Selective Reduction of Iron and Phosphorus from Oolitic Ore

Abstract

The possibility of selective solid-phase reduction of iron from oolitic ore has been experimentally confirmed. Solid phase reduction was carried out at temperatures of 850 and 1000°C in a CO atmosphere and in a mixture with solid carbon. Distribution of iron and phosphorus was investigated with a scanning electron microscope. It was found that at a temperature of 1000°C a minimum amount of phosphorus (up to 0.3%) is transformed into the metallic phase upon reduction with carbon monoxide. Upon reduction in a mixture of ore with carbon, the phosphorus content in the metal phase reaches 1.0–1.3% even at a temperature of 850°C. Thermodynamic modeling of the processes occurring during reductive roasting of oolitic ore was carried out depending on temperature (1000–1400 K) and amount of carbon in the system. It is shown that reduction temperature and degree of phosphorus reduction vary depending on the ratio of CO and CO2 in the gas phase. At temperatures below 892°C, phosphorus is not reduced, and all iron is in the metal phase. With an increase in the amount of carbon in the system, phosphorus appears in the metal phase. With an excess of carbon in the system, all phosphorus is in the metal phase at a temperature of 892°С. Thus, with a certain amount of carbon in the system and, correspondingly, with a certain ratio of CO and CO2 in the gas phase, selective reduction of iron is possible without phosphorus reduction even at a temperature of 1100°С. Comparison of experimental results with results of thermodynamic calculation confirms the possibility of selective reduction of iron without phosphorus reduction only by carbon monoxide.