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

Mathematical models of straight-grate pellet induration processes have been developed and carefully validated by a number of workers over the past two decades. However, the subsequent exploitation of these models in process o ptimization is less clear, but obviously requires a sound understanding of how the key factors control the operation. In this article, we show how a t hermokinetic model of pellet induration, validated against operating data f rom one of the Iron Ore Company of Canada (IOCC) lines in Canada, can be ex ploited in process optimization from the perspective of fuel efficiency, pr oduction rate, and product quality. Most existing processes are restricted in the options available for process optimization. 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 indurati on process model to evaluate whether the first drying zone is best to use o n the up- or downdraft gas-flow stream, and we optimize the on-gas temperat ure profile in the hood of the PH, F and AF zones, to reduce the burner fue l by at least 10 pet over the long term. Finally, we consider how efficient and flexible the process could be if some of the structural constraints we re removed (ie., addressed at the design stage). The analysis suggests it s hould be possible to reduce the burner fuel lead by 35 pet, easily increase production by 5+ pct, and improve pellet quality.