The basic Vapor Recovery Unit system is comprised of a PSA (Pressure Swing Adsorption) process with two activated carbon bed vessels, alternating on a 15 minute time cycle. Regeneration of the carbon reactors is accomplished primarily by vessel evacuation with two stage liquid ring vacuum pumps to a pressure level of-27î Hg (3î Hg absolute) and secondarily with an ambient air purge input to the bed in a controlled manner during the last 25% of the regeneration cycle.

The VOCs (Volatile Organic Compounds) desorbed from the carbon during reactor regeneration are effectively recovered in a two step process including condensation in the liquid ring vacuum pump and absorption in a packed tower, counter current flow, absorber. Supply tank gasoline is pumped on skid for use as a lean oil in the absorber and as a heat exchange fluid for the liquid ring vacuum pump seal fluid.

The liquid ring vacuum pump seal fluid circuit (ethylene glycol and water) is a closed loop flow circuit that supplies the sealing fluid required by the vacuum pump. This fluid serves several purposes providing adequate pump sealing, cooling pump mechanical seals, removing pump heat and removing VOC condensation heat. The seal fluid is circulated in counter-current flow through a single pass shell and tube heat exchanger where it is cooled using supply tank gasoline as a coolant.

All product recovered by the system is pumped back to the gasoline supply tank mentioned. Here the enriched liquid gasoline is allowed to disperse throughout the supply tank environment and cause minimal changes in product characteristics.