The influences of power supply on lean NOx removal by plasma-facilitated selective catalytic reduction

Plasma-facilitated selective catalytic reduction(PF-SCR) was considered as a promising method to realize controlling of NO_x in the lean-burn engine exhaust. But the influences of power frequency lack detailed description. Powers with frequency 50 Hz, 800 Hz and 10 kHz were applied respectively to produce plasma in the experiments, and two-stage process consisting of plasma pretreatment of the exhaust before flow over a lean NO_x catalyst was studied. The results showed that 50 Hz power was more efficient on NO_x removal than other two power supplies according to energy density. It may be attributed to that highest voltage was supplied by 50 Hz power in the three powers at the same energy density, which led to more NO and C₂H₄ oxidation after plasma. As a result, NO₂, more active reactant than NO, was produced more by 50 Hz power. The gas components in the exit of plasma reactor were identified by GC-MS and GC, and the transforming routes of nitrogen element and carbon element were also concluded simply.