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CFD modeling and simulation of clogging in packed beds with nonaqueous media



When liquids containing low concentrations of fine solid impurities are treated in packed-bed reactors, clogging develops and starts hampering the flow severely. This phenomenon, called deep-bed filtration, constitutes serious concern over hydrotreating or hydrocracking of bituminous sands in packed-bed reactors, in which such nonfilterable fines as native clay or incipient coke cause reactor dysfunction by clogging. A detailed k-fluid Eulerian 2-D transient computational-fluid dynamic (CFD) model was formulated to describe the space-time evolution of clogging patterns developing in deep-bed filtration of the liquids. A local formulation of the macroscopic logarithmic filtration law is proposed, as well as a geometrical model for the effective specific surface area of momentum exchange. Both mono- and multiple-layer deposition mechanisms were accounted for by including appropriate filter coefficient formulations. Transient, 2-D axisymmetrical simulations were benchmarked using experimental results and observations of Narayan et al. (1997) of the carbon-black contaminated kerosene flow through packed beds. Comparing the simulations and experiments showed that CFD is useful for the quantitative description of packed-bed clogging.

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