Activated Carbon Adsorption Vapor Recovery Equipment
Process Description
Control of VOC or HAP vapors can be accomplished activated carbon adsorbers. Activated carbon adsorption vapor recovery units utilize the carbon's ability to preferentially adsorb certain molecules from gaseous mixtures. Activated carbon, with its highly porous structure and vast surface area, adsorbs hydrocarbons from the air/hydrocarbon mixture emitted from the vapors generating source. This could be an operational process, a loading or unloading operation, etc. The hydrocarbon
molecules are adsorbed onto the carbon surface and are retained there until the regeneration step. The ability of the carbon to adsorb fuel vapors is enhanced by higher concentrations, higher pressures and lower temperatures. Adsorption of the hydrocarbon molecules proceeds until the available surface area of the carbon is filled or saturated with the hydrocarbon molecules.
The adsorbed hydrocarbons are then regenerated (desorbed or removed) from the carbon by decreasing the pressure, reducing the hydrocarbon concentration around the carbon particles or increasing the temperature of the carbon bed. A combination of these steps can also be used for regeneration. There are three basic types of activated carbon adsorption systems available to recover or remove hydrocarbon vapors from an air stream. Two of these systems regenerate the activated carbon in-situ for reuse. The third system requires that the carbon be removed to another site for regeneration.
The first two systems that provide in-situ regeneration are: Pressure Swing Regenerated Systems and Thermally Regenerated Systems. The third type of system, which requires removal of the activated carbon to another site for regeneration or disposal, is a once through Single Use or canister system. The canister systems can usually be purchased directly from the activated carbon manufacturer.
The following is a brief discussion about two of the three types of carbon based vapor control systems: