Research On Optimization Of Fluidized Reduction Process Of Brazilian Fine Iron Ore

In this paper,Brazilian fine iron ore is taken as the main object of fluidized reduction.Record the data of fine iron ore reduction under different reduction conditions.The influence of different conditions on the reduction of Brazilian fine iron ore is analyzed.The surface morphology of reduced fine iron ore is observed by a scanning electron microscope,and the sticking mechanism of fine iron ore is described.Through the orthogonal experiment,the primary and secondary effects of various factors on the reduction of Brazilian fine iron ore were discussed,and the optimal operation parameters were obtained.The main conclusions are as follows:(1)Under different reduction conditions,the fluidization status of the fluidized bed is different,indicating that changing the reduction temperature,reduction time,reducing gas linear velocity,mineral powder particle size and other conditions can improve the fluidization status.Through a simple comparative analysis method,the optimal operating parameters of reducing Brazilian fine iron ore under atmospheric pressure are as follows: reduction temperature 1023 K,linear velocity 0.6m/s,reduction time 50 min,the particle size range of 0.15mm?0.18 mm.(2)Through pre-experimental analysis,it can be concluded that pressurization and addition of carbon powder can improve the fluidized state of reduced iron ore powder in the fluidized bed.For the metallization rate,the optimum process parameters are reduction temperature 1023 K,gas linear velocity 0.6m/s,reduction time 70 min,reduction pressure 0.25 MPa,added carbon powder mass fraction 2%,added carbon powder particle size 4?m?7?m,the main factor affecting the metallization rate is reduction temperature;For the sticking ratio,the optimal process parameter level selected are 6% by mass fraction of added carbon powder,reduction temperature of 973 K,particle size of added carbon powder 4?m?7?m,gas linear velocity 0.6m/s,reduction pressure 0.25 MPa,reduction time 30 min,the main factor affecting the bonding ratio is the quality of the added carbon powder.The optimal operating parameters were analyzed by a comprehensive balance method: temperature923K?1023K,the linear velocity of reducing gas 0.6m/s,reduction time30min?50min,reduction pressure 0.25 MPa,the particle size of carbon powder between 4?m ?7?m,and carbon powder mass content of 2%?6%.(3)The fluidization state of fine iron ore particles in the reduction process is mainly affected by reduction kinetics.The experimental results show that reducing the concentration of reducing gas,reducing the temperature,and reducing gas linear velocity can significantly reduce the reduction rate and improve the fluidization performance of fine iron ore particles.The variation of fluidization time is in good agreement with the kinetic equation of the gas-solid unreacted nuclear model,which indicates that the change of fluidization time is determined by reduction kinetics.(4)Six kinds of iron ore fines,including Australia mine,Brazil mine,King's fine ore,Newman mine,Zhangzhuang mine,and Gushan mine,were used as raw materials to carry out fluidization experiments in a hot visible fluidized bed.The results showed that the reaction effect was excellent under the optimal operating parameters,indicating that the optimal reduction process has certain universality.The results show that adding carbon powder can improve the fluidization state of six kinds of fine iron ore,among which the stick ratio of Brazilian ore,Newman ore,and King's fine ore decreases most obviously,and the fluidization state is good;Under the condition of adding carbon powder,fine granular metal spheres are formed on the surface of ore powder,which can inhibit the formation of iron whiskers and reduce the sticking force between iron ores.