JPS6057190A - Condensation system of power generating plant - Google Patents

Abstract

PURPOSE:To allow the operation of only one condensating pump having a large capacity and a high overall lift during night time hours in a mutiple axis power generating plant so as to reduce the power consumption by auxiliary systems by disposing a ground steam condensor in the middle of a feed water pipe which supplies the water in a feed water tank to a condensor. CONSTITUTION:A ground steam condensor 9 is disposed in the middle of a feed water pipe 25 to a condensor 7, and a valve 26 for separation is provided at a feed water inlet of the condensor 7. Between the outlet side of the ground condensor 9 and a feed water tank 12, a minimum flow pipe 28 and a minimum flow valve 27 are provided in order to secure the minimum flow to the ground condensor 9. The water at a reduced temperature to a temperature reducer 17 is supplied from a ground steam temperature reducing water feed pipe 31 which is brfanched from the feed water pipe 25. When shafts are stopped during night time hours, the valve 26 is closed and the minimum flow value 27 is opened so that the cooling is conducted while the minimum flow to the ground steam condensor 9 is secured.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a condensate system of a power generation plant, and particularly relates to a condensate system of a power generation plant, which does not require a deaerator, is frequently started up and stopped, and requires no replenishment to the condenser. In many cases, in conditions where one plant is composed of multiple power generation units or where multiple power generation plants are installed next to each other, when some power generation units or power generation plants are stopped at night, etc., the in-house power for driving auxiliary equipment is The present invention relates to a condensate system suitable for reducing plant restart time by significantly reducing the amount of water and improving the deaeration performance of the condenser.

[Background of the invention]

As an example of the prior art, a combined power generation plant using a gas turbine and a steam turbine will be explained with reference to FIGS. 1 and 2. In the figure, a combustor 2 of a gas turbine 1
The gas turbine 1 is rotated by high-temperature combustion gas obtained by mixing and burning the air compressed by the compressor 3 and the fuel LNG gas, thereby generating electricity. The high-temperature exhaust gas after working in the gas turbine 1 heats and evaporates condensate in the exhaust heat recovery boiler 4.
This steam rotates the steam turbine 5 to generate electricity.

6 indicates a generator. The steam that has done work in the steam turbine 5 is condensed in a condenser 7, pumped out by a condensate pump 8, and supplied to the exhaust heat recovery boiler 4 via a grand steam condenser 9.

In order to suppress the generation of nitrogen oxides (NOx) in the combustor 2, in this example, the extracted air from the steam turbine 5 and the condensate from the condensate pump 8 are mixed in the desuperheater 10, and the steam injection device 11 An example is shown in which a so-called steam injection method is adopted in which steam is injected into the combustor 2 via the steam injection method.

The amount of extracted air and condensate consumed for this steam injection is:
10 to 30% of the amount of condensate sucked out and sent from the condenser 7
reach even. To make up for this water shortage, the make-up water tank 12
A large amount of make-up water is supplied to the condenser 7 via the make-up water pump 13 and the hot well water level adjustment valve 14 of the condenser 7. At this time, the dissolved oxygen concentration in the make-up water is as high as about 50 to 1 ooppb, as shown in Figure 3, and a large amount of make-up water increases the dissolved oxygen concentration in the condensate at the outlet of the condenser 7. There is a possibility that the amount of water cannot satisfy the value required by the exhaust heat recovery boiler 4.

As a countermeasure for this, for example, a deaerator can be installed, but in the case of a one-story plant such as a combined plant, it must be built in a commercial building to provide sufficient hydrostatic head, and the cost of the deaerator itself increases. , generally no deaerator is provided. Therefore, in this example, the condenser 7 is structured to have deaeration performance.

That is, before the condensed water from the steam turbine 5 falls into the hot well, it is brought into contact with a portion of the turbine exhaust inside the condenser 7 to perform reheat deaeration. In the case of the combined plant of this example, the exhaust heat recovery boiler 4, the gas turbine 1, the steam turbine 5, the condenser 7, etc. are considered as one unit, and seven units of these are provided, making up a so-called multi-shaft type power generation plant. It is said that This is to take advantage of the ease of operation of starting and stopping at night, etc.

Next, we will explain how to operate the night stop.

At night, only one of the seven shafts continues to operate, and the other six shafts, including the exhaust heat recovery boiler 4, gas turbine 1, and steam turbine 5, are stopped. However, in order to shorten the restart time after a shutdown, it is necessary to quickly establish the quality of the exhaust heat recovery boiler feed water (deaeration) by shortening the vacuum rise time and reducing the dissolved oxygen concentration in the condensate. For this reason, it is necessary to maintain the ground seal and vacuum of the steam turbine 5 even for the six shafts that are stopped.

