JP3650277B2 - Thermal power plant control device and thermal power plant control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal power plant control device and a thermal power plant control method, and more particularly to a thermal power plant control device and a control method for controlling a main steam control valve to close when a steam pressure in a steam supply system is lowered. Is.
[0002]
[Prior art]
Conventionally, this type of thermal power plant generally includes a main steam supply system having a steam control valve for adjusting the amount of main steam supplied, and a steam turbine driven by the main steam from the main steam supply system. In general, when the pressure of the main steam supply system drops to a predetermined value during the load operation, the steam control valve is normally closed to a valve opening corresponding to no load.
[0003]
In other words, when the main steam pressure rises or falls during load operation, or when the main steam pressure is kept constant, for some reason, such as when the amount of fuel input on the boiler side is insufficient, or when an abnormality occurs in the pressure control system, etc. However, when the main steam pressure decreases to a certain pressure, for example, 90% of the rated main steam pressure, the main steam control valve starts to be narrowed at this point. The main steam control valve is narrowed down to 80% of the rated main steam pressure, that is, to a pressure equivalent to no load of the main steam pressure.
[0004]
FIG. 4 schematically shows the plant configuration, in which 13 is a drum boiler, 6, 8 and 21 are steam turbines, and 5 is a main steam control valve. The main steam is supplied from the main steam supply system provided with the drum boiler 13 to the steam turbine through the supply pipe 4 and the main steam control valve 5, and the turbine is driven.
[0005]
In this case, a temperature detector 10 and a pressure detector 11 are installed in the main steam pipe 4 serving as a steam supply path from the boiler 13 to the high-pressure steam turbine 6, and the pressure value of the main steam is the pressure detector. 11 and detected by the control circuit (valve control device) 12. The main steam control valve 5 is controlled by the control signal processed by the control circuit 12. That is, when the pressure of the main steam supply system decreases to a predetermined value, the control device 12 controls the closing operation of the steam control valve to a valve opening corresponding to no load.
[0006]
FIG. 5 is a schematic logic of the control device 12 at this time. When the main steam pressure is reduced to A% of the main steam pressure, for example, 90% in the function generator 31, B% of the main steam pressure, for example, 80%, which indicates the main steam control valve opening corresponding to no load, but so far, the signal for narrowing the main steam control valve is output from 100 to 0%. This output signal is passed through the calculator 32, and the calculator 32 sets the rate of change, etc., and is sent as a control signal to the main steam control valve via the high value selection circuit 33. Of course, the lower limit value is also input to the high value selection circuit 33, and the upper limit selection circuit 33 is limited so as not to reduce the lower limit value.
[0007]
In this case, as shown in FIG. 6 as an example of the characteristic of the main steam pressure corresponding to the plant load, the main steam pressure varies depending on the plant load. Therefore, the function generator is based on the pressure corresponding to the load. 31 is assembled.
[0008]
On the other hand, the temperature of the main steam generated in the drum boiler 13 is adjusted by a temperature reducer 16 provided in the boiler. That is, the temperature of the main steam is detected by the temperature detector 10, and the temperature control valve 15 is operated based on the detected value to adjust the spray flow rate to the temperature reducer 16 so that the temperature becomes a constant temperature. .
[0009]
[Problems to be solved by the invention]
When the main steam pressure of a drum boiler drops due to some factor in a thermal power plant configured in this way, an abnormality on the boiler side is detected by detecting the abnormality on the boiler side with the main steam pressure and narrowing down the main steam control valve. However, in this conventional plant configuration, there is no particular problem on the boiler side, but on the turbine side, when the main steam pressure of the boiler is reduced, the main steam The temperature also decreases, and this temperature decrease may cause rapid cooling of component metals constituting the turbine, which may adversely affect the components.
[0010]
In other words, as described above, the main feature of the drum boiler is that the main steam pressure is controlled by increasing or decreasing the fuel, and the main steam temperature is controlled by the spray flow rate to the temperature reducer 16 provided at the outlet of the primary superheater 2. Done by adjustment. Accordingly, when the main steam pressure is reduced due to a decrease in the amount of fuel or misfiring of the fuel burner 14 or the like in the plant employing this drum boiler, the drum 1 has a heat capacity. Decreases with a time delay and does not decrease rapidly, and there is a possibility that the metal parts constituting the steam turbine may be adversely affected by heat.
