Industry publication, December 2001

NYC 9/11 Public Portal Document

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Gas Turbines Continue To Dominate New Construction I « Low emissions and lower building costs are still decisive l^ven as consensus emer- ges that only about half few of all planned power­ plant projects will ever get WJLi past an artist’s rendering, sales of gas-turbine plants, in both simple and combined cycle, are expected to remain high, soaring above compet­ ing technologies. But proj­ ect completion will be limit­ ed by constraints in natural­ gas pipelines, high-voltage transmission systems, site permitting, equipment man­ ufacturing and skilled labor, among other factors. J In simple cycle, high-tem­ I perature gas turbines offer quick construction, low emis­ sions and rapid start-up ca- t pabilities for peaking ser­ vice. Coupling the GT to a heat-recovery steam genera­ tor (HRSG) and steam tur­ bine for combined-cycle RI- EFFICIENT Simple- and combined-cycle plants rule market. (CC) operation yields the ; highest thermal efficiency of | low-nox (DLN) com- backpressure from the SCR reduces the all electric generating sys­ bustors. DLN com- gas turbine’s fuel efficiency. tems commercially available bustors lower the F-class GTs have demonstrated low today, cc-plant capital costs, peak flame tempera- emissions and high efficiencies, but also although rising, remain low­ ture—and thus NOx problems meeting reliability and dura- er than new nuclear and emissions—by burn- bility expectations in the field. The prob­ coal-fired projects, and sub­ ing a leaner mixture lems span all manufacturers, and include stantially lower than renew­ of fuel and air. failed tie bolts, inadequate rotor stiffness, able energy projects. More advanced fatigue failure of turbine blades, flash- DLN offerings reduce backs in the DLN combustors and spiral- DOMINANT NOx emissions to 15 ing operation and maintenance costs for Four models of advanced GT parts per million or prematurely failed hot-section compo- dominate today’s North less throughout the nents. American market. Siemens entire load range Lingering problems have dogged the J Westinghouse Power Corp., with the addition of GT24, which took a different road from Orlando, Fla., makes two—the V84.3A selective catalytic reduction (SCR) sys- competing models toward high thermal and 50IF. Paris-based Alstom supplies the terns. But most new combined-cycle GT efficiency. Instead of a higher firing tern- GT24, and GE Power Systems, Schen­ projects today are required to meet a 2- perature, the GT24 uses a “sequential I ectady, N.Y, sells the 7FA, recently updat­ or 3-ppm NOx limit. This has increased combustion” system to gain efficiency. ed with the 7fb. Each of these, with capital costs of CC plants because owners Similar to a Rankine-cycle steam

□ orders backlogged for several years, has have to purchase the expensive DLN plant’s reheat cycle, the unique sequen­ demonstrated efficiency levels greater combustors plus an SCR. It also has tial combustion system heats die working than 55% in CC application, based on increased production costs because users fluid—in this case, the combustion air— lower heating value (LHV). Each also has must purchase, store and handle ammo- in two intervals. The GT24 comprises two demonstrated low air emissions using dry nia consumed in the SCR, and because annular combustors located in series: the

POWERPLANT CONSTRUCTION«3S

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