Simultaneous Removal of Particulate Matter and NO_<i>x</i> from Diesel Power Generator Exhaust

In the field of diesel engine industries, after-treatment technologies employing catalysts and filters were developed to reduce pollutant emissions. However, these efforts were primarily focused on vehicles and were limited to applications to power plants. The objective of this study was to evaluate the performance of a diesel particulate filter (DPF) coated with a selective catalytic reduction (SCR) catalyst and to apply it to a commercial diesel power generator. An SCR-coated DPF (sDPF) with a porosity of over 50% was loaded with particulate matter (PM), and engine bench tests were conducted to assess the NOx reduction and passive regeneration performance through soot oxidation. Experiments were conducted in the temperature range of 275–350 °C to examine the effects of urea injection and varying NO2/PM ratios at the sDPF inlet. The results indicated that a DPF with 54% porosity and coated with 90 g/L of SCR catalyst demonstrated the highest NOx reduction performance under diesel power plant operating conditions. The minimum required NO2/PM ratio to maintain or reduce the sDPF backpressure, when urea was injected, was determined to be 89.5. Based on the engine bench test results, simulations were performed to derive design data necessary for a 1 MW of diesel oxidation catalyst-sDPF system, which was then installed on a commercial generator and subjected to long-term operation for 1500 h. During the long-term operation, NOx and PM removal efficiencies exceeded 90%, and the system operated at an average backpressure of 16.52 mbar, below the generator’s allowable backpressure of 30 mbar, facilitated by sDPF passive regeneration. Integrating the after-treatment system into commercial diesel power generators required not only improving PM and NOx reduction performance but also maintaining the system’s backpressure during continuous operation. Determining the optimal NO2/PM ratio entering the sDPF was essential to ensure that this balance was achieved.