New coal combustor technologies cut pollution and costs


June 26, 2002 — Reducing pollution from the nation’s existing coal-fired power plants may be getting cheaper and less complex.

Two new, high-tech coal combustor improvements introduced recently at a Department of Energy technology conference offer the potential for cutting smog-forming emissions to levels that rival more complex chemical devices now being installed on many coal-burning plants.

Equally important, these advanced technologies also could cut the cost of reducing the pollutants by at least 25 percent – an economic benefit that could make them key tools in meeting President Bush’s Clear Skies Initiative.

The President has proposed major reductions in power plant emissions while, at the same time, encouraging utilities to use the most cost-effective, innovative technologies possible.

Alstom Power Inc. and Praxair, Inc., both participants in the Energy Department’s coal research program, developed the new combustion systems in independent projects. Each company presented results from their pilot tests at a recent conference on nitrogen oxide controls conducted by the National Energy Technology Laboratory, the government’s lead center for advanced fossil energy technology.

“These new technologies cut both pollution and cost – a powerful combination,” said Mike Smith, the department’s Assistant Secretary for Fossil Energy. “They illustrate a basic premise of the President’s environmental policy, namely that technological advances can give the American people cleaner air without sacrificing economic growth.”

Both combustor systems employ innovative modifications to low-NOx burner technology. Low-NOx burners – so-named because they lower the levels of nitrogen oxides (NOx) emitted when coal is burned – have become standard for many utilities due, in large part, to the Energy Department’s Clean Coal Technology Program of the 1980s and early 1990s.

Conventional low-NOx burners reduce nitrogen oxide pollutants by 40 to 45 percent at relatively low costs. But as emission limits have become more stringent in many States, many utilities are being required to install more expensive pollution controls that cut emissions even more.

To achieve the necessary emission reductions, power generators are turning to the current state-of-the-art NOx control technology called “selective catalytic reduction” (SCR). Rather than reducing NOx in the combustion zone, SCR uses chemical catalysts to scrub NOx pollutants from a power plant’s flue gas before it is expelled from the plant.

SCR can meet the most stringent emission limits set by federal and state standards – 0.15 pounds of NOx per million Btus (“Btus” are a measure of the fuel’s energy value). But SCR adds a complex and expensive chemical plant to the power station.

Now, the new-generation low-NOx technologies developed by Alstom and Praxair can in many cases achieve the aggressive NOx reduction required to meet these same stringent emission limits. Like conventional low-NOx burners, however, the NOx is reduced inside the combustor not in a separate chemical plant, resulting in a less complex and lower cost power plant.

The Alstom combustion system uses advances in control systems, combustion process modifications, and special”carbon burnout” technology to lower the formation of NOx. The Praxair technology enhances the combustion process with oxygen which improves NOx reduction compared to burners using only air.

The next step will be to demonstrate both combustion systems in full-scale, multiple-burner configurations at sizes typical of larger commercial power plants.

According to Smith, the advanced combustion systems and other clean coal technologies can have a major impact on the future cost of electricity. “Abundant, affordable coal is one of the reasons U.S. consumers benefit from some of the lowest cost electricity of any free market economy,” Smith said.

“The President has set the nation on the path toward cleaner air, but that doesn’t mean we have to abandon coal. Because of new technologies like these high-tech combustion systems, we can continue to benefit from the low-cost power supplied by coal while we continue to clean our air. That’s good for the environment and good for the economy.”

The Praxair burner was co-funded by the Energy Department in cooperation with the University of Utah, The University of Arizona, Reaction International Engineering Inc., and Alstom Power Inc. The ALSTOM project, also co-funded by the Department of Energy, included participation from Progress Materials, Inc. and Kennecott Energy Co.

Praxair is located in Danbury, CT, while Alstom is headquartered in Windsor, CT.


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