We investigate clogging of microchannels at the single-pore level using microfluidic devices as model porous media. The process of clogging is studied at low volume fractions and high flow rates, a technologically important regime. We show that clogging is independent of particle flow rate and volume fraction, indicating that collective effects do not play an important role. Instead, the average number of particles that can pass through a pore before it clogs scales with the ratio of pore to particle size. We present a simple model that accounts for the data.

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Mechanism for clogging of microchannels.

Data from 6 filtration studies, representing 43 experiments, are analyzed with a simplified version of the single-parameter O'Melia and Ali clogging model. The model parameter displays a systematic dependence on fluid velocity, which was an independent variable in each study. A cake filtration model also explains the data from one filtration study by varying a single, velocity-dependent parameter, highlighting that clogging models, because they are empirical, are not unique. Limited experimental data indicate exponential depth dependence of particle accumulation, whose impact on clogging is quantified with an extended O'Melia and Ali model. The resulting two-parameter model successfully describes the increased clogging that is always observed in the top segment of a filter. However, even after accounting for particle penetration, the two-parameter model suggests that a velocity-dependent parameter representing deposit morphology must also be included to explain the data. Most of the experimental data are described by the single-parameter O'Melia and Ali model, and the model parameter is correlated to the collector Peclet number.

/pdf/hydrodynamic-aspects-of-particle-clogging-in-porous-media-2qf19szyxj.pdf

Hydrodynamic aspects of particle clogging in porous media.

Publisher Summary This chapter provides a brief review of major characteristics of reservoir structures and lithologies serving as a guide to reservoir selection for CO 2 disposal. The chapter focuses on existing experience and uncertainties in reservoir characterization and response to CO 2 injection and long-term containment of sequestration sites. Special issues germane to CO 2 disposal arise in the assessment of depleted reservoirs, whose properties are known to have changed during single or repeated pore-pressure drawdown and fluid redistribution. Oil and gas reservoirs and aquifers share some common geometric elements. Generally, both are tabular bodies in which the fluid flow is constrained by upper and lower less-permeable lithologies. Primary aspects of CO 2 sequestration in geologic formations include the geohydrologic characterization, injection behavior, and long-term containment of supercritical CO 2 for storage in aquifers and reservoirs. The efficiency of a CO 2 enhanced oil-recovery flood depends strongly on the equilibrium phase behavior of mixtures of CO 2 with the oil.

Terrestrial sequestration of CO2: An assessment of research needs

Trickle-bed reactors (TBRs), which accommodate the flow of gas and liquid phases through packed beds of catalysts, host a variety of gas–liquid–solid catalytic reactions, particularly in the petroleum/petrochemical industry. The multiphase flow hydrodynamics in TBRs are complex and directly affect the overall reactor performance in terms of reactant conversion and product yield and selectivity. Non-ideal flow behaviours, such as flow maldistribution, channelling or partial catalyst wetting may significantly reduce the effectiveness of the reactor. However, conventional TBR modelling approaches cannot properly account for these non-ideal behaviours owing to the complex coupling between fluid dynamics and chemical kinetics. Recent advances in the application of computational fluid dynamics (CFD) to three-phase TBR systems have shown promise of achieving a deeper understanding of the interactions between multiphase fluid dynamics and chemical reactions. This study is intended to give a state-of-the-art overview of the progress achieved in the field of CFD simulation of TBRs over the past two decades. The fundamental modelling framework of multiphase flow in TBRs, advances in important constitutive models, and the application of CFD models are discussed in detail. Directions for future research are suggested.



RESUME Les lits fixes arroses a co-courant descendant de gaz et de liquide sont le siege d'innombrables processus catalytiques triphasiques, en particulier dans le domaine du raffinage petrolier et de la petrochimie. Les caracteres polyphasique et non-ideal de leur hydrodynamique ont des repercussions importantes sur la conversion chimique, la productivite et la selectivite. Ceci se traduit par l'entremise de la maldistribution des fluides, le mouillage partiel du catalyseur ou des ecoulements preferentiels qui peuvent etre determinants en ce qui a trait a l'efficacite du reacteur. La mise en equation rigoureuse de ces non-idealites et des couplages reaction-hydrodynamique a longtemps resiste aux approches de conceptualisation dites « conventionnelles ». Cette revue de synthese s'attarde par consequent a discuter les recentes avancees dans l'utilisation de la mecanique des fluides numerique comme outil « emergent et non-conventionnel » de description quantitative et fine des ecoulements et des reactions catalytiques, et de leur interaction au sein de ces reacteurs. Specifiquement, nous discuterons de la pertinence des differentes approches multi-fluides mises en œuvre, des relations constitutives developpees et de l'utilisation de la mecanique des fluides numerique pour des applications pratiques des lits fixes arroses. Nous suggererons en guise d'epilogue de nouvelles directions de recherche dans ce domaine. © 2011 Canadian Society for Chemical Engineering

Modelling and simulation of trickle‐bed reactors using computational fluid dynamics: A state‐of‐the‐art review

Two pilot-scale fractured aquifer models (FAMs) consisting of horizontal limestone slabs were employed to investigate the removal of biocolloids suspended in reclaimed wastewater. To better understand the behavior of real fractured aquifers, these FAMs intentionally were not “clean”. The fracture apertures were randomly spread with soil deposits, and both FAMs were preflooded with reclaimed wastewater to simulate the field conditions of the Nardo fractured aquifer in the Salento area, Italy, where fractures are not clean due to artificial groundwater recharge. One of the FAMs was injected with secondary effluent from a wastewater treatment plant collected prior to the chlorination step and the other with exactly the same effluent, which was further treated in a commercial membrane reactor. Consequently, the organic and pathogen concentrations were considerably higher in the secondary effluent than in the membrane reactor effluent. Injected wastewater was continuously recirculated. Pathogen removal was gre...

Removal of biocolloids suspended in reclaimed wastewater by injection into a fractured aquifer model.

Fine particles in the liquid feed to packed-bed reactors can be trapped in the catalyst bed, which eventually leads to excessive pressure drop. The fine particles can include coke, corrosion products, clays, and other minerals. The catalyst bed functions as a granular filter to remove particles much smaller than the size of the pores between the catalyst pellets. The efficiency for trapping the particles in the packed bed depends on the flow fields and the attractive forces between the packing and the fine particles. In order to understand the capture of fine particles from nonaqueous media, we studied a model system of carbon black in kerosene. Columns packed with glass beads and a catalyst were operated over a range of flow velocities to Reynolds numbers from 0.1 to 2.3, on the basis of the diameter of the packing in the bed. Flow was in the upward and in the downward direction. The filter coefficient and efficiency were sensitive to liquid velocity. Trapping was slightly more efficient with downward fl...

José R. Coury

Papers

Particle capture and plugging in packed-bed reactors