JPS61171810A - Control of steam turbine plant - Google Patents

Abstract

PURPOSE:To prevent droppage of steam pressure at the inlet of steam turbine due to excessive extraction by controlling a pressure regulation valve for feeding the steam to the outside of system through the pressure signal at the inlet of steam turbine and the auxiliary steam pressure signal. CONSTITUTION:A pressure transmitter 39 is provided for the steam of steam turbine 45. A pressure transmitter 38 will detect the pressure of auxiliary steam 42. An operator 62 will normally control the pressure regulation valve 33 on the basis of the signals from the pressure transmitter 38 and a setting level transmitter 61. Upon droppage of steam pressure 45 of steam turbine, the operator 62 will control the pressure regulation valve 33 while taking priority of the signal from a setting level transmitter 66. Consequently, the extraction of auxiliary steam 42 is reduced to recover the pressure of the steam of steam turbine 45, resulting in prevention of steam pressure droppage at the inlet of steam turbine.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a combined plant of a gas turbine and a steam turbine, and particularly relates to an auxiliary steam supply method, and an auxiliary steam control suitable for good plant operation. Regarding the method.

[Background of the invention]

Combined Plant Ha, Thermal and Nuclear Power Generation Magazine, Vol.
35, JI65 (Sho 56-12), when a gas turbine and a steam turbine are directly connected via a generator and are a single-shaft type, the shaft output is generally 100 M
W to 150MW, 600MW to 10
A 100O class combined plant has a configuration with 6 or 7 axes.

Figure 3 shows the overall configuration of the combined plant.

Gas turbine 1 sucks in atmospheric air 11, burns fuel 12, and drives generator 2. The exhaust gas 13 of the gas turbine is introduced into the exhaust heat recovery boiler 3, where its heat is recovered, and the feed water 44 sent by the water supply pump 35 is introduced into the exhaust heat recovery boiler 3, and as it passes through the exhaust heat recovery boiler 3, Exhaust gas 13
Steam 41 is generated by heat exchange with 41 tons of steam! , is introduced into the steam turbine 31 and drives the generator 2t. Further, a portion of the steam 41 is used for various purposes as auxiliary steam 42 via the pressure regulating valve 33. The auxiliary steam 42 is regulated to a constant pressure by the pressure regulating valve 33 in response to a signal from the pressure transmitter 3B, and is passed through the steam turbine gland steam regulator 37t to the gland sealing steam of the steam turbine 31 and the thermal desorption of the condenser 34. Along with being used for the steam 36, it is also introduced into the common auxiliary steam header 51 via the auxiliary steam communication pipe 443, and is used for each of the above-mentioned purposes as an auxiliary steam source when starting up other combined plants. .

FIG. 4 shows the characteristics of the shaft load and the pressure of steam 41 in a conventional combined plant.

The combined plant was published in Thermal and Nuclear Power Generation Magazine Vol.
As described in 33-A5, the pressure of the steam 41 is changed according to the plant load, and variable pressure operation is performed without throttling the steam control valve 32t of the steam turbine 31. This is because, as is generally known, the gas turbine exhaust gas temperature decreases during partial load.
This is to improve the plant thermal efficiency by changing the pressure. Therefore, as shown in FIG. 4, the pressure of the steam 41 has a characteristic that changes linearly with the shaft load.

On the other hand, the steam 41 generated from the exhaust heat recovery boiler 3 is
It is used as the auxiliary steam 42 through the pressure control valve 33 for the gland section sealing steam 37 of the steam turbine 31 and the heated deaeration steam 36 of the condenser 34. It is supplied via the auxiliary steam header 51 as an auxiliary steam source when starting up the combined plant of other shafts.

