Simulation of the Transient Thermal Response of a High Pressure Selective Catalytic Reduction Aftertreatment System for a Tier III Two-Stroke Marine Diesel Engine

The IMO tier III legislation, applicable to vessels with a keel laying date from Jan. 1, 2016, has compelled engine builders to apply new technologies for NO_x abatement. One of the most promising technologies for tier III compliance is the selective catalytic reduction (SCR) of nitrogen oxides (NO_x). Despite that SCR technology has been applied in powerplants and heavy duty truck engines for years, there are challenges that stem from its applications in large two-stroke marine diesel engines. In this paper, an SCR model applicable to large two-stroke marine diesel engines is introduced. The goal of the model is to predict the thermal response of a marine SCR aftertreatment system when the engine undergoes transient loading. The model has been developed and validated using testbed measured data from a large two-stroke marine diesel engine. The output of the model is the SCR outlet temperature. It is shown that the model can accurately predict the transient inertial response of the SCR during engine acceleration, deceleration, and low load operation.