Emulsions continued demulsifiers

In the production of crude oil, the greatest part of the crude oil occurs as a water-in-oil emulsion. The composition of the continuous phase depends on the water/oil ratio, the natural emulsifier systems contained in the oil, and the origin of the emulsion. The natural emulsifiers contained in crude oils have a complex chemical structure, so that, to overcome their effect, petroleum-emulsion demulsifiers must be selectively developed. As new oil fields are developed, and as the production conditions change at older fields, there is a constant need for demulsifiers that lead to a rapid separation into water and oil, as well as minimal-residual water and salt mixtures. 

The characteristic of the demulsifier to produce the Joining of droplets does not disrupt the continuity of the emulsifier film but just adds to It If the emulsifier has certain weaknesses, this flocculation force may be sufficient to cause complete resolution of the emulsion. However, in most cases further action Is necessary for the water droplets to unite and become large enough and free enough to settle ouL The action of uniting water drops is called coalescence. 

Chemical addition. Since the chemical must contact each stabilized water droplet in order to destabilize it, Che chemical should be applied so that it is thoroughly mixed with all of the emulsion. This can be accomplisned by batch treating, that is. mixing the demulsifier with a quantity of emulsion after it has been produced or by continuously injecting the dcmulsilier into the emulsion as it is being produced Mosi ofien continuous injection is used... 

Rag layers can be O/W or W/O, mayoften contain multiple emulsions (Figure 8.2), and can even be oil- and water-continuous in different parts of the same system [68]. Rag layers present the most challenging demulsification problems. They may require all of demulsifiers, elevated temperatures, and diluents. 

Demulsifying agents are usually added to the continuous phase and need to diffuse to the interface and displace, or otherwise destroy, the effectiveness of the original stabilizing agents at the interfaces. The demulsifier should usually be added far enough upstream to permit these actions to take place, and for droplet coalescence to occur, before the emulsion reaches a separating vessel. Demulsifiers are formu-... 

In some cases, minimal effort is required for the demulsification process. For example, in field tests, adequate separation of a bitumen emulsion could be achieved without the use of demulsifiers by raising the temperature of the emulsion to 190 T and providing 24 to 48 h of residence time in quiescent storage tanks. However, proper selection of demulsification chemicals is essential when treating the emulsions in conventional equipment on a continuous-flow basis. 

The second mode of CSTR operation is that used by Thien (17) and by Li and Shrier (10). Here, both the external phase and the LM emulsion are in a continuous flow mode. The reactor effluents are sent to gravity settlers where the exterior phase is separated from the emulsion phase. The emulsion phase is then demulsified to recover the product followed by remulsification and recycle back to the reactor. Hatton and Wardius (48) have developed the advancing front model for the analysis of such staged LM operations. Thien (17) employed this scheme to remove the amino acid L-phenylalanine from simulated fermentation broth (dilute aqueous solution). 

In both purification and recovery applications the ELM must be demulsified into two immiscible phases after the extraction step of the process. This is commonly accomplished by heating, application of electric fields ( ), or centrifugation. The liquid membrane phase containing the surfactant and carrier will be recycled to the emulsion preparation step while the Internal phase of the emulsion containing the concentrated solute will undergo further purification in a recovery process or treatment and disposal in a purification process. Such a continuous process is shown in Figure 2. 

In this paper the use of electroacoustic techniques involving the application of a sonic field and the detection of an electric field, for monitoring coalescence of water droplets in non-polar media will be discussed. This technique was used to evaluate the rate and extent of dewatering in oil continuous emulsions when surface active chemicals were added. The results showed that a combination of an oil soluble demulsifier and water soluble surfactant was substantially more effective in causing droplet coalesence than the individual components. An explanation for these findings were based on studies of time-dependent interfacial tensions at the oil/water interface and electrokinetic properties. The results indicated that a direct relationship exists between the adsorption behavior at the oil/water interface (apparent rate of spreading) and emulsion stability. 

Background. Demulsifiers are surface-active substances (surfactants) that have the ability to destabilize emulsions. In order to perform, a demulsifier must counteract the emulsifying agent stabilizing the emulsion, and promote aggregation and coalescence of the dispersed phase into large droplets that can settle out of the continuous phase [1-5, 8,9]. 

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