JPH06221112A - Turbine bypass valve control device - Google Patents

Abstract

PURPOSE:To obtain a turbine bypass valve control which can reduce thermal stress generated at the operation time of a turbine bypass line and prevents occurrence of damage such as crack. CONSTITUTION:A warming computer 27 is provided as a control device for a turbine bypass valve 19 in a combined cycle plant, which computer 27 perform warming of a turbine bypass line while minutely opening the turbine bypass valve 19 by the use of main steam pressure/temperature, gas turbine load falling and stoppage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a turbine bypass valve of a combined cycle plant.

[0002]

2. Description of the Related Art A combined cycle plant is composed of a gas turbine device, an exhaust heat recovery boiler that uses the heat of the gas turbine exhaust gas to generate steam, and a turbine device that is driven by steam from the exhaust heat recovery boiler. .

FIG. 4 shows a general structure of a combined cycle plant. The combined cycle plant is generally composed of one or a plurality of gas turbine apparatuses 1, and the same number of exhaust gas recovery boilers 7 and steam turbine apparatuses 14 as the gas turbine apparatuses 1.

The gas turbine system 1 includes a compressor 3,
A combustor 5 and a gas turbine 4, and a compressor 3
The air pressurized at is sent to the combustor 5. The combustor 5 combusts the pressurized air and fuel to generate high-pressure and high-temperature combustion gas.

The high-pressure and high-temperature combustion gas is sent to the gas turbine 4, and after driving the gas turbine 4, the exhaust heat recovery boiler 7
To the exhaust gas duct 6. Exhaust heat recovery boiler 7
Has a drum type boiler structure, and multiple drums are installed depending on the plant output.

The waste heat recovery boiler 7 is composed of a economizer 8, a steam generating drum 9, an evaporator 10 and a superheater 11 for heating the feed water supplied by the feed water pump 17, and the feed water is supplied to the gas turbine 4
Is heated and vaporized by the exhaust gas after driving. This steam is
It is supplied to a steam turbine 14 via a steam pipe 12 and a regulator valve 13. As a result, the steam turbine 14 and the generator 15 are driven.

Exhaust gas from the steam turbine 14 is collected in a condenser 16 and is heat-exchanged with circulating water having seawater as cooling water to be condensed. This condensed water is boosted by the water supply pump 17 and is supplied to the exhaust heat recovery boiler 7 via the water supply control valve 18. Steam pipe 12
A bypass line in which a turbine bypass valve 19 is installed is branched and is connected to the condenser 16 via a temperature reducing device 20. A spray water line branched from a water supply pump 17 line is connected to the temperature reducing device 20, and a cooling water spray control valve 21 is installed. The gas turbine device is characterized in that it has a shorter start / stop time and is more resistant to load fluctuation than the conventional steam turbine device.

For this reason, in actual operation, quick load follow-up including start / stop is performed for day and night power demand. This causes the turbine bypass line to operate frequently. For example, at the time of start-up, the steam pressure on the steam turbine 14 side and the steam pressure generated in the steam generating drum 22 are mismatched, and this mismatch is released to the condenser 16 through the turbine bypass line. The same is true when stopping.

During normal operation, the turbine bypass line is isolated from the steam line by fully closing the turbine bypass valve 19, and the temperature of the turbine bypass is lowered. Especially after the secondary side of the turbine bypass valve, the pressure inside the condenser 16 has dropped to around the saturation temperature. When suddenly introducing high pressure and high temperature steam into such a line,
Generates large thermal stress. Further, the increased frequency of use of the turbine bypass line increases the life consumption of the metal material.

[0010]

However, the frequent use of the turbine bypass line leaves the following problems. When high-pressure high-temperature steam is discharged from the turbine bypass line to the condenser at once when the load drops or stops, if large thermal stress occurs and the frequency increases, the life consumption of the metal material increases,
Damage such as cracks occurs in the turbine bypass valve.

[0011]

According to the present invention, the turbine bypass valve is slightly opened by a steam turbine stop signal, and the opening degree of the minute opening is calculated by the main steam pressure and the main steam temperature. Warming to reduce the generation of thermal stress when using the turbine bypass line.

[0012]

According to the present invention, the thermal stress of the turbine bypass line generated when the load is dropped or stopped can be reduced by warming the entire line in advance. As a result, the life of the metal material such as the turbine bypass valve is reduced, and damage such as cracks can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, the same symbols as those in FIG. 4 indicate the same or corresponding portions. A signal from the main steam pressure detector 22 that detects the main steam pressure and a signal from the main steam temperature detector 26 that detects the main steam temperature are input to the warming calculator 27. In the warming calculator 27, the turbine bypass valve 19 is slightly opened by the gas turbine load drop signal, and warming of the turbine bypass line is started. The fine opening degree of the turbine bypass valve 19 is determined from the main steam pressure temperature.

