Hydrogen production from ethanol steam reforming. Fixed Bed Tubular Reactor Design

PABLO GIUNTA; MIGUEL LABORDE; NORMA AMADEO

Mérida - México

Simposio; Hydrogen Power Theorethical and Engineering Soluctions internacional Symposium (HYPOTHESIS VII); 2007

The global energy system transition from fossil fuel to hydrogen utilization is the most viable alternative for the future, considering the environmental and sustainability issues related with the energy. The hydrogen production is an appropriate environmental solution if it can be obtained from renewable sources like ethanol or other fuels derived from biomass. Ethanol is a very good candidate for several reasons: i) ethanol is renewable and is becoming increasingly available, ii) it is easy to transport, biodegradable and has low toxicity, iii) it is easy to decompose in the  presence of water by steam reforming reaction to generate a H2-rich mixture. In addition, H2 production from ethanol steam reforming is not only environmental friendly but also would be an opportunity for the utilization of renewable sources. The stoichiometry of the ethanol reforming reaction can be represented as follows: C2H5OH + 3 H2O ↔ 2 CO2 + 6 H2 Nevertheless, the ethanol steam reforming can occur in several reaction pathways depending on catalyst and reactor conditions. It should be pointed out that, as the catalytic reaction is a heterogeneous gas-solid process and the ethanol conversion rate is very fast, the reaction might be affected by both mass and heat transfer limitations. On the other hand, very few kinetic and reactor design studies have been reported about ethanol steam reforming. Then, based on kinetic studies carried out by our group over Ni/Al2O3 catalyst, the intrinsic kinetic obtained is employed to design a fixed bed tubular reformer fed with ethanol and water. The aim of the present work is to perform a numeric simulation of this reactor, considering the mass transfer with simultaneous reaction inside the catalyst pellet. In order to take into account the various driving forces acting on each species, the Dusty Gas Model was used instead of the Fick Model. The effectiveness factor was obtained for each species. Plug flow reactor was considered as the fluid dynamic model to size a fixed bed catalytic reactor. The results can be useful to estimate the minimum size of reactor and, more important, understanding the sources of performance limitations. This knowledge can to lead to future improvements of the reactor configuration.