Hydrogen-induced Fluidized Bed Reduction : Evaluation of the Effect of Pressure, Particle Size, Gas Mixture and Temperature on the Minimum Fluidization Velocity of Iron Ore Fines

Abstract: Steel is used worldwide and there are demands for an increase in current production. The problem emerges because steel and iron-making industries release vast amounts of CO2 and need to be more environmentally sustainable. Therefore, hydrogen-induced fluidized beds are an interesting alternative to blast furnaces for reduction due to their low, if not non-existent, CO2 release. There are, however, some aspects regarding fluidization that need to be further researched to make fluidized beds an economically and environmentally viable alternative. This study aimed to investigate how certain properties affect the fluidization process, including particle size of the iron ore fines, gas mixtures, temperature and pressure. The minimum fluidization velocity is investigated using two modelling approaches, by Ergun and Wen & Yu. It is found that when the commonly found values for sphericity and voidage were applied to the modelling by Ergun, it did not match the cold experiments of iron ore fines by Reifferscheid. A higher value for voidage and a lower value in sphericity produced more accurate results, however, only two types of iron ore fines were used and additional experiments need to be conducted to generalise this assumption. It is also found that temperature greatly affects the minimum fluidization velocity while the influence of pressure is less significant. Additionally, the impact of the sticking phenomenon is discussed as it is a major part relating to the reduction of iron ore fines in a fluidized bed. This study concluded that there are several aspects that need to be investigated when optimising the reactors to find the most effective operating conditions.