A Theoretical Model for Assessing the Influence of N_2 on Gaseous Reduction of Iron Ores with CO or H_2

摘要

The influence of N_2 on gaseous reduction of iron ores has yet to be investigated more rigorously. A generalized theoretical model for iron ore reduction that is featured with equimolar counterdiffu-sion of gaseous reactant and product in the presence of an inert component is derived in the current paper, where the influence of N_2 is quantitatively assessed in terms of a normalized overall reduction rate. The results show that N_2 impacts CO reduction of iron ores mainly via the prevailing mechanism of dilution effect and the sole use of D_(AB) in the corresponding ternary system brings merely minor errors. In contrast, especially under conditions of high N_2 fraction and reduction degree, the effect of mass diffusion must be borne in mind for H_2 reduction and the sole use of D_(ab) can lead to marked errors. The main novelty of the present work is the derivations of the theoretical equations fully following the Maxwell-Stefan relation for multicomponent diffusion and the well-known concept of topochemical reaction for gaseous reduction of iron ores. It is hoped that the brief discussion will stimulate further application of the theoretical equations to the development of more versatile models and to studies of the engineering type.