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2.1.2 Physical and chemical conditions of reception of return emulsions

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Reception of the return emulsions meeting the resulted requirements, represents very much a challenge.

In the course of dispersed phase emulsification in a dispersion medium two opposite processes simultaneously proceed: dispergation and coalescence (merge of drops among themselves).

According to P.A.Rebindera's views process of dispergation of an internal phase at reception of emulsions consists that at significant speeds of a turbulent mode of a current the big spherical drops distort and get the form tsilindrikov. At some critical sizes tsilindriki spontaneously break up to the big and small drops, that termodinamicheski it is favourable. This process is retried until the big drop becomes equal small. During the certain moment of time there comes equilibrium process of merge and crushing of drops. To such condition and sootvejutvuet an emulsion condition.

If balance will move towards dispergation it is formed more or less steady emulsion. Drops can be formed and without introduction in system of PEAHENS. However even any one type of an emulsion will prevail thus. So, Bankroft in the beginning of the last century explained reception of a direct or return emulsion from positions of interfacial tension of their phases. For example, if interfacial tension of water is less, than at oil the direct emulsion (fig. 3.2,) and on the contrary (fig. 3.2,6) is formed. As interfacial tension of water alone always is more than interfacial tension of hydrocarbons at their mixing its emulsification as a part of hydrocarbons will prevail, i.e. a return emulsion.

Fig. 2.2. The schema of formation of emulsions (it agree Bankroftu) Process of stabilisation of formed globules of a dispersed phase and reception of certain type of an emulsion is connected with a solubility kind (vodo or oil-soluble), chemical constitution, concentration of PEAHENS, and also with a number of other physical and chemical parametres which play the subordinated role. For example, fractional wettability of a surface of a solid body of one of emulsion phases (presence of a hydrophobic surface is preferable to an emulsion v/m), density and viscosity, a parity of volumes of phases, etc.

Specific surface of dispersed phase Sya in an emulsion increases with increase in a difference of density of phases in view of acceleration of movement of drops in a power stream with their subsequent deformation and disintegration on smaller. It is experimentally positioned, that Sya it is proportional to speed of a mechanical stirrer (i.e. put energy) and uvelichivaetsja'pri increase of density and viscosity of a dispersion medium, concentration of a dispersed phase. At the same time growth of viscosity of a dispersed phase reduces efficiency of emulsification that follows from the fact of increase in cohesion of its molecules among themselves and increases in energo-expenses at dispergation of drops of a high-viscosity phase of an emulsion.

With a view of simplification of process of formation of a return emulsion it is necessary to achieve gradual input of an aqueous phase in the hydrocarbonaceous environment with emulsifying agent preliminarily dissolved in it. At possibility of chemical formation of emulsifying agent as a part of adsorption layer (a method "in situ") it is necessary to prefer this method.

The temperature increase at emulsification, on the one hand, promotes decrease in interfacial energy, viscosity of phases, but, with another,

Accelerates process of the subsequent merge of drops among themselves because of destruction of a blanket of emulsifying agent. According to V.G.Benkovskogo and to researches of authors [46], for preparation of return emulsions, for example, with use as an oil dispersion medium, the temperature ~20°С is most comprehensible. High degree of stability and efficiency of return emulsions for conditions of many oil deposits possessing similar fiziko-geological and technogenic properties is marked.

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A source: Kozhabergenov Murat Mokanovich. Substantiation of effective technologies doizvlechenija residual oil from obvodnennyh layers on an example of XIII horizon of deposit Uzen: Dis.... A Cand.Tech.Sci.: 25.00.17. - M: RGB, 2006. 2006

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