Environmental Engineering Reference
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Fig. 1 Scheme of combustion and coke zones in a combustion tube
Fig. 2 Scheme of combustion tube and pore-scale domain for simulation
in the movement of oxygen through the clean zone until the coke zone be reached.
With this aim, the production of combustion gases are ignored as these travel mainly
ahead the coke consumption zone. Under the same premise, within the clean zone
we consider only nitrogen and oxygen.
In order to carry out simulations at the pore-scale we need to reduce the solution
domain to decrease the computing costs. With this aim, as depicted in Fig. 2 ,from
the combustion tube containing a core surrounded by an annular fracture we take a
small region encompassing some few solid particles. For the sake of simplicity, we
adopt some assumptions and we focus only in the oxygen transport and its interaction
with the coke through a combustion reaction. It is assumed that this reaction does
not release heat neither produce other gases, i.e., the combustion reaction is used
only to simulate the oxygen and coke consumption over the particles surface. The
assumptions are summarized as follows:
(1) There is only gas in the system, avoiding the existence of oil and water. This is
an idealized system, which can be found behind a combustion front (see Fig. 1 ).
(2) Initially there is coke homogeneously distributed over the entire particles surface.
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