A gas turbine includes a compressor that compresses air, a plurality of combustors that combusts fuel in the air compressed by the compressor to generate combustion gas, and a turbine that is driven by the combustion gas. The fuel supplied to the combustors is often preheated before being supplied to the combustors to increase the combustion efficiency in the combustors.
Patent Document 1 below discloses a gas turbine plant that preheats fuel supplied to a combustor. This gas turbine plant includes a gas turbine, a heat recovery boiler that generates steam by the heat of exhaust gas from this gas turbine, a steam turbine that is driven by steam generated by this heat recovery boiler, and a preheater that heats the fuel to be supplied to the combustor. A first steam line that supplies the steam generated by the heat recovery boiler as a fuel heat source of the preheater is connected to the preheater. Furthermore, a second steam line that introduces steam that heated the fuel into a transition piece of the combustor is connected to this preheater. In addition, a third steam line that introduces the steam that cooled this transition piece into the steam turbine is connected to the transition piece of the combustor. This gas turbine plant further includes an attemperation spray line that sprays water on the second steam line to cool the steam that flows through the second steam line, that is, the steam that heated the fuel.