Study on removing NO from simulated marine diesel engine exhaust gas using the novel composite system of Ozone-Na2SO3/(NH2)2CO.

• The novel system of ozone-Na 2 SO 3 /(NH 2) 2 CO for marine NO removal was proposed. • The NO x removal efficiency was 97.9% and the nitrate concentration was 21.1 mg/L. • Weak acidic media can efficiently improve NO removal and reduce nitrite residue. • This system can efficiently reduce the (NH 2) 2 CO consumption and nitrite residue. The pollutants from the marine exhaust gas seriously threaten air quality and human health. Wet absorption is one of the most efficient NO x control pathways. The strict emission control regulations require the wet NO x control technology to have high NO x removal efficiency and the nitrate concentration of the absorption solution to be below 60 mg/L. The novel system of ozone-Na 2 SO 3 /(NH 2) 2 CO could not only make the NO x absorption efficiency and the amount of nitrate residue fully meet the regulations but also effectively reduce the (NH 2) 2 CO consumption and the nitrite concentration. The final product of NO was mainly N 2 instead of nitrate. The effects of O 3 concentration, Na 2 SO 3 concentration, (NH 2) 2 CO concentration, O 2 concentration, SO 2 concentration, initial pH value, and temperature were thoroughly investigated. The experimental results showed that the NO x removal efficiency was mostly influenced by the O 3 concentration, Na 2 SO 3 concentration, and the initial pH value. Moreover, the nitrate concentration was mainly controlled by Na 2 SO 3 concentration and initial pH value. While the nitrite concentration was governed by the (NH 2) 2 CO concentration and initial pH value. The increase of O 3 concentration and Na 2 SO 3 concentration promote NO x absorption. Although the decrease of initial pH value resulted in a slight increase of nitrate, it greatly reduced the content of nitrite. Furthermore, the increase of Na 2 SO 3 concentration helped to improve the NO x removal efficiency and inhibited the generation of nitrate. Initial pH value was the critical parameter for the NO absorption process. Ozone-Na 2 SO 3 /(NH 2) 2 CO composite system showed great application potential in the field of marine wet NO x control technology. [ABSTRACT FROM AUTHOR]