JPS6017604A - Controller for water level of deaerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to deaerator water level control for thermal power plants and nuclear couplants, and particularly relates to a water level control device that reduces water level fluctuations even after a sudden decrease in turbine load or shutdown.

[Background of the invention]

FIG. 1 is a diagram of a conventional condenser, deaerator, water supply and steam piping system for a boiler circuit.

The condensate stored in the lower part of the condenser 5 is pressurized by the condensate pump 7, and is degassed via the condensate flow meter 8, the deaerator water level control valve 9, and the low-pressure feed water heater 10. It is sent to the container 11. Bleed air from the turbine 3 is introduced into the deaerator deaeration chamber 11a, the condensate that has flowed in is heated, and the air in the compound water is separated because the direct position is raised. The separated air is discharged to the atmosphere through the orifice lie, and the saturated water with reduced air content is stored in the deaerator water storage tank llb.

If the output of the turbine 3 is low and air cannot be extracted, the pressure in the deaerator will drop, so the pressure regulator 36 detects this and opens the pressure regulating valve 18 to introduce steam from the auxiliary steam source 17. The deaerator deaeration chamber 11a is pressurized.

The water in the deaerator water storage tank 11b is stored in the boiler water supply pump 13.
The high-pressure feed water heater 5 and the feed water flow meter 19
It is sent to boiler 1 via all channels.

Steam generated from the boiler 1 is sent to the turbine 3, and the steam that has done work in the turbine 3 is stored in the lower part of the condenser 5.

FIG. 2 shows a water level control system for a deaerator water storage tank Ilb according to the prior art. The double water flow meter 31 detects the flow rate of condensate flowing into the deaerator and transmits it to the condensate flow rate controller 35. The target flow rate of the condensate flow meter is given by the boiler feed water flow meter 33, and if the water level of the deaerator water storage tank Ilb deviates from the set water level, the deaerator water level controller 37 provides a correction double number. is transmitted to the adder 34 to correct the target flow rate.

FIG. 3 is a diagram showing a deaerator water level control situation when conventional deaerator water storage tank water level control is performed.

When the load suddenly decreases at point A1, the boiler feed water flow rate first decreases rapidly. The target value of the condensate flow rate is lowered by detecting a decrease in the feed water flow rate, and the deaerator water level control valve 9 is also throttled down. Since the residence time is about 20 seconds, the amount of water flowing into the deaerator water storage tank llb continues even after the water supply flow rate has suddenly decreased.
The water level in the deaerator storage tank will rise.

When the water level of the deaerator water storage tank rises above the set level, the deaerator water level controller 3 and 7 output a positive signal, and in order to limit the double water flow rate, the target level of the condensate flow rate controller is set. By lowering the value, the deaerator water level is quickly controlled to a constant level, but due to the sudden decrease in the turbine load, the bleed air to the low pressure feed water heater 10 and the deaerator 11 no longer comes from the turbine, and the turbine load decreases. Generally, when the water decreases rapidly, there is a shortage of auxiliary steam and it is difficult to supply it to the deaerator. At this time, cold condensate flows into the deaerator chamber and lowers the internal pressure of the deaerator chamber 11a. Decrease rapidly. Since the deaerator degassing chamber 11a and the deaerator water storage tank llb are connected by a pressure equalizing pipe 11e, the deaerator chamber 11a and the deaerator water storage tank llb are connected by a pressure equalizing pipe 11e. Due to the sudden decrease in the internal pressure of the deaerator chamber 11a, the internal pressure of the deaerator water storage tank 11a also decreases, and as a result, the water stored in the water storage tank 11b is rapidly flanshed and the deaerator degasses. Trying to balance the room pressure.

As the internal pressure of the deaerator water storage tank decreases, the amount of flash increases, and the generated steam flows through the pressure equalization pipe IIIC to the deaerator degassing chamber tia. 7 As the amount of lash increases, the flow rate passing through the pressure equalization pipe IIC increases, the pressure loss in the pressure equalization pipe increases, and the internal pressure of the deaerator degassing chamber 11a also increases. The internal pressure becomes significantly higher. As a result, during normal operation, the condensate that has fallen through the deaerator communication pipe lid from the deaerator degassing chamber 11a to the deaerator water storage tank 11b becomes difficult to fall. As a result, the condensate flowing into the deaerator water storage tank is reduced, and the deaerator water storage tank llb
water level decreases. The deaerator water level controller 37 detects a decrease in the deaerator water level and outputs a correction signal to increase the target value of the condensate flow rate to more than the boiler feed water flow rate, and as a result, the amount of condensate flowing into the deaerator degassing chamber is reduced. As a result, the amount of flushing in the deaerator water storage tank increases, and the amount of flushing in the deaerator water storage tank increases, and the amount of flushing in the deaerator water storage tank increases, and the amount of flushing is increased through the deaerator communication pipe lid. This causes the stored water to flow back into the deaerator chamber 11a.