At this time, depending on the amount of auxiliary steam supplied to the other shafts, if a large amount of steam is extracted, that is, the steam 41 does not pass through the steam turbine 31 and flows through the auxiliary steam communication pipe 43 and the common auxiliary steam header 51. If a large amount of steam 41 is supplied outside the system, the pressure of the steam 41 will drop significantly. For this reason,
As shown in FIG. 5, there is a supply limit to the auxiliary steam 42,
It is necessary to take this into consideration when supplying auxiliary steam.

[Purpose of the invention]

The purpose of the present invention is to solve the drawbacks of the prior art as described above.
An object of the present invention is to provide an auxiliary steam control system suitable for solving the above problems and improving the drop in steam pressure at the inlet of a steam turbine due to excessive extraction of auxiliary steam.

[Summary of the invention]

For the above purpose, a pressure transmitter 39 is installed in the steam turbine steam 45 as shown in FIG. If the pressure decreases, the steam turbine steam 4
5 pressure was detected and the amount of air extracted by the auxiliary steam 42 was improved.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 3 and FIG. 1.

In FIG. 3, in the plant, the gas turbine 1 and the steam turbine 31 are operated at the rated load, the exhaust gas 13 from the gas turbine 1 is introduced into the exhaust heat recovery boiler 3, where the heat is recovered, and the feed water 44 is It is heated to become steam at about 60 atmospheres and is introduced into the steam turbine 31. Also steam 4
1, a part of the solenoid is supplied to the auxiliary steam 42 through the pressure regulating valve 33.
used for various purposes. The pressure transmitter 38 detects the pressure of the auxiliary steam 42, and based on the signal, the pressure regulating valve 33 performs afterpressure control to maintain the pressure of the auxiliary steam 42 at approximately 15 atmospheres.

FIG. 1 shows the characteristics of the shaft load, the normal pressure of the steam turbine steam 45, and the allowable minimum pressure of the single-shaft base compounding plant according to the present invention.

In FIG. 3, when the pressure of the steam turbine steam 45 decreases due to the auxiliary steam 42 extracted from the steam 41, that is, when the amount of extracted air of the auxiliary steam 42 becomes excessive, the pressure of the steam turbine steam 45 decreases significantly. cause. At this time, the pressure of the steam turbine steam 45 is detected by the pressure transmitter 39, and as shown in FIG.
The characteristics of the shaft load, the pressure of the steam turbine steam 45, and the minimum allowable steam pressure of the steam turbine are compared. As a result, the steam turbine steam pressure detected by the pressure transmitter 39 is below the minimum allowable steam pressure of the steam turbine at the shaft load during operation as shown in FIG.

If so, the amount of auxiliary steam 42 extracted from the steam 41 is excessive, causing a pressure drop in the steam turbine steam 4 and 5, which has an adverse effect on the steam turbine 31.

In order to improve this, that is, in order to restore the pressure of the steam turbine steam 45 to a level higher than the minimum allowable steam turbine steam pressure allowed by the steam turbine 31, the auxiliary steam 42, which is the cause of the pressure drop in the steam turbine steam 45, is extracted. It is necessary to reduce the amount.

At this time, the pressure regulating valve 3 is performing after-pressure control to keep the pressure of the auxiliary steam 42 constant according to the signal from the pressure detector 38.
31! -1 The opening degree of the pressure regulating valve 33 is narrowed down by giving priority to the low pressure signal of the pressure transmitter 39 installed in the steam turbine steam 45, thereby reducing the flow rate of the auxiliary steam 42,
The pressure of the steam turbine steam 45 can be restored to ensure the lowest pressure allowed by the steam turbine 31.

FIG. 2 shows an example of a control system for realizing Mizumoto Meikin.

