A cellular automata model for liquid distribution in trickle bed reactors

“…Recently some models have recognized the uneven distribution of liquid phase (Iliuta and Larachi 2005;Alopaeus et al 2006), but only rarely has any notice been taken of factors causing liquid spreading. For example, in case of a single-point liquid distribution, the current models fail to reproduce the measured pressure drop, liquid holdup, and final liquid distribution due to their inability to properly account for the radial spreading of the liquid phase.…”

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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“…Whereas, in many cases biofilm formation is connected with fouling phenomena [26], this is not the case in trickle bed reactors for syngas fermentation where the organic loading rate is low and does not allow for high microbial growth. The basic drawback is channeling [27], that is the flow of the liquid through limited paths across the packed bed resulting in a non-homogenous biofilm growth in the reactor and lower CH4 productivity rates. The operational parameters that are amenable to optimization are the liquid recirculation rate, the gas inflow rate and the hydraulic retention time.…”

Section: Introductionmentioning

confidence: 99%

Biomethanation of Syngas by Enriched Mixed Anaerobic Consortia in Trickle Bed Reactors

Asimakopoulos

Gavala

Skiadas

2019

Waste Biomass Valor

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A cellular automata model for liquid distribution in trickle bed reactors

Cited by 6 publications

References 25 publications

Liquid flow texture analysis in trickle bed reactors using high-resolution gamma ray tomography

Liquid flow texture analysis in trickle bed reactors using high-resolution gamma ray tomography

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

Biomethanation of Syngas by Enriched Mixed Anaerobic Consortia in Trickle Bed Reactors

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