A review is made of the theories proposed for quantitative assessment of ozone generation in dc-energized electrostatic precipitators. The underlying simplifying assumptions adopted by these theories are discussed. Among the most important assumptions is ignoring the ozone destruction which takes place at high ozone generation rates. Therefore, a modification is proposed to account for ozone destruction in assessing the generation of ozone. Subsequently, a linear relationship between the ozone generation rate after being modified and the discharge power is obtained by using the present experimental results or the data published previously.

The aim of this paper is to study the effects of the magnitude and direction of air flow rate on the characteristics of the corona discharge generated in a wire-duct reactor. Two air flow directions were attempted: one parallel to, and the other normal to the discharge wire in the reactor. The corona current-voltage characteristics correlative with ozone generation were studied under different modes of applied voltage. The results have shown that dc and ac corona current-voltage characteristics depend significantly on the magnitude of the air flow rate in the reactor, whatever the direction of the air flow. The ozone concentration generated by either dc, ac or pulsed coronas with parallel flow is higher than that generated with normal flow with the same discharge conditions. The ozone concentration generated by pulsed coronas is higher than that generated by either dc or ac coronas with the same discharge conditions irrespective of the polarity of the pulsed corona.

An analytical study was made in this paper for calculating the ozone generation by negative dc corona discharges. The corona discharges were formed in a coaxial wire-cylinder reactor. The reactor was fed by dry air flowing with constant rates at atmospheric pressure and room temperature, and stressed by a negative dc voltage. The current-voltage characteristics of the negative dc corona discharges formed inside the reactor were measured in parallel with concentration of the generated ozone under different operating conditions. An empirical equation was derived from the experimental results for calculating the ozone concentration generated inside the reactor. The results, that have been recalculated by using the derived equation, have agreed with the experimental results over the whole range of the investigated parameters, except in the saturation range for the ozone concentration. Therefore, the derived equation represents a suitable criterion for expecting the ozone concentration generated by negative dc corona discharges in dry air fed coaxial wire-cylinder reactors under any operating conditions in range of the investigated parameters.

This paper is aimed at investigating how the characteristics of corona and silent discharges including ozone generation are influenced by geometry of the discharge reactor. The corona discharges have been generated in coaxial wire-cylinder and wire-duct reactors stressed by dc and ac voltages. The silent discharges have been generated in the same reactors in addition to tubular reactors under ac voltage after pasting a dielectric barrier on the ground electrode of the reactors. The reactors were fed by dry air flowing at atmospheric pressure and temperature. The pulse characteristics of silent discharges are compared with those of ac corona discharges. The current-voltage and the ozone generation characteristics of silent and ac discharges are recorded. These characteristics depend significantly on the geometry of the reactor irrespective of the discharge type. NomenclatureC ozone concentration, ppm d width of the discharge gap, mm dV /dt time derivative of voltage V , kV s −1 P discharge power, W Q air flow-rate through the reactor, litre min −1 r radius of the discharge wire, mm STP standard temperature and pressure conditions V o onset voltage of the discharge (peak value), kV V p applied voltage (peak value), kV