Marine Diesel Engine SCR System Simulation And Experimental Study

As the nature environment worsen, the standard of international Marine diesel engineemission of NOx becomes more and more strict. SCR technology, as one of the mainmeasures of reducing NOx emissions, has been used worldwide. The properity of the selectedcatalyst and the structure of the catalytic converter are two important factors in the SCRsystem.This paper based on a special type of diesel engine Urea-SCR system to carry out thepreparation of catalysts of V₂O₅-WO₃/TiO₂, and analyzes the activity of those SCR atalysts.Moreover, a simulation model has been analyzed in this paper.This paper selects the honeycomb ceramics as the catalyst carrier, and uses the dippingmethod to make small sample catalyst of V₂O₅-WO₃/TiO₂. Moreover, this paper laysemphasis on the activity of the catalyst in different mass percentage of V₂O₅, WO₃andcalcinations temperatures. Meanwhile, the effects of the reaction temperature、the molar ratioof NH₃and NOx、the concentration of SO2and airspeed are taking into consideration, and theparameters of the standard reaction of SCR have been determined in this part. The resultshows that the catalyst made at the temperature of500°C is more active, and the efficiency isthe highest as the reaction temperature is at330°C. At the same time, the results of theexperiment show that the existence of SO2restrain the activity of catalyst, and conversion rateof NO increases gradually as the ratio of NH₃and NOx goes up. But After the ratio of NH₃and NOx is more than1.1, conversion rate of NO levels off.Then, according to the experimental data and run characteristic of the ship, a3D modelof the SCR system is established. This system is used to simulate airflow performance inreactor, the injection of Urea solution, Mixing effect in the mixer, Chemical reaction of SCR.Analysis the Uniformity of gas flow, distributed of pressure, and exhaust composition inchemical reaction. Through the studies have shown that the main pressure loss at the part ofcatalyst carrier. Without consideration mixture of urea and exhaust, the case of（NH2）2CO/NOx molar ratio at0.475then ratio of NH₃and NOx at0.95, DeNOx and Theescape of NH₃at the best match. When additional mixer, Mixing effect in the mixer haveImproved. At the same time the effect of DeNOx have be improved. Calculated theconversion rate of NOx is84.37%Compared with the actual error is less than6%. Pointed out direction structure and choice of reducing agent quality with SCR system. Provides areference for subsequent experimental studies and simulation analysis.