Vogt Hsrg Stig-equipped Lm6000 Vpi-mg-0007

7/21/2019 Vogt Hsrg Stig-equipped Lm6000 Vpi-mg-0007

1/564 COMBINED CYCLEJOURNAL, Third Quarter 2010

WESTERN TURBINE USERS

It is oft said that if youre standingstill youre falling behind. Thatscertainly true in the competitive

power generation business. Competi-tors with later-model gas turbines, forexample, almost surely can producemore power more efficiently and oper-ate more reliably than you can. Andprobably ramp faster, too.

Consider GE Energys LM5000aeroderivative gas turbine, no lon-ger in production. Wear and tear indemanding industrial service hasadversely impacted the reliability ofsome engines. With the cost of sparesincreasing and their availability some-times questionable, at least a few own-ers are considering upgrades to theLM6000. This is not news; 10 LM5000shave been replaced with LM6000ssince the first conversion was com-pleted in December 1999 for OildaleEnergy LLC, Bakersfield, Calif, byEnergy Services Inc, Farmington, Ct.

But until now, there was not anLM6000 replacement for LM5000engines equipped with steam injec-tion for power augmentation. Recallthat LM5000s were offered both withand without STIG, the acronym forsteam-injected gas turbine. Perhapshalf the engines purchased wereSTIG-equipped. Of the 50+ LM5000sstill in service, half have STIG.

GE told the editorsabout theSTIG-equipped LM6000-PC at the

Western Turbine Users Inc annualconference last spring and announcedthat the first unit would be installedat Capital Power Corps EF OxnardLLC facility in California. That projectstarted March 1 and was completedin mid May.

The editors waited about sixmonths before calling Capital Power,a major player in the North Americanindependent power business with adiverse portfolio of nearly three dozengenerating units totaling more than3500 MW.

Discussions with Dave Sweigart,

GM of Capital Powers Californiaassets (including LM2500, LM6000,and Frame 6 gas turbines) and SusanRichards, senior manager of optimiza-tion engineering for US plants werefollowed up with interviews of engi-neers at GE and Vogt Power Interna-tional Inc, Louisville. Vogt upgradedthe original heat-recovery steam gen-erator (HRSG) to meet STIG systemrequirements for the LM6000.

Sweigart first provided backgroundinformation on the plant. EF Oxnard,he said, produces electric power for

Southern California Edison Co (SCE)and supplies steam to an absorptionrefrigeration system that providescool to thermal host BoskovichFarms Inc, a large producer and pack-ager of produce.

As originally configured, thesupplementary-fired triple-pressureHRSG sent all of its HP steam to theLM5000 STIG 120 for power augmen-tation. IP saturated steam went to theabsorption chiller and IP superheatedsteam to the single-stage LP turbine(for additional power augmentation),which drove the LP compressor. LPsteam was used for deaeration.

The plants purchase poweragreement (PPA) influences the gasturbine to cycle daily and operateonly during peak hours. Translation:Run 13 (winter) to 15 (summer) hourson weekdays; shut down on week-ends. Sweigart said the plant was ahigh-maintenance facility, difficult torepair, and parts were getting harderto obtain. The company was ready tomake a change.

Capital Powerhad successfullyswapped out the LM5000 at its NorthIsland plant for an LM6000-PD witha dry, low-emissions (DLE) combus-tion system in 2009 and was inclinedto do the same at Oxnard. However,North Island, which supplies electricityto San Diego Gas & Electric Co andthermal energy to the US Navy, wasnot STIG-equipped. Had the company

opted for an LM6000-PD at Oxnard,a steam turbine would have beenrequired as well to meet contractualobligations. Note that North Islandwas GEs first self-perform LM5000 toLM6000 conversion project and Capi-tal Power was satisfied with the job ithad done.

