Researchers at the University of Illinois have developed a device for capturing and recovering dilute volatile organic compounds and other hazardous air pollutants.
‘The device uses activated-carbon-fibre 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’ said Mark Rood, a University of Illinois professor of civil and environmental engineering.
Researchers say the activated-carbon-fibre cloth has almost twice the adsorption capacity of activated-carbon granules at low concentrations. The material also 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 recovery and reuse of the captured pollutants.
‘The vapour-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. ‘The exhaust from the booth would be blown through an adsorption bed containing a number of cylindrical cartridges of activated-carbon-fibre cloth, which would trap the solvent.’
To release the solvent, an electric current passes through the fabric, allowing for rapid heating, said Sullivan. ‘The solvent boils off the fabric, condenses on the inside of a 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. ‘We can treat very dilute gas streams and provide a pure liquid effluent with this new device’ said Rood.
The electrothermal process is also said to allow 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 uses as much power as a hair dryer does. Industrial-sized units would start at the size of large filing cabinets, said Sullivan. The carbon-cloth cartridges have been regenerated over 100 times without degradation to the cloth.
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