JPH01273805A - Two stage reheating steam turbine plant having turbine bypass device - Google Patents

Abstract

PURPOSE:To increase the warming performance at actuation time by providing the bypass pipe going round the respective turbine of ultrahigh pressure, high pressure, medium and low pressures and providing the steam liaison pipe leading steam to a low pressure turbine directly without flowing it to an ultrahigh pressure turbine. CONSTITUTION:The title plant performs work with the steam generated by a boiler 1 being passed in order through an ultrahigh pressure turbine 23, a 1st stage reheater 30, high pressure turbine 2, 2nd stage reheater 37 and medium, low pressure turbines 10, 11, driving a generator 22. In this case, the bypass pipe 26 reaching to a 1st stage reheater 30 by going round the ultrahigh pressure turbine 23, the bypass pipe 33 reaching to a 2nd stage reheater 37 by going round the high pressure turbine 2 and the bypass pipe 14 reaching to a steam condenser 12 by going round the medium, low pressure turbines 10, 11 are respectively provided. An ultrahigh pressure steam liaison pipe 45 is provided so that steam may be flowed into the low pressure turbine directly without being flowed into the ultrahigh pressure turbine 23 and a main steam control valve 46 is interposed on the way.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION Field of Industrial Application The present invention relates to a two-stage reheat steam turbine plant with a turbine bypass device.

(Prior Art) A turbine bypass system is installed for the purpose of increasing the flexibility of plant operation by eliminating or relaxing mutual control between a boiler and a steam turbine, and has a primary function. One is to improve the startup characteristics. By cooling the reheater with steam at startup, it prevents burnout of the reheater, increases the boiler combustion rate, and facilitates metal matching when venting the steam turbine. It can be done. The next function is to absorb the difference between the boiler load and the turbine load, and to respond to sudden load changes that exceed the boiler's load response and absorb the response delay at that time. It also has the function of discharging excess steam when transitioning to Furthermore, it functions as a superheater safety valve and a reheater safety valve, and can suppress pressure rises, especially when combined with a variable pressure operation plant.

As shown in FIG. 2, a conventional turbine bypass system is a high-pressure turbine bypass device that includes a main steam pipe 3 for passing steam generated from a boiler 1 bypassing a high-pressure turbine 2.
and a high-pressure turbine bypass pipe 5 connecting the low-temperature reheat steam pipe 4, a bypass control valve 6 for controlling the steam flow rate of the high-pressure turbine bypass pipe 5, and a reduction valve for controlling the outlet temperature of the bypass control valve 6. A high-pressure turbine check valve 8 is installed in the low-temperature reheater 4.

Also, as a low-pressure turbine bypass device, a high-temperature reheat steam pipe 13 and a condenser 12 are used to dump the steam that has passed through the reheater 9 of the boiler to the condenser 12 by bypassing the intermediate-pressure turbine 10 and the low-pressure turbine 11. A bypass control valve 15 for controlling the steam flow rate of the medium and low pressure turbine bypass pipe 14 and a desuperheater 16 for controlling the outlet temperature of the bypass control valve 15. It is made up of.

The water condensed in the condenser 12 is sent to the boiler through a condensate pump 17, a low pressure heater 8, a deaerator 19, a feed water pump 20, and a high pressure heater 21, and is then sent to the boiler again.
It is circulated through an intermediate pressure turbine 10 and a low pressure turbine 11. The generator 22 is driven by the high pressure turbine 2, the intermediate pressure turbine 10, and the low pressure turbine 11.

In a steam turbine plant having this conventional turbine bypass system, there is a case where the intermediate pressure and low pressure turbines 10° and 11 are used to start up and speed up, and further control low loads, and a case where the high pressure turbine 2
Or high pressure, intermediate pressure, low pressure turbine 2, 1.0.11
There are cases in which the motors are simultaneously started, speeded up, and further controlled at low loads.

In either case, during start-up, especially during a cold start or warm start, the steam in the turbine rotor
There is a problem that metal matching becomes a harsh environment (mismatch becomes large), and control at startup is complicated because high pressure, intermediate pressure, and low pressure turbines 2, 10 and 11 must be taken into consideration at the same time.

