Flooding Velocities in Packed Columns

Sherwood, T. K.; Shipley, Gabe; Holloway, Frank

doi:10.1021/ie50343a008

Cited by 198 publications

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“…In a rather dramatic indication of the robustness of the relative permeability model, Dankworth and Sundaresan (1989) reversed the direction of flow of the gas phase and were able to obtain reasonable agreement with experimental steady-state liquid holdup and pressure drop data for countercurrent gas-liquid flows in packed beds. In addition, they were able to predict the flooding conditions for countercurrent flow columns, and obtained a remarkable agreement with the correlations of Sherwood and Shipley (1938) and of Hutton and Leung (1974). Tsochatzidis and Karabelas (1994) studied the details of the microscopic and macroscopic flows during the trickling to pulsing flow transitions in a packed bed.…”

Section: Theories Of Trickling To Pulsing Transitionmentioning

confidence: 67%

Multiphase Flow Models in Packed Beds

Carbonell

2000

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Modèles d'écoulements polyphasiques dans les lits garnis -Cette étude présente un examen des théories sur les écoulements des liquides et des gaz dans les lits garnis appliquées au dimensionnement des réacteurs. Des progrès significatifs ont été réalisés dans la connaissance des phénomènes d'écoulements polyphasiques dans les lits garnis et dans la possibilité d'effectuer des pré-visions quantitatives sur le comportement des fluides en écoulement. Certaines théories utilisent avec succès des équations de continuité et de quantité de mouvement moyennées dans l'espace pour les phases liquide et gazeuse, associées à des lois de comportement représentant les forces de traînée entre les phases fluides et les particules ainsi que les effets de la pression capillaire dans la colonne. Il en résulte un ensemble cohérent d'équations qui sont capables de modéliser les données expérimentales pour le taux de rétention du liquide et la perte de charge dans des conditions de régime permanent. Ces théories ont également été utilisées pour donner des informations sur la stabilité de ces écoulements permanents. Un accord remarquable a été trouvé entre les observations expérimentales et les prédictions théoriques sur les transitions entre les régimes à faibles et à fortes interactions. De plus, le même ensemble d'équa-tions a permis de modéliser les écoulements, à la fois en co-et en contre-courant, des phases liquide et gazeuse dans les lits garnis. Cette approche robuste est basée sur les principes fondamentaux de la méca-nique des fluides et peut être appliquée à d'autres configurations de réacteurs. Une formulation similaire a également amélioré la compréhension de l'hydrodynamique des réacteurs à gazosiphon. Certains de ces résultats sont présentés à titre de comparaison ; un résumé des challenges visant à élargir ces modèles hydrodynamiques pour y inclure les effets du transfert de chaleur, du transfert de masse et des vitesses de réaction est également proposé.Mots-clés : force de traînée, perméabilité, perte de charge, rétention, débits de transition, régime hydrodynamique. Abstract -Multiphase Flow Models in Packed Beds

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Section: Theories Of Trickling To Pulsing Transitionmentioning

confidence: 67%

Multiphase Flow Models in Packed Beds

Carbonell

2000

Oil & Gas Science and Technology - Rev. IFP

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“…In most previous works [2][3][4][5][6] liquid hold-ups were investigated by using a cold model of a fixed bed which was soaked prior to experiments (hereinafter called initially soaked bed). The characteristics of liquid hold-ups for BF should be investigated by using a moving bed unsoaked prior to experiments (hereinafter called initially unsoaked bed), because the burden continually descends and is not completely wetted in the lower part of BF.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Liquid Hold-ups in a Soaked and Unsoaked Fixed Bed

Kawabata¹,

Liu²,

Fujita³

et al. 2005

ISIJ Int.

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In most previous works, liquid hold-ups were studied by using a cold model of a fixed bed soaked prior to experiments. However, they did not consider that the dripping zone of a blast furnace is saturated with liquids or with evenly distributed droplets. In the present study, the characteristics of liquid hold-ups and liquid flow were investigated by using a one-dimensional cold model of a fixed bed soaked and unsoaked prior to experiments (initially soaked and unsoaked beds). Packed balls were five kinds, the diameters (D p ) of which ranged from 5.4 to 30 mm. Tap water was used as liquid. Contact angles (q) for these particle/liquid systems were about 70°and 10°for fluorine-coated particles and non-coated particles, respectively.Although, under bad wettability condition (q Լ 70°), total and static hold-ups for initially unsoaked bed packed with small balls are remarkably smaller than those for initially soaked bed, the difference in their hold-ups between initially unsoaked and soaked beds decreases with increasing ball size in the bed. In initially soaked bed, total and static hold-ups increase monotonically as ball size decreases, which means the specific surface area increases. On the other hand, in initially unsoaked bed, total and static hold-ups under bad wettability condition indicate maximum values at about D p ϭ10 mm and decrease abruptly in proportion to a decrease in particle size, despite an increase in the specific surface area. Only restricted liquid droplets and/or liquid rivulets are formed within the packed bed with good wettability condition (qԼ 10°) for initially unsoaked bed, nevertheless liquid is easy to spread out on the solid surface. The influence of the initial bed condition, soaked or unsoaked bed, on liquid hold-ups is great under bad wettability condition.KEY WORDS: ironmaking; blast furnace; dripping zone; fixed bed; liquid hold-ups; particle/liquid wettability; initially soaked and unsoaked beds.

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“…Sherwood et al' s generalised flooding correlation for counter-current packed column 52 (Sherwood et al, 1938).…”

Section: 3mentioning

confidence: 99%

A Non-Wetting Packed Bed Gas Scrubber

Chang

Swithenbank

Sharifi

2007

Process Safety and Environmental Protection

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SummaryPresent integrated gasification combined cycle (IGCC) systems demonstrate high system efficiency and impressive environmental performance, giving them an edge over conventional pulverised fuel power stations. A key area in the development of IGCCs is hot fuel gas clean-up (HGCU). Fuel gas cleaning at elevated temperatures reduces thermal efficiency losses associated with gas quenching in conventional cold gas cleaning methods. Current hot gas desulphurisation techniques focus on the use of regenerable metal oxide sorbents, however the long-term sorbent performance issues have yet to be fully addressed. A fresh and radical approach may provide the key to overcoming the inherent limitations associated with metal oxide sorbents. A molten tin irrigated packed bed scrubber adopted in this research project is one such innovative way forward in HGCU. The hot scrubber offers the prospect of a multicomponent clean-up device.High-temperature sulphur removal takes place via absorption of H 2 S (and COS) into molten tin whilst discrete molten tin droplets and rivulets on the packing surface act as solid particulate collectors.The primary aim of this research project was to investigate the workings of a small-scale roomtemperature packed bed scrubber operating under non-wetting flow conditions analogous to the molten tin irrigated scrubber. Water irrigation of low surface energy packings simulated the nonwetting flow of liquid metals. The air-water analogue of the liquid metal scrubber provided the platform for hydrodynamics (flow visualisation, flooding and liquid holdup), particulate removal and mass transfer studies under non-wetting flow conditions. The performance of a small air lift for water circulation through the column was also investigated. These cold studies offered insight into the operation and performance of the liquid metal hot scrubber.Prior to the cold gas scrubber studies, preliminary small-scale gasification tests on petroleum coke samples were performed to investigate the effect of molten tin on H 2 S in the product fuel gas. The tests provided actual experimental evidence of the possibility of sulphur removal by molten tin in a gasification environment.It was shown that the maximum possible size of a liquid droplet hanging from a non-wetting spherical solid surface could be predicted from the liquid surface tension and density based on force balance. The mobility of static holdup in a non-wettable packed bed has been demonstrated, this being due to the tendency for the liquid to form discrete droplets rather than spreading films. Existing flooding and liquid holdup correlations that hold for conventional wettable packed beds were shown to be inadequate where non-wetting systems were concerned. Summary hence alternative methods applicable to the latter were sought. The introduction of a non-wetting tendency factor based on the ratio of the solid critical surface tension to the liquid surface tension, enabled the flooding capacities of non-wetting systems including those of this study to be predict...

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Flooding Velocities in Packed Columns

Cited by 198 publications

References 0 publications

Multiphase Flow Models in Packed Beds

Multiphase Flow Models in Packed Beds

Characteristics of Liquid Hold-ups in a Soaked and Unsoaked Fixed Bed

A Non-Wetting Packed Bed Gas Scrubber

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