Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 3
3.2.9 Extraction (C.1)
3.2.9.1 Water
Water usage is an issue when water is used as a solvent in the extraction process. Also,
extraction equipment is cleaned periodically to ensure efficient and optimum operating
conditions. The frequency of cleaning depends on the product and extractor design. This
cleaning will generate waste water containing soluble and insoluble organic material and SS.
For example, in the extraction process of oil from oilseeds with hexane, cooling water is needed
in an amount of 0.2 to 14 m 3 /t oilseed. Furthermore, a certain amount of waste water is
generated, mainly from the hexane/water separation, which amounts to 0.2 to 0.5 m 3 /t oilseed;
the load being of 0.1 to 1 kg COD/t oilseed. The amounts of water consumption and of pollution
depend on the cooling water system, e.g. once-through or with recycling, and on the kind of
oilseeds. The throughput rate of the toaster also has a major influence on these parameters.
Water consumption for the pressing of oil is minimal.
3.2.9.2 Air emissions
Extraction with organic volatile solvents may cause emissions of VOCs. Council Directive
1999/13/EC [157, EC, 1999] includes provision for oilseed extraction, including VOC emission
limit values for vegetable oil and animal fat extraction, and vegetable oil refining activities.
Extraction plants may also cause odour, due to the emission of H2S and organic compounds.
When extraction with water takes place, water vapour containing non-condensable VOCs may
be released to the air.
3.2.9.3 Solid output
The solid output may be re-used as a product or co-product, or be disposed of. For example,
after the removal of the adhering water, spent coffee grounds can be burned as fuel in steam
boilers or used as raw material for further processing. The solid output may contain solvents.
3.2.9.4 Energy
Electrical energy and steam are required; the levels depend on the type of application. For
example, energy consumption is of 170 – 390 kWh steam (600 to 1400 MJ) and 30 – 60 kWhe/t
oilseed (100 to 200 MJ). The energy consumption depends mainly on the kind of oilseed and of
the type of cooling water circuit.
3.2.9.5 Noise
Possible sources of noise are cooling towers, fans and steam safety valves.
3.2.10 Deionisation (C.2)
3.2.10.1 Water
The regeneration of ion exchange columns produces water containing the chemicals used for
regeneration, usually acids or alkalis and brine; ions removed from the product, minerals and
impurities extracted from the used column. The pH of the waste water fluctuates. Regeneration
starts with rinsing the ion exchange columns with water. This produces waste water containing
soluble organic material and product residues, which depending upon their dilution, may be
reprocessed.
128 January 2006 RHC/EIPPCB/FDM_BREF_FINAL