Kinetics and mechanism of smelting reduction of fluxed chromite Part 1 Carbon–chromite–flux composite pellets in Fe–Cr–C–Si melts

Abstract

Experimental studies on the smelting reduction of fluxed carbon–chromite composite pellets in Fe–Cr–C–Si alloys were carried out at 1520–1600°C. The reduction reaction was found to be favoured by high temperatures, a high lime addition in the pellets, a long pellet dissolution time, and a moderate melt Cr content. For a given CaO addition, however, the reduction rate initially slowed before increasing with an increasing silica addition to the pellets. A three stage reduction mechanism is proposed. The first stage is very likely to be controlled by solid state and/or gas diffusion with an apparent activation energy of 472 kJ mol^-1 for pellets fluxed with 15%CaO and 25%SiO₂ . The third stage proceeds via smelting mechanisms, with mass transfer in the slag phase possibly rate controlling.