JP4208661B2 - Steam turbine power plant having a steam valve device and a steam flow control system including the steam valve device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steam valve device provided in a high-temperature steam flow path of a steam turbine power plant and a steam turbine power plant provided with a steam flow control system including the steam valve device.
[0002]
[Prior art]
In a steam turbine power plant, various steam valves are provided for controlling the flow rate of turbine-driven steam, shutting off steam in an emergency, and the like, which are important elements for the safe operation of the steam turbine.
[0003]
For example, FIG. 5 is a system diagram of one typical steam turbine power generator. Referring to FIG. 5, the steam from the boiler 100 passes through the main steam stop valve 101 and the steam control valve 102 and works in the high-pressure turbine 110, and then reheats the boiler 100 again via the check valve 107. It is heated by the vessel and flows into the intermediate-pressure turbine 111 and the low-pressure turbine 112 through the reheat steam stop valve 103 and the intercept valve 104 to work. The steam that has passed through the low-pressure turbine 112 is returned to water by the condenser 113, and is circulated so as to be boosted by the feed water pump 114 and supplied to the boiler 100 again.
[0004]
In order to increase the operational efficiency of the plant, depending on the plant, the high-pressure turbine bypass valve 105 connected before the main steam stop valve 101 and before the reheater of the boiler 100 or after the reheater of the boiler 100 may be used. A low-pressure turbine bypass valve 106 connected to the condenser 113 is installed so that the boiler system alone can be circulated regardless of the operation of the turbine.
[0005]
These steam valves, in particular, the main steam stop valve 101, the steam control valve 102, the reheat steam stop valve 103, the intercept valve 104, the high pressure turbine bypass valve 105, the low pressure turbine bypass valve 106, and the like are generated in a boiler. It is used in a very harsh environment because of the direct action of steam.
[0006]
FIG. 6 shows a typical structure of a conventional example of such a steam valve. This steam valve includes a pressure vessel portion 4 configured by fixing an upper lid 2 to a valve casing 1 with bolts 3. The valve body 6 is screwed into the valve stem 5, the guide piece 7 that holds the valve stem 5, the strainer 8 that captures foreign matter in the steam, and the valve seat 9. An actuator (not shown) for operating the valve stem 5 in the vertical direction is provided.
[0007]
The steam flowing in from the inlet steam pipe part 12 flows into the steam chamber IR as shown by an arrow A, passes through a flow path formed between the valve body 6 and the valve seat 9 and exits from the outlet steam pipe part 13. It flows out to the arrow B. Further, the valve casing 1 is formed with a pre-valve drain 10 and a post-valve drain 11 which are connected to the steam chamber IR, and has a function of discharging drain accumulated in the steam chamber IR when the turbine is started. Yes.
[0008]
In a thermal power plant using a steam turbine power generation system as shown in FIG. 5, a conventional main steam pressure of 24.1 MPa, a main steam temperature of 538 ° C., and a reheat steam temperature of 566 ° C. have been typically employed in Japan. It was. However, since the oil shock, energy conservation has been strongly promoted, and since the subsequent rapid interest in global warming, the main steam and reheat steam temperatures have been increased to 593 to achieve high efficiency of thermal power plants. It rises in steps such as ℃, 600 ℃, and 610 ℃. This tendency tends to increase further in recent years, and the use of steam temperatures of 630 ° C., 650 ° C., 700 ° C. and 725 ° C. or higher is being studied.
[0009]
Under such main steam and reheat steam temperature conditions generally exceeding 600 ° C., chromium (Cr) -molybdenum (Mo) -vanadium (V) steel that has been conventionally used as a valve casing material for these steam valves. Therefore, it is difficult to use a low alloy heat resistant steel such as a ferritic alloy represented by the above, and it is necessary to use an austenitic heat resistant steel or a Ni-based alloy heat resistant steel. However, austenitic heat-resisting steel is not only expensive, but its proof strength at high temperatures is not necessarily high, and its thermal expansion coefficient is relatively large, so it is preferable to use it as a thick valve casing material at high temperature and high pressure. Absent.
