JP2002004809A - Steam power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stem power plant, capable of extracting steam from a system without impairing original plant performance. SOLUTION: The steam power plant 1 is formed that a once-through boiler 2 comprising a superheater 3 and a reheater 4, and a steam turbine ST, consisting of a high pressure turbine HT, an intermediate pressure turbine IT, and a low pressure turbine LT are combined together. The superheater 3 and the high-pressure turbine HT are interconnected via a main steam line MSL and steam flowing out from the high-pressure turbine HT is returned to the reheater 4 via a cold reheat line CRL. Furthermore, by releasing a change-over valve CV and a bypass flow regulating valve FRV1, a part of steam in a main steam line MSL can be led to the cold reheat line CRL via a bypass line VL. Further, water from a feed water pump FP can be sprayed in a desuperheater 9 of the bypass line VL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam power plant, and more particularly, to a steam power plant that drives a steam turbine with steam generated by a once-through boiler.

[0002]

2. Description of the Related Art Conventionally, a steam power plant as shown in FIG. 2 is known. Steam power plant 1 shown in FIG.
01 is a combination of a once-through boiler 102 having a superheater (superheater tube) 103 and a reheater (reheater tube) 104 and a steam turbine ST. The steam turbine ST includes a high-pressure turbine HT, a medium-pressure turbine IT,
And a low-pressure turbine LT.
The generator EG is driven by utilizing the energy of the steam generated in the step (a).

As shown in FIG. 2, a steam inlet of the high-pressure turbine HT is connected to a once-through boiler 10 through a main steam line MSL.
2 and connected to the superheater 103 of the high pressure turbine HT
, The steam superheated by the superheater 103 is supplied as a drive source. The steam that has lost energy due to expansion in the high-pressure turbine HT is returned to the reheater 104 of the once-through boiler 102 via the low-temperature reheat line CRL. The steam reheated by the reheater 104 is supplied to the high-temperature reheat line HR.
The steam that has been supplied to the intermediate pressure turbine IT via L and has lost energy due to expansion in the intermediate pressure turbine IT is supplied to the low pressure turbine LT.

[0004] The steam that has lost energy due to expansion in the low-pressure turbine LT is introduced into a condenser C via a condensate line CWL, and is cooled and condensed. The condensate recovered by the condenser C is pumped to the condensate desalination device 105 by the condensate pump CP. The condensed water desalinated by the condensate desalination device 105 is supplied to the low-pressure heater 10 by the condensate boost pump BP.
6 to the deaerator 107. The condensed water deaerated by the deaerator 107 is supplied to the superheater 103 of the once-through boiler 102 via the high-pressure heater 108 and the water supply line FWL by the water supply pump FP.

[0005]

A steam power plant equipped with a once-through boiler as described above is often used as a power supply source for various factories and the like. May be required to be used as a steam supply source in addition to the use as a steam source. In such a case, it is conceivable to extract steam from the main steam line connecting the superheater of the once-through boiler and the steam turbine (high-pressure turbine) from the relationship of the steam temperature / pressure and the like.

However, in a once-through boiler, the main steam condition is generally determined from the water supply condition and the boiler heat input condition, and the reheat steam condition is generally determined from the main steam condition, the high pressure turbine loss coefficient, and the boiler heat input condition. It is. Therefore, when a large amount of steam is extracted from the main steam line connecting the superheater and the steam turbine, the amount of steam returned from the steam turbine (high-pressure turbine) and returned to the reheater of the once-through boiler decreases, The reheat steam conditions will be different from the design of the once-through boiler. In this case, since the reheater tube constituting the reheater of the once-through boiler is overheated, the reheater tube may be damaged by erosion or the like.

Accordingly, an object of the present invention is to provide a steam power plant capable of extracting steam from a system without impairing the original plant performance.

[0008]

According to a first aspect of the present invention, there is provided a steam power plant for driving a steam turbine by steam generated by a once-through boiler having a superheater and a reheater. A main steam line connecting the superheater and the steam turbine, a reheat line for returning steam from the steam turbine to the reheater, and a bypass line for leading steam flowing through the main steam line to the reheat line, Water supply means for supplying moisture into the bypass line.

