Conflict has marred the start of commercial operation of the world's largest and most advanced circulating fluidized-bed boilers. Foster Wheeler Energy Corp. last month filed suit against JEA for breach of contract on the Jacksonville, Fla., municipal utility's Northside generating station, where CFB installation was completed this summer. But the project's legal problems do not detract from the accomplishment that the 600-Mw plant represents in the maturing of circulating fluidized-bed combustion technology.

RECORD-SETTING JEA's Northside station claims the world's largest CFB boiler installation. (Photo courtesy of JEA)

Clinton, N.J.-based Foster Wheeler designed and supplied the two 300-Mw CFB boilers and performed engineering, procurement and construction for the boiler island. The new steam generators replaced oil- and gas-fired boilers serving Units 1 and 2, accomplishing a triple play: They increased the plant's power output by 250% and reduced emissions by more than 10%, according to JEA figures, while switching to a combination of petroleum coke and coal, generally considered "dirty" fuels. The U.S. Dept. of Energy's Clean Coal Technology Demonstration Program contributed $72 million of the overall project cost of about $630 million.

The use of solid fuel enables the utility to deliver power to the grid for about 2.33� per kilowatt-hour, or half the cost of the original units operating on oil and gas. Power from a new natural-gas-fired combined-cycle unit also would have cost about 4.5� per kwh, the utility estimates.

The two CFB boilers have successfully operated at full load, and initial performance-test results indicate an ability to meet emissions guarantees on both coal and coke, says Robert Dyr, JEA's project manager for the boiler and air-quality control system. But by integrating state-of-the-art components while scaling up furnace width by one-third, JEA has pushed CFB capacity to perhaps the highest level possible without incurring undue risk, industry observers say.

Foster Wheeler's suit alleges JEA "commandeered" the plant, which was operational but not commissioned, and began commercial operation for summer peak loads. The complaint also states JEA refused to pay $30 million in outstanding invoices. Utility officials could not be reached for comment on the suit.

DEVELOPING. Use of CFB boilers for U.S. utility applications began in the 1980s. Most early units were sized well below 50 Mw, but by 1990 scale-up to about 100 Mw was common. Scale-up continued through the 1990s, nurtured by the Dept. of Energy's Clean Coal and Vision 21 programs.

Scott L. Darling, Foster Wheeler director of CFB proposals, says experience in designing a traditional 1,000-Mw boiler is transferable to CFB design. Success requires paying proper attention to sizing of the furnace and the cyclone separator. It's important to "make sure the cyclone diameter on a large unit is no larger than on your largest successful unit," he adds. Scaling up then becomes an almost modular matter of adding cyclones, rather than scaling them up.

The technology's ability to burn low-Btu, "dirty" fuel efficiently makes it attractive. Following this path, Foster Wheeler has submitted a CFB proposal offering full commercial guarantees up to 460 Mw for a unit using a sub-bituminous-type fuel, Darling says. FW also has participated since 1999 in a comprehensive design study for state-owned utility Electricité de France to develop a 600-Mw CFB. "It's just a natural extension of the 460-Mw approach," Darling says, since it stays within base dimensions of that unit. Neither the process design nor the velocities change, he adds. Click here to view image

The 440-Mw Red Hills Power Project in Choctaw County, Miss., was expected to sport the largest CFBs--250 Mw each--in commercial operation as its December 2000 completion date drew near (ENR 10/9/00 p. 53). But a variety of problems delayed its completion until April 8, 2002, more than 15 months late.

"The boiler works very well. The process is quite functional," says B.H. "Randy" Ransdell, plant manager and director of Choctaw Generation LP. Startup problems have been in areas such as fuel-handling systems, air distribution and areas peripheral to the boilers' operation. With 42% inherent moisture and 5,300 Btu per lb, the lignite fuel is nobody's dream. But "once into the boiler, it's OK," he says. The numbers support him. For November, the average capacity factor through Nov. 20 was 95.9%, and the availability factor was 98.2%.

SQUEEZED Turów boiler retrofits proceeded in confined site. (Photo courtesy of Foster Wheeler Corp.)

Ransdell says scale-up hasn't caused trouble. He is seeing none of the problems with heat absorption, refractory, air flow and other issues that plagued earlier, smaller boilers. "From an installed-cost and life-cycle-cost perspective, CFB is a real good option," especially compared to a conventional pulverized-coal plant, which requires added equipment to control emissions, he concludes.

