Reduction behavior of iron oxide and influence of basicity in initial melt formation zone

In order to estimate the influence of initial melt on reduction behavior of iron oxide, heating-up reduction and isothermal reduction were carried out. Samples (FCSA4) were composed of Fe₂O₃, CaO, SiO₂ and Al₂O₃. Four kinds of samples of different composition (basicity: C/S = CaO/SiO₂ = 1.0, 1.5, 1.8, 2.0) were prepared. The reduction rate of FCSA4 with C/S = 1.0, 1.5 was lower than that rate of FCSA4 with C/S = 1.8, 2.0 due to the initial melt formation at the isothermal reduction of 1473 K. The overall reduction rate ka increased with increasing C/S and decreasing of amount of melt. The SEM analysis indicated the influence of melt formation on pore structure of sample. The porosity was estimated by image analysis technique. Defining ka and closing pore ratio ϵ_c, the relational equation between ka and ec represents as follow: k_a = (-0.36 ϵ_c + 18.67) × 10^-5 In the reduction from 1273 K to 1473 K with 21 vol% CO - 9 vol% H₂ - 70 vol% N₂ gas mixture, the rates of all samples didn't decrease. The pore wasn't closed by the effect of H₂ addition. Moreover, the rate of FCSA4M2 with the addition of 0.2 mass% MgO also didn't decrease. The initial melt formation temperature shifted to higher temperature by the addition MgO.