JPH02169807A - Combined power plant - Google Patents

Abstract

PURPOSE:To shorten the time of manipulation of start of a power plant unit without the use of complicated system by returning condensate water which has been transferred into a reserving tank insulated from the atmosphere during stop of the unit, at the time when the vacuum increases before the start. CONSTITUTION:Upon stop of a unit, condensate in a condenser 6 is transferred into a reserving tank 51 before vacuum break of a condensate pump 7. Thereby the condensate pump 7 is stopped to give a vacuum break. Thereafter, the degree of vacuum of a condenser 6 is raised during start thereof up to a predetermined value, and thereafter, shut-off valves 52, 53 are opened so as to automatically lay water in the condensor 6 without driving the other drive pump. With this arrangement, condensate may be returned to the condenser 6 in a low dissolved oxygen concentration condition without being exposed to the atmosphere, thereby it is possible to restart the unit in a short time without using deaeration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combined power generation plant, and particularly to a plant system suitable for shortening plant start-up time.

[Conventional technology]

A combined cycle power plant has good plant efficiency as the gas turbine temperature rises (plant efficiency is about 46-47% when the gas turbine inlet gas temperature is 1300°C). In addition, the plant is suitable for DSS (daily start and stop) or intermediate load operation, as the start and stop operations are easy and the start time is quick.

In particular, as the proportion of nuclear power generation equipment in total output increases, the number of equipment plans for nuclear power generation equipment increases.

An overview of the system of a conventional steam cycle plant is shown in Figure 3. A deaerator 1 is installed to keep the dissolved oxygen (Dot) in the water supply as low as possible, and to prevent accidents due to corrosion within the system.
2 is installed.

In addition, 1 in the figure is a waste heat recovery boiler, 2 is a high pressure main steam, and 3 is a waste heat recovery boiler.
is low pressure main steam, 4 is steam turbine, 5 is generator, 6 is condenser, 7 is condensate pump, 8 is ground condenser, 9 is condensate recirculation system, 10 is heating steam, 11 is water stop valve, 1
2 is a deaerator, and 13 is a water supply pump.

In the case of a combined cycle power plant, since the output of each unit is small, one plant is usually composed of multiple units.
Or generate 1 million kW of power.

Therefore, in order to make effective use of the plant site, a method of incorporating a deaerator into the boiler as shown in FIG. 4 has been adopted. (Refer to Japanese Unexamined Patent Publication No. 57-84903.) In this method, a deaeration boiler 35 is installed in the lowest gas region of the boiler, and the feed water is deaerated using the heated deaeration steam 40 generated by the boiler.

In addition, 30 in the figure is a high pressure superheater, 31 is a high pressure evaporator, 3
2 is a high pressure energy saver, 33 is a low pressure evaporator, 34 is a low pressure energy saver, 35 is a deaeration boiler, 36 is a feed water preheater, 37 is a low pressure feed water pump, 38 is a high pressure feed water pump, 40 is a heating for deaeration It's steam.

The condenser 6 of the steam turbine 4 has a deaeration function by itself, and if the -degree load increases, the DO□ in the water supply increases.
The concentration is maintained at 10 ppb or less and can satisfy the water supply group 1# value.

However, is it possible to control the Doztn degree at startup? 11, it is necessary to add another function, and the heating steam 10 is introduced into the condenser 6 while the condensate is recirculated by the condensate re-VFI ring system 9 as shown in FIG. This achieves the purpose of degassing the feed water.

The effectiveness of this method has already been confirmed in actual equipment, and this method is called the condenser degassing method.

[Problem to be solved by the invention]

In the case of the conventional degassing boiler 35 shown in FIG. 4, a feed water preheater 36 is installed on the gas downstream side of the degassing boiler 35 due to thermal efficiency issues.
Therefore, in the case of a DSS operation plant, the DO2 is high every time the plant is started up and corrosion is likely to occur in the pipes, as the water is passed through before deaeration.

Furthermore, as shown in Fig. 7, from the gas turbine gas MWg and gas temperature Tg characteristics, in the range (a) there is a shortage of degassed steam, and in the range (b) there is excess steam from the degassed boiler 35, so there is no excess or deficiency. There is a problem in that a system for introducing and exhausting steam is required, which necessitates a complicated system control configuration.

In addition, in the case of the latter condenser deaeration method, although the equipment is simple, there is a problem in that it takes time to prepare before starting up. In other words, the vacuum of the condenser is destroyed in order to reduce the power consumption at night in the DSS plant, and the vacuum in the condenser is awaited for the next morning's start-up.As a result, the condensate absorbs the 0□ in the air, and the DO□ at the time of start-up is reduced. reaches approximately 10,000 ppb.

FIG. 6 shows the temporal change in DO□ concentration due to the condensate recirculation system 9 and heating 10 in FIG.
Approximately 1 hour of pre-startup operation time is required to reach this point.

An object of the present invention is to provide a combined power generation plant that does not require a complicated system and can shorten startup operation time.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention (first invention)
In the condenser degassing method shown in Fig. 5, when the unit is stopped, the condensate in the condenser is transferred to a water storage tank isolated from the atmosphere before the vacuum is broken, and the Dot concentration is maintained so as not to increase while the unit is stopped. It is characterized in that it is configured to return to the condenser when the vacuum inside the condenser rises before startup.

