4) Age of emulsion Age of emulsion is generally increasing the emulsion stability. The ratio of emulsifying agents within oil may increase because of oxidation, photolysis, evaporation of light ends, or bacterial action. This is because light ends are low- molecular weight and low-density hydrocarbons such as pentane, hexane and butane that will vaporize xylene significantly over time. Breaking the emulsion as soon as possible after the emulsion formation will reduce the effects of ageing. 5) Control of emulsifying agents Emulsifying agents or surfactants are important in the emulsion formation process. The surfactants are either natural or synthetic. The elimination, alteration or neutralization of these materials allows the prevention or resolution of emulsions. Elimination of emulsifying agents may include corrosion inhibition programs to reduce the amount of iron sulfide, to avoid emulsification tendencies, or elimination of incompatible crude oils from crude oil blends. Alteration of emulsifying agents are includes the addition of an asphaltene dispersant to “tie up” asphaltene polar sites, addition of paraffin crystal modifiers to prevent large paraffin crystals from stabilizing emulsions, or by raising the treating temperatures above the paraffin cloud point of a crude oil. Neutralization of emulsifying agents such as by neutralization of polar charges associated with the film of emulsifying agents formed around the emulsified droplets. Neutralization is the function carried out by commercial demulsifiers or coagulants that promote coalescence and thereby accelerate by gravity settling.
18 6) Agitation control Emulsion stability will be reduced by reducing or eliminating the agitation of oil-and- water mixture. The effectiveness of any demulsifier added to treatment system is directly dependent upon it making optimum contact with the emulsion. Therefore, the emulsion must be sufficiently agitated after the chemical demulsifier has been added. Increase of the mild agitation, is beneficial in promoting coalescence. Re- emulsification may occur if an emulsion is agitated severely once it has broken into oil and water. 2.2.4 Mechanisms of demulsification process Chemical demulsification is a dynamic process since it is a phenomenon that occurs under non-equilibrium conditions. Coalescence of the dispersed phase often happens before the interface is at equilibrium. Therefore, it is paramount to consider dynamic and dilatational properties in the analysis of the demulsification mechanism. An important feature of dispersants is the ability to break water-in-oil emulsions that form naturally as the oil slick weathers and tosses about on the sea surface. Recent laboratory and field experience have demonstrated the ability of some dispersants to break emulsions formed at sea, particularly before the extremely viscous and stable ‘mousse’ stage of emulsion forms. This demulsification activity promotes coalescence of the water droplets in the emulsion, which in turn causes separation of water and lowering of viscosity.
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