Research On SCR Technology Of Marine Diesel Engine NO_x

At present,the problem of environmental pollution is attracting more and more attention,and the international community and relevant organizations have enacted corresponding emission regulations to reduce the harm to human and natural environment caused by major pollutants.In this paper,the effect of selective catalytic reduction(SCR)on NO_x emission from marine diesel engine was studied,and the control effects of different temperature,exhaust air velocity and ammonia nitrogen ratio were compared.Through the research,we found that(1)the NO_x emission limit of third stage equipped with SCR system engine is 3.4g/kWh.In the test,the engine passed the catalytic reduction of the SCR system,and the NO_x emissions met the requirements of the third phase emission regulations.SCR and the conversion efficiency is high,for the future optimization of engine control NO_x emissions meet the strict emission limits for the third stage value provides an effective method;(2)through the comparison of different exhaust temperature,space velocity,ammonia nitrogen oxides than under the SCR system on the emission control effect,found that with the increase of ammonia ratio,the catalytic conversion of NO_x to improve the efficiency;low temperature,the conversion rate of NO_x with the increase of the ratio of ammonia nitrogen reaches a certain value,when the NH3 supply exceeds the critical value,the leakage of NH3 will increase rapidly;the higher the temperature,the initial reaction rate of SCR faster,NH3 and NO after the full reaction time is short,but the high exhaust temperature so,NH3 had oxidation reaction,again to generate NO_x compounds,the catalytic conversion rate which occurs along with the exhaust temperature continued to rise fall.Therefore,with the increase of the exhaust temperature,the conversion rate of NO_x increases first and then decreases.In the case of low speed ratio,the catalytic conversion rate of NO_x is relatively high,and the catalytic conversion rate of NO_x decreases with the increase of the space velocity ratio.When the temperature is low,the catalytic conversion rate of NO_x decreases almost linearly.When the temperature increases to a certain extent,the effect of space velocity on the conversion rate is smaller.(3)in order to improve the performance of SCR system,this paper puts forward some strategies,such as ensuring sufficient amount of catalyst,controlling the emission of diesel soot and controlling the injection of urea.In short,this article on the selective catalytic reduction(SCR)of the control effect of nitrogen oxide emission of marine diesel engine,whether it has guiding significance to our country marine SCR system performance is still after the domestic diesel engine emission control to enhance the effect.