HR: 1340h
AN: H23D-1617    [Abstracts]
TI: Efficient Heat and Mass Transfer Formulations for Oil Shale Retorting
AU: * Parker, J C
EM: jparker@utk.edu
AF: Universtiy of Tennessee, Civil and Environmental Eng, Knoxville, TN 37996-2010, United States
AU: Zhang, F
EM: zhangf@ornl.gov
AF: Oak Ridge National Laboratory, Bethel Valley Road, Oak Ridge, TN 38831, United States
AB: A mathematical model for oil shale retorting is described that considers kerogen pyrolysis, oil coking, residual carbon gasification, carbonate mineral decomposition, water-gas shift, and phase equilibria reaction. Reaction rate temperature-dependence is described by Arrhenius kinetics. Fractured rock is modeled as a bi-continuum consisting of fracture porosity in which advective and dispersive gas and heat transport occur, and rock matrix in which diffusive mass transport and thermal conduction occur. Heat transfer between fracture and matrix regions is modeled either by a partial differential equation for spherical conduction or by a linear first-order heat transfer formulation. Mass transfer is modeled in an analogous manner or assuming local equilibrium. First-order mass and heat transfer coefficients are computed by a theoretical model from fundamental rock matrix properties. The governing equations are solved using a 3-D finite element formulation. Simulations of laboratory retort experiments and hypothetical problems indicated thermal disequilibrium to be the dominant factor controlling retort reactions. Simulation accuracy was unaffected by choice of mass transfer formulation. However, computational effort to explicitly simulate diffusive mass transfer in the rock matrix increased computational effort by more than an order of magnitude compared with first-order mass transfer or equilibrium analyses. A first-order heat transfer approximation of thermal conduction can be used without significant loss of accuracy if the block size and/or heating rate are not too large, as quantified by a proposed dimensionless heating rate.
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1805 Computational hydrology
DE: 1849 Numerical approximations and analysis
DE: 5134 Thermal properties
SC: Hydrology [H]
MN: 2007 Fall Meeting