On the other hand, when this conventional turbine bypass system is applied to a two-stage reheat steam turbine in combination with a boiler having two stages of reheaters, the situation becomes even more complicated.

When the above-described conventional turbine bypass system is applied to a two-stage reheat steam turbine combined with a boiler having two-stage reheaters, the result is as shown in FIG. 3. As an ultra-high-pressure turbine bypass device, an ultra-high-pressure turbine connects an ultra-high-pressure main steam pipe 24 and a first low-temperature reheat steam pipe 25 for flowing ultra-high-pressure, high-temperature main steam generated from the boiler 1 bypassing the ultra-high-pressure turbine 23. The first low-temperature regeneration system is composed of a turbine bypass pipe 26, a bypass control valve 27 for controlling the steam flow rate of the ultra-high pressure turbine bypass pipe 26, and a desuperheater 28 for controlling the outlet temperature of the bypass control valve 27. An ultra-high pressure turbine exhaust check valve 29 is installed in the heat steam pipe 25 . Also, as a high-pressure turbine bypass device, a first high-temperature reheat steam pipe 31 and a second low-temperature reheat pipe 32 are used to flow the steam that has passed through the first stage reheater 30 of the boiler 1 while bypassing the high-pressure turbine 2.
a high-pressure turbine bypass pipe 33 connecting the high-pressure turbine bypass pipe 33, a bypass well control 34 for controlling the steam flow rate of the high-pressure turbine bypass pipe 33, and a desuperheater 35 for controlling the outlet temperature of the bypass entry control valve 34. A high-pressure turbine exhaust check valve 36 is installed in the second low-temperature reheat steam pipe 32. Further, as a low-pressure turbine bypass device, a second high-temperature reheat steam pipe 38 is used to dump the steam that has passed through the second stage reheater 37 of the boiler 1 to the condenser 12, bypassing the intermediate-pressure turbine 10 and the low-pressure turbine 11. A low pressure turbine bypass pipe 14 , a bypass control valve 15 for controlling the steam flow rate of the medium and low pressure turbine bypass pipe 14 , and a reduction valve for controlling the outlet temperature of the bypass control valve 15 are connected to the condenser 12 and the low pressure turbine bypass pipe 14 . It is composed of a warmer 16.

The water condensed in the condenser 12 is sent to the boiler 1 through a condensate pump 17, a low pressure heater 18, a deaerator 19, a feed water pump 20, and a high pressure heater 21, and is then sent to the ultra-high pressure turbine 2 again.
3. The generator 22 circulating through the high pressure turbine 2, the intermediate pressure turbine 10 and the low pressure turbine 11 is driven by the extra high pressure turbine 23, the high pressure turbine 2, the intermediate pressure turbine 10 and the low pressure turbine 11.

(Problem to be solved by the invention) By the way, as an important development model for improving the performance of steam turbine plants due to the shortage of fossil fuels, the development of ultra-high pressure and high temperature turbines with higher main steam pressure and temperature than conventional models is progressing. . In Japan, the conventional main steam inlet condition is 246 kg.
f/a#, 316kgf/d over 538℃, 5
The development of a 66℃ ultra-high pressure and high temperature turbine has been completed and construction is already underway, with a worldwide production capacity of 316kgf/a+f,
593℃ class or 350kgf/a+! , 538
℃ class turbine development is underway. These ultra-high pressure, high temperature turbines are essentially two-stage reheat steam turbine plants with two-stage reheaters. In the case of this two-stage reheat type ultra-high-pressure, high-temperature turbine, the turbine control at startup is more complicated than that of the single-stage reheat turbine described above, and there is also a turbine bypass system to prevent steam-metal mismatching at startup. As a result, the boiler load increase rate (steam temperature increase rate) increases, and each turbine rotor of an ultra-high-pressure, high-temperature turbine is strongly affected by mismatching. Furthermore, in the case of ultra-high-pressure, high-temperature turbines, martensitic stainless steel or austenitic stainless steel is used as part material for the steam turbine, so a stricter design than before is required to account for the difference in elongation of the turbine.

