Application of Response Surface Methodology to Assess the Combined Effect of Operating Variables on the Direct Reduction of Fe2O3 by Coal Volatiles

The reduction of Fe2O3 powder at the top layer by the volatiles from high volatile (HV) bituminous coal at the bottom layer of a multilayer powder geometry including a separating alumina layer was studied. The simultaneous effects of the alumina layer thickness, time, temperature and the weight of coal on the amount of reduction and coal devolatilization were studied by implementing a rotatable central composite design (CCD) based on response surface methodology (RSM). RSM successfully revealed the influential operating variables and the effects of the interactions between the variables on the reduction of Fe2O3 and devolatilization of coal. The phase evaluation of various iron oxide phases and metallic iron was obtained through XRD. The XRD results showed that the reduction of pure Fe2O3 to metallic iron proceeded through a stepwise reduction via Fe3O4 and FeO. It was also found that the reduction of iron oxide by coal volatiles occurred internally uniformly at the first stage of reduction to form Fe3O4; however, the behavior became nearly topochemical as the reduction proceeded.