Vapor Phase Carbon Vessels are used to remove pollutants from the air through an adsorption process. Contaminants such as gasoline range organics (GRO), volatile organics (VOC), and chlorinated compounds are physically absorbed onto the surface of activated carbon in the vessel. Porous grains of carbon are used because they have a large internal surface area that adsorbs organic and inorganic compounds as well as some metals.
The activated carbon media within a VGAC vessel has a finite lifespan before it begins to breakthrough and allows contaminants to pass through the filter. Carbon vessels are typically installed in a lead/lag, series orientation to ensure no pollution passes through the vessels. Once carbon is spent in one vessel, it is replaced with fresh carbon and the orientation of the vessels is switched via a piping header or toggling hoses. After the changeout, the former lag vessel becomes the new lead vessel and vice versa.
Typical Treatment Application
- Vapor phase granular activated carbon
- Impregnated granular activated carbon/clays/zeolite
- Vapor phase polymers & resins
- Bio venting & bio-pile systems
- Off gas treatment for SVE/DEP systems and air strippers
- Excavation venting
- Remediation systems
- Odor control
- Industrial off gas treatment
Compounds Treated with Vapor Phase Vessels
- Trichloroethene (TCE)
- Tricholoroetheane (TCA)
- Dichloroethane (DCA)
- BTEX (Benzene, Toluene, Ethylbenzene, Xylene)
- Hydrogen Sulfide
- Hydrogen Chloride
- Carbon Tetrachloride
- Gas range organic compounds
- Diesel range organic compounds
- Volatile organic compounds
The picture to the left shows contaminants being adsorbed by the carbon. The larger the compounds, the easier and faster it is for the carbon pores to get plugged up. This has a direct impact on the bed life of the carbon.
Depending on concentration, flow and other characteristics, alternate treatment options may be required in addition to GAC treatment.
H2K offers multiple treatment options that can accommodate a large variety of applications. H2K is able to provide performance modeling to determine sizing and bed life based on provided analytical data. Air flow, contaminant concentration, relative humidity, pressure drop and discharge criteria are all factors in determining the proper carbon filter size.
Contaminants & concentrations: VGAC vessels provide satisfactory adsorption performance so long as the activated carbon has sufficient space to adsorb contaminants. Larger particle contaminants will use up carbon granules more quickly and cause more frequent changeouts. VGAC will process and treat air with higher pollutant concentrations just as well as lower concentrations, but carbon will be used more quickly and require more frequent changeouts.
Process flow rate: As flow rate through a carbon vessel increases, carbon will be used more quickly and pressure drop across the filter will increase. The proper balance between vessel size and flow rate must be considered to avoid over or undersizing the vessels.
Design Options Available
VC Series – This line is our standard option for vapor phase adsorption. Units come standard with welded steel construction and internal epoxy coating for corrosion resistance. A false bottom is installed to create an air plenum underneath the carbon bed which allows even air distribution through the vessel. Units can handle flows up to 3,700 SCFM.
VCD Series – The VCD series vapor phase carbon vessels as designed for easy carbon change-out. These units feature a manual chain hoist to lift the vessel which allows spent carbon to be collected in containers for disposal. This process allows users to avoid costly vac truck services. Vessels are designed up to 7,800 SCFM
VCS Series – Stacked bed VGAC vessels are designed with two carbon beds inside to increase treatment capacity in a reduced footprint. These vessels feature an air plenum above and below the bed to minimize pressure loss and maintain even distribution across bed at low and high flow rates and can process up to 22,600 SCFM.
VRC Series – This line features a radial airflow design to increase surface area and reduce pressure drop across the vessel. These are a terrific fit for centrifugal fans, regenerative blowers, or other low pressure blowers. Units are rated up to 1800 SCFM.
Former ordinance plant
This project utilized a 3,600 CFM VGAC vessel for treatment of air stripper off-gas as part of a groundwater treatment system. Vessels were installed to treat TCE and DCE which was stripped from the water in the air stripper.
Easy change-out VGAC vessels
In an effort to reduce carbon change-out costs, H2K technologies partnered with a client to design carbon vessels that allow a technician to remove carbon without an expensive vacuum truck. This dump bed carbon vessel allows users to directly dump carbon into containers for transport and disposal off site. These vessels treated mercury at 5,000 CFM.
SVE remediation system
A pair of 36” diameter VGAC vessels was utilized to treat off-gas from a rotary claw blower as part of a soil vapor extraction system. This project required a heat exchanger on the SVE discharge to ensure air flow through the carbon vessels would be cool enough for proper adsorption. This system was capable of treating 600 SCFM.