FIG. 2 shows the configuration of the warming computing unit 27 for reducing the thermal stress of the turbine bypass line generated when the load is lowered or stopped in the control device configured as described above. The main steam pressure signal and the main steam temperature signal are input to the steam flow rate calculator 30 in the warming calculator 27. The steam temperature calculator 30 is preliminarily input with the transient temperature characteristics determined from the material, structure, etc. of the turbine bypass valve 19, and the steam flow rate at which the thermal stress is minimized is calculated from the main steam pressure and the main steam temperature.

The steam flow rate signal is input to the valve opening calculator 31, where the required valve opening is calculated. Specifically, it is calculated from the main steam pressure, the flow rate, and the valve flow rate coefficient. This signal is sent to the proportional-integral calculator of the turbine bypass valve 19 via the switch 28.
It is input to the addition / subtraction calculator 29 installed on the output side of 23.

The switching unit 28 adjusts the output of the warming calculator 27 to the output side of the proportional-plus-integral calculator according to the gas turbine load drop or the stop signal output from the main controller of the gas turbine system 1. Switch to input to.
As a result, the turbine bypass line is properly warmed, and damage such as cracks due to thermal stress can be prevented.

In this description, the process of stopping the combined cycle plant has been mainly described, but the same effect can be obtained in the process of increasing the load of the combined cycle plant starting from the start of the gas turbine.

In the above description, the output of the warming arithmetic unit is output to the addition / subtraction arithmetic unit via the switching unit, but the same effect can be obtained as a signal selector as another method. The signal selector compares the output of the warming calculator with the output of the proportional-plus-integral calculator and preferentially outputs the turbine bypass valve open signal.

Another embodiment will be described with reference to FIG. The main steam pressure detector is used as the steam flow calculator 29 of the warming calculator 27.
22 and other turbine bypass valve 19 for temperature detector 26 signal
The metal temperature detector 32 of is input. The transient temperature characteristic of the turbine bypass valve 19 is calculated in consideration of the temperature during operation of the turbine bypass line, and the steam flow rate at which the thermal stress is minimized is obtained. Subsequent calculations are the same as those described above, and will be omitted.

In the description of FIG. 3, the output of the warming computing unit is output to the addition / subtraction computing unit via the switching unit, but as another method, the same effect can be obtained in the configuration as in the above description. The turbine bypass device includes another type of steam conversion valve in which decompression and temperature reduction are integrated, but the present invention is also effective in this device.

[0022]

As described above, according to the present invention, the thermal stress generated during the operation of the turbine bypass line can be reduced and damage such as cracks can be prevented.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a warming calculator according to the present invention.

FIG. 3 is a block diagram showing another example of the warming arithmetic unit according to the present invention.

FIG. 4 is a system diagram of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gas turbine device, 2 ... Generator, 3 ... Compressor, 4 ... Gas turbine, 5 ... Combustor, 6 ... Exhaust gas duct, 7 ... Exhaust heat recovery boiler, 8 ... Economizer, 9 ... Evaporation drum, 10 ... Evaporator, 11 ... Superheater, 12 ... Steam pipe, 13 ... Regulator, 14 ... Steam turbine, 15 ... Generator, 16 ... Condenser, 17 ...
Water supply pump, 18 ... Water supply control valve, 19 ... Turbine bypass valve, 20 ... Valve temperature device, 21 ... Cooling water spray control valve, 22 ... Main steam pressure detector, 23 ... Proportional-integral calculator, 24 ... Temperature detector, 25 ... Proportional-integral calculator, 26 ... Main steam temperature detector, 27 ...
Warming computing unit, 28 ... Switching unit, 29 ... Adjustment computing unit, 30
… Steam flow calculator, 31… Valve opening calculator.

Claims (2)

[Claims] 1. A turbine bypass valve control device in a combined cycle plant, comprising a warming computing unit for warming a turbine bypass line by slightly opening a turbine bypass valve when a main steam pressure temperature and a gas turbine load drop or stop occur. A turbine bypass valve control device characterized by the above. 2. A turbine bypass valve control device, wherein the turbine bypass valve metal temperature is further input to the warming computing unit to calculate transient characteristics of the valve body methane temperature during operation of the turbine bypass line.