JPH052801B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a deaerator water level control device for thermal power and nuclear power plants.

[Background of the invention]

Deaerators in thermal power and nuclear power plants are installed in the water supply system to the boiler or nuclear reactor in order to remove dissolved oxygen that causes internal corrosion of the boiler or nuclear reactor and steam system. Steam is blown into the supplied condensate to heat it and deaerate it, which is then sent out as feed water for the boiler or reactor. The steam for heating the condensate is extracted from the turbine,
Alternatively, auxiliary steam is used to ensure the minimum pressure in the deaerator, and these heating steams come into contact with condensate and condense in the deaeration chamber of the deaerator.
It becomes part of the water supply for boilers or nuclear reactors. The water level in the deaerator depends on the amount of condensate flowing in from the condenser, the amount sent as feed water for the boiler or reactor, the amount of steam flowing in for heating, and the flow rate of recovered condensate from the boiler or reactor side. In addition to this, when the turbine is started or stopped, the water stored in the deaerator fluctuates due to fluctuations in the pressure inside the deaerator, and this causes the deaerator water level transmitter to indicate that the water level has apparently decreased. It may give a false signal. Conventional control methods for keeping the water level in the deaerator constant include, for example, as shown in Japanese Patent Application Laid-open No. 74504/1983.
The turbine load signal is used as a leading signal for deaerator water level control to improve followability to sudden changes in turbine load. If the deaerator water level transmitter output fluctuates significantly and the deaerator water level signal continues to be lower than the set position of the water level controller, the proportional + integral action of the water level controller will eventually cause the deaerator to If the water stored in the deaerator begins to flash, the condensate flow rate control valve for water level control will be fully open and the condensate flow rate will become excessive, causing the condensate pump or condensate boost pump to run out. It was necessary to manually switch the deaerator water level controller to prevent the condensate flow rate control valve from opening fully.

On the other hand, as shown in Japanese Patent Application Laid-open No. 54-79306, the opening degree of the condensate flow rate control valve is limited in order to suppress a sudden drop in deaerator pressure only when a sudden load reduction or shutdown of the turbine is detected. However, it does not limit the opening degree of the condensate flow rate control valve during normal startup and shutdown processes. Therefore, if the deaerator water level continues to be lower than the specified water level during normal startup and shutdown processes, the condensate flow rate control valve will be fully opened, and the condensate pump and
Alternatively, if the water level in the deaerator water storage tank drops, the deaerator water level controller should be switched to manual to prevent the condensate flow rate control valve from fully opening, as there is a risk of the condensate boost pump running out. It was necessary to prevent this.

[Purpose of the invention]

An object of the present invention is to provide a stable water level control device for a deaerator that prevents a condensate pump or a condensate booster pump from running out due to excessive opening of a condensate flow rate control valve.

[Summary of the invention]

The gist of the present invention is to limit the opening degree of the condensate flow rate control valve so as not to flow condensate in excess of the maximum allowable discharge flow rate of the condensate pump or the condensate boost pump.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, condensate stored in a condenser 1 is pressurized by condensate pumps 2a, 2b, and 2c, and includes a condensate pipe 11, a condensate flow rate control valve 21, a low-pressure heater 3, and a condensate flow rate. It is sent to the deaeration chamber 4a of the deaerator 4 through the transmitter 22. On the other hand, the bleed air from the turbine 9 passes through the bleed pipe 18 to the deaeration chamber 4a of the deaerator 4.
The condensate is mixed, heated and degassed, and stored as saturated water in the water storage tank 4b of the deaerator 4. Further, the water stored in the water storage tank 4b descends from the deaerator downcomer pipe 12 and is pressurized by the water supply pump 5, and the water in the water supply pipe 1
3. Water is supplied to the boiler 7 through the high pressure heater 6, water supply flow rate transmitter 25, and water separate drain cooler 8. In the boiler 7, the water is sent to a water separator 7b via a heater 7a, where it is separated from steam. The separated steam is sent to the turbine 9 through the heater 7c and the main steam pipe 17.
They work inside the building and generate electricity using the generator 10.
The steam that has done work is condensed in the condenser 1, stored at its bottom, and circulated again to the deaerator 4 by condensate pumps 2a, 2b, 2c. Drainage is separated by the water separator 7b during the plant startup process after the boiler burner ignition, during the plant shutdown process, and during low load.
Water is stored. This drain is sent to the water separator drain cooler 8 through the water separator drain pipe 14, where it heats the water supplied to the boiler 7, and the drain itself is cooled and the drain recovery pipe 15,
The collected drain is collected into the deaerator 4 through the flow control valve 29. A part of this drain is flashed in the deaerator, mixes and heats the condensate flowing in from the condensate pipe 11, becomes saturated water, is stored in the deaerator water storage tank 4b, and is sent to the boiler 7 again by the water supply pump 5. Sent. During the start-up process and the stop process, the drain flow rate in the water separator 7b is transiently large and may not be recovered by the deaerator 4. At this time, the drain dump control valve 28 provided in the drain dump pipe 16 opens and the excess drain is removed. Drain is discharged to condenser 1. During the startup process before the burner ignition of the boiler or when condensate is not recovered from the water separator 7b to the deaerator 4, the deaerator pressure control valve 3 is supplied from the auxiliary steam source 30.
1. Steam is blown into the deaerator 4 via the auxiliary steam pipe 32, and the inflowing condensate is mixed, heated, and deaerated, and is stored in the water storage tank 4b of the deaerator 4 as saturated water. Note that 24 is a deaerator water level transmitter, and 26 is a generator output transmitter.

