Abstract
The direct reduction process of coal-based composite pellet involves a series of physicochemical reactions. This paper reports a 3D unsteady mathematical model for simulation of heat transfer, mass transfer and chemical reactions inside the pellets. In this model, the pellets are assumed to be continuous porous medium composed of fine spherical particles. User-defined functions (UDFs) program in C language are developed to define chemical reactions, parameters and linked to FLUENT. The results predicted by the model are good agreement with experimental data. In addition, temperature, concentration, pressure and flow field inside the pellets are investigated by the model. Finally, the effects of furnace temperature and pellet diameter on the average pellet temperature, average molar concentration of reducing gases and degree of metallization have been simulated. The results show that the reduction rate is influenced more by the average pellet temperature than by average molar concentration of reducing gases.
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