of magnetization roasting process,sawdust biomass with large quantity and low price is used as reducing agent.The roasting results show that the best roasting conditions are:roasting temperature of 750?,sawdust addition of 15%and roasting time of 40 min.Under this condition,the iron concentrate grade is(62.84±1.02)%,and the iron recovery rate is(94.03±0.78)%.The phase structure analysis shows that the iron-containing phase of iron concentrate is mainly magnetite;the magnetic analysis result shows that the saturation magnetization of iron concentrate is 46.01 emu/g.Compared with the raw ore,the saturation magnetization is increased by 98.6%,indicating that the addition of sawdust could effectively improve the magnetic properties of iron tailings,means could provide good conditions for subsequent magnetic separation.Therefore,when sawdust biomass is used as the reducing agent in the magnetization roasting-magnetic separation process,the iron element in the iron tailings could be effectively recovered,and a better recovery effect could be obtained.