Demulsification

Mechanisms involved in the demulsification by surfactants of petroleum W/O emulsions include adsorption of the surfactant at the oil-water interface and reduction of the interfacial tension, change in the nature of the interfacial film from a highly hydrophobic one to a less hydrophobic one (and, consequently, one more wettable by water), reduction of the viscosity of the interfacial film by penetration into it of the surfactant, and displacement of the original W/O emulsion stabilizers, particularly the asphaltenes, from the interface into the oil phase. 

Al-Rikabi, H. and J. S. Osoba, Paper presented at American Chemical Society meeting April 9, 1973, Dallas, TX. 

in Encyclopedia of Emulsion Technology, J. Sjoblom (Ed.), Marcel Dekker, New York, 2001, Chap. 24. 

Barette, D., Memoir de Licence, FUNDP, Namur, Belgium, 1992. 

Some emulsions are undesirable when they occur. In process industries chemical demulsification is commonly used to separate water from oil in order to produce a fluid suitable for further processing. The specific kind of emulsion treatment required can be highly variable, even within the same industry. The first step in systematic emulsion breaking is to characterize the emulsion in terms of its nature (O/W, W/O, or multiple emulsion), the number and nature of immiscible phases, the presence of a protective interfacial film around the droplets, and the sensitivity of the emulsifiers [295,408,451], Demulsification then involves two steps. First, there must be agglomeration or coagulation of droplets. Then, the agglomerated droplets must coalesce. Only after these two steps can complete phase separation occur. It should be realized that either step can be rate determining for the demulsification process. 

Sometimes an emulsion can be broken by changing the temperature or by applying mechanical shear. The temperature can be increased, for example, to cause crystalline or semi-crystalline components, such as paraffins, to melt, or to approach the 

If an emulsion is stabilized by electrical repulsive forces, then demulsification could be brought about by overcoming or reducing these forces. In this context the addition of electrolyte to an O/W emulsion could be used to achieve the critical coagulation concentration, in accord with the Schulze-Hardy rule. 

More commonly, demulsifiers are surface-active substances (surfactants) that have the ability to destabilize emulsions. This involves reducing the interfacial tension at the emulsion interface, often by neutralizing the effect of other surfactants that are stabilizing the emulsion. An example is antagonistic action - the addition of an O/W promoter to break a W/O emulsion (see sensitization in Section 5.4). Mikula 

Ideally, all of these actions happen quickly, resulting in the separation of the oil and water phases. 

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Entmischung, /. disintegration, etc. (see entmischen) (A/etof.) coring demulsification. entmutigen, v.t. discourage. 

Polyalkylene polyamides and other nonsilicone synthetic antifoams are particularly useful in controlling foaming problems. These chemicals also provide defoaming and demulsification benefits. 

Demineralization by ion-exchange as purification technology to reduce amine consumption as source of feedwater contamination Demineralization processes Demulsfier, for fuel oils Demulsification effect, of antifoams Demulsification, of fuel oils Denting... 

At the refinery, before distillation, the salt content is often further reduced by a second emulsification with freshwater, followed by demulsification. Crude oils with high salt contents could lead to breakdowns and corrosion at the refinery. The object of using an emulsion breaker, or demulsifier, is to break the emulsion at the lowest possible concentration and, with little or no additional consumption of heat, to bring about a complete separation of the water and reduce the salt content to a minimum. 

The polyoxyalkylene units in the copolymer have a molecular weight below 500, and the polysiloxane units have 3 to 50 silicon atoms. The resin has a phenol/aldehyde ratio of 2 1 to 1 5 and an average molecular weight of 500 to 20,000 Dalton. The composition shows synergistic demulsification activity when compared with the individual components. The siloxane units can be either in blocks [979,980] of the polyoxyalkylene-polysiloxane copolymer or randomly distributed [728,729]. 

Polyalkylene polyamine salts are prepared by contacting polyamines with organic or inorganic acids. The polyamines have a molecular weight of at least 1000 Dalton and ranging up to the limits of water solubility [1185]. In a process of demulsification of the aqueous phase of the broken bitumen emulsions, the pH is adjusted to deactivate the demulsifier so that the water may be used in subsequent in situ hot water or steam floods of the tar sand formation. 

A study on a commonly used demulsifier, namely, a phenol-formaldehyde resin, elucidated how various parameters such as interfacial tension, interfacial shear viscosity, dynamic interfacial-tension gradient, dilatational elasticity, and demulsifier clustering affect the demulsification effectiveness [1275]. 

