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A novel pulsed corona wire-in-tube reactor with quartz view-ports allowed visual observation of the effect of charge voltage and gas composition on the corona distribution. The H2S conversion and energy efficiency of H2S decomposition in this pulsed corona discharge reactor varied at constant power (100 W) due to the selected values of the electrical parameters of pulse forming capacitance (720–2880 pF), charge voltage (11–21 kV), and pulse frequency (157–961 Hz). Low pulse forming capacitance, low charge voltage, and high pulse frequency operation produces the highest energy efficiency for H2S conversion at constant power. H2S conversion is more efficient in Ar–N2 gas mixtures than in Ar or N2. These results can be explained by corona discharge observations, the electron attachment reactions of H2S at the streamer energies, and a proposed reaction mechanism of H2S dissociation in the Ar–N2 gas mixture. The energy consumption per molecule of converted H2S in an equimolar mixture of Ar and N2 (4.9 eV/H2S) is the lowest that has been reported for any plasma reactor operated at non-vacuum pressures. The results reveal the potential for energy efficient H2S decomposition in pulsed corona discharge reactors.

Hydrogen sulfide ( H 2 S ) dissociation into hydrogen and sulfur has been studied in a pulsed corona discharge reactor (PCDR). Due to the high dielectric strength of pure H 2 S ( ∼ 2.9 times higher than air), a nonthermal plasma could not be sustained in pure H 2 S at discharge voltages up to 30 kV with our reactor geometry. Therefore, H 2 S was diluted with another gas with lower dielectric strength to reduce the breakdown voltage. Breakdown voltages of H 2 S in four balance gases (Ar, He, N 2 , and H 2 ) have been measured at different H 2 S concentrations and pressures. Breakdown voltages are proportional to the partial pressure of H 2 S and the balance gas. With increasing H 2 S concentrations, H 2 S conversion initially increases, reaches a maximum, and then decreases. H 2 S conversion and the reaction energy efficiency depend on the balance gas and H 2 S inlet concentrations. H 2 S conversion in atomic balance gases, such as Ar and He, is more efficient than that in diatomic balance gases, such as N 2 and H 2 . These observations can be explained by proposed reaction mechanisms of H 2 S dissociation in different balance gases. The results show that nonthermal plasmas are effective for dissociating H 2 S into hydrogen and sulfur.

This work explores the effect of gas pressure on the rate of electron collision reactions and energy consumption for NO conversion in N 2 in a pulsed corona discharge reactor. A previous study showed that the rate constant of electron collision reactions, multiplied by the electron concentration, can be expressed as k [ e ] = β α - 0.5 P - 0.5 W 0.75 exp ( - α P / W ) . The model parameter α remains constant with increasing gas pressure, which verifies the previous assumption that the electron temperature is inversely proportional to gas pressure. However, the model parameter β decreases with increasing gas pressure, which indicates that the rate constant of electron collision reactions decreases with increasing gas pressure. The new expression for the rate constant of electron collision reactions, k [ e ] = B α - 0.5 P - 1.4 W 0.75 exp ( - α P / W ) , is more general because it explicitly accounts for the effect of gas pressure that was previously contained in the parameter β . The electron mean energy decreases with increasing gas pressure, which results in thermal dissipation of a larger fraction of the energy input to the reactor that heats the gas instead of producing plasma chemical reactions. Therefore, energy efficiency for NO conversion in N 2 decreases with increasing gas pressure.