The Heat Transfer And Kinetic Simulation Of Ozone Generation Via Dielectric Barrier Discharge

Ozone features strong oxidizing capabilits etc., so it was used in water treatment and pharmaceuticals industries nearly a century earlier. Morever, its new applications have been found constantly. However, the productivity of commercial ozonizer fed by oxygen is less than lllg/(kW-h) now, which is well below the theoretical value 1226g/(kW-h). More than 90% of the energy consumed by ozone generation will be converted into heat by the theory of ozone generation via DBD (dielectric barrier discharge). If the heat is not removed promptly, it will decompose ozone generated already. Therefore, it is necessary to analyse deeply the heat-transfer process of ozone generation via DBD in order to produce ozone more effectively. In this paper, the temperature field of ozone generation via DBD was studied so as to reveal the temperature distribution and seek the valid method to drop the temperature of gas gap. At the same time, kinetic analysis is conducted to disclose the reaction mechanism of ozone generation. It mainly concludes these contents as follows:Firstly, the heat-transfer model of tube-type and plane-type ozone generator via DBD was built by Flotran CFD module of ansys software. Their temperature distributions and influencing factors of gas-gap temperature were studied. The analyses of tube-type ozone generator show that the circumferential temperature of each part is uniform, but there is a temperature gradient along gas-stream and radial direction. Within certain range, the lower temperature and larger flow of cooling water, lower discharge power, longer valid-discharge length are in favour of dropping the average temperature of gas gap. The analyses of plane-type ozone generator show that the temperature, along X-axis direction (perpendicular to the direction of gas stream), of each part is nearly uniform besides gas gap and high-voltage electrode, but there is a temperature gradient along gas-stream direction. When the cooling water and dielectric layer lie in the same side of gas gap, it is beneficial to dropping the average temperature of gas gap. Adoption of single dielectric layer or wider gas gap is also good to dropping the average temperature of gas gap.Secondly, the detailed element reactions and kinetic parameters of ozone generation were collected. Then kinetic simulation of process of ozone generation is also conducted. The results show that the increase of gas pressure, the decrease of ambient temperature and gas flow would help produce high-concentration ozone within certain range. Through the sensitivity and ROP (rate of production) analyses of process of ozone generation, the main element reactions and components in the course of ozone generation, and the main influencing reactions of main componets were obtained. Through the transient analysis of process of ozone generation, we reached such conclusions:in unsteady-state particles, the life cycle of oxygen atom is longest, but the life cycles of O-,O+,O2+ are very short. The life cycle of O+,O2+ is about 10-8s, and the life cycles of O- and O2* are approximately 10-6s and 10-6s～10-5s respectively.