R. S. Buriks, A. R. Fauke, and D. J. Poelker. Vinyl phenol polymers for demulsification of oil-in-water emulsions. Patent CA 2031122,1991. 

L. U. Castro. Demulsification treatment and removal of in-situ emulsion in heavy-oil reservoirs. In Proceedings Volume. SPE West Reg Mtg (Bakersfield, CA, 3/26-3/30), 2001. 

D. R. McCoy. Demulsification of bitumen emulsions using polyalkyl-ene polyamine salts. Patent CA 1220151,1987. 

S. Mukherjee and A. P. Kushnick. Effect of demulsifiers on interfacial properties governing crude oil demulsification. In Proceedings Volume. Annu AICHE Mtg (New York, 11/15-11/20), 1987. 

A. Sivakumar and M. Ramesh. Demulsification of oily waste waters using silicon containing polymers. Patent US 5560832, 1996. 

G. N. Taylor. Demulsification of water-in-oil emulsions using high molecular weight polyurethanes. Patent GB 2346378,2000. 

Demulsification Industrial Applications, Kenneth J. Lissant Surfactants in Textile Processing, Arved Datyner... 

Effect of Demulsifiers on Interfacial Properties Governing Crude Oil Demulsification... 

Although, many other methods (e.g. electrostatic separation, heating, centrifugation, etc.) may be used to separate the oil and water phases, chemical demulsification is the most inexpensive and widely used technique to resolve crude oil emulsions. The demulsifiers are oil-soluble water-dispersible non-ionic polymeric... 

Our goal is to develop a property-performance relationship for different types of demulsifiers. The important interfacial properties governing water-in-oil emulsion stability are shear viscosity, dynamic tension and dilational elasticity. We have studied the relative importance of these parameters in demulsification. In this paper, some of the results of our study are presented. In particular, we have found that to be effective, a demulsifier must lower the dynamic interfacial tension gradient and its ability to do so depends on the rate of unclustering of the ethylene oxide groups at the oil-water interface. 

Our results suggest that the lowering of interfacial shear viscosity, although necessary, is not a sufficient criterion for effective demulsification. In addition, a demulsifier must also rapidly dampen any fluctuations in the oil-water interfacial tension. 

The demulsification data with four different demulsifiers for a crude oil-water system (Table I) support this conclusion. Structurally, the demulsifier PI and R0 are of moderate (MW 2,000-5,000) molecular weights, whereas PI and P2 are large (MW >50,000) three dimensional structures. 

The results show that although all the demulsifiers lower the shear viscosity, they differ widely in their demulsification effectiveness, as measured by the residual bottom sediment and water content (Figure 1) (BS and W%) of the dehydrated oil. For example, the demulsifier 0P1, although it lowers both the equilibrium interfacial tension (Figure 2) and the shear viscosity (Table I), nevertheless is ineffective. This is because it takes a much longer time for the oil-water interfacial tension to reach equilibrium with 0P1 than with PI or P2 (see later). 

The importance of rapid relaxation in demulsification effectiveness can be seen with the crude oil-water dynamic tension results with P2 (Figure 3) and 0P1 (Figure 4). As can be seen, it takes only about 60 seconds for the interface to reach its equilibrium state with the effective demulsifier P2, whereas with less effective demulsifier 0P1, the equilibrium is reached only after 800 seconds. 

The shape of the curves for the dilational modulus (Figures 7 and 8) suggests a single relaxation mechanism, probably the unfolding of the demulsifier molecules at the interface. The frequency peak in the e"(f) plot is a measure of the characteristic relaxation time. A shorter relaxation time, by inducing faster film drainage, increases demulsification efficiency. 

The dynamic response data for PI and P2 (Figure 7) are similar. They are, however, quite different from that of 0P1 (Figure 8). The characteristic relaxation times for PI and P2 are 50 and 69 seconds respectively, whereas with 0P1 it is 158 seconds. This indicates that with PI and P2, the oil-water interface will have much shorter response time leading to an improved demulsification effectiveness. 

For effective demulsification of a water-in-oil emulsion, both shear viscosity as well as dynamic tension gradient of the water-oil interface have to be lowered. The interfacial dilational modulus data indicate that the interfacial relaxation process occurs faster with an effective demulsifier. The electron spin resonance with labeled demulsifiers suggests that demulsifiers form clusters in the bulk oil. The unclustering and rearrangement of the demulsifier at the interface may affect the interfacial relaxation process. 

DEMULSIFICATION TESTS. Demulsification tests were conducted using standard bottle test procedures to evaluate the relative performance of Thin Film Spreading Agents in coalescing emulsions of formation brine in crude oil under reservoir conditions. 

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