In order to achieve the above-mentioned object, the present invention (second invention) further provides a water storage tank for isolating the feed water deaerated by the condenser from the atmosphere even during unit operation, and stores the condensate when necessary. It is characterized in that it is configured so that water can be transferred to a tank and also supplied to the boiler from the water storage tank.

[Effect]

In the first invention, since the condensate is isolated from the atmosphere during the period when the condenser is vacuum-broken, oxygen does not dissolve into the condensate, and the condensate is returned after the vacuum rises in the condenser. There is no problem in dissolving O2 in water.

In the second invention, the necessary amount of condensate is retained in an isolated water storage tank regardless of the DOz concentration of the condensate in the condenser, and the condensate recirculation system is used until the deaeration in the condenser is completed. In the meantime, the low DO□ water in the water storage tank can be sent to the HR3G, so there is no need to wait for degassing, and startup can be done in a short time.

[Embodiments of the invention]

FIG. 1 is a system diagram showing a first embodiment of the present invention.

High pressure main steam 2 generated in exhaust heat recovery boiler (HR3G) 1
, low pressure main steam 3 is introduced into a steam turbine 4. The rotational power is given to the generator 5 and replaced with electricity.

The steam that has finished its work is condensed in the condenser 6, and sent again to the HR3G1 as water supply by the condensate pump 7.

When the unit is stopped, the condenser 6 is
In this case, the condenser 6 is filled with air and O! is destroyed in the condensate. is dissolved, and the Dog concentration rises to the saturation point of 9,000 to 10,000 ppb at startup the next morning. In this case) Is it possible to pass water to IR3GI? I
It is necessary to deaerate to 4 degrees TOPPB, and by recirculating the condensate in the condensate recirculation system 9 and blowing heated steam 10 into the condenser 6, water can be passed after about 1 hour. Possible reference values can be reached.

Normally, a power plant needs to start up the load around 5 to 6 a.m., but in the conventional method, it was necessary to start the start-up operation an hour earlier.

According to the present invention, before the vacuum of the condensate pump 7 is broken when the condensate pump 7 is stopped, the condensate in the condenser 6 is sent to the water storage tank 51 while the pump 7 is in operation, and then the condensate pump 7 is stopped. , carry out vacuum breakdown. At startup, the degree of vacuum in the condenser 6 is increased and after reaching the specified degree of vacuum, by opening the stop valves 52 and 53, it is possible to automatically fill the condenser 6 with water without going through other drive pumps. shall be.

In this way, the condensate is stored in the water storage tank 51 in a state where it does not come into contact with the atmosphere when the plant is stopped, so that it is possible to start up the plant immediately without the deaeration operation by recirculation. Even if the condensate in the condenser 6 is transferred to the water storage tank 51, the water supply DOtflA degree in the condenser may increase, but the residual water supply volume in the system is about 1/20 of the transferred condensate. Since the amount is small and can be shut off with a valve, high DO
The amount of retained water in No. 7 is extremely small. Therefore, after mixing with the water supply in the water storage tank 51, the Do
, and even if a degassing operation is required, it will only take a short time.

The water storage tank 51 may be of a sealed type or of a floating type, and as shown in the figure, it may be of a pressure control type, such as N,
A type in which the pressure is controlled by supplying Nff1 gas from a supply stage (l?ti 54) may also be used. In the figure, 55 is a pressure regulating valve, and 56 is a detection device.

According to this embodiment, the following effects can be achieved.

The travel time can be reduced by about 1 hour.

The operator's working time can be reduced by at least one hour, making it possible to save costs.

2) Saving pump power for deaeration and steam for heating is equivalent to 2x10 bKcal of calorie per unit at each start-up, which is approximately 50 tons/unit in oil equivalent per year.

3) It is possible to use low grade materials because there is no need to circulate high Dotru water into the system.

4) Conventionally, when it is necessary to start up a plant urgently, the high DOt'1M degree condensate in the condenser is discharged, resulting in a low DO! Concentrated make-up water is replaced, which used to waste water, but now it is possible to save water.

As another embodiment of the present invention, as described above, the water storage tank 5
Even if a make-up water tank is used instead of 1, the function is the same. FIG. 8 shows a second embodiment of the present invention, in which a deaerator 12 is provided within the condensate recirculation system 9.

The effects of this embodiment are as follows: 1) Since it is separate from the main system, the capacity is only 1/10 to 1/2 o, in this case it is sufficient to target 15 to 20 o of condensate, and therefore the equipment cost is also reduced. It will be cheaper.

2) Combined with condensate deaeration, the time required to complete deaeration is 1/6 of that of conventional methods.
It is possible to shorten the number to about 115.

FIG. 2 shows a third embodiment of the present invention. In this embodiment, the space inside the condenser 6 is utilized and a water storage tank 51 is provided in that space.

FIG. 9 is a system diagram for explaining a fourth embodiment of the present invention.

