JPH03275904A - Starting method of steam turbine plant and condenser used therefor - Google Patents

Abstract

PURPOSE:To carry out speedy starting-up by dividing a condenser into an upper space for condensing exhaust and a lower space for storing condensed water, feeding the deaerated pure water into the lower space on start and then increasing the degree of vacuum in the upper space. CONSTITUTION:The inside of a condenser 10 is divided into an upper space A for accommodating a pipe bundle 11 and a lower space B for accommodating a hot well 12 by a partitioning member 21. For instance, when a steam turbine plant is operated after the stop for a long period, the air in the lower space B is bled by an air bleeder 16, and the heating steam is introduced, and the pure water which is previously deaerated in a pure water processing device 27 is introduced into the upper part of the hot well 12 and stored. Then, the pure water is allowed to flow in a steam condenser 14, and the flow of air into the condenser 10 from steam turbines 8a-8c is shut off, and then an air bleed valve 26 in the upper space A is opened, and the degree of vacuum is increased, and a separating valve 23 is opened to realize the communication between the upper and lower spaces A and B. Accordingly, the dissolved oxygen concentration is reduced, speedily, and starting-up is accelerated.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a steam turbine plant, and more specifically, to shortening condensate introduced into a condenser during a plant start-up operation. The present invention relates to a startup method that can degas and supply the degassed water to a boiler in a short period of time, and a condensing device used in the method.

(Conventional technology) In recent years, combined cycle power generation plants have gained recognition as a power generation method that can achieve both outstanding load followability and high thermal efficiency. Continuous efforts are being made to improve operational capabilities and equipment. The most noticeable movement in terms of operation methods is the shift from base load operation to operation that assumes daily start and stop operations, that is, operation for Daily Star Hawk Stop (hereinafter referred to as continuous use of DSS), which Improvements in equipment will also follow this trend.

An example of a conventional combined cycle power generation plant will be explained with reference to FIG. 2. Air pressurized by the compressor 1 is guided to the combustor 2, where the combustion system
It mixes with the fuel supplied from the source and becomes high-temperature combustion gas. This combustion gas is led to the gas turbine 3 as the working medium of the gas turbine system, where it expands and performs 4-J of work.
Nah). The combustion gas remains at a high temperature (approximately 550°C) after expansion, and is sent from the gas turbine 3 to the exhaust heat recovery boiler 4, where it plays the role of a heat source medium for the steam turbine system, and is then released into the atmosphere 111 as exhaust gas. Ru.

- On the other hand, if we turn our attention to the steam turbine system, the water supply pump 5
The feed water pressurized in a, 5b, and 5e is supplied to steam drums 6a, 6b, and 6C, which are maintained in different ways, respectively, via an energy saver (not shown). Steam drum 6a s 6b
The feed water extracted from s 6 c is respectively evaporator 7
a s 7 b s 7 e, and is heated by the exhaust gas of the gas turbine 3 flowing into the exhaust heat recovery boiler 4 to become steam. This steam is transferred to each steam turbine 8
a, 8b, and 8e, where it expands and performs work. The work of the steam turbines 8a, 8b, 8e and the work of the gas turbine 3 are converted into electrical output by a generator 9 directly connected to these prime movers.

The exhaust gas from the steam turbines 8a, 8b, and 8c is led to a condenser 10, where it is cooled by cooling water passing through the heat transfer tubes forming the tube bundle 1, condensed, and returned to water. This condensed water falls into the hot well 12 of the condenser [0] and is stored there as condensate.

After this, the condensate is extracted by the condensate pump 13 and passed through the gland steam condenser 14 to each feed water pump 5a, 5b,
Sent up to 5e.

Incidentally, the grand steam condenser 14 is connected to each steam turbine 8.
Steam leaking from the glands a, 8b, and 8e and flowing out is collected by a gland steam pipe 15, and is condensed through heat exchange with condensed water, thereby achieving heat recovery. Also,
An air extractor 16 is provided to extract noncondensable gases, such as oxygen, released when condensing within the condenser 10 to maintain a vacuum in the condenser 10 during plant operation. Furthermore, during plant operation, a portion of the condensate is passed through the condensate recirculation system 17 (7) and returned to the condenser 10 in order to lower the dissolved oxygen concentration in the condensate, while being heated by the exhaust gas of the steam turbine 8C. In addition, a replenishment water pipe 18 is provided for replenishing pure water to make up for the shortage when the condensate has decreased.

In addition, the code|symbol 19 has shown the condensate recirculation valve, and the code|symbol 20 has shown the pump artificial valve, respectively.

