Criteria for chemical equilibrium with application to methane steam reforming |
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Affiliation: | 1. Laboratorio de Procesos Catalíticos, Dpto. de Ingeniería Química, ITHES (UBA-CONICET), Universidad de Buenos Aires (UBA), Ciudad Autónoma de Buenos Aires, Argentina;2. Grupo de Procesos Catalíticos (PROCAT), Universidad de Málaga (UMA), Málaga, Spain;1. Department of Chemical Engineering, Aristotle University of Thessaloniki, University Campus, GR-54124 Thessaloniki, Greece;2. ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Technical Unit for Renewable Energy Sources (UTRINN), via Anguillarese 301, 00123 Rome, Italy;1. Department of Chemical Engineering, Faculty of Engineering, University of Sistan and Baluchestan, Zahedan, Iran;2. Faculty of Chemical Engineering, Petroleum and Gas, University of Shiraz, Shiraz, Iran |
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Abstract: | A literature survey reveals significant inaccuracy of the prediction of equilibrium models. A thermodynamic analysis is presented to show that the equilibrium calculations rest on a critical assumption of reversible heat exchange between a reactive system and its surrounding. Indeed, a correct application of the energy conservation and entropy balance equation leads to a modified Gibbs function. Minimization of the modified Gibbs function happens to be identical to maximization of the total entropy generation. The actual chemical equilibrium is shown through a methane steam reforming, as an illustrative example, to be correctly predicted by kinetic modeling. The state of chemical equilibrium does not necessarily correspond to maximum entropy generation. Once a chemical equilibrium has been established, both the total entropy generation and the modified Gibbs function remain unaltered and independent of time. |
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Keywords: | Chemical equilibrium Entropy generation Modified gibbs energy Kinetic model Steam reforming |
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