Simulation of Mechanical Degradation of Iron Ore Pellets in a Direct Reduction Furnace

The increase in production of steel in electric arc furnaces in recent years influenced directly the world production of direct reduction iron (DRI). Amongst the most widely used technologies for DRI production is the MIDREX (R) process. The behavior of the metallic charge used in these furnaces, mainly made up of iron ore pellets, influences directly their productivity. Fines contained in the feed are typically removed by screening, in order to prevent them from impacting negatively the productivity of the furnace. However, fines still may be generated inside the furnace as a result of the collisions amongst pellets and between them and internals of the furnace as they move downwards from the feed to the discharge of the shaft furnace. Predicting and preventing such mechanical degradation is critical in the furnace operation. The present work deals with the prediction of degradation of iron ore pellets during reduction in a MIDREX furnace. Collision energies involved in the vertical flow of pellets along a MINIMOD (R) MIDREX direct reduction furnace were estimated using the discrete element method. Using this technique along with a model of degradation that considered assumptions based on information from the literature it was possible to estimate the proportion of fines generated inside the reactor, which was consistent with plant practice. Finally, it was predicted that the generation of fines in the reduction zone of the furnace would vary from 3.4 % to 4.6 % as the throughput of the furnace increased in 50 %.