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

Abstract

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.

Simulation investigation of the spontaneous motion behaviors of underwater oil droplets on a conical surface

“…The phase-field method has been widely proven as an ideal approach for tracking the diffusive interface between two immiscible phases because it is based on thermodynamic theory and the total energy of the system tends to be minimized over the simulation process. [24][25][26] In this simulation model, a dimensionless phase-field variable f(x) is used to characterize two phases (oil and water), where x is the position vector. f o = f(x) = 1 represents the oil phase; f w = f(x) = À1 represents the water phase; the diffusive interface between oil and water phases is represented by the region with À1 o f(x) o 1.…”

Effect of liquid volume fraction and shear rate on rheological properties and microstructure formation in ternary particle/oil/water dispersion systems under shear flow: two-dimensional direct numerical simulation

“…The details of the modelling of interfacial flows are available in our previous papers. [34][35][36][37]…”

Numerical simulation of droplet dispersion within meso-porous membranes

“…However, such studies reach certain limits in terms of resolvable pore sizes and time scales [8]. To assist in this effort and to provide deeper insight into liquid membrane processes, numerical simulations of liquid filtration and emulsification using various numerical methods from phase field [9][10][11] to level set and volume of fluid (VoF) [12][13][14] as well as lattice Boltzmann (LB) [15][16][17] have been utilized [18][19][20]. All these studies have, in one way or another, through their specific approach, tackled the subject of wettability in membrane processes.…”