Steam-turbine power plant and steam turbine

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

1998-05-11

2001-01-16

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

Working fluid passage or distributing means associated with...

Plural rigidly related blade sets

C415S100000, C415S103000, C415S200000, C415S216100, C416S24100B, C060S039780, C148S325000, C148S333000

Reexamination Certificate

active

06174132

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel steam turbine of high efficiency and high temperature, and more particularly to a steam turbine in which a main steam temperature and/or a reheat steam temperature are/is 620 (° C.) or above. It also relates to a steam-turbine power plant which employs such steam turbines.
2. Description of the Related Art
Conventional steam turbines have had a steam temperature of 566 (° C.) at maximum and a steam pressure of 246 (atg).
It is desired, however, to heighten the efficiencies of thermal power plants from the viewpoints of the exhaustion of fossil fuel such as petroleum and coal, the saving of energy, and the prevention of environmental pollution. For enhancing the power generation efficiencies, it is the most effective expedient to raise the steam temperatures of the steam turbines. Regarding materials for such high-efficiency turbines, 1Cr-1Mo-¼V ferritic low-alloy forged steel and 11Cr-1Mo-V-Nb-N forged steel are known as rotor materials, while 1Cr-1Mo-¼V ferritic low-alloy cast steel and 11Cr-1Mo-V-Nb-N cast steel are known as casing materials. Among these materials, austenitic alloys disclosed in the official gazette of Japanese Patent Applications Laid-open No. 180044/1987 and No. 23749/1986, and martensitic steel disclosed in the official gazette of Japanese Patent Applications, Laid-open No. 147948/1992, No. 290950/1990 and No. 371551/1992 are especially known as materials whose high-temperature strengths are superior.
Although, in the laid-open applications mentioned above, the rotor materials, the casing materials, etc. are disclosed, almost no consideration is given to the steam turbines and the thermal power plants which are accompanied by the higher steam temperatures as stated above.
Further, a supercritical steam turbine is known from the official gazette of Japanese Patent Applications, Laid-open No. 248806/1987, but a plant system as a whole is not considered at all.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a steam turbine which permits a heightened steam temperature of 610-660 (° C.) by heat-resisting ferritic steel and which exhibits a high thermal efficiency, and a steam-turbine power plant which employs the steam turbine.
Another object of the present invention is to provide steam turbines whose running temperatures are 610-660 (° C.) and whose basic designs are substantially the same, and a steam-turbine power plant which employs the steam turbines.
The present invention relates to improvement to a steam-turbine power plant having a high-pressure turbine and an intermediate-pressure turbine which are joined to each other, and low-pressure turbines which are connected in tandem. The improvement comprises that steam inlet of each of the high-pressure and intermediate-pressure turbines which leads to moving blades of a first-stage included in each of the high-pressure and intermediate-pressure turbines is at a temperature of 610-660 (° C.) (preferably 615-640 (° C.), and more preferably 620-630 (° C.)). Further, that steam inlet of each of the low-pressure turbines which leads to moving blades of a first stage included in each of the low-pressure turbines is at a temperature of 380-475 (° C.) (preferably 400-430 (° C.)), and a rotor shaft, the moving blades, fixed blades and a casing, which are included in each of the high-pressure and intermediate-pressure turbines and which are exposed to the temperature of the steam inlet of each of the high-pressure and intermediate-pressure turbines, are made of high-strength martensitic steel which contains 8-13 (weight-%) of Cr.
