JP2558740B2 - How to start up a two-stage reheat steam turbine plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a method for starting a two-stage reheat steam turbine plant in combination with a boiler having a two-stage reheater.

(Prior Art) In recent years, efforts to improve the performance of steam turbine plants have resulted in the efforts of the parties concerned to develop ultra-high pressure and high-pressure turbines, and some units are soon to realize this. The steam condition at the turbine inlet of this newly developed ultra-high pressure high temperature turbine is the same as the conventional pressure / temperature 246 kg / cm ² g / 5
It is 316 kg / cm ² g / 566 ° C against 38 ° C. On the other hand, when we turn our eyes around the world, we have improved this steam condition to 316 kg / cm.
Development of ultra high-pressure high-temperature turbines of ² g / 593 ° C and 352 kg / cm ² g / 593 ° C class is also in progress. These ultra high pressure and high temperature turbines are basically constructed as a two-stage reheat type steam turbine plant in combination with a boiler having a two-stage reheater. Hereinafter, a typical one will be described with reference to the drawings.

That is, in FIG. 2, the main steam generated in the boiler 1 is guided to the ultra-high pressure turbine 3 through the main steam pipe 2, expands and performs work inside the main steam pipe 3, and is exhausted as a first-stage low-temperature reheat steam pipe. It is sent to the first stage reheater 5 via 4. This ultra-high pressure turbine exhaust gas is reheated in the first-stage reheater 5, becomes high-temperature reheated steam, and is introduced into the high-pressure turbine 7 through the first-stage high-temperature reheat steam pipe 6, where it expands to perform work. The exhaust gas is sent to the second stage reheater 9 through the second stage low temperature reheat steam pipe 8 as exhaust gas. This high-pressure turbine exhaust gas is heated in the second-stage reheater 9 and becomes high-temperature reheated steam through the second-stage high-temperature reheated steam 10 to the intermediate-pressure turbine.
It is guided to 11, is expanded and performs work inside, and is sent to the low pressure turbine 13 via the low temperature steam pipe 12 as exhaust gas.
This medium-pressure turbine exhaust expands and performs work in the low-pressure turbine 13 as well, and is then discharged to the condenser 14 and exchanges heat with cooling water sent by a circulating water pump (not shown) to become condensed water. This condensate is extracted by a condensate pump 15, heated through a low-pressure feed water heater 16 and a deaerator 17, further pressurized by a feed water pump 18, returned to the boiler 1 through a high-pressure feed water heater 19, The cycle is complete. In the figure, reference numeral 20 indicates a main steam stop valve, 21a and 21b indicate reheat steam stop valves, and reference numerals 22 and 23a and 23b indicate a main steam control valve and a reheat steam control valve, which are super high pressure. Turbine 3 or high pressure turbine 7, medium pressure turbine 11 and low pressure turbine
The output of each is controlled by adjusting the flow rate of the main steam or reheated steam flowing in 13.

By the way, in such a two-stage reheat type steam turbine plant, the mismatch between the boiler load and the turbine load at the time of starting and stopping the turbine is alleviated, and the cooling steam is supplied to each reheater 5 and 9. A turbine bypass system is provided for this purpose. That is, an ultra-high pressure turbine bypass pipe 25 having an ultra-high pressure turbine bypass valve 24 that connects the main steam pipe 2 and the first-stage low temperature reheat steam pipe 4 to the ultra-high pressure turbine 3 is provided. A high-pressure turbine bypass pipe 27 having a high-pressure turbine bypass valve 26 that connects the first-stage high-temperature reheat steam pipe 6 and the second-stage low-temperature reheat steam pipe 8 is provided respectively, and the high-pressure turbine bypass pipe 27 is provided in the first-stage reheater 5 at the time of startup. On the other hand, the steam whose temperature has been adjusted by the desuperheater 28 is fed to the second stage reheater 9 again.
The steam whose temperature is adjusted by the desuperheater 29 is supplied to each of the above. Further, in order to discharge the cooling steam at the time of start-up and further to let the main steam or the like escape directly to the condenser 14 without passing through the intermediate-pressure turbine 11 and the low-pressure turbine 13 when the plant load is cut off, etc. A middle low-pressure turbine bypass pipe 31 is provided while connecting the stage high-temperature reheat steam pipe 10 and the condenser 14 with a low-pressure turbine bypass valve 30. In the figure, reference numeral 32 is a desuperheater,
It is provided to cool the steam discharged to 14 to an appropriate temperature. Further, reference numerals 33 and 34 denote check valves, and reference numeral 35 denotes a generator.

