Liquid–solid wetting factor in trickle-bed reactors: its determination by a physical method

Pironti, F. F.; Mizrahi, Daniela; Acosta, A.; González-Mendizabal, Dosinda

doi:10.1016/s0009-2509(98)00493-x

Cited by 36 publications

(35 citation statements)

References 20 publications

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“…In the past decades, the liquid–solid contacting efficiency has been estimated mostly in the indirect manners—the tracer technology or the reaction rate method . Although hydrodynamic method has been considered in some research, however, it was only defined as the ratio of the two shear stresses in two‐phase and in liquid‐phase flow, without evaluating the wetting condition of the bed or directly correlated with the pressure drop and Reynolds number, without knowing the real wetting condition of packing. Therefore, the understanding on liquid–solid contacting up to now is rather superficial, the external wetting efficiency is simply considered as a lumped function of the liquid physical property, the pellet geometry and diameter, the porosity of the reactor, and the liquid velocity.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic modeling on the external liquid–solid wetting efficiency in a trickling flow reactor

et al. 2012

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A three-region model was proposed, which considers the bed cross section being composed of a stagnant liquid region, a liquid film region, and a rivulet flow region. To estimate the fractions of the three regions, the fraction of film flow was evaluated first, by transforming the complex trickling flow texture into pure liquid film flow. Through the measurements of liquid holdup and pressure drop for the film flow, a relationship between relative permeability and gas saturation was established, and from which the fraction of film flow region was obtained. It shows packing size is most important to the faction of rivulet flow. The external wetting efficiency of the packing was correlated as the sum of two-third power of the liquid film fraction and the rivulet flow fraction, besides, a correlation based on Reynolds and Galileo numbers of the two phases in the form of ce ¼ 4.85Re 0:42 L Ga À0:25 L Re 0:083 G was proposed.

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Section: Introductionmentioning

confidence: 99%

Hydrodynamic modeling on the external liquid–solid wetting efficiency in a trickling flow reactor

et al. 2012

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“…Due to the above reasons, liquid distribution in the industrial scale differs from the laboratory scale. Experimental reactors are highly susceptible for liquid maldistribution, at least in atmospheric pressure with low flow rates (Lutran et al 1991;Sundaresan 1994;Møller et al 1996;Wang et al 1998;Pironti et al 1999;van der Merwe and Nicol 2005). Nonetheless, when hydrodynamic models and pressure drop correlations for trickle-bed reactors are developed and tested based on laboratory experiments, liquid distribution has often been assumed to be uniform (Holub et al 1992(Holub et al , 1993Attou et al 1999;Iliuta and Larachi 1999;Jiang et al 2002a,b;Narasimhan et al 2002).…”

Section: Introductionmentioning

confidence: 99%

An Analytical Model for Capillary Pressure–Saturation Relation for Gas–Liquid System in a Packed-Bed of Spherical Particles

Lappalainen¹,

Manninen

Alopaeus³

et al. 2008

Transp Porous Med

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Capillary pressure is considered in packed-beds of spherical particles. In the case of gas-liquid flows in packed-bed reactors, capillary pressure gradients can have a significant influence on liquid distribution and, consequently, on the overall reactor performance. In particular, capillary pressure is important for non-uniform liquid distribution, causing liquid spreading as it flows down the packing. An analytical model for capillary pressure-saturation relation is developed for the pendular and funicular regions and the factors affecting capillary pressure in the capillary region are discussed. The present model is compared to the capillary pressure models of Grosser et al. (AIChE J., 34:1850(AIChE J., 34: -1860(AIChE J., 34: , 1988 and Attou and Ferschneider (Chem. Eng. Sci., 55:491-511, 2000) and to the experiments of Dodds and Srivastava (Part Part Syst. Charact., 23:29-39, 2006) and Dullien et al. (J. Colloid Interface Sci., 127:362-372, 1989). The non-homogeneity of real packings is considered through particle size and porosity distributions. The model is based on the assumption that the particles are covered with a liquid film, which provides hydrodynamic continuity. This makes the model more suitable for porous or rough particles than for non-porous smooth particles. The main improvements of the present model are found in the pendular region, where the liquid dispersion due to capillary pressure gradients is most significant. The model can be used to improve the hydrodynamic models (e.g., CFD and cellular automata models) for packed-bed reactors, such as trickle-bed reactors, where gas, liquid, and solid phases are present. Models for such reactors have become quite common lately (Sáez and Carbonell, AIChE J., 31:52-62, 1985; K. Lappalainen (B) · V. Alopaeus Chemical Engineering and Plant Design, Nomenclatures A c Cross-sectional area (m 2 ) d Half spacing between neighboring microcylinders (m) d p Particle diameter (m) d min As defined in Eq. 5 (m) D H Hydraulic diameter (m) f Wetting efficiency J (S L ) Leverett's J -function k Permeability (m 2 ) N c Number of particle contact points per particle p c Capillary pressure (Pa) p i Pressure of phase i (Pa) r 1,2 Scaled radii of curvature R 1,2 Radii of curvature (m) R Particle radius (m) R * Mean curvature of the meniscus (m) s Perimeter (m) S L Liquid saturation V f Volume of fluid in a pendular ring (m 3 )Greek letters ε Void fraction of the packed-bed ϕ Filling angle (see Fig. 3) (rad) (x) Gamma function θ Liquid-solid contact angle (rad) θ i Holdup of phase i ρ i Density of phase i (kg · m −3 ) σ Surface tension between the wetting and the non-wetting phases (N · m −1 ) X(1 − cos ϕ)

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“…However, several methods have been proposed to measure the wetting efficiency f in trickle-bed reactors: dynamic tracer technique, 6,7 chemical reaction method, 8 and more recently, hydrodynamic technique 9 and magnetic resonance imaging technique (MRI). 10 Except MRI, all those approaches are overall, indirect, and require a model of reactor involving hydrodynamic, transfer, and/or kinetic parameters.…”

Section: Introductionmentioning

confidence: 99%

Wetting topology in trickle bed reactors

Baussaron¹,

Julcour-Lebigue²,

Wilhelm³

et al. 2007

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).Local and average partial wetting efficiencies in trickle-beds have been directly measured by image processing and PIV analysis. Two different setups have been implemented: a vertical monolayer of pellets where the wetting structure and stability and also local velocity gradient are characterized by PIV, and a fixed bed to analyze (by photography) the axial evolution of wetting over bed cross section after a transient injection of dye. Porous alumina spheres and different liquids have been used to examine the effect of liquid-solid affinity; two liquid distributors, and bed prewetting were investigated at low liquid superficial velocities (0.5 Â 10 À3 -10 À2 m/s). Contrary to usual techniques (excepting MRI), not only average wetting efficiencies are derived from the colorimetric tracing, but also local features: axial evolution of wetting, size, and locations of dry zones, distributions of wetting efficiency at a particle scale. All those local data are important to improve reactor models assuming uniform pellet wetting. The effect of liquid-solid affinity is predominant in the case of the monolayer of beads, and, contrary to usual assumption, is still significant for the real trickle bed in the low range of wetting efficiency, corresponding to liquid superficial velocity lower than 2 Â 10 À3 m/s.

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Liquid–solid wetting factor in trickle-bed reactors: its determination by a physical method

Cited by 36 publications

References 20 publications

Hydrodynamic modeling on the external liquid–solid wetting efficiency in a trickling flow reactor

Hydrodynamic modeling on the external liquid–solid wetting efficiency in a trickling flow reactor

An Analytical Model for Capillary Pressure–Saturation Relation for Gas–Liquid System in a Packed-Bed of Spherical Particles

Wetting topology in trickle bed reactors

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