A novel selective reduction roasting process has been successfully developed for utilizing the complex tin, zinc-bearing iron concentrates by the authors' group. In this study, the isothermal reduction kinetics of SnO2 and ZnO in the preheated iron ore pellet containing tin and zinc was investigated in a 20%CO-80%CO2 gas mixture at temperatures of 950 degrees C, 1000 degrees C, 1050 degrees C and 1100 degrees C. It was found that the reduction reaction of SnO2 -> SnO (g) was controlled by interfacial chemical reaction at 950 degrees C and 1000 degrees C, whereas it was controlled by combination of chemical reaction and gas internal diffusion at 1050 degrees C and 1100 degrees C. As for the reduction reaction of ZnO -> Zn (g), it was always controlled by the interfacial chemical reaction at temperatures of 950 degrees C-1100 degrees C. (C) 2013 Elsevier B.V. All rights reserved.