Simultaneous desulfurization and denitrification from flue gas by catalytic ozonation combined with NH3/(NH4)2S2O8 absorption: Mechanisms and recovery of compound fertilizer

Abstract

An integrated method of simultaneous desulfurization and denitrification from flue gas by catalytic ozonation combined with NH3/(NH4)2S2O8 absorption was developed for the first time. It consisted of two parts: (1) the catalytic ozonation of NO over FeOx/SAPO-34 to study the effects of the various influencing factors, and (2) the absorption–oxidation of NOx and SO2 induced by ozone combined with a NH3/(NH4)2S2O8 solution in a bubble column reactor. In Part 1, results showed that under the optimal condition of a molar ratio of 0.5 for O3/NO, a residence time of 3 s, a water vapor volume fraction of 4%, a NO initial concentration of 536 mg/m3, and a SO2 initial concentration of 343 mg/m3, the oxidation rate of NO was 55%. The characterizations of poisoned catalyst are briefly discussed. In Part 2, as the gas passed sequentially through the ozonizing reactor and the absorber (NH3/(NH4)2S2O8 solution of 0.8% ammonia and 0.2 mol/L (NH4)2S2O8), a NO conversion rate of approximately 92.6% and SO2 conversion rate of 100% were obtained. The pH of the NH3/(NH4)2S2O8 solution had a significant impact on the NO conversion. According to the analysis of the composition of products under different pHs, a mechanism of desulfurization and denitrification based on NH3/(NH4)2S2O8 solutions was proposed. The reaction product as a compound fertilizer contained up to 24.5% nitrogen.