[0010]
By the way, it is well known that when such a thick steam valve is used, thermal stress is generated due to a temperature difference between the casing inner surface and outer surface of the steam valve, which is not preferable from the viewpoint of the life of the casing. . Therefore, in order to suppress the generation of the thermal stress as much as possible, a casing having a double structure is known in which a warming fluid or the like is circulated between the double casings to suppress a temperature difference between the inside and outside of the casing. (For example, patent document 1).
[0011]
However, since the above-described steam valve suppresses the fluid or the like that flows between the casings while monitoring the temperature difference between the inside and outside of the casing, the structure is complicated and not necessarily suitable for practical use.
[0012]
[Patent Document 1]
Japanese Patent Laid-Open No. Sho 62-237909
[Problems to be solved by the invention]
Accordingly, a main object of the present invention is to provide a steam valve device capable of stable control of high-temperature and high-pressure steam, and a steam turbine power plant including the steam valve device, despite relatively economically, by optimal arrangement of materials. Objective.
[0014]
[Means for Solving the Problems]
According to the present invention, an inner steam chamber serving as a main steam channel is provided on the inner side, and an inner valve casing that houses a valve seat and a valve body that is provided so as to be movable back and forth with respect to the valve seat, and a main portion of the inner valve casing An outer valve casing defining an outer steam chamber surrounding the outer valve chamber, the inner valve casing and the outer valve casing are formed of relatively high temperature heat resistant steel and low temperature heat resistant steel, respectively, and the outer steam chamber is pressurized A steam valve device is provided that is configured to introduce a cooling fluid.
[0015]
According to the present invention, there is also provided a steam turbine power plant including a steam turbine and a drive steam flow control system for the steam turbine including at least one steam valve device of the present invention.
[0016]
In the steam valve described in JP-A-62-237009, the steam for warming up is placed in the outer steam chamber so as to alleviate the temperature difference between the inner and outer walls generated in the steam valve at the start-up of the steam turbine. In the steady operation as in the present invention, the burden as a high temperature / high pressure partition to the inner valve casing made of high temperature heat resistant steel is introduced into the outer steam chamber, and the low temperature heat resistance No consideration is given to stable control of high-temperature and high-pressure steam by sharing the outer valve casing with steel.
[0017]
【Example】
Hereinafter, the present invention will be described more specifically based on examples.
[0018]
1 is a cross-sectional view of a steam valve used as a main steam stop valve in the system diagram of FIG. 5 as an embodiment of the steam valve device of the present invention, and FIG. 2 is an external perspective view thereof, corresponding to FIG. The same reference numerals are given to members to be performed. 1 and 2, the steam valve surrounds an inner valve casing IC that defines an inner steam chamber IR that forms a substantially inverted L-shaped main steam flow path, and a main portion of the inner valve casing IC. The outer valve casing OC that defines the outer steam chamber OR to be used is a main component. The inner valve casing IC includes a main steam inlet pipe (part) 12 positioned horizontally (preferably also in practice), a central casing part 21 and an outlet pipe (part preferably) also in the figure (preferably also actually). ) 13 and an upper lid 22 is fixed to the central casing portion 21 with bolts 23 to define the upper part of the inner steam chamber IR. All of these members are practical in high temperature heat resistant steel, for example, 700 ° C. or higher. Made of austenitic alloy steel or Ni-base alloy steel having high strength. A valve seat 9 is provided at the jaw portion that moves from the upper portion of the outlet pipe (portion) 13 to the central casing 21, and a valve body 6 fixed to the valve rod 5 is disposed at the upper portion of the upper portion of the valve rod 5. By an actuator (not shown) arranged in the vertical direction, it is arranged so as to move up and down in the vertical direction, that is, to move forward and backward with respect to the valve seat 9. Further, the inlet pipe (part) 12 and the outlet pipe (part) 13 are connected to the main steam inlet pipe and the outlet pipe (both not shown) by flanges 24 and 25, respectively.
