JPH076608B2 - Reheat steam temperature controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal power plant having a high-pressure turbine bypass and a low-pressure turbine bypass, and particularly to a reheat steam temperature at the time of cold start to match the intermediate-pressure turbine rotor metal temperature as much as possible. The present invention relates to a reheat steam temperature control device that can be operated.

[Background of the Invention]

Conventionally, the reheat temperature control method at start-up of a thermal power plant having a high-pressure turbine bypass and a low-pressure turbine bypass is such that the steam passing through the high-pressure turbine bypass is guided to the condenser via the reheater bypass valve to allow the reheater to flow into It is known that the temperature of the reheated steam is quickly raised by increasing or decreasing the amount of steam. (JP-A-56-56504, JP-A-56-1)
However, the provision of the reheater bypass valve complicates the system configuration and increases the equipment, and therefore it is difficult to adopt the one known in practice.

In a thermal power plant that does not have a reheater bypass but has only a high-pressure turbine bypass and a low-pressure bypass, when the turbine is stopped for a long time and the turbine rotor metal temperature is cooled to near the ambient temperature, the boiler is started. Since it is necessary to perform boiler boosting operation and high-pressure turbine warm-up operation after ignition and before venting the turbine, it takes a considerable amount of time.
As a result, the reheat steam temperature becomes too high compared to the medium pressure turbine rotor metal temperature, causing a problem that unacceptable thermal stress occurs in the medium pressure turbine rotor metal immediately after ventilation.

[Object of the Invention]

An object of the present invention is to provide a reheated steam temperature control device capable of matching the reheated steam that is easily overheated at the time of starting the cold machine to the medium pressure turbine rotor metal temperature as much as possible.

[Outline of Invention]

In order to achieve such an object, the present invention provides a high-pressure turbine bypass in order to reduce the thermal stress due to so-called positive mismatch, in which the reheat steam temperature is higher than the intermediate-pressure turbine rotor metal temperature during ventilation of the intermediate-pressure turbine. Outlet steam and reheater desuperheater The outlet steam is prevented from becoming wet, and the steam temperature is adjusted by adjusting the high pressure turbine bypass spray valve and reheater spray valve with the medium pressure turbine rotor metal temperature. The metal temperature is matched as much as possible.

Example of Invention

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a boiler steam generator, 2 is a superheater, 4 is a high-pressure turbine to which high-temperature high-pressure steam is supplied from a superheater 2 through a main steam pipe 3, and 5 is an inlet side pipe of a reheater 6. A low-temperature reheat pipe, 8 is a medium-pressure turbine to which reheat steam is supplied from the reheater 6 through the high-temperature reheat pipe 7, and 9 is a condenser, which forms a main flow path of steam. Reference numeral 10 is a pipeline that connects the main steam pipe 3 and the low temperature reheat pipe 5 via a high pressure turbine bypass valve 11, and 12 is a high pressure turbine bypass spray that supplies spray water to the high pressure turbine bypass valve 11 to reduce the temperature of the main steam. It is a valve. Reference numeral 14 is a reheater spray valve that supplies spray water to the reheater desuperheater 13 to deheat the reheated steam. Further, reference numeral 15 is a pipe line connecting the high temperature reheat pipe 7 and the condenser 9 via a low pressure turbine bypass valve 16. Further, 17 is a rotor metal temperature detector of the intermediate pressure turbine 8 (actually, a reheat steam inner wall metal temperature detector), 18 is a reheat steam temperature detector, 19 is a high temperature reheat pipe steam pressure detector, and 20 is Low temperature reheat pipe steam pressure detector, 21 is reheater desuperheater outlet steam temperature detector,
22 is a high temperature bypass outlet steam temperature detector.

FIG. 2 is a block diagram showing an embodiment of the control device according to the present invention.

Reference numeral 23 is a function generator that generates a reheat steam ventilation temperature target value 24 based on the medium pressure turbine rotor metal temperature detected by the detector 17 and the high temperature reheat pipe steam pressure detected by the detector 19.

Here, a conceptual diagram of the function generator 23 is shown in FIG. Third
In the figure, the horizontal axis shows the medium-pressure turbine rotor metal temperature, and the vertical axis shows the reheat steam ventilation temperature target value 24.The target value 24 is the temperature of the medium-pressure turbine rotor metal with the hot reheat pipe steam pressure as another parameter. A value (the value at which the reheat steam chamber steam temperature matches the metal temperature) is given.

Next, in FIG. 2, reference numeral 25 is a signal switch, and the input signal 24 is selected before ventilation of the intermediate pressure turbine and the input signal 29 is selected after ventilation of the intermediate pressure turbine. The signal 29 is the reheated steam temperature set value after ventilation, and is generated by a combination of the reheated steam temperature final (rated) target set value 26, the reheated steam temperature change rate setter 27 and the change rate limiter 28.

Therefore, before the medium-pressure turbine ventilation, the deviation signal 30 between the reheat steam temperature detected by the detector 18 and the reheat steam ventilation temperature target value 24 selected by the signal switch 25, that is, the mismatch amount A corresponding control signal 32 is output from the controller 31, which causes the reheater spray valve 14 to open and close. In this case, if excessive spray water is injected into the reheater desuperheater 13, the reheater desuperheater outlet steam may become wet.
Therefore, the low-temperature reheat pipe vapor pressure is detected by the detector 20, and adjustment is performed according to the deviation between the saturation temperature limit signal 34 generated by the function generator 33 and the reheater desuperheater outlet detected by the detector 21. The signal 36 is output by the controller 35, and the signal on the low side of the control signal 32, which is the output of the controller 31, is the low value selector 37.
Selected in. As a result, the amount of mismatch between the intermediate pressure turbine rotor metal temperature and the reheat steam temperature can be minimized without the outlet steam of the reheater desuperheater becoming below the saturation temperature.

Further, an embodiment of a control device which lowers the inlet steam temperature of the reheater 6 by using the high pressure turbine bypass spray valve 12 to facilitate the matching of the intermediate pressure turbine rotor metal temperature and the reheat steam temperature is shown in FIG. Show.

38 is the high pressure turbine bypass outlet temperature reference setting signal 39 due to the medium pressure turbine rotor metal temperature detected by the detector 17.
Is a function generator for generating. Reference numeral 40 is a function generator that generates a correction signal 41 according to the mismatch amount 30.

Here, FIG. 4 shows a conceptual diagram of the function generator 38, and FIG. 5 shows a conceptual diagram of the function generator 40. In Fig. 4, the horizontal axis shows the medium-pressure turbine rotor metal temperature, and the vertical axis shows the high-pressure turbine bypass outlet temperature reference set value 39. The reheat steam temperature cannot be uniquely determined only by the reheater inlet temperature. The values are characteristic values based on operation results. In FIG. 5, the horizontal axis shows the mismatch amount 30 and the vertical axis shows the correction signal 41. When the mismatch amount 30 is positive, the correction signal 41 becomes negative, in order to prevent interference with the reheater spray valve control. It has a dead zone.

Next, in FIG. 2, an addition signal 42 of the high-pressure turbine bypass outlet temperature reference setting signal 39 and the correction signal 41 is the output of the high-pressure turbine that is the output of the signal generator 43 provided to prevent overheating of the high-pressure turbine bypass outlet pipe. The low value selector 45 selects a signal having a lower value from the bypass outlet temperature maximum setting signal 44. Further, the saturation temperature limit signal 34 generated by the function generator 33 or the output signal of the low value selector 45, whichever is the higher value is selected by the high value selector 46, and the final high pressure turbine bypass outlet temperature is selected. The set value is 47. Adjustment signal according to the deviation signal between the high pressure turbine bypass outlet temperature detected by the detector 22 and the set value 47
49 is output from the controller 48, which opens and closes the high-pressure turbine bypass spray valve 12.

