Comparison of various chemical compounds for the removal of SO2 and NOx with wet scrubbing for marine diesel engines

Abstract

Seawater, NaOH, NaClO, NaClO2, H2O2, and KMnO4 were used as scrubbing liquids to react with SOx and NOx separately in a customized wet scrubber. The absorption of SO2 in the aqueous phase was influenced by three factors: pH, ionic concentration, and oxidation potential. For NOx removal, the effectiveness of various chemical compounds can be ranked from least to most effective as follows: seawater, NaOH, H2O2 < NaClO < KMnO4 < NaClO2. This effectiveness was influenced by the chemical compound’s ability to oxidize NO to NO2, absorb the NO2 that was formed, and retaining the nitrogen in the aqueous phase. High oxidation potential promoted the oxidation of NO to NO2 but hindered the absorption of NO2. NaClO2 was superior compared to NaClO in all three categories of oxidizing, absorption and retention. NaClO could not retain a significant amount of NO2 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. KMnO4 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.

A Novel Method Based on Hydrodynamic Cavitation for Improving Nitric Oxide Removal Performance of NaClO2

“…When the initial pH was 2.00, 2.50, 3.00, and 3.50, the maximum NO 2 concentration was 205 ppmv, 182 ppmv, 195 ppmv, and 135 ppmv, respectively. Chin et al [ 65 ] and Brogren et al [ 66 ] explained that 60−80% of the NO 2 generated in the reaction can be removed by Equations (18)–(22).…”

Follow-up Research on Simultaneous Removal of NO and SO2 by Wet Scrubbing NaClO Solution Combined In Situ with Ozone Oxidation: Performance and Mechanism

“…Previous studies showed that oxidation potential of NaClO solution increased with solution pH decreasing from 11 to 6. As the pH of NaClO solution was maintained at 6 during the scrubbing process, the oxidation potential of NaClO solution was kept at a high level, which was not conducive to the hydrolysis absorption of NO 2 . It was possibly due to the relatively strong oxidation property of NaClO.…”

“…As the aqueous solubility of NO 2 was much higher than that of NO, part of NO 2 would be absorbed and generate NO 2 – , which could be oxidized to NO 3 – rapidly during the wet scrubbing process. However, due to the high flue gas flow rate and temperature, especially the scrubbing solution pH was kept at 6 and high oxidation of HClO was not conducive to the absorption of NO 2 , parts concentration of NO 2 may be released and caused NO oxidation rate higher than NO x removal efficiency.…”

Kinetics of Nitric Oxide Absorption from Flue Gas Using an Advanced Oxidation Process with Sodium Persulfate Solution

“…Therefore, NO needs to be oxidized first before wet removal. Oxidizing NO to make it soluble in water, various oxidants − have been investigated for their effectiveness in NO x removal. Among these oxidants, Na 2 S 2 O 8 has been widely used in the removal of organic toxic gases, treatment of organic contaminants in groundwater, and remediation of diesel-contaminated soil − for its high stability, low cost, environmental friendliness, and good oxidation properties.…”