As shown in FIG. 2, the pressure transmitter 3B detects the pressure of the auxiliary steam 42 extracted from the steam 41 through the pressure regulating valve 33, and calculates the pressure of the auxiliary steam 42 to be constant using the set value transmitter 61. The pressure signal of the steam turbine steam 45 from the pressure transmitter 39 and the shaft load are sent to the computing unit 65. Using the shaft load signal from the signal transmitter 64, as shown in FIG. 1, the relationship between the shaft load, the pressure of the steam turbine steam 45, and the minimum allowable pressure of the steam turbine is calculated. As a result, if the pressure of the steam turbine steam 45 is below the steam turbine allowable minimum pressure, that is, if the pressure of the steam turbine steam 45 is reduced by the auxiliary steam 420 overflow bleed from the steam 41, the setting A low pressure signal of the steam turbine 45 is transmitted from the value transmitter 66 to the calculator 62 . The computing unit 62 normally receives signals from the pressure transmitter 38 and the set value transmitter 61.
Pressure regulating valve 33t - auxiliary steam 42 via signal converter 63
The pressure is controlled to be constant at approximately 15 atm.
If the aforementioned low pressure signal of the steam turbine steam 45 is transmitted from the set value transmitter 66, the arithmetic unit 62
gives priority to the signal from the set value transmitter 66 over the signal from the set value transmitter 61, transmits the control signal to the signal converter 63, and controls the pressure regulating valve 33f. That is, the pressure regulating valve 33 is normally controlled so that the pressure of the auxiliary steam 42 is constant, but when the auxiliary steam 42 is extracted from the steam 41 in an excessive amount and the pressure of the steam turbine steam 45 decreases, , the amount of extracted air of the auxiliary steam 42 is reduced to reduce the amount of extracted air of the auxiliary steam 42 from the steam 41, and the pressure of the steam turbine steam 45 is restored. Of course, the calculator 62 prioritizes the signal from the setpoint transmitter 66 until the pressure of the steam turbine steam 45 is restored and the low pressure signal from the setpoint transmitter 66 is eliminated.

This prevents the pressure of the steam turbine steam 45 from falling below the allowable minimum pressure of the steam turbine due to excessive extraction of the auxiliary steam 42 extracted from the steam 41, and prevents the pressure of the auxiliary steam 42 from becoming lower than the allowable minimum pressure of the steam turbine. It is possible to prevent air bleed.

In the present invention, a decrease in steam pressure of the steam turbine is detected by detecting the steam pressure of the steam turbine, but the auxiliary steam 42
, or install a flow rate measuring device in the auxiliary steam communication pipe 43,
A similar effect can be obtained by a method in which the pressure drop in the steam turbine steam 45 is determined by directly monitoring the amount of auxiliary steam extracted from the steam 41.

〔Effect of the invention〕

According to the present invention, it is possible to prevent a decrease in the steam turbine inlet steam pressure due to excessive extraction of auxiliary steam.

(9) In a power generation plant in which a -shaft type compound plant is constituted by a plurality of shafts, other shafts can be started and stopped without adversely affecting the operating shaft.

Furthermore, by simply improving the control method, the above objectives can be achieved without a significant increase in cost.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of shaft load and steam turbine allowable minimum pressure in an embodiment of the present invention, Fig. 2 is a control system configuration diagram, and Fig. 3 is a combined plant configuration diagram for explaining the conventional method. FIG. 4 is a characteristic diagram of conventional shaft load and steam turbine steam pressure, and FIG. 5 is a conventional characteristic diagram of shaft load and supplyable auxiliary steam amount. 1... Gas turbine, 3... Exhaust heat recovery boiler, 31
...Steam turbine, 41...Steam, 45...Steam turbine also 1's θ -p What 7IQ thread 2nd surface Fig. 24

Claims (1)

[Claims] 1. In a power generation plant equipped with a steam turbine driven by steam generated by a steam generator, and a pipe connecting the steam generator and the steam turbine, a part of the steam is supplied to the outside of the system. A pressure detection device is provided in a part of the piping that connects the steam generator and the steam turbine, and a pressure detection device is also provided in a part of the piping that supplies the steam to the outside of the system, and the steam is removed from the system by signals from both. A method for controlling a steam turbine plant, which is characterized by controlling a pressure control device installed in the middle of a pipe that supplies water.