|Supersize That. Wisconsins 80-ton feedwater heaters are much larger than a subcritical powerplants. (Photo courtesy of Black & Veatch)|
Renewed interest in coal "is clearly driven by fuel-cost issues," says Gregory A. Anderson, executive vice president of fossil-power technologies for Sargent & Lundy LLC, Chicago. The firm is analyzing a variety of coal-generation technologies for several utilities. "If they can close old [simple-cycle] gas-fired generation, they will do it now," he says.
Clean coal technology helps overcome community resistance to coals emissions. "Coal is a four-letter word," says John Thompson, advocacy coordinator for Boston-based Clean Air Taskforce, an environmental group. "If we dont radically change the nature of how we use coal, our options for global warming are going to be zero. Particulates and global warming are the main concerns in this century."
Many environmental activists still call "clean coal" an oxymoron. But as a baseload fuel, "coal is not a good thing or a bad thing; its just a reality," Thompson says.
Clean or advanced coal technologies increase energy efficiency and reduce flue-gas emissions while generating electricity from coal (see related story). Gasification allows separation of impurities before combustion, while circulating fluidized-bed and supercritical pulverized-coal processes cut emissions in the combustion cycle. Now, tested and demonstrated, they are moving toward commercial operation. Click here to view chart
Powerplant owners and researchers, pursuing the goal of near-zero emissions and higher efficiency, are pushing still others through the development pipeline. The $1-billion FutureGen program, using $650 million in Dept. of Energy funds to build the worlds first powerplant with near-zero emissions, took a major step forward in September with the formation of an alliance to develop the project (ENR 10/3 p. 22). In mid-November, DOE selected two other projects valued at nearly $10 million to demonstrate "oxycombustion," a carbon-capture technology that combusts coal with oxygen instead of air. Observers expect these pilot technologies to become commercially viable over the next 10 years as more stringent environmental regulations reduce marginally higher costs over conventional powerplants.
|Material Success. New alloys stand up under supercriticals high temperature and pressure conditions. (Photo courtesy of Hitachi America Ltd.)|
After a lengthy period of slow growth, the U.S. electric system from 1999 to 2004 grew by 25%, adding more than 200,000 MW of generation capacity. Most of these new plants burn natural gas, which was cheap, easy to permit and burns cleaner than coal. In 2003, DOEs Energy Information Administration forecast that by 2025, 74,000 MW of new coal capacity would be added to the nations generation capacity, making up 17% of projected new capacity. Two years later, EIA is forecasting 87,000 MW of new coal capacity by 2025. Coals proportion of projected total new capacity is up to 33% by 2025. Even more striking, 18,154 MW now proposed would use advanced coal technology. Click here to view map
Many environmentalists consider gasification the best use of coal for generation. With gasification, sulfur dioxide (SO2), carbon dioxide (CO2), mercury and oxides of nitrogen (NOx) are stripped from the synthesis gas stream before combustion. "We have all the technology to isolate CO2 from syngas commercially demonstrated and ready to operate today," Thompson.
The Clean Air Interstate Rule, issued last spring by the Environmental Protection Agency, will make massive cuts in SO2, NOx and fine particulate (PM) levels. Affecting 28 states in the eastern U.S. and the District of Columbia, it will cut NOx by 68% in 2009 and by 72% in 2015 from its current allowable average level of .46 lb per million Btu of coal fired.
Emission allowances for SO2 under the cap-and-trade program will fall by 50% in 2010 and 65% in 2015 in the affected region. Particulate rules are still being discussed, but the regulation of SO2 and NOx will dramatically reduce particulates because those compounds react with other matter in the atmosphere to form fine particulates, says Gary Brown, senior technologist in the air quality group of CH2M Hill Cos. Ltd., Denver.
Despite President Bushs 2001 rejection of the Kyoto Protocol, a large number of U.S. industrial companies assume regulation is inevitable and have joined the Chicago Climate Exchange, a market for carbon-emission allowances.
Current and anticipated emission regulations are still forcing generators using subcritical pulverized-coal to add to capital costs with back-end equipment like scrubbers, selective catalytic reduction and baghouses or electrostatic precipitators. Even power developers using advanced coal technologies, which already have lower emissions than subcritical systems, must add the equipment to achieve permitted emission levels. Click here to view chart
"We dont see supercritical costing us more. If we do, itll be 1 to 3% [capital cost], but we would offset it in operating cost," says Marty Swartz, project director of the supercritical Granite Fox Power Project. IGCC capital costs, in contrast, are 25% more, and operating costs are 100% more, he says. "The gasifier requires a lot of maintenance," he notes.
Granite Fox Power LLC, a wholly owned subsidiary of San Diego-based Sempra Generation, is proposing a two-unit, 1,450-MW supercritical PC powerplant in Gerlach, Nev., costing an estimated $2.5 billion. "Theres a lot of environmental pressure to reduce CO2 emissions," says Swartz. Supercritical PC overall emissions are lower because supercritical combustion is more efficient than subcritical. It uses less fuel.
If the permits are in place in early 2007, as scheduled, construction would begin soon after, aiming for completion in 2011 for both units, Swartz says.
|In the Game. Circulating fluidized-bed (left) and IGCC are two clean coal technologies with near-term promise.|
Many supercritical plants have been constructed in Europe, South Korea and Japan, where high fuel costs made their efficiency especially attractive. But Barberton, Ohio-based Babcock & Wilcox Co. claims the first supercritical system, a 125-MW universal-pressure boiler built in 1957 for Ohio Power Co. More than 150 supercritical plants were built in the U.S. in subsequent decades, but the generation market became overbuilt and faded about 1980. Advances in metallurgy since then have made the technology more reliable.
A bad experience with early generations of supercritical technology in the U.S. left "a sour taste," says Ray Kowalik, vice president and general manager...oal is returning to favor as a powerplant fuel, driven by rising electricity demand and rising costs for competing fuels. As utilities and private-power developers seek to get ahead of the next surge in powerplant construction, they are proposing, in record numbers, plants using technologies that reduce coals notoriously dirty emissions. Coal-fueled powerplants that produce near-zero emissions also are coming, thanks to intensive public and private research programs.