Comparison of various chemical compounds for the removal of SO2 and NOx with wet scrubbing for marine diesel engines
Terence Chin, Ivan C. K. Tam, Chun‐Yang Yin
Abstract
Abstract Seawater, NaOH, NaClO, NaClO 2 , H 2 O 2 , and KMnO 4 were used as scrubbing liquids to react with SO x and NO x separately in a customized wet scrubber. The absorption of SO 2 in the aqueous phase was influenced by three factors: pH, ionic concentration, and oxidation potential. For NO x removal, the effectiveness of various chemical compounds can be ranked from least to most effective as follows: seawater, NaOH, H 2 O 2 < NaClO < KMnO 4 < NaClO 2 . This effectiveness was influenced by the chemical compound’s ability to oxidize NO to NO 2 , absorb the NO 2 that was formed, and retaining the nitrogen in the aqueous phase. High oxidation potential promoted the oxidation of NO to NO 2 but hindered the absorption of NO 2 . NaClO 2 was superior compared to NaClO in all three categories of oxidizing, absorption and retention. NaClO could not retain a significant amount of NO 2 which it absorbed in the aqueous phase. The pH around 8 provided a good balance between oxidation versus absorption/retention and reactant utilization for the chlorine-based oxidants. KMnO 4 had the lowest reactant consumption rate; only half a mole was consumed for every mole of NO removed, compared to around 2–3 mol of chlorite or 3–5 mol of hypochlorite.