(Problems to be Solved by the Invention) Although the two-stage reheat type steam turbine plant is the most typical one of the ultra-high pressure high temperature turbine due to the above configuration, when the turbine inlet steam condition changes to a higher pressure, the ultra high pressure It is necessary to consider the increase in the exhaust pressure of the turbine 3. The rise in exhaust pressure in the ultra-high pressure turbine 3 is caused by the main pressure of the ultra-high pressure turbine 3 being increased when the rotational speed is increased by opening the reheat steam control valve 23a of the high-pressure turbine 7 other than the ultra-high pressure turbine 3, for example. This occurs because the main steam leaks from the seat surface of the steam control valve 22 and the main steam flows inside the ultra-high pressure turbine 3 and stays there. When the main steam pressure in the above-mentioned example is 352 kg / cm ² g class, this exhaust pressure is about twice as high as the conventional level. Under such exhaust pressure, the friction between the impeller of the ultra-high pressure turbine 3 rotated at high speed and the residual steam becomes intense, causing heat generation due to so-called wind loss that causes the metal temperature to rise significantly. In the part where the peripheral speed is fast, there is great concern about the material strength.

One measure to deal with the heat generation due to the windage loss is to introduce cooling steam to the ultra-high pressure turbine 3. That is, it is conceivable to open the main steam control valve 22 from the initial stage of introduction to introduce the main steam into the ultra-high pressure turbine 3 and employ a starting method in which the impeller or the like is cooled by the cooling steam.

However, in this way of starting up,
For example, because of the matching of the introduced steam with the metal temperature, all of the ultra-high pressure turbine 3, the high-pressure turbine 7, the intermediate-pressure turbine 11 and the low-pressure turbine 13 cannot be excluded from monitoring, and the amount of steam is monitored while simultaneously monitoring the metal temperature and the like. There is a problem in that it is difficult to avoid deterioration of controllability due to extremely complicated operations such as adjustment.

Therefore, an object of the present invention is to improve the controllability by reducing the number of turbines to be monitored at the same time as starting the turbine, and also to suppress the exhaust pressure of the ultra-high pressure turbine from rising. It is to provide a method for starting a thermal steam turbine plant.

[Structure of Invention]

(Means for Solving Problems) In order to solve the above problems, a starting method according to the present invention is a turbine system including an ultrahigh pressure turbine, a high pressure turbine, an intermediate pressure turbine and a low pressure turbine, and a first stage reheater. A reheat system including a second-stage reheater, a turbine bypass system including an ultra-high pressure turbine bypass system, a high-pressure turbine bypass system, and a medium- and low-pressure turbine bypass system, and a first for an ultra-high-pressure turbine used for output control. In the method for starting a two-stage reheat type steam turbine plant having a control valve of No. 1, a second control valve for high-pressure turbines, and a third control valve for medium- and low-pressure turbines, the rotation speed is constant with respect to a constant speed from a turbulent stop state. Controlling only the third control valve while closing the first and second control valves to direct a portion of the reheated steam sent from the second stage reheater to the medium and low pressure turbines, and The rest The reheated steam is processed by the middle and low pressure turbine bypass systems, in which case the internal pressures of the ultra high pressure and high pressure turbines are both maintained at approximately vacuum, and then part of the main steam is fed to the ultra high pressure turbine. The first control valve and the second control valve are controlled so as to supply a part of the reheated steam from the first stage reheater to the high pressure turbine, and the remaining main steam and reheated steam are the turbine. By processing in a bypass system, it is necessary to maintain the exhaust pressure of the ultra-high pressure turbine and the exhaust pressure of the high pressure turbine in equilibrium with the pressure of the first stage reheater and the pressure of the second stage reheater, respectively. Characterize.

