Effective interfacial area in gas-liquid cocurrent downflow through packed beds

Ratnam, G. S. Venkata; Varma, Y. B. G.

doi:10.1007/bf00383575

Cited by 11 publications

(3 citation statements)

References 13 publications

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“…At a given pressure, the interfacial areas and the two-phase pressure drops exhibit the expected increase with gas and liquid velocities. Such trends coincide with those already reported for atmospheric conditions (Morsi et al, 1980;Midoux et al, 1984;Wild et al, 1992;Venkata Ratnam et al, 1994). For low liquid or gas superficial velocity (u L ) 0.14 cm/s, u G ≈ 2 cm/s), a weakly depends on pressure (Figure 2a).…”

Section: Resultssupporting

confidence: 91%

“…Accurate evaluation of the gas-liquid mass-transfer parameters is, therefore, essential for achieving a successful reactor design and scaling. Earlier investigations of gas-liquid mass-transfer characteristics of TBRs were mostly limited to atmospheric pressure (Gianetto et al, 1973;Hirose et al, 1974;Charpentier, 1976;Fukushima and Kusaka, 1977;Bakos et al, 1980;Morsi et al, 1980Morsi et al, , 1984Midoux et al, 1984;Morsi, 1989;Venkata Ratnam and Varma, 1991;Wild et al, 1992;Venkata Ratnam et al, 1994). Only a few researchers have studied how gas-liquid mass transfer evolves at elevated pressures Wild et al, 1992;Larachi et al, 1992;Lara-Marquez et al, 1992;Cassanello et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Gas−Liquid Interfacial Mass Transfer in Trickle-Bed Reactors at Elevated Pressures

Larachi

Cassanello

Laurent

1998

Ind. Eng. Chem. Res.

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A phenomenological description and a semiempirical two-zone model are proposed for the gasliquid interfacial areas and the volumetric liquid-side mass-transfer coefficients in cocurrent downflow trickle-bed reactors operated at elevated pressure. Gas-liquid interfacial areas, a, and volumetric liquid-side mass-transfer coefficients, k L a, are measured in the trickle flow regime at high nitrogen pressure (0.3-3.2 MPa). Use is made of diethanolamine carbamation in aqueous viscous and organic model solutions in which fast and slow absorptions of carbon dioxide occur. In order to extract genuine mass-transfer parameters, a rigorous thermodynamic model is established to account for liquid and gas nonidealities. The influence of pressure, gas and liquid superficial velocities, liquid viscosity, and packing size on the gas-liquid interfacial mass transfer is examined. At constant gas and liquid superficial velocities, increasing the reactor pressure improves the gas-liquid interfacial mass transfer at the expense of increased two-phase pressure drop and gas holdup. At high pressure, the gas-liquid flow may be viewed as a two-zone flow pattern: (i) a liquid-free gas continuous phase which delineates a macroscopic gas-liquid interface (ii) and a gas-liquid film emulsion comprised of tiny bubbles which form in the films and delineate a microscopic gas-liquid interface. Taylor's theory of fluid-fluid sheared emulsions is used to quantify the microscopic interface via the effect of pressure on the size of bubbles in the trickling film. A bubble Sauter diameter is related to viscous shear stress and surface tension force, the two competing forces that determine bubble size. The model is also extended to estimate volumetric gas-liquid mass-transfer coefficients under high-pressure conditions.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Gas−Liquid Interfacial Mass Transfer in Trickle-Bed Reactors at Elevated Pressures

Larachi

Cassanello

Laurent

1998

Ind. Eng. Chem. Res.

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“…high interaction region, as suggested by Specchia and Baldi. 9 The criteria for discriminating between the low and high interaction regions were determined using the relation (LG 23 Therefore, it is proposed to analyze the effect of all the variables through various combinations of dimensionless groups. The effect of individual flow rates (gas and liquid) have been accounted by the corresponding gas and liquid Reynolds number, Re g and Re l , whereas the combined effect of the liquid properties have been included in the form of the Morton number, Mo l , along with the bed characteristics (bed voidage, ε) and particle characteristics (size and shape) as follows:…”

Section: Two-phase Pressure Dropmentioning

confidence: 99%

Prediction of two‐phase pressure drop and liquid holdup in co‐current gas–liquid downflow of air–Newtonian systems through packed beds

Babu

Arunagiri

Murugesan

2005

J of Chemical Tech & Biotech

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The dependency of pressure drop and liquid holdup on phase velocities, geometry of the column and packing materials as well as on the physical properties have been analyzed. Our experimental data (825 data points obtained using four liquid systems and three different particles) along with those of the available literature (776 data point from five different sources) were used for the analysis. The applicability and the limitations of the literature correlations were evaluated using the available data. Based on the analysis, new correlations for the estimation of pressure drop and liquid holdup, valid for low and high interaction regimes have been developed using the available data, with a wide range of variables.

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Impact of gravity on the bubble‐to‐pulse transition in packed beds

Salgi

Balakotaiah

2013

AIChE Journal

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A model based on two-phase volume-averaged equations of motion is proposed to examine the gravity dependence of the bubble-to-pulse transition in gas-liquid cocurrent down-flow through packed beds. As input, the model uses experimental correlations for the frictional pressure drop under both normal gravity conditions and in the limit of vanishing gravity, as well as correlations for the liquid-gas interfacial area per unit volume of bed in normal gravity. In accordance with experimental observations, the model shows that, for a given liquid flow, the transition to the pulse regime occurs at lower gas-flow rates as the gravity level or the Bond number is decreased. Predicted transition boundaries agree reasonably well with observations under both reduced and normal gravity. The model also predicts a decrease in frictional pressure drop and an increase in total liquid holdup with decreasing gravity levels. V C 2013 American Institute of Chemical Engineers AIChE J, 60: [778][779][780][781][782][783][784][785][786][787][788][789][790][791][792][793] 2014

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Effective interfacial area in gas-liquid cocurrent downflow through packed beds

Cited by 11 publications

References 13 publications

Gas−Liquid Interfacial Mass Transfer in Trickle-Bed Reactors at Elevated Pressures

Gas−Liquid Interfacial Mass Transfer in Trickle-Bed Reactors at Elevated Pressures

Prediction of two‐phase pressure drop and liquid holdup in co‐current gas–liquid downflow of air–Newtonian systems through packed beds

Impact of gravity on the bubble‐to‐pulse transition in packed beds

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