Page 55 - 5010

on the presence of surfactants in these liquids (mainly in oil).
According to the rules oil, taken for refining from the field, has to

contain less than 2 % of water and mud. The amount of water and

mud in oil at the exact (proper) measurements is determined as a rule
by means of Dean-Stark apparatus.

Therefore destruction of emulsions (demulsification) is one of
the most important processes of oil treatment in the field.
There are two types of emulsions – hydrophilic and hydrophobic.

The emulsion of hydrophilic type is the following one: in large

volume of water (dispersible environment) very small (dispersible)
drops of oil are dissipated. As a rule oil constitutes approximately 2 –

3 % of the volume of emulsion of this type. Hydrophilic emulsion

looks like rusty water and often can be met in waste waters.

The emulsion of hydrophobic type is the following one: drops of

water are in a bulk of oil. Crude oil, especially dense, heavy oil, oil

with big amount of resins contains such colloidally soluble in one of
phases “stabilizers” or “emulsifiers” (for example, naphthenic acids,
asphaltenes, resins) which forming the protective shell on the surface
of drops prevent their direct connection and thus prevent the rapid

segregation of liquids.
The following methods are used for destruction of emulsions

(demulsification): gravitational method; gravitational and thermal;

chemical; electric; mechanical and combined methods.
1. Gravitational method. It is the most simple method for
destruction of emulsions. This method is based on the difference of

densities of oil and water. It is often used in oil fields (water settling
in tanks). But the difference in densities of liquids is small and
therefore this process is very long.

2. Gravitational and thermal method. This method consists in
the following: heating reduces liquid viscosity and mobility of liquids
increases. Therefore the process of their segregation is accelerated. To
avoid evaporation of light, the most valuable fractions of oil, the

mixture (emulsion) is heated in tanks or other capacities to the
temperature not higher 50 °С. In special hermetic demulsification
installations oil is heated to 100 °С and higher. After heating the

mixture has to be settled.
3. Chemical method. It consists in adding reagents (demulsifiers)

54