The reduction of hematite to wustite in a laboratory fluidized bed.

Particles (approximately 180 to 250 Μm across) were reduced by CO-CO, by H-HO, and by CO-CO-H-HO in a small fluidized bed, with facilities for automatic sampling of off-gas. Structural changes in the preheating period and during reduction were followed by surface area measurements and by microscopy. During reduction, surface areas increased initially and then decreased, as porosity created by chemical reaction was reduced by sintering; 'uniform internal reduction' was observed from magnetite to wustite. Although the bed was operated under vigorously bubbling conditions, with flow rates 7 to 15 times the minimum fluidization velocity at temperature, gas utilization was high for abstraction of about two-thirds of the maximum amount of oxygen removable by the inlet gas. The utilization fell sufficiently in the remaining stages of the reaction for approximate rate constants to be estimated. The rate increased (a) with increasing temperature, (b) with increasing gas flow, (c) with increasing reducing potential of the inlet gas, and (d) with increasing hydrogen content of inlet gas. The off-gas analyses showed the importance of the water gas shift reaction within the pores of the fluidized particles. [ABSTRACT FROM AUTHOR]