The impact of valve tray geometry on the interfacial area of mass transfer

Liang, Yanyan; Zheng, Zhuo; Shao, Min; Geng, Jiao; Wu, Youting; Zhang, Zhibing

doi:10.1002/aic.11489

Cited by 9 publications

(25 citation statements)

References 22 publications

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“…However, the ratio of liquid height to tray diameter is less than 1 in distillation/absorption columns; thus, bubbles cannot be fully developed. 14 The maximum bubble diameter is closely related to the energy dissipation rate of the system and the properties of the fluid. Another factor affecting the maximum bubble diameter is the residence time of bubbles in the gas-liquid dispersion.…”

Section: Resultsmentioning

confidence: 99%

“…11,14,15 The experimental data are summarized in 13 However, the space height of the column was not provided; thus, the exact LP/SP ratio is unknown. Moreover, estimation was performed to obtain the LP/SP.…”

Section: Validation Of the Extended New Interfacial Area Modelmentioning

confidence: 99%

“…Foaming would not occur in this system because NaOH can increase the water surface tension. In Liang's system, 14 foaming can be ignored because the system is air-water. However, moderate or heavy foaming would occur in the systems of Azrak 12 and Peytavy 13 because DEA can decrease the water surface tension.…”

Section: Data For Model Development and Testingmentioning

confidence: 99%

“…Models are developed using small-scale tray experimental data. [11][12][13][14] These models are empirical and semiempirical. However, the effect of gas-liquid nonideal flow on the interfacial area was not considered in such models; thus, they cannot be used to predict the gas-liquid interfacial area of large-scale trays.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Prediction of gas–liquid interfacial area in valve trays

Wang¹,

Leng²,

Shao³

et al. 2015

AIChE Journal

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An accurate prediction of gas-liquid interfacial area is very important for the design and optimization of column trays. However, the difference of the gas-liquid flow regimes operating at different scale trays significantly affect the interfacial area calculation. Therefore, in this study, an interfacial area model operating at small column was established using the Kolmogorov's isotropic turbulence hypothesis. According to the analyzes of the gas-liquid flow phenomena of different scale columns, an assumption that the similarity principle of flow characteristics of gas-liquid in full contact was proposed. Moreover, a new model that can be used to predict the gas-liquid interfacial area of a large column with exiting the nonideal flow was obtained through the extension of the small tray interfacial area model based on this principle. Finally, the new model was tested by comparisons with the experimental results of references. The prediction accuracy significantly improved with the maximum deviation of approximately 40%. V C 2015 American Institute of Chemical Engineers AIChE J, 62: 905-915, 2016 Keywords: distillation, different scales, valve tray, interfacial area, physical model IntroductionDistillation is the major process in present and future petroleum and/or chemical industries.1 Heat and mass transfers between gas and liquid phases occur in trays during distillation. Briefly, these transfer processes occur via phase interface. Hence, the interfacial area is an important field of investigation in chemical engineering research. Generally, studies on the interfacial area have mainly focused on two aspects: (1) increasing the contact interfacial area of the gasliquid interface by some means or the optimization of equipment structures to enhance the mass and heat transfer processes and (2) developing gas-liquid interfacial area models to predict the transfer of mass or heat. Valve trays grafted with some special structures are widely used as contactors for distillation/absorption columns because of their high tray efficiency, relatively low pressure drop, and large operation range (enhanced performance).2 However, previous research on hydrodynamics and mass transfer has mainly focused on sieve trays, [3][4][5][6][7][8][9][10] and little attention has been centered on valve trays.11-15 Therefore, high-accuracy models should be developed on the basis of theoretical research regarding the actual flow characteristics of gas-liquid in valve trays to calculate the hydraulic and mass transfer rates. These models will provide theoretical guidance for the reasonable design and optimization of trays.Column diameter and height are two main parameters involved in industrial column design. The column diameter is controlled by two-phase flow hydrodynamic behavior (weeping or flooding), whereas the total column height is controlled by mass transfer parameters. 15 To date, the actual trays of a column (cf. column height) are determined by two main methods: (1) tray efficiency based on equilibrium stage model [16][17][18] an...

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Section: Resultsmentioning

confidence: 99%

Section: Validation Of the Extended New Interfacial Area Modelmentioning

confidence: 99%

Section: Data For Model Development and Testingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Prediction of gas–liquid interfacial area in valve trays

Wang¹,

Leng²,

Shao³

et al. 2015

AIChE Journal

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show abstract

“…Liang et al (2008) had considered u t 2 related to the local energy dissipation when the isotropic turbulence is assumed in the gas dispersion field, and thus is described as Eq. (20).…”

Section: Size Distribution For Bubblesmentioning

confidence: 99%

Simulation of the Bubble Behaviors for Gas–Liquid Dispersion in Agitated Vessel

Liu

Sheng

Han

et al. 2017

J. Chem. Eng. Japan / JCEJ

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The present study mainly investigates bubble behaviors in an agitated vessel. Computational uid dynamics provides a method for exploring the complex uid ow in an agitated vessel. A stirred tank model with transport equation for the interfacial area concentration and force equilibrium equation for bubbles under multi-forces is created for a 43-dm 3 agitated vessel. The model considers the breakage and coalescence mechanism of the bubbles. The local gas holdup is measured by ber-optical probe. After this, the bubble size distributions are calculated by the interfacial area concentration model. The simulations with validated models show good agreement with the experiments. From the simulation results, the area in which the gas holdup value is greater than 0.01 extends 37% in the upper circulation region when the rotation speed is increased to 40 rad/s from 20 rad/s. However, in the lower circulation, the gas holdup maintains a low level due to the existence of a "death zone". The simulations indicate that the bubble breakage mainly occurs in the impeller out ow region and the coalescence occurs in the upper circulation region. For bubble behaviors being in the lower circulation region, bubble coalescence or breakage is determined by the ow eld pattern in the vessel. Moreover, it is di cult for the simulation process to converge when the virtual mass force is considered and there is a lack of effective technology to measure it, which has led researchers to generally ignore this force. In order to analyze the virtual mass force, the present study utilizes computer programming which is based on the virtual mass force formula to obtain the force. The results show that at positions close to the impeller tip and the center of the upper region, the virtual mass force value is 0.015 and 0.017, respectively, but the value is approximately zero in the bulk of the tank. Hence, the bubble has two signi cant stages of acceleration process in the vessel.

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Theoretical and experimental investigation on the characteristics of fly‐ash scrubbing in a fixed valve tray column

2012

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in Wiley Online Library (wileyonlinelibrary.com).The goal of this study is to evaluate the performance of a fixed valve tray column designed to remove fly-ash particles. A series of experiments were carried out at room temperature to demonstrate the collection efficiency of a fixed valve tray column at different gas and liquid superficial velocities. The fly-ash particles removal characteristics of the fixed valve tray column were evaluated by measuring variations of concentration and size distribution of particles in the outlet. The mechanism of particle removal in this turbulent dispersion system was theoretically analyzed on the basis of diffusion, interception, sedimentation and impaction, and a model was proposed to predict the collection efficiency. The results show that the simulation results agree well with the experimental data. In contrast to most of the conventional models, the present model is capable of evaluating the effects of bubble hydrodynamics, system property, and operation conditions on the collection efficiency. The model is expected to guide effectively the design and operation of valve tray washing columns, which is widely applied nowadays.

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The impact of valve tray geometry on the interfacial area of mass transfer

Cited by 9 publications

References 22 publications

Prediction of gas–liquid interfacial area in valve trays

Prediction of gas–liquid interfacial area in valve trays

Simulation of the Bubble Behaviors for Gas–Liquid Dispersion in Agitated Vessel

Theoretical and experimental investigation on the characteristics of fly‐ash scrubbing in a fixed valve tray column

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