10 GAS TURBINE WORLD: May – June 2013

Hitachi’s new H-80 dual shaft en-gine puts the company in direct

competition with the advanced ‘F-technology’ class large gas turbines being marketed by world OEMs for 50/60Hz power plants. Notably:

o Simple cycle. Design rated at 110.6MW and 37.6% efficien-cy for 60Hz power generation and 112.4MW and 38.2% efficiency for 50Hz power.

o Combined cycle. Net rated at 154.4 to 155.8MW base load output (60/50Hz) and 53.1 to 53.4 % effi-ciency for 1x1 unfired configurations.

o Cogeneration. Exhaust ducted into unfired HRSG at 545°C provides 165 tons/hour of 870 psig, 300°C pro-cess steam at over 80% CHP effi-ciency.

Initially, the driver behind the H-80 development program was to design a gas turbine that could be retrofit-ted to upgrade early combined cycles installed in the 1990s still in service operating at relatively low plant effi-ciencies and high CO2 emissions. The goal was to achieve a flange-to-flange engine exchange without having to modify any of the asso-ciated plant equipment such as the HRSG, steam turbine, electric genera-tor and auxiliary drives. To achieve this, say Hitachi proj-ect managers, it was necessary to keep exhaust flows and temperatures

of the H-80 largely the same as the machine(s) to be replaced. And not exceed the original gas turbine foot-print or interconnections. From an engineering design point of view, the major goals were to:● increase compressor ratio and firing temperature (to improve efficiency) while keeping the exhaust tempera-ture approximately the same,● adjust compressor speed to achieve approximately the same flow as the old units to be replaced, and ● adopt a two-shaft design that would eliminate the need for a reduction

gear and thereby minimize space re-quirements for installing the H-80 gas turbines.

New combined cycles More recently, Hitachi has also devel-oped a series of standardized 1x1 and 2x1 combined cycle reference plant designs for 60Hz and 50Hz green-field power projects using simplified equipment and easily replicated com-ponent modules in order to minimize plant costs. For 60Hz operation, the 1x1 H-80 combined cycle block is rated

H-80 dual shaft gas turbine ratedover 110MW and 37% efficiency By Victor deBiasi

Hitachi’s 1300°C-class gas turbine is being marketed for ‘drop-in’ repowering of existing combined cycle plants and for new 50/60Hz power generation projects.

H-80 gas turbine rotor. HP turbine runs at 4,580 rpm speed of compressor: LP tur-bine at 3,000 / 3,600 rpm for direct 50/60Hz generator drive without a reduction gear.

GAS TURBINE WORLD: May – June 2013 11

at 154.5MW and 53.1% efficiency (including gas turbine losses) and the 2x1 configuration is rated at 321.2MW and 55.2% efficiency. For 50Hz generation, the 1x1 H-80 combined cycle block is rated at 155.8MW and 53.4% efficiency (including gas turbine losses) and the 2x1 configuration is rated at 322.8MW plant output and 55.3% ef-ficiency. For both versions, the 1x1 and the 2x1 plant configurations are multi-shaft designs in which the gas turbine(s) and steam turbine each drive their own individual generators. Standard 2x1 combined cycle de-sign arrangements for both 50 and 60Hz power generation include a tri-ple pressure reheat cycle for the steam side and unfired HRSG operation. For standard 1x1 combined cycles, the steam system is designed around an unfired, dual pressure level HRSG and dual pressure, non-reheat steam turbine. Steam condenser pressure on all variations is 1.2 inches Hg.

New cogeneration plantsThanks to its 1015°F exhaust temper-ature and near 680 lb/sec mass flow, the H-80 also is a decent candidate for combined heat and power projects. At base load output, ducting the gas turbine’s exhaust into an unfired HRSG can provide 165 metric tons/hour of process steam at 6MPa and 300°C steam flow conditions (870 psig and 570°F) at better than 80% CHP efficiency. With supplementary firing of gas turbine exhaust, the HRSG can be duct fired to 700°C inlet temperature and significantly increased steam pro-duction of more than 270 t/h at 6MPa and 300°C steam conditions. Standard CHP plant configurations have been designed around unfired two-pressure level horizontal gas flow HRSG boilers that can be installed alongside the gas turbine generator package. Provisions for selective catalytic reduction units in the HRSG are avail-

able for ultra low NOx attainment ar-eas. Auxiliary systems for such plants provide complete ammonia storage, injection and dilution fan equipment.