According to this embodiment, the condensate supply system 61 that supplies condensate to the water storage tank 60 is connected to the condensate pump 7 outlet (R3G
Branches from the main water supply system at the 1st inlet. And condensate return system 6
2 is connected between the condensate pump 7 and the pump inlet stop valve 64, and a condenser connecting pipe 63 is connected between the cavity of the water storage tank 60 (steam trunk) and the cavity of the condenser 6. It is connected.

During plant operation, the condensate in the condenser 6 is sufficiently low DOt
This condensate is 7 kg/am” to 60 kg.
/cm'', water can be easily supplied to the water storage tank 60 by opening the stop valve a.

When the plant is stopped, if the stop valves a, b, and c are closed, even if the water supply device 6 is vacuum-broken, it is completely cut off from the atmosphere, and the Do, ? ! It does not increase the temperature by 1 degree.

Furthermore, at startup, condenser deaeration is started by starting the recirculation system 9, but HR3GI is also started in the same way, until the condenser deaeration is completed and water can be supplied from the condenser 6. During this time, water is supplied from the condensate return system 62 from the water storage tank 60. Even if stop valve a is opened at this time, a vacuum has already been created and air from the condenser 6 will not enter the water storage tank 60.
Only the low D Oz water in the water storage tank 60 is sent to the boiler, so there is no waiting time until the condenser degassing is completed, and a short start-up is possible.

FIG. 10 is a system diagram for explaining the fifth embodiment of the present invention.

In the case of this example, the water supply pump standby unit or 50%
Two capacity pumps? A and 7B are used to operate the recirculation system 9 and the water supply system from the water storage tank 60 in parallel.

In addition, since the combined power generation plant is composed of multiple units, the water storage tank 60 can be shared, and in this case, one dedicated pump is installed separately to supply water from the water storage tank 60, and each unit is separately supplied with water. It is also possible to remove the spare pump.

In this way, in this embodiment, it is possible to share pumps, reduce the number of pumps, and simplify the system.

As in the fourth and fifth embodiments, the condenser 6
By connecting the water storage tank 60 with the connecting pipe 63, it is easy to transfer water and extract water, and there is no need for a gas cylinder such as nitrogen gas to prevent air leakage, and there is no need for a pressure control device. Become.

When using nitrogen gas, approximately 30 to 4 ONm3 at each startup
As a result, in a 10100O class plant, approximately 10,000 501x130atg cylinders are consumed per year, so when cylinder replacement and filling work are taken into consideration, this is a significant labor saving.

〔Effect of the invention〕

According to the first invention, when the unit is stopped, the condensate in the condenser can be transferred to the water storage tank, and when the unit is restarted, it can be returned to the condenser in a low DO□ concentration state without being exposed to the atmosphere. , which eliminates the need for degassing operations and enables restarting in a short time.

According to the second invention, the condensate is DO2 of condensate in the condenser.
Regardless of the temperature, the required amount is maintained in an isolated water storage tank, and the recirculation system allows the low D Oz feed water in the storage tank to be sent to the HR3G until deaeration is completed in the condenser. , there is no need to wait for degassing, allowing for even shorter startup times.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a combined power generation plant according to the first embodiment of the present invention, Fig. 2 is a partially enlarged view of another embodiment, and Figs. 3, 4, and 5 are diagrams of the conventional example. System diagram, Figure 6 is a degassing characteristic diagram of the condenser, Figure 7 is a load characteristic diagram of the degassing boiler, and Figures 8, 9, and 10 are combined power generation plants according to other embodiments. This is a system diagram of 1・・・・・・・・・HR3G, 4・・・・・・・・・
Steam turbine, 5... Generator, 6...
...... Condenser, 7... Condensate pump, 51.60... Water storage tank, 61...
... Old condensate supply system, 62 ... Condensate return system, 63 ... Condenser connection pipe, 64
・・・・・・・・・Pump inlet stop valve. Figure 3 Figure 4 Figure 2 Figure 5 Figure 6 to tsa tsA Figure 7 Figure 8 Figure 9 Figure 10

Claims (3)

[Claims] (1) In a combined power generation plant equipped with a boiler, a steam turbine, a generator, and a condenser, a water storage tank is provided to cut off the condensate in the condenser from the atmosphere when the unit is stopped, and the unit A combined power generation plant characterized in that it is configured to transfer condensate to its water storage tank when the unit is stopped and to return condensate from the water storage tank to the condenser when the unit is started. (2) In a combined power generation plant equipped with a boiler, a steam turbine, a generator, and a condenser, a water storage tank is provided to isolate the feed water deaerated by the condenser from the atmosphere during unit operation. . A combined power generation plant, characterized in that it is configured such that condensate can be transferred to the water storage tank when necessary, and water can be supplied from the water storage tank to the boiler. (3) In claim (2), the condensate supply system to the water storage tank is branched from the main water supply system between the condensate pump outlet and the boiler inlet, and the return system from the water storage tank is connected to the condensate pump inlet stop valve. A combined power generation plant characterized by having a connecting pipe connected to the downstream side of the water storage tank and the condenser cavity.