Steam turbine power-generation plant and steam turbine

Details Steam turbine power-generation plant and steam turbine Steam turbine power-generation plant and steam turbine

2000-06-28

2002-03-19

Look, Edward K. (Department: 3745)

Rotary kinetic fluid motors or pumps

Working fluid passage or distributing means associated with...

Specific casing or vane material

C415S216100

Reexamination Certificate

active

06358004

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a compact steam turbine and particularly to a high temperature steam turbine in which a 12% Cr based steel is used for final stage rotating blade of a low pressure steam turbine.
BACKGROUND ART
The rotating blade for a steam turbine is made from a 12Cr—Mo—Ni—V—N steel at the present time. In recent years, there is a desire to improve the thermal efficiency of the gas turbine from the viewpoint of energy saving and to make the equipment of the gas turbine more compact from the viewpoint of space savings.
To improve the thermal efficiency of a gas turbine and to make the equipment thereof more compact, it is effective to make the blades of the steam turbine longer, and for this purpose, there has been a tendency to make the length of the final stage blades of the low pressure steam turbine longer every year. With such a tendency the service condition for the blades of a steam turbine becomes strict, and as a result, the 12Cr—Mo—Ni—V—N steel is no longer sufficient in strength under the above service conditions, and therefore, it is expected that a new material will be developed having a higher strength. The strength of the material for the blades of the steam turbine is determined by its tensile strength which is a basic mechanical characteristic.
The material for the blades of a steam turbine is also required to exhibit a high toughness in addition to a high strength for ensuring safety against breakage.
As a structural material having a tensile strength higher than that of the conventional 12 Cr—Mo—Ni—V—N steel (martensite based steel), there are generally known a Ni based alloy and a Co based alloy; however, such materials are undesirable as blade materials because of their poor working ability at hot temperatures, poor machinability, and periodic damping characteristic.
A disk material for a gas turbine is known, for example, from Japanese Patent Laid-open Nos. Sho 63-171856 and Hei 4-120246.
In the conventional steam turbine, the maximum steam temperature has been set at 566° C. and the maximum steam pressure has been set at 246 atg.
However, from the viewpoint of exhaustion of fossil fuel such as mineral oil or coal, energy saving, and prevention of environmental pollution, it is desired to increase the efficiency of the thermal power-generation plant, and to increase the efficiency of power-generation, it is most effective to increase the steam temperature of the steam turbine. A suitable material for such a high efficient ultra-high temperature steam turbine is known from Japanese Patent Laid-open No. Hei 7-233704.
The present invention has been made to cope with the recent trend to make the blades of a low pressure steam turbine longer. A suitable material for the rotating blades for a steam turbine is not disclosed in Japanese Patent Laid-open Nos. Sho 63-171856 and Hei 4-120246 at all.
Japanese Patent Laid-open No. Hei 7-233704 discloses a rotor material, a casing material, and the like; however, as described above, the document does not describe a 12% Cr based martensite steel for a final stage rotating blade for a high pressure side turbine-intermediate pressure side turbine integral type steam turbine and a low pressure steam turbine which are operated at high temperatures.
An object of the present invention is to provide a steam turbine operable at a high temperature in a range of 600 to 660° C. by use of ferrite based heat resisting steels, to thereby enhance the thermal efficiency, and a steam turbine power-generation plant using the steam turbine.
Another object of the present invention is to provide a steam turbine operable at each operating temperature in a range of 600 to 660° C. with its basic structure being substantially not changed, and a steam turbine power-generation plant using the steam turbine.
DISCLOSURE OF INVENTION
The present invention provides a steam turbine power-generation plant including a combination of a high pressure turbine, an intermediate pressure turbine and two low pressure turbines, a combination of a high pressure turbine and a low pressure turbine connected to each other and an intermediate pressure turbine and a low pressure turbine connected to each other, or a combination of a high pressure side turbine-intermediate pressure side turbine integral steam turbine and one low pressure turbine or two low pressure turbines connected in tandem with each other, in which the temperature of a steam inlet to a first stage rotating blade of each of the high pressure turbine and the intermediate pressure turbine or the high pressure/intermediate pressure turbine is in a range of 600 to 660° C. (preferably, 600 to 620° C., 620 to 630° C., 630 to 640° C.) and the temperature of a steam inlet to a first stage rotating blade of the low pressure turbine is in a range of 350 to 400° C., characterized in that a rotor shaft, rotating blades, stationary blades, and an inner casing, exposed to the temperature atmosphere of the steam inlet, of each of the high pressure turbine and the intermediate pressure turbine or the high pressure/intermediate pressure turbine are made from a high strength martensite steel containing Cr in an amount of 8 to 13 wt %; and a final stage rotating blade of the low pressure turbine is specified such that a value of [the length of a blade (inch)×the number of revolution (rpm)] is 125,000 or more.
The present invention provides a steam turbine, particularly, a high pressure side turbine-intermediate pressure side turbine integral type steam turbine in which steam discharged from a high pressure side turbine is heated at a temperature equal to or higher than an inlet temperature on the high pressure side and fed in an intermediate pressure turbine, the steam turbine including a rotor shaft, rotating blades planted in the rotor shaft, stationary blades for guiding flow of steam to the rotating blades, and an inner casing for holding the stationary blades, in which the temperature of the steam flowing to a first stage one of the rotating blades is in a range of 600 to 660° C. and the pressure is 250 kgf/cm
2
or more (preferably 246 to 316 kgf/cm
2
) or 170 to 200 kgf/cm
2
, characterized in that the rotor shaft or the rotor shaft, at least a first stage one of the rotating blades, and a first stage one of the stationary blades are made from a high strength martensite steel containing Cr in an amount of 9.5 to 13 wt % (preferably, 10.5 to 11.5 wt %) and having a full temper martensite structure, the martensite steel being specified such that a 10
5
h creep rupture strength thereof at a temperature corresponding to each steam temperature (preferably, 610° C., 625° C., 640° C., 650° C., 660° C.) is in a range of 10 kgf/mm
2
or more (preferably, 17 kgf/mm
2
or more); and the inner casing is made from a martensite cast steel containing Cr in an amount of 8 to 9.5 wt %, the martensite steel being specified such that the 10
5
h creep rupture strength at the temperature corresponding to the steam temperature is in a range of 10 kgf/mm
2
or more (preferably, 10.5 kgf/mm
2
or more).
In the high pressure turbine and the intermediate pressure turbine or the high pressure side turbine-intermediate pressure side turbine integral type steam turbine, preferably, the rotor shaft, at least a first stage one of the rotating blades, and a first stage one of the stationary blades, which are preferably used at a steam temperature of 620 to 640° C., are made from a high strength martensite steel containing 0.05 to 0.20 wt % of C, 0.15 wt % or less of Si, 0.05 to 1.5 wt % of Mn, 9.5 to 13 wt % of Cr, 0.05 to 1.0 wt % of Ni, 0.05 to 0.35 wt % of V, 0.01 to 0.20 wt % of Nb, 0.01 to 0.06 wt % of N, 0.05 to 0.5 wt % of Mo, 1.0 to 4.0 wt % of W, 2 to 10 wt % of Co, and 0.0005 to 0.03 wt % of B, the balance being 78 wt % or more of Fe; and the rotor shaft, at least a first stage one of the rotating blades, and a first stage one of the stationary blades, which are preferably used at a steam temperature of 600 to less than 620° C., are made from a high strength martensite steel conta

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