This steam power plant can extract steam from the main steam line and use it as a steam supply source while providing the original use such as power supply. That is, in this steam power plant, the main steam line connecting the superheater of the once-through boiler and the steam turbine, and the reheating line for returning steam from the steam turbine to the reheater are connected by the bypass line. . Also,
Water can be supplied into the bypass line by water supply means (preferably, water is sprayed).

By opening the bypass line, a part of the steam superheated by the superheater can be led from the main steam line to the reheating line. In addition, since water can be further supplied from the water supply means to the steam flowing from the main steam line to the bypass line, the amount of steam can be further increased in the bypass line. Therefore, in this case, in addition to the steam from the steam turbine, the steam from the bypass line is introduced into the reheater of the once-through boiler.

As a result, even if a large amount of steam is extracted from the main steam line and the amount of steam flowing out of the steam turbine to the reheating line is reduced, the reheater of the once-through boiler satisfies the design conditions. Since the amount of steam can be introduced, it is possible to prevent the reheater tube from being overheated. Thus, according to the steam power plant according to the present invention, steam can be extracted from the system without impairing the original plant performance. If steam is not extracted from the main steam line, the bypass line may be closed,
The plant performance is not impaired at all.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a steam power plant according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing a steam power plant according to the present invention. The steam power plant 1 shown in FIG.
This is a combination of once-through boiler 2 and steam turbine ST. The once-through boiler 2 mainly includes a boiler body 2a,
It has a superheater tube T3 forming the superheater 3 together with the boiler main body 2a, and a reheater tube T4 forming a reheater 4 together with the boiler main body 2a. The steam turbine S
T consists of a high-pressure turbine HT, a medium-pressure turbine IT, and a low-pressure turbine LT, which are connected coaxially,
The generator EG is driven using the energy of the steam generated in the superheater 3 and the reheater 4 of the once-through boiler 2.

As shown in FIG. 1, the steam inlet of the high-pressure turbine HT is connected to a superheater 3 (superheater tube T3) of the once-through boiler 2 via a main steam line MSL. The steam superheated by the superheater 3 is supplied as a drive source. The steam that has lost energy due to expansion in the high-pressure turbine HT passes through the low-temperature reheat line CRL, and is reheated by the reheater 4 (reheater tube T4) of the once-through boiler 2.
Will be returned to Then, the steam reheated by the reheater 4 is supplied to the intermediate-pressure turbine IT via the high-temperature reheat line HRL. The steam that has lost energy due to expansion in the intermediate-pressure turbine IT is supplied to the low-pressure turbine LT as a drive source.

On the other hand, the steam that has lost energy due to expansion in the low-pressure turbine LT passes through a condenser line CWL to a condenser C.
And cooled and condensed. The condensate collected by the condenser C is sent to the condensate desalination device 5 by a condensate pump CP. Then, the condensed water that has been desalinated by the condensate desalination device 5 is pumped to the deaerator 7 via the low-pressure heater 6 by the condensate boost pump BP. The condensed water deaerated by the deaerator 7 is supplied to the superheater 3 (superheater tube T3) of the once-through boiler 2 via the high-pressure heater 8 and the water supply line FWL by the water supply pump FP.

Here, the steam power plant 1 is capable of extracting steam from the main steam line MSL and using it as a steam supply source while providing the original use such as power supply. For this reason, in the steam power plant 1, the bypass line VL is branched from the middle of the main steam line MSL connecting the superheater 3 of the once-through boiler 2 and the high-pressure turbine HT (steam turbine ST). The main steam line M
From the SL, a steam extraction line SEL is branched downstream of the branch of the bypass line VL (on the steam turbine ST side). The steam extraction line SEL is led to another facility using steam.