Further, the present invention relates to an improvement to a steam-turbine power plant having a high-pressure turbine and an intermediate-pressure turbine which are joined to each other, and low-pressure turbines which are connected in tandem. In the improvement, that steam inlet of each of the high-pressure and intermediate-pressure turbines which leads to moving blades of a first stage included in each of the high-pressure and intermediate-pressure turbines is at a temperature of 610-660 (° C.) (preferably 615-640 (° C.), and more preferably 620-630 (° C.)). Further, that steam inlet of each of the low-pressure turbines which leads to moving blades of a first stage included in each of the low-pressure turbines is at a temperature of 380-475 (° C.) (preferably 400-430 (° C.)), and a rotor shaft, fixed blades and a casing, which are included in each of the high-pressure and intermediate-pressure turbines and which are exposed to the temperature of the steam inlet of each of the high-pressure and intermediate-pressure turbines, are made of high-strength martensitic steel which contains 8-13 (weight-%) of Cr.
Further, the present invention relates to a steam turbine comprising a rotor shaft, moving blades which are assembled on the rotor shaft, fixed blades which guide inflow of steam to the moving blades, and an inner casing which holds the fixed blades. The steam flows into a first stage of the moving blades at a temperature of 610-660 (° C.) and under a pressure of at least 250 (kg/cm
2
) (preferably 246-316 (kg/cm
2
)) or 170-200 (kg/cm
2
). The rotor shaft and, at least, first-stage ones of the moving blades and the fixed blades are made of high-strength martensitic steel of fully-tempered martensitic structure which exhibits a 10
5
-hour creep rupture strength of at least 15 (kg/mm
2
) (preferably 17 (kg/mm
2
)) at a temperature corresponding to the respective steam temperatures (preferably 610 (° C.), 625 (° C.), 640 (° C.), 650 (° C.) and 660 (° C.)), and which contains 9.5-13 (weight-%) (preferably 10.5-11.5 (weight-%)) of Cr, and the inner casing is made of martensitic cast steel which exhibits a 10
5
-hour creep rupture strength of at least 10 (kg/mm
2
) (preferably 10.5 (kg/mm
2
)) at the temperature corresponding to the respective steam temperatures, and which contains 8-9.5 (weight-%) of Cr.
Further, the present invention relates to an improvement to a steam turbine having a rotor shaft, moving blades which are assembled on the rotor shaft, fixed blades which guide inflow of steam to the moving blades, and an inner casing which holds the fixed blades. In the improvement, the rotor shaft and, at least, first-stage ones of the moving blades and the fixed blades are made of high-strength martensitic steel which contains 0.05-0.20 (%) of C, at most 0.15 (%) of Si, 0.03-1.5 (%) of Mn, 9.5-13 (%) of Cr, 0.05-1.0 (%) of Ni, 0.05-0.35 (%) of V, 0.01-0.20 (%) of Nb, 0.01-0.06 (%) of N, 0.05-0.5 (%) of Mo, 1.0-4.0 (%) of W, 2-10 (%) of Co and 0.0005-0.03 (%) of B, and which has at least 78 (%) of Fe, the percentages being given in terms of weight, and the inner casing is made of high-strength martensitic steel which contains 0.06-0.16 (%) of C, at most 0.5 (%) of Si, at most 1 (%) of Mn, 0.2-1.0 (%) of Ni, 8-12 (%) of Cr, 0.05-0.35 (%) of V, 0.01-0.15 (%) of Nb, 0.01-0.8 (%) of N, at most 1 (%) of Mo, 1-4 (%) of W and 0.0005-0.03 (%) of B, and which has at least 85 (%) of Fe, the percentages being given in terms of weight.
Further, the present invention relates to the improvement to a high-pressure steam turbine having a rotor shaft, moving blades which are assembled on the rotor shaft, fixed blades which guide inflow of steam to the moving blades, and an inner casing which holds the fixed blades, wherein the moving blades are arranged including at least 10 stages on each side in a lengthwise direction of the rotor shaft, except a first stage which is of double flow, and the rotor shaft has a distance (L) of at least 5000 (mm) (preferably 5200-5500 (mm)) between centers of bearings in which it is journaled, and a minimum diameter (D) of at least 600 (mm) (preferably 620-700 (mm)) at its parts which correspond to the fixed blades, a ratio (L/D) between the distance (L) and the diameter (D) being 8.0-9.0 (preferably 8.3-8.7), and it is made of high-strength martensitic steel which contains 9-13 (weight-%) of Cr.
Further, the present invention relates to th

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