A novel method of pH-buffered NaClO2-NaCl system for NO removal from marine diesel engine.

Marine diesel engines produce a lot of exhaust gas (NO, SO2). Based on the situation that wet scrubbing methods have been already applied to ship desulfurization and seawater is easily accessible around the ships, this paper proposed a novel AOP (advanced oxidation process) of NaClO2 (sodium chlorite) with Cl- (abundant Cl- exist in seawater) to remove NO from the flue gases of marine engines. The buffer capacity of NaAC (sodium acetate), the effect of Cl- concentration, and Cl- promotion mechanism on NO removal were investigated. The result showed that the existence of NaAC in solution could inhibit the rapid decline of the solution pH. The addition of Cl- achieved a remarkable promotion to NO removal at lower NaClO2 concentration, which was due to the fast generation of ClO2 from the promotion decomposition of NaClO2 by Cl- in acidic condition. Then, the thermodynamic and dynamic mechanism of the generation of ClO2 was intensively analyzed. And the mechanism of NO removal was discussed finally.