Potential for Reducing Emissions by Regulating O₂, CO, and H₂O in the Recirculation Gas in Iron Ore Sintering

The sintering process is undergoing a transformation to meet future challenges, so a more profound understanding of the potential influence of the individual recirculation gas constituents, in particular O2, CO, and H2O, is essential. Within this paper, miniaturized lab-scale sintering experiments are presented using an industrylike raw mixture, to study the effects of variations in the individual O2, CO, and H2O supply on the sintering process and the sinter quality. As the O2 content (up to 30 vol%) in the suction gas increases, both sintering yield and strength increase, resulting in lower return rates, with more or less constant amounts of CO in the off-gas. Productivity and sintering strength increase with increasing CO concentration, while the NO concentration in the off-gas tends to be lower. With increasing H2O content, productivity and sintering strength increase with a significantly lower CO concentration in the off-gas, due to the water-gas shift reaction taking place in the flame front. The results demonstrate the potential of adjusting the raw mixture recipe by selectively modifying the recirculation gas, particularly towards a lower coke breeze content. This would enable reductions in the specific emissions of CO, CO2, SO2, and NO per ton of product sinter.