Effects of Adding Iron Ores-based Calcium Ferrites to the Sinter Mix on Sinter Quality and Reduction of CO₂, NO and SO₂

Abstract

Sinter plants account for more than 10, 40 and 70% of the total emission of CO₂, NO and SO₂ in steelworks, respectively. It is necessary to reduce the fuel ratio in the sinter mix to decrease the CO₂ emission from sinter plants, which will harmfully affect on the melt formation and sinter quality consequently. To overcome the loss in the amount of melt, the current study aims to clarify the effect of adding iron ores-based calcium ferrites to the sinter mix on the sinter quality and emission of harmful gases. The addition of calcium ferrites promoted a significant drop in the sintering temperature, while maintaining the porosity level. The presence of calcium ferrites led to the formation of finer pores, modifying the dominant pore size in the sinter from macro to medium/micropores. The amount of SFCA and SFCA-I phases was significantly increased from 9% of the standard sinter to at least 32%. The sinter properties such as reduction degree, RI and RDI were improved in the presence of calcium ferrites by at least 24, 74 and 26%, respectively. Due to the decrease in the sintering temperature, the required fuel ratio is expected to decrease by more than 30%, and consequently the identical reduction ratio was resulted in the emission of CO₂. The presence of calcium ferrites also contributed to the reduction in the emission of NO and SO₂ at least by 38 and 49%, respectively. A low-temperature sintering process could be designed by adding calcium ferrites to the sinter mix.