(Problem to be Solved by the Invention) By the way, while the plant is stopped, is a large amount of condensate stored in the hot well 2 of the condenser 10 in preparation for the next startup? Atmosphere enters the inside of the 0, and the condensate remains in contact with the atmosphere for a long time until it starts up. As a result, a large amount of oxygen dissolves in the condensate, and the dissolved oxygen concentration changes from 7 ppb, which is maintained during plant operation, to a very large value.

If this value becomes large, problems such as severe corrosion of the French heat tubes in the evaporators 7a, 7b, and 7C of the exhaust heat recovery boiler 4 will occur, so the dissolved oxygen concentration will be lower than the gopp level at startup.
Must be kept within b.

However, if there is nothing to prevent the atmosphere from entering the condenser 10 and dissolving a large amount of oxygen as described above, the value would be as large as 10,000 ppb. If the dissolved oxygen concentration, which has increased to 10,000 ppb, is to be lowered to 80 ppb by a degassing method using the condensate recirculation system 17, a large amount of condensate must be pumped over a long period of time to reduce the dissolved oxygen concentration to 80 ppb. As a result, the amount of time spent on deaeration increases each time DSS is operated, and it may not be possible to quickly respond to the demands of the electricity demand side.

An object of the present invention is to start up a steam turbine plant that can minimize the time required to degas the condensate stored in the hot well of the condenser to maintain the dissolved oxygen concentration required at the start of the plant. An object of the present invention is to provide a method and a condensing device for use in the method.

[Structure of the Invention] (Means for Solving the Problems) A method for starting a steam turbine plant according to the present invention includes an upper space for accommodating a tube bundle for condensing the exhaust gas of a steam turbine, and an upper space for accommodating a tube bundle for condensing the exhaust gas of a steam turbine. A lower space that accommodates a hot well that receives and stores water is airtightly divided, and a connecting pipe with an isolation valve that can be opened and closed is connected between the upper space and the lower space to collect water. It is configured as a communication passage for the hot well, and is connected above the hot well to a pure water treatment equipment equipped with a deaerator, and an air extractor is installed so that it can communicate with both the upper and lower spaces. , closing the isolation valve to cut off communication between the upper space and the lower space, supplying pre-degassed pure water from the pure water treatment device to the hot well while maintaining a vacuum in the lower space using the air extraction device; The water is then circulated through the condensate recirculation system, and then the vacuum in the headspace is increased to maintain approximately the same level as the bottom volume while the isolation valve is opened to communicate the two spaces, after which the water is removed from the hotwell. It is characterized in that it is supplied to a boiler.

In addition, in a condensing device of another invention, the inside of the condenser is divided into an upper space that accommodates a tube bundle for condensing the exhaust gas of a steam turbine, and a lower space that accommodates a hot well that receives and stores condensed water. The upper space and the lower space are divided airtightly, and a communication pipe with an isolation valve that can be opened and closed is connected between the upper space and the lower space to form a communication passage for condensate. This hot well is characterized in that it is connected to the water treatment device above the hot well, and furthermore, the air extraction device is provided so as to be able to communicate with both the upper and lower spaces.

(Operation) According to the start-up procedure of the present invention, the isolation valve is first closed to isolate the lower space of the condenser from the atmospheric environment. For this reason, while maintaining a vacuum only in the lower space using the air extraction device,
Pure water that has been degassed in advance can be supplied to the hot well from the pure water treatment device, and the dissolved oxygen concentration of the degassed condensate can be easily lowered to within goppb, which is the limit value at startup.

At the same time, the degree of vacuum in the upper space is increased by the air extraction device, and the vacuum level is matched to that of the lower space in a short period of time, allowing startup to be completed in a short period of time even after a long period of stoppage. I can do it.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 showing a condensing device used in the startup method according to the present invention. In addition,
In this figure, the same parts as those of the conventional example shown in FIG. 2 are given the same reference numerals, and the explanation thereof will be omitted.

In FIG. 1, the inside of the condenser 10 is airtightly divided into an upper space A and a lower space B by a partition member 21. A communication pipe 22 serving as the only communication passage for condensate is connected between the upper space A and the lower space B, and an isolation valve 23 that can be opened and closed is provided in this passage. Further, the tube bundle 11 and the hot well 12 are accommodated in the divided upper and lower spaces ASB, respectively. moreover,
The suction side faces each of the upper and lower spaces ASB,
- First and second air extraction pipes 24 and 25 are provided via an air extraction valve 26 so as to connect the universal opening side to the air extraction machine 16, respectively.

Further, as a peripheral device of the condenser]0, a pure water treatment device 27 including a deaerator configured as C is provided.

