MIL-HDBK-1005/9A
a) Chemical Treatment. This is usually carried out in
smaller tanks (1,000 to 5,000 bbls) that provide heat. The
demulsifier is transfer injected into the waste stream via a
metering pump to ensure adequate mixing and proper dosage. The
heat required is generally between 145F and 165 F (62.8C and
73.9C) and may be provided with steam heating coils in the
settling tank. The waste stream may be heated before demulsifier
addition if convenient. A reclamation facility will typically
have two holding tanks. The oil settles in one tank while it is
collected in the other. Depending on the size of tank used, 3 to
7 days are required for optimum resolution of the emulsion. After
settling, the bottom water is drawn off and returned to the LET
for reprocessing. Figure 26 shows the treatment of an oil
emulsion in a batch process. For more information on the
selection and application of a demulsifier, refer to paragraph
3.10.9.2.
b) Filtration. In filtration (precoat), the emulsion
is filtered through a layer of diatomaceous earth, normally
deposited on a continuously rotating drum filter. Precoat
filtration is not normally recommended because of its high
operating costs. For additional details, refer to the API Manual.
3.10.9.2 Demulsifier Selection and Application. Given the
complexity and diversity of emulsions, an emulsion breaker is
expected to perform many tasks. Ideally, a demulsifier should
provide a rapid water break, clean oil that meets reuse
specifications, a sharp interface and clear, oil-free water.
Based on the above functions, no single-component
chemical can do these jobs effectively. The different surface
phenomena that occur in three different phases can only be
addressed by a multi-component demulsifier. Therefore, when
formulating a demulsifier, one has to consider incorporating a
range of solubilities, surface activities, and wetting properties.
An effective demulsifier may consist of two, three, or
four components, preselected and blended in a specific order and
in carefully controlled proportions.
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