The steam for grand sealing is supplied from the main steam pipe 15 of the single axis of operation.
It is then branched out and supplied to each shaft via a pressure reducing valve 16. The supplied steam is mixed with the condensate discharged from the condensate pump 8 in the desuperheater 17, and is supplied to the steam turbine gland section 18 for steam sealing. Leak-off of air and seal steam sucked in from the atmosphere is condensed in the gland steam condenser 9, and drain is collected in the condenser 7 via the drain U seal pipe 19, drain recovery tank 20, and drain recovery pump 21. .

On the other hand, non-condensed air is discharged to the atmosphere by the blower 22. Further, vacuum is ensured by a vacuum pump 23.

When the system is stopped at night, the condensate pump 8 must be continuously operated for the other six axes to supply condensate as cooling water to the gland steam condenser 9. At this time, since the exhaust heat recovery boiler 4 is stopped, the condensate recirculation valve 24 is opened, and cooling water for the grand steam condenser 9 is secured through a small closed circuit that returns condensate to the condenser 7.

Here, the condensate pump 8 has no deaerator in the middle and NO
As a result of the requirement for condensate pressure to overcome the bleed pressure of the turbine for steam injection as a countermeasure against x, the total head of the specific bomb has become high in ordinary thermal power plants and the like.

In this way, operating seven high total head pumps together at night for the sole purpose of cooling the grand steam condenser 9 requires a very large amount of auxiliary machinery, which has the advantage and disadvantage of operability in a plant that frequently starts and stops. It's a big issue that affects the world.

As described above, the conventional technology has the following problems.

(1) Continuous operation of all 8 condensate bonders with a high total head even at night consumes a large amount of auxiliary power.

(2) By supplying a large amount of make-up water to the condenser 7, dissolved oxygen in the condensate to the exhaust heat recovery boiler 4 increases.
The time spent degassing to ensure water quality becomes longer, and the restart time becomes longer.

(3) Since the downstream side of the condensate recirculation valve 24 is the vacuum condenser 7, the restriction (differential pressure) in the condensate recirculation valve 24 is large, resulting in wear and tear of the valve seat, erosion of the piping downstream of the valve, etc. In addition to shortening the lifespan of piping and valves, vibration and noise around the valves also become a problem.

[Purpose of the invention]

An object of the present invention is to provide a condensate system for a power plant that can solve the problems of the prior art.

[Summary of the invention]

In order to achieve this objective, the condensation system of the power plant of the present invention is characterized in that a ground steam condenser is installed in the middle of the make-up water piping that sends the make-up water storage water to the condenser. shall be.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 4 and 5. In FIG. 4, the same reference numerals as in FIGS. 1 and 2 represent the same or equivalent components. In the condensation system according to the present invention, a grand steam condenser 9 is installed in the middle of the make-up water piping 25 to the condenser 7, an isolation valve 26 is provided at the make-up water inlet of the condenser 7, and A minimum flow pipe 28 and a minimum flow valve 27 are provided between the outlet side of the grand steam condenser 9 and the make-up water tank 12 to ensure the minimum flow rate of the grand steam condenser 9.
The structure is such that deheated water is supplied from a gland steam deheated water injection pipe 31 branched from the make-up water pipe 25.

Next, we will explain the operation.

When the six shafts are stopped at night, the valve 26 is closed and the minimum flow valve 27 is opened to perform cooling while ensuring the minimum flow rate of the grand steam condenser 9. Further, the deheated water of the gland steam to the desuperheater 17 is supplied through the make-up water pipe 25 at the outlet of the gland steam condenser 9 and the deheated water injection pipe 31 of the desuperheated gland steam. Note that during this period, the condensate pumps 8 of the systems that are not being driven may be stopped. The amount of condensed water in the grand steam condenser 9 is negligibly small compared to the storage capacity of the condenser 7, and although the water level in the condenser 7 becomes high for about 8 hours at night, it does not cause problems such as alarms. do not have. Furthermore, in this regard, it is possible to ensure complete safety by adopting the operation shown in FIG.

That is, before entering the night shutdown, the set water level (NWL) of the condenser 7 for six axes may be lowered to the night NWL by changing the set value of the condenser water level regulator 29.

It goes without saying that the control range should be selected so that the control range does not reach the low water level (LWL>) and an alarm is generated by the low water level switch 30. Note that ΔL1 is the daytime control range, and ΔL2 is the nighttime control range. show.

On the other hand, during normal operation during the day, the valve 26 is opened and the minimum flow valve 27 is closed to replenish the condenser 7.

As explained above, the following effects can be obtained in this embodiment.

