Rate-determining steps for reduction in magnetite-coal pellets

A comprehensive modelling approach and experimental results were used to test possible rate-determining steps for direct reduction in pellets containing fine magnetite and coal. In support of the modelling approach, a survey of rate constants from the literature is presented. Heat transfer was found not to be limiting for the reduction reaction (although conduction within the pellet limits the rate of devolatilisation of the coal). For average rate constants, the chemical reactions are under mixed control (by the reduction and Boudouard reactions). The reductant also affects the product quality. since most of the sulphur in the reductant is retained in the direct-reduced product. (C) 2002 Elsevier Science Ltd. All rights reserved.