An experimental study on the kinetics of fluidized bed iron ore reduction

To optimize existing iron ore reduction processes or to develop new ones, i t is necessary to know the reduction kinetics of the iron ore of interest t inder the relevant operating conditions. In this work the reduction kinetic s of hematite fine iron ore was studied for industrial-scale processes usin g the fluidized bed technology. Especially designed batch tests were perfor med in a laboratory-scale fluidized bed reactor fluidized with H-2, H2O, CO , CO2, N-2 at atmospheric and elevated pressures to simulate the relevant p rocess conditions. To obtain the reduction rates and the degree of reductio n, the concentrations of H2O, CO, and CO2 in the outlet gas were analyzed b y FT-IR spectroscopy. Preliminary reduction tests showed a strong effect of the sample weight on the reduction rates, especially in the early stages of reduction. The optim um sample weight was determined by partly replacing the hematite with silic a sand. Additionally the silica sand provided a constant and stable flow pa ttern throughout the reduction tests. The effects of temperature, gas compo sition, particle size and pressure on the rates of reduction were tested an d discussed. Rate analysis showed the existence of two phases with different rates durin g the reduction tests, Additional investigations (microscope analysis, SEM) demonstrated that in the first phase the rates were controlled by mass tra nsport in the gas phase and in the second phase by the reduction process wi thin the small grains of the iron ore particles.