Recycling pollutants
Recycling pollutants
Keywords: University of Illinois, Organic pollutants, Recycling
Researchers at the University of Illinois at Urbana, Champaign (Champaign,Illinois) have developed a device that captures and recovers dilute volatile organic compounds (VOCS) and other hazardous air pollutants.
"The new vapour recovery system is fast, convenient, and can achieve new levels of air quality control", says Mark Rood, a UI professor of civil and environmental engineering. "The device used 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."
The activated carbon fibre 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 vapour recovery system could be used to control the emissions from large paint booths, for example, including the hanger sized units used to paint entire aircraft," says Patrick Sullivan, a civilian employee at the US Air Force Research Laboratory who is pursuing his doctorate at UI. "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."
An electric current passing through the fabric releases the solvent and allows for rapid heating, Sullivan explains. "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 says.
"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 VOC 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 says. The carbon cloth cartridges have been regenerated more than 100 times without degradation to the cloth.
