Detailed Kinetic Modelling of Hydrogen Production from Ethanol Reforming for Use in Fuel Cell Power Systems G. Vourliotakis, G. Skevis * and M.A. Founti Laboratory of Heterogeneous Mixtures and Combustion Systems Thermal Engineering Section, School of Mechanical Engineering National Technical University of Athens, Greece Abstract Ethanol is particularly attractive as an alternative fuel for both automotive and stationary applications. Due to its high hydrogen content, ethanol can also be utilized for hydrogen production in SOFC systems. The present study assesses the potential of non-catalytic ethanol reforming process using a detailed kinetic modelling approach. A recently developed comprehensive detailed mechanism for ethanol oxidation, pyrolysis and combustion is used and further validated against data from ethanol reformers. Comparisons between computations and experimental major and intermediate species data are shown to be satisfactory. Chemical aspects of the fuel reforming process are thoroughly investigated through rate of production path and sensitivity analyses with particular emphasis on syngas and potential carbonaceous deposits formation. An assessment of ethanol as a reformate versus conventional fuels with similar hydrogen content is also numerically performed and ethanol is found to feature a higher conversion efficiency to syngas than methane. * Corresponding author: gskevis@central.ntua.gr Associated Web site: http://www.ntua.gr/hmcs Laboratory of Heterogeneous Mixtures and Combustion Systems, School of Mechanical Engineering, National Technical University of Athens, Heroon Polytechniou 9, Polytechnioupoli-Zografou, Athens 15780, Greece Introduction Fuel cell systems constitute a promising alternative technology for both automotive and stationary applications. These systems are operating at relatively low and controlled temperatures compared to conventional power generating systems and have a potential for improved efficiency coupled with reduced emissions. Solid-oxide fuel cells (SOFC) are particularly attractive since they can be incorporated into hybrid systems with CHP capabilities due to their relatively high operating temperatures (650 – 1000 ºC) [e.g. 1-3]. High pressure operation in hybrid systems is also a possibility and efficiencies up to 70% in combined SOFC – gas turbine power systems can be expected [4]. In principle, SOFC operation directly on hydrocarbon fuels is possible [e.g 5], but practical systems rely entirely on fuel reforming processes in order to convert the fuel into hydrogen and/or syngas. Currently methane is the reformate of choice in fuel cell applications mainly in view of its high ratio hydrogen to carbon ratio [e.g. 6]. Reforming of higher pure hydrocarbons (e.g. butane) and practical fuels (e.g. gasoline and diesel) is also an option but has been shown to result in a reduced overall fuel conversion into hydrogen. On the other hand the use of alternative, non- fossil fuels is steadily increasing due to energy security and supply issues and concerns about climate change. Ethanol is a renewable fuel provided it is derived from feedstock, biomass [e.g. 7] and waste products [e.g. 8] and has high enough hydrogen content in order to be a candidate for hydrogen production in fuel cell systems through a reforming process [e.g. 9]. The potential of reforming ethanol for hydrogen production has mainly been explored through experimental and numerical evaluation of the available technologies, such as steam reforming, partial oxidation and autothermal reforming. Steam reforming appears to be the more efficient in terms of hydrogen yield while the exothermic partial oxidation process appears advantageous in terms of system complexity and integration since there is no need for an external heat source or a water balance. For example, ethanol steam reforming equilibrium has been shown to result in high H 2 yields (of the order of 70 %.) under high temperatures (about 1000 K) and water to ethanol molar ratios of the order of 5 [10]. On the other hand, partial oxidation can produce comparable H 2 yields, at similar temperatures, only under near pyrolytic conditions [10]. In order to enhance the overall conversion, reforming takes place in a catalytic environment. Ethanol steam reforming using noble metal catalysts can be realized with 95 % hydrogen selectivity [e.g. 11]. Additionally, catalytic partial oxidation supported by e.g. Rh–Ce catalysts, results in more than 95 % ethanol direct conversion into hydrogen [12]. However, catalysts are sensitive against poisoning, get easily damaged by temperatures higher than 1300 K and show a tendency to degenerate by age. A promising alternative is thermal partial oxidation (T-POX) reforming. The process is non-catalytic, so deactivation problems are not relevant. It also has a good dynamic response and simple system design. Further a T-POX reactor is very fuel flexible since the fuel conversion and product yield depend on operating parameters and are not constrained by potential fuel-catalyst incompatibilities. In order to achieve efficient operation in the absence of catalyst, high temperatures of the order of 1000 K are required. However this is not an issue in SOFC systems since they are already operating at elevated temperatures. Recently, the potential of