(Operation) Turbine start-up operation uses the turbine bypass system to obtain the state of steam required for start-up, and after this preparation, steam is actually guided to each turbine to gradually rotate the impeller. It is roughly divided into the starting process of raising.

The feature of the present invention resides in the operating procedure of each control valve of the turbine system and each control valve of the turbine bypass system in this starting process, and the process proceeds as follows.

That is, the operation is initially performed by a third, middle and low pressure turbine
The control valve is opened so that a part of the reheated steam is guided to the medium pressure turbine and is rotated until a constant speed is reached. At this time, the turbine bypass system closes the control valve by the amount of steam consumed in the turbine system. In that case, the main purpose of the present invention is to maintain the internal pressures of the ultra-high pressure and high-pressure turbines in a vacuum, which causes neither the ultra-high pressure nor the high-pressure turbine to cause windage loss, and to prevent the heating phenomenon of their exhausts. Suppressed. It also helps improve controllability due to the reduced number of turbines monitored at the same time.

Next, operation opens the first control valve for the ultra high pressure turbine and the second control valve for the high pressure turbine. For this reason, the main steam or reheated steam flows into each turbine to start up while increasing the load together with ventilation. In that case, the exhaust pressure of the ultra-high pressure turbine is normally balanced with the pressure of the first stage reheater, and the exhaust pressure of the high pressure turbine is balanced with the pressure of the second stage reheater.

(Embodiment) FIG. 1 shows an apparatus according to a first embodiment of the present invention. Here, the same components as those shown in FIG. 2 in FIG. 1 are designated by the same reference numerals, and a description thereof will be omitted.

In FIG. 1, the other end of the ultra-high pressure turbine exhaust pipe 41 branched from the first-stage low temperature reheat steam pipe 4 communicating with the exhaust side of the ultra-high pressure turbine 3 is recovered via an ultra-high pressure turbine exhaust valve 42. The other end of the high-pressure turbine exhaust pipe 43 branched from the second-stage low temperature reheat steam pipe 8 communicating with the water tank 14 and the exhaust side of the high-pressure turbine 7 has a condenser via a high-pressure turbine exhaust valve 44. 14 connected to each.

The start-up operation by the above-mentioned device proceeds in the following procedure.

(I) Startup preparation process The degree of vacuum of the condenser 14 is increased in preparation for the turbine startup,
The super high pressure turbine bypass valve 25, the high pressure turbine bypass valve 26 and the medium and low pressure turbine bypass valve 30 are opened when a certain level, for example, 600 mmHg or more is reached. At the same time, the ultrahigh pressure turbine exhaust valve 42 and the high pressure turbine exhaust valve 44 are also fully opened. Then, the steam generated in the boiler 1 flows from the main steam pipe 2 to the ultra-high pressure turbine bypass pipe 25,
After being cooled by the desuperheater 28, it is led to the first stage reheater 5 through the first stage low temperature reheat steam pipe 4. At this time, the check valve 33 works so as to prevent the main steam flowing from the desuperheater 28 to the first-stage reheat steam pipe 4 from flowing to the ultra-high pressure turbine 3 and the condenser 14. After this, the main steam recovers its temperature while passing through the first-stage reheater 5, flows through the first-stage high-temperature reheat steam pipe 6 to the high-pressure turbine bypass pipe 27, and is cooled by the desuperheater 29. It is guided to the second stage reheater 9 through the second stage low temperature reheat steam pipe 8. Also here, the check valve 34 prevents the reheated steam flowing into the second stage low temperature reheat steam pipe 8 from flowing into the high temperature turbine 7 and the condenser 14. The main steam that has flowed to the second-stage reheater 9 is heated while passing through it, recovers the temperature, and flows through the second-stage high-temperature reheat steam pipe 10 to the middle and low pressure turbine bypass pipes 31 to reduce the temperature. After being cooled by 30, the entire amount is discharged to the condenser 14.

