KING GEORGE, VA - Each year Mirant's Birchwood
Power Facility in King George, VA, pays to have more
than 100,000 tons of coal combustion ash disposed of in
a municipal landfill. A new Department of Energy project
may soon demonstrate that this ash has significantly
more value than as the daily cover material for a
community's solid waste.
The department recently signed a cooperative
agreement with Universal Aggregates, LLC, of
Bridgeville, PA, to design, construct and operate a
manufacturing plant at the Birchwood Power Facility that
will turn the ash into lightweight aggregate that can be
used to make a variety of construction materials, from
masonry blocks and concrete to asphalt paving material.
Construction of the plant is expected to start within
the next two weeks, and the facility is scheduled to
begin operating in 2004. The federal government will
provide $7.22 million of the 30-month project's $19.58
million cost. A formal groundbreaking ceremony is
planned for early spring.
The project could pave the way for a new type of
recycling technology for coal-burning power plants. Ash
for Universal Aggregates project is produced as a
by-product of the power plant's "spray dryer" scrubber
system. Scrubbers are used on many coal-fired power
plants in the United States to reduce sulfur pollutants,
but currently less than 20 percent of the 28 million
tons of residue produced annually by these scrubbers is
reused and most of that is from "wet" scrubbers.
As new environmental standards take effect, power
companies are expected to install more scrubbers,
including the "spray dryer" technology used at the
Mirant plant that produces a dry by-product rather than
a wet residue. While air quality will improve, scrubber
waste tonnage will inevitably increase, placing greater
burdens on landfills and adding increasing waste
disposal costs to consumers' electric bills.
The Universal Aggregates process is designed to
recycle the by-products from either wet or dry
scrubbers, thereby lowering the costs of waste disposal
while reducing the environmental drawbacks of
In the process, ash from the spray dryer and other
solid wastes from the power plant are blended in a mixer
to produce a uniform granular material. The loose, moist
material is then fed to an extruder that further mixes
the material, then forces it through the holes of a
metal die to form wet "green" pellets. The soft pellets
are dried and hardened in a curing vessel specially
designed to allow the solids to continue flowing without
After curing, the hardened pellets are crushed and
screened to specification, then stockpiled for sale as
manufactured aggregates. Once in operation, the project
will produce 167,000 tons of aggregate a year. The
construction aggregate market in the United States is
estimated to be about two billion tons annually.
The Birchwood Power Facility project will be the
final step to verify that the aggregate manufacturing
process and equipment is ready for future commercial
use. Currently there are 21 spray dryer facilities in
the United States that produce an adequate amount of
by-product to economically justify the installation of
similar aggregate manufacturing facilities.
Prior to the current project, the technology was
tested at a six-ton per day pilot plant at CONSOL Energy
Inc.'s Research and Development Campus in South Park,
PA. Universal Aggregates is a joint venture of CONSOL
and SynAggs, LLC, a Pittsburgh, PA-based company.
P.J. Dick, Inc., of West Mifflin, PA, will serve as
the engineering and construction contractor for the
Birchwood Power Facility project.
The project is one of six demonstration projects
funded by the Energy Department as part of its "Power
Plant Improvement Initiative." Begun in late 2000, the
initiative provided federal matching funds to projects
that would use innovative technology to enhance the
environmental or operating performance of coal-fired
power plants. The effort served as the precursor to
President Bush's expanded program to develop even more
advanced clean coal technologies for the nation's power
The Universal Aggregates project is being managed by
the Energy Department's National Energy Technology
Laboratory, the major technology arm of the department's
Fossil Energy research and development program.