Simultaneous Desulfurization and Denitrification by H₂O₂/FeSO₄ Preoxidation Combined with Wet Flue Gas Desulfurization Postabsorption: Experimental Investigation and Process Simulation

This study focused on the development of a novel process of H2O2/FeSO4 preoxidation combined with wet flue gas desulfurization (WFGD) postabsorption for simultaneous desulfurization and denitrification, and recovery of sulfur and nitrogen from flue gas. The results show that when no oxidant is added, the denitrification efficiency by WFGD is only 5.3%, while under the H2O2/FeSO4 preoxidation, the desulfurization and denitrification efficiency can reach 99.9% and 83.6%, respectively. When the liquid/gas ratio reaches 18 L·m–3, the desulfurization efficiency is nearly 100%, and the denitrification efficiency can reach 90.6% due to the increased liquid/gas contact area and improved heat and mass transfer. The absorption process of SO2 and NOx involves both physical and chemical absorption, which is dominated by physical absorption, and the absorption characteristics are multilayer absorption. The desulfurization products CaSO3 and CaSO4, and the denitrification products Ca(NO2)2 and Ca(NO3)2, are absorbed by the CaCO3 slurry. The Aspen Plus process simulation results show that the desulfurization and denitrification efficiencies are 99.5% and 89.6%, respectively, and the concentrations of SO2 and NOx in the flue gas are 21.4 mg·m–3 and 41.5 mg·m–3, respectively, which meet the ultralow emission standards. In addition, the H2O2/NO molar ratio, oxidation temperature, and SO2 concentration have an important effect on the NO conversion, which then affects the denitrification efficiency.