Space limitations and other fac-tors militated against installation ofan LM6000-powered 1 1 com-bined cycle at Oxnard. When theOEM announced availability of theLM6000-PC with STIG (referred to asthe LM6000-PC CDP), Capital Power

believed that was the best alternativefor the site. But dont get the impres-sion this was an easy projectonesimply involving the removal of oneengine and its replacement withanother. There were many constraintsand challenges.

For example, the plant is lockedinto its PPA until 2020, so there waslimited to no opportunity to uprate thefacility and sell additional output. Evenif that were possible, more capacitycouldnt be squeezed from the exist-ing generator. There were budget con-

straints as well. They dictated that theplant reconfigure the existing HRSGto match the new requirements of theLM6000 rather than replace the 20-yr-old boiler.

GE did not do the Oxnard projectturnkey basis. Rather, it provided achange-out kit and engineering sup-port, including a technical advisor(TA). Richards was the project man-ager for Capital Power, which hiredthe contractors required for all but theHRSG work.

Sweigart recalled C D Lyon Con-struction Inc from nearby Ventura asbeing important to the projects suc-cess. Lyon does work for us all thetime, he continued, and they had avested interest in the project. Offer-ing his experience to others, Sweigartsaid its important for the owner tobe proactive to assure jobs like thisare completed in a timely mannerand within budget. Hands-on isengrained in Capital Powers culture,he added.

The proverbial fly in the ointmenton the Oxnard conversion was thegenerator. Sweigart said the LM5000and LM6000 rotate in opposite direc-tions, making it necessary to changethe exciter diode wheel and the threefans on the air-cooled Brush genera-tor. The rotor was pulled and this workwas done at the plant.

Ordinarily, one would expect thatswitching the inlet fan to the outlet

and vice versa would be a relativelyeasy job. Not so at Oxnard. Sweigartsaid the fans had a significant amountof balance weights and after theywere switched and the rotor reinsert-ed in the generator, plant personnelcouldnt eliminate the induced imbal-ance. The rotor had to be removedagain and this time sent out for a spinbalance. Lesson learned: If you do asimilar project, pull the rotor and sendit to a competent shop to swap fanlocations and spin balance.

The project triggered a NewSource Review, requiring environmen-

tal impact studies and modeling toprove the more stringent air qualitystandards would be met with the newengine, addition of CO catalyst, andan upgrade to the SCR. Sweigart saidthe company was committed to doingthe best job it could from an environ-mental perspective. Maintaining closecontact with regulatory authoritieswas important, he added. The permit-ting effort for Oxnard took about sixmonths, primarily with the local airquality district.

The new unit is running well. There

Capital Power installs first STIG-equipped LM6000 a


2/5

COMBINED CYCLEJOURNAL, Third Quarter 2010 65

have been relatively few issues sincestartup, Sweigart saidincludinginstrumentation. He added that Capi-tal Power is not pushing this machinefull throttle as it had the 1990-vintageLM5000. The old engine was 33 MW,augmented to run at 50 MW. TheLM6000 is a low 40s machine withpower augmentation to 50 MW.

Regarding thermal performance,Richards said the heat rate for theLM6000 STIG was predicted to be2% to 3% better than that for theLM5000. At present, she added,theyre getting 2.5%. However, onlyabout a third of the project was

justified on heat-rate improvement;remainder of the expected saving wasexpected to come from eliminatingforced outages and their associatedloss of revenue and cost of leasedengines.

Richards expects the engine willrun 25,000 hours before hot-gas-pathor other parts require replacement.This unit requires less steam injectionthan the LM5000, she said, reducingwater use by 5 million gal/yr. AnnualNOxemissions are decreased by 9tons/yr.

Engine requirements

A conference call with GE engineersdug into the details of the new enginemodel and the operational flexibility itoffers. Participating were Scott Hover,

product services program managerfor the LM6000; Tayo Montgomery,manager of technical sales sup-port for aero GTs; Mike McCarrick,repowering leader for the Americas;Ted Stokley, customer relationshipmanager; and Senior Design EngineerWaseem Adhami.

