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Single-stage
separation by use of packed mass media is generally used for hydrocarbons
of lighter specific gravities and process streams where the removal
of water and solids is of vital importance.
Separation is first started when the liquid enters
the vessel. Due to the substantially reduced velocity, free water
starts to fall out by gravity. As it progresses through the mass
packed media, further separation occurs by impingement of the water
droplets on the media. At the same time, solids tend to fall out
as the liquid enters the vessel at reduced velocity but are further
removed by filtration as the flow continues through the mass media.
Settling zones permit a natural separation of water
due to the difference in the specific gravities of the two phases.
Mass packed coalescing media are available in various
styles and materials. Selection is based on the condition of the
liquid as to temperature, acidity and specific gravity. A second
criterion is the efficiency of water and solids removal desired.
Heavy solids or certain types of solids will tend to either blind
off the surface of the media and/or compress them to the point that
they will no longer function as a coalescer.
In the event solids are expected to be moderate to
heavy (in excess of 5 ppm), consideration should
be given to using the wafer type. This type permits change out of
the first or second upstream wafers,
which may contain a heavy load of solids, while the third and successive
downstream wafers are
relatively free of solids and still effective coalescers.
The outside diameter of all repacks is sized to the
inside diameter of the vessel. Thus, each repack
is personalized to the vessel. Further, densities will vary depending
upon the media used.
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