[0019]
The outer valve casing OC that defines the outer steam chamber OR that surrounds the main portion of the steam inner valve casing IC (that is, the central casing portion 21 that houses the valve body 6 and includes the valve seat 9) has a flange portion 26. A partition member (typically referred to as “outer valve casing”) 27 is divided into two halves by dividing it on a center line X indicated by a one-dot chain line in the drawing of the main steam inlet pipe (portion) 12 of the inner valve casing IC. That is, the upper half body 27a and the lower half body 27b are structured such that they are locked to each other by a plurality of bolt / nut mechanisms in the flange portion 26. As will be described later, since the pressurized cooling fluid is introduced into the outer steam chamber OR partitioned by the outer valve casing OC and the outer valve casing 27 is cooled from the inner wall thereof, the outer valve casing 27 is made of low temperature heat resistant steel. For example, a low alloy heat resistant steel such as a ferritic alloy typified by Cr—Mo—V steel having a heat resistant temperature of about 570 ° C. can be sufficiently constituted.
[0020]
Further, the outer valve casing 27 is joined to the guide piece 7 of the valve stem 5, the inlet pipe (part) 12 and the outlet pipe (part) 13 of the inner valve casing IC at, for example, a seal ring divided into two or three parts. Are stacked in multiple layers, respectively, and are provided with flanges for an actuator (not shown) arranged at the end of the valve stem 5 and inlet and outlet steam pipes (not shown). The outer valve casing 27 can be disassembled and assembled without removing the joints 24 and 25. In addition, after removing the upper half 27a of the outer valve casing 27 after disassembly, the inner lid 22 of the inner valve casing IC is exposed, the bolt 23 is removed, and the inner lid 22 is removed to remove the inner lid 22 from the inner steam chamber IR. Maintenance inspection can also be performed easily.
[0021]
The outer valve casing OC is supported on a pedestal or the like by a support mechanism (not shown). The inner valve casing IC is supported by the outer valve casing OC via a holding mechanism 30 formed of a rigid joint such as an embedded bolt embedded to join the inner and outer casings. A plurality of, for example, three holding mechanisms 30 may be provided on a plane perpendicular to the center line Y of the main steam outlet pipe (part) 13 and including the center line X of the main steam inlet pipe (part) 12. preferable. As a result, even when the inner and outer casings are thermally expanded, it is possible to prevent a load from acting in a direction perpendicular to the respective axes of the seal rings 28a, 28b and 28c.
[0022]
In the steam valve device of this example, an orifice 29 for introducing low-temperature / low-pressure steam as pressurized cooling fluid from the inner steam chamber IR into the outer steam chamber OR is close to the valve seat 9 of the inner valve casing IC. A pre-valve drain 10 provided at the upstream position and connected to the pressure regulating valve 31 by piping is provided at the bottom of the outer valve casing OC. Further, in order to discharge the steam leaked into the gap between the valve stem 5 and the guide piece 7 to the outside of the system, a hole-like valve stem leak-off 32 opened in the guide piece is provided and led to the outer surface of the outer valve casing OC. Piping is combined.
[0023]
Hereinafter, the operation of the steam valve shown in FIG. 1 (and FIG. 2) described above will be described.
[0024]
For example, the main steam flow A having a pressure of 25 MPa and a temperature of 700 ° C. is introduced into the inner steam chamber IR, and is moved forward and backward by the valve body 6 driven by an actuator (not shown) through the valve rod 5 to the valve seat 9. While exiting the inner steam chamber IR while being opened and closed, a part thereof is cooled by expansion when passing through the orifice 29, for example, a low temperature / low pressure at a pressure of 11-13 MPa and a temperature of 540-570 ° C. Steam (pressurized cooling fluid) is introduced into the outer steam chamber. As a result, the outer valve casing 27 is maintained at 570 ° C. or lower including the inner wall, and a configuration using low temperature heat resistant steel becomes possible. Since the orifice 29 is provided at an upstream position close to the valve seat 9, it also has a function as a drain discharge hole for the inner steam chamber, and the drain before the valve seat provided at the bottom of the outer valve casing 10. 10, condensate water that causes erosion of the valve seat 9 and the valve body 6 can be removed before the valve seat. The drain 10 in front of the valve seat is connected to the pressure control valve 31 by piping, and the operation of the control valve 31 enables the pressure (and temperature) in the outer steam chamber OR to be adjusted. That is, if the set pressure of the outer steam chamber OR is increased, the amount of steam flowing out from the drain 10 is reduced, and the pressure (and temperature) in the outer steam chamber is increased. On the other hand, if the set pressure of the outer steam chamber OR is lowered, the amount of steam flowing out from the drain 10 increases, and the pressure (and temperature) of the outer steam chamber OR decreases.
