prepared material is received into the OILTEK Extractor by an OILTEK
Conveyor via an OILTEK Air seal in the raw material receiver section, which
has an arrangement for controlling the level of material received by the
The design of OILTEK Extractor is such that its speed is adjusted
automatically depending upon the capacity being processed by means of level
controllers coupled with variable frequency drive to its motor.
The Extractor chamber consists of a number of solvent sprayers which in
uniform, sprays the solvent over the entire bed of raw material. The length
and breadth is designed to give sufficient time for intimate contact,
penetration and percolation of solvent into raw material. The Extractor is
also designed with light and sight viewing glasses to view the spray
The material coming out of the spraying chamber is de-oiled material with
solvent which is to be recovered in the Desolventising section where it is
transported by means of a special OILTEK Solvent Seal Conveyor . The mixture
of the oil and solvent called Miscella is collected in the
Miscella tank from where it is pumped to distillation section.
The de-oiled meal contains about 20% - 35% solvent by weight depending on
the material. The meal must be desolventised.
The basic principal involved in Desolventation is direct heating of
material with steam to a temperature well above boiling point of the solvent
and thus ensuring no solvent is left over in the material. Toasting is also
heating the material with direct and indirect steam to remove the remaining
hexane and as well toast the meal.
Vapours of solvent are then sent to OILTEK Condensers via OILTEK Scrubber
where the solvent vapour is washed, and particulars of fines are not carried
to the condensers.
The OILTEK Air seals are provided at inlet and outlet of OILTEK
Desolventisers to ensure an air tight arrangement. This is essential to keep
the solvent loss figure down. The de-oiled and de-solventised meal thus
obtained is then transported to Bagging Section.
Veendeep takes great care in designing and sizing the Desolventiser as to
minimize the steam and power consumption.
Mixture of oil and solvent obtained in the OILTEK Extractor is known as miscella
and it normally contains 12%-35% depending on the material used. During
distillation, solvent evaporates first due to its low boiling point (64 to
67 deg C) thus leaving clean oil behind.
Distillation is performed in three stages under vacuum to ensure that no
oxygen is present when the oil is heated to a high temperature.
Presence of Oxygen will exercise the oil, making it unsuitable. First
evaporation takes place in Economizer and concentrates in the Evaporator,
Pre Heater and Final Heater. After each step of evaporation the oil passes
through Oil Vapour Separator, which separates the evaporated vapour leaving
practically only oil behind. This oil is further treated with open steam in
OILTEK Stripper and then finally dried in OILTEK Drier to ensure that no
solvent finds its way along with the oil. The oil is finally cooled in
OILTEK Oil Cooler to below 60° C before sending it to storage.
The solvent vapours thus produced by passing through OILTEK Oil Vapor
Separator to separate out any oil particles trapped with solvent vapors and
are then passed on to OILTEK Condenser for condensation.
Solvent vapours are formed both in Desolventisation Section as well as in
Distillation Section and these are to be condensed. Special floating head
type OILTEK Condensers are provided. The floating head type OILTEK
Condensers help in quick and easy removal of tubular bundles for periodical
cleaning. Adequate surface area have been provided for OILTEK condensers for
complete condensation of solvent vapour.
Final Solvent Recovery
In spite of providing adequate Condensers, the air that is being injected
out of the system contains traces of solvent. In order to recover the
traces, a special final vent air stripping column has been provided. It
comprises of a main OILTEK Absorber to give a large surface of contact. It
is partly filled with mineral oil which is a suitable absorbing media that
absorbs the solvent vapours from the air. The oil and solvent mixture is
stripped to recover the solvent.