Therefore, when the mismatch amount 30 is in the dead zone, the high-pressure turbine bypass outlet temperature does not exceed the maximum value or fall below the saturation temperature, and control is performed by the medium-pressure turbine rotor metal temperature. Also, if the mismatch amount 30 exceeds the dead zone, for example, the mismatch amount
If 30 becomes excessively positive, the high pressure turbine bypass outlet temperature can be controlled to be lower by the correction signal 41 without again becoming below the saturation temperature.

〔The invention's effect〕

As is clear from the above description, according to the present invention, it is possible for the medium-pressure turbine rotor while preventing the high-pressure turbine bypass outlet and the reheater desuperheater outlet steam from becoming wet. Since the reheated steam having the optimum temperature in the range can be supplied, it has an effect of reducing the thermal stress of the intermediate pressure turbine rotor.

[Brief description of drawings]

1 is a piping system diagram of a thermal power plant having a turbine bypass system to which the present invention is applied, FIG. 2 is a control block diagram showing an embodiment of a reheat steam temperature control device according to the present invention, FIG. 3, FIG. 4 and 5 are conceptual diagrams of the function generators designated by reference numerals 23, 38 and 40 in FIG. 2, respectively. 1 ... Boiler steam generator, 4 ... High-pressure turbine, 6 ...
Reheater, 8 ... Medium pressure turbine, 11 ... High pressure turbine bypass valve, 12 ... High pressure turbine bypass spray valve, 13 ...
… Reheater desuperheater, 14 …… Reheater spray valve, 17 …… Medium pressure turbine rotor metal detector, 23,33,38,40 …… Function generator, 31,35,48 …… Controller , 37,45 …… Low price selector, 46
...... High price selector.

Claims (2)

[Claims] 1. A high pressure turbine bypass system for bypassing a high pressure turbine, a low temperature reheat steam system for guiding the high pressure turbine exhaust steam and the high pressure turbine bypass steam to a reheater, and the reheat having a reheater spray. Of high temperature reheat steam that guides the reheated steam obtained in the reactor to the intermediate pressure turbine, and low pressure turbine bypass system that bypasses the medium and low pressure turbine to the reheated steam to the condenser, turbine plant In the reheat steam temperature control device, it is used in the process of creating ventilation conditions while flowing steam through the high pressure turbine bypass system and the low pressure turbine bypass system, and detects to match the intermediate pressure turbine rotor metal temperature with the reheat steam temperature. For controlling the reheater spray valve according to the reheater temperature target value determined by the intermediate pressure turbine rotor metal temperature and the reheat steam pressure The reheat steam temperature control device, characterized in that provided. 2. A high pressure turbine bypass system for bypassing a high pressure turbine, a low temperature reheat steam system for guiding the high pressure turbine exhaust steam and the high pressure turbine bypass steam to a reheater, and the reheat having a reheater spray. Of high temperature reheat steam that guides the reheated steam obtained in the reactor to the intermediate pressure turbine, and low pressure turbine bypass system that bypasses the medium and low pressure turbine to the reheated steam to the condenser, turbine plant In the reheat steam temperature control device, it is used in the process of creating ventilation conditions while flowing steam through the high pressure turbine bypass system and the low pressure turbine bypass system, and matches the intermediate pressure turbine rotor metal temperature with the reheat steam temperature. ,
High-pressure turbine bypass outlet temperature temperature determined by the detected medium-pressure turbine rotor metal temperature and the high-pressure turbine bypass outlet temperature obtained by adding the correction value determined by the amount of mismatch between the medium-pressure turbine rotor metal temperature and the reheat steam temperature. A reheat steam temperature control device comprising means for controlling a high pressure turbine bypass spray valve according to a deviation between a set value and a high pressure turbine bypass outlet temperature measurement value.