(1) Six large-capacity, high-head condensate pumps 8 are stopped during the night, resulting in a savings of approximately 6,000 MW-I (/year) of in-plant power for a 10,100 O class combined plant.

(9) (2) Make-up water to the condenser 7 is heated in the grand steam condenser 9, reaches a temperature υ higher than the saturation temperature in the condenser 7, and is transferred to the condenser 7. No, the deaeration effect of the flash during spraying increases compared to unheated make-up water. Therefore, the deaeration performance of the condenser 7 is improved.

(3) Spray make-up water into condenser 7 If the dissolved oxygen concentration after deaeration is constant, the required spray pressure will differ by 30% as shown in Figure 6 with and without heating the make-up water. At the time of make-up water (maximum), it is estimated that the amount of water with heating is about half of that without heating.

As a result, the total head of the make-up water pump 13 becomes smaller, and the internal power for driving the pump is also significantly reduced.

(4) It is not necessary to operate the condensate recirculation valve 24 at night, which makes it possible to ensure the service life of piping and valves, and to avoid vibrations and noise.

(5) The condensate recirculation valve 24 is opened for a short time during the pump startup process to ensure the minimum flow of the condensate pump 8, but the condensate recirculation valve 24 is opened for a short period of time during the pump startup process to ensure the minimum flow of the condensate pump 8. The minimum flow of 8 is approximately 3
The capacity of 0 to b24 can be reduced.

In the above embodiment, the return destination of the minimum flow pipe 28 of the grand steam condenser 9 may be the make-up water pipe 25 on the population side of the make-up water pump 13.

FIG. 7 shows another embodiment of the present invention applied to a steam turbine power plant. In this power generation plant, the extracted air from the steam turbine 5 is sent and consumed as auxiliary steam for the factory, and a large amount of air is supplied to the condenser 7, and multiple power generation plants are installed next to each other, each providing steam backup. It is effective if you do it.

FIG. 8 also shows an example in which the present invention is applied to a thermal power plant as another embodiment of the present invention.
The in-house steam generated in step 3 is used as ground seal steam for the turbine via an in-house steam pipe 34 and an in-house steam supply valve 35.

(11) Therefore, as in this embodiment, the present invention can be implemented even in the case of a multi-shaft combined power generation plant or a single unit rather than multiple units, and the vacuum and grounding can be achieved by stopping the condensate pump 8 during no load. It is possible to maintain the seal.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

(1) In a multi-shaft power generation plant, only one large-capacity, high-head condensate pump needs to be operated at night, so the consumption of auxiliary power can be significantly reduced.

(2) Since the make-up water to the condenser can be heated and sprayed, the deaeration performance of the condenser can be improved.

(3) Improved deaeration performance of the condenser reduces deaeration time to ensure water quality, and restart time can be shortened.

(4) No need to operate the condensate recirculation valve at night,
Not only can the lifespan of piping and valves be secured, but also vibration and (12) noise can be avoided.

[Brief explanation of the drawing]

Figure 1 is a schematic system diagram of a conventional multi-shaft combined power generation plant, Figure 2 is a detailed diagram of one unit in Figure 1, and Figure 3 is a diagram showing condenser hotwell water temperature, degree of vacuum, and
FIG. 4 is a diagram showing an embodiment of the present invention, and is a detailed system diagram of one unit in a multi-shaft combined power generation plant equipped with a condensate system according to the present invention.
Fig. 5 is an explanatory diagram showing the nighttime operation of the condenser hot well water level, Fig. 6 is a diagram showing the characteristics of make-up water amount and condenser required spray pressure, and Figs. 7 and 8 are diagrams showing the characteristics of the condenser hotwell water level. FIG. 3 is a schematic system diagram showing another example. 5... Steam turbine, 7... Condenser, 9... Grand steam condenser, 12... Make-up water tank, 13...
Make-up water pump, 25... Make-up water piping, 26... Valve,
27... Minimum flow valve, 28... Minimum flow pipe. Agent Patent Attorney Masami Akimoto (13) No. S Kokukatsu et al. Water content error” T5 No. 30

Claims (1)

[Claims] 1. A condenser that condenses steam from a steam turbine, a gland steam condenser that condenses steam from the steam turbine, and a pump and piping to supply condensate to the condenser. In a condensation system of a power generation plant equipped with a make-up water tank for replenishment, the ground steam condenser is installed in the middle of a make-up water piping that sends water stored in the make-up water tank to the condenser. Plant condensate system. 2. In claim 1, piping and valves are provided between the downstream side of the grand steam condenser and the make-up water tank to ensure the minimum flow rate of the grand steam condenser. A condensate system for a power generation plant characterized by the following.