During this time, the main steam stop valve 20 and the reheat steam stop valves 21a, 21
b is fully opened and preheated by main steam or reheated steam. Further, since the ultra-high pressure turbine exhaust valve 42 and the high-pressure turbine exhaust valve 44 are fully opened, the internal pressure of the ultra-high pressure turbine 3 and the high-pressure turbine 7 becomes a pressure in equilibrium with the internal pressure of the condenser 14, that is, almost vacuum. It is kept close. Needless to say, the opening operation of the main steam control valve 22 and the reheat steam control valves 23a and 23b is not performed during this start-up preparation.

(II) Startup Process In the startup operation, the reheat steam control valve 23b is first slightly opened. Then, a part of the reheated steam flowing through the second-stage high-temperature reheated steam pipe 10 passes through the reheated steam control valve 23b and the intermediate pressure turbine 1
Flow to 1 and turn the impeller. After that, reheat steam control valve 2
As the opening degree of 3b is opened, the rotation speed of the intermediate pressure turbine 11 increases and reaches a constant speed. At the same time, the low-pressure turbine 13 is also rotated by the exhaust of the medium-pressure turbine 11 and reaches a constant speed. At this time, the openings of the middle and low pressure turbine bypass valves 30 are closed by an amount commensurate with the flow rate of the reheated steam introduced into the intermediate pressure turbine 11.

On the other hand, the metal temperature of the medium-pressure turbine 11 and the low-pressure turbine 13 and the difference in expansion are accurately grasped during the speed-up process of the medium-pressure turbine 11, etc., and adjusted so as not to hinder the operation together with other monitoring items. It The super-high pressure turbine 3 which is the most difficult object to monitor is excluded, and the number of turbines is small, so that it can be handled relatively easily.

Further, in the process of increasing the speed of the intermediate pressure turbine 11 and the like, the impellers of the ultrahigh pressure turbine 3 and the high pressure turbine 7 are rotated at the same speed as the rotation speed of the intermediate pressure turbine 11. However, at this time, the insides of the ultra-high pressure turbine 3 and the high-pressure turbine 7 are in a state close to a vacuum, and even if there is no flow of the main steam or the reheated steam that works as the cooling steam, the windage loss does not occur, so that the blades are not blown. The car does not generate heat.

Next, in the starting operation, the main steam control valve 22 and the reheat steam control valve 23a are slightly opened, and at the same time, the ultrahigh pressure turbine exhaust valve 42 and the high pressure turbine exhaust valve 44 are fully closed. Then, a part of the main steam from the boiler 1 flows from the main steam pipe 2 to the ultra-high pressure turbine 3 and rotates its impeller. After that, as the opening degree of the main steam control valve 22 is opened to match the load, the amount of main steam flowing into the ultra-high pressure turbine 3 increases and the exhaust pressure increases, and the closed check valve 33 is fully opened. . For this reason,
The main steam that has expanded in the ultra-high pressure turbine 3 is discharged to the first stage low temperature reheat steam pipe 5, and the ultra high pressure turbine bypass pipe 24
Flow into the first-stage reheater 5 together with the main steam flowing therethrough, and after recovering the temperature there, a part of it passes through the first-stage high-temperature reheat steam pipe 6 to the high-pressure turbine 7 through the reheat steam control valve 23a. Introduced to rotate the impeller, the rest is the high pressure turbine bypass pipe
Head to 27.

Then, as the reheat steam control valve 23a is opened, the amount of reheat steam flowing into the high pressure turbine 7 increases, and the exhaust pressure thereof increases. Therefore, the closed check valve 34 is fully opened, the reheated steam is discharged to the second stage low temperature reheated steam 8, and the second stage reheater 9 is discharged together with the reheated steam flowing through the high pressure turbine bypass pipe 27. Flow into. Then, while passing through it, the temperature is recovered and a part is introduced into the intermediate pressure turbine 11 through the second-stage high temperature reheat steam pipe 10 through the reheat steam control valve 23b to rotate the impeller, and the rest is It is discharged to the condenser 14 through the middle and low pressure turbine bypass pipe 31.

On the other hand, starting from the ventilation of the ultra-high pressure turbine 3 and the high-pressure turbine 7, the metal temperature, the difference in expansion, etc. of each are accurately grasped at the time of start-up, and adjustment is made so as not to hinder the operation together with other monitoring items. .

