Emission regulations are gradually being tightened recently to prevent further air pollution. Cost-effective and efficient technologies must be developed to process the NOx generated in the combustion of fossil fuels. One of the candidate technologies to process NOx is the denitrification of flue gas by pulsed corona discharge, which has been demonstrated experimentally to show high de-NOx performance. However, the optimization of operation conditions and the appropriate understanding of the de-NOx process still remain to be clarified. Therefore, following our previous study on ammonia injection, we have simulated in the present study the de-NOx process to which hydrocarbons such as ethylene have been added to provide guidelines on its proper operation conditions and its main reaction paths to remove NOx. The simulated results show that the removal efficiency in a case of ethylene addition becomes lower than for ammonia addition, but the de-NOx energy consumption rate becomes lower than for ammonia injection. However, with ethylene injection the production of the pollutant, formaldehyde, limits the allowable amount of injected ethylene. The de-NOx performance is better with propylene than ethylene injection because propylene reacts with the OH radical more than ethylene to oxide NOx. However, formaldehyde is also produced in the case of propylene injection, limiting the allowable amount of injected propylene. The de-NOx performance is also assessed in a case where HNO2 is considered as NxOy.