Reduction Disintegration Behavior of Iron Ore Sinter under High H2 and H2O Conditions

概要

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Reduction of CO2 emissions is an important object for the iron and steel industry. One feasible method may be the utilization of H2 gas as a reducing agent in the blast furnace (BF). However, for stable BF operation, it is first necessary to understand the effects of high H2, and therefore high H2O, concentrations in the reducing gas on the disintegration behavior of iron ore sinter, because it significantly affects the gas permeability of the upper part of the BF. In the present study, disintegration behavior of a sinter sample at 773 K for 3.6 ks under gas flow of N2–CO–CO2–H2–H2O system was examined. The results showed a remarkable increase in the reduction degree and reduction-disintegration index (RDI) upon the addition of a small amount of H2. However, further increase in the H2 concentration caused these values to decrease gradually. Reduction by CO gas led to the formation of magnetite phases with not only thick and long but also fine cracks near the surface. In contrast, H2 reduction did not lead to formation of a significant number of fine cracks. Image analysis of samples revealed that the crack length density showed the similar trend to RDI value. CO gas reduction mainly proceeds near the surface of sinter particles, while H2 gas reduction tends to proceed inside the particles. Accordingly, reduction of H2 gas gave lower RDI than CO gas to the sinter with same reduction degree.