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Gas Turbine TechnologySin Green

n May 2003, Spanish utility IberdrolaGeneracion awarded GE Energy con-tracts to provide 9FB-based combined

cycle power systems for two power pro-

jects in Spain. Just two years later, inAugust 2005, GE Energy announced thatfirst firing of one of the gas turbines hadtaken place, marking the first time that a9FB machine had been fired for a com-mercial project.

The first firing took place at the Arcos dela Frontera Grupo III (Group III) com-bined cycle project in Cadiz, Spain, whereGE Energy has supplied a S209FB multi-shaft combined cycle system consisting oftwo Frame 9FB gas turbines, one D11steam turbine with 48 last-stage buckets,three 330H hydrogen-cooled generatorsand two three-pressure heat recoverysteam generators (HRSGs). The company

has supplied a second S209FB combinedcycle system for Iberdrolas Escombreraspower plant in Murcia, Spain.

The first 9FB at the 800 MW Group IIIplant was fired on August 27 and was syn-chronized to the grid on September 5,with the second unit following soon after.The first firing marked the beginning of atest phase at the Group III site that willlead up to commercial operation by theend of the year.

Located between Sevilla and the Campo deGibraltar two areas with a growingdemand for electricity the Group IIIplant is part of Iberdrolas plans to add1700 MW of new capacity to the Spanishgrid this year. Engineering, procurementand construction (EPC) for the project isbeing carried out by Iberdrolas engineer-

ing subsidiary, Iberdrola Ingenieri yConstruccion SAU (Iberinco).Evolutionary designGE describes the first firing at the GroupIII power plant as a milestone for its9FB technology, which was launched tomarket in mid-2002. The companydescribes the 9FB as one of the worldsmost advanced air-cooled 50 Hz gas tur-

bines. It is the latest evolution in GEsF technology, which has accumulated

more than 13 million hours of commer-cial service around the world.

The 9FB is the 50 Hz version of the60 Hz 7FB gas turbine introduced in1999 the first unit of which was installedat a Reliant Energy project inHunterstown, Pa., USA. Configured withGEs advanced steam turbine technologyin combined cycle operation (one 9FB plusone steam turbine), the 9FB is designed toproduce 412 MW and achieve a net plantefficiency of 58 per cent. By comparison,GEs 9FA gas turbine has a combined cycle

output of 390 MW and a net plant effi-ciency of 56.7 per cent.

The improved output and efficiency hasbeen achieved by increasing firing temper-atures and the use of advanced materials,including those developed for GEs HSystem. The original Frame 7F machine,introduced in 1989, fired at 1260C, whilethe 9FB fires at more than 1370C.

The FB compressor is based closely onthe FA compressor. It is an 18-stage,axial flow unit with variable inlet guidevanes to maintain high part-load effi-ciency and low emissions over a wide

operating range. Variable vanes alsoimprove low-speed surge characteristics,make startups easier, and provide goodpart-load performance in combined cycleapplications. Closing the vanes keepsexhaust temperature up at reduced loads,thus retaining steam-raising capabilitiesif the gas turbine is running at less than100 per cent load.

Throughout the compressor blade path,all airfoil material is high chromium-stain-less steel. While the FA units operate atcompressor pressure ratios of 15.5 to 1,the FB machines run at 18.5 to 1. Thecompressor rotor tie bolts material ischanged to IN718 alloy to provide

improved clamp load for the higher torque

I

We validated output, heat rate, emissions, component dynamics,

aeromechanics, operational clearances, transient operability, and the

controls and accessory operability

The Group III project in Spain is scheduled for start up in early 2006. The 9FB is the latest evolution in GEs F

technology, which has accumulated over 13 million operating hours in projects around the world

Fired up

The first 9FB gas turbine has achieved first firing at the Group III of the

Arcos de la Frontera combined cycle plant in Spain, marking

a milestone in the development of GEs F technology.

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margins of the FB.Compressor bleed air extraction mani-

fold configurations cast into the casingshave been modified to provide bettertransient clearance control to the outercompressor flow path.

