| The reduction behavior of iron ore fines of multi-sized distribution in a fluidized bed has been extensively investigated in the aspects of degradation and elutriation. The present study has endeavored to obtain fundamental data for effective plant operations and improvements of devices in fluidized-bed systems through fully understanding the effects of operating parameters and dimension or design of reactor on the degradation and elutriation of ore fines during the fluidized-bed reduction. In the fluidizedbed reduction of iron ore fines of multi-sized distribution, the minimum fluidization velocity for fine ore particles smaller than 1500㎛, of which fluidization behavior is governed by the viscosity of gas, decreases with a increase in temperature while that for coarse ore particles larger than 1500㎛, of which fluidization behavior is governed by the force of inertia, increases with temperature. The minimum fluidization velocity equation proposed by Wen and Yu shows most reliable prediction in this study. The abrasion and degradation during fluidized-bed reduction are more severe when the ore particles are coarse, and in this study, the weight pct of ore particles smaller than 250㎛ increased from 27wt% to 45wt% and that of ore particles smaller than 500㎛ increased from 42wt% to 57wt% after the fluidized-bed reduction. It has been confirmed with a mathematical model of elutriation loss that as the superficial gas velocity increases, the fluidization of coarse ore becomes more vigorous but the elutriation rate and the concentration of iron ore fines entrained in gas also increase and it finally results in a high elutriation loss. |
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