Optimizing the operation of straight-grate iron-ore pellet induration systems using process models

摘要

Mathematical models of straight-grate pelletinduration processes have been developed and carefullyvalidated by a number of workers over the past two decades.However, the subsequent exploitation of these models in processoptimization is less clear, but obviously requires a soundunderstanding of how the key factors control the operation. Inthis article, we show how a thermokinetic model of pelletinduration, validated against operating data from one of the IronOre Company of Canada (IOCC) lines in Canada, can beexploited in process optimization from the perspective of fuelefficiency, production rate, and product quality. Most existingprocesses are restricted in the options available for processoptimization. Here, we review the role of each of the drying (D),preheating (PH), firing (F), after-firing (AF), and cooling (C)phases of the induration process. We then use the indurationprocess model to evaluate whether the first drying zone is bestto use on the up- or downdraft gas-flow stream, and we optimizethe on-gas temperature profile in the hood of the PH, F, and AFzones, to reduce the burner fuel by at least 10 pct over the longterm. Finally, we consider how efficient and flexible the processcould be if some of the structural constraints were removed (i.e.,addressed at the design stage). The analysis suggests it shouldbe possible to reduce the burner fuel lead by 35 pct, easilyincrease production by 5 + pct, and improve pellet quality.