Emulsion Treating Theory

When selecting a treating system, several factors should be considered to determine the most desirable method of treating the crude oil to contract requirements. Some of these factors are  

Corrosiveness of the crude oil, produced water, and associated gas. Scaling tendencies of the produced water. 

Quantity of fluid to be treated and percent water in the fluid. Paraffin-forming tendencies of the crude oil. 

Availability of a sales outlet and value of the associated gas produced. 

Laboratory analysis, in conjunction with field experience, should be the basis for specifying the configuration of treating vessels. 

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The remainder of this review treats the preponderance of work in mass/solution processes. As shown in Table II, relatively little has been done with suspension and emulsion polymerization theory, particularly with continuous reactors. It is worthwhile to highlight some of this work. 

The conductivity of a dilute emulsion can be treated by classic theory (see Maxwell [6]) assuming spherical droplets... 

Although the remainder of this contribution will discuss suspensions only, much of the theory and experimental approaches are applicable to emulsions as well (see [2] for a review). Some other colloidal systems are treated elsewhere in this volume. Polymer solutions are an important class—see section C2.1. For surfactant micelles, see section C2.3. The special properties of certain particles at the lower end of the colloidal size range are discussed in section C2.17. 

The electrical conductivity of dilute emulsions can be treated by classical electrodynamic theory and the conductivity is given by... 

Then mesoscopic aspects are treated. Chapter 9 gives a general introduction on disperse or particulate systems. It concerns properties that originate from the division of a material over different compartments, and from the presence of a large phase surface. Two chapters give basic theory. Chapter 10 is on surface phenomena, where the forces involved primarily act in the direction of the surface. Chapter 12 treats colloidal interactions, which primarily act in a direction perpendicular to the surface. Two chapters are concerned with application of these basic aspects in disperse systems Chapter 11 with emulsion and foam formation, Chapter 13 with the various instabilities encountered in the various dispersions foams, emulsions, and suspensions. 

An important variation of the model of Mickley and Fairbanks is the film penetration model developed by Yoshida et al. [48] by treating packets as a continuum with a finite thickness (8em). The film penetration theory includes two extremes of emulsion behavior. On one extreme, the packet contacts the heating surface for a short time so that all the heat entering the packet is used to heat up the packet (penetration theory) while none passes through it. On the other extreme, the packet stays at the surface long enough to achieve steady state and simply provides a resistance for heat conduction. 

The stability of suspensions containing solid particles are treated in the framework of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which accounts for the electrostatic and van der Waals interactions between the particles (Verwey and Overbeek 1948, Derjaguin 1989). In the past decades it has been shown that other types of inter-particle forces may also play an important role in the stability of dispersions - hydrodynamic interactions, hydration and hydrophobic forces, steric and depletion forces, oscillatory structural forces, etc. The hydrodynamic and molecular interactions between surfaces of drops and bubbles in emulsion and foam systems (compared to that of suspensions of solid particles) are more complex due to the particles fluidity and deformability. These two features and the possible thin film formation between the colliding particles have a great impact on the hydrodynamic interactions, the magnitude of the disjoining pressure and on the dynamic and thermodynamic stability of such systems (Ivanov and Dimitrov 1988, Danov et al. 2001, Kralchevsky et al. 2002). 

The degree of stability of many dispersions cannot be explained solely on the basis of Fa and Fr. Elworthy and Florence [56] have treated the stability of emulsions of chlorobenzene and anisole stabilized with a series of synthetic polyoxyethylene ethers in the light of colloid theory and have shown that electrical stabilization alone cannot explain the stability observed. The nature of this other force which is invoked to explain discrepancies between theory and experiment is not fully worked out. Nevertheless, much interest has been shown in this alternative mechanism of stabilization, which for non-ionic emulsions appears to play the major role [64]. Results have indicated that the thickness and degree of solvation of adsorbed layers is critical [65]. Thus, the particular conformation and length of the polyoxyethylene chains of non-ionic surfactants at interfaces is likely to be an important factor in the stabilization of emulsified droplets. 

Recently, Durant et al. [55] developed a mechanistic model based on the classic Smith-Ewart theory [48] for the two-phase emulsion polymerization kinetics. This model, which takes into consideration complete kinetic events associated with free radicals, provides a delicate procedure to calculate the polymerization rate for latex particles with two distinct polymer phases. It allows the calculation of the average number of free radicals for each polymer phase and collapses to the correct solutions when applied to single-phase latex particles. Several examples were described for latex particles with core-shell, inverted core-shell, and hemispherical structures, in which the polymer glass transition temperature, monomer concentration and free radical entry rate were varied. This work illustrates the important fact that morphology development and polymerization kinetics are coupled processes and need to be treated simultaneously in order to develop a more realistic model for two-phase emulsion polymerization systems. More efforts are required to advance our knowledge in this research field. 

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