An Experimental Study To Reduce NO_x Of Marine Diesel Engine By SCR

With the development of the ship transportation, the requirement of the marinediesel engine nitrogen oxide emission is more stringent. The selective catalyticreduction （SCR） which has high removal efficiency is the key technology to controlthe emissions of the marine diesel engine nitrogen oxides in the future. Based on theoriginal research, this article investagated the marine SCR technology combinedwith NO Catalytic Oxidation to control the emissions of marine diesel enginenitrogen oxides.Pt-based catalysts supported on various supports such as γ-Al₂O₃, TiO₂, ZrO₂,CeO₂and Ce_0.4Zr_0.6O₂have been examined, The investigation indicates thatPt/γ-Al₂O₃catalyst is found to be the most active one among all the catalystsselected.The optimal Pt loading over Pt/γ-Al₂O₃was1%,1wt%Pt/-Al₂O₃catalystwas used as the NO oxidation catalyst in the paper. The influence of reactiontemperature, space velocity, O₂content, SO₂and NO concentration reactionconditions on the catalytic activity was investigated, and to determine the optimumoperating conditions.The catalyst of V₂O₅/TiO₂was prepared based on the original research andtested the impact on the activity of the catalyst loading various concentration ofV₂O₅. The result shows the SCR activity of the catalyst and SO₂oxidation wereincreasing along with the loading of V₂O₅in the range of0.5-5.0%. The catalystloading of4wt%V₂O₅maintained the better SCR activity and anti-sulfurperformance with less than1%SO₂conversion during180-300℃. So the optimalloading of V₂O₅was4wt%. The most appropriate operating conditions of the marineSCR catalyst were determined by testing the effects of different conditions on V-Ticatalyst,such as ammonia ratio, the O₂content, space velocity and temperature, etc.Based on the selected NO catalytic oxidation catalyst and marine SCR catalyst,the combination effect of the NO catalytic oxidation and marine SCR technologywas investigated under the condition of different concentration of nitrogen oxidesand oxygen. The selected nitrogen oxide concentrations were400mg/m³,950mg/m³and1350mg/m³. The oxygen concentrations were10%,13%and16%. The resultshowed that the effect of combination technology is superior to single SCRtechnology.The honeycomb marine SCR catalyst was prepared to test its sulfur resistance.The catalyst remained stable efficiency of more than95%in a month under the conditions of3000mg/m³of SO₂. SO₂conversion was also controlled under1%stably, which showed that the catalyst has a good sulfur resistance and was suitablefor the practical engineering application.