Lowering reduction temperature of iron ore and carbon composite by using ores with high combined water content

Abstract

The steel industry is facing two difficult and urgent tasks to reduce CO2 emissions and to use low-grade iron resources effectively. The utilization of an iron ore-carbon composite is one of the promising methods to solve the former. The latter is concerning to goethite ores such as Australian Marra Mamba and pisolite ores, which contain high concentration of combined water. In this study, the effect of combined water on the reduction behavior of the iron ore-coal composites at elevating temperature was examined under inert gas flow. Below 1 200 K, the reduction of iron oxide in Marra Mamba ore-coal and pisolite ore-coal composites proceeded faster than that in hematite ore-coal composite. It can be attributed to the larger specific surface area of the ores after decomposition of the combined water. Metallic iron also formed at lower temperature in the composites containing Marra Mamba and pisolite ores. The generation rate of CO gas from these composites showed the maximum value at approximately 1 170 K; however, that from the hematite-coal composite gave no peak, because formed metallic iron could act as a catalyst for the gasification of carbon. These results indicate that the reduction of ores with high combined water concentration can proceed at lower temperature. Above 1 373 K, however, the reduction rate of these ores in the composite significantly decreased due to a drastic decrease in the specific surface area of the ores and the formation of slag. © 2009 ISIJ.