WASHINGTON, DC -
Developed with funding from the U.S. Department of Energy (DOE), a novel approach
to improving coal-combustion fly ash was successfully tested at near full-scale
levels. Easily integrated with existing ash handling equipment, the simple-to-operate,
cost-efficient technology can be retrofitted to existing coal-fired power systems
to generate a safer, marketable by-product.
The technology is an alternative to current ash beneficiation processes?treatments
used to improve the physical and chemical properties of fly ash. The innovative
ozonation process blends the ash with ozone to render its carbon particles inactive
and results in improved ash quality that meets concrete manufacture specifications.
Once destined for landfill disposal or mine reclamation efforts, the improved
fly ash could soon find a permanent niche in the concrete marketplace.
"One of the biggest challenges to fly ash utilization is managing the unburned
carbon content," explains Robert Patton, project manager at DOE's National Energy
Technology Laboratory (NETL). "By exposing the ash to ozone in a contained unit,
we can improve the ash to the point of being a useful product that eliminates
the carbon's negative impact during concrete production."
Used as a replacement for Portland cement in the production of concrete, the
fly ash can reduce carbon dioxide emissions by approximately one ton for
each ton of ash used. This is a significant benefit in addition to the inherent
economic and environmental value of reusing the ash.
The ozonation technology was demonstrated at PPL Generation's Montour Steam Electric
Station in Montour County, Pennsylvania. Tested at almost full-scale levels of
10 tons per day, the ozonation treatment was successful on various ashes, including
low-carbon and activated-carbon-contaminated ashes.
"Over the last few years, we've been losing ash sales due to deteriorating quality," said
Larry Labuz, manager of ash operations for PPL. "The ozonation process provides
an alternative to treating our fly ash, making it suitable for the concrete marketplace
again?an obvious value for us."
Following the demonstration at PPL's Montour plant, technical and economic analyses
were conducted for full-scale, commercial design of the technology. While the
technology is financially advantageous over typical disposal options, results
also show that it is cost competitive with existing ash beneficiation processes
by a difference of up to $15 per ton of treated ash. Finally, the simple nature
of the ozonation technology and the ease with which it can be integrated into
existing systems could potentially reduce costs even further.
The technology behind the ash ozonation process began as bench-scale work in
2000 when DOE partnered with Brown University and the Electric Power Research
Institute (EPRI) to conduct research on alternative ash beneficiation processes.
The team at Brown discovered that oxidizing carbon surfaces suppresses the adsorption
of surfactants used in concrete, the most important carbon-related restriction
on fly ash use in concrete production. Subsequently, DOE and EPRI funded bench-
and pilot-scale experiments prior to the recent demonstration at PPL.
The ozonation demonstration project was funded under NETL's Water and Environmental
Resources program, created to develop retrofit environmental control technologies
for existing power plants, with application to new plants as well.