Yafang Zhang

The Effect of Inert Gases on Ozone Generation Using Dielectric Barrier Discharge in Dry Air

This experiment studies the effect of inert gases He, Ar, Kr and Xe on ozone generation within a dielectric barrier discharge reactor fed by dry air. The results show that increasing inert gas content leads to a lower applied voltage, discharge power and reduced field. Although the addition of inert gas would lead to a lower reduced field, however, the electron energy distribution function still shifts to the right. The electron density increases slightly at first and then decreases steadily with increasing Xe content, but it decreases monotonically with increasing content of He, Ar and Kr. With regard to dry air/Kr and air/Xe mixtures, ozone concentration and ozone yield show a slight initial increase, followed by a steady decrease for and , which are favorable for ozone production through the Penning dissociation of O2 due to their lower excitation energy.

Energy Conversion and Temperature Dependence in Ozone Generator Using Pulsed Discharge in Oxygen

ABSTRACT A detailed reaction kinetic model consisting of 10 species and 63 reactions is developed to investigate the energy conversion and temperature dependence in an ozone generator using oxygen pulsed discharge. The energy conversion ratios of total electric energy converted into reaction heat, heat carried by gas and heat loss to ambient, namely ηreaction, ηgas and ηloss, are obtained for the first time. The ratio of reaction heat ηreaction decreases substantially with increasing specific energy and inlet gas temperature, which represents how much energy is utilized effectively to synthesize ozone. Correspondingly, ηloss and ηgas increase gradually. ηreaction declines from 55.4% to 27.7% at inlet gas temperature of 298 K when specific energy changes from 0.06 J/cm3 to 0.78 J/cm3. The detailed reaction pathway including the degree of transformation among species for ozone formation is also obtained via kinetics simulation. Meanwhile, sensitivity analysis and rate-of-production analysis for the four most important species O3, O, O(1D) and O2(b1∑) obtained from the reaction pathway are executed to understand quantitatively the temperature dependence of sensitivity coefficient and production rate for each individual reaction. The production rate of ozone via the most important ozone generation reaction O+O2+O2 = > O3+O2 increases linearly with the increase of gas temperature, as well as the destruction rates of ozone via the most important ozone decomposition reactions O3+O3 = > O2+O2+O2 and O3 + O = > O2(b1∑)+O2.

The Effect of SF6 on Ozone Generation using Dielectric Barrier Discharge

This paper reports the results of an experimental study of effect of SF6 on ozone generation within a Dielectric Barrier Discharge (DBD) fed by both pure oxygen and dry air. The chemical reaction mechanisms relevant to the process of ozone generation (and destruction) are discussed. The experimental results show the oxygen source should avoid the presence of SF6 but the addition of a small amount of SF6 in an air discharge can improve ozone concentration and ozone produce efficiency.

Experimental Study on Ozone Generation and Ozone Oxidation to Removal Multi-Pollutant of Flue Gas

Experiments were carried out to study the effects of peak voltage and gap width on ozone generated by proper high frequency and high voltage power supply. The results show that the corona inception voltage are 4100 V, 6500 V and 8040 V when the gap width are 1 mm, 2 mm and 3mm, respectively. The highest volume fraction and production efficiency of ozone are 24.55×10-3 and 134 g/kWh with a gap width of 1 mm. The volume fraction of ozone generated is twice than an ozone generator (famous brand in China), while the production efficiency is equal to it. The simultaneous removal of NOx/SO2 by O3 oxidation was investigated by experiment. In the assistance of wet scrubber, the SO2 removal efficiency is nearly 100% and the NOx reduction efficiency is 86.27% at [O3]/[NO]=0.9.

The Influence of Inert Gas Addition on Electric Breakdown Utilizing Dielectric Barrier Discharge in Ozone Generation in Air

This article investigates the effect of inert gas addition He, Ar, Kr, and Xe on gas breakdown voltage within a dielectric barrier discharge reactor with air feed gas. The density-normalized effective ionization coefficients are calculated for inert gas/air mixtures; the critical reduced field is then obtained where the electron ionization exactly balances the attachment. Adding inert gases would lead to the decreasing critical reduced field strength due to the enhancement of effective ionization coefficient. In addition, inert gas additions have shown to reduce the breakdown voltage. Moreover the calculated breakdown voltage values and the experimental data are plotted for the sake of comparison and results show that calculated results are in agreement with the experimental values. Parametric studies offer substantial insight in plasma physics, as well as in ozone generation applications.

Energy conversion and temperature dependence in ozone generator fed by synthetic air

ABSTRACT A homogenous chemical kinetic model consisting of 21 species and 118 reactions is applied to investigate energy conversion and its temperature dependence in ozone generator fed by synthetic air. The portion of electric energy converted into reaction heat, gas heating and heat loss to surroundings (by convection) in terms of the total electric energy input, the conversion ratios ηreaction, ηgas, and ηloss, are obtained. The detailed reaction pathway including the degree of transformation among species for ozone production is also obtained via simulation of the reaction kinetics. In addition, sensitivity analysis and rate-of-production analysis for the three foremost species O3, O, and N2(A) are performed to understand quantitatively the temperature dependence of sensitivity coefficient and production rate for each individual reaction. ηreaction shows a steep rise at low specific energy, but then suffers a gradual decrease at high specific energy. ηloss has a contrary behavior. And ηgas increases steadily with the increase of specific energy. The ηreaction peak of 35.1% is achieved at specific energy of 0.17 J/cm3 at the conditions under investigation. Additionally, inlet gas temperature only has a small effect on energy conversion. Moreover, high gas temperature in discharge gap is confirmed to be not favorable for ozone formation from the view of reaction heat. The sensitivity coefficients of reactions with electron participation are sensitive to gas temperature. O+O2+O2→O2+O3 and O+O2+N2→N2+O3 account for about 70% and 30% of generated ozone respectively at the given conditions. And e+O2→e+O+O, N2(A)+O2→N2O+O, and N2(A)+O2→O+O+N2 are responsible for about 51.3%, 14.7%, and 32.0% of oxygen atom, respectively.

Optimal Design for Simultaneous Desulfurization and Denitrification by Ozone Oxidation Integrating with Chemical Scrubber

In order to obtain minimum NOx and SO 2 emissions, extra investment and operating costs needs to be supplied. The cost of the ozone oxidation integrating with chemical scrubber (OO&CS) also increases nonlinearly as emissions decrease. This poses a challenging multiobjective optimization problem where emissions like NOx and SO 2 need to be minimized, while minimizing the system cost. A multi-pollutant oxidation by ozone model and an OO&CS process model incorporating in a multiobjective problem is employed to optimize the OO&CS process. It offers multiple Pareto optimal designs that cover the whole Pareto set in an efficient and uniform way and presents abundant insight information approximately the multiobjective problem. These designs capture the nonlinear nature of the OO&CS process, which can eliminate bad designs and promote designs that have lower emissions and lower cost. The optimal process is a valuable tool for design engineers for redesigning the best available design system to make it cost efficient while keeping its advantage of very low level of all pollutant emissions.