As shown in FIG. 1, the bypass line VL
Joins a low-temperature reheat line CRL for returning steam from the high-pressure turbine HT (steam turbine ST) to the reheater 4. In the bypass line VL, in order from the main steam line MSL side, a switching valve CV including a motor valve and the like,
A bypass flow rate adjustment valve FRV1 and a temperature reducer 9 are provided. Thus, if the main steam line MSL and the low temperature reheat line CRL are connected by the bypass line VL, and the switching valve CV and the bypass flow rate regulating valve FRV1 are opened, the steam flowing through the main steam line MSL is opened. Some will flow into the low temperature reheat line CRL via the desuperheater 9. Further, a thermometer T is provided downstream of the cooler 9 (on the side of the low-temperature reheating line CRL) on the bypass line VL.
The thermometer T measures the temperature of the steam flowing through the bypass line VL at the outlet of the desuperheater 9, and sends a signal indicating the measured value to the control device 10.

A spray line SPL is connected to a temperature reducer 9 provided in the bypass line VL via a nozzle N.
Are connected at one end. In spray line SPL,
A spray flow control valve FRV2 and a stop valve SV including a cylinder valve and the like are provided in order from the temperature reducer 9 side. And the other end of the spray line SPL is a water supply pump F
It is connected to the middle stage of P. Thereby, the stop valve SV
And the spray flow regulating valve FRV2 are opened,
Water is supplied from the water supply pump FP to the spray line SPL, and water is sprayed from the nozzle N into the temperature reducer 9. That is, the water supply pump FP, the spray line SPL, the stop valve S
V, the spray flow rate adjustment valve FRV2, and the like function as a water supply unit that supplies moisture to the steam in the bypass line VL.

The actuators of the switching valve CV, the bypass flow control valve FRV1, the spray flow control valve FRV2, and the stop valve SV are all connected to the control device 10 via a signal line, like the thermometer T. Have been. The control device 10 controls the switching valve CV and the bypass flow rate according to a normal operation mode when the steam power plant 1 is operated for an original purpose such as power supply and a bleed mode when steam is extracted from the main steam line MSL. It controls the valve FRV1, the spray flow regulating valve FRV2, and the stop valve SV.

More specifically, the control device 10 opens and closes the switching valve CV by an operation of the operator in both the normal operation mode and the bleeding mode. Further, a bypass flow control valve FRV1 is provided by an abnormality detection device (not shown).
, The switching valve CV is forcibly closed. Further, in the bleeding mode, the control device 10 controls the amount of water supplied to the once-through boiler 2 (superheater 3) and the steam extraction line SE.
L based on the amount of bleed air from L
1 is set, and a signal indicating the set opening is sent to the bypass flow rate regulating valve FRV1. Further, the control device 10
When the bleeding mode is stopped due to some abnormality or the like, the bypass flow rate regulating valve FRV1 is forcibly closed.

When the control device 10 opens the switching valve CV and the bypass flow control valve FRV1, it opens the spray flow control valve FRV2. Then, during the bleeding mode, the control device 10 controls the temperature reduction device 9 for the steam flowing through the bypass line VL based on the signal received from the thermometer T.
A control signal is sent to the spray flow control valve FRV2 such that the temperature at the outlet of the spray pressure control valve FRV2 is higher than the outlet temperature of the high-pressure turbine HT (the temperature of steam flowing through the low-temperature reheat line CRL) by a predetermined temperature (for example, + 5 ° C.). I do.

In addition, the control device 10 opens the spray flow rate adjusting valve FRV2 to open the spray line SPL.
The stop valve SV is opened, and the spray flow regulating valve FRV2 is opened.
Is completely closed, the stop valve SV is closed. Note that a monitoring thermometer (not shown) is provided in front of the junction of the bypass line VL and the low-temperature reheating line CRL, and the control device 10 controls the steam temperature measured by the monitoring thermometer, that is, When the temperature of the steam flowing into the low-temperature reheat line CRL becomes higher than the outlet temperature of the high-pressure turbine HT by, for example, 10 ° C., an alarm is issued, for example, 20
℃, switching valve CV, bypass flow control valve F
The bleeding mode is stopped by forcibly closing the RV1, the spray flow regulating valve FRV2, and the like.

