Use of ethanol is attracting increasing attention both as primary feedstock and as an alternative to increase the feedstock flexibility in a given unit. However, steam reforming of ethanol is not a straight forward process. Equilibrium of the reaction is shifted towards the production of hydrogen even at low temperature. However, in practice, ethanol is also converted to ethylene. The present study is focused primarily upon the production of hydrogen in fixed-bed reactors by steam-ethanol reforming under different temperature conditions. Computational fluid dynamics is used to model fluid flow, heat and mass transfer, and chemical reactions. The governing integral equations are solved for the conservation of mass, momentum, and energy and other scalars such as laminar flow and chemical species. Steady-state analyses are performed using computational fluid dynamics. The reaction rates are computed by the laminar finite-rate model. The present study aims to explore how to effectively produce hydrogen in fixed-bed reactors by steam-ethanol reforming at different temperatures. Particular emphasis is placed upon the effect of temperature on the transport and reaction characteristics of fixed-bed reactors for polymer electrolyte membrane fuel cell applications. The results indicate that under a thermodynamic point of view, high temperatures and steam-ethanol molar ratios promote hydrogen yield. Low ethylene content is obtained at high pressure and low temperature. At high temperatures the contribution of steam reforming reactions results in a marked increasing of overall enthalpy, enhancing process endothermicity, whereas the exothermic contribution of water-gas shift and methanation reactions reduces the external heat supply and the overall energy penalty at lower temperature. Although the equilibrium of the water-gas shift reaction favors the products formation at lower temperatures, reaction kinetics are faster at higher temperatures. The typical products distribution of ethanol steam reforming reaction, according to thermodynamic evaluations, results in considerable hydrogen production rates at higher temperatures and high methane yields at lower temperatures. The majority of supported metals as catalysts expresses better performance at high temperatures, and the production of oxygenated products increases and the formation of coke is thermodynamically favored at low temperatures. Low reaction temperatures generally favor the Boudouard reaction mechanism while methane decomposition is the main route at high temperatures.

Keywords: Hydrogen; Ethanol; Reformers; Burners; Reforming; Combustion