Research On The Technology And Mechanism Of Recovering Iron By Co-Reduction Magnetic Separation From Red Mud And Blast-Furnace Ash

Red mud is the waste residue produced in the process of alumina production,which has small particle size,strong alkalinity and rich iron resources.Blast-furnace ash,a byproduct of the steel industry,contains both carbon and iron oxides.As solid wastes,red mud and blast-furnace ash are mainly stored in landfill and stockpiling,which not only seriously pollute the environment,but also waste precious resources.In order to recover and utilize iron resources in red mud and blast-furnace ash,the furnace ash was used as reducing agent to co-reduction with the red mud.The process and mechanism of recovering metal iron by co-reduction and magnetic separation of red mud and blast-furnace ash were studied.The results showed that SG,HG and GG from different producing areas had different effects on co-reduction and magnetic separation,and the indexes of direct reduced iron?DRI?were different,among which SG obtained the best reduction iron index,HG followed,GG the worst.When SG is used as the reducing agent,direct reducing iron with TFe grade 92.05%and iron recovery 92.14%can be obtained under the conditions of 30%dosage,reduction temperature of 1200?,reduction time of 60min,grinding fineness of-74?m accounting for 62%,magnetic field intensity of0.1T.When HG and GG were used as reducing agents,6%and 9%Ca F₂ were added under the above conditions,the metallic iron with TFe grade and iron recovery both exceeding90%could also be obtained.The phase composition and microstructure of the reduction products were analyzed by X-ray diffractometer and scanning electron microscope.The results show that the reduction of iron ores is insufficient when the blast-furnace ash content of furnace is low,and the main phases of iron ores are metallic iron hercynite and gehlenite.With the increase of blast-furnace ash content,the reduction atmosphere is enhanced,which promotes the reduction of iron ores.In addition,the contents of fixed carbon,iron ore and basic metal oxide in blast-furnace ash have an impact on the process of co-reduction.The higher the content of iron ore and fixed carbon,the better the reduction of iron ore and the accumulation of metallic iron particles.An appropriate amount of basic metal oxide can promote the reduction of iron ore,and increase the melting point and viscosity of the system after excess,which prevents the aggregation and growth of metallic iron particles and leads to the low TFe grade in DRI.The addition of Ca F₂ in the co-reduction system of red mud and blast-furnace ash promotes the reduction of hercynite,produces low melting point of cancrinite and complex silicate minerals containing fluorine,reduces the melting point of the system,promotes the accumulation and growth of metallic iron particles,and improves the TFe grade and recovery rate of DRI.