JPS6242127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry heater for a thermal power plant, and more particularly to a method and apparatus for detecting leakage of feed water from a dry heater of an ultra-supercritical thermal power plant.

The water supply system of the currently proposed ultra-supercritical thermal power plant will be explained with reference to FIG.

Figure 1 shows a portion of a thermal power plant. In this figure, 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 an intermediate pressure turbine 3 and a high pressure turbine 2. The temperature is raised by each high-pressure feed water heater 6. After that, the pressure is further increased by the boost pump 7, and then the water is introduced to the dry heater 9, where the temperature is raised, through the ultra-high pressure feed water heater 8, which is heated by the extracted steam from the ultra-high pressure turbine 1. 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 is intended to recover heat and 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 the steam extracted from the high pressure turbine 2 and passed through the dry heater 9 is used as a heating source for the high pressure feed water heater 6 as shown in FIG.
The extracted steam at the outlet of the dry heater 9 must be in a superheated steam state. If a tube leak or the like occurs in the dry heater 9 and a portion of the feed water flows into the bleed steam, and the bleed steam at the outlet of the dry heater 9 becomes wet steam, the dry heater 9 will be transferred to the high pressure feed water heater 6. There is a risk that the bleed steam piping and the heat transfer tubes of the high-pressure feed water heater 6 may be damaged by erosion due to water droplets in the wet steam. Therefore, early detection of tube leaks in the dry heater 9 is important in order to prevent equipment damage.

An object of the present invention is to provide a dry heater leak detection method and apparatus that make it possible to reliably detect a tube leak in a dry heater installed in a feedwater heater system of a thermal power plant.

A feature of the present invention is that a pressure detector and a temperature sensor are attached to the bleed steam piping at the outlet of the dry heater, and the bleed steam at the dry heater outlet is adjusted based on the pressure and temperature signals of the bleed steam from these detectors. The purpose is to determine whether it is wet steam or not, and to detect tube leaks in the dry heater at an early stage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a leak detection technique for a dry heater of an ultra-supercritical thermal power plant, which is an embodiment of the present invention, will be described with reference to the drawings.

FIG. 2 shows only the system around the dry heater 9 in the ultra-supercritical thermal power plant shown in FIG. In FIG. 2, extracted steam from the high pressure steam turbine 2 is led to the dry heater 9 through the dry heater inlet extracted steam pipe 11,
After the feed water is heated there, it flows into the high pressure feed water heater 8 through the dry heater outlet bleed steam pipe 12. In the bleed system, a pressure detector 13 and a temperature detector 14 are installed at the dry heater outlet bleed steam pipe 12.
Set up each. Detection signals from these two detectors 13 and 14 are input to a leak detector 15.

Next, the function of the leak detector 15 is shown in FIG. The pressure signal P of extracted steam detected from the pressure detector 13 is input to the saturated steam enthalpy calculator 16 provided in the leak detector 15, where the saturated steam enthalpy i'' corresponding to the pressure is calculated. The pressure signal P from the pressure detector 13 and the temperature signal T from the temperature sensor 14 are input to the enthalpy calculator 17, where the enthalpy i of the extracted steam at the outlet of the dry heater 9 is calculated.Then, the steam state is determined. In the device 18, the saturated steam enthalpy obtained by these two computing devices 16 and 17 is
i'' is compared with the dry heater outlet steam enthalpy i, and the determination is made as follows.

(1) If i>i″+α, it is superheated steam.(2) If i″+α>i>i″−α, it may be wet steam.(3) If i<i″−α, it is wet steam. Here, α is a set value.

This is because if a tube leak occurs in the dry heater 9, the bleed steam at the outlet of the dry heater becomes wet steam due to the leaked feed water, so the enthalpy i'' of the bleed steam at the dry heater outlet is This can be determined from the fact that it is larger than the enthalpy i of saturated steam.And,
Based on the above determination result, the steam state discriminator 18 outputs an operation signal for displaying or controlling the steam state.

In other words, in the steam state discriminator 18, the above 1, 2,
The display device 16 determines the case 3 and displays the vapor state.
to be displayed. Further, in the case of the above-mentioned discrimination results 2 and 3, the operation signal e may be outputted to operate the mist separator or the bleed steam stop valve as shown in FIGS. 4 and 5.

