A correlation for interfacial area in co-current gas-liquid downflow through packed beds
TL;DR: In this article, the interfacial area in cocurrent gas-liquid downflow through packed beds is correlated taking into consideration the physical properties of the fluids and the power dissipation in the system.
Abstract: Interfacial area in cocurrent gas-liquid downflow through packed beds is correlated taking into consideration the physical properties of the fluids and the power dissipation in the system. The correlation is tested with the experimental data covering a wide range in system variables including low and high porosity packings, the flow rates of the phases and their physical properties.
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TL;DR: In this paper, a review of the physical parameters for various multiphase reactors is presented, focusing on gas-phase catalyzed processes with an emphasis on unsteady state operation.
Abstract: Conventional and emerging processes that require the application of multiphase reactors are reviewed with an emphasis on catalytic processes. In the past, catalyst discovery and development preceded and drove the selection and development of an appropriate multiphase reactor type. This sequential approach is increasingly being replaced by a parallel approach to catalyst and reactor selection. Either approach requires quantitative models for the flow patterns, phase contacting, and transport in various multiphase reactor types. This review focuses on these physical parameters for various multiphase reactors. First, fixed-bed reactors are reviewed for gas-phase catalyzed processes with an emphasis on unsteady state operation. Fixed-bed reactors with two-phase flow are treated next. The similarities and differences are outlined between trickle beds with cocurrent gas–liquid downflow, trickle-beds with countercurrent gas–liquid flow, and packed-bubble columns where gas and liquid are contacted in coc...
329 citations
TL;DR: In this paper, a double-slit model was developed to predict the frictional two-phase pressure drop, external liquid holdup, pellet-scale external wetting efficiency, and gas-liquid interfacial area in cocurrent downflow trickle-bed reactors operated under partially wetted conditions in the trickle flow regime.
Abstract: A double-slit model developed can predict the frictional two-phase pressure drop, external liquid holdup, pellet-scale external wetting efficiency, and gas–liquid interfacial area in cocurrent downflow trickle-bed reactors operated under partially wetted conditions in the trickle flow regime. The model, an extension of the Holub et al. (1992, 1993) mechanistic pore-scale phenomenological approach, was designed to mimic the actual bed void by two inclined and interconnected slits: wet and dry slit. The external wetting efficiency is linked to both the pressure drop and external liquid holdup. The model also predicts gas–liquid interfacial areas in partially wetted conditions. An extensive trickle-flow regime database including over 1,200 measurements of two-phase pressure drop, liquid holdup, gas–liquid interfacial area and wetting efficiency, published in 1974–1998 on the partial-wetted conditions, was used to validate the modeling approach. Two new improved slip-factor functions were also developed using dimensional analysis and artificial neural networks. High-pressure and -temperature wetting efficiency, liquid holdup, pressure drop, and gas–liquid interfacial area data from the literature on the trickle-flow regime using conventional monosized beds and catalyst bed-dilution conditions were successfully forecasted by the model.
88 citations
TL;DR: In this article, the state-of-the-art of the gas-liquid mass transfer characteristics in trickle-bed reactors was summarized and its quantification methods were reevaluated based on a wide-ranging data base of some 3200 measurements.
78 citations
TL;DR: In this paper, a set of reliable correlations has been recommended for the prediction of the gas−liquid interfacial area (agl), the volumetric liquid- (kla) and gas-side (kga) mass-transfer coefficients, the wall heat-transfer coefficient (hw), the bed effective radial thermal conductivity (λe), and the particle-to-fluid heat transfer coefficient (hp).
Abstract: Meticulous inspection of the literature has unveiled the weakness of several empirical methods for predicting the macroscopic mass- and heat-transfer characteristics relevant to gas−liquid cocurrent downflow and upflow packed-bed reactors. In response, using a wide experimental database consisting of 5279 measurements for trickle beds (downflow) and 1974 measurements for packed bubble columns (upflow), a set of reliable correlations has been recommended for the prediction of the gas−liquid interfacial area (agl), the volumetric liquid- (kla) and gas-side (kga) mass-transfer coefficients, the wall (ηeklw) and bed (ηekls) liquid−solid mass-transfer coefficients, the wall heat-transfer coefficient (hw), the bed effective radial thermal conductivity (λe), and the particle-to-fluid heat-transfer coefficient (hp). Some of these correlations are from the literature, and others have been developed by combining artificial neural networks and dimensional analysis. The accuracy of the proposed correlations surpasses...
59 citations
TL;DR: A phenomenological description and a semi-empirical two-zone model for the gas−liquid interfacial areas and the volumetric liquid-side mass-transfer coefficients in cocurrent downflow t... is proposed in this article.
