A CFD model for prediction of critical electric potential preventing membrane fouling in oily waste water treatment

Monfared, Maryam Abbasi; Kasiri, Norollah; Mohammadi, Toraj

doi:10.1016/j.memsci.2017.05.077

Cited by 13 publications

(5 citation statements)

References 66 publications

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“…Despite numerous experimental and numerical studies on microfiltration for O/W emulsion separation, the detailed behaviors of oil droplets inside the membrane microporous structure are not well understood because of the limitations of the visualization techniques in experimental studies and low-resolution CFD models used in the numerical studies. In most numerical studies, simple generic geometries, such as a single-cylinder, were used to model the membrane pore, ,,− while the geometry of a real membrane is very complex, consisting of different morphologies and pore structures with variable pore diameters. Furthermore, in most conventional CFD modeling of the microfiltration of oil droplets, only one droplet was considered.…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Numerical Simulation of Microfiltration of Oil-in-Water Emulsion Permeating through a Realistic Membrane Microporous Structure Generated by Focused Ion Beam Scanning Electron Microscopy Images

et al. 2022

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Owing to the limitations of visualization techniques in experimental studies and low-resolution numerical models based on computational fluid dynamics (CFD), the detailed behavior of oil droplets during microfiltration is not well understood. Hence, a high-resolution CFD model based on an in-house direct numerical simulation (DNS) code was constructed in this study to analyze the detailed dynamics of an oil-in-water (O/W) emulsion using a microfiltration membrane. The realistic microporous structure of commercial ceramic microfiltration membranes (mullite and αalumina membranes) was obtained using an image processing technique based on focused ion beam scanning electron microscopy (FIB-SEM). Numerical simulations of microfiltration of O/W emulsions on the membrane microstructure obtained by FIB-SEM were performed, and the effects of different parameters, including contact angle, transmembrane pressure, and membrane microporous structure, on filtration performance were studied. Droplet deformation had a strong impact on filtration behavior because coalesced droplets with diameters larger than the pore diameter permeated the membrane pores. The permeability, oil holdup fraction inside the pores, and rejection were considerably influenced by the contact angle, while the transmembrane pressure had a little impact on the permeability and oil hold-up fraction. The membrane structure, especially the pore size distribution, also had a significant effect on the microfiltration behavior and performance.

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Section: Introductionmentioning

confidence: 99%

High-Resolution Numerical Simulation of Microfiltration of Oil-in-Water Emulsion Permeating through a Realistic Membrane Microporous Structure Generated by Focused Ion Beam Scanning Electron Microscopy Images

et al. 2022

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“…To reduce the potential for fouling development, several methods have been proposed and developed. They can be, broadly, divided into two main categories: namely, physical methods and chemical methods. ,− One of the most effective ways to physically combat fouling has been filtration under a crossflow setup. That is the feed emulsion is forced to continuously flow along the membrane length to stress pinned droplets to detach the surface. , This introduces one more parameter (namely; the crossflow velocity) to the optimization exercise of the operating conditions to maximize the filtration capacity and at the same time minimize fouling development.…”

Section: Introductionmentioning

confidence: 99%

Coalescence of an Oil Droplet with a Permeating One over a Membrane Surface: Conditions of Permeation, Recoil, and Pinning

Salama

2021

Langmuir

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When a droplet lands over a nonwetting surface it forms a convex interface that makes a contact angle larger than 90°. If the droplet lands over a pore opening, an interface is also formed at the pore opening that can prevent the droplet from permeating. The conditions for permeation and pinning are very much related to a threshold critical pressure that above which the droplet will permeate. This property defines a selectivity criterion for microfiltration processes of oily water systems using membrane technology. Such a feature of the membrane gets compromised, however, due to the permeation of droplets that are relatively smaller in size or whose critical entry pressure is smaller than the applied transmembrane pressure (TMP). In this work, we investigate what happens to a droplet when it coalesces with a droplet that undergoes permeation. Two scenarios are considered: namely, (1) a droplet coalesces with a permeating one whose interface inside the pore has not broken through the pore exit and (2) a droplet coalesces with a permeating one whose interface in the pore has broken through. We show that a larger droplet (that will essentially not permeate if pinned over a membrane opening) will now permeate when the pore is filled with oil from a preceding one or recoils when the interface inside the pore of a preceding droplet has not broken through the exit of the pore. This has interesting implications for the rejection capacity of the membrane, which decreases due to the permeation of droplets that would, otherwise, not permeate. A computational fluid dynamic (CFD) study has been conducted to confirm the conclusions obtained from the theoretical study and to reproduce the fates of the combined droplet after coalescence at the surface of the membrane. Furthermore, a simplified formula for estimating the critical entry pressure is developed.