Using this pure water treatment device 27 as a supply source, a hot well] 2
A make-up water pipe 28 that supplies pure water to the water supply pipe 28 and a pure water injection pipe 29 that sends pure water to the path from the condenser 10 to the water supply pumps 5a, 5b, and 5c are connected to each other via the make-up water valve 30 and the injection valve 31, respectively. provided.

Additionally, a heating steam pipe 32 is provided via a heating steam valve 33 for supplying heating steam to the pure water introduced into the lower space B.

Next, the startup procedure according to #I above will be explained.

In the stop operation performed prior to starting, first, the isolation valve 23 provided in the communication pipe 22 is fully closed, and at the same time, the pump valve 20 is also closed. Before this stop operation, both the air extraction valve 26 of the first air extraction pipe 24 communicating with the stop space A and the air extraction valve 26 of the second air extraction pipe 25 communicating with the lower space B are opened. Both spaces A
.

The degree of vacuum in B is maintained at the same level. Then both air extraction valves 26 are closed and air extraction a! 16 drive or stop"j
-9, the vacuum in the upper space A is broken and the atmosphere flows into the upper space A. However, 2. The lower space B is completely isolated from the external environment due to the cooperation with the isolation valve 23ε pump artificial valve 20, and is still maintained in a vacuum state. Therefore, there is almost no possibility of 6J dissolving oxygen into the condensate stored in the hot well 12, and if the stoppage time is short, the limit value of dissolved oxygen concentration during operation is 7P.
pb will continue to be maintained.

Thereafter, the manual start-up operation will differ depending on whether the stoppage time is short, such as during DSS operation, or when the plant is to be started up after a long stoppage.

I-If the stoppage time is short, this startup operation is performed because the vacuum in the lower space B is maintained and condensate with a low dissolved oxygen concentration is stored in the hot well 12, so the air extraction valve of the second air extraction pipe 25 is activated. 26 to start the air extractor 16, and further open the pump population valve 20 and start the condensate pump 13 to supply condensate to the grand steam condenser 14.
, the grand seal steam from 8C to the grand steam pipe] 5
The process begins by cutting off the flow of air that is collected through the steam turbines 8a, 8b, and 8C and flows in from the ground portion of each steam turbine 8a, 8b, and 8C. At this time, the condensate supplied to the grand steam condenser 14 is recovered to the condenser 10 through the condensate recirculation system 17, but there is no need to degas it because the dissolved oxygen concentration is low. Next, the first air extraction pipe 2 connected to the upper space A
4 to open the air extraction valve 26 to increase the degree of vacuum in the upper space A, open the make-up water valve 30 to introduce a certain amount of pure water from the deionized water treatment device 27 to the hot well 12 (at this time, the hot well The pure water led to 12 is sufficiently degassed in advance with the deaerator attached to the pure water treatment device 27, and then
Avoid significantly increasing the dissolved oxygen concentration in condensate that is maintained with PB. By the way, the pure water introduced as make-up water at this time is supplied to the steam drums 6a and 6b when the plant is stopped.
, the water level in 6C decreases with the drop in color water temperature, and the specified water level cannot be maintained at the next startup, so the water level in hot well 12 is temporarily restored to normal operation. The water level will be higher than the current water level. After that, when the air in the upper space A is removed and the degree of vacuum rises to a level between the upper space A and the lower space B, the isolation valve 23 is opened and both spaces A
Connect SB.

By the way, in passing water to the waste heat recovery boiler 4, it is necessary to fill the path on the r flow side with respect to the condensate recirculation system 17 in advance with pure water. Therefore, the water deaerated by the pure water treatment device 27 is introduced by opening the injection valve 31, and then the condensate is made to flow from the branch part of the condensate recirculation system 17 to the steam drums 6as 6b, 6c. In this way, the dissolved oxygen concentration at the time of plant start-up is maintained within 80 ppb, and the start-up of the plant can be completed in a short time.

■-When the stoppage time is long On the other hand, when the plant has been stopped for a long time, the startup procedure is to first fully close the isolation valve 23 and the pump valve 20, and extract the air stagnant in the lower space B. When the vacuum level reaches a set value, the heated steam valve 33 is opened to introduce heated steam into the lower space B. Next, the pure water that has been deaerated in advance in the pure water processing bag M27 is guided above the hot well 12 through the replenishment water pipe 28,
The hot well 12 is filled with water while being degassed by the heated steam guided through the heated steam pipe 32. Next, while starting the condensate pump 13 and flowing pure water (condensate) to the grand steam condenser 14, each steam turbine 8a18b
The gland seal steam from 18c is recovered to each steam turbine 8a, 8b.

