Features. Conference Report: NOx, SO3 in the spotlight at NETLNETL's 2006 Environmental Controls Conference

Power, Feb 2007 by Mann, Alfred N, Makovsky, Leo E, Inc, Management Services, Sarkus, Thomas A, Laboratory, National Energy Technology

face= Italic; As emissions caps drop, technological solutions must become increasingly effective and efficient. Researchers, equipment vendors, and plant operators are exploring alternatives to SCR and SNCR, with a view to reducing the overall costs of NOface= Subscript; xface=-Subscript; reduction. They've also achieved 95% to 99% removal of SOface= Subscript; 3face=-Subscript; , with no visible plume opacity.face=-Italic;

By Alfred N. Mann and Leo E. Makovsky, Technology & Management Services Inc., and Thomas A. Sarkus, National Energy Technology Laboratory

In May 2006, the National Energy Technology Laboratory (NETL) of the U.S. Department of Energy's (DOE) Office of Fossil Energy sponsored a two-session Environmental Controls Conference (ECC 2006) in Pittsburgh, Pa. The event was cochaired by Tom Sarkus, director of NETL's Advanced Energy Initiatives Division, and Ron Cutright, director of NETL's Major Projects Division.

The first ECC 2006 session focused on selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR) control of various nitrogen oxide (NOface= Subscript; xface=-Subscript; ) emissions. SCR and SNCR--the primary technologies currently available commercially for achieving significant reductions of NOface= Subscript; xface=-Subscript; in flue gas--rely on reacting flue gas with a reagent (usually ammonia or urea) to produce environmentally benign nitrogen and water.

Conferences on SCR/SNCR have been organized and conducted by NETL nearly every year since 1997. The second ECC 2006 session addressed the related issue of reducing stack emissions and flue gas concentrations of sulfur trioxide (SOface= Subscript; 3face=-Subscript; ). It was the second NETL meeting on that subject; the first was held in 1998.

face= Bold; SCR/SNCR workingface=-Bold;

Carl Bauer, NETL director, gave the keynote address of the SCR/SNCR session. He began by reminding the audience how much America relies on coal-fired power. The U.S.--which has 27% of the world's proven coal reserves (an estimated 496 billion short tons, enough to last several hundred years)--currently gets about half of its electricity from coal. Because coal is forecasted as the cornerstone of America's energy future, in partnership with industry, the DOE is developing advanced technology to provide cost-effective solutions to environmental concerns.

Based on past performance, there's ample reason to believe that the technical community can deliver these solutions. SCR/SNCR technologies (among others) have proven capable of enabling any coal plant--new or existing--to operate as cleanly as a natural gas-fired plant, with respect to NOface= Subscript; xface=-Subscript;

Since passage of the Clean Air Act in 1970, emissions have declined for virtually every pollutant monitored by the U.S. Environmental Protection Agency (EPA). In particular, sulfur dioxide (SOface= Subscript; 2face=-Subscript; ) emissions have decreased 35% and emissions of fine particulate matter (PM10) have fallen 87% over the period, even as electricity production has risen 177% (Figure 1). The DOE has contributed toward this success by funding demonstrations of advanced SOface= Subscript; 2face=-Subscript; scrubbers, a variety of NOface= Subscript; xface=-Subscript; control technologies, air toxics and mercury (Hg) characterization studies, and clean-coal generation technologies. Building on this applied research, SCR systems will continue to be deployed domestically and worldwide.

face= Bold; Tough row to hoeface=-Bold;

At ECC 2006, Meg Victor of the EPA predicted that some areas of the U.S will have difficulty coming in under current caps on NOface= Subscript; xface=-Subscript; emissions. As those caps are ratcheted down by implementation of the Clean Air Interstate Rule (CAIR), the Clean Air Visibility Rule (CAVR), and the future Clean Air Mercury Rule (CAMR), additional postcombustion controls on coal-fired plants will be needed, she added.

Complying with the progressively tighter limits of those three rules will require one of the largest investments in pollution control technology in history. The CAIR, CAVR, and CAMR standards will ultimately reduce SOface= Subscript; 2face=-Subscript; and mercury emissions by more than 70% and NOface= Subscript; xface=-Subscript; emissions by more than 60%, relative to 2003 levels (Figure 2). CAIR's Phase II cap of 1.3 million tons/year on NOface= Subscript; xface=-Subscript; will restrict power plant emissions of the pollutant to an equivalent limit of 0.125 lb/mmBtu. Significantly, the new limit will be applicable year-round, not just during the five-month summer ozone season, as is the current 0.15 lb/mmBtu limit on NOface= Subscript; xface=-Subscript;

face= Bold; SCR operating experienceface=-Bold;

To kick off the SCR/SNCR session, Anthony Licata of Babcock Power Environmental Inc. and Clayton Erickson and Robert Lisauskas of Riley Power Inc. summarized the current status of SCR technology and projected likely future developments. Retrofits of older, smaller power plants may be more difficult to make, they said. To meet permitted limits, NOface= Subscript; xface=-Subscript; levels may have to be reduced 90%, SOface= Subscript; 3face=-Subscript; emissions will have to be cut, and releases of mercury will have to be minimized. Those challenges were discussed in subsequent papers.