The editors asked Hover to beginwith a review of options for maximizingoutput and/or performance by injectingwater and/or steam into the LM6000-PC (Fig 1). Starting from the front ofthe machine, fine droplets of water canbe introduced near the compressor

inlet to restore power lost as a result ofhigh ambient temperatures. This evap-orative cooling technique is known asSprint, a term most LM owner/opera-tors are familiar with.

NOxemissions are controlled inengines with single annular combus-tors, like EF Oxnards, by reducingflame temperature via injection ofwater or steam into the combustor(Fig 2).

Finally, STIG, which involvesintroducing HP superheated steamthrough bleed ports (known as CDP

2. Combustor arrangement reveals one steam and one gas manifold. Steamhere is for NOxcontrol

Steam manifoldand feeder hoses

Gas manifoldand feeder hoses

EF Oxnard

1. STIG-equipped LM6000-PC,designated the LM6000-PC CDP, shows someminor modifications from the baseline engine. The HPT first-stage nozzle area,shafts, and coupling adapter called out in the diagram have been modified;other parts are standard PC components

Compressor front frame,collector, variable bleedvalve, and gearbox

Booster and inlet guide vanes

Single annularcombustor

LP turbine

Improved shaftsand couplingadapter for highertorque via hot-enddrive

Turbine rear frame

HP turbinefirst-stage nozzlearea optimized

HP compressor

3. Internal changes to LM6000-PC CDP areshown on engine air-flow diagram for unitequipped with a single annular combustor

Sump pressurizationSump ventHot gas pathCompressor discharge airCompressor air (primary and secondary)Bore cooling air

Air flow controlTurbine cooling air

Frame ventHP recoupLP recoupBalance piston air

NOxsteamOptimizedfirst-stagenozzle area

Steam distribution baffle added;T flange added to compressor rear frame

STIG steam injected intoexisting compressor discharge bleed ports


3/5

66 COMBINED CYCLEJOURNAL, Third Quarter 2010

WESTERN TURBINE USERS

ports) immediately downstream of thecompressor, provides owner/opera-tors a marginal increase in output buta substantial boost in efficiency (Fig3). When Sprint and STIG are usedin combination, very significant gainsin output and efficiency are possible(Table 1).

Hover said the STIG version ofthe LM6000-PC was developed forcustomers (1) upgrading from theLM5000 to LM6000 that had excesssteam available or (2) others that hadlost their steam hosts and wantedto increase the value of their power-

production operations.Its a niche market:Owner/opera-

tors with excess steam are able to sellmore electricity at a lower heat rateusing only their gas turbine/genera-tors. Investment in a steam turbine isnot required. This is why STIG some-times is referred to as the poor mans

combined cycle. But keep in mindthat while capital is conserved, wateris not. Revenue from the additionalkilowatt-hours sold must offset theexpense of water vapor carried outthe stack with exhaust gas.

The design challenge was toadapt the LM6000-PC to absorb upto 50,000 lb/hr of 600F steam forpower augmentation in addition to theapproximately 30,000 lb/hr required toreduce NOxemissions to 25 ppm atthe engine exit. GE engineers had thecompanys experience with STIG onthe LM2500 and LM5000 as a starting

point.Thorough investigations of heat

and mass transfer and componentlifein particular the lives of HP tur-bine airfoilswere required. Theyconfirmed that steam was injected atthe optimum locations and that thepressures and pressure drops along

the gas flow path would assure safe,continuous operation of the engine.

Analyses of other componentsimpacted by the STIG implementa-tion were required as well; in a fewinstances, design changes werenecessary. For example, engineersfound that compressor/turbine shaftsand the coupling adapter had to beupgraded to accommodate the highertorque associated with the hot-endgenerator drive.

In sum, this was a major designeffort which resulted in relativelyminor modifications to the baseengine required to accommodateSTIG. Heres a list of turbine upgradesrequired: Compressor rear frame (CRF)

steam-baffle shop mod to ensureeven distribution of steam injectedinto the engine.

