Study On NO_x Removal From Marine Diesel Engine Exhaust Gas By Electrolyzed Seawater

The exhaust gas emitted from diesel engine contains a great number of pollutants such as SOx,NOx,PM and so on,leading to the air pollution.The Beihai of Europe,and the Baltic Sea were set as the NOx emission control area at the MEPC 70 meeting.In order to meet the strict requirement,several technologies have been applied to mitigate NOx emissions from marine.diesel engines.These technologies include SCR,EGR,wet scrubbing and so on.However,SCR has some problems,such as high working temperature,easy poisoning and so on.EGR system will reduce the thermal efficiency of diesel engine,increase CO,PM emissions.Wet scrubbing method can simultaneously remove NOx and SOx,as well as particulate matter in the exhaust gas.However,most of the oxidizer needs to be carried along with the ship,which can influence the security of ship operation.Nevertheless,the effective chlorine solution can be prepared by electrolysis of seawater.By sing the strong oxidation of the solution,the NOx can be oxidized to high-nitrogen oxides which are soluble in water.Therefore,this paper presents a method fo r denitrification of the marine diesel engine by seawater electrolysis.The feasibility of the method was studied by electrolytic and denitrification experiment.The effects of different electrolysis conditions on the available chlorine concentration and the pH value of electrolyte were investigated by the electrolysis experiments.The result shows that the available chlorine concentration increases linearly with the increase of electrolysis time,current density and seawater salinity.The pH value of electrolyte decreased first and then increased with the increase of electrolysis time.The lower the current density is,the more obvious the phenomenon is.The pH value of electrolyte increases with the decrease of electrode spacing and seawater salinity.The effects of the available chlorine concentration,pH value of electrolyte,initial concentration of NO and SO2 on denitrification were investgated by the non circulating simulated gas denitrification experiments.The results indicate that the NOx removal rate increases as available chlorine concentration increased,and stabilize at available chlorine concentration of 1000 mg/L.However,the NOx removal rate decreases with the increase of pH value of the electrolyte.With the increasing of the initial concentration of NO,the NOx removal rate increases and stabilizes when the initial concentration of NO is greater than 1000 ppm.The NOx removal rate decreased slightly with the increase of initial concentration of SO2,but the removal rate of SO2 was always up to 100%.The effect of available chlorine concentration on the removal rate of NOx and the duration of the circulating spray time were investigated by the circulating simulated gas denitrification experiments.The results show that with the increase of available chlorine concentration,the removal rate of NOx and the duration of cyclic spraying time increased gradually.In addition the energy consumption analysis on the application of electrolysis seawater to desalination was performed by 5S35ME-B9 diesel engine,the result shows that the electrolytic power consumption accounted for about 8.09percentage of the engine power.