[0011]
The present invention has been made in view of this, and the object thereof is to prevent adverse effects on the metal parts constituting the steam turbine even if the main steam supply system pressure drop occurs during plant operation. And it is providing the control apparatus of the thermal power plant which can aim at the expansion of a continuous operation.
[0012]
[Means for Solving the Problems]
That is, the present invention relates to a main steam supply system having a drum-type boiler, a steam turbine driven by main steam from the main steam supply system, and a steam adjustment mode which is provided in the steam supply system and adjusts the supply amount of main steam. Control of a thermal power plant comprising a valve and a control device that controls the closing operation of the steam control valve to a valve opening corresponding to no load when the pressure of the main steam supply system drops to a predetermined value In the apparatus, when the main steam pressure drops to the predetermined value, the main steam temperature value is taken into the valve control device, and when the temperature value is less than the predetermined value, the main steam control valve is closed. Means for starting the operation is provided to achieve the intended purpose.
[0013]
The present invention also provides a main steam supply system having a drum-type boiler, a steam turbine driven by the main steam from the main steam supply system, and a steam control unit provided in the steam supply system for adjusting the supply amount of the main steam. And a control device that controls the closing operation of the steam control valve to a valve opening corresponding to no load when the pressure of the main steam supplied to the steam turbine is reduced to a predetermined value. In the thermal power plant control device, the valve control device is provided with means for taking in the temperature value of the main steam and starting the closing operation of the main steam control valve when the temperature value is equal to or lower than a predetermined value. It is what I did.
[0014]
In addition, when the main steam pressure supplied from the main steam supply system to the steam turbine drops to a predetermined value, the main steam control valve of the main steam supply system is closed to a valve opening corresponding to no load. In the control method, when the temperature of the main steam supplied to the steam turbine is taken in during operation of the plant, and the pressure of the main steam is reduced to the predetermined value, the temperature value of the main steam is predetermined. When the value is less than or equal to the value, the closing operation of the main steam control valve is started.
[0015]
In addition, when the main steam pressure supplied from the main steam supply system to the steam turbine drops to a predetermined value, the main steam control valve of the main steam supply system is closed to a valve opening corresponding to no load. In this control method, the temperature of the main steam supplied to the steam turbine is monitored when the pressure of the main steam drops to a predetermined value during operation of the plant, and when the main steam temperature is equal to or higher than the predetermined value, the main steam is monitored. The throttle signal of the steam control valve is blocked.
[0016]
In addition, when the main steam pressure supplied from the main steam supply system to the steam turbine drops to a predetermined value, the main steam control valve of the main steam supply system is closed to a valve opening corresponding to no load. In this control method, during operation of the plant, the temperature value of the main steam supplied to the steam turbine is captured, and when the captured temperature value is equal to or less than a predetermined value, the closing operation of the main steam control valve is started. It is what I did.
[0017]
That is, in the case of a thermal power plant formed in this way, the valve controller that controls the opening / closing operation of the steam control valve takes in the temperature value of the main steam when the pressure of the main steam drops to the predetermined value, When this temperature value is less than a predetermined value, the means for starting the closing operation of the main steam control valve, that is, the main steam control valve narrowing signal is blocked if the main steam temperature is a predetermined value or more. Therefore, the main steam control valve starts to be closed after the main steam temperature is lowered to some extent, and there is no thermal adverse effect on the metal parts constituting the steam turbine. In addition, it is possible to prevent the main steam control valve from immediately starting to be throttled only by lowering the main steam pressure, and if recovery of the main steam pressure can be expected during that time, it can also contribute to the continuation of plant operation, and expansion of continuation of operation Can be achieved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the illustrated embodiments. FIG. 1 is a diagram showing the outline of the configuration of the thermal power plant. 13 is a drum boiler, 6, 8 and 21 are steam turbines (high pressure, medium pressure, low pressure), 5 is a main steam control valve, 22 is a condenser, 25 is a deaerator, and 50 is a generator. . Reference numeral 14 denotes a fuel burner as a boiler heating source.
