Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
The process can also be carried out by passing the product in aqueous solution through a
column of active material, e.g. using granular activated carbon or ion exchange resin beads.
Here, only minimal filtration is required after the process as the active material is held in place.
Active material is withdrawn from the column at regular intervals and replaced by new or
reactivated material.
The main purpose of both these operations is to remove colour molecules from the product as
well as precursors that may give rise to colour formation on storage, which is known as ageing.
The majority of the impurities removed are organic in nature. Passage over activated carbon
may also be helpful in removing phenolic material, which may cause taints, pesticide residues
and some heavy metals.
2.1.3.12 Distillation (C.12)
2.1.3.12.1 Objective
Distillation is the separation of the components of a liquid mixture by partial vaporisation of the
mixture and separate recovery of the vapour and residue. The more volatile components of the
original mixture are obtained at a higher concentration in the vapour, the less volatile in a higher
concentration in the liquid/solid residue.
2.1.3.12.2 Field of application
Distillation enables the separation and purification of volatile food products from aqueous
blends. Distillation can be used to separate flavours or essential oils, but is mainly used either
for the production of potable alcohol or spirits, or for the industrial production of alcohol from
agricultural raw materials, e.g. fruit and grain, which can then be used in alcoholic drinks or
liquors. Distillation normally follows alcoholic fermentation.
Spirit drinks production is regulated by Council Regulation (EEC) No 1576/89 [218, EC, 1989].
They are prepared from the distillate of the alcoholic yeast fermentation of products from
agricultural origin.
2.1.3.12.3 Description of techniques, methods and equipment
The process takes place in two basic types of equipment; the pot still and the column still. Stills
may be operated singly or in groups. The addition of heat enables the separation of
alcohol/aqueous compounds from the initial liquid feed in the still. Condensed aqueous alcohol
is removed as a liquid spirit from the head of the still, whilst a residual stream is discharged
from the base.
The pot still can be operated in a batch or continuous manner. In the former case, a batch of
material is charged to the still pot, boiling is initiated, and the vapours are then continuously
removed, condensed and collected until their average composition has reached a desired value.
When operated in a continuous manner, feed is continuously passed to the still pot with the
vapour and liquid portions being continuously removed.
In column distillation, the alcoholic liquid or beer enters a distillation tower heated with vapour.
In each contacting device, generally a tray, an equilibrium is created between the vapour
enriched with volatile components and the condensed liquid. Crude alcohol is drawn off from
the top of the tower and then rectified through another tower where 95 % of the alcohol is
separated from higher alcohols. At the bottom of the first tower, an aqueous blend or stillage is
drawn off. A condensed water or stillage water, contaminated slightly with organics, is drawn
off at the bottom of the second tower once the alcohol has been dehydrated. 95 % alcohol can be
turned into anhydrous alcohol by a number of different technologies. These technologies can
include azeotropic distillation using a third component, adsorption by a molecular sieve, or
dehydration by a membrane technique. Some spirits and ethyl alcohols of agricultural origin can
be distilled higher than 84 %.
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