Abstract
A mathematical model for the kinetics of reduction of porous wustite pellets with CO-H2 gas mixtures was developed on the basis of the unreacted-core model. In this model, (1) the water-gas shift reaction with reduced iron as catalyst was taken into consideration, and (2) the diffusion rates of gases through the gasfilm and the product iron layer were evaluated using the Stefan-Maxwell equations for multi-component gas diffusion. Porous wustite pellets were reduced with CO-H2 gas mixtures(5Nl/min) at 900°C, and experimental data obtained were analyzed by the model. The results were as follows:
(1) The effect of the water-gas shift reaction on the reduction kinetics was negligibly small.
(2) Relation between the reduction rate and bulk gas composition showed negative deviation from linearity. It was due to the dominant contribution of diffusional resistances through the product layer to the overall reaction rate.
(3) The values of rate parameters in the model varied with bulk gas composition. When bulk gas composition was constant, however, the effects of the changes of gas composition within the pellet during reduction on the values of the parameters were negligibly small, and therefore the values can be treated as constants.