Next, an embodiment to which the leak detector 15 of the present invention is applied will be described with reference to FIG. In order to bleed the dry heater outlet steam as shown in FIG. The mist inside is separated. The steam from which the mist has been separated is returned from the mist separator 21 to the dry heater outlet bleed steam pipe 12 through a steam return pipe 22 having a control valve 32. On the other hand, the mist separated by the mist separator 21 is discharged to the outside through a drain pipe 23 having a control valve 33. Here, if the steam state discriminator 18 of the leak detector 15 shown in FIG.
5, the control valve 31 attached to the steam extraction pipe 20 and the control valve 32 attached to the steam return pipe 22 are fully opened for a certain period of time, and then fully closed.
Then, after these two controls 31 and 32 are fully closed, by opening the control valve 33 attached to the drain pipe 23, it is possible to check whether mist is generated, that is, check for a tube leak in the dry heater. I can do it.

Next, another embodiment to which the leak detector 15 of the present invention is applied will be described with reference to FIG. In FIG. 5, in this embodiment, when the leak detector 15 determines that the extracted steam at the outlet of the dry heater 9 is wet steam, the leakage between the high pressure turbine 2 and the dry heater 9 is determined based on the operation signal e. The operation of the dry heater 9 is stopped by fully closing the bleed steam stop valve 30 attached to the dry heater inlet bleed steam pipe 11.

According to the embodiment of the present invention, leakage of feed water in the dry heater can be detected early, so that the high pressure feed water heater uses steam from the bleed steam pipe at the outlet of the dry heater or the steam from the bleed steam pipe at the outlet of the dry heater as a heating source. This makes it possible to prevent heat transfer tubes from being damaged by erosion due to water droplets in wet steam generated by tube leaks in dry heaters, thereby improving the reliability of power plants.

As explained above, according to the present invention, it is possible to reliably detect a tube leak in a dry heater installed in a feed water heater system of a thermal power plant.

[Brief explanation of the drawing]

Fig. 1 is a water supply system diagram of an ultra-supercritical pressure plant to which the present invention is applied, Fig. 2 is a dry heater heating system diagram showing an embodiment of the present invention, and is equipped with a dry heater leak detector. FIG. 2 is a block diagram showing details of the leak detector, and FIGS. 4 and 5 are dry heater heating system diagrams illustrating an application example of the present invention. 1...Ultra high pressure turbine, 2...High pressure turbine,
3... Medium pressure turbine, 4... Deaerator, 5... Water pump, 6... High pressure feed water heater, 7... Boost pump, 8... Ultra high pressure feed water heater, 9... Dry heater, 11 ...Dry heater inlet bleed steam piping, 1
2...Dry heater outlet extraction steam piping, 13...
Pressure detector, 14... Temperature detector, 15... Leak detection device, 16... Saturated steam enthalpy calculator, 17... Enthalpy calculator, 18... Steam state discriminator, 20... Steam extraction piping, 21 ...Mist separator, 22...Steam return piping, 23...
Drain extraction piping, 30...Bleed steam stop valve.

Claims (1)

[Claims] 1. A dry heater that uses extracted steam from a steam turbine as heating steam and heats feed water with the sensible heat of the extracted steam, and a feed water heater that heats the feed water with the latent heat of the extracted steam after heating the feed water. In a dry heater of a thermal power plant equipped with A method for detecting a leak in a dry heater, characterized in that saturated steam enthalpy is calculated from a signal, and the state of extracted steam passing through a dry heater is determined based on a comparison of both enthalpies. 2 A system is equipped with an extraction steam piping that guides extraction steam from the steam turbine, a dry heater that heats the supply water with the extraction steam guided through the extraction steam piping, and a feed water heater that heats the supply water with the extraction steam that has passed through the dry heater. In the dry heater of a thermal power plant, a temperature detection device and a pressure detection device are installed in the bleed steam piping from the dry heater to the feed water heater, and further, based on the temperature signal and pressure signal of the bleed steam from both of these detection devices, a first calculation means for calculating the enthalpy of the extracted steam that has passed through the dry heater; a second calculation means for calculating the saturated steam enthalpy based on the pressure signal; 1. A leak detection device for a dry heater, comprising a detection device having a determination means for determining the state of extracted steam based on a comparison of both obtained enthalpies.