JPH0549884B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention is directed to a thermal power plant equipped with a dry heater, particularly in a dry heater of an ultra-supercritical pressure thermal power plant. This relates to a control device that prevents steam from forming.

[Background of the invention]

Figure 1 shows an example of a water supply system diagram for a recently proposed ultra-supercritical thermal power plant.

In FIG. 1, feed water sent from a low-pressure feed water heater (not shown) passes through a deaerator 4, is pressurized by a feed water pump 5, and is then heated by extracted steam from a hollow turbine 3 and a high-pressure turbine 2. The temperature is raised by each high-pressure feed water heater 8. Thereafter, the pressure is further increased by a boost pump 7, and then the water is heated through an ultra-high pressure feed water heater 6 heated by extracted steam from the ultra-high pressure turbine 1, and then introduced to a dry heater 9. The supplied water is further heated by this dry heater 9 and then supplied to a boiler (not shown).

The dry heater 9 is a feed water heater specific to the feed water heater system of an ultra-supercritical thermal power plant, and the installation of this dry heater 9 recovers heat to improve the thermal efficiency of the plant. The function of this dry heater 9 is to heat the feed water using superheated steam, which is extracted steam from the high-pressure turbine 2, but the extracted steam that has heated the feed water and lowered its temperature is also drawn out from the dry heater 9 in the state of superheated steam. be done. In this way, this differs from a normal feedwater heater in that the extracted steam does not condense within the vessel, unlike in a normal feedwater heater.

Here, when extracted steam from the high-pressure turbine 2 and passed through the dry heater 9 is used as a heating source for the high-pressure feedwater heater 6 as shown in FIG. 1, the extracted steam at the outlet of the dry heater 9 is always Must be in superheated steam state. If the bleed steam supplied to the dry heater 9 or the high-pressure feed water heater 8 becomes wet steam, the bleed steam piping from the dry heater 9 to the high-pressure feed water heater 6 or the high-pressure feed water heater 6
There is a risk that the heat transfer tubes may be damaged by erosion due to water droplets in the wet steam.

As mentioned above, the reason why the extracted steam turns into wet steam is that a tube leak occurs in the dry heater 9 and a part of the supplied water flows into the extracted steam, and the extracted steam at the outlet of the dry heater 9 turns into wet steam. In some cases, the extracted steam at the outlet of the dry heater 9 becomes wet steam due to overcooling of the dry heater due to a delay in raising the temperature of the feed water when each feed water heater is in service (when ventilation of extracted steam starts). There is.

Even when these causes occur, it is important to prevent the bleed steam led from the dry heater to the feedwater heater from turning into wet steam.

[Purpose of the invention]

An object of the present invention is to provide a control device for a dry heater system that can prevent extracted steam led from a dry heater to a feedwater heater from turning into wet steam and improve plant reliability.

[Summary of the invention]

In order to achieve the above object, the dry heater system control device of the present invention includes a dry heater that heats feed water using extracted steam from a steam turbine, and a dry heater that heats the feed water using extracted steam that flows through the dry heater. In a dry heater for a power generation plant equipped with a feed water heater, a bleed steam bypass system bypasses the bleed steam that should flow through the dry heater, and a feed water bypass system bypasses the feed water that should flow through the dry heater. a flow rate control valve is provided in at least one of the extraction steam bypass system and the water supply bypass system, and
A temperature detector and a pressure detector are provided in the bleed steam outflow line of the dry heater, and a controller is provided which receives output signals from the two detectors and controls opening and closing of the flow rate regulating valve. shall be.

[Embodiments of the invention]

A dry heater system and its control device for an ultra-supercritical thermal power plant, which is an embodiment of the present invention, will be explained based on the drawings.

FIG. 2 shows an embodiment in which the present invention is applied to a system around the dry heater 9 in the ultra-supercritical thermal power plant shown in FIG. In FIG. 2, the extracted steam from the high-pressure steam turbine 2 is led to the dry heater 9 through the dry heater inlet bleed steam pipe 21, heats the feed water here, and then passes through the dry heater outlet bleed steam pipe 22 to the high pressure water supply. The inlet bleed steam pipe 21 flows into the heater 8
is provided with a bleed steam stop valve 11, which is opened and closed when the dry heater and feedwater heater are started (heater-in service) or stopped according to the operation of the plant. The bleed steam bypass system of the present invention includes a bleed steam bypass pipe 23 connecting the dry heater inlet bleed steam pipe 21 and the dry heater outlet bleed steam pipe 22, and a steam amount control valve 24 provided in the bypass pipe 23. configured. In addition, a pressure detector 26 and a temperature detector 2 are installed at the high-pressure feed water heater inlet bleed steam piping 25 that guides the bleed steam to the high-pressure feed water heater 8.
7 and 7 respectively. Detection signals from these two detectors 26 and 27 are input to a controller 28 provided to control the steam amount control valve 24.

