Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
2.1.3.9.3 Description of techniques, methods and equipment
Edible oils and fats are mixed with bleaching earth that has an affinity for adsorbing the abovementioned
undesirable compounds. The oil is mixed under vacuum conditions with 0.1 to 3 %
of bleaching earth. This is a clay mineral, such as bentonite or montmorillonite, that has been
activated by thermal and/or acidic or other treatments. These earths, sometimes mixed with
small amounts of activated carbon, have a very high adsorbing capacity. After bleaching for
30 o 90 minutes, the oil is separated from the bleaching earth, using filters. The spent earth
contains high amounts of oil, up to 30 %. A steam stripping process can recover a part of the oil
or fat. Used bleaching earth can be added to the meal in integrated installations. The bleached
oil is further treated in other refinery processes. The equipment used for bleaching consists of
mixing vessels, vacuum generators and filters.
2.1.3.10 Deodorisation by steam stripping (C.10)
2.1.3.10.1 Objective
The objective of deodorisation is to remove ffa and other highly volatile compounds from crude
degummed and/or alkali refined edible oils and fats after bleaching.
2.1.3.10.2 Field of application
Deodorising is applied in the refining of edible oils and fats.
2.1.3.10.3 Description of techniques, methods and equipment
Deodorisation is the use of steam distillation to strip ffa and other highly volatile components,
under vacuum conditions, from oils and fats. The equipment used for deodorisation consists of a
steam distillation column, barometric condenser, demisters and scrubbers. Steam is injected into
the oil heated to over 200 °C at the bottom of the distillation column, which is under vacuum
conditions. The steam strips the ffa and other impurities from the oils and fats but gums are not
removed by this process. The steam is condensed afterwards, using a barometric condenser of
either once-through or closed-circuit design (see Section 2.1.9.4). The separation of the volatile
components from this steam can be enhanced by a one-stage or a two-stage
scrubbing/condensation system and by demisters. Deodorisation can be operated in batch or
continuous deodorising vessels.
2.1.3.11 Decolourisation (C.11)
2.1.3.11.1 Objective
Decolourisation is carried out to improve the colour, purity, ageing, microbiological stability
and shelf-life of certain food products.
2.1.3.11.2 Field of application
Decolourisation is used in the sugar, glucose, syrup and fermentation industries.
2.1.3.11.3 Description of techniques, methods and equipment
Decolourisation can be carried out by the addition of an active powder, e.g. powdered activated
carbon, to the product in aqueous solution, which is then mixed under controlled conditions.
Afterwards, the powder is removed by filtration, using static filters or rotary vacuum filters,
while the decoloured product is processed further. This process is often carried out in multiple
stages with the active material being re-used until exhausted, often using a countercurrent
system.
24 January 2006 RHC/EIPPCB/FDM_BREF_FINAL