Increasing efficiency of power generation plants is in progress in response to demands for reduction of carbon dioxide, resource conservation, and the like. Specifically, increasing temperature of working fluid of a gas turbine and a steam turbine, employing a combined cycle, and the like are actively in progress. Further, research and development of recovery technology of carbon dioxide are in progress.
FIG. 8 is a system diagram of a conventional gas turbine facility 300. FIG. 9 is a view schematically illustrating a vertical section of a combustor 313 provided at the conventional gas turbine facility 300. In the conventional gas turbine facility 300, a turbine is operated while using carbon dioxide and water vapor generated in a combustor as working fluid, and a part of carbon dioxide exhausted from the turbine is circulated.
As illustrated in FIG. 8, in the conventional gas turbine facility 300, oxygen separated from an air separator (not-illustrated) is introduced to a pipe 340. The oxygen is then compressed in a compressor 310, and its flow rate is controlled by a flow rate regulating valve 311. The oxygen passing through the flow rate regulating valve 311 is heated by receiving heat from later-described combustion gas in a heat exchanger 312, and is supplied to combustor 313.
Fuel is guided from a fuel supply source (not-illustrated) to a pipe 341. The fuel is regulated in flow rate by a flow rate regulating valve 314 and is supplied to the combustor 313. This fuel is hydrocarbon.
As illustrated in FIG. 9, the oxygen supplied from the pipe 340 and the fuel supplied from the pipe 341 react (combat) in the combustor 313. Combustion gas containing carbon dioxide and water vapor is generated by this combustion. The flow rates of fuel and oxygen are regulated to be of a stoichiometric mixture ratio (theoretical mixture ratio) in a state that they are completely mixed.
The combustion gas generated 319 is combustor 313 is introduced to a turbine 315. Note that, for example, a generator 319 is coupled to the turbine 315, as illustrated in FIG. 8. The combustion gas which performed an expansion work in the turbine 315 passes through the heat exchanger 312. At this time, heat is emitted, and the oxygen flowing in the pipe 340 and the carbon dioxide flowing in a pipe 343 are heated.
The combustion gas passing through the heat exchanger 312 then passes through a cooler 316. At this time, the water vapor in the combustion gas condenses into water. The water passes through a pipe 342 and is exhausted to the outside.
The carbon dioxide separated from the water vapor compressed in a compressor 317 interposed in the pipe 343 to become supercritical fluid. A part of the compressed carbon dioxide is introduced to a pipe 344 branched off from the pipe 343. The carbon dioxide introduced into the pipe 344 is regulated in flow rate by a flow rate regulating valve 318 and is exhausted to the outside.
Meanwhile, a remaining part of the carbon dioxide flows in the pipe 343. Then, the carbon dioxide is heated in the heat exchanger 312 and is supplied into a combustor casing 350 accommodating the combustor 313 as illustrated in FIG. 9. A temperature of the carbon dioxide passing through the heat exchanger 312 is about 700° C. Here, the combustor casing 350 is constituted by an upstream side casing 351a and a downstream side casing 351b. 
The carbon dioxide guided into the upstream side casing 351a flows toward the turbine 315 between the downstream side casing 351b and a combustor liner 352, a transition piece (tail pipe) 353.
When the carbon dioxide flows between the downstream side casing 351b and the combustor liner 352, the transition piece 353, the carbon dioxide cools the combustor liner 352 and the transition piece 353. This cooling is performed by, for example, porous film cooling, or the like. A part of the carbon dioxide is introduced into the combustor liner 352 and the transition piece 353 from hole 354, 556 of a porous film cooling part, dilution holes 355, and so on, as illustrated in FIG. 9. Besides, the carbon dioxide is also used for cooling of stator blades 360 and rotor blades 361 on the turbine 315.
The carbon dioxide introduced into the combustor liner 352 and the transition piece 353 is introduced to the turbine 315 together with the combustion gas produced by combustion. As stated above, the carbon dioxide other than the one exhausted from the pipe 344 circulates in the system.
Here, the upstream side casing 351a and the downstream side casing 351b are exposed to high-temperature carbon dioxide. The upstream side casing 315a and the downstream side casing 351b are therefore composed of an expensive Ni-based alloy.
As described above, in the convention gas turbine facility 300, the combustor casing 350 exposed to the high-temperature carbon dioxide has to be composed of the expense Ni-based alloy. Accordingly, a manufacturing cost of the gas turbine facility increases.
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