Figure 2 is a water level control system diagram for a deaerator according to the present invention. The output signal of the transmitter 24 is transmitted to the deaerator water level controller 64, where proportional + integral calculations are performed, and the output signal is transmitted to the water supply flow rate transmitter 25 by the calculator 65.
Perform addition/subtraction calculations with the output signal to obtain the required make-up water flow rate signal for the deaerator. This signal is transmitted to a selector 66 for condensate flow rate restriction. When one condensate pump is in operation, the switch 70 is set from the signal setting device 69.
A signal equivalent to the rated flow rate of one condensate pump is transmitted via the first-order delay device 67 to the selector 66, which compares it with the signal from the calculator 65 and selects one of the flow rate signals on the smaller flow rate side. It is transmitted to the condensate flow rate controller 68 as a flow rate setting signal. When two condensate pumps are in operation, a signal corresponding to the rated flow rate of the two condensate pumps is transmitted from the signal setting device 71 via the switch 72 and the primary lag device 67 to the selector 66, and the condensate When three pumps are in operation, a signal equivalent to the rated flow rate of three condensate pumps is transmitted from the signal setting device 73 to the selector 66 via the switcher 47 and the primary lag device 67. There is.

At the same time, the measurement signal of the condensate flow rate transmitter 22 is also transmitted to the condensate flow rate controller 68, and the condensate flow rate controller 68 performs proportional + integral calculations on the deviation between the signal of the condensate flow rate transmitter 22 and the set signal. The condensate flow rate control valve 21 is controlled to maintain the water level in the deaerator 4 at a specified value. In the unlikely event that the pressure inside the deaerator fluctuates and the deaerator water level flushes, the output of the deaerator water level transmitter 24 fluctuates greatly.
If an erroneous signal indicating that the deaerator water level has decreased is transmitted to the deaerator water level controller 64, the deaerator water level controller 64
The output operates in the direction of increasing the condensate flow rate, but the selector 66 transmits to the condensate flow rate controller 68 only a signal that is limited to a rated flow rate or less corresponding to the number of condensate pumps in operation at that time. Therefore, the set flow rate of the condensate flow rate controller is never set higher than the total rated flow rate of the condensate pump at that time.

Note that the input signal of the selector 66 is input to the monitor switch 6.
1, and if the signal on the primary delay device 67 side becomes large, an alarm is issued.

In the embodiment, the condensate flow rate limit signal was set based on the number of operating condensate pumps, but the present invention is not limited to this. As shown in FIG. 3, the generator output signal is calculated by a function. Since the plant is operated to increase the number of condensate pumps in operation according to the generator output as shown in Figure 4, the condensate flow rate is calculated by the generator 80 and is increased by about 10% to match the generator output. By adding this, a condensate flow rate restriction signal can be obtained. Further, although the selector 66 is placed in the set flow rate signal circuit of the condensate flow rate controller, the present invention is not limited to this, and by installing it on the output side of the flow rate controller 68 as shown in FIG. It is possible to prevent the flow rate control valve 21 from opening too much.

In addition, in the explanation, the generator output signal is functionally calculated to generate a condensate flow rate limit signal, but this is not limited to the following: Turbine first stage pressure, turbine extraction pressure, main steam flow rate, and water supply water flow rate, which have a functional relationship with the generator output. It can also be determined by any signal of flow rate.

FIG. 5 is a system diagram of another embodiment of the present invention.

〔Effect of the invention〕

According to the present invention, the condensate flow rate can be limited to within the maximum allowable flow rate of the condensate pump or the condensate booster pump, and the plant start-up process, shutdown process,
Under any operating conditions during load changes, the deaerator can be operated stably without causing the condensate pump or the condensate boost pump to run out.

[Brief explanation of the drawing]

Fig. 1 is a piping system diagram of a thermal power plant showing an embodiment of the present invention, Figs. 2 and 3 are water level control system diagrams of a deaerator of the present invention, and Fig. 4 is a condensate water level control system diagram of the present invention. The flow rate restriction setting diagram, FIG. 5, is a system diagram of another embodiment of the present invention. 21... Condensate flow rate control valve, 22... Condensate flow rate transmitter, 68... Condensate flow rate regulator.

Claims (1)

[Scope of Claims] 1. A deaerator water level control device installed in a condensate system that supplies condensate from a condenser to a deaerator via a plurality of parallel pumps, which controls the deaerator water level using the deaerator water level. In a deaerator water level control device including an adjusting means for adjusting the flow rate of condensate to the deaerator based on the obtained control signal, the deaerator water level is adjusted according to a maximum allowable discharge flow rate determined by the number of operating units of the plurality of parallel pumps. 1. A deaerator water level control device characterized by being provided with a limiting means for limiting a control signal obtained using. 2 A deaerator water level control device installed in a condensate system that supplies condensate after driving a generator coupled to a turbine from a condenser to a deaerator via a plurality of parallel pumps. In a deaerator water level control device including a control means for adjusting the flow rate of condensate to the deaerator based on a control signal obtained using the gas water level, the output of the generator or a process quantity having a functional relationship therewith is detected. A deaerator water level control device, further comprising a limiting means for limiting a control signal obtained using the deaerator water level according to a detected value.