Influence of gaseous sulfur on CO reduction of wustite added with foreign oxides

Abstract

Dense wustite plates added separately with major gangues in ironmaking were reduced using a thermobalance at 1173∼1 373 K with CO-CO2-COS mixtures to elucidate the cooperative influence of added oxide and gaseous sulfur on the reduction behavior. In the tests without sulfur, the reduction was extremely retarded by the existence of Al2O3 or SiO2 in wustite mostly by the formation of dense iron in porous or dense wustite (B or C type), while it was fairly enhanced by adding CaO with porous iron (A type). The sulfur addition of PCOS/Pco=2.2 ×10-6 ∼ 2.2 × 105 unable to form oxysulfide liquid resulted in less reduction rates relative to those without sulfur. This action of sulfur was added to an influence exerted by Al2O3 or CaO. When sulfur and CaO coexisted without any oxysulfides, fibrous iron morphology (F type) was strongly realized. At 1 373 K the iron morphology became coarser for pure or MgO-doped wustite by adding COS. Regardless of gangues the reduction rates rised with higher temperatures. For the reduction tests of same samples using sulfur-bearing gas, porous iron (A type) was preferred previously in H2, while the present CO reduction conducted mostly dense iron (C type). This is probably because the former gas has a larger oxygen removal force from sulfur-adsorbed wustite surface than the latter one. These reduction behavior is discussed focusing a few actions caused by gaseous sulfur.