KINETIC-MODEL FOR REDUCTION OF IRON-OXIDE IN MOLTEN SLAGS BY IRON-CARBON MELT

Rate of reduction of iron oxide in iron and steelmaking slags by mass contents of dissolved carbon (> 3%) in molten iron depends upon activi ty of FeO, temperature, mixing of bulk slag and other experimental con ditions. A general kinetic model is developed by considering mass tran sfer of FeO in slag, chemical reaction at gas-metal interface and chem ical reaction at gas-slag interface, respectively, as the three rate c ontrolling steps. A critical analysis of the experimental data reporte d in literature has been done. It is shown that in the case of slags c ontaining mass contents of less than 5% FeO, the reduction of FeO is c ontrolled by mass transfer of FeO in slag plus chemical reaction at ga s-metal interface; when slags contain more than 40% FeO, the reduction of FeO is controlled by chemical reaction at gas-metal interface plus chemical reaction at gas-slag interface; at intermediate FeO mass con tents (between approximately 5 and 40% FeO), the reduction of FeO is c ontrolled by all three steps, namely, mass transfer of FeO in slag, ch emical reaction at gas-metal interface and chemical reaction at gas-sl ag interface. The temperature dependence of rate constant for the gas- slag reaction is obtained as: In k2 = -32345.4(+/-6128)/T + 19.0(+/-3. 42);sigma(lnk2,1/T) = +/- 0.3. where k2 is expressed in mol m-2 s-1 ba r-1. The mass transfer coefficient of iron oxide in bulk slag is found to vary in the range 1.5 x 10(-5) to 5.0 x 10(-5) m/s, depending upon the slag composition as well as experimental conditions.