Abstract
An oscillatory emulsification system for the production of oil in water emulsions using a commercially available low-cost woven metal microscreen (WMMS) is investigated. The system allows for independent control of both the oscillation frequencies and amplitudes such that it provides two degrees of freedom for controlling the emulsion properties. The investigations included the production of both surfactant and particle-stabilized emulsions. The average droplet size was found to decrease when both the oscillation frequency and amplitude was increased. For surfactant-stabilized emulsions, using bi-surfactants in both the continuous and dispersed phases resulted in a smaller droplet size due to lower interfacial tension. For particle-stabilized emulsions, both the hydrodynamics of the system and the hydrophobic and hydrophilic nature of the stabilizing particles influenced the interfacial properties at the oil–water interface, which in turn affected the final droplet size and distribution with potential droplet breakage. In absence of the latter, a simple torque balance model can be used to reasonably predict the average emulsion droplet size.
Highlights
Emulsification is an important unit operation in many industries such as pharmaceuticals, food, cosmetics, and fuel applications
The experimental setup consisted of a rectangular container filled with the continuous phase and two stainless steel woven metal microscreens (WMMS’s) with a 38-μm pore size and 36% porosity housed on both sides of a flat surface frame that oscillated vertically using an adjustable eccentric to provide a wide range of oscillatory frequencies and amplitudes (f = 0–25 Hz and a = 0–22 mm)
Increasing the dispersed phase flow resulted in an increase in droplet size, and the effect became became weaker at higher fluxes and as the oscillatory shear increased
Summary
Emulsification is an important unit operation in many industries such as pharmaceuticals, food, cosmetics, and fuel applications. It involves dispersing one immiscible liquid into another using equipment such as high-pressure homogenization or colloid mills. These high shear systems typically require high energy that partially dissipates in the form of heat with potential negative impact on product functional properties and the process energy efficiency. Among the approaches proposed to overcome such limitations is emulsification using membranes or microsieves [1,2] In this technique, pressure is applied to force one phase to permeate into another to produce an emulsion. Droplet detachment in this case is basically induced when the shear force exerted by the continuous phase exceeds the capillary force holding the droplets to the membrane pores
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