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As nitrogen oxide (NOx) emissions from marine slow speed diesel engines have caused serious health and environmental problems, NOx removal using electro-generated chlorine under seawater electrolysis was studied in a lab-scale scrubbing reactor.

Experiments were conducted to simultaneously remove NO and SO2 from simulated exhaust gas by cyclic scrubbing and online supplementing pH-buffered NaClO2 solutions in a bench-scale reactor. The effects of key operating parameters on pollutant removal performance had been investigated. The results suggested that an extremely high oxidant utilization rate could be obtained when the oxidant supplementing molar rate approached the oxidant consumption molar rate. Though co-existing SO2 in flue gas would consume a certain amount of the oxidant during the absorption process, the intermediate products of SO3 2– ions generated from SO2 hydrolysis might be in favor of NO2 absorption to some extent. The introduction of ethanol in scrubbing solution could enhance NO x removal performance largely, which was possibly because of its inhibition effect on SO3 2– oxidation. The reaction mechanism and reaction products in scrubbing solutions were also discussed roughly through theoretical calculations and ion chromatography analysis.

The mass transfer reaction kinetics of NO absorption by UV/chlorine advanced oxidation process were investigated in a lab-scale photochemical bubble reactor. Effects of several parameters on NO absorption rate were studied, including UV power, NO inlet concentration, SO 2 concentration, active chlorine concentration of electrolyzed seawater, and reaction temperature. Results showed that NO absorption rate increased gradually with the increase of UV power, NO inlet concentration, and active chlorine concentration of electrolyzed seawater, but was almost independent of SO 2 concentration and reaction temperature (below 313 K). The absorption process is a pseudo-0.2-order with respect to NO, as well as a pseudo-0.6order with respect to active chlorine. The mass transfer process is the main rate-determining step for the NO absorption by UV/electrolyzed seawater process. The established NO absorption model is in good agreement with the experimental values.

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