In this respect as well, it is extremely difficult to apply the conventional turbine bypass system as it is.

The object of the present invention is to provide a two-stage recycler equipped with a turbine bypass device that can simplify startup operations by reducing the effects of thermal stress caused by mismatching of ultra-high pressure turbine rotors, high-pressure turbine rotors, etc. at the time of turbine startup. The purpose of the present invention is to provide a thermal steam turbine plant.

[Structure of the invention]

(Means for Solving the Problems) In a two-stage reheat steam turbine plant having a turbine bypass device according to the present invention, steam generated in a boiler having a two-stage reheater passes through an ultra-high pressure main steam pipe to an ultra-high pressure It is guided to the turbine, from this ultra-high pressure turbine it is sent to the first stage reheater of the boiler where it is heated, then it is led through the first high temperature reheat steam pipe to the high pressure turbine, and from this high pressure turbine it is sent to the second stage of the boiler. In a two-stage reheat steam turbine plant, the ultra-high pressure main steam pipe is sent to a reheater, heated, and then sequentially guided to an intermediate-pressure turbine and a low-pressure turbine via a second high-temperature reheat steam pipe. An ultra-high-pressure turbine bypass pipe equipped with a bypass control valve that branches off from the first high-temperature reheat steam pipe and bypasses the ultra-high-pressure turbine to the first stage reheater; A high-pressure turbine bypass pipe with a bypass control valve leading to the stage reheater, and a medium-low pressure pipe with a bypass valve branching from the second high-temperature reheat steam pipe and bypassing the intermediate-pressure turbine and the low-pressure turbine to the condenser. It is characterized in that a turbine bypass pipe is provided respectively, and an ultra-high pressure main steam communication pipe is provided via a main steam control valve so that the steam does not flow into the ultra-high pressure turbine but directly flows into the low pressure turbine.

(Function) As a means to reduce the thermal stress effects caused by turbine rotor mismatching during turbine startup, an ultra-high pressure main steam connecting pipe is installed to directly guide main steam from before the ultra-high pressure turbine inlet to the low-pressure turbine inlet. By starting the low-pressure turbine before venting to the high-pressure turbine, a warming effect due to wind damage is given to the ultra-high-pressure, high-pressure, and intermediate-pressure turbines, which reduces mismatching between steam and metal during actual turbine startup. At the same time, the difference in expansion of the steam turbine is also reduced.

(Example) Hereinafter, one embodiment of the present invention will be briefly described with reference to the drawings.

FIG. 1 shows a two-stage reheat steam turbine plant combined with a boiler having two reheaters and having a turbine bypass device.

Immediately before the turbine is started, the steam from the boiler 1, except for a portion, passes through the ultra-high pressure main steam pipe 24, the flow rate is controlled by the bypass control valve 27, the temperature is lowered by the desuperheater 28, and the steam is sent to the first low-temperature reheat. It passes through the steam pipe 25 and is led to the first stage reheater 30. Since the ultra-high pressure turbine exhaust check valve 29 is installed in the first low-temperature reheat steam pipe 25, the steam that has passed through the attemperator 28 does not flow back to the ultra-high pressure turbine 23. After that, the steam recovers only its temperature in the first stage reheater 30, passes through the first high temperature reheat steam pipe 31, has its flow rate controlled by the bypass control valve 34, lowers its temperature in the desuperheater 35, and then passes through the first high temperature reheat steam pipe 31. Low temperature reheat steam pipe 32
and then flows to the second stage reheater 37. Furthermore, only the temperature of the steam is recovered in the second stage reheater 37 and the steam is transferred to the second high temperature reheat steam pipe 3.
8 , the medium and low pressure turbine bypass pipe 14 , the temperature is further reduced in the attemperator 16 , and the temperature is discharged to the condenser 12 .

In this operating state of the turbine bypass system, the main steam stop valve 39, the first reheat steam stop valve 41, the second reheat steam stop valve 4
3 is warmed in the fully open state.

