Innovative use of a carbon fibre material allows hazardous air pollutants (HAPs) to be collected and siphoned off for reuse.
The Construction Engineering Research Laboratory (CERL), in partnership with the University of Illinois and the US Air Force, has developed a cartridge-like device that captures HAPs and volatile organic contaminants (VOCs) exhausted from operations such as painting and chemical cleaning. These materials can then be recycled for uses such as paint thinning.
The new device is expected to save between 20 and 50% over conventional treatments while enabling production plants to comply with the US Clean Air Act.
CERL’s new system uses a woven, pure carbon fibre cloth which is rolled up into cylinders and located in a metal vessel. When HAPs-contaminated air is pulled through the vessel, the substance adheres to the carbon fibers until the adsorbent is saturated. Then an electric current passes through the cylinders and the captured material desorbs from the fabric, condensing onto the chamber walls, which have remained cool throughout the process.
‘Much of the energy goes into desorbing material from the carbon fibers, not in heating of the ancillary equipment and containment vessel,’ said Dr. James Hay, CERL researcher who led the project. ‘The liquid HAP that collects on the cool walls of the vessel is readily removed from the gas stream and is available for reuse in the process that originally generated the pollutant.’
CERL’s says that its device represents a breakthrough in pollution treatment technology. Conventional treatments use granular activated carbon, which is a spherical-like material placed in cannisters. Once it becomes inundated with contaminant, a second step is required to purge it — usually involving steam. Then another procedure must occur to remove water so the carbon can be reused.
According to Hay, the new system is novel because it eliminates the additional steps by collecting and desorbing the HAPs all in the same vessel. ‘Any time you avoid a treatment process, you save money. That’s especially true when the process uses a lot of energy like the current methods do,’ he said.
Besides lowering the cost of treatment in that way, the new carbon fibre fabric system will be more cost-effective because the substrate will not have to be replaced as often. In addition, it achieves a state of purity in emissions that falls well under regulated levels and will avoid fines for non-compliance.
‘We estimate the cost will be 20 to 50% lower to use than conventional pollution abatement methods,’ said Dr. Mark Rood, the University of Illinois professor who co-developed the system. ‘We won’t know for sure until we do the pilot-scale test, but laboratory testing points to significant savings.’ Lab tests focused on capturing methyl ethyl ketone, a common HAP. A pilot-scale device is being developed and will be field-tested in the coming year.