Vapor-Recovery System Captures And Recycles Air Pollutants

“The new vapor-recovery system is fast, convenient and can achieve new levels of air-quality control,” said Mark Rood, a UI professor of civil and environmental engineering. “The device uses activated-carbon-fiber cloth and electrical energy to collect and efficiently recover air pollutants that are emitted to the atmosphere from the use of materials such as paint solvents and cleaning solutions.” The activated-carbon-fiber cloth has nearly twice the adsorption capacity of activated-carbon granules at low concentrations and has a woven structure that allows the adsorbent to be pliable and electrically conductive for electrothermal desorption. Electricity flows through the carbon cloth causing heating, while allowing for efficient recovery and reuse of the captured pollutants.

“The vapor-recovery system could be used to control the emissions from large paint booths, for example, including the hangar-sized units used to paint entire aircraft,” said Patrick Sullivan, a civilian employee at the U.S. Air Force Research Laboratory who is pursuing his doctorate at the UI. “The exhaust from the booth would be blown through an adsorption bed containing a number of cylindrical cartridges of activated-carbon-fiber cloth, which would trap the solvent.”

To release the solvent, an electric current passes through the fabric, allowing for rapid heating, Sullivan said. “The solvent boils off the fabric, condenses on the inside of the chamber and drains into a collection vessel for recovery and reuse.”

Because electrothermal desorption does not require an adsorbent drying step, the regeneration process can be faster and more energy efficient than conventional desorption techniques used with activated-carbon granules, Rood said. “We can treat very dilute gas streams and provide a pure liquid effluent with this new device.”

The electrothermal process also allows for desorption and condensation of a volatile organic compound without contaminating the condensate with water – which would require a costly and complex distillation process for water-soluble solvents.

The current bench-scale device is slightly larger than a football and uses as much power as a hair dryer. Industrial-sized units would start at the size of large filing cabinets, Sullivan said. The carbon-cloth cartridges have been regenerated over 100 times without degradation to the cloth.

Collaborators on the project include K. James Hay at the U.S. Army Construction Engineering Research Laboratory, Joseph Wander at the U.S. Air Force, and graduate students David Ramirez and Katherine Dombroski at the UI. A pilot-scale program is being planned for later this fall with chemical engineer Massoud Rostam-Abadi at the Illinois State Geological Survey.

The researchers have applied for a patent.