Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
The neutralised oil is bleached to remove colouring matter, such as carotenoids and other minor
constituents, such as oxidative degradation products or traces of transition metals. Bleaching
uses activated Fuller’s earth with treatments typically in the 90 to 130 ºC range for
10 to 60 minutes. The earth is sucked into the oil under vacuum and is removed by filtration.
The bleached oil is steam distilled at low pressure to remove volatile impurities including
undesirable odours and flavours. This process, known as deodorisation, takes place in the
temperature range of 180 to 270 ºC and may last from 15 minutes to 5 hours depending upon the
nature and the quantity of the oil, and the type of equipment used. For example, if a batch
deodoriser is used, it would take between 4.5 to 5 hours depending on the oil type and the
quantity. However, if the same oils were processed in a semi-continuous deodoriser it would
take about 15 minutes. Figure 2.8 shows a flow diagram of crude oil chemical refining. Olive oil
and husk from pomace oil refining is similar to oilseed oil refining.
INPUT:
Crude
vegetable
oil
OUTPUT:
Auxiliary
material
1. Neutralisation/
and/or final
degumming
Waste water
Adsorbent
2. Bleaching
Internal
recycling or
waste
Figure 2.8: Crude oil chemical refining
[79, Italian contribution, 2001]
Electricity
Fuel / Steam
Water
Catalyst
3.
Hardening
Waste (if
applicable)
Auxiliary
material
4. Interesterification
5.
Deodorising
Waste water
Finished
product
Physical refining is a simpler process in which the crude oil is degummed and bleached,
followed by steam stripping which removes ffa, odours and volatiles in one step. The oil is
heated to temperatures of up to 270 ºC and then refined by the oil flowing over a series of trays
countercurrent to the flow of the stripping steam. The advantages of physical refining are the
higher yield, the lower cost and the fewer chemicals used. One of the disadvantages, compared
to chemical neutralisation, can be a lower quality of the end-product.
There are three other processes which may be carried out during oil refining, depending upon
the oil source. These are winterisation, which essentially is the removal of wax which would
otherwise cause cloudiness. This is carried out on, e.g. sunflower oil. The process involves
cooling the oil followed by filtration, using a filter aid to remove wax. The second process is
fractionation. Typically this may be carried out on crude or refined oil. This involves
completely melting the solid oil, followed by cooling to yield solid and liquid fractions which
have different functional properties (see Section 2.2.5.3.). The third process is
interesterification. This involves the separation of triglycerides into fatty acids and glycerol
followed by recombination. The reaction is carried out using citric or phosphoric acid plus a
catalyst, typically sodium methoxide. Interesterification modifies the functional properties of
the treated oil and may be carried out after neutralisation or deodorisation.
RHC/EIPPCB/FDM_BREF_FINAL January 2006 77