Thermally Regenerated Activated Carbon Technology
In low vapor concentration applications, thermally regenerated activated carbon (TRAC) vapor recovery system can be used. In the thermally regenerated activated carbon system at least two (2) carbon vessels are provided to insure uninterrupted service. In some applications, three carbon beds are provided. Please note: in the context of this discussion the number of beds is not necessarily the number of vessels utilized to contain the activated carbon since two or more maybe piped together in such a fashion that they are used simultaneously making one large bed.
In the dual bed systems the vapors enter one of the carbon vessels and are dispersed through the bed of activated carbon, most of the hydrocarbons are adsorbed onto the carbon and cleaned air is vented to the atmosphere. As hydrocarbons are being adsorbed in the on-line carbon vessel, the second vessel is being regenerated. Hydrocarbons are removed or desorbed from the activated carbon by heating the bed with steam or heated inert gas. The regenerated hydrocarbons are sent to the next step in the process where they are condensed. The regenerated bed is cooled and then placed back into service to adsorb the hydrocarbon vapors.
Typically, in the applications that use more than two beds, one bed is adsorbing vapors, the second bed is being thermally regenerated, and the third bed is in the cool down mode. This allows for quicker switching of the beds than the two bed system.
Applications for these types of systems include hydrocarbon vapor concentrations of 1% or less. Some of the hydrocarbon vapors controlled are: solvents such as methylene chloride, trichloroethane, toluene, and other chemicals such as styrene, phenol, various alcohols and ketones.
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Some Manufacturers of TRAC systems are: