GrasasYaceites 1-57. pdf

8. LIQUID-LIQUID PHASES SEPARATION
Oil from decanters has between 1 and 3% waste
water and waste water from three way system
(alpechín) has an oil content in the range of 0.5-2%.
Both have to be cleaned. After liquids are sieved, the
separation of liquid phases with different density is
performed by natural decantation (hardly used at
present) or by vertical centrifuges. These centrifuges
are formed by a double truncoconical shaped bowl
GRASAS Y ACEITES
, 57 (1), 
ENERO
-
MARZO
, 25-31, 2006, 
ISSN
: 0017-3495
29
OLIVE OIL EXTRACTION AND QUALITY
Figure 2
Longitudinal section for two and three way centrifugation
systems.
Figure 3
Cross section for two and three way centrifugation systems.
Figure 4
Schemes of continuous extraction systems

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and a pool of plates inside that rotate at the same
time at 6000-7000 rpm. The liquids are loaded on
the top through a hollow axis which leads to a
deflector where they are partitioned. Then they are
introduced among the plates that work as elemental
centrifuges separating the different phases:
• Solids are located in the higher radius
• Waste water remains in an intermediate radius 
• Oil is in the lower radius
When working, the centrifuge inside is full of
liquid, thus the liquid phases are located in their
respective rings. Oil rises next to the central axis
flowing through holes in the rotation axis. However
the wastewater is projected from the plates to an
outlet in the external wall of the bowl. Solids remain
where the double truncoconical parts of the bowl
are united which is the larger distance to rotation
axis.
Vertical centrifuge can be used for oil cleaning or
to extract the oil from alpechín, the difference is the
alpechín outlet, which can be regulated by a
regulation ring. As the regulation ring is higher the
alpechín outlet will be grater (its oil content will be
higher), it produces a movement of the hydraulic
ring to the external part of the bowl, then the oil is
cleaner. This is the aim of vertical centrifuges for oil,
however those for alpechín, is to obtain the lesser
oil content in the waste water and thus, the
regulation ring will be smaller. The hydraulic ring is
moved to the rotation axis and then, the oil will
appear dirty.
In vertical centrifuges for oil some warm water
has to be added to increase the thickness of the
alpechín phase. Water affects the oil characteristics,
for higher water amount oil phenol content
decreases and for warmer water a decrease in
phenols and aroma compounds has been
observed.