The flow of air flowing into the condenser 10 from the ground section 8c is blocked. Next, while raising the vacuum in the upper space A by opening the air extraction valve 26 of the first air extraction pipe 24, the make-up water valve 30 is opened and pure water degassed in advance by the deionization device 27 is poured into the hot well. Lead to 12. Thereafter, the air in the upper space A is discharged, and when the degree of vacuum rises to the same level as that in the lower space B, the isolation valve 23 is opened to allow both spaces A and B to communicate with each other. Then, water filling using deaerated water in the deionized water treatment device 27 is completed for the route from the condensate recirculation system 17, which is proceeded with the above process, to the steam drums 6as 6b, 6c via the water supply pumps 5a, 5b, 5c. Waiting for this, the steam drums 6a, 6b,
Condensate water (water supply) is supplied over 6c. This condensate can satisfy the limit value of dissolved oxygen concentration of 80 ppb or less at the time of plant startup, and even after the plant has been stopped for a long period of time, startup can be completed in a short time.

In addition, although the above description is about a combined cycle power plant, the application of the present invention is not limited to this. Namely, a boiler that generates steam, a steam turbine driven by the steam from the boiler, a condenser that receives and condenses the exhaust of the steam turbine, and condensate (feed water).
Similar effects can be obtained if applied to a steam turbine plant configured by combining a feed water pump that boosts the pressure of water and sends it to a boiler.

[Effects of the Invention] As is clear from the above description, the present invention airtightly partitions the inside of a condenser into an upper space for accommodating a tube bundle and a lower space for accommodating a hot well. A communication pipe with an isolation valve that can be opened and closed is connected to the lower space to form a communication passage for condensate, and a pure water treatment equipment equipped with a deaerator is connected above the hot well. In addition, an air extraction device is installed so that it can communicate with both the upper and lower spaces, and when starting the plant, an isolation valve is used to cut off communication between the upper and lower spaces, and the air extraction device is used to maintain a vacuum in the lower space. At the same time, pre-degassed pure water from the water treatment equipment is supplied to the hot well and then circulated through the recirculation system, and while the vacuum in the headspace is maintained by the air extractor, the isolation valves are opened to separate both spaces. This allows the dissolved oxygen concentration in the condensate to be lowered to the startup limit of 80 ppb at an early stage, reducing the time required for startup.
This has the excellent effect of being able to quickly respond to the demands of the power demand side and supply power.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a condensing device used in a method for starting a steam turbine plant according to the present invention, and FIG. 2 is a system diagram showing an example of a condensing device used in a conventional starting method. . 10...Condenser 11...Tube bundle 12...Hot well 16...Air extractor 17 ......Condensate recirculation system 21...
・・・・Partition member 22・・・Communication pipe 23・・・・Isolation valve 24.25・・Air extraction pipe 27・・・・Pure Water treatment device 28...Supplementary water pipe 29...Pure water injection pipe

Claims (2)

[Claims] (1) In a method for starting a steam turbine plant comprising a condenser that condenses exhaust gas of a steam turbine and recovers it as condensate, the inside of the condenser accommodates a tube bundle that condenses the exhaust gas of the steam turbine. The upper space is airtightly divided into an upper space and a lower space accommodating a hot well that receives and stores condensed water, and an isolation valve that can be opened and closed is provided between the upper space and the lower space. A communication pipe is connected to form a communication passage for condensate, and is connected to a pure water treatment device equipped with a deaeration device above the hot well, and an air extraction device is connected to the upper and lower spaces. When starting up the plant, the isolation valve is closed to cut off communication between the upper space and the lower space, and while maintaining the vacuum in the lower space by the air extractor, the purified water is Pre-degassed pure water from a treatment device is supplied to the hot well and further circulated through a condensate recirculation system, and then the air extraction device raises the vacuum in the head space to approximately equal to the bottom space. 1. A method for starting a steam turbine plant, comprising: opening the isolation valve to communicate between the two spaces while maintaining the hot well, and then supplying condensate from the hot well to the boiler. (2) The inside of the condenser is airtightly divided into an upper space that accommodates a tube bundle that condenses steam turbine exhaust gas and a lower space that accommodates a hot well that receives and stores condensed water. , a communication pipe having an isolation valve that can be opened and closed is connected between the upper space and the lower space to form a communication passage for condensate, and a pure water treatment apparatus equipped with a deaerator; A condensing device connected above a hot well and further comprising an air extraction device so as to be able to communicate with both the upper and lower spaces.