Influence of Gaseous Sulfur on Hydrogen Reduction of Wustite Added with Foreign Oxides.

Abstract

Dense wustite plates added separately with major gangues in ironmaking were reduced using a thermobalance at 900°C with H2-H2O-H2S mixtures to elucidate the coexisting influence of each added oxide and gaseous sulfur on the reduction behavior.In the tests without sulfur, the reduction was retarded by the existence of Al2O3 as well as MgO in wustite mostly by the formation of dense iron in porous wustite (B type iron), while it was enhanced by adding CaO or SiO2 with porous iron (A type iron). These results coincided with several earlier works.The tests with as=0.01 as the sulfur activity in gas phase, which was defined relative to Fe/FeS equilibrium, showed that their reduction behavior did not change significantly compared with those without sulfur. However, with increasing as up to 0.10 most of the reduction rates tended to approach a moderate level regardless of adding above oxides, being affected by the reducing potential and the two cases whether traces of oxysulfides are formed in Fe/FeO interface or not. In the former case, coarse iron morphology (AC or FC type iron, C; coarse, F; fibrous) was observed with relatively less reduction rates than the latter, in which fine morphology (A or F type iron) was realized except the case of Al2O3 (B type iron) to eliminate the extreme reduction retardation. Only under the coexistence of sulfur at as=0.10 and CaO, F type morphology was predominated.These reduction behavior is discussed focusing a few actions caused by gaseous sulfur.