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Experimental study on hydrogen reduction of industrial fines in fluidized bed

ABSTRACT A novel setup of fluidized bed was developed to study the reduction of iron oxides by pure hydrogen. The setup enabled the introduction of powder directly to pure hydrogen atmosphere at experimental temperature. The arrangement was to minimize the experimental uncertainties due to gas switching. Hematite and magnetite powders were studied in the temperature range of 768-888 K. Reduction rates of the two powders were found to be similar. For both powders, the reduction rates were very high before the O/Fe ratio reached 0.5. Thereafter, the reduction was sluggish. SEM analyses revealed that the later stages of reaction was controlled by diffusion through the product layer on bigger particles, irrespective of the type of oxide powder. The results have indicated that both hematite and magnetite powder could be employed in fluidized bed. The results have also suggested that process optimization is essential regarding the sluggish reaction below 0.5 O/Fe ratio.