Iron ore reduction in a continuously operated multistage lab-scale fluidized bed reactor-mathematical modeling and experimental results

Industrial-scale fluidized bed processes for iron ore reduction (e.g., FIOR and FINMET) are operated by continuous feeding of ore, while laboratory tests are mostly performed under batchwise operation. The reduction behavior under continuous operation is influenced by both the residence time of the iron ore particles and the reduction kinetics, which is obtained by batch tests. In a mathematical model for such a process, the effect of both phenomena has to be considered. The residence time distribution of iron ore particles in a laboratory fluidized bed reactor was obtained by measuring the response of a step input and described by mathematical models similar to a continuously stirred tank reactor. In the same reactor, reduction tests with continuous feeding of iron ore were performed. Based on batch tests in a fluidized bed reactor, a mathematical model was developed to describe the kinetics of iron ore reduction under fluidized bed conditions. This kinetic model was combined with the fluidized bed reactor model to describe continuous iron ore reduction. In this detailed model, the change of gas composition while rising in the fluidized bed was considered. The degree of reduction and the gas conversion for reactors in series were calculated. The results obtained by the mathematical model were compared with experimental data from the laboratory-scale reactor.