Influence of artificially induced porosity on strength and reduction behavior of hematite compacts

Abstract

With the objective to gain more fundamental understanding of the influence of pore structure on the low-temperature reduction behavior of iron ore agglomerates, laboratory-scale induration experiments were performed using pure hematite compacts doped with naphthalene as a porosity-generating agent. The pore structure was thus controlled up to 60% porosity and 1.4mm pore diameter, and no mineralogical changes were observed in these ranges after induration. The cold strength of indurated compacts was higher with pores smaller than 0.125mm in diameter, as well as with pores larger than 1 mm. Changes in the cold crushing behavior of indurated compacts are discussed based on matrix length and distribution theory. Reduction tests in CO-CO2-N2 gas at temperatures in the range of 350-800°C revealed high strength after reduction of compacts with fine pores less than 0.125 mm in diameter. Reasons for this high strength were the Isotropic stress distribution within the compacts, as well as lower expansion due to development of a complex reduction front. © 2005 ISIJ.