[0019]
First, an outline of the operation of the plant will be described with reference to this figure. The main steam is supplied from the main steam supply system including the drum boiler 13, the superheaters 2 and 3, and the main steam pipe 4 through the main steam control valve 5. Supplied to the turbine. That is, the steam generated in the drum 1 of the boiler is superheated by the primary superheater 2 and the secondary superheater 3, and is guided to the high-pressure steam turbine 6 through the main steam pipe 4 and the main steam control valve 5. The steam that has passed through the high-pressure steam turbine is reheated by the reheater 7 and enters the intermediate-pressure steam turbine 8, and the steam that has passed through the intermediate-pressure steam turbine enters the low-pressure steam turbine 21 and is condensed in the condenser 22.
[0020]
The condensate condensed in the condenser 22 is increased in pressure by the condensate pump 23 and led to the deaerator 25 through the low-pressure feed water heater 24. The condensate deaerated by the deaerator 25 is pressurized by a feed water pump 26, heated by a high-pressure feed water heater 27, returned to the boiler 13 through a feed water flow rate adjustment valve 28, passed through a economizer 29, and the drum 1. To be supplied with water.
[0021]
The temperature of the main steam generated in the boiler 13 is adjusted by a temperature reducer 16 provided in the boiler. That is, the temperature of the main steam is detected by the temperature detector 10, and based on this detected value, the temperature control valve 15 is operated to control the spray flow rate to the temperature reducer 16 so as to reach a constant temperature.
[0022]
The main steam whose temperature is controlled in this way is supplied to the high pressure steam turbine 6. A detector 11 is installed, and the pressure value of the main steam is detected by the pressure detector 11 and taken into a control circuit (valve control device) 12. The main steam control valve 5 is controlled by the control signal processed by the control circuit 12. That is, when the pressure of the main steam supply system decreases to a predetermined value, the steam control valve is controlled to close to a valve opening corresponding to no load.
[0023]
In this case, the control circuit 12 is provided with the following means. That is, when the main steam pressure drops to a predetermined value, the control circuit 12 takes in the temperature value of the main steam, and starts the closing operation of the main steam control valve when the temperature is lower than the predetermined value. To do.
[0024]
That is, as shown in the diagram of FIG. 1 (b), the main steam temperature is monitored, and when the main steam pressure drops to a predetermined value, the main steam temperature value is taken in. The subtractor 36 compares the fetched temperature value with a predetermined value, and it is determined by the monitor relay 37. When the temperature value falls below the predetermined value, the switch 34 closes the main steam control valve closing operation start signal. Is sent.
[0025]
In this case, the temperature of the predetermined value serving as a reference varies depending on the plant load, but the steam flowing into the turbine has a sufficient degree of superheat, and is set by a limit value for preventing rapid cooling of the turbine metal. . That is, as an example is shown in FIG. 3, since it changes depending on the load of the plant, it is set by the function generator 35 corresponding to this. Note that the switching device 34 normally inputs a maximum value of 100% from the setting device 38 and outputs it from b to c in the figure, and outputs from a to c when the main steam temperature falls below a predetermined value.
[0026]
According to this embodiment, even if the main steam pressure drop occurs during operation, the main steam control valve is not controlled to be closed regardless of the main steam temperature, and the metal parts constituting the steam turbine are heated. If the main steam pressure adjustment valve can be expected to recover during that time, the plant operation can be continued. Can also contribute.
[0027]
FIG. 2 shows another embodiment of the present invention. In this embodiment, when the main steam temperature further falls below a predetermined value, the main steam control valve is throttled by the preceding control even when the main steam pressure is not lowered by a predetermined amount.
[0028]
That is, in the case of a drum-type boiler, the malfunction of the spray control can be considered as a cause of the decrease in the main steam temperature. In this case, the main steam temperature can be decreased without decreasing the main steam pressure. Therefore, as a countermeasure for such a case, a function generator 41 is separately provided downstream of the subtracter 36, and when the main steam temperature becomes c ° C., for example, 10 ° C. or less from a predetermined value, the main steam control valve is output to be throttled. A signal is output. That is, a control signal is output to the main steam control valve by the low value selection circuit 43 via the calculator 42.