[0025]
In general, in order to effectively achieve the reduction of the pressure-resistant burden of the inner valve casing and the reduction of the heat-resistant burden of the outer valve casing, which are the objects of the present invention, the pressure and temperature in the outer steam chamber are compared with those in the inner steam chamber, It is desirable to reduce the pressure to 45 to 52% and the temperature to 130 to 160 ° C. For this purpose, it is preferable to provide about 4 to 8 orifices 29 having a diameter of 8 to 12 mm.
[0026]
(Modification)
In the above, as a preferable aspect of the steam valve device of the present invention, a part of the main steam flowing in the inner steam chamber is adiabatically expanded through the orifice 29 to introduce a low-pressure, low-temperature steam flow into the outer steam chamber. The configuration. However, for the purpose of optimizing both casing materials by reducing the pressure-resistant burden of the inner valve casing and the heat-resistant burden of the outer valve casing, which are the objects of the present invention, the above is determined in relation to the main steam pressure and temperature. Any fluid having a reduced pressure and temperature can be used as the pressurized cooling fluid. For example, a part of the steam flow having an appropriate pressure and temperature is branched from an arbitrary position of the steam turbine plant, such as a high-pressure turbine outlet steam flow, and introduced into the outer steam chamber, so that the formation of the orifice 29 is omitted. You can also.
[0027]
However, in the embodiment described above with reference to FIG. 1, it is possible to construct a high-temperature / high-pressure steam valve compactly as a whole without providing additional piping by using the orifice 29. In combination, it is very preferable because it provides an important advantage of preventing erosion of the main part of the valve.
[0028]
(Other variations)
Next, another modified example of the steam valve device of the present invention will be described with reference to FIGS. 3 and 4 (the same members as those in FIGS. 1 and 6 are denoted by the same reference numerals). .
[0029]
In the modification shown in FIG. 3, as an example of the case where a material having a large thermal expansion such as austenitic heat-resistant alloy steel is adopted for the inner valve casing IC, the inner valve casing is held in order to smoothly absorb the thermal expansion at its own weight support point. As the mechanism 30, a variable angle joint holding mechanism is used between the weight support point of the inner valve casing and the non-opposing position of the outer casing. That is, the weight support point of the inner casing is used as the inner joint 34, and the weight of the inner valve casing is connected. This is a structure in which the support is performed at the support point outer joint 35 of the outer valve casing OC via the rod 33. The inner joint 34 and the outer joint 35 have a universal joint structure and absorb the thermal expansion of the inner casing. Further, since the connecting rod 33 is thermally expanded in the same manner as the outer valve casing, the relative position between the inner joint 34 and the connecting rod 33 hardly changes.
[0030]
Further, in the modification shown in FIG. 4, a tropical zone 36 made of the same material as the inner casing is provided between the inner valve casing IC and the seal rings 28b and 28c. A gap is provided between the tropical zone 36 and the inner valve casing to reduce the temperature of the contact surface with the seal ring 28 and reduce the temperature deterioration of the seal rings 28 and 28c.
[0031]
In the above description, the steam valve device of the present invention has been described with an example of the main steam stop valve. However, an essentially similar structure can also be used as an adjusting valve and an intercept valve. Therefore, the steam valve of the present invention having the structure described with reference to FIGS. 1 to 4 is used for any of the steam valves 101 to 106 of the steam turbine power plant described with reference to the system diagram of FIG. The inventive steam turbine power plant is obtained.