H-80 gas turbine The H-80 is in the 1300°C (2370°F) turbine nozzle inlet temperature range, putting it at a somewhat high-er firing temperature than that of the 1260°C (2300°F) model H-25. Unlike the single-shaft H-25 from which it is scaled, the H-80 is a dual

shaft machine with separate compres-sor rotor and an aerodynamically cou-pled free power turbine. The power turbine operates at 3600 rpm to directly drive a 60Hz generator or at 3000 rpm for 50Hz, without a reduction gearbox. While the smaller single-shaft H-15/25 units drive out of the com-pressor (cold end), the large twin shaft machine is hot end drive with the load coupling at the exhaust end of the tur-bine.

H-80 factory unit. A total of twelve H-80 gas turbines have been ordered or installed by electric utilities (as of May 2013) to upgrade old combined cycle plants by replac-ing their gas turbines with “drop in” units to increase combined cycle output and re-duce site emissions. This is a photo of the new H-80 two-shaft engine during factory build.

Shin Oita Original H-80 plant Actual H-80 combined cycle plant design rating design rating performance

Net plant output (at 15°C) 111.4 MW 126.5 MW 128.2 MW

Relative power increase base ref 13.5% 15.0%

Net CC efficiency (LHV) 47.7% 51.3% 51.4%

Relative difference base ref 7.7% 7.9%

Source: Hitachi May 2013, Shin Oita power station plant

Repowered plant ratings. First H-80 “flange to flange” replacement for Ky-ushu Electric 3.5 years ago has logged over 24,000 hours of service (as of May 2013) at a 15% higher power and 8% better efficiency rating.

12 GAS TURBINE WORLD: May – June 2013

Design featuresThe H-80 is a heavy frame gas tur-bine with cast iron and steel casings, horizontally split throughout to allow top casing lift for complete rotor ac-cess. Combined with a reverse-flow can-type externally accessible combustor, Hitachi engineers say the design pro-vides a high degree of maintainability and enables onsite replacement of all hot gas path parts. It has a 17-stage axial-flow com-pressor with a pressure ratio of 19.3 to 1 and is capable of variable-speed

operation and running at reduced load. It rotates at 4580 rpm at full rated output. Part of the challenge of compres-sor development, say Hitachi design engineers, is to ensure that the com-pressor operates reliably over the wide range of flow rates from start-up to shut-down, and to prevent any instability such as rotating stall and surging. There are variable inlet guide vanes (IGVs) at the compressor entry, followed by two stages of variable geometry vanes to control partial load

airflow and surge. This provides good engine control for cycling and partial load opera-tion, and also keeps the exhaust tem-perature high at lower loads for good combined cycle and cogeneration per-formance.

Compressor and combustors The 17-stage compressor used for the H-80 is a scaled up design (derived from the mature H-25 compressor) capable of variable speed operation at low load. It was developed with the help of transonic stage design techniques and multi-stage flow analysis. Compressor rotor and stator blades are made of 12Cr-Nb steel and 12Cr steel, and receive a corrosion-resistant coating. Ten individual combustor cans are arranged at a shallow angle around the turbine centerline. These feature slot cooled liners and are intercon-nected with cross fire tubes. Three combustor options include unabated, dry low NOx, steam/water injection for NOx control. The stan-dard DLN combustion system limits

H-80 two-shaft engine. Industrial frame design has separate 17-stage compressor rotor (with three variable vane stages) with an air cooled two-stage turbine driving a closely coupled two-stage free power turbine. Power turbine settings of 3000 or 3600 rpm directly drive 50- and 60Hz generators without the need for a reduction gearbox. Ten dry low NOx (DLN) reverse flow can-annular combustors with multi-fuel capability limit emissions on natural gas fuel to less than 15ppm NOx.

