A Multifunctional Converter for Purifying Diesel Exhaust Gas with a Self-Heat Exchange Function

As a continuation of our study of heat-integrated converters, we have fabricated a multifunctional converter that can treat all the components of emissions from diesel vehicles, namely CO, hydrocarbons, nitrogen oxides (NO _x ), and particulate matter (PM). NO _x is reduced over a NH₃-SCR catalyst while PM is removed by a diesel particulate filter. The converter is also equipped with a self-heat exchanger that transfers heat from downstream to upstream of the converter, increasing the converter temperature and thereby substantially improving its performance. In an experiment using a 2.2-L engine vehicle operated at a constant speed of 60 km/h, the NO _x and PM reduction rates respectively reached 98 and 99.97 % due to efficient heating of the exhaust gas from 117 to 320 °C in the converter by the addition of H₂ in the exhaust gas combined with the self-heat exchange function. Under transient driving conditions (Japanese 10–15 mode), the total NO _x reduction rate was 96 %.