Iron carbide formation with CO gas and CO-H{sub}2 gas mixture under low sulfur potential using the two-step process of metallization and carbidization

摘要

Iron carbide is a good alternative of iron resource, but it tends to be decomposed into iron and carbon. In the previous works, iron oxide was reduced and converted to carbide in one step. The authors showed that carbon deposition was suppressedby adding slight sulfur to the reaction gas, and that the reduced iron was carbidized completely. At the temperature lower than 930K or with CO and a small amount of H{sub}2 gas mixture, the sulfur potential in gas had to be high enough to form sulfide.However, the sulfur content of product was relatively high.Thus, two-step process was introduced in this work; Iron ore was reduced to metal and it adsorbed sulfur at 873K and 973K with hydrogen gas mixture containing smaller amount of H{sub}2S than sulfide is formed. Then, it was carbidized with CO gas or 10vol% H{sub}2 H{sub}2S-CO gas mixture at the same temperature. Sulfur was saturated on the pore surface of reduced iron in the reduction step. It stabilized carbide and prevented carbon deposition with carbidization gas mixtures containing little amount ofsulfur. The conversion to carbide reached about 80% before 8ks. The sulfur content of product was less than 0.05mass%, which is low enough for steelmaking. The catastrophic carbon deposition and pulverization of iron ore, i.e. 'metal dusting', happened in H{sub}2 CO gas mixture after l6ks, although carbon deposition would be controlled up to the complete conversion to carbide.Using the two-step process, the authors will measure the rate of carbide formation by a thrmobalance without the disturbance of reduction and carbon deposition.