JPS59134307A - Steam turbine plant - Google Patents

Abstract

PURPOSE:To prevent the occurrence of excessive thermal stress against machinery and equipment available as well as to aim at improvements in heat recovery, by leading high pressure steam into a vortex tube device, then cooling a turbine with low temperature steam and driving the turbine or performing its feed water heating with the high pressure steam. CONSTITUTION:A steam turbine plant consists of a boiler 1, steam turbines 2-5, a condenser 7 and a feed water system. The partial steam produced in the boiler 1 is led into a vortex tube device 22 through which separation into high pressure steam and low temperature steam takes place. Heat recovery also takes place in a way of interconnecting high and pressure steam 25 to an exhaust system 15 of a superhigh pressure turbine 2. Likewise, high and low pressure steam 23 is interconnected to a cooling system of the superhigh pressure turbine 2. In this manner, not only the occurrence of excessive thermal stress against machinery and equipment available can be prevented but also heat recovery from the steam that is used for cooling can be brought about.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to cooling of steam turbines, and more particularly to cooling technology for steam turbine plants driven by ultra-high temperature and high pressure steam.

[Prior art]

As oil prices soar, coal-fired power is becoming the mainstream for newly built thermal power plants. However, coal-fired power plants have the drawback that the proportion of auxiliary power is relatively large due to coal fuel pretreatment, dust removal, etc., and the plant efficiency is lower than that of oil-fired power plants. Under these circumstances, measures to improve the power generation efficiency of coal-fired power plants are being considered from various angles.

As one of these methods, a method has been proposed in which the inlet steam conditions are further increased in temperature and pressure to improve power generation efficiency. It is known that the efficiency of the Rankine cycle improves as the pressure increases, but this becomes more noticeable at higher temperatures. In this case, a plant configuration example as shown in FIG. 1 is usually used. That is, as shown in FIG. 1, in a turbine plant consisting of a boiler 1, a high-pressure turbine 3, an intermediate-pressure turbine 4, a low-pressure turbine 5, a generator 6, a condenser 7, etc., the boiler 1 and the high-pressure turbine 3 are An ultra-high pressure turbine 2 is provided in between, and main steam 14 from the boiler 1 is guided to the ultra-high pressure turbine 2, and the exhaust gas 15 is returned to the boiler 1 and reheated, and then reheated steam 16 is introduced to a conventional high-pressure turbine 3. It's a system. The plant configuration after the high-pressure turbine 3 is the same as that of a conventional thermal power plant. a second stage reheat steam system 18 to the intermediate pressure turbine 4, a connecting pipe 19 that leads the exhaust gas of the intermediate pressure turbine 4 to the low pressure turbine 5, a condensate pump 8, low pressure feed water heaters 9, 10, and a deaerator 11.
, a water supply pump 12, a high-pressure water supply heater 13, a boiler water supply system 20, etc.

In such a so-called ultra-high-pressure high-temperature steam turbine plant, the main steam pressure ranges from 246 Kg f/crA to 352 Kg f/crtxXiK degrees from 538 Kg to 649 Kg f/crA.
Since the turbine casing, rotor shaft, blades, etc. of the ultra-high pressure turbine 2 are exposed to an atmosphere of high-temperature and high-pressure steam due to the high pressure and high temperature of the ultra-high-pressure turbine 2, there is a strong demand for materials with high heat and pressure resistance. However, these heat-resistant materials generally have the disadvantage that the greater their high-temperature strength, the worse their workability and weldability become, which is one of the causes of increased costs for steam plants. Furthermore, in ultra-high temperature and high pressure power generation plants,
As the steam conditions become high in temperature and pressure, restrictions are placed on structures such as turbine casings and piping to alleviate thermal stress and absorb differences in elongation, which poses a major problem. In particular, in the ultra-high pressure stage 2 shown in FIG. 1, it is absolutely necessary to provide cooling protection for the normally used inner and outer casings and rotor shaft.

An example of this cooling method is to branch off a part of the main steam and mix it with high-pressure, low-temperature water to lower the temperature and remove moisture. In this case, a huge amount of mixing space is required to uniformly mix the steam and cooling water, and in this case, a small amount of moisture remains in the steam (p1) If this hits the object to be cooled, the cooling effect of the water will be excessive. It has the disadvantage that the temperature suddenly drops and cracks occur due to thermal stress.

[Purpose of the invention]

An object of the present invention is to provide a steam turbine plant in which the optimum cooling steam is obtained for the steam turbine, thereby preventing excessive thermal stress from occurring in equipment, and in which heat is recovered from the steam used for cooling. It's about doing.

