Experimental Investigation About High-temperature And High-bed Direct Reduction Based On Ore-coal Composite Pellet

With the rapid development of blast furnace ironmaking process, its problem is also becoming more and more urgent. In view of economic-social environment, the development of alternative coke-free ironmaking process is necessary and important to sustainable development, In the development of direct reduction process all around the world, metallurgists did a lot of work about the investigation of the new processes. In this paper mainly did experimental study and theoretical analysis about the new developed high temperature and high bed direct reduction process based on ore-coal composite pellets.In this paper, we mainly discussed using high temperature and high bed process to deal with iron ore and compared with single bed in production indexs like metallization, productivity and so on. Also special ores like laterite-nickel ore is also tried to be used in this process, In the base of analysis about reduction thermodynamics and kinetics, we determine the best condition by comparing the size of ferronickel particles. We also used some testing methods like XRD, SEM, EDS to investigate the features like phase compositions, microstructure of materials after reduced.The conclusions of present work include:(1)In lab scale, the optimum parameters for high-temperature and high-bed direct reduction include that, C/O=0.8, reduction time is50mins, and keeping insulation board outside the furnace. At these conditions, degree of metallization of top4layers is above90%, and that of the5th layer is higher than77%. The average degree of metallization of the whole bed is about87.6%. The metallic particles of DRI (Direct Reduction Iron) are dense from metallographies.(2) The degree of metallization and productivity of high-temperature and high-bed direct reduction are much higher,87.6%and56.83kg/h.m2respectively, compared with single bed. Also, the carbon rate is lower (about266.81kg/tFe), which is benefit to decrease energy consumption and CO2emission.(3) Laterite-nickel ore is also tried to be used in this process. Parameters like reduction time, temperature and amount of flux is considered in comparing the size of ferronickel particles. IPP6.0is used to analysis the size distribution of ferronickel particles and the effect on magnetic separation. (4) We determined that the best condition for the growing up of ferronickel particles is0%CaO,45mins,1400℃. Under that condition, the grade of nickel in metal phase is3.77%, iron and nickel recovery is only70%, that index can be increased by improving the magnetic separating condition. Through the result of XRD and EDS we know that ferronickel metal phase mainly includes such phases like iron, ferronickel, and augite. However tailings mainly contains such phases like augite, quartz and so on.The project is financially supported by NSFC51074040and basic scientific research fund project N120402007. The consequences of present work can provide theoretical basis for the implement of high temperature and high bed direct reduction and is referable for the setting of appropriate operating parameters. Also, it provides a new choice for developing our country’s coke-free ironmaking processes.