Heat recovery steam generator and power plant (toshiba) electricity voltage in usa

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This application is a divisional application and claims the benefit of priority under 35 U.S.C. § 120 to U.S. application Ser. No. 14/007,141, filed Sep. 24, 2013, which is a U.S. national stage application of PCT/JP2012/057784, filed Mar. 26, 2012, and claims the benefit of priority from Japanese Patent Application No. 2011-67530 filed on Mar. 25, 2011, the entire contents of each of which are incorporated herein by reference. TECHNICAL FIELD

In recent year, combined-cycle power generation currently becomes the major steam in thermal power plants, in order to improve thermal efficiency of the plants. A combined-cycle power plant is a power plant in which a heat recovery steam generator is combined with a gas turbine and a steam turbine. A combustor provides the gas turbine with combustion gas of high temperature and high pressure. The gas turbine is revolved by expansion of the combustion gas so that a generator is rotated. Thereafter, exhaust gas is introduced into the heat recovery steam generator. In the heat recovery steam generator, steam is generated by utilizing thermal energy of exhaust gas. Steam is supplied to the turbine, and the generator is rotated by the steam turbine in collaboration with the gas turbine.

In general, a conventional heat recovery steam generator is a boiler which generates steam corresponding to heat of exhaust gas discharged from the gas turbine in order to supply steam to the steam turbine. A heat recovery steam generator provided with an auxiliary burner, which is capable of heating up exhaust gas, has been prevails in recent year. This is because decrease in the output of the gas turbine in the summer season results in reduction in an exhaust gas amount, so that it is necessary to compensate decrease in amount of steam generated by the heat recovery steam generator, and because steam should be also supplied to a cogeneration plant, a distilling plant and so on, in addition to the steam turbine.

In a newly developed heat recovery steam generator, an auxiliary burner shows a tendency to have a large size, with a view to increasing a steam supply amount. As a result of it, as exhaust gas temperature in the heat recovery steam generator rises, auxiliary burners are installed on a plurality of locations for the purpose of preventing the generator constituent parts from deteriorating the durability and reliability (see 3P2001-116208A, for example). DISCLOSURE OF THE INVENTION

In the heat recovery steam generator including the auxiliary burner, a thermal balance inside the heat recovery steam generator shows a large difference between when the auxiliary burner is fired to heat exhaust gas and when the auxiliary burner is ceased. In particular, in the heat recovery steam generator where auxiliary burners are installed on a plurality of locations, the excessive increase of evaporation amount may results in lowering the degree of superheating of steam or raising the degree of superheating of steam excessively.

Accordingly, in the heat recovery steam generator including a plurality of auxiliary burners, it is necessary to distribute fuel to each auxiliary burner properly. However, when fuel to be charged to one auxiliary burner is increased so as to increase the steam amount, steam temperature at a generator outlet may drop because of the increase in the steam amount. In order to cope with this, when fuel to the other auxiliary burner is increased in order to raise the steam temperature, this results in excessive superheating. There is a problem that controlling process of fuel amount becomes complicated in order to distribute fuel to each of auxiliary burner properly.

Therefore, the object of the present invention is to provide a heat recovery steam generator that can solve the above problem of the prior art, and can adequately distribute fuel to auxiliary burners located on a plurality of positions in the heat recovery steam generator, depending on an operation condition of the heat recovery steam generator.

Another object of the present invention is to provide a power plant including a heat recovery steam generator that can adequately distribute fuel to auxiliary burners located on a plurality of positions in the heat recovery steam generator, depending on an operation condition of the heat recovery steam generator.

In order to achieve the aforementioned object, a heat recovery steam generator according to an embodiment of the present invention is a heat recovery steam generator in which a plurality of heat exchangers consisting of a superheater, an evaporator and an economizer are installed in a duct along a flow direction of exhaust gas from a gas turbine, so as to generate steam by utilizing the exhaust gas of the gas turbine, the heat recovery steam generator comprising:

a fuel distribution control means configured to control distribution of fuel charged to each of the first stage auxiliary burner and the second stage auxiliary burner, in accordance with a predetermined distribution ratio of each charging quantity to whole charging quantity in all the range thereof.

a heat recovery steam generator in which a plurality of heat exchangers consisting of a superheater, an evaporator and an economizer are installed in a duct along a flow direction of an exhaust gas from the gas turbine, so as to generate steam by utilizing the exhaust gas of the gas turbine;

a fuel distribution control means configured to control distribution of fuel charged to each of the first stage auxiliary burner and the second stage auxiliary burner, in accordance with a predetermined distribution ratio of each charging quantity to whole charging quantity in all the range thereof. BRIEF DESCRIPTION OF THE DRAWINGS