Further, the main steam control valve 46 provided in the ultra-high pressure main steam connecting pipe 45 that directly connects the ultra-high pressure main steam pipe 24 and the low-pressure turbine 11 is fully open, and the low-pressure turbine 11 and the boiler 1 are fully opened.
A part of the main steam from the ultra-high pressure turbine 23 degrees high pressure turbine 2 flows in and drives the low pressure turbine 11.
rotates, and each turbine rotor is warmed by windage. This warming method is an effective startup method, especially during a cold start or a warm start when there is a large temperature difference (mismatch) between the steam temperature and the rotor metal temperature. After sufficient warming, the main steam control valve 46 is closed, and then the main steam control valve 4o is opened to transfer a part of the steam that was flowing through the bypass control valve 27 to the first stage reheater 3o to the ultra-high pressure turbine 23. At the same time, the second reheat steam control valve 44 is opened, and a part of the steam that was flowing to the condenser 12 through the bypass control valve 15 is transferred to the intermediate pressure turbine 1.
0 and through the low pressure turbine 11 to ventilate and increase rotation. After this, the main steam control valve 40, the first reheat steam control valve 42, and the second reheat steam control valve 44 are opened, and at the same time, each bypass control valve 27.34.1
5 is fully closed. When the load increases further from this state, the amount of steam is increased only by the main steam control valve 40.

〔Effect of the invention〕

As described above, according to the present invention, the steam turbine can be sufficiently warmed at the time of starting the turbine, especially at the time of cold start or warm start, so that thermal stress due to mismatching of the ultra-high pressure turbine rotor, high pressure turbine rotor, etc. Since it is possible to reduce the influence of steam turbines and the difference in expansion of the steam turbine, it is possible to eliminate the complexity of startup operations, and at the same time, it has the effect of making turbine control the main element.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a two-stage reheat steam turbine plant having a turbine bypass device showing an embodiment of the present invention, FIG. 2 is a system diagram of a steam turbine plant having a conventional turbine bypass device, and FIG. 3 is a system diagram of a steam turbine plant having a conventional turbine bypass device. shows a system diagram of a steam turbine plant when a conventional turbine bypass device is applied to a two-stage reheat steam turbine plant. 1... Boiler 2... High pressure turbine 10.
...Intermediate pressure turbine 11...Low pressure turbine 12...
・Condenser 14...middle and low pressure turbine bypass pipes 15, 27.3
4...Bypass control valve 23...Ultra high pressure turbine 2
4...Ultra high pressure main steam pipe 26...Ultra high pressure turbine bypass pipe 30...First stage reheater 31...First high temperature reheat steam pipe 33...High pressure turbine bypass pipe 37...・Second stage reheat steamer 38...Second high temperature reheat steam pipe 45...Ultra high pressure main steam communication pipe 46...Main steam control valve agent Patent attorney Yudo Noriyoshi Chika Kendai Daishimaru Figure 2

Claims (1)

[Claims] Steam generated in a boiler with a two-stage reheater is led to an ultra-high-pressure turbine via an ultra-high-pressure main steam pipe, and from this ultra-high-pressure turbine is sent to the first-stage reheater of the boiler where it is heated. It is led to a high-pressure turbine through a first high-temperature reheat steam pipe, and from this high-pressure turbine it is sent to the second stage reheater of the boiler where it is heated, and further through a second high-temperature reheat steam pipe to an intermediate-pressure turbine and a low-pressure In a two-stage reheat steam turbine plant in which steam is sequentially guided to a turbine, a bypass control valve is branched from the ultra-high pressure main steam pipe, bypasses the ultra-high pressure turbine, and leads to the first stage reheater. a high-pressure turbine bypass pipe having a bypass control valve branched from the first high-temperature reheat steam pipe to bypass the high-pressure turbine and reach the second-stage reheater; Medium and low pressure turbine bypass pipes each having a bypass control valve branching from the high temperature reheat steam pipe to bypass the medium pressure turbine and the low pressure turbine and reach the condenser are provided, and steam flows into the ultra high pressure turbine. 1. A two-stage reheat steam turbine plant having a turbine bypass device, characterized in that an ultra-high-pressure main steam communication pipe is provided via a main steam control valve so that it directly flows into the low-pressure turbine without having to do so.