Simultaneous Control Of Nox And Organic Particles Using Plasma Assisted Catalysis

Water and higher concentrations of oxygen present in diesel and turbine combustion exhausts inhibit and deactivate selective reduction (SCR) catalysts that are effective in removing NOx from internal combustion engine exhausts. Ox idation of NO to NO2, the slow step in SCR treatment, is accomplished rapidly as a competing process during plasma-catalyzed oxidation of hydrocarbon (HO) fuels in exhausts. Reduction of NO2 so formed is effected by passage of the heated stream through a bed of alumina of practically any configuration. Two-stage reactors to perform these steps were assembled and tested at bench-, pilot- and full-scale on exhaust from a 5.9-L Cummins diesel engine. The process, called plasma-assisted catalytic reduction (PACR), removed 95% of NOx at pilot scale using propene as the HO. Diesel fuel was used in the three sets of engine tests, and under these conditions PACR consistently achieved 50-55% reduction of NOx at a net fuel penalty of 5% to operate the control. Fuel sulfur did not affect the PACR process, and SO2 was not oxidized. Conduction across the high-voltage insulator was observed as a problem, but oxidation of deposited soot by the plasma was also observed and the system could be reconfigured using the plasma to prevent soot accumulation. Fuel cracking to enhance NO2 reduction was proposed but not tested.