Demulsification of crude oil emulsions tracked by pulsed field gradient NMR. Part II: Influence of chemical demulsifiers in external AC electric field

Hjartnes, Tomas Nordeide; Mhatre, Sameer; Gao, Bicheng; Sørland, Geir Humborstad; Simon, Sébastien; Sjöblom, Johan

doi:10.1016/j.colsurfa.2019.124188

Cited by 29 publications

(10 citation statements)

References 48 publications

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“…We are confident that the results presented here will shed light on the stability of fluid interfaces in electric-field-based applications such as electrocoalescence, electrocoagulation, microfluidics, electroemulsification, electrostatic atomization, etc. For instance, during coalescence of two droplets in the presence of an electric field and surface-active compounds, the evolved interfacial properties govern the kinetics of the coalescence. − In the electric-field-controlled microfluidic applications such as microreactor technology, bioparticle handling, assays, etc., future studies could investigate enhancement in the mass transport at/across the interfaces.…”

Section: Discussionmentioning

confidence: 99%

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

2020

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In this work we investigate adsorption of surface active compounds at water-oil interface subjected to an electric eld. A uid system comprising a pendent water drop surrounded by an asphaltene-rich organic phase is exposed to a DC uniform electric eld.Two sub-fractions of asphaltenes having contrasting anities to water-oil interface are used as surface active compounds. The microscopic changes in the drop shape, as a result of asphaltene adsorption, are captured and the drop proles are analyzed by using our in-house code for axisymmetric drop shape analysis (ADSA) under electric eld.The estimates of dynamic interfacial tension under dierent strengths of the eld (E 0 ) and concentrations of the asphaltene sub-fractions (C) are used to calculate adsorption dynamics and surface excess. The experimental observations and careful analysis of the data suggest that the externally applied electric eld signicantly stimulates the mass transfer rate at a liquid-liquid interface. The enhancement in mass transport at 1 water-oil interface can be attributed to the axisymmetric electrohydrodynamic uid ows generated on either sides of the interface. The boost in mass transport is evident from the growing decay in equilibrium interfacial tension (γ eq ) and increased surface excess (Γ eq ) upon increasing strength of the applied electric eld. The mass transfer intensication does not increase monotonously with the electric eld strength above an optimum E 0 , which is in agreement with previous theoretical studies in the literature.However, these rst explicit experimental measurements of adsorption at an interface under electric eld suggest that the optimum E 0 is determined by characteristics of the surface active molecules.

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Section: Discussionmentioning

confidence: 99%

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

2020

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“…Our approach of simulating directly the multiple droplet electrocoalescence to identify critical field strengths is also applicable to a three-dimensional study, although the visualization of the droplets in 3D would require other techniques such as pulsed field gradient (PFG) NMR since the 3D crude would be opaque in a microfluidic arrangement in which the channel height was larger to accommodate a 3D dispersion of droplets. The use of PFG-NMR to study water in crude oil emulsions has been undertaken by Sjoblom et al − …”

Section: Discussionmentioning

confidence: 99%

Microfluidic Study of the Electrocoalescence of Aqueous Droplets in Crude Oil

2020

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In electrocoalescence, an electric field is applied to a dispersion of conducting water droplets in a poorly conducting oil to force the droplets to merge in the direction of the field. Electrocoalescence is used in petroleum refining to separate water from crude oil and in droplet-based microfluidics to combine droplets of water in oil and to break emulsions. Using a microfluidic design to generate a two-dimensional (2D) emulsion, we demonstrate that electrocoalescence in an opaque crude oil can be visualized with optical microscopy and studied on an individual droplet basis in a chamber whose height is small enough to make the dispersions two dimensional and transparent. From reconstructions of images of the 2D electrocoalescence, the electrostatic forces driving the droplet merging are calculated in a numerically exact manner and used to predict observed coalescence events. Hence, the direct simulation of the electrocoalescence-driven breakdown of 2D emulsions in microfluidic devices can be envisioned.

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“…The drop–drop coalescence helps the droplets grow in size, thereby enhancing their terminal settling velocity ( v t ), which is proportional to the square of the diameter of the drop in the Stokes limit . Various research groups have reported the growth of droplets under the application of an electric field for the water-in-oil emulsion system. − In an electrocoalescer, these droplets travel to the interface, where they undergo drop–interface coalescence . The drop–interface coalescence plays an important role in determining the efficiency of an electrocoalescer.…”

Section: Introductionmentioning

confidence: 99%

Coalescence, Partial Coalescence, and Noncoalescence of an Aqueous Drop at an Oil–Water Interface under an Electric Field

2020

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Drop−interface interaction under an electric field is relevant in commercial desalters wherein water droplets suspended in oil coalesce under an electric field, move down under gravity, and eventually coalesce with the water pool at the bottom of the desalter. In this work, we report our observation that the transition from coalescence to partial coalescence can be described by a critical electrocapillary number and is independent of the Ohnesorge number. On the other hand, the partial coalescence to noncoalescence transition depends upon both the electrocapillary number and the Ohnesorge number. The bridge during partial coalescence exhibits an electrocapillary-number-independent growth and collapse dynamics, although the transition time for growth to collapse depends upon the electrocapillary number (Ca E ). Lastly, contrary to previous studies, our results indicate that the secondary droplet size varies as Ca E 3/2 unlike the Ca E 1/2 reported in the literature.

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Demulsification of crude oil emulsions tracked by pulsed field gradient NMR. Part II: Influence of chemical demulsifiers in external AC electric field

Cited by 29 publications

References 48 publications

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

Microfluidic Study of the Electrocoalescence of Aqueous Droplets in Crude Oil

Coalescence, Partial Coalescence, and Noncoalescence of an Aqueous Drop at an Oil–Water Interface under an Electric Field

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