The problem of environmental pollution by the combustion of fossil fuels in diesel engines, to which NOx emission is a dominant culprit, has accelerated global environmental pollution and global and local health problems such as lung disease, cancer, and acid rain. Among various De-NOx technologies, SCR (Selective Catalytic Reduction) systems are known to be the most effective technology for actively responding to environmental regulations set by the IMO (International Maritime Organization) in marine diesel applications. The ammonia mixes with the exhaust gas and reacts with the NOx molecules on the catalyst surface to form harmless N2 and H2O. However, since the denitrification efficiency of NOx can be rapidly changed depending on the operating temperature from 250 °C to 350 °C at 0.1% sur contents of the catalyst used in the SCR, a device capable of controlling the exhaust gas temperature is essential for the normal operation of the catalyst. In addition, when the catalyst is exposed to SOx in a low exhaust gas temperature environment, the catalyst is unable to reduce the oxidation reaction of the catalyst, thereby remarkably lowering the De-NOx efficiency. However, if the exhaust gas temperature is set to a high temperature of 360–410 °C, the poisoned catalyst can be regenerated through a reduction process, so that a burner capable of producing a high temperature condition is essential. In this study, a plasma burner system was applied to control the exhaust gas temperature, improving the De-NOx efficiency from the engine and regenerating catalysts from PM (Particulate Matter), SOOT and ABS (ammonia bisulfate), i.e., catalyst poisoning. Through the burner system, the optimum De-NOx performance was experimentally investigated by controlling the temperature to the operating region of the catalyst, and it was shown that the regeneration efficiency in each high temperature (360/410 °C) environment was about 95% or more as compared with the initial performance. From the results of this study, it can be concluded that this technology can positively contribute to the enhancement of catalyst durability and De-NOx performance.

The most effective de-NOx technology in marine diesel applications is the urea-based selective catalytic reduction (SCR) system. The urea-SCR system works by injecting a urea solution into exhaust gas and converting this to NH3 and CO2. The injection, mixing, and NH3 conversion reaction behavior of the urea-water solution all have a decisive effect on the performance of the system. To improve de-NOx efficiency, it is important to provide enough time and distance for NH3 conversion and uniform distribution prior to the solution entering the catalyst. In this study, therefore, the characteristics of gas flow, NH3 conversion, and its distribution are investigated with a static mixer by means of numerical methods, providing a special advantage to ship manufacturing companies through the optimization of the urea-SCR system. The results show that the inclusion of the mixer induces strong turbulence and promotes the NH3 conversion reaction across a wider region compared to the case without the mixer. The mean temperature is 10 °C lower due to the activated endothermic urea-NH3 conversion reaction and the NH3 concentration is 80 PPM higher at 1D than those without the mixer. Moreover, the uniformity of NH3 distribution improved by 25% with the mixer, meaning that the de-NOx reaction can take place across all aspects of the catalyst thus maximizing performance. In other words, ship manufacturing companies have degrees of freedom in designing post-processing solutions for emissions by minimizing the use of the reduction agent or the size of the SCR system.

The captured particulate matter (PM) in diesel particulate filters (DPF) must be periodically burned to maintain the performance and durability of the engine. The amount of PM in the filter must be monitored to determine a suitable regeneration period. In this study, the modeling parameters of the DPF were optimized using experimental data to determine a suitable regeneration period for the DPF for marine diesel engines. The differential pressure over the exhaust gas mass flow rate and temperature were measured using a fresh DPF. The modeling parameters of Darcy’s law were optimized using the experimental data. Finally, the model parameters were validated using differential pressure data obtained from a DPF containing PM. The proposed model, which is a function of the gas flow rate, temperature, and amount of collected PM, was developed to simulate the differential pressure of DPFs and shows potential for application in the development of regeneration logic for marine DPFs.