Integrierte Vermeidung und Verminderung der Umweltverschmutzung

2.1.3.8.2 Field of application
Chapter 2
Chemical neutralisation is applied in the refining process of vegetable oils such as soybean oil,
sunflower oil, rapeseed oil, and of animal oils and fats such as tallow or fish-oil.
2.1.3.8.3 Description of techniques, methods and equipment
The oil is preheated using steam, after which phosphoric acid or citric acid is mixed with it to
increase the water solubility of the phosphatides. The acidified oil, with a crude oil content of
0.5 to 6 %, is then mixed with a caustic solution, which neutralises both the ffa and the
phosphoric or citric acid, and further increases the water solubility of the phosphatides. The
aqueous mixture of soap and phosphatides, which is known as soap-stock, is separated from the
oil by centrifugation. The oil is mixed with water to wash off the rest of the soaps. Again, the
water is removed from the oil by centrifugation. The caustic refined oil may be dried under
vacuum conditions and then pumped to a storage tank. The process is typically operated in a
continuous way, as shown in Figure 2.1, but it can also be a semi-continuous or batch process,
using long period mixing and sedimentation equipment.
Figure 2.1: Flow diagram of continuous neutralisation of oils and fats
[87, Ullmann, 2001]
The centrifuge aqueous discharges, i.e. the soap-stocks, are combined and further treated in a
soap-stock splitting system. This acidulation process is used to recover the ffa after treatment
with concentrated acid, usually sulphuric acid or occasionally hydrochloric acid, and heating
with steam. The separated ffa are then removed in a decanter centrifuge. In integrated
installations, the soap-stock can be added to the meal toasting process. The phosphatides
recovered are used as lecithin in human food or in animal feed.
2.1.3.9 Bleaching (C.9)
2.1.3.9.1 Objective
The objective of bleaching is to remove pigments, metals, e.g. nickel or iron from other oil
refinery processes; residual soaps and phospholipids from the oil or fat.
2.1.3.9.2 Field of application
Bleaching is applied in the refining of edible oils and fats.
RHC/EIPPCB/FDM_BREF_FINAL January 2006 23