|
 device for capturing and recovering dilute volatile
organic compounds and other hazardous air pollutants has been
developed by researchers at the University of Illinois.
 "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 US 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 US Army Construction
Engineering Research Laboratory, Joseph Wander at the US 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. 
|
