Emulsions demulsification

In many instances it is the breaking of an emulsion (demulsification) which is of practical importance. Examples are the creaming, breaking and inversion of milk to obtain butter, and the breaking of W/O oil-field emulsions. Small amounts of water often get emulsified in lubricating oils, hydraulic oils and heat-exchange systems, and it is necessary to remove this water to prevent corrosion and other undesirable effects. 

Deming, W. Edwards See Japanese workmanship, demulsification See emulsion/demulsification. demurrage See cost, demurrage, dendritic plastic A highly branched (dendritic) precursor of synthetic plastics that lead to three-dimensional gels and networks. These systems are broadly recognized as thermoset plastics. See gel. 

AMPHOSOL AT-2 STEPANATE AT-2 detergent, petroleum oil emulsion demulsification Tergitol 15-S-20 detergent, petroleum oils Cetoleth-2 Cetoleth-3 Cetoleth-6 Non-oxynol-4 Nonoxynol-5 Rhodasurf BC-420 Serdox NES 3 Serdox NOL 2 Surfonic N-40 T-Det N-1.5 T-Det N-6 Teric N4 Teric N5 detergent, petroleum processing equip. 

Aromox C/12 Aromox C/12-W wetting agent, petroleum extraction Silwet L-7602 Siwel L-7607 wetting agent, petroleum oil emulsion demulsification Tergitol 15-S-20... 

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. 

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. 

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. 

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

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. 

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. 

Although the emulsions were expected to be stabilized with increasing surfactant concentration, the degree of stability beyond a critical surfactant concentration becomes approximately constant due to the saturation of the surfactants at the oil-water interface. Again, higher concentration of surfactant will hinder demulsification after extraction. So a critical surfactant concentration value should be used for practical purposes. 

Two principal approaches for the demulsification of the loaded emulsion are chemical and physical treatments. Chemical treatment involves the addition of a demulsifier to the emulsion. This method seems to be very effective. However, the added demulsifier will change the properties of the membrane phase and thus inhibits its reuse. In addition, the recovery of the demulsifier by distillation is rather expensive. Therefore, chemical treatment is usually not suitable for breaking emulsion liquid membrane, although few examples of chemical demulsification have been reported for certain liquid membrane systems [88]. 

Demulsification with electrostatic fields appears to be the most effective and economic way for breaking of W/0 emulsion in ELM processes 190, 91]. Electrostatic coalescence is a technique widely used to separate dispersed aqueous droplets from nonconducting oils. Since this type of technique is strictly a physical process, it is most suitable for breaking emulsion liquid membranes to recover the oil membrane phase for reuse. 

The process of demulsification usually involves removal or dropout of relatively large volumes of water which have contaminated fuel. The amount of water in this circumstance is usually >1% of the total fuel volume. Also, when an emulsion has been created in a fuel, breaking this emulsion is termed demulsification. Sometimes, the term emulsion breaking is also used to describe the process of demulsification. 

Macroemulsions tend to separate into two phases. This is called demulsification. Demul-sification can be very slow so that even a macroemulsion might appear stable. Often macroemulsions are just called emulsions because all classical dispersions of oil and water were macroemulsions. In this section we use the term emulsion if it concerns a property of macro- and microemulsions. If we discuss the properties primarily of macroemulsions we use the full term. From the practical point of view micro- and macroemulsions are very different. That we discuss some properties together should not hide this fact. 

Freshly prepared macroemulsions change their properties with time. The time scale can vary from seconds (then it might not even be appropriate to talk about an emulsion) to many years. To understand the evolution of emulsions we have to take different effects into account. First, any reduction of the surface tension reduces the driving force of coalescence and stabilizes emulsions. Second, repulsive interfacial film and interdroplet forces can prevent droplet coalescence and delay demulsification. Here, all those forces discussed in Section 6.5.3 are relevant. Third, dynamic effects such as the diffusion of surfactants into and out of the interface can have a drastic effect. 

Most emulsions are not thermodynamically stable, but as a practical matter, quite stable emulsions can occur that resist demulsification treatments and may be stable for weeks/months/years. Most meta-stable emulsions that will be encountered in practice contain oil, water and an emulsifying agent (or stabilizer) which is usually a surfactant, a macromolecule, or finely divided solids. The emulsifier may be needed... 

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. 

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