CFB emissions are cleaned by blending limestone with the fuel for sulfur capture. Air is fed into the boiler to circulate the fuel, which combusts at temperatures below 1,750°F, the temperature at which nitrogen oxides are formed. Clean emissions are one of the technology's strongest selling points.

LOCATION. For Poland's Elektrownia Turów S.A. (ETSA), Bogatynia, CFB was the obvious choice for replacement boilers at its 10-unit plant in the region called the Black Triangle, where the German, Czech and Polish borders meet. Four decades of uncontrolled burning of poor quality coal have made its air the most polluted in all of Europe. There was simply no room to use any technology needing additional flue-gas desulfurization, says Jacek Gadowski, ETSA senior research engineer. "The new plant had to fit into the existing space," he says. ETSA is spending $1.5 billion to modernize the 2,000-Mw lignite-fired Turów station to meet Poland's tough new air-quality laws.

Nine years ago state-owned ETSA planned to replace six of its 200-Mw pulverized coal units. Three others were upgraded and one was destroyed in a fire. ETSA was confident in adopting 230-Mw replacement units, says Gadowski. "Boilers of the size we needed were more-or-less available commercially," he adds. In 1994 ETSA awarded a contract to Zürich-based ABB Group with Finland's Ahlstrom Pyropower, which became Foster Wheeler Pyropower Inc., San Diego, Calif.

With work on the first units ending on time and on budget, ETSA has no complaints, says Gadowski. The CFB conversion has stopped the plant being "very dirty," he says. Design sulfur dioxide emissions of 400-milligrams-per-cu-m are more than 80% below some previous levels, says Gadowski.

Operating experience with the first three units also has been good, says Markku Ruutiainen, Foster Wheeler project manager. After working through normal start-up problems, the 230-Mw retrofits have achieved over 90% availability and met all performance guarantees. The first three retrofits differ from the second three, which are rated 260-Mw each, in the type of cyclone installed. The early units have a "hot" cyclone--a refractory-lined vessel. The steam-cooled cyclone on the later boilers yields greater output with the same footprint.

CEILING. The interest in substantially increasing capacity from the current level is only tentative, says Georg von Wedel, business development manager at Germany's Lurgi Energie und Entsorgung GmbH, Ratingen. Lurgi sees growing interest in coal-fired generation, notably in Asia and Eastern Europe, but von Wedel feels 250 Mw will remain the size ceiling for a while. "We are in a market driven by independent power producers. They don't like to have one big boiler (because) if it goes down, they are going to lose all their revenue," he says.

Jim Wood, president and CEO of Babcock Borsig Capital Corp., Boston, does not see much of a role for advanced technologies in the next round of generation buying. He attributes this to the "perfect storm" confluence of today's risk-averse generation industry, low profit margins for vendors that face significant financial risk related to equipment performance and an illiquid electricity market.

Wood says a lack of development money has hindered further technology advances in recent years. A significant investment would be required to take fluidized-bed boilers to the next level in terms of output and efficiency, he believes. Domestic manufacturers have focused their limited financial resources on emissions-control solutions.

Owners no longer can afford to fund research and development. "Gone are the days when utilities and manufacturers shared risk to develop technologies that reduced the cost, and increased the reliability, of electric supply," says Wood. "Today, manufacturers essentially face construction risk, operating risk, performance risk and maintenance risk alone. And in a market with the opportunity for reward virtually nonexistent, why take that risk?"

But Alstom Power Inc., Windsor, Conn., is undaunted. Richard Skowyra, manager of engineering for CFB performance design, says the firm continues to work on scaling up. It currently is installing two 290-Mw CFBs in Pennsylvania, a 320-Mw unit in Sardinia and others elsewhere. "We're envisioning anywhere between 400 and 600 Mw," he says.

NEXT. "The next step, the way we see it, is to go supercritical," says Skowyra. He notes that the supercritical unit's better heat-rate produces more megawatts for less fuel, further reducing emissions. Alstom now is working in Europe on a supercritical CFB up to 550 Mw, he says.

But the technology has matured in the last five years, he asserts. "The big challenge these days is to control the emissions even closer." In the U.S., even a CFB has to have selective noncatalytic reduction, and quite often polishing scrubbers for additional SO2 removal, he says.

As boilers get larger, systems serving them need more attention too. The growing size of limestone-preparation systems requires the material to be prepared on site, and ash-handling systems are becoming "quite large and complex," he says.