Oil Water Separation
Oil Water Separation
Oil Water Separation
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groups are
demulsifiers.
mainly
used
as
Water
at the bottom
emulsion
in
the
middle or below the water layer.
To break such a persistent emulsion, chemicals have to be applied.
A number of demulsifiers are
commercially available with varying degrees of performance and
selectivity. Generally, demulsifiers
are diluted with an organic solvent
and injected into crude oils. The
nature of the emulsion changes
from crude to crude, which can
influence the performance of the
emulsion breaker programme. This
necessitates the evaluation of cost
effectiveness and performance in
breaking the emulsion.
Persistent
PTQ Q2 2013 87
Agglomeration
Creaming
Coalescence
Creaming and
coalescence
Emulsion
88 PTQ Q2 2013
forces.
A
cationic
charged long-chain polymer
neutralises
the
negatively charged oil
droplets. The repellent
forces are weakened and
oil droplets are brought
together. This resolves
the emulsion of water
and oil. The emulsion-breaking
process
involves three steps:
Agglomeration
Creaming
Coalescence.
Figure 2 illustrates the physical
process of oil-in-water emulsion
breaking. Agglomeration is the
association of small dispersed
phase droplets (clusters). Creaming
is the concentration of the dispersed
phase. Coalescence is the drainage
of the continuous phase. The oil
droplets agglomerate by forming
bigger droplets and clusters, and
are collected at the surface. The
addition of an emulsion breaker
additive helps to accelerate the
separation process. These types of
emulsion breakers are surface
active components, which destabilise the dispersed phase.
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Wastewater treatment
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separation
and biological treatment
Filtration and polishing.
The main purpose of the primary
treatment is the separation of oil
and water. The removal of oil is a
very important step to reduce the
loading to the downstream treatment processes, because high oil
levels are toxic for the microorganisms used in biological treatment.
The wastewater typically contains
oil in water emulsions, with oil
dispersed in the continuous water
phase.
Common primary treatment units
are:
API oil/water separator
Corrugated
plate
interceptor
(CPI)
Dissolved air flotation (DAF)
Induced air flotation (IAF).
The function of an API oil/water
separator is based on the difference
in specific gravity of oil and water.
Suspended heavy particles settle to
the bottom of the separator to be
scraped by a rake into the sludge
pit, which is discharged continuously. The oil rises to the top of the
separator. The wastewater accumulates as a middle layer between the
settled solids and the oil phase. It
can be sent to a flotation unit for
further treatment. Substances such
as oil or particles can be separated
from water by flotation. Mechanical
flotation and dissolved air flotation
are applied to increase the flotating
velocity of particles. Fine air
bubbles are generated in water. The
upward flow of the bubbles and the
adhesion of bubbles with particles
Chemical
Conclusions
PTQ Q2 2013 89