Integrierte Vermeidung und Verminderung der Umweltverschmutzung

2.1.4.11.3 Description of techniques, methods and equipment
Chapter 2
Carbonatation is the introduction of the milk of lime, calcium hydroxide, and carbon dioxide
gas (CO2) into a liquid to form calcium carbonate and to precipitate and remove impurities. The
effect of lime and CO2 is the precipitation of insoluble calcium salts, the flocculation of
colloidal components, the chemical degradation of other molecules such as invert sugar and
amides, and the absorption of non-sugars on precipitated calcium carbonate. Lime and CO2 are
normally produced in lime kilns by the thermal dissociation of limestone.
Any non-sugar components contained in the raw sugar juice after extraction from the beet, make
the subsequent stages in the sugar process impossible to perform. Therefore, the raw juice must
be purified to allow further processing. This is achieved by continuously adding milk of lime
and carbon dioxide from the lime kiln to precipitate most of the non-sugars. The product after
filtration contains the calcium carbonate and the non-sugars and is used in agriculture as a
liming material to improve the structure of arable soil and to regulate soil acidity. Sugar factory
lime may also be used for site recovery, e.g. filling quarry ditches, and for producing bricks or
cement. For aspects relating to lime kilns, see the “Cement and lime BREF” [219, EC, 2001].
2.1.4.12 Carbonation (D.12)
2.1.4.12.1 Objective
The aim of this process is to dissolve a quantity of carbonic gas into different products to obtain
a gasified or carbonated final product. When dissolved in water, carbon dioxide (CO2), is
sparingly soluble and thus, slowly released, forming bubbles that provide a characteristic
mouthfeel and a unique taste when consumed. In addition to an organoleptic property, under
suitable conditions, CO2 has a preserving property by the inhibition of the development of
harmful aerobic micro-organisms. This, however, is not a substitute for other methods used to
ensure microbiological safety.
2.1.4.12.2 Field of application
Carbonation is an important process step in the preparation of many soft drinks and certain
types of mineral waters. It is also applied in the wine and brewing industries. In the manufacture
of still wines, carbonation is used to protect the colour and increase the aroma.
2.1.4.12.3 Description of techniques, methods and equipment
Carbonation results from the impregnation of a liquid with CO2 to form carbonic acid. The CO2
was traditionally obtained from lime kilns, by heating calcium carbonate, but this has now been
universally replaced in the soft drinks sector by the storage of bulk liquefied gas externally
delivered by a CO2 supplier. The gas is stored within pressurised insulated tanks kept at a very
low temperature. In common practice, the gas tends to be generated as a by-product of
fermentation or chemical processes from companies outside of the soft drinks sector.
A carbonator combines CO2 gas with the liquid to be carbonated. Current carbonators can be
classified into two main categories; those that carbonate water only and those that carbonate the
finished product mixture of syrup and water. These are sometimes coupled with coolers, often
referred to as carbo-coolers. The principal designs available are carbonators with integral
coolers, draining wall heat-exchangers and carbon dioxide injectors.
In combination with this process, de-aeration, i.e. the removal of air, is vital and is usually
applied to the water component in a first stage. The presence of air can create spoilage
problems. CO2 is sometimes used to flush out air, however, the use of mechanically de-aerated
water has become more popular in recent years.
RHC/EIPPCB/FDM_BREF_FINAL January 2006 33