A novel one-step wet denitration method by hydrodynamic cavitation and chlorine dioxide

Abstract

Ships have brought substantial economic benefits, and meanwhile, they release exhaust gases, including plenty of nitrogen oxides (NOx). Increasingly stringent air pollutant emission standards (e.g., MARPOL) for ships have been established at home and abroad to reduce the pollution of NOx. In this paper, a promising technology for removing NOx from ship exhaust by hydrodynamic cavitation (HC) and chlorine dioxide (ClO2) was proposed. The mechanism of HC promoting denitration was discussed. The various influencing factors of the HC enhancing ClO2 circulation denitration, such as the pressure difference (∆P) between the inlet and outlet of the HC reactor, solution temperature (10.0 – 55.0 ℃), NO initial concentration (500–1000 ppm), gas flow rate (1.0–1.6 L/min), solution pH (3.00 – 11.00), and ClO2 concentration (0.001–0.100 mmol/L) on denitration effect were studied in the experiments, in which the optimal conditions were established. On the basis of the results of HC enhancing ClO2 circulation denitration, HC enhancing ClO2 non-circulation denitration experiments were carried out. The results showed that the NO and NOx removal efficiencies reached 93% and 90%. We also measured the final anions in solutions after denitration by ion chromatography and discussed the reaction pathways.