CRF T-flange repair procedure. New HP turbine first-stage nozzle

segments. On-engine steam delivery piping. HP turbine nozzle jumper tubes

and check valves.Plus, a new turbine control system

was installed.Package and other onsite work

included steam piping and valve modsto route steam from the HRSG to thegas turbine; HRSG work as describedin the next section; steam pipingand associated purge and drain linesrequired to deliver steam to the com-pressor discharge bleed ports.

Wrapping up the discussion, theGE engineers said that conversion

from an LM5000 to STIG-equippedLM6000 improves power output andefficiency and increases reliability andavailability with virtually no impact onstart times. They suggested that con-version decisions be made only afterconducting studies to evaluate gener-ator and transformer capacity, exam-

2. How the upgraded HRSG compares to the original

Orig HRSG Orig HRSG UpgradedSuperheated steam data with LM5000 with LM6000 HRSG

HP flow, 1000 lb/hr 71.7 64.5 71.7

HP temp, F 585 597 625

HP press, psia 582 580 650

IP flow, 1000 lb/hr 21.6 19.5 0

IP temp, F 502 494 NA

IP press, psia 200 195 NA

LP/deaerator press, psia 41 32 52

1. Comparing options for the LM6000-PC CDP

Parameter Base PC Sprint only Sprint + STIG STIG only*

Output, MW 46.1 51.5 55.1 46.9

Efficiency, % 43.1 42.8 45.2 45.5

NOxsteam, 1000 lb/hr 31 31 33 30

Steam for export, 1000 lb/hr 71 81 28 14

STIG steam, 1000 lb/hr NA NA 50 50

HRSG total output, 1000 lb/hr 102 112 111 94*Sprint off

4. Heat-recovery steam generator, which supplies STIG and NOxsteam to the gas turbine required a redesign effort,some new components, and modification of others to accommodate the change in engines from LM5000 STIG 120 toLM6000-PC CDP

Removed line/decommissioned heating surfaceNew line/new heating surfaceModified heating surface/line

SCRcatalyst

COcatalyst AIG

HPSH1

HPEV1

HPEV2

HPEV3

HPEV4

HPEV5

HPEV6

IPSHt

oHPECA

IPEV

1

IPEV

2

IPEV

3

IPEV

4

IPEV

5

IPEV

6

IPEV

7

IPEV

8

IPEV

9

IPEV

A

HPEC1

HPEC2

IPEC1

HPEC3

HPEC4

IPEC3

HPEC5

LPEV

1

LPEV

2

LPEV

3

LPEV

4

LPEV

5

IPEC2

HPdrum

IPdrum

LPdrum/deaerator

HPHigh pressureIPIntermediate pressureLPLow pressure

ECEconomizerEVEvaporatorSHSuperheater


4/5


ining HRSG capability, and reviewingexisting air permits and PPAs.

HRSG modifications

Perhaps the most challenging part ofconverting EF Oxnard to the STIG-equipped LM6000-PC was the designand field work required to upgrade theHRSG for the new service. As a result

of the New Source Review, CO cata-lyst was added to the boiler and theSCR upgraded to limit NOxemissionsto 2 ppmdown from 4.1 ppm.

The engineering study phase ofthe HRSG project began by model-ing the boiler in its current conditionusing using Vogts proprietary designsoftware. This effort explored threelevels of performance with varying LPand deaerator pressures, the corre-sponding IP and HP economizer inletwater temperatures, and differenttargets for HP and IP superheatedsteam. Options were presented for

modifying the existing unit to meeteach of the three design points.

Table 2 shows the data compiledduring the modeling study. The firstcolumn is self explanatory; informa-tion presented is for the originalHRSG/LM5000 configuration. Itagreed with actual plant data, validat-ing the models accuracy.

The second column presentswhat could be expected by using theoriginal HRSG with the LM6000. Thisinformation revealed bothASME Boil-er and Pressure Vessel Code viola-

tions and unacceptable performancedata. For example, superheated IPsteam used as a power boost for theLM5000s LP turbine has no purposein the reconfigured plant.