Abstract: A phenomenological description and a semiempirical two-zone model are proposed for the gas−liquid interfacial areas and the volumetric liquid-side mass-transfer coefficients in cocurrent downflow t...
58 citations
Cites background or result from "A correlation for interfacial area ..."
...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)....
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...…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., 1980, 1984; Midoux et al., 1984; Morsi, 1989; Venkata Ratnam and Varma, 1991; Wild et al., 1992; Venkata Ratnam et al., 1994)....
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References
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TL;DR: In this paper, the theory of gas absorption accompanied by fast pseudo-mth order reaction was used to obtain values of effective interfacial area in a packed column, irrigated with aqueous solutions and provided with 1 in.C. Raschig rings, 1 in in.P.V.
51 citations
"A correlation for interfacial area ..." refers background in this paper
...It was reported [ 3 , 4] that the shape and material of packing determine the interfacial area in the column....
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TL;DR: In this article, a column packed with glass spheres of 3 different sizes (2.59-12.2 mm) was measured for two-phase cocurrent flow of O2-water and CO2-NaOH systems.
Abstract: Volumetric absorption coefficient (ka)lg, specific interfacial area alg and mass transfer coefficient klg were measured for two-phase cocurrent flow of O2-water and CO2-NaOH systems in a column packed with glass spheres of 3 different sizes (2.59-12.2 mm). Values of (ka)lg observed were so high as to be that can be hardly attainable in conventional gas-liquid contactors. This is due to large alg of small bubbles dispersed in liquid where alg very often exceeds the geometrical surface area of packing. Values of klg range from 2 to 8×10-4m/sec, which are comparable to that of circulating bubbles in the usual systems. The effect of superficial gas velocity on (ka)lg and alg is much greater than that in a countercurrent packed column, while the effect of liquid velocity is approximately same. A liquid-phase energy loss El per unit volume of liquid contained in a bed was newly defined as a measure of microscopic flow intensity and was used for discussion and correlation of mass transfer properties. It was found that the bubble diameter is proportional to El-2/5.
49 citations
TL;DR: In this paper, the authors measured the interfacial area and liquid-side mass transfer coefficients in a 5cm diameter trickle-bed reactor operating with organic liquids. But their results were limited to the case of CO 2 -NaOH and O 2 −Na 2 SO 3.
49 citations
"A correlation for interfacial area ..." refers background in this paper
...Midoux et al. [ 10 ] noted that the interfacial area, pressure drop and liquid holdup systematically increased with increase in the liquid viscosity and liquid flow rate at constant flow rate of the gas....
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...Data [4] [6] [9] [ 10 ] [11] No. ofpoints (67) (20) (42) (54) (29) Correlation Min Max RMS Min Max RMS Min Max RMS Min Max RMS Min err err err err err err err err err err err err err Max RMS err err...
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TL;DR: In this paper, mass transfer coefficients with gas and liquid phase controlling resistance using a concurrent flow packed column with a wide range of operating conditions and four types of packing were measured and correlated with dissipated energy values.
Abstract: Measurements were made of mass transfer coefficients with gas and liquid phase controlling resistance using a concurrent flow packed column with a wide range of operating conditions and 4 types of packing. Mass transfer coefficients were much larger than those obtainable in countercurrent towers. The results were correlated with dissipated energy values. The correlations obtained can be used to determine absorption efficiency. Experimental results show that the use of a high velocity concurrent flow column is particularly suitable when mass transfer is controlled by the liquid phase resistance with chemical reaction in the liquid. (18 refs.)
46 citations
"A correlation for interfacial area ..." refers background in this paper
...The interfacial area was reported to depend on the type of hydrodynamic regime [ 7-9 ]....
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TL;DR: In this article, the theory of gas absorption accompanied by fast pseudo-m th order reaction was used to obtain values of effective interfacial area in 10,15 and 20 cm i.d. packed columns which were operated co-currently.
33 citations
"A correlation for interfacial area ..." refers background in this paper
...The interfacial area in cocurrent gas-liquid downftow through packed beds was reported much larger than that realised in countercurrent flow of the phases [5]; the former was, once again, reported to give about twice that of the specific area of the packing at high gas and liquid flow rates [ 4 ]....
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...Of Intalox saddles, Pall rings and Raschig rings having nearly the same geometric surface area arid packing density, Intalox saddles were reported to give the highest interfacial area at any given superficial liquid velocity [ 4 ]....
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...Data [ 4 ] [6] [9] [10] [11] No. ofpoints (67) (20) (42) (54) (29) Correlation Min Max RMS Min Max RMS Min Max RMS Min Max RMS Min err err err err err err err err err err err err err Max RMS err err...
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...It was reported [3, 4 ] that the shape and material of packing determine the interfacial area in the column....
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