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The gas flow are conducted by the active coal, where the components that
needs to removed with
adsorption are bound to the active carbon until these are saturated. After reaching the
saturation degree of the active carbon these are
replaced or are regenerated.
At the replacement of active carbon it is generally transported taken back
by the supplier who if (chemical) as waste dispose it of or
regenerate it. When the company regenerates the active carbon himself we
speak of regenerative
adsorption.
Generally the saturation degree is expressed in g/kg active carbon. The
saturation degree depends on the concentration in air. Experimentally
adsorption isotherms can be established which give the
link between the number of grams of a component per grams active carbon
which can become captured and the partial pressure of the component in
air. The partial pressure of a component depend on the concentration on the
component in the gas and on the pressure of the degasses. At higher concentration and higher
pressure the
partial pressure of the
component become larger.
The isotherm of active carbon is linear. At higher partial pressures the capacity becomes proportionally higher. This makes that active
carbon at a given temperature has a higher adsorption capacity at high then at low entrance concentrations.
However at higher temperature the
adsorption capacity will diminish .
1rst estimated value can be adsorption capacity of 20 - 25 g solvent
(expressed as carbon) by 100 g active carbon at a good functioning of
the adsorption. If the component adsorbs badly, the temperature and the humidity of air high becomes
higher the capacity will be less.
Adsorption by means of actively carbon can happen under the form of filled patterns,
dumped carbon combined in a caught bed or as injection of powder shaped
carbon combined with a filter screen.
Alternatives for adsorption with active coal are:
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Impregnated actively coal adsorbs and holds the
specific components long enough so that the chemical impregnant can react with
pollution (chemisorptions). Impregnated actively coal has been devised especially chemical
for components which adsorb difficult to catch with standard active
coal.
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Sorbalite (active coal + lime): this mixture is used for
cleaning degasses of combustion ovens. With one product are possible the SOx then both and dioxin problems
are remedied.
The advantages for the use of active coal are:
-
High efficiency of VOC disposal
-
Simple and robust technology
-
Arranged for discontinue processes
-
Easy maintenance
-
Easy to place
The disadvantages are:
-
Substance can ensure constipations
-
Mixtures of components can ensure a fast disruption
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Not arranged for wet degasses (less critically active
carbon
impregnated)
-
Risk of spontaneous combustion of the bed (ketones,
terpentines, ...)
-
Risk on polymerization of unsaturated KWS on the active
carbon
(exothermic causes constipations)
Cabbage sorption has actively a complete broad application range for:
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The disposal of solvents and VOC at printing,
spray paint companies
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The disposal of dioxins, heavy metal such as mercury and other
remaining emission in waste combustion ovens
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Removel of scents, air-conditioning
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Cleansing of process gases such as synthesis gases, hydrogen,
natural gas, carbondioxide, gas dumpsters and solvent recuperation
-
Recuperation of tetrachloroethylene fume in the
drying house
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VOC disposal in foundries
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