H-80 power plant 60Hz Design 50Hz Design

Base load output 110,610 kW 112,440 kW

Heat rate (LHV) 9080 Btu/kWh 8925 Btu/kWh

Plant efficiency 37.6% 38.2%

Turbine speed 3600 rpm 3000 rpm

Pressure ratio 19.3 to 1 19.3 to 1

Exhaust flow 677.2 lb/sec 679.5 lb/sec

Exhaust temperature 1015°F 1015°F

Source: Hitachi, May 2013

H-80 simple cycle ratings. ISO design performance at 15°C (59°F) sea level site conditions without inlet and outlet losses on natural gas fuel.

14 GAS TURBINE WORLD: May – June 2013

emissions to less than 15ppm NOx at 15% O2 on natural gas fuel. DLN designs are based on the proven H-25 dry combustion system design. The pre-mixed, low NOx combustor has a diffusion pilot and is based on a ring-shaped flame holder.

Cooled HP turbineThe high-pressure turbine driving the compressor is a two-stage air-cooled unit with cooling applied on all stages of rotating and stationary airfoils. The cobalt-based first stage tur-bine nozzle design incorporates im-pingement cooling and film cooling, with pin fin cooling on the trailing edges. First stage blades (buckets) made of nickel-base alloys for high temper-ature strength incorporate return flow cooling technology first developed by Hitachi in the 1980s. The design includes a turbulence promoter on the surface in the cool-ing flow path to improve performance without using a large volume of cool-ing air. The first-stage turbine nozzle and bucket airfoils are given a ceramic thermal barrier coating (TBC) that helps cool and protect the metal sur-faces. This lowers the base material temperature by about 50°C, says Hi-tachi, compared to that without TBC. The two-stage free power turbine (low pressure turbine) is close cou-pled to the gas generator and operates at 3600 or 3000 rpm full load. This is an axial flow unit with shrouded rotating blades to provide higher efficiency with lower tip loss-es. Interestingly, the first stage nozzle of the power turbine is air-cooled.

MaintenanceOnsite maintenance support is de-signed into the machine with sys-tems such as individually replaceable blades and vanes, external combustor basket access and field lift of casings for rotor access. Inspection intervals will vary de-pending on site installation and op-

erating conditions, but Hitachi plant engineers have developed a standard natural gas fueled inspection shut-down schedule for the H-80, based on a full 8000 hours per year continuous operation case. Combustion inspections are rou-tinely scheduled at 12,000-hr inter-vals (8 days downtime); hot gas path inspection at 24,000 hours (20 days); and major inspections every 48,000 hours (30 days). Hitachi supports its machines with a global spare parts supply network and service support centers.

Commercial installationsThe first prototype H-80 began facto-ry test in January 2009 for long-term performance and design verification. Fully instrumented tests were con-ducted up until June of that year to validate the overall design and to ver-ify performance characteristics. Tests included full load, part load, start-stop, cycling and load rejection. This H-80 was then supplied for follow-on field installation testing as a replacement turbine for an earlier generation Frame 7 machine at unit 1 of the Shin Oita power station in Aosaki, Japan owned and operated by Kyushu Electric Power Co.

It began test operation in electric utility service in October 2009 as part of a single-shaft combined cycle pow-er block at Shin Oita. Having confirmed the perfor-mance, reliability, operation and con-trol functionality through factory and onsite testing, the unit began com-mercial operation for Kyushu on Jan-uary 8, 2010 as turbine 4 at Unit 1. Since then, three other machines have been installed and have entered commercial operation at Shin Ohita. Two more are in build for delivery starting later this year.

