Enhancing the Performance of DOC and SCR After-Treatment Devices Using Statistical Techniques and Heating Strategies

Exhaust gas emissions from compression ignition engines are the most hazardous contaminants to human beings as well as the atmosphere. This research work contributes to develop a combined technology that targets the reduction in HC, CO, smoke and NOx emissions collectively without any modification in engine fuel or injection strategy. Slight changes in the exhaust after- treatment system will help in meeting the goal of reduced standards. DOC and SCR devices fitted at the exhaust gas pipe reduces CO, HC, smoke, and NOx emissions produced by the CI engine. A combination of aluminum oxide- cerium oxide and iron oxide are used as SCR and DOC catalysts, whose preparation is done by impregnation method and their performance is tested on a SCR+DOC bed. The injection of aqueous urea solution is varied from 200 ml to 600 ml by intervals of 200 ml at different load conditions. Response parameters for various experiments are predicted using response surface methodology. Utilizing this novel combination of catalysts shows a reduction of 2.6% in CO, 2.2% in HC and 73.2% in NOx emissions. To enable the regeneration of catalysts, a heating strategy is implemented. This helps in replenishing the SCR and DOC bed which gets affected by repeated usage for a continuous period of time. The catalyst light-off temperature is reduced which overcomes the difficulty of operation in cold regions. A significant improvement in the after-treatment system is noticed by electrically heating the catalyst with an electrical power of 400 W. CO and HC emissions are reduced by 12.2% and 2.1% respectively.