An experimental NOx treatment in diesel engine combustion exhaust gases by non-thermal plasma and activated carbon filter combinations

An application of non-thermal plasma (NTP) to chemical treatment of nitrogen oxides (NOx) in diesel engine exhaust gases is experimentally investigated. The chemical treatment oxidizes from nitric oxide (NO) to nitrogen dioxide (NO₂) due to the sufficient residual oxygen (O₂), and simultaneously generates nitric acid (HNO₃) gases due to the water vapor contained in the combustion gases. The NTP is effective for the conversion to NO₂ and HNO₃ gases. For the combustion gas treatment, another chemical effect is required to reduce the poisonous NO₂ and HNO₃ gases. Since activated carbon effectively adsorbs NO₂ and HNO₃ gases, a combination of the NTP and the activated carbon can be expected to remove the NOx. Experiments are conducted to evaluate the combined process of the NTP oxidizations and adsorptions. The reactor is a cascaded AC discharge electrode system and an activated carbon filter in the diesel engine exhaust gas flow. The experimental results show that the NOx gases are successfully removed in the chemical treatment. The NOx removal effects of these combined process are discussed.