This paper presents the results of a theoretical and experimental study of plasma-assisted reforming of ethanol into molecular hydrogen in a new modification of the "tornado" type electrical discharge.Numerical modeling clarifies the nature of the non-thermal conversion and explains the kinetic mechanism of nonequilibrium plasma-chemical transformations in the gas-liquid system and the evolution of hydrogen during the reforming as a function of discharge parameters and ethanol-to-water ratio in the mixture. We also propose a scheme of chemical reactions for plasma kinetics description. It is shown that some characteristics of the investigated reactor are at least not inferior to characteristics of other plasma chemical reactors.
PACS: 52.65.-y, 52.80.-s
IntroductionThe interest to alternative fuels research in the last two decades is increased by the depletion of the traditional fossil fuels. Today, ethanol is considered the most perspective fuel for internal-combustion engines [1]. First, it could be produced from renewable sources (biomass, industrial waste, etc). Second, its combustion produces relatively small amount of pollutants. However, the low velocity of the ethanol combustion wave propagation does not allow its use in its pure form as an engine fuel [2]. In order to increase this velocity, one needs to enrich С 2 Н 5 ОН by molecular hydrogen [3], since the latter has higher flame speed than alcohol. Unfortunately, there is another problem of storing H 2 on a vehicle. Recently, several methods were proposed to obtain hydrogen from hydrocarbon fuels before its entering to the engine [1]. The methods are partial oxidation, steam reforming, dry CO 2 reforming, thermal decomposition and plasma-assisted reforming.The use of non-equilibrium plasma looks more attractive as a result of its lower energy consumption. Plasma acts as a catalyst and initiates fast chain reactions that do not progress under normal conditions. Today different plasma chemical reactors are used (for example [1], [4][5][6]) for molecular hydrogen generation from different hydrocarbons (ethanol, methane, etc) in non-equilibrium plasma. In [7][8], a new plasma chemical reactor for ethanol-to-hydrogen conversion was proposed. It was shown
This paper presents the results of complex experimental and theoretical studies of the process of nonthermal plasma-assisted reforming of ethanol-based fuels in the dynamic plasma liquid systems using the DC and pulsed electric discharges in a gas channel with liquid wall (DGCLW) and the DC discharge in a reverse vortex gas flow of Tornado type with a "liquid" electrode (TORNADO-LE). In addition to the direct plasma reforming, also pyrolysis of ethanol after initial plasma treatment was studied. The experiments demonstrate possibilities and efficiency of low-temperature plasma-chemical conversion of ethanol into hydrogen-rich synthesis gas in different regimes. The numerical modeling clarifies the nature and explains the kinetic mechanisms of nonequilibrium plasma-chemical transformations in the plasma-liquid systems in different discharge modes.
Nomenclature
Id= discharge current U = discharge voltage W = electric power G = gas flow rate T = temperature p = pressure
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