In the Lab

• By Heida Diefenderfer
• Jun 01, 2002

New Low-emission Combustion Method

LIVERMORE, Calif. -- Engineers from the Lawrence Livermore National Laboratory (LLNL) have developed a combustion method that results in lower power plant pollutant emissions by combining stage-combustion with nitrogen-enriched air.

The new technology, Staged Combustion with Nitrogen-Enriched Air (SCNEA), could help power plants comply with strict U.S. Environmental Protection Agency (EPA) requirements for decreasing plant emissions.

"As EPA requirements become tighter and tighter on emissions, most solutions become more difficult and more expensive to implement," said Larry Fischer, LLNL principal investigator for SCNEA. "With our technology, consumers will see cleaner air at a miniscule increase in their utility bills."

Before concerns about oxides of nitrogen (NO and NO₂) and their relationship to photo-chemical smog and acid rain came to light in the late 1980s, fuel was typically burned in boilers and furnaces with single-stage combustion using air as the oxidant stream.

NOC emissions are regulated under the provisions of the Clean Air Act and its 1990 amendments. Those requirements demand that dry bottom wall-fired boilers can emit no more than .50 lbs. of pollutants per million British thermal units (Btu - a measurement of energy) and that tangentially fired boilers can emit not more than .45 lbs. of pollutants per million Btu. To date, low-NO_X technologies, including low-NO_X burners, overfire air and reburning, have been used to reduce NO_X production in coal-fired boilers. But they must reach significantly lower emission levels required by 2005.

Fischer said SCNEA is expected to lower corrosion and slagging rates extending the lifetime of equipment and decreasing down time and maintenance costs in power plants. He estimates that a 350-megawatt coal-fired boiler plant would cost about $60 million to retrofit for SCNEA operation.

The SCNEA combustion method burns fuels in two or more stages, where the fuel is combusted fuel-rich with nitrogen-enriched air in the first stage, and the fuel remaining after the first stage is combusted in the remaining stage(s) with air or nitrogen-enriched air. "You get the NO_X reduction, but you're not taking a significant hit in efficiency (energy output) of the power plant," said Kevin O'Brien of New Business Development in the Engineering Directorate.

This method substantially reduces the oxidant and pollutant loading in the effluent gas and is applicable to many types of combustion equipment including boilers, burners, turbines, internal combustion engines and many types of fuel including coal, oil and natural gas.

Livermore is working to form a consortium of representatives from the EPA, utility companies, boiler manufacturers, emission control equipment companies and a company that produces nitrogen-enriched air. The next stage is to do a small-scale pilot program.

Founded in 1952, LLNL is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. It is managed by the University of California for the U.S. Department of Energy's National Nuclear Security Administration.

For more information, visit www.llnl.gov/PAO.

ORNL Technology Gets Nod from EPA

OAK RIDGE, Tenn. -- Prospects for cleaning up contaminated sites around the country are better because of a technology and procedure developed at the U.S. Department of Energy's (DOE) Oak Ridge National Laboratory and recently accepted by the U.S. Environmental Protection Agency (EPA).

The technology, which consists of direct sampling and analysis of volatile organic compounds in water, soil, gas and air, requires little if any sample preparation and yields results in three to five minutes. Compared to conventional approaches, the method saves time, money and allows more sites to be tested -- and ultimately decontaminated.

"EPA's official acceptance of this method should accelerate its adoption by the regulatory community," said Roger Jenkins of the Chemical Sciences Division. "Before that happened, there would have been only modest interest in using this procedure to support on-site characterization and remediation."

With direct sampling ion trap mass spectrometry, the person conducting the test introduces sample materials directly into an ion trap mass spectrometer through a simple interface. No chromatographic separation is required, and the response of the instrument is nearly instantaneous. EPA's new Method 8265, developed by ORNL, embodies this technique.

"The implication of the EPA's having made this direct sampling and analysis methodology an official method is that regulators are now much more likely to accept this new rapid method performed in the field as being 'just as good' as a standard fixed laboratory procedure," said Marcus Wise, a scientist in ORNL's Chemical Sciences Division and one of the developers of the instrument and methodology. "With the budget constraints, it has become increasingly important to develop and deploy innovative technologies for faster and less expensive approaches to restore the environment."

Tri-Corders Environmental of McLean, Va., has licensed the technology from ORNL and is building transportable instruments for on-site use. Environmental and analytical companies will benefit, as will the government and private sectors. Perhaps most importantly, researchers at ORNL note, the public will benefit because sites will ultimately get cleaned up more quickly, thus lowering both risk and cost to the public.

Aside from the speed afforded by this process, the new method allows for samples, such as water, to be analyzed without having to remove them from the site. That simplifies testing and lowers the cost. And the new test protocol eliminates the problems associated with drawing samples, shipping them, and logging those samples and results.

"When you have to move samples off site, there are just that many more opportunities to make mistakes," Jenkins said.

In addition to environmental screening, a number of direct screening methods are being explored for detecting hidden explosives, chemical and biological warfare agents on the battlefield, and contaminants in food and agricultural products, Wise said.

ORNL's efforts to develop the technology and methodology began in the late 1980s through a U.S. Department of Defense project. In recent years, DOE also has funded some of the work that has resulted in EPA Method 8265 (www.epa.gov/epaoswer/hazwaste/test/new-meth.htm).

Researchers playing key roles in developing the technology and working with EPA to get it accepted were Marc Wise, Mike Guerin, Cyril Thompson and Roosevelt Merriweather.

ORNL is a Department of Energy multiprogram research facility managed by UT-Battelle.

This article originally appeared in the June 2002 issue of Environmental Protection, Vol. 13, No. 6, p. 12.

This article originally appeared in the 06/01/2002 issue of Environmental Protection.