NOx Treatment by DC Corona Radical Shower with Different Geometric Nozzle Electrodes

Abstract

The nozzle electrode is a very important part in the corona radical shower NOx treatment system. In this study, the influences of different geometric nozzle electrodes on corona discharge characteristics, ozone and NOx formation characteristics, and NO conversion characteristics were investigated. In addition, an experiment that involved the NO conversion characteristics, relative to multinozzle electrodes, was performed. The results show that the different nozzle radii may transform the discharge modes. The increasing nozzle quantity can enlarge the corona region and increase the discharge current, while it almost has no effect on the onset voltage and sparking voltage. The ozone formation during corona discharge is affected by different geometric nozzle electrodes. More ozone is generated with the increasing nozzle radius and nozzle quantity. However, NOx concentrations are not affected much and the NOx concentrations are basically <10 ppm. The NO conversion rate improves with the magnification of the nozzle radius and the increase of nozzle quantity. For the φ3(14) nozzle electrode, the NO conversion rate can reach ∼82% under a NO initial concentration of 69 ppm, treatment gas flow rate of 19.7 L/min, and input power of 4.7 W. The increasing quantity of nozzle electrodes can enhance the maximum NO conversion rate. However, it has no obviously positive effect on energy efficiency. The consistency between the ozone formation and NO conversion indicates that the radicals of O and O3 may have an important role during NO conversion. In this experiment, energy yield basically seems to show a trend of increase, followed by a decrease, with increasing specific energy density. The energy yield clearly is enhanced as the size of the nozzle radius and the nozzle quantity each increase. For the φ3(14) nozzle electrode, when 82% NO conversion is acquired, the energy yield is ∼20 g/kWh. Hence, a high NO conversion rate and energy yield surely can be obtained through optimization of the nozzle radius and nozzle quantity.