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“…One, however, can highlight three modeling approaches. The first is phenomenological and experimental in nature (e.g., Hermia models), ,, the second is computational using the tools of computational fluid dynamics (CFD) to model the process of permeation, and the third is related to the microfiltration of a single droplet to gain understanding of the physics involved during the filtration of oil droplets. ,, Recently, another modeling approach has been developed that utilizes the knowledge obtained from the studies of the microfiltration processes and upscaled to encounter the whole membrane and feed systems. This is called the multicontinuum approach. , The multicontinuum approach stems from the possibility of constructing fate maps for every size range of oil droplets at every size of membrane pore opening.…”

Section: Introductionmentioning

confidence: 99%

“…Apparently, this modifies the formula derived for the critical pressure due to the changes of the curvature of the interface in the feed channel. However, through the CFD studies conducted by Darvishzadeh et al, , such modifications seem to be insignificant and, therefore, there is a great deal of agreement among researchers − to use the formula of Nazzal and Wiesner to estimate conditions of permeation. This may be because the influential factor in determining the condition of permeation is indeed related to the interface at pore entrance, which does not really change.…”

Section: Introductionmentioning

confidence: 99%

Simplified Formula for the Critical Entry Pressure and a Comprehensive Insight into the Critical Velocity of Dislodgment of a Droplet in Crossflow Filtration

Salama

2020

Langmuir

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Produced water treatment remains a challenging issue for the oil production industry. Finding ways to effectively treat oily water systems without incurring higher operational costs is the struggle and focus of recent research work. The success in establishing a modeling approach to study the filtration of oily water systems is dependent upon our understanding of the fate of oil droplets at the membrane surface. It has been determined that four fates confront oil droplets at the membrane surface, namely, permeation, breakup, pinning, and rejection. Conditions for manifestation of any of these four fates depend on two operating conditions (transmembrane pressure and crossflow velocity) in comparison with two critical conditions (entry pressure and critical velocity of dislodgment). In this work, a new simplified formula for the critical entry pressure is introduced. It compares very well with the formula already existing in the literature. Furthermore, the complete model for the critical velocity of dislodgment in crossflow filtration is presented and highlighted. More investigations on the physical processes that are involved during the pinning of a droplet at a pore opening are presented. In addition, a thorough analysis of the forces that are involved during the permeation of a droplet that could lead to its breakup is presented. It is found that, once the droplet reaches the pore opening, the interfacial tension force and the pressure force continue to increase. Following the critical configuration, these forces continuously decline and the drag force due to the crossflow field, therefore, becomes sufficient to break up the droplet.

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A CFD model for prediction of critical electric potential preventing membrane fouling in oily waste water treatment

Cited by 13 publications

References 66 publications

High-Resolution Numerical Simulation of Microfiltration of Oil-in-Water Emulsion Permeating through a Realistic Membrane Microporous Structure Generated by Focused Ion Beam Scanning Electron Microscopy Images

High-Resolution Numerical Simulation of Microfiltration of Oil-in-Water Emulsion Permeating through a Realistic Membrane Microporous Structure Generated by Focused Ion Beam Scanning Electron Microscopy Images

Coalescence of an Oil Droplet with a Permeating One over a Membrane Surface: Conditions of Permeation, Recoil, and Pinning

Simplified Formula for the Critical Entry Pressure and a Comprehensive Insight into the Critical Velocity of Dislodgment of a Droplet in Crossflow Filtration

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