7TH EUROPEAN COKE AND IRONMAKING CONGRESS - ECIC 2016

The CaO-Fe2O3 (CF) system is the most significant binding phase for fluxed sinter, of which the reducibility becomes a vital index having great importance on the evaluation of sinter qualities. SiO2 is the necessary composition of SFC (SiO2-Fe2O3-CaO) generated from CF. Investigation on the isothermal reduction of CaO·Fe2O3 with addition of 2, 4, 8%(mass percent) SiO2 in a continuous stream of 30% CO and 70% N2 at 850, 900 and 950°C was carried out by thermogravimetric analysis(TGA). The results indicate that CF2S and CF4S has little improvement on reduction degree, but activates the reduction with faster rates than CF. The reduction of samples with 8% silica is not only highly accelerated but also proceeds most easily. The rate analysis revealed that reduction of Fe3O4 to FeO and subsequent process from FeO to Fe overlaps for CF reduction whereas Fe2O3 to Fe3O4 and subsequent process from Fe3O4 to FeO overlaps for CF8S reduction. Reduction of CF8S is described by the Avrami-Erofeev equation with two-dimensional shrinking reaction, whereas reduction of CF2S and CF4S are expressed first by the Avrami-Erofeev equation with two-dimensional shrinking core reaction, followed by the two-dimensional phase boundary controlled reaction.