Effects of Recycling By-Products as Calcium Ferrites Added to the Sinter Mix on Sinter Quality and Emission of CO2, NO, and SO2

Nowadays, environmental-friendly actions are extremely required, especially for the recycling of by-products and least emission of harmful gases such as CO2. To decrease the CO2 emission from sintering plants, it is necessary to reduce the fuel ratio, which will affect the melt formation, and consequently deteriorate the sinter quality. To overcome the reduction in the melt amount, the current study aims to clarify the effect of adding calcium ferrites to the sinter mix on sinter quality and emission of CO2, NO, and SO2. The calcium ferrites were prepared from several by-products generated from different areas of the steelworks. The addition of calcium ferrites promoted a significant drop in the sintering temperature by 75 °C at least while maintaining the porosity level. The presence of calcium ferrites promoted the formation of finer pores by changing the dominant pore size in the sinter from macro to medium/micro-pores. In addition, the amount of SFCA and SFCA-I was significantly improved to 43 pct at least from 9 pct in the standard sinter. The sinter properties such as reduction degree, reducibility (RI), and RDI were improved, especially in the presence of 20 wt pct of by-product A-based calcium ferrite of 24, 78, and 50 pct, respectively. Due to the decrease in the sintering temperature, the required fuel ratio was expected to decrease by more than 35 pct, and consequently, the same reduction ratio applies to the emission of CO2. The presence of calcium ferrites also promoted a reduction in the emission of NO and SO2 by at least 42 and 32 pct, respectively. An environmental-friendly low-temperature sintering process could be designed by recycling the by-products as calcium ferrites and adding them to the sinter mix.