NEUTRALISATION
The
edible oils permitted for manufacturing Vanaspati contain
certain percentage of free fatty acids (FFA), gums and other
impurities with FFA, varying between 0.5% to 5%. To remove
the FFA and other impurities, the oil is first treated with
Phosphoric Acid to remove Phosphatides and then with caustic
soda solution to neutralise the free fatty acids into a soap
stock. The soap stock so formed is removed either by allowing
it to settle in a batch process or by centrifugal force in
continuous process. To remove all the soapy matters hot water
wash is further given to the oil under constant agitation
in the vessel. The washed Water being heavier settles down
and is removed from the bottom in batch process and by centrifuge
in continuous process.
BLEACHING
Oil
so obtained after neutralising and washing is taken in a bleaching
vessel where the oil is first dried by heating under vacuum
at temperature of 100 degree centigrade and then bleached
by adding earth and activated carbon to remove its colour.
At the end of bleaching process the oil is filtered in filter
press to remove the spent bleaching earth and carbon. The
cleaned oil so received after bleaching is taken into autoclave
for hydrogenation.
HYDROGENATION
The oil is first heated with the help of
steam in coils and then spent nickel catalyst is fed into
the process. Since, most of the oils used for Vanaspati manufacture
are unsaturated, they consume hydrogen gas which is passed
through the oil at that temperature in the presence of nickel
catalyst and thus the melting point of the oil rises. Fresh
quantity of nickel catalyst is added into the process, the
quantity depends upon the type of oil. When desired melting
point of oil is obtained, the supply of hydrogen gas to the
process is stopped. Then the hydrogenated nickel catalyst
mixed oil is first cooled from 200oC and then it is filtered
through a filter press. Some time for easy filtration filter
aid is also added.
HYDROGEN GAS GENERATION
Hydrogen is manufactured by electrolytic
process by passing free current through dilute aqueous sol.
of alkali, thereby decomposing the water according to following
equation. 2H20à2H2+O2 The hydrogen produced is tested for
purity and collected in gas holders. The gas is compressed
by Hydrogen gas compressor and taken in autoclaves through
pipeline and storage vessels after reducing its pressure to
20-30 PSI for the purpose of Hydrogenation. The oxygen is
purified, compressed and filled into cylinders.
POST TREATMENT
After hydrogenation, the oil is taken for
post treatment to remove any undesired FFA if developed during
the process and also to remove nickel catalyst left with the
help of either very diluted caustic soda solution or with
hot water as found suitable at that time. The neutralising,
washing and bleaching process will be repeated in the same
manner as were carried out for soft oil.
DEODORISATION
