INFLUENCE OF COATING OXIDE AND SULFUR PRESSURE ON STICKING DURING FLUIDIZED-BED REDUCTION OF IRON-ORES

In order to avoid sticking during a fluidized bed reduction of iron ores and elucidate its mechanism, their reduction tests using two types of easily sticked ores coated by a water-slurry consisting of each submicron reagent of gangue species were carried out at 900-degrees-C by N2-H-2 mixtures having sulfur activities incapable of forming FeS, where fibrous irons are known to be predominated from the authors' previous researches. Without coating, ores sticked mostly due to fibrous morphology and/or high surface energy of iron. With coating, ores kept fluidizing mainly due to the physical spacer effect among ore surface. Al2O3, and MgO were effective agents, while CaO was ineffective due to nonuniform coating and preferential upward growth of irons. Particularly, the conditions near a(s)=0.1 in a bed (a(s):sulfur activity in gas phase relative to Fe/FeS equilibrium) increased fairly the coating amount necessary to improve fluidization, because such conditions promote most fibrous irons. It was found that the coating amounts required to improve fluidization increase with fibrous iron morphology, active iron surface, and less original gangue coverage. Coating traces of ore tail rich in Al2O3 and SiO2 species was also effective for fluidization.