JPS6153411A - Steam pressure controlling apparatus - Google Patents

Abstract

PURPOSE:To prevent a chimney from heat fatigue by comparing gas temperature at an outlet of a steam generator with a specified value to open a low pressure bypass valve for increasing temperature drop of exhaust gas when said gas temperature departs from the specified value. CONSTITUTION:In a combined cycle plant having high and low bypass systems, the above-mentioned steam pressure controlling apparatus is provided with high and low steam pressure controlling systems 20, 40 respectively for controlling high and low bypass valves 17, 18. In this case, the low steam pressure controlling system 40 is provided with a relay coil 44 energized by the output of a comparator 44 when gas temperature at an outlet of a steam generator detected by a temperature detector 41 exceeds a specified value set by a temperature setter 42. The energizing force of the relay coil 44 changes over a relay contact 44a to the control setter (pressure setter) 45 side the output of which is supplied to the input of a deflector 33. The low pressure bypass valve 18 is constituted to be operated in the open direction through an adjuster 34 by the output of the deflector 33.

Description

[Detailed Description of the Invention] This embodiment is explained as an example applied to a combined cycle plant having the same configuration as shown in Fig. 2, and the same members as in Fig. 3 are given the same reference numerals. However, detailed explanation will be omitted.

In FIG. 1, the configuration of the high pressure steam pressure control system 20 is as follows.
It is exactly the same as the case shown in the figure.

The low-pressure steam pressure control system 40 includes a temperature detector 41 that detects the outlet gas temperature of the steam generator, and a temperature setting device that sets the specified 1 shift below the maximum allowable gas temperature necessary to prevent thermal fatigue of the chimney. device 42, this setting device and the temperature detector 4
1, and a relay coil 44 that is energized when the output of the comparator exceeds a certain value.

31 is a pressure setting device (normal setting device) for setting the pressure of the low-pressure steam pressure control system during normal operation of the steam turbine, and 45 is a pressure setting device for setting a lower pressure. It is a setting device (suppression setting device).

When the outlet gas temperature of the steam generator is below the specified value, the relay contact 44a is normally connected to the setting device 31, but
When the above specified value is exceeded, the relay coil 44 is energized,
The relay contact 44a is switched to the suppression setting device 45 side.

The outputs of these pressure setting devices 31.45 are connected to relay contacts 44.
One of them is selected by a and input to the deviation device 33 together with the output of the pressure detector 32. When the deviation signal output from the deviation device exceeds a predetermined range, the regulator 34 is activated to adjust the opening degree of the low pressure bypass valve 18.

The operation of the steam pressure control device of the present invention configured as described above is the same as that described with reference to FIG. 3 when the exhaust gas temperature at the outlet of the steam generator is below a predetermined temperature.

On the other hand, when the steam generator outlet gas temperature rises above the specified value, the relay coil 44 is activated! relay contact 4/
Ia is switched, and the output J of the suppression setting device 45 is set to the deviation device 33.
is input.

As described above, this suppression setter 45 is set to a lower pressure 110 than the normal setter 41, so the regulator 34 prevents the low pressure bypass valve 18 from operating in the opening direction. In addition, the amount of steam produced and discharged from the low-pressure drum increases, and the water supply port to the low-pressure drum also increases, so the amount of heat exchanged and discharged from the steam generator increases, and the amount of water supplied to the low-pressure drum also increases. As the temperature increases, the heat exchanger VA load in the steam generator increases, and the outlet gas temperature of the steam generator decreases.

As described above, in the steam pressure control device of the present invention, when the outlet gas temperature of the steam generator exceeds a preset temperature, the 17i1 degree of the low pressure bypass valve 18 is automatically increased to reduce the heat inside the steam generator. By increasing the exchange layer, the steam generator outlet gas temperature decreases. Therefore, the risk of deterioration of the chimney due to thermal fatigue is significantly reduced.

In the above explanation, two setting devices with different set values, the normal setting device 31 and the suppression setting device 45, are installed in the low-pressure steam pressure control system, and their outputs are switched according to the output of the comparator 43. Although an example has been described in which the low pressure bypass valve 18 is controlled in the opening direction, the present invention is not limited to this, and when the output of the comparator 43 exceeds a specified value, the low pressure bypass valve 18 is controlled directly through the interface. Almost the same effect can be obtained even if the valve is opened by locking.

In addition, in FIG. 1, a relay coil 44 is used as a switch.
Although an example has been described in which relay contacts 4 and 4a are used, it goes without saying that this switch can be replaced with 1q control rectifying elements made of various semiconductors.

[Effects of the Invention] As described above, according to the present invention, the temperature of the output gas from the steam generator can be maintained below a preset specified temperature, so that the chimney is kept at a high temperature for a long time and is not heated. It is possible to prevent deterioration and improve the reliability of the plant.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a steam pressure control device showing an embodiment of the present invention, Fig. 2 is a system diagram of a combined cycle plant to which the present invention is applied, and Fig. 3 is a system diagram of a conventional steam pressure control device. be. 1...Gas turbine 2...11 Hot exhaust gas 3...Steam generator 4...Superheated Container 5...N-pressure evaporator 6...High-pressure economizer 7...Low-pressure evaporator 8... ...Low pressure economizer 9...Low humidity exhaust gas 10...Chimney 11...Low pressure drum 12... ...Low pressure regulator 13...Steam turbine 14...High pressure drum 15...High pressure regulator 16...・・Condenser 17・・・・・・・＾Pressure bypass valve 18・・・・
......Low pressure bypass valve 20......High pressure steam pressure control system 21......External command 30.40...Low pressure steam pressure control system agent Patent Attorney Sa Suyama - Figure 1 Figure 2

Claims (2)

[Claims] (1) The exhaust gas of the gas turbine is passed through a steam generator to generate high-pressure steam and low-pressure steam, and then released from the chimney, and the high-pressure steam and low-pressure steam are transferred to a high-pressure steam control valve and a low-pressure steam control valve, respectively. In a combined cycle plant, the high pressure steam control valve or the low pressure steam control valve and the high pressure steam control valve and the high pressure bypass valve or the low pressure bypass valve that bypass the steam turbine are introduced into the condenser. is provided with a high-pressure steam pressure control system that adjusts the opening degree of the high-pressure bypass valve based on the deviation between a pressure setting device with a variable setting value and a pressure detector, and the low-pressure bypass valve is provided with a A steam pressure control device comprising a low pressure steam pressure control system that controls the low pressure bypass valve in the opening direction when the outlet gas temperature exceeds a set value. (2) The low-pressure steam pressure control system includes a temperature detector that detects the outlet gas temperature of the steam generator, a switch that performs a switching operation when the output of this temperature detector exceeds a set temperature, and a steam turbine. There is a pressure setting device (hereinafter referred to as a normal setting device) that sets the pressure of the low-pressure steam pressure control system during normal operation, and a pressure setting device that sets a pressure lower than this normal setting device (hereinafter referred to as a suppression setting device). ), a deviation device for determining the deviation between the output of either the normal setting device or the suppression setting device selected by the switching device and the output of the pressure detector;
The steam pressure control device according to claim 1, further comprising a regulator that adjusts the opening degree of the low pressure bypass valve based on the output of the deviation device.