[0029]
In this embodiment, the effects of the above embodiment, that is, the metal parts constituting the steam turbine are not adversely affected by heat, and it is further protected against a decrease in the main steam temperature. It is possible to improve the performance.
[0030]
Regarding the decrease in main steam temperature, there are some plants that trip the turbine at a low main steam temperature as a turbine protection. However, in the embodiment of the present invention, the main steam control valve is throttled by prior control based on temperature to trip the turbine. To avoid. Once the turbine is tripped, it takes two hours or more to restart the unit and start up to the rated load, but it takes about one hour to start up from the no-load position to the rated load without tripping. Therefore, it is possible to reduce the start-up loss for restarting the unit.
[0031]
【The invention's effect】
As described above, according to the present invention, even if a pressure drop in the main steam supply system occurs during plant operation, the metal parts constituting the steam turbine are not adversely affected, and operation continuation is expanded. It is possible to obtain a control device for this type of thermal power plant that can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a control device for a thermal power plant according to the present invention and a schematic diagram of a thermal power plant equipped with the control device.
FIG. 2 is a diagram showing another embodiment of the control device for the thermal power plant of the present invention.
FIG. 3 is a diagram illustrating an example of a predetermined value characteristic of plant load versus main steam temperature.
FIG. 4 is a diagram showing a schematic configuration of a conventional thermal power plant.
FIG. 5 is a diagram showing an outline of a control logic of a control device for a conventional thermal power plant.
FIG. 6 is a diagram showing an example of plant load versus main steam pressure characteristics.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Boiler drum, 2, 3 ... Superheater, 4 ... Main steam piping, 5 ... Main steam control valve, 6, 8, 21 ... Steam turbine (high pressure, medium pressure, low pressure), 7 ... Reheater, DESCRIPTION OF SYMBOLS 10 ... Temperature detector, 12 ... Control circuit (valve control apparatus), 13 ... Boiler, 15 ... Temperature control valve, 16 ... Temperature reducer, 22 ... Condenser, 23 ... Condensate pump, 24 ... Low-pressure feed water heater 25 ... deaerator, 26 ... feed pump, 27 ... high-pressure feed water heater, 28 ... feed water flow control valve, 29 ... economizer, 34 ... switch, 35, 41 ... function generator, 36 ... subtractor, 37 ... monitor relay, 38 ... setting device, 43 ... low value selection circuit, 50 ... generator.

Claims (3)

A main steam supply system having a drum-type boiler, a steam turbine driven by main steam from the main steam supply system, a main steam control valve provided in the main steam supply system for adjusting the supply amount of the main steam; A control device for a thermal power plant, comprising: a valve control device for controlling the closing operation of the main steam control valve to a valve opening corresponding to no load when the pressure of the main steam supply system drops to a predetermined value. The main steam temperature is taken into the valve control device when the main steam pressure drops to the predetermined value, and when the temperature value is equal to or lower than the predetermined value, the main steam control valve is closed. A control device for a thermal power plant, characterized in that means for starting the operation is provided.   Control method for a thermal power plant that closes the main steam control valve of the main steam supply system to a valve opening corresponding to no load when the pressure of the main steam supplied from the steam supply system to the steam turbine drops to a predetermined value In the operation of the plant, when the temperature of the main steam supplied to the steam turbine is taken in during operation of the plant and the pressure of the main steam decreases to a predetermined value, the temperature of the main steam is equal to or lower than the predetermined value. A control method for a thermal power plant, wherein the closing operation of the main steam control valve is started.   Control method for a thermal power plant that closes the main steam control valve of the main steam supply system to a valve opening corresponding to no load when the pressure of the main steam supplied from the steam supply system to the steam turbine drops to a predetermined value The main steam supplied to the steam turbine is monitored when the pressure of the main steam drops to a predetermined value during operation of the plant, and the main steam is monitored when the temperature of the main steam exceeds a predetermined value. A control method for a thermal power plant characterized by blocking a throttle signal of an adjusting valve.

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