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Smoldering Combustion in Oil Shales: Influence of Calcination and Pyrolytic Reactions

Elayeb, Mustafa and Debenest, Gérald and Mourzenko, Valeri and Thovert, Jean-François Smoldering Combustion in Oil Shales: Influence of Calcination and Pyrolytic Reactions. (2017) Transport in Porous Media, 116 (2). 889-921. ISSN 0169-3913

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Official URL: http://dx.doi.org/10.1007/s11242-016-0805-9

Abstract

A three-dimensional numerical tool for the microscale simulation of smoldering in fixed beds of solid fuels is presented. The description is based on the local equations and accounts the local couplings of the transport and reaction mechanisms. The chemical model includes devolatilization and cracking of the kerogen, calcination of the carbonates contained in a mineral matrix and oxidation of the carbon char left by the pyrolysis. An extensive survey of the functioning regimes exhibits features that have to be taken into account in the operation of a reactor and in its macroscopic modeling. Three dimensionless numbers are shown to control the phenomenology, which embody the effects of the constituent properties and of the operating conditions. One of them, PeF,s, provides an a priori criterion for the validity of a local equilibrium hypothesis and for the applicability of standard homogenized formulations. The numerical observations comply when PeF,s is small with the expectations from a simple homogenized description, including quantitative predictions of the mean temperature profile, of the consumption of the various reactants and of the relative positions of the reaction fronts. Conversely, local equilibrium is not satisfied when PeF,s is large and these approaches fail in several respects. The simple upscaled transport equations are unable to predict the evolution of some of the locally average state variable. Furthermore, strong local deviations of the state variables from their local averages, combined with the nonlinearity of the kinetic laws, cause the overall reaction rates to differ from those deduced from the mean values. Nevertheless, a successful heuristic model for the spread of the hot and potentially reactive region can be stated, which provides an avenue for further studies.

Item Type:Article
Additional Information:Thanks to Springer editor. The definitive version is available at https://link.springer.com/ The original PDF of the article can be found at https://link.springer.com/article/10.1007/s11242-016-0805-9
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > Ecole Nationale Supérieure de Mécanique et d'Aérotechnique - ENSMA (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Other partners > Misurata University (LIBYA)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
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Deposited By: Gerald DEBENEST
Deposited On:12 Jul 2017 09:23

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