Himeji No.2 goes commercial

The new M501J gas turbine combined cycle units at Himeji No.2 have successfully 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 world’s 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.

 

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 country’s 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 Electric’s 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 Japan’s 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 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 4°C) 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 1600°C (2912°F) by integrating the proven component technologies used in the 1400°C F-series and the 1500°C G series turbines. The M501J also benefited from the development of key technologies for the national 1700°C-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 inlet temperature reached 1600°C 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 (directional solidified) superalloy.

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 486.5 MW.

 

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