Amenability of Reduced Iron Ore Pellets to Mechanical Degradation

Abstract

The mechanical properties of iron ore pellets are of central importance to guarantee good productivity in direct reduction plants. Besides the generation of fines during handling, mechanical degradation resulting from forces produced inside the furnace are detrimental to the performance of these reactors, since they can lead to the generation of clusters, and also because they impact negatively the permeability of the charge to the flow of reducing gases. The present work analyzed the effect of different degrees of reduction on the mechanical properties of direct reduction iron ore pellets so as to estimate the proportion of fines generated inside a direct reduction furnace. As such, tests have been performed with unreduced, as well as iron ore pellets that were subjected to different degrees of reduction, with the aim of analyzing their mechanical properties, including microhardness, cold compression strength, mass loss in drop tests as well as pore size distributions. From these results, a parameter of a model of mass loss due to surface breakage was estimated, which demonstrated their greater amenability to breakage as reduction progressed. A combination of these results to simulations using the Discrete Element Method of a direct reduction furnace made it possible to estimate in 5.7% the percentage of fines generated in the furnace.