JACKSONVILLE, FL — Recent tests with one of the nation's mid- to high-sulfur coals have further verified that a new electric generation technology in its first large-scale utility demonstration here is one of the world's cleanest coal-based power plants.
This city's municipal utility JEA logged the achievement at its Northside Generating Station using Illinois No. 6 coal in a 300 megawatt demonstration of circulating fluidized bed (CFB) combustion, which is the largest application yet of the new form in the United States. It almost triples the size of a previous demonstration and scales up the technology to the sizes preferred for adding new plants and replacing old ones, also called repowering.
Northside eliminated more than 98 percent of sulfur emissions and held them to measured levels as low as 0.08 pounds per million British thermal units of fuel use. At this level, SO2 emissions were 94 percent below the general limits set for high sulfur coal in federal law and regulation and almost 50 percent below project design limits. All other emissions were also under the levels set either in design or by federal law and regulation.
Specific measured achievements included nitrogen oxide emissions as low as 0.086 pound per million Btus, which was 40 percent under the regulatory limit of 0.15 pound and almost 5 percent below design; and particulates at 0.0019 pound per million Btus, which was almost 94 percent under the regulatory limit of 0.03 pound and almost 83 percent below design. Regulatory and design limits were also bettered for carbon monoxide and volatile organic compounds. The "full-load" results with the Illinois coal were obtained in the third of four testing periods.
The JEA demonstration proved ultra-clean in the three other tests as well. Similar results were obtained with Pittsburgh No.8 coal and with another solid fuel called petroleum coke, which is the residue left from oil refining. The latter was burned in blends with coal of 50 and 80 percent petcoke. The results of a fourth testing period are in preparation. Detailed results of all tests will be combined and published this spring in a final demonstration report.
A part of the Department of Energy's Clean Coal Technology Demonstration Program, the JEA project is a repowering demonstration. It replaced older, less-efficient natural gas and oil generation. It takes the relatively new CFB technology to utility scale and shows that it can offer electricity producers the flexibility to use a variety of fuels, including abundant mid- to high-sulfur coal, while elevating emissions capture.
Winner of Power magazine's Plant of the Year Award in 2002, the 300 megawatt demonstration has a non-demonstration twin, and together they deliver 600 megawatts of baseload power. The demonstration unit is a cost-sharing effort of the federal government, the utility and other parties, but the second unit had no federal financing. The two advanced combustors are the largest fluidized-bed units ever installed in a power plant and together can deliver enough power to light approximately a quarter-million homes.
The JEA demonstration is to evaluate the operational and environmental performance of the Foster Wheeler Energy Corporation's CFB technology. The process uses a crushed limestone sorbent to capture the first 90 percent of the sulfur during combustion. Sorbent is added to the coal as it enters the combustor. In the combustor, the coal and limestone move in a fluid motion, hence the name "fluidized bed," and the coal burns at a temperature low enough to limit formation of the pollutant NOx. As the coal particles become smaller, they move higher in the combustor; then the introduction of secondary air produces even smaller coal particles; and these particles move out of the combustor, along with some of the sorbent, to be collected in a cyclone separator and recycled into the lower combustor.
Northside elevates the pollution control capabilities of the basic technology by adding steps specific to Jacksonville's locale and concerns. Added features include fabric filters to capture solid fly-ash particles and a polishing scrubber to achieve 98 percent SO2 removal.
The extra steps stem from Northside's location; it is on the St. John’s River amid one of the last unspoiled coastal wetlands near the Atlantic coastline – an ecological wonderland of salt marshes, coastal dunes, and hardwood stands inhabited by animal life and native vegetation. To ensure the stability of the ecosystem, JEA conferred with community and environmental groups to ultimately set emission limits significantly lower than even those directed by existing U.S. Environmental Protection Agency regulations.
Circulating fluidized bed combustors are relatively new to the electric power industry. They promise lower capital costs, lower pollution-control costs, better pollution control, fuel flexibility and higher combustion efficiency. Those qualities translate into moderate electricity costs for consumers.
While conventional coal-fired plants required expensive add-ons to clean pollutants from flue gases after combustion, fluidized-bed technology captures most of them inside the boiler during combustion.
Circulating fluidized bed technology is an integral part of DOE’s Clean Coal Technology Demonstration Program, created in 1985 to develop innovative, environmentally friendly coal utilization technologies. During the past two decades, the program has nurtured 35 projects that have collectively resulted in a suite of clean coal technologies capable of meeting current and future environmental regulations.