JPS6237285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature reduction control device for a turbine bypass system, and in particular, controls the amount of water injected into a temperature reduction device installed in a turbine bypass path branched from a main steam system to a condenser. The present invention relates to a temperature reduction control device for a turbine bypass system.

In combined cycle power plants, general thermal power plants, and the like, temperature control is usually performed by adjusting the amount of water injected from a double water device into an attemperator provided in a turbine bypass system using a water injection control valve. In such a case, especially in a combined power generation plant or the like having high efficiency and high load responsiveness, it is necessary to quickly and accurately control the temperature in the attemperator. However, the response speed of conventional desuperheater temperature control is not necessarily sufficient, and the piping length to the condenser must be longer than necessary, making it difficult to use the limited plant area effectively. There were some drawbacks that made it difficult to utilize.

FIG. 1 shows an overview of a typical conventional turbine bypass system. The main steam flow from the boiler 1 is sent to the steam turbine ST (not shown) through the main steam pipe 2, while being branched from the main steam pipe 2 and passing through the desuperheater 4 under the flow rate adjustment by the turbine bypass valve 3. and is sent to the condenser 5. A portion of the feed water circulated from the condenser 5 to a drum (not shown) by a condensate pump 6 is injected into the attemperator 4 by a water injection control valve 7.

When controlling the temperature using the desuperheater 4,
The steam temperature in the pipe 10 that exits the desuperheater 4 and reaches the condenser 5 is detected, and a converted signal is sent to the control device 9 via the temperature transmitter 8. The control device 9 processes this signal and sends an opening command signal to the water injection control valve 7
The optimum temperature for the condenser 5 is obtained by adjusting the amount of water injected into the attemperator 4 according to the steam temperature at zero.

In this way, in the conventional system shown in Figure 1, the temperature of the attemperator 4 is directly controlled based on the temperature of the steam exiting the attemperator 4, but in such feedback control, so-called follow-up control is used. As a characteristic inherent in , the response is not quick. In addition, due to this slow response, there is a risk that high-temperature steam may flow into the condenser 5 without sufficient temperature reduction effect, so the piping 10 must have a large diameter and a long length with enough room. Problems arise with installation space. Furthermore, if the amount of water injected is set higher than necessary with safety in mind, the thermal effect will be reduced and energy loss will result.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and to provide a temperature reduction control device for a turbine bypass system that can quickly and accurately control the temperature.

The present invention provides a temperature reduction control device for a turbine bypass system, which adjusts the amount of water injected for temperature control into an attemperator provided in a turbine bypass path branched from a main steam system to a condenser. In,
The amount of water injected for temperature control into the attemperator is adjusted by a predictive control signal obtained based on detection and processing of information including temperature, pressure, and enthalpy factors of main steam upstream of the attemperator. Characterized by what has been done.

An embodiment of the present invention will be described in detail below based on the drawings.

FIG. 2 shows an embodiment in which the present invention is applied to a combined cycle power plant. The main steam flow from the boiler 1, which is heated by the exhaust gas of a gas turbine (not shown), is carried by a main steam pipe 2 to the steam turbine.
ST (not shown). In addition, a portion of the main steam is diverted at startup or when the steam turbine load fluctuates and is sent to the turbine bypass system to keep the main steam pressure and the level in the drum within acceptable values. That is, it is recovered to the condenser 5 via the turbine bypass valve 3 and the attemperator 4. The amount of main steam flowing into the attemperator 4 is adjusted by the opening degree of the turbine bypass valve 3. The temperature of the desuperheater 4 is controlled via a condenser 5, a condensate pump 6, and a deaerator (not shown).
This is done by means of a water injector using a water injection control valve 7 that bypasses the system going to the pipe 10, and the steam temperature in the pipe 10 is lowered to a necessary and sufficient level that can be recovered by the condenser 5. Each part of the plant system described above is basically the same as that shown in FIG. 1, and corresponding parts are designated by the same reference numerals.

Here, the configuration of the present invention for controlling the temperature in the desuperheater 4 will be described below. In the conventional method, the opening degree of the water injection control valve 7, which is adjusted for temperature control, is adjusted by detecting the steam temperature from the desuperheater 4, but in the embodiment of the present invention, Predicting the steam temperature on the exit side of the desuperheater based on information on thermal factors contained in the main steam on the upstream side before the temperature decreases, and adjusting the water injection control valve 7 based on this information. A control method is adopted.