The deaerator degassing chamber is connected to the bleed pipe from the turbine as described above, and the deaerator storage water that has flowed back as described above flows back to the turbine through this bleed pipe 'f:, and the turbine blades are This is extremely dangerous as it can cause damage and damage the turbine. When the temperature of the water stored in the deaerator is almost the same as the temperature of the condensate flowing into the deaerator chamber 11a, the deaerator water storage is stopped and the deaerator stops. The water in the deaerator chamber 11a rapidly falls into the deaerator water tank, causing the water level in the deaerator water tank to rise rapidly. As a result, the deaerator water level controller 37 lowers the target value of the double water flow rate, decreases the opening degree of the deaerator water level control valve, and eventually closes it completely.
The water level in the deaerator water storage tank 11b will rise abnormally. As described above, there is a problem in that when the load suddenly decreases, the water level in the deaerator water storage tank 11b changes suddenly.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water level control device for a deaerator water storage tank that limits the flow rate of condensate flowing into the deaerator to a level greater than the flow rate of boiler feed water flowing out of the deaerator when the load suddenly decreases.

[Summary of the invention]

The key point of the present invention is to detect that the turbine load is suddenly reduced or shut off, the deaerator deaerator chamber pressure is higher than the deaerator water storage tank internal pressure, and the condensate flow rate is reduced to within the boiler feed water flow rate. There are limits.

[Embodiments of the invention]

FIG. 4 shows a deaerator water level control system of the present invention, and FIG. 5 shows a level switch for detecting the differential pressure between the deaerator water storage tank and the deaerator degassing chamber. A condensate flow meter 31 detects the flow rate of condensate flowing into the deaerator and transmits it to a condensate flow rate controller 35 of the Cashood setting type.

The target flow rate of the condensate flow meter 35 is given by the boiler feed water flow meter 33, and if the water level of the deaerator water storage tank Ilb deviates from the set water level, the deaerator water level controller 37 sends a correction signal. This is transmitted to the adder 34 and the target flow rate is corrected. The level switch 61a detects a sudden decrease in the turbine load and a decrease in the deaerator chamber pressure compared to the deaerator water storage tank internal pressure, and switches the signal from the 100% signal generator 45 to the boiler feed water flow meter 33 side. The signal is switched by the signal selector 41 and transmitted to the signal selector 40. The signal selector 40 compares the output signal of the adder 34 and the signal of the boiler x water flow meter 33, selects the lower flow rate side, and transmits it to the condensate flow rate controller 35 to perform deaeration in accordance with this target value. The deaerator water level control valve 9 is controlled to limit the water level of the deaerator water storage tank.

FIG. 7 shows the deaerator water level control situation when the deaerator water level is controlled according to the present invention.

At point A1, when the load is suddenly reduced, the boiler feed water flow rate first decreases rapidly. A decrease in the water supply flow rate is detected, the target value of the condensate flow rate is lowered, and the deaerator water level control valve is also throttled, but the response is delayed and the condensate stays in the deaerator chamber for about 20 minutes. In good time, the lowering of water to the deaerator water storage tank 11b should last for at least 20 seconds after the water supply flow rate suddenly decreases, and therefore the water level in the deaerator water tank will rise. do. When the water level in the deaerator water storage tank rises above the set level of the water level controller 37, the deaerator water level controller 37 outputs a correction signal, and furthermore, in order to completely limit the condensate flow rate, the condensate flow rate controller 35 outputs a correction signal. By lowering the target value of Cold condensate flows into the deaerator chamber and rapidly reduces the internal pressure of the deaerator chamber 11a. Since the water stored in the deaerator water storage in the evening is saturated water at the pressure before the sudden load drop, the water is pumped in the deaerator water storage tank for 7 hours to balance the pressure in the deaerator chamber, but the deaerator The pressure in the water tank is higher. At this time, the pressure difference between the deaerator water storage tank llb and the deaerator deaeration chamber lla is expressed as a water level in the level detection pipe that connects the lower side of the deaerator water storage tank llb and the upper side of the deaerator deaeration chamber. The level switch 61M detects that the water level has risen above the specified water level, switches the signal switch 41, and transmits the boiler feed water flow rate signal to the signal selector 40. As a result, the target flow rate of the condensate flow rate controller is never set higher than the boiler feed water flow rate.

