Experimental study on removal performance of SO2 and NOx in marine exhaust gas using seawater/urea peroxide solution and analysis of ions concentration change

The removal of SO2 and NOx emitted by marine diesel engines was still very important for the development of shipping industry. In this study, a novel method based on seawater/urea peroxide composited absorption solution was used to remove NOx and SO2 efficiently and can keep nitrate concentration lower in liquid phase. And the key parameters were investigated, such as removal efficiency, ions concentration, solution composition, reaction temperature and absorbent concentration. The selected reaction temperature and urea peroxide concentration was 60 °C and 5%, and the SO2 and NOx removal efficiency was close to 100% and 80% respectively. Compared with fresh water, the seawater can improve the NOx absorption capacity of urea peroxide solution, so as to meet the emissions regulation requirements. The concentration of NO3− increased with the oxygenation and absorption capacity of the absorbing solution increasing. However, the addition of seawater could make the concentration of NH4+ decrease a little bit. The ions concentration also increased with the reaction time, and when it came to practical application, the reaction time should be strictly controlled. •Urea peroxide (with oxidation and reduction properties) was firstly used in SO2 and NOx removal.•Marine NOx and SO2 removal efficiencies of 80% and 100% were found respectively.•The nitrate and ammonium were still kept at low levels.•Mutual consumption of oxidant and reductant can be avoided effectively.•The appropriate reaction temperature and urea peroxide concentration was 60 °C and 5% respectively.