Three-stage turbineAn advancement for the FB compared tothe FA series comes in the design of thethree-stage turbine. With the increase infiring temperature, the gas path airfoils forthe FB were redesigned and new materialswere specified. Advanced, three-dimen-sional aerodynamics have been applied tothe turbine design, using computationalfluid dynamics to optimize gas flow, result-ing in higher efficiency and lower coolingair consumption.

The higher firing temperature required

the application of single crystal N5 in thefirst stage bucket, with thermal barriercoating. Second and third stage bucketsare comprised of directionally solidifiedGTD444 materials, replacing the DSGTD111 material of the FA units. Firstand second stage nozzles for the FB utilizeGTD111, while earlier F units used theolder, cobalt-based FSX414.

The GTD111 alloy, originally devel-oped for buckets, offers higher creepstrength and is used in the FB to maintainthe same hot gas path inspection inter-vals of the 7FA. Utilizing high-pressureair supply bled from the compressor, theFB turbine bucket rows 1 and 2 are fully

air cooled, using a combination ofimpingement, convection and filmcooling. A similar system is used to coolnozzle rows 1 and 2.

Since launching the 9FB in 2002, GE hasmade one modification to the units com-bustion system design, says Gregory Beggs,9FB product line manager at GE Energy.

Initially when launched, the 9FB was

fitted with a Dry Low NOx (DLN) 2+combustion system, which had been usedextensively on the 9FA machines. It is nowequipped with a DLN2.6+ combustionsystem, says Beggs.

The DLN2.6+ is a blend of the 9FAsDLN2+ combustion system and the

DLN2.6 system from GEs 7FA gas turbineseries. The 2.6+ design consists of GEspatented swozzle technology a combi-nation of a swirler and a nozzle with anadditional nozzle in the centre. This design

promotes flame stability and improves fuelstaging capability, says Beggs: We took thebest features of both systems and combinedthem for use in the 9FB.

ValidationIn order to fully validate the 9FB unitsat Group III, one of the units was

instrumented with over 1100 gas

turbine sensors and over 300 controls,accessory and packaging sensors. Over170 hours of testing was performed,and validation ended on 22 November2005, says Beggs.

We validated output, heat rate, emis-sions, component dynamics, aeromechan-

ics, operational clearances, transient oper-ability, and the controls and accessoryoperability, says Beggs. Testing was per-formed over the whole operating range ofthe product, from minimum downturn to

baseload. We basically tested for anythingthat the plant might experience under realoperating conditions.

The gas turbines have met all ourexpectations so far, adds Beggs. GE isvery pleased with the product.

A smooth validation and commission-ing period is important for both GEEnergy and Iberinco as the plant is offi-cially scheduled for commercial opera-tion in early 2006. But according toBeggs, validation and commissioning isgoing to plan. Both gas turbines haveachieved full speed full load (FSFL) oper-ation, and the steam turbine has alsobeen operational. Beggs was expecting

the plant as a whole to achieve FSFL inNovember. We will be ready to supplypower to the grid when needed.

One of the 9FB units at Group IIIremains instrumented for validation, anda number of additional activities, includ-ing the reliability run, need to be carriedout at the plant before the PAC is issued,says Beggs.

In addition to supplying the Group IIIand the 815 MW Escombreras combinedcycle plants in Spain for Iberdrola, GE hasundertaken an additional three contractsfor the supply of six 9FB machines inEurope: two in Spain and one in Italy.While the Escombreras plant is slated for

commercial operation by the end of 2006,

The improved output and efficiency has been achieved by

increasing firing temperatures and the use of advanced materials,

including those developed for GEs H System

PEi

Table 1. FB technology: combined cycle performance

50 Hz 60 HzS109FB S209FB S107FB S207FB

Net plant output (MW) 412.9 825.4 280.3 562.5Heat rate (KJ/kWh) 6202 6206 6276 6266Net plant efficiency (%) 58.0 58.0 57.3 57.5Gas turbine 1xMS9001FB 2xMS9001FB 1xMS7001FB 2xMS7001FBSource: GE Energy

The FB consists of an 18-stage compressor and a three-stage gas turbine. Validation of the units at the Group IIIpower plant in Spain was completed in November

Gas Turbine Technology

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