Therefore, the amount of condensate flowing into the deaerator will not be below a certain level.
The rate of pressure drop in the deaerator chamber is also reduced. Even if the internal pressure in the deaerator chamber drops, the amount of condensate that accumulates in the deaerator chamber will not be degassed because the amount of water supplied to the deaerator will not exceed the amount that flows out of the deaerator chamber. The water level of the deaerator storage water level decreases, but eventually at point B3, the deaerator storage water temperature and the temperature of the condensate flowing into the deaerator become almost equal, and the deaerator water level decreases.
When the 7-lush in 1b stopped, it accumulated in the degassing chamber of the deaerator. After the condensate fell into the deaerator storage tank, the water level in the deaerator storage tank almost matched the water level set on the water level controller, and it was stable without any sudden changes in the condensate flow rate or the deaerator water level. Water level control becomes possible.

The pressure difference between the deaerator chamber 11a and the deaerator water storage tank llb can be detected by directly detecting the pressure difference using a differential pressure detector 63 as shown in FIG. Water level transmitter 62b of water storage tank iib and deaerator water storage tank 11
A level difference meter detects the level difference between the water level detector 62a between the deaerator b and the deaerator degassing chamber 11a. As shown in FIG. 9, a method is required in which the deviation between the boiler feedwater flowmeter 33 and the condensate flowmeter 31 is detected by the flow rate difference meter 64, and the point A in FIG. 3 is detected.

[Brief explanation of drawings]

Figure 1 is a conventional piping system diagram (condenser, deaerator, voyage), Figure 2 (t) is a water level control system diagram of a deaerator according to the conventional technology, and Figure 3 is a conventional piping system diagram (condenser, deaerator, voyage). An explanatory diagram of the deaerator water level control situation, Fig. 4 is a deaerator water level control system diagram of one practical example of the present invention, and Fig. 5 is an explanatory diagram of the deaerator water storage tank and deaerator degassing chamber according to the present invention. A diagram showing differential pressure detection, FIG. 6 is a diagram showing differential pressure detection between the deaerator water storage tank and the deaerator degassing chamber according to an application example of the present invention, and FIG. 7 is a diagram showing control of the deaerator water level according to the present invention. A situation diagram, Fig. 8 is an explanatory diagram of the pressure difference between the deaerator deaeration chamber and the deaerator water storage tank according to an application example of the present invention, and Fig. 9 is a detection system for the deviation between the boiler feed water flow meter and the condensate flow meter. It is a diagram. In addition, in the figure, 2 is the main steam pipe, 4 is the generator, 6 is the condenser, 1
2f′i deaerator downpipe, 14 is water supply pipe, 16 is bleed pipe,
31 is a condensate flow value needle, 32 is a deaerator water level gauge, 33 is a boiler feed water flow meter, 34 is an addition calculator, 35ii is a temporary water flow rate controller, 61a is a level switch, 61b is a level detection pipe, 63 is a level difference It is a total. J2... Boi 2.2... Main steam pipe, 3... Turbine, 4... Generator, 5... Condenser, 6... Condensate pipe, 7... Condensate pump , 8... Element for detecting bale water flow rate, 9... Deaerator water level control valve, lO... Low pressure feed water heater, l 1... Deaerator, lla... Deaerator degassing Chamber, llb...Deaerator water storage tank, 11C...Pressure equalization pipe, lid...Connection pipe, 12...Deaerator down pipe, 1
3... Boiler water pump, 14... Water supply pipe, 15.
... Pressure feed water heater, 16a, 16b.

Claims (1)

[Scope of Claims] 1. Turbine exhaust gas is condensed in a condenser and guided to a deaerator deaeration chamber through a deaerator water level control valve for deaeration, and is provided below the deaeration chamber. In a device that supplies water to the boiler using a pump after storing water in the deaerator deaerator chamber 7, it is detected that the pressure in the deaerator water storage tank has increased from the deaerator deaerator chamber to the deaerator water tank. a first means for detecting a signal from the first means and a sudden load reduction of the turbine, or a signal from the first means and a load interruption of the turbine to limit the opening;
A deaerator water level control device that prevents an abnormal rise in water levels in the deaerator water storage tank and the deaerator degassing chamber.