The steam power plant 1 configured as described above
In the case where the steam is not extracted from the main steam line MSL via the steam extraction line SEL (normal operation mode), the switching valve CV, the bypass flow control valve FRV1, the spray flow control valve FRV2, and , All the stop valves SV are closed, and the bypass line VL is closed. Thereby, the steam power plant 1 can be operated without impairing the plant performance at all.

On the other hand, when steam is extracted from the main steam line MSL via the steam extraction line SEL (extraction mode)
First, the control device 10 opens the switching valve CV of the bypass line VL and the bypass flow rate adjustment valve FRV1. Thereby, a part of the steam superheated by the superheater 3 of the once-through boiler 2 is guided from the main steam line MSL to the low temperature reheat line CRL while the flow rate is adjusted by the bypass flow rate adjustment valve FRV1.

In the bleed mode, the controller 10 controls the spray flow rate adjusting valve FR of the spray line SPL.
V2 and the stop valve SV are opened. Then, the water extracted from the intermediate stage of the water supply pump FP is sprayed from the nozzle N into the temperature reducer 9 of the bypass line VL while the flow rate is adjusted by the spray flow rate adjustment valve FRV2. Thereby, the mist of water sprayed from the nozzle N takes heat from the steam in the desuperheater 9 and evaporates. As a result, moisture is supplied to the steam flowing from the main steam line MSL into the bypass line VL, and the amount of steam in the bypass line VL can be further increased. The main steam line MS
The temperature of the high-temperature steam from L can be reduced so as to approach the temperature of the steam flowing out of the high-pressure turbine HT.

As described above, in the bleed mode, the reheater 4 of the once-through boiler 2 includes the steam turbine ST (high-pressure turbine H).
In addition to the steam from T), steam from the bypass line VL will be introduced. As a result, the main steam line M
Due to the extraction of a large amount of steam from the SL, the steam turbine ST (high-pressure turbine HT) is connected to the low-temperature reheating line C
Even if the amount of steam flowing out to the RL is reduced, the amount of steam that satisfies the design conditions can be introduced into the reheater 4 of the once-through boiler 2.
It is possible to prevent the reheater tube T4 from being overheated. Thus, according to the steam power plant 1 of the present invention, steam can be extracted from the system without impairing the original plant performance.

[0027]

Since the steam power plant according to the present invention is configured as described above, the following effects can be obtained. That is, a main steam line connecting the superheater of the once-through boiler and the steam turbine is connected to a reheat line for returning steam from the steam turbine to the reheater by a bypass line, and water is supplied into the bypass line. With such a water supply means, a large amount of steam can be extracted from the system without impairing the original plant performance.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a steam power plant according to the present invention.

FIG. 2 is a system diagram showing a general steam power plant.

[Explanation of symbols]

1. Steam power plant, 2. Once-through boiler, 3. Superheater,
4 ... reheater, 9 ... cooler, 10 ... control device, CRL ... low temperature reheat line, CV ... switching valve, EG ... generator, FP ... feed water pump, FRV1 ... bypass flow rate adjustment valve, FRV2 ...
Spray flow control valve, HRL ... High temperature reheat line, HT ...
High-pressure turbine, IT: Medium-pressure turbine, LT: Low-pressure turbine, MSL: Main steam line, N: Nozzle, SEL: Steam extraction line, SPL: Spray line, ST: Steam turbine, SV: Stop valve, T: Thermometer, T3: superheater tube, T4: reheater tube, VL: bypass line.

Claims (1)

[Claims] 1. A steam power plant for driving a steam turbine with steam generated by a once-through boiler having a superheater and a reheater, comprising: a main steam line connecting the superheater and the steam turbine; A reheating line for returning steam to the reheater from a main line, a bypass line for guiding steam flowing through the main steam line to the reheating line, and a water supply unit for supplying moisture into the bypass line A steam power plant comprising: