The Droplet Population Balance Model – Estimation of Breakage and Coalescence

“…For a Kühni and a RDC extraction column the published standard hydrodynamic relationships for axial dispersion of both of the phases and the slip velocity have been used so far. The breakage of the droplets was calculated on the basis of a modified We-number by Cauwenberg et al [14] adapted to the specific column geometry by Modes [12] and Simon et al [15,25]. A new attempt was made to assess the droplet swarm hydrodynamics of this two stirred extraction columns on coalescence models based on the film drainage for undeformable and deformable drops with partially mobile interfaces, using the lubrication approximation of Chesters [8].…”

Section: Resultsmentioning

confidence: 99%

Assessment of Drop Coalescence and Breakup for Stirred Extraction Columns

et al. 2005

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This work is a model assessment study considering two major hydrodynamic parameters: the holdup of the dispersed phase and the Sauter diameter. This is done for two different types of extraction columns, namely, the rotating disc contactor (RDC) and the Kühni column, using different drop breakup and coalescence models in a droplet population balance model. Based on the film drainage models for undeformable (spherical drops) and deformable drops with partially mobile interfaces, different simulations have been performed and the results compared with experimental values. The agreement between the experimental observation and the simulation is encouraging and the used models have proven to be suitable to predict holdup and Sauter diameter profiles for the system toluene/water. IntroductionExtraction columns are widely used in petroleum, pharmaceutical and chemical industries, mainly with physical extraction systems [1,2]. Their advantage is their high efficiency and low cost in respect of number of stages, solvent inventory, settler area, site area, maintenance, etc. [3, 4]. The choice of the most appropriate model for calculating a given type of a liquid-liquid extraction column is not straightforward. Most of the recent models [5,6] aim to study the influence of breakup and coalescence rates in turbulent dispersions on hydrodynamics and mass transfer. Drop coalescence and breakage are key parameters for a fundamental understanding of the behavior of liquid-liquid dispersions in extraction columns. These two processes are dynamic in nature and, in a turbulent flow field, depend on the drop sizes, the 552

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“…Currently, there is no general correlation to predict the coalescence rate. However, basic experiments in a Venturi-tube have shown that the coalescence probability of droplets strongly depends on the droplet size, the hold-up and system properties [68][69][70]. Therefore, it is not possible to introduce a correlation for predicting the droplet coalescence independent of solving the population balance equation describing this phenomenon.…”

Section: Coalescence Parameters Estimation Pac-kagementioning

confidence: 99%

LLECMOD: A Bivariate Population Balance Simulation Tool for Liquid- Liquid Extraction Columns

Attarakih¹,

Bart²,

Steinmetz³

et al. 2008

TOCENGJ

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Abstract:The population balance equation finds many applications in modelling poly-dispersed systems arising in many engineering applications such as aerosols dynamics, crystallization, precipitation, granulation, liquid-liquid, gas-liquid, combustion processes and microbial systems. The population balance lays down a modern approach for modelling the complex discrete behaviour of such systems. Due to the industrial importance of liquid-liquid extraction columns for the separation of many chemicals that are not amenable for separation by distillation, a Windows based program called LLECMOD is developed. Due to the multivariate nature of the population of droplets in liquid -liquid extraction columns (with respect to size and solute concentration), a spatially distributed population balance equation is developed. The basis of LLECMOD depends on modern numerical algorithms that couples the computational fluid dynamics and population balances. To avoid the solution of the momentum balance equations (for the continuous and discrete phases), experimental correlations are used for the estimation of the turbulent energy dissipation and the slip velocities of the moving droplets along with interaction frequencies of breakage and coalescence. The design of LLECMOD is flexible in such a way that allows the user to define droplet terminal velocity, energy dissipation, axial dispersion, breakage and coalescence frequencies and the other internal geometrical details of the column. The user input dialog makes the LLECMOD a user-friendly program that enables the user to select the simulation parameters and functions easily. The program is reinforced by a parameter estimation package for the droplet coalescence models. The scale-up and simulation of agitated extraction columns based on the populations balanced model leads to the main application of the simulation tool.

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The Droplet Population Balance Model – Estimation of Breakage and Coalescence

Cited by 38 publications

References 11 publications

Modeling fluid behavior and droplet interactions during liquid–liquid separation in hydrocyclones

Modeling fluid behavior and droplet interactions during liquid–liquid separation in hydrocyclones

Assessment of Drop Coalescence and Breakup for Stirred Extraction Columns

LLECMOD: A Bivariate Population Balance Simulation Tool for Liquid- Liquid Extraction Columns

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