That is, the temperature and pressure of the main steam in the main steam pipe 2 are detected and converted signals are sent to the temperature transmitter 11.
and is transmitted to the control device 9 by the pressure transmitter 12, and the control device 9 uses such a signal to predict the steam temperature on the outlet side of the desuperheater 4 and generate a correction signal to control it to an optimum value. It is transmitted to the turbine bypass valve 3 and the water injection control valve 7.

An outline of the signal processing performed by the control device 9 will be explained below with reference to the block diagram shown in FIG.

First, the signal T _M from the temperature transmitter 11 is converted into a temperature correction coefficient K ₂ in the function F ₁ calculator 13: (However, A is a constant) On the other hand, the signal P _M from the pressure transmitter 12 is converted into a pressure correction coefficient K ₃ in the function F ₂ calculator 14: K ₃ = P _M /B (However, B is a constant) Each of the above The coefficients K ₂ and K ₃ are multiplied in a multiplier X ₁ 15 to give the turbine bypass flow correction factor K ₄ : K ₄ = K ₂ × K ₃ while said temperature transmitter 11 and pressure transmitter 12
The signal from is also taken into the function _F3 calculator 16,
Here, the enthalpy of the superheated main steam is calculated and the enthalpy correction coefficient _K5 is obtained: _K5 = _F3 ( _PM , _TM ) This enthalpy correction coefficient _K5 is calculated by combining the flow rate correction coefficient _K4 and the multiplier X. ₂ is multiplied in 17 to calculate the turbine bypass steam correction coefficient K ₅ : K ₆ = K ₄ × K ₅ Furthermore, the control signal X ₅ from the turbine bypass controller 18 and the turbine bypass steam correction coefficient K ₆
The function F ₄ is calculated in the calculator 19 to calculate the control signal Y ₅ for turbine bypass correction: Y ₅ =F ₄ (X ₅ , X ₆ ) Based on this control signal Y 5, the function F ₄ is calculated. _F5 computing unit 20
A calculation for correcting the opening degree of the water injection control valve is performed inside to obtain a control signal Y ₁ : Y ₁ =F ₅ (Y ₅ ) The water injection control valve 7 is controlled by this control signal Y ₁ .

As described above, according to the embodiment of the present invention, the appropriate amount of water to be injected into the attemperator 4 is calculated by comprehensive correction based on various conditions such as heat, pressure, and enthalpy in the main steam. Therefore, temperature control of the condenser 5 can be optimized and plant thermal efficiency can be improved. In particular, this temperature control is performed as advance predictive control based on the state of the main steam on the upstream side, and its responsiveness is extremely high, making it possible to accurately follow the temperature reduction control at the time of plant startup or sudden load changes. can. As a result of the rapid and accurate temperature reduction control, the length, diameter, and wall thickness of the piping 10 from the desuperheater 4 to the condenser 5 are made larger than necessary for safety reasons. There is no need to do this, and great effects can be achieved in terms of reducing piping equipment and making effective use of installation space.

In the above embodiment, an example in which the present invention is applied to a combined cycle power plant has been described, but the present invention can also be widely applied to temperature reduction control in a general turbine bypass system.

As described above, the responsiveness of the temperature reduction control device for a turbine bypass system of the present invention can be made appropriate and quick.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a turbine bypass system to which a conventional device is applied, Fig. 2 is a system diagram of a turbine bypass system according to an embodiment of the present invention, and Fig. 3 is a block diagram of main parts of the embodiment shown in Fig. 2. . 1...Boiler, 2...Main steam pipe, 3...Turbine bypass valve, 4...Desuperheater, 5...Condenser, 7
... Water injection control valve, 9 ... Control device, 10 ... Piping, 11 ... Temperature transmitter, 12 ... Pressure transmitter.

Claims (1)

[Claims] 1. A temperature reduction control device for a turbine bypass system, which is configured to adjust the amount of water injected for temperature control to a desuperheater provided in a turbine bypass path branched from the main steam system and leading to a condenser. The amount of water injected into the attemperator for temperature control is adjusted by a predictive control signal obtained based on the detection and processing of information including temperature, pressure, and enthalpy factors of main steam on the upstream side of the attemperator. The temperature reduction control device for the turbine bypass system, characterized in that: