Positive and negative corona discharges in flowing carbon dioxide

Abstract

The effect of the gas flow rate (10–320 cm3 min−1) on the process of ozone formation in both positive and negative corona discharges has been studied using a coaxial cylindrical system of electrodes fed by dry CO2. The source of ozone is electron impact dissociation of carbon dioxide to liberate oxygen atoms and their subsequent formation of oxygen molecules, which may then form ozone by the well-known Chapman mechanism. Small increases in flow rate were found to cause a major increase in the discharge current measured in the negative corona discharge. This effect was found to correspond to observed changes in the ozone concentration within the discharge and is a consequence of dissociative electron attachment to ozone leading to negative ion formation in the discharge. In contrast no direct effect of ozone on the positive corona discharge current was observed. The observed increase in average positive ion mobility in the positive corona is ascribed to the conversion of ions into more mobile ions. Considerably higher ozone concentrations (up to 100 ppm) were found in the negative corona discharge. The effect of the geometry of the system was also explored by using three different stainless steel outer electrodes with diameters of 10, 15 and 27 mm. Ozone concentrations were found to decrease significantly with increasing radius of the outer electrode at the same average input energy density.

Influence of the Outer Electrode Material on Ozone Generation in Corona Discharges

“…From the measured data of the ozone decomposition rate constant the probability of ozone decomposition c was calculated by using the formula (6). The data for the clean material and data obtained in last cycles of treatment of wall with oxygen-ozone-mixture are summarised in Table 1 together with data of other authors [10].…”

“…Skalny et al [6] have found in post discharge regime an exponential decrease of ozone concentration in closed cylindrical reactor. This was ascribed to heterogeneous ozone decomposition on the wall of the reactor.…”

“…Therefore, the investigation of technological parameters, influencing the efficiency of ozone generation, is permanent. As it was shown by several authors the electrode material is the one of parameters considerably affecting the process of ozone generation in corona discharges [1][2][3][4][5][6][7][8][9]. The interaction of ozone molecules with the outer electrode or inner electrode in coaxial corona discharge reactor results in ozone destruction and surface oxidation phenomena.…”

Elemental mercury oxidation in an electrostatic precipitator enhanced with in situ soft X-ray irradiation

“…However, when soft X-rays were added, a current of 41.5 μA and an Hg 0 conversion of 49.1% were reached. The main reaction involved is as follows (Skalny et al, 2008a(Skalny et al, , 2008b):…”

Radical Photochemistry in Oxygen‐Loaded Ices

“…O 3 may further dissociate by photolysis, by electronstimulated dissociation, [25,29] or by collision. [16] The maximum intensity of the O 3 peak corresponds to the maximum concentration of O 3 when an equilibrium between the production/destruction of the product is achieved.…”