Effect of reducing agents on reducing atmosphere in coal-based direct reduction of beach titanomagnetite

Abstract

Beach titanomagnetite (TTM) provides a cheap alternative source of Fe and Ti, but this ore is difficult to process to make suitable concentrates for the blast furnace. Recently studies showed that it is feasible to separate Fe and Ti by coal-based direct reduction. In this study, beach TTM was selected as the research object, the effects of reducing agents on reducing atmosphere in coal-based direct reduction of beach TTM were analyzed, and the role of volatiles was also studied. The results showed that when bitumite and coke were used as reducing agents of TTM, the CO produced from volatiles was involved in the reduction reaction, and the generated CO₂ provided the raw material for the reaction of TTM. The reduction effect of bitumite was better than that of coke. The reason is that bitumite+TTM had a higher gas generation rate and produced a higher CO partial pressure, while coke+TTM had a lower gas generation rate and produced a lower CO partial pressure. When graphite was used as a reducing agent, there was a solid-solid reaction in the early stage in the reaction. With the continuous accumulation of CO₂, the Boudouad reaction started and accelerated. Graphite+TTM also produced a higher CO partial pressure.

摘要

海滨钛磁铁矿资源储量丰富，是钛、铁资源的重要来源，但是采用常规选矿方法难以得到用于高炉冶炼的铁精矿。研究表明，采用煤基直接还原工艺可以实现钛磁铁矿的钛铁分离。本文研究了还原剂对钛磁铁矿煤基还原过程中还原气氛的影响，并分析了挥发分的作用。结果表明，当烟煤和焦炭作为钛磁铁矿的还原剂时，产生的CO参与了还原反应，生成的CO2进一步作为碳热还原反应所需要的原料。同时发现烟煤的还原效果优于焦炭，这主要是因为烟煤与钛磁铁矿混合物具有较高的气体生成速率，可以产生较高的CO分压值，而焦炭与钛磁铁矿混合物具有较低的气体生成速率，导致产生的CO分压值较低。当石墨作为还原剂时产生和烟煤相似的还原效果，在反应的早期阶段存在固-固反应，随着CO2的不断累积，Boudouad开始反应并加速，产生了较高的CO分压值。