FIG. 3 is a block diagram showing one example of a specific configuration of the controller 28.

The controller 28 includes a calculator 30 that calculates a saturation temperature signal 31 corresponding to the pressure of the extracted steam flowing into the feed water heater 8 based on a signal 29 from the pressure detector 26, an arithmetic unit 33 that receives the signal output 32 of the temperature detector 27 and calculates a temperature difference signal 34 between the detected temperature and the saturation temperature; a temperature difference setter 35; and an output signal of the temperature difference setter 35. 36 and a proportional-integral calculator 38 which inputs the temperature difference signal 34 and provides a valve operation signal 39 to the steam amount control valve 24 so as to perform optimum steam amount control.

Next, the functions and operating methods of the controller 28 shown in FIG. 3 and the extraction steam bypass system shown in FIG. 2 will be explained.

For example, a tube leak occurs in the dry heater 9 and part of the supplied water flows into the extracted steam,
When the extracted steam at the outlet of the dry heater 9 becomes wet steam, the signal output 32 from the steam temperature detector 27
and a saturation temperature signal 3 calculated by the arithmetic unit 30 based on the signal output 29 from the pressure detector 25.
1 indicates the same value. In other words, the feed water heater 8
It is detected that the extracted steam introduced into the chamber has turned into wet steam. At this time, the proportional-integral calculator 38 adjusts the steam amount control valve 24 so that the deviation between the signal output 34 from the temperature difference calculator 33 and the signal output 36 from the temperature difference setter 35 becomes zero. is controlled, the temperature difference setting device 3
5, the temperature detection signal 31 is set to be higher than the saturation temperature signal 31, the control valve 24 opens, and a portion of the high temperature bleed steam is directly transferred from the steam pipe 21 to the bleed steam. tube 22
bypass to heat the leaked water supply,
It can prevent it from becoming wet steam.

For example, when each feed water heater is in service (when ventilation of extracted steam starts), if the extracted steam at the outlet of the dry heater 9 becomes wet steam due to overcooling of the dry heater due to a delay in raising the temperature of the supplied water, That is, when the feed water temperature of the dry heater 9 becomes higher than the feed water temperature of the feed water heater 8, the steam side pressure in the dry heater 9 is higher than or almost the same as the steam side pressure in the feed water heater 8. Because of the pressure,
The extracted steam introduced into the dry heater 9 is cooled more than necessary (supercooled) and is already inside the dry heater.
In the case where the steam is turned into wet steam (condensation), the bypass system and control device of the present invention operate in exactly the same way as in the case of draining with a tube leak as described above, and bypass the high-temperature bleed steam by the necessary amount. At the same time, by reducing the amount of wet steam, it is possible to prevent the extracted steam introduced into the feed water heater 8 from turning into wet steam (condensation).

FIG. 4 shows an embodiment of the water supply bypass system of the present invention, which includes a water supply bypass pipe 40 connecting the water supply inlet pipe 15 and the water supply outlet pipe 16 of the dry heater 9, and It is constituted by a water supply amount control valve 41 provided. Further, a pressure detector 26 and a temperature detector 27 are installed in the high-pressure feed water heater inlet bleed steam piping 25 that guides the bleed steam to the high-pressure feed water heater 8, respectively. and,
Detection signals from these two detectors 26 and 27 are input to a controller 42 that controls the water supply amount control valve 41. This controller 42 is configured in exactly the same way as the controller 28 described above, and has the same functions. When the feed water bypass system configured in this manner is used, the extracted steam introduced into the dry heater 9 is cooled more than necessary (supercooling), such as when the feed water heater is in service.
When the extracted steam at the outlet of the dry heater 9 becomes wet steam, the controller 42 operates in exactly the same manner as the controller 28 in the extracted steam bypass system described above, and the water supply amount control valve 41 controls the amount of water required. By bypassing the feed water, reducing the heat load within the dry heater 9 and increasing the outlet temperature of the extracted steam, it is possible to prevent the extracted steam introduced into the feed water heater 8 from becoming wet vapor. Furthermore, since the degree of superheating of the outlet steam can be indirectly controlled by the temperature difference setting device 35, it is also possible to correct the imbalance in the heat load between the dry heater and the feed water heater.