[Summary of the invention]

A feature of the present invention is that high-pressure steam supplied from a boiler or high-pressure steam branched from a high-pressure stage of a steam turbine is introduced into a portex tube device and separated into low-temperature steam and high-temperature steam. The separated high-temperature steam is used as the drive steam of the steam turbine or the heating steam of the feed water heating device installed in the condensing system for heat recovery. It is located in a planned steam turbine plant.

[Embodiments of the invention]

Hereinafter, a specific implementation of the present invention will be explained with reference to FIGS. 2 to 10.
This will be explained in detail using figures.

2 to 6 show a steam turbine plant including an ultra-high temperature, high pressure steam and pressure turbine 4, a low pressure turbine 5, a generator 6, a condenser 7, etc. according to the present invention, in which the main steam 14 is connected to the portex tube 22. Cooling steam system 2
1, and a high-pressure low-temperature steam system 23 that is separated within the portex tube 22 and communicates with the cooling system of the structure of the ultra-high pressure turbine 2. In addition, a high-temperature cooling steam system 24 is installed to cool the structure and return heated and cooled steam,
In order to recover this heat, the high pressure turbine exhaust steam system 1
7, and also communicates with the ultra-high pressure turbine exhaust system 15 in order to recover heat from the high pressure high temperature steam 25 separated within the portex tube 22.
and configure it.

In the embodiment shown in FIG. Although an example is shown in which the return destinations of high-pressure, high-temperature steam are guided to the high-pressure turbine exhaust steam system 17 and the ultra-high-pressure turbine exhaust steam system 15, respectively, this does not have a limited meaning. Depending on the temperature and cooling load of the structure of the ultra-high-temperature turbine 2, for example, as shown in FIG. You can also do that. In addition, as shown in FIG. 4, when starting up the turbine, the high-pressure, high-temperature steam 25 separated by the sivoltex tube 22 is guided to the ultra-high-pressure turbine 2 by operating the switching valves 46 and 47 to quickly start up the ultra-high-pressure turbine 2, and the high-pressure, low-temperature steam system 23 can also be returned to the low pressure feed water heater 10 via line 51 for heat recovery. Further, as shown in FIG. 5, the high pressure and high temperature steam system 25 can be returned to the total reheat steam system 16. Alternatively, as shown in FIG. 6, the high-pressure, high-temperature steam system 25 can be guided through the system 52 to a dry heater 48 installed in the boiler feed water system 20 to heat the feed water, and then returned to the low-pressure feed water heater 10. These matters are determined from the optimum conditions of the plant thermal cycle.

Further, in the above-mentioned embodiment, the portex tube 22 was described as one stage for simplicity, but in the case of Tenkawa, it is connected in multiple stages and used so that a predetermined low-temperature steam can be obtained.

By configuring the cooling steam generation system as described above, it becomes possible to generate cooling steam that enables heat-resistant protection of the internal structure of the ultra-high pressure turbine 2.

Now, an embodiment of a method of cooling the internal structure of the ultra-high pressure turbine 2 using such a cooling steam generation system will be described using FIGS. 4 to 6.

FIG. 7 is a sectional view showing a typical example of the ultra-high pressure turbine 2. That is, a main steam pipe 26 that introduces ultra-high temperature and high pressure steam from the boiler 1 into the turbine, a so-called nozzle box 27 that guides this main steam to the turbine stage, a plurality of diaphragms 28 that make up the turbine stage, and turbine rotor blades. The rotor disk 34 supports the diaphragm 28, an inner casing 33 that fixes the diaphragm 28, and an outer casing 30 that incorporates these various components into one body. In such an ultra-high pressure turbine 2, id
The ultra-high-temperature, high-pressure steam flowing through the main steam pipe 26 and the nozzle box 27 is accelerated by the stationary vanes held by the diaphragm 28, and by applying rotational force to the rotor disk 34, the pressure and temperature gradually increase without losing energy. This will reduce the Most of the main steam flow 15 that has passed through the turbine stage is discharged through the exhaust pipe 29 and guided to the reheater of the boiler 1, but some steam flow is branched and passes through the internal case and sink 33. It becomes cooling steam 32 to be cooled and is discharged from the cooling steam exhaust pipe 31. However, although this cooling steam 32 reduces its pressure and temperature as it passes through the turbine stage, it is still relatively high temperature.
There is a possibility that the heat-resistant protection of the external casing 30 etc. will not be sufficient. In particular, the heat resistance of the outer casing 30 is important because ultra-high temperature steam flows inside the main steam pipe 26 and high-temperature heat is transferred to the outer casing 30 by heat conduction. However, if the outer casing 30 is made of a material with high heat resistance, the cost will increase significantly, so it is desirable to use a conventional material with relatively low heat resistance as the material for the outer casing 30. FIG. 7 shows a specific example of a cooling method for the outer casing 30 for this purpose. That is, the low-temperature steam 23 generated in the portex tube 22 shown in FIG. This is a method of cooling the outer casing 30 by forming a heat shielding layer. FIG. 8 shows a detailed configuration of this cooling channel 35.

