The efficiency of Neutralising operation is determined
by the least possible loss of Neutral oil in soap stock.
As such, in this operation the quantity of original oil
is reduced by its free fatty acid content plus quantity
of neutral Oil in soap stock plus impurities. The constitutes
refining loss or neutralising loss and is generally two
to two and half times the free fatty acid content of the
oil. After draining of the soap stock the oil which is
now free from fatty acids and impurities is washed repeatedly
with hot water to free it from any caustic soda and soap.
These dissolve in the wash water, which is drained from
the bottom after settling. Neutralisation also removes
bulk of the colour of the Crude Oil and makes it lighter.
Gum
Conditioning & Neutralisation
The phosphatide portion of oil is either removed or conditioned
in this process by addition of some additives under specific
condition. The most common additive for this purpose are
phosphoric acid and citric acid. A specified quantity
of any one or mix of such additives is mixed in the oil
charge for a specific period and process parameters. This
cause a separation of phosphatides from oil and are removed
after certain settling time. Some times these separated
gums are not directly removed but with soap stock formed
during neutralisation. The oil mass is then neutralised
with Alkali for removal for free fatty acid in the form
of soap stock. This soap stock is removed from oil mass
by gravity separation method. For removal of Alkali traces.
Oil is washed with hot water. The chemical reaction involved
in this operation is as follows: R-COOH+NaOH à
RCOONA + H2O.
Bleaching
The neutralised washed oil is then taken for second step
in refining i.e. Bleaching. In this operation, the oil
is taken in Cylindrical vessel provided with agitator
called `Bleacher' and kept under vacuum and heated upto
90oC with steam. The moisture from oil is thus evaporated
and oil becomes dry. Then dry is treated with Bleaching
earth (fuller's earth) and Carbon. These a outs absorb
most of the residual colour free the oil remaining after
Neutralisation. The mixture of oil and bleaching agents
is filtered through a standard plate and frame press for
separation. The clear oil obtained is bleached oil and
is very much lighter in colour than the neutralised oil.
In this operation, the colouring pigments in oil are adsorbed
by certain bleaching agents under specific conditions.
The oil is finally filtered for removal of bleaching agents.
The oil charge is dehydrated under vacuum to avoid any
further detoriation due to oxygen. A specified quantity
of bleaching agents is added that acts as adsorbing material
for colouring matter. This externally added bleaching
material is removed by filtration.
Deodorisation
The oil after bleaching is practically pure, but contains
minute quantities of original odoriferous matter. Also
the chemicals used during neutralisation process in a
cylindrical vessel called `Deodoriser'. The Deodoriser
is kept under very high vacuum and the bleached oil is
taken in it. The oil then heated at high temeprature 200C
with high pressure steam and open steam is passed through
the oil. Under high vacuum and temperature the open steam
leaves the deodoriser is completely bland and free from
any odour and taste. This oil is then cooled and clarified
through a Filter Press to get sparkling oil. The filtered
oil is then packed into standard size tins and sealed.
The vitamins `A' and `D' are added to this filtered oil
if necessary before packing. This step takes care of the
odour of the oil. The purpose of deodorisation is to make
oil blend and tasteless. The oil charge is taken to very
high temperature under max attainable vacuum. The volatile
materials are evaporated off with some carrier (commonly
direct steam). In this process the peroxide value of oil
is brought down as minimum as possible. In order to increase
the storage life of refined oil antioxidants may also
be added under specified conditions. This oil is passed
through micro filter to give a crystal clear appearance
to the refined oil.
The efficiency of Neutralising operation is determined
by the least possible loss of Neutral oil in soap stock.
As such, in this operation the quantity of original oil
is reduced by its free fatty acid content plus quantity
of neutral Oil in soap stock plus impurities. The constitutes
refining loss or neutralising loss and is generally two
to two and half times the free fatty acid content of the
oil. After draining of the soap stock the oil which is
now free from fatty acids and impurities is washed repeatedly
with hot water to free it from any caustic soda and soap.
These dissolve in the wash water, which is drained from
the bottom after settling. Neutralisation also removes
bulk of the colour of the Crude Oil and makes it lighter.
The oil after bleaching is practically pure, but contains
minute quantities of original odoriferous matter. Also
the chemicals used during neutralisation process in a
cylindrical vessel called `Deodoriser'. The Deodoriser
is kept under very high vacuum and the bleached oil is
taken in it. The oil then heated at high temeprature 200C
with high pressure steam and open steam is passed through
the oil. Under high vacuum and temperature the open steam
leaves the deodoriser is completely bland and free from
any odour and taste. This oil is then cooled and clarified
through a Filter Press to get sparkling oil. The filtered
oil is then packed into standard size tins and sealed.
The vitamins `A' and `D' are added to this filtered oil
if necessary before packing. This step takes care of the
odour of the oil. The purpose of deodorisation is to make
oil blend and tasteless. The oil charge is taken to very
high temperature under max attainable vacuum. The volatile
materials are evaporated off with some carrier (commonly
direct steam). In this process the peroxide value of oil
is brought down as minimum as possible. In order to increase
the storage life of refined oil antioxidants may also
be added under specified conditions. This oil is passed
through micro filter to give a crystal clear appearance
to the refined oil.