Emulsions continued water droplets size

A portion of the water in an emulsion can be dispersed within the oil droplets. This portion of the total water should be treated as oil when estimating emulsion viscosity. Generally, added water is present in the continuous phase. If the crude oil contains water prior to emulsion formation, this water may be present in either the continuous (water) phase or the dispersed (oil) phase after emulsion formation, depending primarily on the water droplet size in the crude oil. In order to predict how much of the water in the crude oil will be freed into the continuous phase, emulsion preparation experiments with the actual crude oil to be used are necessary. 

Bowcott, J.E. and Schulman, J.H.(1955) Emulsions -control of droplet size and phase continuity in transparent oil-water dispersions stabilized with soap and alcohol. Z. Elektrochem., 59, 283. 

The objective of this paper is to illustrate the efficacy of inferring the interdroplet forces in a concentrated protein stabilized oil-in-water emulsion from the knowledge of the equilibrium profile of continuous phase liquid holdup (or, dispersed phase faction) when the emulsion is subjected to a centrifugal force field. This is accomplished by demonstrating the sensitivity of continuous phase liquid holdup profile for concentrated oil-in-water emulsions of different interdroplet forces. A Mef discussion of the structure of concentrated oil-in-water emulsion is presented in the next section. A model for centrifugal stability of concentrated emulsion is presented in the subsequent section. This is followed by the simulation of continuous phase liquid holdup profiles for concentrated oil-in-water emulsions for different centrifugal accelerations, protein concentrations, droplet sizes, pH, ionic strengths and the nature of protein-solvent interactions. 

Oil and emulsion t low through a spreader into (lie back, or coalescing, section ot the vessel that is lluid packed. Tlic spreader distributes flow evenly throughout the length ol this section Treated oil is collected at the top by means of a collection device sized to maintain a uniform vertical oil flow Coalescing water droplets fall countercurrent to the rising oil continuous phase. The oil-water interface is maintained by a level controller and dump valve for this section of the vessel. 

The effect of the viscosity of the continuous phase was studied theoretically in o/w emulsions containing water-soluble stabilizers and also in w/o emulsions of various oils [32]. In the former, droplets were larger in the absence of a stabilizer than in its presence. However, there was no clear-cut correlation of the viscosity of the continuous phase with droplet size. This can be ascribed to the increased amount of energy dissipated in the immediate vicinity of the droplets relative to the bulk liquid, which may result in more efficient disruption than if the energy dissipation occurs evenly throughout the continuous phase. The addition of a stabiiizer possibly alters and partly suppresses cavitation in the bulk liquid, the cavitation threshoid and viscosity being related similarly as in pure liquids [58]. The energy may subsequently dissipate preferentially at the surface of droplets and result in more efficient use in terms of droplet disruption. 

To develop an understanding of the emulsion flow in porous media, it is useful to consider differences and similarities between the flow of an OAV emulsion and simultaneous flow of oil and water in a porous medium. As discussed in the preceding section, in simultaneous flow of oil and water, both fluid phases are likely to occupy continuous, and to a large extent, separate networks of flow channels. Assuming the porous medium to be water-wet, the oil phase becomes discontinuous only at the residual saturation of oil, where the oil ceases to flow. Even at its residual saturation, the oil may remain continuous on a scale much larger than pores. In the flow of an OAV emulsion, the oil exists as tiny dispersed droplets that are comparable in size to pore sizes. Therefore, the oil and water are much more likely to occupy the same flow channels. Consequently, at the same water saturation the relative permeabilities to water and oil are likely to be quite different in emulsion flow. In normal flow of oil and water, oil droplets or ganglia become trapped in the porous medium by the process of snap-off of oil filament at pore throats (8). In the flow of an OAV emulsion, an oil droplet is likely to become trapped by the mechanism of straining capture at a pore throat smaller than the drop. 

A new method for droplet size measurement, using a bench-top pulsed-field-gradient NMR spectrometer operating in the time domain, has been reported (18). The continuous water phase is successfully suppressed by gradient pulses in order to measure the dispersed oil phase. Simulations show that for most common oil/water food emulsions the influence of droplet diffusion is negligible due to a rather large droplet size or a high viscosity of the continuous water phase. 

Emulsions are characterized in terms of dispersed / continuous phase, phase volume ratio, droplet size distribution, viscosity, and stability. The dispersed phase is present in the form of microscopic droplets which are surrounded by the continuous phase both water-in-oil (w/o) and oil-inwater (o/w) emulsions can be formed. The typical size range for dispersed droplets which are classified as emulsions is from 0.25 to 25 p (6). Particles larger than 25 p indicate incomplete emulsification and/or impending breakage of the emulsion. Phase volume ratio is the volume fraction of the emulsion occupied by the internal (dispersed) phase, expressed as a percent or decimal number. Emulsion viscosity is determined by the viscosity of the continuous phase (solvent and surfactants), the phase volume ratio, and the particle size (6). Stroeve and Varanasi (7) have shown that emulsion viscosity is a critical factor in LM stability. Stability of... 

In emulsion and suspension polymerizations, the continuous water phase serves as an excellent conductor of heat and allows the heat to be removed from the system (Figure 9.8). Therefore, the polymerization can be conducted at a high rate. This is a kind of flash chemistry without using micro devices. Instead, the reaction is carried out in small size droplets. The high surface-to-volume ratio of droplets is responsible for the fast heat transfer. 

---