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Gas Phase Activated Carbon Adsorption 409

Table 5
Reported Operating Capacities for Selected Compounds
Average inlet concentration Adsorption capacity a
Compound (ppmv) (lb VOC/100 lb carbon)
Acetone 1000 8
Benzene 10 6
n-Butyl acetate 150 8
n-Butyl alcohol 100 8
Carbon tetrachloride 10 10
Cyclohexane 300 6
Ethyl acetate 400 8
Ethyl alcohol 1000 8
Heptane 500 6
Hexane 500 6
Isobutyl alcohol 100 8
Isopropyl acetate 250 8
Isopropyl alcohol 400 8
Methyl acetate 200 7
Methyl alcohol 200 7
Methylene chloride 500 10
Methyl ethyl ketone 200 8
Methyl isobutyl ketone 100 7
Perchloroethylene 100 20
Toluene 200 7
Trichloroethylene 100 15
Trichlorotrifluoroethane 1000 8
Xylene 100 10
a Adsorption capacities are based on 200 scfm of solvent-laden air at 100ºF (per hour).
Source: US EPA.

The VOC removal efficiency of gas phase carbon adsorption systems has been
compared by Moretti and Mukhopadhyay (22) with that of catalytic oxidation, flar-
ing, condensation, absorption, heaters, biofiltration, membrane separation, and ultraviolet
(UV) oxidation.
4.7. Regeneration and Air Pollution Control of Carbon Adsorption System
A schematic of a standard fixed-bed CAS is shown in Fig. 4. Typically in a three-bed
CAS, two beds are adsorbing, and the third is desorbing. Steam is typically used to
regenerate the carbon. Most organic solvents are stripped from the carbon with high
temperature and water vapor. The condensed water leaving the system carries the cap-
tured organics. Additional treatment is required to separate the captured organics from
the water prior to its disposal. An alternative to using steam for regeneration is to use
an inert gas to reactivate the carbon. After regeneration, the captured organics must be
separated from the inert gas. The inert gas systems are initially more expensive than
steam regeneration systems. The benefits of regenerating with inert gas are that it con-
sumes less energy and recovers a purer solvent. These benefits may provide sufficient