Modelling of Liquid Dispersion in Trickle-Bed Reactors: Capillary Pressure Gradients and Mechanical Dispersion

Lappalainen, Katja; Alopaeus, Ville; Manninen, Mikko; Kallio, Sirpa

doi:10.1615/multscientechn.v21.i1-2.60

Cited by 3 publications

(6 citation statements)

References 13 publications

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“…The movement of liquid along the axial direction is affected by the gravity and the drag force between the liquid and solid, while the movement of liquid along the radial direction is mainly affected by the capillary force. At the low superficial particle velocity, the bed porosity is between 0.38 and 0.41 with the particle of 3 mm, thus the capillary dispersion dominates the liquid spreading, which proved in the simulation work of Lappalainen et al 38,39 This shows that the radial spreading behavior of the liquid is obvious. Therefore, the gas–liquid flow boundary between the gas channel (large white area) and the liquid channel (large black area) in Figure 7B appears randomly, and most of these boundaries are slanted.…”

Section: Resultsmentioning

confidence: 81%

Flow regimes in a gas–liquid–solid three‐phase moving bed

et al. 2021

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The gas–liquid–solid three‐phase moving beds could supply a potential solution for multiphase reactions with catalyst easily deactivated, and the flow regimes in it were studied by optical method and pressure drop measurement. Results showed that taking the trickle flow as the initial flow regime, the flow channels were more obvious as the particle velocity increased. When the initial flow regimes were pulse flow and bubble flow respectively, the pulse‐to‐trickle and bubble‐to‐pulse flow transitions mainly occurred at moderate‐to‐high particle velocities (0.01–0.04 m s−1 under conditions used in this work). Moreover, the flow regime map in the three‐phase moving bed was constructed and shown that the region of trickle flow increased and the region of bubble flow decreased. Finally, the application of three‐phase moving beds was discussed, and it could be suitable for those reactions, which had to operate in the pulse flow, bubble flow, and transition zone.

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Section: Resultsmentioning

confidence: 81%

Flow regimes in a gas–liquid–solid three‐phase moving bed

et al. 2021

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“…The theoretical background of mechanical dispersion forces in packed beds is discussed by Fourati et al . Lappalainen et al proposed mechanical dispersion forces for both the gas and the liquid phase in terms of the spreading factor and specific drift velocities. The mechanical dispersion of liquid and gas phases are

true {\vec{M}}_{normalDisp normal, normalmech normal, normall} = K_{normalls} {\vec{u}}_{normalD normal, normall} + K_{normalgl} ({\vec{u}}_{D, l} - {\vec{u}}_{D, g})

…”

Section: Numerical Detailsmentioning

confidence: 99%

“…The drag due to the interphase coupling is taken into account using the relative permeability approach , which is based on the phasic volume fraction concept, where the solid is considered as a porous body. The forces due to capillary , and mechanical , dispersion are also included in order to study the axial evolution of the liquid distribution. Each phase satisfies the mass and momentum conservation individually, and the sum of the gas and liquid volume fractions is unity in the porous body.…”

Section: Numerical Detailsmentioning

confidence: 99%

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An Eulerian‐Eulerian Computational Approach for Simulating Descending Gas‐Liquid Flows in Reactors with Solid Foam Internals

et al. 2017

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Dedicated to Professor Rüdiger Lange on the occasion of his 65th birthdayChemical reactors with new types of packings, such as metallic and ceramic openpore foams, have become subjects of scientific and engineering interest in the past decades. For trickle bed reactors, the new packing types provide favorable conditions, such as high specific surface area and low pressure drop, which are believed to contribute to an intensification of mass and heat transfer. Here, an attempt was made to model and predict the flow pattern and liquid distribution in a trickle bed reactor with solid foams, using computational fluid dynamics. A three-dimensional model based on the relative permeability approach was adopted, where gas and liquid phases flow co-currently downwards through a reactor with SiSiC ceramic foams as internals. The influence of both mechanical and capillary dispersion was included and studied in detail for foams of two different pore densities and for different initial distribution patterns.

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“…Trickle-bed reactors are employed in petroleum, petrochemical and chemical industries, in waste treatment and in biochemical and electrochemical processing as well as other application [5] Various flow regimes exist in TBRs depending on the superficial mass velocity, fluid properties and bed characteristics [6,7] such as trickle flow, pulsing flow, mist flow and bubble flow [7]. The performance of a trickle-bed reactor is affected, not only by reaction kinetics, pressure, and temperature, but also by reactor hydrodynamics, which are commonly described by means of global parameters such as pressure drop, liquid holdup, dispersion of gas and liquid phases, catalyst wetting, and mass-and heat-transfer coefficients [8]. Liquid holdup and pressure drop in the bed are the two key hydrodynamic parameters whose knowledge is necessary while designing and scaling up of the reactor [9].…”

Section: Introuductionmentioning

confidence: 99%

Hydrodynamics in a Trickle Bed Reactor

Fadel Abd,

Talib Jasim,

Shihab Ahmed

2013

ETJ

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Experimental investigations have been carried out to study the performance of trickle bed reactor. The effect of key parameters that play predominate role in the performance of trickle bed reactor was studied. A laboratory unit was constructed for this purpose where a versatile reactor setup required " high pressure stainless steel reactor of 0.05m i.d × 1.25m height", in which the hydrodynamic experiments carried out under different operating condition namely, superficial gas velocity and liquid velocity , reactor pressure, bed temperature .Air-water system was used for hydrodynamic experiments pressure drop, dynamic liquid holdup, and axial dispersion coefficients were estimated. The results also show that the dynamic liquid holdup increases with increasing liquid velocity and decreases with increasing superficial gas velocity and bed temperature. Axial dispersion tends to increase with increasing superficial gas and liquid velocities while it decreases with increasing bed temperature.

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Modelling of Liquid Dispersion in Trickle-Bed Reactors: Capillary Pressure Gradients and Mechanical Dispersion

Cited by 3 publications

References 13 publications

Flow regimes in a gas–liquid–solid three‐phase moving bed

Flow regimes in a gas–liquid–solid three‐phase moving bed

An Eulerian‐Eulerian Computational Approach for Simulating Descending Gas‐Liquid Flows in Reactors with Solid Foam Internals

Hydrodynamics in a Trickle Bed Reactor

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