Emission Characteristics of a Urea SCR System under the NOx Level of Japanese 2009 Emission Regulation

In order to discuss future technical issues for urea SCR (selective catalytic reduction) system, it is necessary to assess various technical possibilities that would be applied to urea SCR systems which is capable of complying with future emission level requirements, for example Japanese 2009 emission regulation. In this paper, three measures (enhanced insulation on a DOC (diesel oxidation catalyst), aggressive urea solution injection and idling stop) are installed on a urea SCR system of a commercial engine system in order to achieve further NOx (nitrogen oxide) reductions. With combination of these three measures, NOx is drastically reduced to the levels lower than 0.7 g/kWh, which is a NOx limit value of the Japanese 2009 emission regulation. NH₃ (ammonia) and HCN (hydro cyanide) are also measured as unregulated harmful components. Both unregulated components are emitted at very low levels, even though NOx emissions are lower than the Japanese 2005 emission regulation and equivalent to the 2009 regulation level.