Research On Effect Of Gangue Compositions On Carbon Composite Pellets Reduction

Circumstances including shortage of high grade ore and coking coal, improvement of environmental protection standard and adjustment of product structure make it more important to develop the technologies of blast furnace ironmaking with low coke rate and non-blast furnace ironmaking. Carbon composite pellet technique developed in above background makes it possible to produce the direct reduction iron and utilize ferro-waste and low grade complex iron ore.With respect to the reduction mechanism and influencing factors on strength of carbon composite pellets there have been relatively deep studies recently, which give vital support to the promotion of application and development of carbon composite pellet techniques. However, the research on effect of gangue compositions on reduction carbon composite pellet reduction is less. Based on this situation, the following investigations and results are included in this paper.(1) The isothermal reduction of carbon composite pellets with gangue compositions of 3-9%Si O2, 0.2-0.6%Ca O, 0.5-1.0%Al2O3 and 1-2%Mg O in N2 atmosphere was investigated at the temperature range of 1100-1200?. The results show that formation of fayalite for the existence of Si O2 and Ca O?Fe O?2Si O2 produced by Ca O can decrease the reduction rate of carbon composite pellets, while Al2O3 and Mg O increase the reduction rate of carbon composite pellets by decreasing the amount of fayalite formation at the temperature range of 1100-1150?.(2) The metallization rates of carbon composite pellets of different gangue compositions after reduction at the constant temperature of 1100?, 1150? and 1200? are 66.40-76.44%, 72.42-89.71% and 79.93-93.79%, respectively and increase with rising temperature. Meanwhile, reduced iron melts and aggregates a ferro-layer on the pellets and granular iron in the pellets.(3) Apparent activation energies for the reduction of carbon composite pellets under carbon gasification reaction as limiting step are 142.16-227.76 k J/mol and apparent activation energies for the reduction of carbon composite pellets reduction under interfacial as limiting step are 132.49-211.62 k J/mol. The reduction process of carbon composite pellets is controlled by carbon gasification reaction and interfacial reaction.