Study On Nitrogen Fixation Into Water By The Technique Of Pulsed High-voltage Discharge Plasma And The Mechanism

Inactive molecules could be dissociated or excited into reactive species by pulsed high-voltage discharge. Nitrogen was directly fixed into water in the form of nitric acid by the technique of pulsed high voltage discharge. Some important factors were investigated concerning the nitrogen fixation efficiency, and the process of nitrogen dissociation in the discharge process and finally fixation into water was analyzed. The fixation kinetics was also preliminarily studied. The main results are as follows:1) Nitrogen could take part in plasma chemical process induced by the discharge, and be fixed into water. Nitrous acid was generated, and was converted to nitric acid. With the formation of nitrous acid and nitric acid, pH decreased, which was advantageous for the conversion of nitrous acid. The final product was mainly nitric acid.2) The fixation efficiency was increased with the increase of applied high-voltage and frequency, the energy efficiency decreased when the voltage increased to some specific value. The fixation efficiency was improved when the mesh size of ground electrode was decreased for the generation of gas-phase discharge. When gas flow-rate varied from 80 to 140 L/h, the production increased with the decrease of gas flow-rate. The total production of HNO2 and HNO3 reached a maximum at O2 content of 66.7% in the gas mixture.3) Nitrogen could be dissociated during the discharge. Nitrous acid was preliminarily formed, and then converted to form nitric acid. Thus, nitric acid was the final product if the discharge time was long enough. The active species such as hydrogen peroxide and hydroxyl radical in the liquid phase played important role in the conversion process. When pH was high in the beginning of discharge, hydroxyl radical played main part, and with the formation of nitric acid and decrease of pH, hydrogen peroxide could take part in the conversion process.