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.