In this figure, the low temperature steam 23 and inlet vibrator 37 shown in Figure 2 are shown.
In addition, a partition wall 36 is provided on the inner wall side of the outer casing 30 so as to communicate the high temperature steam 24 and the outlet vibe 38 and isolate it from the internal fluid of the outer casing 30, thereby forming a cooling flow path 35 and a cooling passage 35 between the high temperature steam 24 and the outlet vibe 38. The outlet vibe 39 is communicated with the main steam pipe 26 and the outer casing 30 to form a cooling passage 41 via a heat shield plate 40 . By adopting such a cooling method, the inner wall surface of the outer casing 30, the joint between the main steam pipe 26 and the outer casing 30, etc. are cooled, and it is possible to use a material with relatively low heat resistance as the outer casing material. becomes.

On the other hand, FIG. 9 shows an embodiment of a method of cooling the joint between the main steam pipe 26 and the outer casing 30 without providing a heat insulating layer as shown in FIG.

In this figure, the cooling steam 21 is introduced into the portex tube 22 through the inlet control valve 43, the flow rate of the separated high temperature steam 25 is controlled by the outlet control valve 44, and the low temperature steam 23 is introduced into the inlet vibrator 42 and the high temperature steam 24. The outlet vibe 39 is communicated with the main steam pipe 26 and the outer casing 30, and a cooling flow path 41 is formed between the main steam pipe 26 and the external casing 30 via a heat shield plate 40. The inlet control valve 43 and the outlet control valve 44 are controlled by a controller 45 to sense the temperature of the main steam and perform optimal cooling. As shown in FIG. 10, the characteristics of the portex tube 22 are that when high-pressure steam is supplied, high-temperature steam H and low-temperature steam are obtained by separating them. The above control can be easily achieved since the temperature of H can be changed and the temperature level of the entire tank can also be changed by means of the inlet control valve 43 which controls the high pressure steam supply.

By employing such a cooling method, it is possible to effectively cool the joint between the main steam pipe 26 and the outer casing 30, which are at the highest temperature. Note that the inlet control valve 43 and the outlet control valve 4
Although the control mechanism constituted by 4 and the controller 45 is not shown in the figure, it can be similarly applied to the embodiment shown in FIG.

Further, in this example, the portex tube 22 is placed outside the ultra-high pressure turbine 2, but it can also be placed between the outer casing 30 and the inner casing 33.

If the ultra-high-temperature, high-pressure steam turbine cooling technology according to the embodiments of the present invention described above is adopted, the internal structure of the ultra-high-pressure turbine can be used as a relatively low-grade structure excluding the parts that come into direct contact with ultra-high-temperature steam. Even if heat-resistant steel is used, a steam turbine plant with sufficient strength and reliability can be provided. Moreover, with the cooling technology of the present invention, when the main steam conditions change such as during partial load or variable pressure operation, the structure can be cooled by sensing the temperature of the main steam and controlling the portex tube inlet and outlet control valves. The conditions can be optimized, and the reliability of the steam turbine can be significantly improved because it is not affected by turbine flow as in the case of using a portion of the conventional final stage evaporation.

Additionally, Portex tubes have a simple structure and no moving parts, making them highly reliable and inexpensive. Furthermore, the high-temperature steam separated by the portex tube is sent to the exhaust system or water supply system of the ultra-high pressure turbine, and the low-temperature steam heated by cooling the internal components is sent to the exhaust system of the cylinder pressure turbine.
Since the steam is returned and used for complete heating, deterioration in plant efficiency is minimized. Since these steam systems are located around high-pressure turbines, the piping system can be short, and additional power such as bongos for cooling internal structures is not required, making them extremely economical and practical. expensive.

In addition, since the low-temperature steam separated by the vortex valve is completely in the gas phase, there is no local rapid cooling caused by water droplets compared to low-temperature steam obtained by mixing cooling water.
There is no need to worry about cracks caused by thermal stress.

