Carbothermic reduction in the combustion bed packed with composite pellets of iron oxide and coal

Process feasibility has been experimentally studied on a new reduction concept using the composite pellets of iron ore and coal powders in their combustion bed. A key to realize this concept will be a method to prevent reoxidation of metallic iron formed during the process. To examine the optimum measure, reduction experiment using a single composite tablet was first conducted. Coating the tablet with a CaO bearing material, i.e., Ca(OH)₂ or CaCO₃ powder, gives a certain suppression effect on the reoxidation at high temperature. On the basis of this result, reduction experiment in the combustion bed packed with the composite pellets were carried out under various conditions. An proper condition could not be found to perfectly prevent the reoxidation of metallic iron. However, the reoxidation was significantly suppressed by the admixing of CaO bearing material to the mixture or the coating it around the composite pellets. The maximum reduction and metallization degrees obtained were 72 and 64%, respectively. It suggests that the proposed process has a potential to produce partially-reduced iron burdens to a subsequent reduction/melting process such as the blast furnace.