Article

Effect of reactor configuration on nitric oxide conversion in nitrogen plasma

AIChE Journal (Impact Factor: 2.58). 05/2005; 51(6):1813 - 1821. DOI: 10.1002/aic.10451

ABSTRACT The configuration of a nonthermal plasma reactor strongly affects the rate of electron collision reactions. Experiments involving the decomposition of NO in N2 were performed in a reactor in which the number of parallel reactor tubes varied from 1 to 10 at a constant pressure of 147.6 kPa and ambient temperature. A previously developed lumped model of the reactions accurately predicted the effects of varying the initial concentrations of NO (from 240 ppm to 593 ppm) and gas residence time (from 1.93 to 7.42 s). With an increasing number of parallel reactor tubes, the rate of electron collision reactions decreases because the energy input per unit reactor volume at unit time decreases, while the energy consumption per molecule of NO converted to N2 and O2 decreases due to electrical and geometric effects associated with the decreasing peak width of the discharge voltage pulses and increasing reactor capacitance. Therefore, increasing the number of parallel reactor tubes provides a viable scale-up method for constructing more efficient pulsed corona discharge reactors. © 2005 American Institute of Chemical Engineers AIChE J, 2005

1 Bookmark
 · 
44 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This work explores the effect of gas pressure on the rate of electron collision reactions and energy consumption for NO conversion in N2 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 . 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, , 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 N2 decreases with increasing gas pressure.
    Chemical Engineering Science. 01/2005;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hydrogen sulfide (H2S) dissociation into hydrogen and sulfur has been studied in a pulsed corona discharge reactor (PCDR). Due to the high dielectric strength of pure H2S (∼2.9 times higher than air), a nonthermal plasma could not be sustained in pure H2S at discharge voltages up to 30kV with our reactor geometry. Therefore, H2S was diluted with another gas with lower dielectric strength to reduce the breakdown voltage. Breakdown voltages of H2S in four balance gases (Ar, He, N2, and H2) have been measured at different H2S concentrations and pressures. Breakdown voltages are proportional to the partial pressure of H2S and the balance gas. With increasing H2S concentrations, H2S conversion initially increases, reaches a maximum, and then decreases. H2S conversion and the reaction energy efficiency depend on the balance gas and H2S inlet concentrations. H2S conversion in atomic balance gases, such as Ar and He, is more efficient than that in diatomic balance gases, such as N2 and H2. These observations can be explained by proposed reaction mechanisms of H2S dissociation in different balance gases. The results show that nonthermal plasmas are effective for dissociating H2S into hydrogen and sulfur.
    Chemical Engineering Science 04/2007; 62(8):2216-2227. · 2.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: NO is mainly converted to NO2 by chemical oxidation in the presence of oxygen. Initial selectivity analysis shows that three electron collision reactions are important for NOx evolution in O2/N2. The rate constants of these reactions decrease with increasing oxygen concentration. This is because oxygen is electronegative and thus reduces electron concentration. The rate constant of O2 dissociation by electron collision reaction is almost two orders of magnitude higher than that of N2 dissociation. NO formation occurs predominantly through N(2D) + O2 → NO + O. The critical oxygen concentration, defined as the concentration at which the NOx formation rate counterbalances the NOx decomposition rate, increases with increasing initial NO concentration. © 2005 American Institute of Chemical Engineers AIChE J, 2005
    AIChE Journal 05/2005; 51(6):1800 - 1812. · 2.58 Impact Factor