〔Effect of the invention〕

According to the present invention, it is possible to obtain the optimum cooling steam for the steam turbine, thereby preventing the generation of excessive thermal stress, and furthermore, by recovering the heat contained in the steam used for cooling, it is possible to prevent a decrease in plant efficiency. The effect is obtained.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional ultra-high-temperature, high-pressure steam turbine plant, FIG. 2 is a system diagram of an ultra-high-temperature, high-pressure steam turbine plant that is an embodiment of the present invention, and FIGS. A system diagram of an ultra-high-temperature, high-pressure steam turbine plant that is another embodiment of the system, Fig. 7 is a sectional view showing the internal cooling structure of the ultra-high pressure turbine 2 in Fig. 2, and Fig. 8 is a partially enlarged view of Fig. 7. 9 is a sectional view showing another embodiment of FIG. 8, and FIG.
The figure shows the characteristics of the portex tube.

Claims (1)

[Claims] 1. A boiler, a steam turbine driven by steam generated from the boiler, a condenser for condensing the steam that has passed through the steam turbine, and a condenser for collecting condensate from the condenser. In a steam turbine plant equipped with a water supply system that supplies water to a boiler, a part of the steam generated in the boiler and driving the steam turbine is introduced into a portex tube device and separated into high-temperature steam and low-temperature steam. A steam turbine plant characterized in that the low-temperature steam is guided to a portion of the steam turbine that requires cooling, and the cylinder-temperature steam is used as driving steam for the steam turbine. 2. In claim 1, the low-temperature steam after cooling the parts of the steam turbine that require cooling is used as driving steam for a turbine with a low driving steam pressure among a plurality of turbines constituting the steam turbine. A steam turbine plant characterized by: 3. The steam turbine according to claim 1, further comprising a control device that adjusts the steam conditions of the low-temperature steam that is guided to a cooling-required location of the steam turbine in accordance with the state of the steam turbine. plant. 4. In claim 1, a partition wall is provided on the inner wall side of the outer casing of the steam turbine to form a space between the casing and the partition wall, and the low-temperature steam from the portex tube device is A steam turbine plant characterized by being introduced into this space. 5. A steam turbine plant according to claim 1, wherein the steam introduced into the portex tube device is steam branched from a steam system extending from the boiler to the steam turbine. 6. A steam turbine plant according to claim 1, wherein the steam introduced into the portex tube device is a part of driving steam that has flowed into the steam turbine. 7. In claim 4, the low-temperature steam introduced into the space flows down from an outer casing portion in the vicinity to which the main steam pipe is connected, and the steam turbine comprises one of the plurality of turbines constituting the steam turbine. A steam turbine plant characterized in that it is installed in a turbine with low driving steam pressure. An 8° boiler, a steam turbine driven by the steam generated from the boiler, a condenser that condenses the steam that has passed through the steam turbine, and a condenser that supplies condensed water to the boiler from the condenser. In a steam turbine plant equipped with a water supply system equipped with a heating device for heating feed water, a part of the steam generated in the boiler to drive the steam turbine is introduced into a portex tube device to generate high-temperature steam and low-temperature steam. A steam turbine plant characterized in that the low-temperature steam is guided to a part of the steam turbine that requires cooling, and the high-temperature steam is guided to a heating device for heating feed water of a water supply system for heat recovery. . 9. In claim 8, the low-temperature steam after cooling the parts of the steam turbine that require cooling is used as a heat source for a heating device with low steam pressure among a plurality of heating devices provided in the water supply system. A steam turbine plant characterized by guiding. 10. Claim 8 is characterized in that a control device is provided that adjusts the steam conditions of the low-temperature steam guided to a portion of the steam turbine that requires cooling, depending on the state of the steam turbine. steam turbine plant. 11. In claim 8, a partition wall is provided on the inner wall side of the outer casing of the steam turbine to form a space between the casing and the partition wall, and the low-temperature steam from the portex tube device is A steam turbine plant characterized by being introduced into this space. 12. A steam turbine plant according to claim 8, wherein the steam introduced into the vortex stoop device is steam branched from a steam system extending from the boiler to the steam turbine. . 13. The steam turbine plant according to claim 8, wherein the steam introduced into the portex tube device is part of the driving steam that has flowed into the steam turbine. 14. In claim 11, the low-temperature steam introduced into the space flows down from the outer casing portion in the vicinity to which the main steam pipe is connected, and flows into one of the plurality of heating devices constituting the heating device. , a steam turbine plant characterized in that it is adapted to be introduced into a heating device with low steam pressure.