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Catalytic emission control systems are installed on nearly all automobiles and heavy-duty trucks produced today to reduce exhaust emissions for the vehicles to meet government regulations. Current systems can achieve very high efficiencies in reducing tailpipe emissions once the catalytic components reach their operating temperatures. They are, however, relatively ineffective at temperatures below their operating temperature windows, especially during the cold start period of the vehicles. With the increasingly stringent government regulations, reducing the emissions during the cold start period before the catalytic components reach their operating temperatures is becoming a major challenge. For cold start HC control, HC traps based on zeolites have been investigated and commercialized for certain applications. For cold start NOx control, especially in lean burn engine exhaust, NOx storage and release catalysts have been evaluated.

The European research co-operation Lotus is presented. The main objectives of the project were i) to show the potential for a urea-based SCR system to comply with the EU standard of years 2005 and 2008 for heavy-duty Diesel engines for different driving conditions with optimal fuel consumption, ii) to reach 95 % conversion of NOx at steady state at full load on a Euro III engine, iii) to reach 75 % NOx reduction for exhaust temperatures between 200-300°C, and 85 % average NOx reduction between 200-500°C. The energy content of the consumed urea should not exceed 1.0 %, calculated as specific fuel consumption. These targets were met in May 2003 and the Lotus SCR system fulfilled the Euro V NOx legislative objectives for year 2008.

This paper describes the development and characterization of a selective catalytic reduction (SCR) catalyst system for a typical EUIV heavy-duty diesel (HDD) engine. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated, before examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. Finally, the durability of the SCR catalyst is described. Taken as a whole, the results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment (EA) solution.

This paper describes the development and characterization of a Selective Catalytic Reduction (SCR) catalyst system for EUIV (HDD) engines. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated. The durability of the SCR catalyst is described. Finally, examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. The results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment solution.