Environmental and economic impact assessment of three sintering flue gas treatment technologies in the iron and steel industry

Increasingly stringent pollutant emission standards pose a new challenge to the control of air pollutants in China's iron and steel industry (ISI). This study quantified and compared the environmental and economic effects of three typical sintering flue gas ultra-low emission treatment technologies in China's ISI, namely, semi-dry flue gas desulfurization + semi-dry flue gas denitration with O3 + bag filter (SSOB), wet flue gas desulfurization + wet electrostatic precipitator + selective catalytic reduction denitration (WWS), and semi-dry flue gas desulfurization + bag filter + selective catalytic reduction denitration (SBS) by conducting a life cycle assessment coupled with life cycle costing method. Using 1 ton of sinter as the functional unit and "cradle to gate" as the system boundary, the environmental impact of the three treatment technologies is 0.1822, 0.1298, and 0.117, respectively and the total economic cost is 11.622, 10.353, and 10.435 RMB, respectively. The ozone oxidation, semi-dry flue gas desulfurization (FGD), and semi-dry flue gas denitration processes are the key processes of SSOB with electricity, liquid oxygen, and sodium sulfite as key substances. Wet flue gas desulfurization process and selective catalytic reduction (SCR) denitration process are the key processes in WWS while electricity is the key substance. Semi-dry FGD and SCR denitration are the key processes in SBS, with electricity and lime as the key substances. SBS has optimal environmental performance, while WWS has lowest economic costs. Optimization suggestions for each technology are presented based on the influence degree of key processes. The research findings will be valuable for the selection and optimization of ultra-low emission technologies of ISI.