Himeji Number 2 Goes Commercial

7/24/2019 Himeji Number 2 Goes Commercial

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Himeji No.2 goes commercial

The new M501J gas turbine combined cycle units at Himeji No.2 havesuccessfully started commercial operation and are demonstrating world-

class levels of efficiency.

Aerial view of Himeji No.2. The power station is the largest thermal power plant owned by Kansai

Electric.

Five years ago the Kansai Electric Power Company (Kansai Electric) started a large-

scale project to replace Himeji No.2 Thermal Power Station with what it claimed would

be the worlds most efficient combined cycle plant featuring Mitsubishi Hitachi Power

Systems (MHPS) 501J gas turbines.

The last unit of this environment friendly project, which targeted reduction of greenhouse

gas emissions while securing a competitive power supply for the Kansai area, began

commercial operation earlier this year.


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The new combined cycle plant:

Has recorded an electrical efficiency over 60 %

Enables about 30% CO2 and 85% NOx reduction compared with the original plant

Will deliver savings in the order of $520 million per year compared with the old plant.

With the high price of gas in Japan typically being four to five times that in the US

high efficiency has long been a pursuit of Japanese companies. Accordingly, when

Kansai Electric, took the decision to replace the Himeji No.2 Thermal Power Station, it

opted for state-of-the-art technology.

Although Kansai Electric could not foresee future events, the decision to opt for the most

efficient technology proved to be visionary. Since the disaster at Fukushima, which

forced the closure of the countrys entire nuclear fleet, Japan has had to rely on thermal

generation and expensive imported fuel. This had made Himeji 2 an even more

important asset in Kansai Electrics generating portfolio.

MHPS installed the first 501J at its T-Point station, which is its validation plant. MHPS

owns T-Point and sells the power output to Kansai Electric. Prior to Japans nuclear

shutdown, this plant used to predominantly operate in cycling mode, meeting peak

demand for Kansai. Since Fukushima, however, it has been running more continuously

to help ease the tight supply in the region.

Plant configuration

Himeji No.2 power station is the largest thermal power plant owned by Kansai Electric.

The original plant, built in 1963, was composed of six conventional units with a total

output of 2550 MW. These units were originally commissioned and operated with crude


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or heavy oil but were later converted to natural gas. Two of the original units are still in

operation.

The new Himeji No.2 Thermal Power Station is a state-of-the-art combined cycle plant

comprised of six single-shaft blocks rated 486.5 MW each (at an ambient of 4C) for a

total capacity of 2919 MW. Each block consists of one M501J gas turbine rigidly

coupled to a SRT-50 single reheat steam turbine.

Because the gas and steam turbine are linked in a single shaft arrangement without a

clutch, the gas turbine and steam turbine are ramped up at the same time.

All six combined cycle blocks have started commercial operation with high reliability

and, according to MHPS, are demonstrating superior performance with a net efficiency

in excess of 60%.

High efficiency GT

The main contributor to this high efficiency is the M501J gas turbine and its high turbine

inlet temperature.

The M501J gas turbine has been designed with a turbine inlet temperature of 1600C

(2912F) by integrating the proven component technologies used in the 1400C F-series

and the 1500C G series turbines. The M501J also benefited from the development of

key technologies for the national 1700C-class gas turbine project.

The turbine has been carefully developed over a number of years. Operating tests of the

first M501J gas turbine started in February 2011 at Machinery Works T-Point

demonstration combined-cycle power plant in Takasago. The tests proceeded as

scheduled with the first spin-up on February 2nd followed by first ignition soon after. The


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inlet temperature reached 1600C on the seventh start-up. The unit went commercial on

July 1, 2011.

The design of the M501J gas turbine is based on proven F- and G-series features:

The compressor shaft-end drive connected to the generator reduces the thermal

expansion and eliminates the need for a flexible coupling.

The rotor has a two-bearing structure to support the compressor and turbine ends.

An axial flow exhaust structure is used to optimize the combined-cycle plant layout.

The rotor structure has bolt-connected disks with the torque pin in the compressor

rotor and a disc with curved coupling in the turbine rotor to ensure reliable torque

transmission.

The M501J turbine section is an axial-flow, four-stage, high-load, high-performance

turbine.

Row-1 to row-4 rotating blades and rows 1-3 stationary vanes are air-cooled. Unlike the

row-4 blades in the G-series turbine, which are uncooled, those in the J-series turbine

are cooled to cope with the higher inlet temperature. As with the F- and G-series gas

turbines MGA1400 (Mitsubishi Gas Turbine Alloy) is used for the rotating blades, while

the vanes are made of MGA2400. The rows 1-3 blades are made of DS (directionalsolidified) superalloy.


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Exterior view of the new plant. The power station is a state-of-the-art combined cycle plant

composed of six single-shaft blocks each rated at 486. !".

The cooling structure was improved for the F-series and again for the G-series turbine,

and the J-series uses high-performance film cooling and advanced thermal barrier


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coating (TBC) developed in the national project, aimed at developing a 1700C

machine.

The M501J compressor is designed as an axial flow type with a pressure ratio of 23:1; it

was based on the technology used in the H-series compressor, which has a pressure

ratio of 25:1. Three-dimensional (3D) advanced design techniques were used to

improve the performance and reduce the shockwave loss in the initial stages and

frictional loss in the intermediate and final stages.

In addition, bleeding was used in the low-, middle-, and high-pressure stages during

compressor start-up to suppress rotating stall on start-up, and the partial-load

performance of the combined cycle was improved, by controlling the inlet guide vane

(IGV) and three-stage variable stator vanes.

M501J cross-sectional view. The t#rbine section is an axial-flow$ fo#r-stage$ high-load$ high-

performance t#rbine. The compressor is designed as an axial flow type with a press#re ratio of %&'(.

The M501J combustor is based on the proven steam cooling system used in G-series

gas turbines. MHPS implemented steam cooling mainly to enable operation at high

temperatures with reasonable NOx emissions.


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While other manufacturers have largely abandoned steam cooling, MHPSs has

extensive, positive experience with the technology. The company has millions of

operating hours on the largest steam cooled fleet in the market with very good reliability.

Third parties have validated MHPSs availability and reliability figures. Operational data

from the M501G, which also uses steam cooling, has been collected by Strategic Power

Systems Inc (SPS) since 2009 and reported through the Operational Reliability Analysis

Program (ORAP) for verification. According to the data, the M501G fleet has

demonstrated a five-year reliability average of 98.8 per cent.

MHPSs steam cooling technology is different to other OEMs, where the GT is started up

using air cooling and transferred to steam cooling under part-load conditions. In order to

prevent the associated thermal shock, MHPS steam cooling is applied prior to firing the

engine and the completion of a warm-up sequence is a requirement for start-up.

M501J sinle-shaft confi!ration. Each block consists of one !)(* gas t#rbine rigidly co#pled to

a +,T-) single reheat steam t#rbine. eca#se the gas and steam t#rbine are in a single shaft

arrangement witho#t a cl#tch$ the gas t#rbine and steam t#rbine are ramped #p at the same time.

This warm-up sequence is common with steam turbines to prevent condensate water

ingestion. The warm-up sequence starts automatically and the plant can be started

once all the condensate is removed from the line and the steam is

superheated.


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Although this means it takes longer to start the gas turbine, there is less thermal shock,

which improves reliability. While some argue the requirement for an auxiliary boiler

MHPS does not see this as an issue, as an auxiliary boiler is usually needed in thesteam turbine seals of modern plants to start quickly.

Compared with conventional air-cooling, this start-up sequence will add perhaps five

minutes to start-up (time to gas turbine ignition) from a hot-start condition and around 30

minutes from a warm start. If the machine is cold, it would add about 40 minutes.

Although the turbine inlet temperature is increased from 1500C in the G-series to

1600C in the J-series, the subsequent rise in nitrogen oxide (NOx) emissions are

limited through the use of low-NOx technologies by improving the combustion nozzle for

more homogeneous mixing of fuel and air and reducing the local flame temperature in

the combustion area.

Bottoming cycle

While the efficiency of the gas turbine is important, it is also essential to optimize thebottoming cycle to achieve the high combined cycle efficiency that has been recorded at

Himeji No.2.

If the vacuum in the condenser is not efficient or the exhaust ducts from the gas turbine

to the HRSG are not optimized etc., the end result is a relatively low combined cycle

efficiency.

Notably, the steam turbine is a big contributor to the overall combined cycle efficiency.

The state-of-the-art SRT 50 steam turbine was designed to operate with a condenser

vacuum of 96.3 kPa and features 50-inch last stage steel blades that result in large

annular area for high efficiency and large capacity.


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This new large-capacity, single-casing reheat turbine features other advanced

technologies such as high-efficiency reaction blade, welded rotor, advanced seals and

high performance bearings developed to achieve higher efficiency, and more compactdesign.

"inle-casin steam t!r#ine.The steam t#rbine is a big contrib#tor to the oerall combined cycle

efficiency. The )-inch last stage steel blades res#lt in large ann#lar area for high efficiency and

large capacity

Construction

The optimized bottoming cycle and high efficiency gas turbine has led to a plant that has

the highest efficiency in Kansai Electrics fleet. Since startup, the units have recorded

over 60% efficiency at ambient conditions, thus easing the tight energy situation.


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In order to help mitigate the current energy shortage, the construction and

commissioning schedule of the new Himeji No.2 plant was carefully modified to expedite

the Commercial Operation Date (COD) of each unit from its original schedule.

The Table (see page 17) shows the contractual and actual COD dates of the first four

and the subsequent two.

First gas turbine shipment to Himeji No.2. The accumulated operating hours of Unit No.1 is over

16 000 hours as of June 2015.

The original plan contemplated the decommissioning of the existing Units 5 and 6 prior

to the installation of the new Units 4 to 6. However, due to the critical electricity supply

caused by the earthquake, the removal of the existing Units 5 and 6 was postponed.

The new units were constructed in the area made available by the removal of Units 1

through 3. This simultaneous removal and construction combined with the large-scale of


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the project in a fairly congested industrial area involved very complex planning and

execution.

Existing facilities, notably the water intake/discharge infrastructure, were used by both

the existing and the newly erected units.

Close communication and cooperation of several teams involving mechanical, electrical,

I&C, and other departments prevented unintended interference connecting piping and

many other major activities in the existing and new units. Careful attention was paid to

avoid impacting on the operation of the existing units.

The Himeji No.2 Power Station was conceived prior to the earthquake and tsunami that

hit Japan in March 2011. In an effort to alleviate the difficult power supply situation in the

Kansai area, Kansai Electric and its suppliers initiated an aggressive acceleration

program that accelerated the COD of the first four units by two to four months and eight

months for the last two remaining blocks. This was especially important to meet the high

demand for electricity during the summer/winter peaks.

The newly installed units have operated continuously at base load (approximately 486.5

MW at site condition) with very good reliability since startup. The accumulated operating

hours of Unit No.1 is over 16 000 hours as of June 2015.


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Internal view of the turbine hall.The newly installed combined cycle units have operated

continuously at base load (approximately 486.5 MW at site conditions).

Environment and economics

The plants high efficiency has enabled about 30% CO2 and 85% NOx reduction

compared with the original plant. In addition, the amount of warm water discharged is

about 40% lower, thus reducing the ecological impact of the plant on the bay ecosystem.

The vastly improved cycle efficiency results in substantial fuel cost savings. The new

high efficiency combined cycle plant translates into savings in the order of $520 million

per year compared with the old plant (42% efficiency).


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Even when compared with current technology, the savings are significant. Compared to

combined cycle plants based on F-Class (54% efficiency) and assuming the same

power output, the estimated saving is $253 million per year.

Looking forward

MHPS has sold 38 M501J turbines with 17 already in operation.

In addition to those in Japan, it is operating units in Korea. The company has sold six in

North America, with the first unit in Oklahoma scheduled to begin commercial operation

in 2017.

MHPS is confident of the M501Js performance and its place in the market based on the

ability of T-Point plant to detect and correct typical prototype issues before a new

machine goes to a client. The ability to do this is a big contributor to the high reliability of

the fleet.

Documents

Himeji Number 2 Goes Commercial