A diesel emission control system, which can simultaneously reduce particulate and NOx emissions through filtration and particle-free Exhaust Gas Recirculation (EGR) has been developed and tested. The key element of the system is a novel ceramic fitter which has shown virtually complete soot removal from diesel exhaust streams. Regeneration of the filter was accomplished by periodically backpulsing the filter with short pulses of compressed air.
Testing of the system was carried out using a Caterpillar generator set powered by a 65 kW diesel engine, and a separate load bank which allowed the engine to operate at various load settings. The filter unit consisted of four CeraMem filters (150 mm2 x 305 mm long, 4 mm2 cell), a backpulsing system for filter regeneration, and a baghouse for soot collection.
NOx reduction of 75% was achieved at full engine load and a 30% EGR rate. The CO emissions, which increased as a result of the EGR, were reduced to their initial values by utilizing a CO oxidation catalyst mounted downstream of the filter unit. The filter, which exhibited a particle collection efficiency > than 99%, proved to be regenerable after repetitive filtration/regeneration cycles.