A Preliminary Research On Chemical Kinetics Of Discharge Plasma In Gas-Liquid Mixture

With the development of wastewater treatment technology by discharge plasma, especially the further research of wastewater treatment by discharging in a two-phase mixture(TPM), the inosculation between the theory of discharge physics and chemical kinetics is exigently needed, and the study hierarchy level should be transited from the macroscopical and phenomenological level to the microcosmic molecular level. At present, the research on chemical kinetics for the reaction system formed and maintained by the two-phase mixture discharge appears scarce. Based on an in-depth analysis for the essence characteristic of discharge plasma chemistry, this paper discussed the research content and methods of chemical kinetics for the reaction system formed and maintained by the two-phase mixture discharge, and established a preliminary chemical kinetics model coupling with the discharge theory for a gas-water mixture discharge chemistry system. And the calculation and analysis are implemented at last. The main contents include:Chemical kinetics model for describing the reactions action of active species produced by discharge plasma in bubbled water is developed in this paper for simulating and predicting the evolution of the concentration of each active species produced by a single discharge with the reaction time. The results indicate that as follows:(1) the concentration of H2O2 produced by the initiation reaction is gradually decreased in the subsequent radical reactions, and a high voltage has a more remarkable drop than a low voltage. The concentration comes to zero after 1～1.5ns.(2) the concentration of O2 rises up and comes to a constant after 50～60ns, it is higher in high-voltage than in low-voltage.(3) the variation tendency of the concentration of·OH and HO2·with the time both increase first, then decrease, and finally reduce to zero. The time of the radical·OH to reach maximum concentration is approximately 9 to 13ns, longer than HO2·(2~3ns). The concentration of the two species is higher in high-voltage than in low-voltage, and after reaching the maximum concentration, the concentration will decrease faster in high-voltage, then running to zero basically in the same time. Computation model for the yields of active species produced by discharged plasma in the gas-liquid mixture formed by spraying mist in the gas phase is established in this paper. The evolution of the yields of active species in the circumambient space of a single water droplet's surface with the discharge characteristic parameters of the two-phase mixture is studied. The results indicate that as follows:(1) the yields of active species increase gradually with an increase in the dielectric mismatch of the gas-liquid two-phase mixture, and the extent of their increase with the change of the dielectric mismatch is weakened during the same course.(2) the yields of active species increase gradually with an increase in the volume fraction of liquid droplet, and the extent of their increase with the change of the volume fraction of liquid droplet is enhanced during the same course.(3) the yields of active species in the case of charged liquid droplet are 2～10 more than those in the case of uncharged liquid droplet.