At this time, the number of turbines to be monitored is only two, and even if these are required to be strictly monitored due to the temperature condition, it is possible to focus attention on them and to deal with them safely. is there.

After this, the starting operation is the main steam control valve 22 and the reheat steam valve.
23a, 23b are each opened to a predetermined opening degree, and at the same time, the super high pressure turbine bypass valve 24 and the high pressure turbine bypass valve 26,
The middle and low pressure turbine bypass valves 30 are closed.
As a result, the total amount of main steam flowing from the boiler 1 through the main steam pipe 2 is directed to the ultra-high pressure turbine 3, and the steam flow control thereafter is entirely entrusted to the main steam control valve 22.

〔The invention's effect〕

As described above, according to the start-up method of the two-stage reheat steam turbine plant according to the present invention, the number of turbines to be monitored is small at the same time, for example, matching the introduced steam and the metal temperature, or the stationary part. Since it is easy to adjust the amount of steam that keeps the expansion difference between the rotating part and the rotating part within an appropriate range, the controllability of the two-stage reheat steam turbine plant can be improved. Moreover, since the internal pressure of the ultra-high pressure turbine is placed under favorable conditions of vacuum and heat generation due to windage loss is suppressed, it is possible to obtain a useful effect that the degree of overheating of exhaust gas is small.

[Brief description of drawings]

FIG. 1 is a system diagram of a two-stage reheat type steam turbine plant including an apparatus applied to the method of the present invention, and FIG. 2 is a system diagram showing a conventional two-stage reheat type steam turbine plant. 1 ... Boiler, 3 ... Super high pressure turbine 5 ... First stage reheater, 7 ... High pressure turbine 9 ... Second stage reheater, 11 ... Medium pressure turbine 13 ... Low pressure turbine, 22 ... Main steam control valve 23a, 23b Reheat steam control valve 24 Super high pressure turbine bypass valve 26 High pressure turbine bypass valve 30 Medium / low pressure turbine bypass valve 33, 34 Check valve 41 … Ultra high pressure turbine exhaust pipe 42 …… Ultra high pressure turbine exhaust valve 43 …… High pressure turbine exhaust pipe 44 …… High pressure turbine exhaust valve

Continuation of the front page (72) Inventor Ichiro Kajitani 3-2-16 Toyosu, Koto-ku, Tokyo Ishikawa Shima Harima Heavy Industries Co., Ltd. Toyosu General Office (56) Reference JP-A-60-159311 (JP, A) JP Sho 53-102401 (JP, A)

Claims (1)

(57) [Claims] 1. A turbine system including an ultra-high pressure turbine, a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine, a reheat system including a first-stage reheater and a second-stage reheater, and an ultra-high-pressure turbine bypass system. Turbine bypass system consisting of high-pressure turbine bypass system and middle and low-pressure turbine bypass system, first control valve for ultra-high-pressure turbine used for output control, second control valve for high-pressure turbine, middle- and low-pressure turbine In the method for starting a two-stage reheat steam turbine plant having a third control valve, the second-stage reheater is fed to the intermediate-pressure and low-pressure turbines from a turbine stopped state until the rotation speed reaches a constant speed. Only the third control valve is controlled while the first and second control valves are closed so as to guide a part of the reheated steam, and the remaining reheated steam is supplied to the middle and low pressure turbine bypass systems. Where In that case, the internal pressures of the ultra-high pressure and high-pressure turbines are both maintained at approximately vacuum, and then a portion of the main steam is re-heated to the ultra-high-pressure turbine and re-heated from the first-stage reheater to the high-pressure turbine. The first control valve and the second control valve are controlled so as to supply a part of the hot steam, respectively, and the remaining main steam and reheated steam are processed in the turbine bypass system, and in that case, A two-stage reheat system in which the exhaust pressure of the high-pressure turbine and the exhaust pressure of the high-pressure turbine are held in equilibrium with the pressure of the first-stage reheater and the pressure of the second-stage reheater, respectively. How to start a steam turbine plant.