[0032]
【The invention's effect】
As described above, according to the present invention, the high-temperature / high-pressure steam valve has an inner / outer double valve casing structure, and the pressurized / cooling fluid is introduced into the outer steam chamber defined by the outer valve casing. The pressure resistance burden and the heat resistance burden of the outer valve casing are alleviated significantly, and the casing material can be optimized. As a result, according to the present invention, it is possible to obtain a steam valve device capable of stably controlling high-temperature and high-pressure steam, and a steam turbine power plant including the same, although it is relatively economical. In addition, the steam valve device is made compact by providing an orifice in the inner valve casing near the valve seat, adiabatic expansion of the main steam through the orifice, and using a low-temperature and low-pressure steam flow as the pressurized cooling fluid. The erosion of the valve main part can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an embodiment of a steam valve of the present invention.
FIG. 2 is an external perspective view of the steam valve of FIG.
FIG. 3 is a cross-sectional view of another embodiment of the steam valve of the present invention.
FIG. 4 is a cross-sectional view of another embodiment of the steam valve of the present invention.
FIG. 5 is a system diagram of a steam turbine power plant equipped with a steam flow control system including a steam valve of the present invention.
FIG. 6 is a cross-sectional view of a conventional steam valve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steam valve casing 2 Upper cover 3 Bolt 4 Pressure vessel 5 Valve rod 6 Valve body 7 Guide piece 8 Stoner 9 Valve seat 10 Drain 11 before valve seat Drain 12 after valve seat Inlet pipe (part)
13 Outlet pipe (part)
21 Central casing 22 Inner top lids 24, 25 Flange 27 Outer valve casing members 28a to 28c Seal mechanism 29 Orifice 30 Holding mechanism 31 Pressure adjustment valve 32 Valve stem leak-off IC Inner valve casing OC Outer valve casing

Claims (13)

  An inner steam chamber that is provided with an inner steam chamber serving as a main steam flow path and accommodates a valve seat and a valve body that can be moved forward and backward with respect to the valve seat, and an outer steam chamber that surrounds a main portion of the inner valve casing An outer valve casing that divides the inner valve casing and the outer valve casing from a relatively high temperature heat resistant steel and a low temperature heat resistant steel, respectively, and a pressurized cooling fluid is introduced into the outer steam chamber. A steam valve device characterized by comprising   The inner valve casing is provided with an orifice for communicating the inner and outer steam chambers, and a part of the steam in the inner steam chamber is expanded through the orifice so that relatively low-temperature and low-pressure steam as a pressurized cooling fluid is supplied to the outer steam chamber. The steam valve device according to claim 1, wherein the steam valve device is introduced.   The steam valve device according to claim 2, wherein the orifice is opened at an upstream side portion adjacent to the valve seat of the inner valve casing, and the orifice also acts as a drain before the valve seat.   The steam valve device according to any one of claims 1 to 3, wherein the high-temperature heat-resistant steel is austenitic alloy steel or Ni-base heat-resistant alloy steel, and the low-temperature heat-resistant steel is low-alloy steel.   The steam valve device according to any one of claims 1 to 4, wherein the outer valve casing is divided on the center line of the main steam inlet pipe.   The steam valve device according to claim 5, wherein the divided outer valve casings have a flange portion and are joined by a flange joint.   The main steam flow path connecting the main steam inlet pipe and the main steam outlet pipe constituting the inner valve casing is substantially orthogonal to the L shape, and a seal is provided at the joint between the main steam inlet pipe and the outer valve casing in the main steam outlet pipe. The steam valve device according to any one of claims 1 to 5, wherein a mechanism is provided.   The steam valve device according to claim 7, wherein the seal mechanism has a divided structure.   The steam valve device according to claim 7 or 8, wherein a tropical zone is arranged between the outer wall of the inner valve casing and the seal mechanism.   The steam valve device according to any one of claims 1 to 9, wherein a weight support point of the inner valve casing is provided at a position facing the outer valve casing on a plane including the center line of the main steam inlet pipe.   The steam valve device according to claim 10, further comprising a rigid joint holding mechanism between a weight support point of the inner valve casing and an opposed position of the outer valve casing.   The steam valve device according to claim 10, further comprising a variable angle joint holding mechanism between a weight support point of the inner valve casing and a non-opposing position of the outer valve casing.   A steam turbine power plant including a steam turbine and a drive steam flow control system for the steam turbine including at least one steam valve device according to any one of claims 1 to 12.

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