Simulation of iron ore reduction in a fixed bed

A simulation of direct reduction in a fixed-bed process of iron ore is presented. Simulation is done with a model which takes into account the bed characteristics, including the reaction kinetics, the thermal effects, and the quality and flow of the reducing gas. It is considered that the reactor is a cylinder with its wall made of layers of a refractory and an insulator; this reactor contains a bed of iron ore pellets which is reduced under a flow of reducing gas in the longitudinal direction (along the cylinder). The finite-difference method is used to solve simplified differential equations for description of gas-pellet, gas-refractory and refractory-insulator-environment heat transfer, and heat changes due to reaction inside the reactor. The simulation is fitted by using reducibility tests in a laboratory and runs in a pilot plant. It is found that, because of the nature of the process, it is carried out almost fully in the transitory stage and that is why this simulation is necessary.