Replacement marketLike the 30MW-class H-25, the new H-80 was conceived as a ‘drop in’ replacement for existing older gas tur-bine models such as the hot end drive Frame 7EA. The smaller H-25 was aimed at the MS5001 genset replacement mar-ket, providing a higher efficiency and higher power retrofit which promised very quick payback with substantial fuel savings. And indeed, a number of H-25 units have been installed as replace-ment sets. But a greater number are at new green field plant sites. Since their design introduction in

1x1 Combined Cycle 60Hz Plant 50Hz Plant

Net plant output 154,450 kW 155,790 kW

Net heat rate 6426 Btu/kWh 6390 Btu/kWh

Efficiency 53.1% 53.4%

Gas turbine power 107,360 kW 108,940 kW

Steam turbine power 47,090 kW 46,850 kW

2x1 Combined Cycle 60Hz Plant 50Hz Plant

Net plant output 321,150 kW 322,830 kW

Net heat rate 6181 Btu/kWh 6170 Btu/kWh

Efficiency 55.2% 55.3%

Gas turbine power 214,720 kW 217,880 kW

Steam turbine power 106,430 kW 104,950 kW

Source: Hitachi May 2013

H-80 combined cycle ratings. Net plant performance for 1.2 inch Hg condenser pressure design and 59°F sea level site conditions.

16 GAS TURBINE WORLD: May – June 2013

1988, Hitachi reports, over 150 H-25 machines sold and installed world-wide are approaching 1.5 million fired hours of operation to date.

Repowering projectsThe prototype production H-80 for Kyushu Electric replaced an

MS7001E base load combined cycle gas turbine operating on LNG fuel. Shin Oita Unit 1 is a 750MW com-bined cycle plant composed of six individual single-shaft modules, each with a gas turbine, HRSG and steam turbine driving a single central gen-erator.

The original 7E combined cycle modules were installed sequentially starting in 1990 and began operation in 1991. Following the initial H-80 retrofit, Unit 1 has since been ful-ly converted, with all six combined cycle modules now retrofitted with H-80 gas turbines. A nearly identical project involv-ing 7E replacement was carried out at Chugoku Electric Power Company’s Yanai power station in southern Ja-pan. This retrofit project sited near Ya-maguchi involves replacing the older six 7E gas turbines with new H-80s. Like the Kyushu Electric project, this was an LNG fueled combined cycle built of single-shaft power trains. Similarly, this H-80 retrofit in-stallation is designed to preserve as much of the existing plant structure and equipment as possible in addition to the generator, heat recovery boiler and steam turbine. As of the end first quarter in 2013, Chugoku had two units installed and in commercial operation, while the remaining four H-80s are under man-ufacture for delivery starting later this year. Together, both these domestic Jap-anese projects account for the twelve H-80s that have been sold, being built or installed to date. Six machines are in commercial operation, with cumu-lative operating hours over 90,000 as of the end of the first quarter.Greenfield projectsAlthough the H-80 was initially con-ceived as a ‘drop in’ flange-to-flange replacement for existing, older gas turbine models, Hitachi also sees a growth market for greenfield projects. The US market is of particular in-terest considering the large number of coal plant retirements with capacities of less than 200 MW that have been announced,. “These are prime candidates,” say company marketing executives, “that may need to be replaced by gas-fired simple or combined cycle plants.” n

H-80 Unfired HRSG Steam Profile. Typical steam production curves for 545°C (1015°F) gas turbine exhaust without supplementary firing.

H-80 Fired HRSG Steam Profile. Typical steam production curves with supple-mentary duct firing to 700°C (1290°F) inlet temperature.

– 190

– 180

– 170

– 160

– 150

– 140

– 130

– 280

– 270

– 260

– 250

– 240

– 230

– 220

– 210

Steam flow (t/h)

Steam flow (t/h)

Steam Pressure (MPa)

Steam Pressure (MPa)

saturated

saturated

0 1 3 52 4 6

0 1 3 52 4 6

200°C

200°C

250°C

250°C

300°C

300°C

350°C

350°C

400°C

400°C

450°C

450°C

500°C

500°C