H 2 S destruction in 50 Hz and 25 kHz gliding arc reactors

Abstract

The destruction of foul smelling gases is an important subject involving a number of industrial applications. Increased interest is being devoted to technologies based on the properties of cold plasmas, which are the subject of a large body of research. Among all possible techniques, the sliding discharge is one of the simplest to utilize. We present a study of the destruction of H2S diluted in air by this type of discharge at two frequencies; 50 Hz and 25 kHz. We first describe the electric power supplies, their characteristics, and the design of the reactor. The properties of the discharge and its changes are then described at the above two frequencies. We performed measurements of voltage, current, velocities, and length of the discharge. After describing the instrumentation used for chemical diagnoses, the main experimental results are presented. They show the changes in the conversion rate as a function of the flow rate, of the gas to treat and of the frequency. It was thus possible to determine how destruction efficiency is affected by voltage, flow rates, and frequency of the power supply. The experimental results obtained show that the efficiency is greater at 50 Hz. This effect is not produced by the dependence of chemical mechanisms with the frequency. At low frequency it is possible to obtain greater lengths of the discharge than those obtained with high frequencies, which is why the destruction is better. At the same time, energy cost was compared for both frequencies. In favorable cases, we observed that about 500 eV per molecule permit a conversion rate of 75% at 50 Hz and only 55% at 25 kHz. This cost, which seems very high compared to other techniques, is due to the important dilution of the gliding discharge device, but the order of magnitude of the power consumption is 1 W/ℓ of gas treated.