However, the 36,000 lb/hr of IPsaturated steam for the absorptionrefrigeration unit had to be maintainedas part of the retrofit. Modeling madeit clear that new tube bundles (harps)

would be required for the superheatersection and the first HP evaporatorsection (Fig 4).

The third column shows perfor-mance predicted with the new harpsand other necessary modifications(Fig 5). HP steam flow, temperature,and pressure met the LM6000-PCCDP requirements and the saturatedIP steam flow the absorption reefersneeds.

Peter Allison, a member of Vogtsaftermarket business developmentteam with experience in thermal mod-eling, said that the decommissioned

lines and heat-transfer surfaces shownin red in Fig 4 were disconnected andisolated with appropriate pipe capsand drains in case the plants steamrequirements change in the future. Thepressure-drop penalty for leaving thesuperfluous heat-transfer surface inplace is about 1.5 in. H2O.

Vogt provided Capital Power withtwo different formulations of SCRcatalyst, each with two options forvarying gas-side pressure drop andguaranteed life, and one formulationof CO catalyst with options for varying

pressure drop and life. Performanceof the catalyst formulations selectedis detailed in Tables 3 and 4.

Vogts scope of work included thefollowing: Turnkey constructionincluding

demolition and installation, con-struction management, onsite TAservices, and commissioning of theupgraded HRSG and related auxil-

iaries. SCR catalyst replacement and new

CO catalystincluding design,structural modification and rein-forcement, removal/installation,access doors, casing mods, instru-mentation ports, etc.

Replacement of the HP superheat-er and first HP evaporator harpsfabricated by Chanute Manufactur-ing, Tulsa.

Conversion of the original IPsuperheater into an additional HPeconomizer harp, including testing.

Decommissioning of half the IP

economizer surface and two of thethree IP economizer harps.

Piping modifications. Boiler cleaning and hydro. Allison

stressed that cleanliness wasimportant on both on the water andgas sides of the HRSG. Ductworkand external tube surfaces werethoroughly cleaned before startupwith catalyst in place becauseschedule constraints did not allowfor first fire without catalyst installedto burn off oil and other foreignsubstances from the gas side.

3. Impact of installing CO catalyst*

Pressure drop, in. H2O 1.8CO at turbine exit, ppmvd at 15% O2 75

CO at stack exit, ppmvd at 15% O2 46.3VOC at turbine exit, ppmvd at 15% O2 4.7VOC at stack exit, ppmvd at 15% O2 2*CO catalyst was added as part of the LM6000 upgrade

4. NOxemissions halved with new SCR

AfterParameter Original upgrade

Pressure drop, in. H2O 2.2 1.4NOxat turbine exit, ppmvd at 15% O2 25 25

NOxat stack exit, ppmvd at 15% O2 4.1 2

Ammonia slip, ppmvd at 15% O2 10 5

5. New HP evapo-rator module,located immediatelydownstream of theammonia injectiongrid (refer to Fig4), is lowered intoplace. The singleHP superheater

module also wasreplaced (left)

6. Fresh chargeof SCR catalystoffered improvedNOxdestructionefficiency and lowerpressure drop (right)


5/5


Solar Thermal IntegrationVogt Power International Inc. a world class HRSG designer and

manufacturer offers Aftermarket products and services for all OEMs

HRSGs, including: Inspections & Field Services, Studies & Modeling,

Turnkey Retrofits, Replacement & Spare Parts and LCAMPSoftware.

VOGTPOWERINTERNATIONALINC UPONTCIRCLE, LOUISVILLE TELEPHONE AX WWW.VOGTPOWER.COM

Field Service and Aftermarketsolutions for ALLHRSGs

VOGT POWER INTERNATIONAL INC.

Documents

Vogt Hsrg Stig-equipped Lm6000 Vpi-mg-0007