Comparison of unidirectional and bi-directional pulse driven corona discharge reactors for decomposition of hazardous gases

It is well known that both positive and negative pulse driven corona discharge reactors are effective in the decomposition of hazardous exhaust and flue gases. It is also reported in the literature that sinusoidal voltage driven reactors also have some advantages. The authors investigated earlier the effect of bi-directional pulses on corona reactors for freons. The action of bi-directional pulses is that fast rising pulses occur with the same pulse shape alternately both in the positive and negative directions. In this paper the comparison of these methods is made. The effects of the positive, negative and bi-directional pulses on a 120 cm long cylindrical reactor with the internal diameter of 6 cm were tested. The pulse peak voltage was varied between 10 and 35 kV in both directions. The width of the pulse was in the interval of 300–500 ns, the rise time was 35–50 ns. The gases investigated were nitrous oxide and sulphur dioxide. During the experiments, the voltage and the discharge current were measured, and the energy was calculated. In most cases, the result was that the positive sign pulse was the most effective, but the advantage of the negative pulse and the bi-directional pulse were also justified in some cases.