Tests confirm 40 MW output for Hitachi's humid air turbine

Hitachi recently announced the achievement of rated output at the 40MW-class test facility with the new gas turbine, AHAT (Advanced Humid Air Turbine) system, being co-developed with the Central Research Institute of Electric Power Industry (CRIEPI) and Sumitomo Precision Products Co., Ltd. (SPP).

Through operations at this facility, it has been verified for the first time that the key components of the AHAT system can be applied to medium-class gas turbines. Further tests to confirm operating characteristics under various conditions and component reliability will be conducted while developing scale-up technology for application in a demonstration plant, to realize small-medium class (~ 200MW-class) highly efficient gas turbine generation systems.

With a growing demand in recent years for highly efficient gas turbines to achieve economic efficiency and low environmental impact and increase efficiency to improve stable operations, environmental consideration, and optimization of operating costs, Gas Turbine Combined Cycle (GTCC) generation is used widely as a highly efficient technology in gas thermal power generation.

However, further development to increase efficiency and reduce costs is being anticipated. Also, as the mass introduction of renewable energy systems such as wind and solar is also taking place, a power adjustment system excelling in a fast start-up speed and load following capability, is becoming increasingly important.

To respond to these needs, Hitachi, CRIEPI and SPP have proceeded with the development of key technology for AHAT cycle power generation and its system verification since 2004, in a project supported by the Ministry of Economy, Trade and Industry, Japan.

Feasibility tests of the AHAT principle were completed in 2010 with a 3MW-class small gas turbine. However, as the system components such as the centrifugal compressor and a can-type combustor were configured for a small-class turbine, feasibility tests in a medium-class gas turbine with multi-stage axial-flow compressors and multi can-type combustors were required.

Further, to contribute to lower environmental load, the reduction of NOx emissions was also an issue. Hitachi therefore developed a 40MW-class test facility to apply the AHAT technology developed to a medium-class gas turbine used in industry and combustor technology to achieve a reduction in NOx emission, and verified operation.

The technology developed in the 40MW-class test facility has the following features:

System configured for a medium-class gas turbine used in power utilities: A droplet evaporation model was developed and incorporated in a fluid simulation, to optimize the compressor blade angles. To improve the cooling performance of the turbine component, a hybrid cooling nozzle was developed using the highly humid air and the discharged air from the compressor, enabling the nozzle to be cooled to below target temperature. As a result, the start-up time from ignition to rated power could be achieved in 60 minutes, about one-third that of a GTCC cold start.

Contributing to a reduction in environmental load: In this 40MW-class test facility, stable combustion with reduced NOx emission under higher temperature and pressure conditions (Gas temperature 1,270℃, Pressure 1.7MPa) than the previous 3MW- class test facility (1,180℃, 0.8MPa) was required. To reduce NOx further, a fuel nozzle with lateral pores was developed to enhance mixing of fuel and air, optimizing it for a cluster nozzle burner which is a high humidity combustor. As a result, a NOx concentration of 24ppm (at 16 percent O2) was confirmed for the humidity of the pilot equipment (approx. 10 weight percent), and a NOx concentration of less than 10ppm for the humidity in commercial equipment (approx. 18 weight percent) was achieved.

Through continued operations at this facility, further tests to confirm operating characteristics under various conditions and component reliability will be conducted to assess system characteristics of commercial AHAT equipment, while developing scale-up technology for application in a demonstration plant, to realize small-medium class ( ~ 200MW-class) highly efficient gas turbine generation systems.