Promotional mechanism of enhanced denitration activity with Cu modification in a Ce/TiO2–ZrO2 catalyst for a low temperature NH3-SCR system

Probable surface NH3-SCR reaction mechanism over CuCe/TiO2-ZrO2 catalyst is proposed to follow the E–R mechanism and the L–H mechanism, while the E–R mechanism dominates in the reaction and the oxidation of NO closes the catalytic cycle.

Techno-Economic Evaluation of Co-Removal of NOx and SOx Species from Flue Gases via Enhanced Oxidation of NO by ClO2—Case Studies of Implementation at a Pulp and Paper Mill, Waste-to-Heat Plant and a Cruise Ship

Co-absorption of NO2 and SO2 from flue gases, in combination with the enhanced oxidation of NO by ClO2(g), is studied for three different flue gas sources: a medium sized waste-to-heat plant; the kraft recovery boiler of a pulp and paper mill; and a cruise ship. Process modeling results are used to present the technical potential for each site together with cost estimation and optimization using a bottom-up approach. A process set-up is proposed for each site together with equipment sizing and resulting flows of process fluids. The simulation results, supported by experimental results, show that removal rates equal to or greater than current best available technologies are achievable with more than 90% of NOx and 99% of SO2 removed from the flue gas. The resulting cost of removing both NOx and SO2 from the flue gases is 2100 €/ton for the waste-to-heat plant, 800 €/ton for the cruise ship and 3900 €/ton for the recovery boiler. The cost estimation show that the consumption and cost of chemical additives will play a decisive role in the economic feasibility of the investigated concept, between 50% and 90% of the total cost per ton acid gas removed.

EFFECT OF MOISTURE ON NITROGEN DIOXIDE FORMATION IN LAMINAR FLAME OF NATURAL GAS

The paper contains the results of experimental studies of the effect of moisture on nitrogen dioxide formation and on oxidation of NO to NO2 in laminar premixed flame of natural gas. The water vapor is shown to be the third very influential participant, along with fuel and oxidizer, in the combustion process. Injection of moisture into the combustion zone has an effect due to the insertion of additional quantities of HO2- and OH– radicals into the process, which contributes to the intensification of the oxidation of NO to NO2. Introduction of the concept of the “excess moisture ratio” in the combustion process is proposed. The studies were executed at the laboratory installation in conditions of formation of the V-shaped laminar flame of natural gas behind a transverse cylindrical steel stabilizer, with determining the concentrations of flue gas components.

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

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.