A 145-MW blast furnace gas firing gas turbine combined cycle plant was designed and installed in a steel works in Japan as a repowering unit. A 124-MW large-scale gas turbine with turbine inlet temperature 1150°C (1423 K) was adopted as a core engine for the combined cycle plant. The fuel of this gas turbine is blast furnace gas mixed with coke oven gas. These are byproducts of steel works, and the calorific value of the mixed gas is controlled to be about 1000 kcal/Nm3 (4187 kJ/Nm3). A specially designed multicannular type combustor was developed to burn such a low Btu fuel. The gas turbine, generator, steam turbine, and fuel gas compressor are connected to make a single-shaft configuration. As a result of introducing the gas turbine combined cycle plant, the plant thermal efficiency was above 45 percent (at NET) and the total electricity generation in the works has increased from 243 MW to 317 MW. This paper describes the design features of this combined cycle plant.

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