FIG. 5 shows an example in which both a water supply bypass system and an extraction steam bypass system are provided.
FIG. 6 is a block diagram showing the configuration of the control device. Those systems and control devices with the same drawing reference numbers as in Figures 2 to 4 are as follows:
They are the same or similar components. Using the dry heater bypass system configured in this way,
In addition to the functions and effects of each bypass system described above, a dry heater cut can be operated. Furthermore, by adjusting the setting device 35 of the controller 45, in addition to controlling the feed water bypass amount, wet vaporization is prevented by controlling the extraction steam amount bypass amount, which has the advantage of increasing the control range and control amount. .

〔Effect of the invention〕

As described in detail above, the dry heater system control device of the present invention includes a dry heater that heats feed water using extracted steam from a steam turbine, and a dry heater that heats the feed water using extracted steam that has passed through the dry heater. A dry heater for a power generation plant equipped with a feed water heater includes at least an bleed steam bypass system that bypasses the bleed steam that should flow through the dry heater, and a feed water bypass system that bypasses the feed water that should flow through the dry heater. At least one of the bleed steam bypass system and the water supply bypass system is provided with a flow rate control valve, and the bleed steam outflow pipe of the dry heater is provided with a temperature detector and a pressure detector. By providing a controller that receives the output signals of the two detectors and controls the opening and closing of the flow rate regulating valve, it is possible to prevent the extracted steam led from the dry heater to the feed water heater from turning into wet steam. This greatly contributes to improving the reliability of the entire plant.

[Brief explanation of the drawing]

Fig. 1 is a water supply system diagram of an ultra-supercritical pressure plant that is the object of the present invention, Fig. 2 is a system diagram showing a dry heater bleed steam bypass system and its control device, which is an embodiment of the present invention, and Fig. 3 is a block diagram showing details of the control device shown in FIG. 2, FIG. 4 is a system diagram showing a dry heater water supply bypass system and its control device according to an embodiment of the present invention, and fifth and sixth are system diagrams showing the control device. The figures show an embodiment different from the above, with FIG. 5 being an extraction steam bypass system diagram and FIG. 6 being a block diagram. 1...Ultra high pressure turbine, 2...High pressure turbine,
3... Medium pressure turbine, 4... Deaerator, 5... Water pump, 6... Ultra high pressure feed water heater, 7... Boost pump, 8... High pressure feed water heater, 9... Dry heater, 11 ... Bleeding stop valve, 15, 16... Water supply piping, 21, 22, 25... Bleeding steam piping, 23...
...Extraction steam bypass piping, 24, 41...Control valve, 26...Pressure detector, 27...Temperature detector,
28, 42, 45...Controller, 30, 33, 38
...Calculator, 35...Setting device, 40...Water supply bypass piping.

Claims (1)

[Claims] 1. A dry power generation plant equipped with a dry heater that heats feed water using extracted steam from a steam turbine, and a feed water heater that heats the feed water using extracted steam that has passed through the dry heater. In the heater, an bleed steam bypass system that bypasses the bleed steam to be passed through the dry heater, and
At least one of a water supply bypass system for bypassing the water supply to be distributed through the dry heater is provided, and at least one of the bleed steam bypass system and the water supply bypass system is provided with a flow rate control valve, and the dry heater is provided with a flow rate control valve. A power generation plant, characterized in that a temperature detector and a pressure detector are provided in the bleed steam outflow pipe, and a controller is provided for controlling the opening and closing of the flow rate regulating valve based on the output signals of the two detectors. control device for the dry heater system. 2. The controller includes a computing unit that calculates the saturated steam temperature corresponding to the pressure of the extracted steam detected by the pressure detector, and an output signal of the computing unit and the extracted steam detected by the temperature detector. a computing unit that calculates the degree of superheating of the extracted steam based on the temperature of the computing unit, and a flow rate regulator that controls the opening degree of the flow rate regulating valve based on the degree of superheating calculated by the computing unit, Claim 1, characterized in that the flow control valve is controlled to open and close so that the extracted steam supplied from the dry heater to the feed water heater does not turn into wet steam. A control device for the dry heater system of a power generation plant.