|| NETL scientist Evan Granite prepares for a lab test of the UV mercury removal process.
MORGANTOWN, WV - A promising technology to
remove mercury from coal-fired power plants -- dubbed
the "GP-254 Process" -- has been developed and is
currently being tested at the Department of Energy's
National Energy Technology Laboratory (NETL). Newly
patented, the GP-254 Process enhances mercury removal
using ultraviolet light to induce various components of
power plant stack gas to react with the mercury, and
changes the composition of the mercury into a form that
can be removed easily and economically.
"Coal is one of our most plentiful energy sources in
the United States and provides a strong measure of our
energy security, so we must improve our ability to make
use of this resource in a manner that is both
environmentally sound and economically feasible,"
Secretary of Energy Spencer Abraham said. "The GP-254
Process is an exciting technology that could provide an
elegantly simple solution to a complex problem. Using
equipment similar to that used in water treatment plants
to kill microbes, we may be able to dramatically reduce
the amount of mercury entering the air from power plants
- and it would be inexpensive, benefiting the consumer
and our economy."
When power plant flue gases are exposed to the
ultraviolet light in the GP-254 Process, the elemental
mercury becomes "excited," making it more likely to
react with other compounds in the gas. In laboratory
experiments with simulated flue gas, the excited mercury
reacted with oxygen and sulfur dioxide to form mercurous
sulfate and mercuric oxide, both of which were readily
The process is designed to work with existing
pollution-control devices. Depending on where the
ultraviolet light is applied, it could enhance mercury
removal in the particulate collector or a wet scrubber
of a coal-fired plant. The process could be especially
attractive to power plants that burn "low rank" coals --
softer coals with lower energy content such as
sub-bituminous coals and lignite. Not only do low rank
coals release more mercury per unit of energy than
higher rank coals, but more of the mercury in low rank
coals is harder-to-remove.
"A preliminary cost analysis, based on our
small-scale lab tests, indicates that operating costs
for the GP-254 Process will be lower than those for
other methods," said Secretary Abraham. "Our next step
will be to test and optimize the process at pilot scale
using emissions from NETL's onsite combustor."
Mercury is a naturally occurring element that is
present throughout the environment. Most mercury is
locked up in ores and it rarely occurs free in nature.
Human activities, including municipal waste combustion,
medical waste incineration, and coal combustion, release
some of that mercury. The result is higher amounts of
mercury cycling in our air, soil, and water.
The threat to the environment comes from an organic
form of mercury called methyl mercury. Even when mercury
is released in an inorganic or elemental form,
biological processes can covert it to methyl mercury.
Methyl mercury bioaccumulates through the food chain;
small organisms and plants take up the mercury as they
feed, small animals take in the mercury when they eat
the small organisms and plants, and larger animals take
it in when they eat the small animals. Humans are
exposed mainly from eating fish with high levels of
mercury. Forty-three states have advisories warning
about high mercury levels in fish.
Citing a "plausible link" between emissions of
mercury from fossil fuel-fired power plants and methyl
mercury in fish, the U.S. Environmental Protection
Agency (EPA) announced in December 2000 that it would
regulate emissions from coal-and oil-fired power plants.
EPA is developing a "maximum achievable control
technology" standard that may require as much as 90
percent mercury control. The final regulation is to be
issued by December 2004, with expected compliance by
President Bush called for reductions in mercury
emissions in his Clear Skies Initiative, announced on
February 14, 2002. The initiative calls for phased-in
reductions in mercury emissions from power plants
beginning in 2010, and proposes a cap-and-trade approach
that rewards innovation, reduces cost, and guarantees
results. The Clear Skies Act of 2003, supporting the
President's initiative, was introduced in the House and
Senate in late February 2003. Several other legislative
bills that include regulation of coal-fired power plant
mercury emissions have been introduced in the 108th
session of Congress as well.
Regardless of what form the final regulations take,
the Department of Energy (DOE) is helping to arm the
utility industry with a number of low-cost
mercury-control technologies. DOE's Office of Fossil
Energy has conducted a comprehensive, integrated mercury
research and development program since the early 1990s.
Implemented by NETL, the current Mercury Control
Technology Research and Development Program is
conducting full-scale field testing of mercury-control
technologies, and continuing bench- and pilot-scale
development of a number of novel control concepts,
including the GP-254 Process. The program's plans
include developing technologies that are ready for
commercial demonstration by 2005 and that reduce
emissions 50 percent to 70 percent and by 2010 to reduce
emissions by 90 percent -- all at costs 25 percent to 50
percent less than current estimates.
In his State of the Union Address, President Bush
said that in this century, the greatest environmental
progress will come through technology and innovation. "I
believe this is an excellent example of what he meant,"
Secretary Abraham said.