JPS63105301A - Deaerator water-level controller - Google Patents

Abstract

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

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to deaerator water level control for thermal power plants and nuclear couplants, and in particular, to a deaerator water level control suitable for controlling the water level during a sudden load reduction of a turbine or after load shedding. Related to air water level control device.

[Conventional technology]

Deaerators for thermal power plants and nuclear power plants are installed in the water system of the steam generator and in the water supply system to the steam generator in order to remove dissolved oxygen that causes internal corrosion of the steam system. Steam is injected into the condensate supplied from the water heater, heated and degassed, and then sent out as feed water for the steam generator.The steam used to heat the condensate is oil from the turbine or auxiliary steam. The heating steam comes into contact with a portion of the condensate in the degassing chamber of the deaerator, condenses, and is stored in the deaerator water storage tank, where it becomes part of the water supply to the steam generator.

The water stored in the deaerator water tank flows through the deaerator downcomer pipe, is led to the water supply pump, is pressurized, and is sent to the steam generator.

When the turbine load suddenly decreases or when the load is cut off, the amount of oil in the glue bottle for heating the low-pressure feed water heater installed at the inlet of the deaerator suddenly decreases, and the temperature of the condensate flowing into the deaerator rapidly decreases. Since the oil for heating the deaerator is also exhausted, the pressure inside the deaerator drops rapidly.

The water flowing out from the water storage tank flows into the water supply pump through the deaerator downpipe, but it takes about three minutes for the water to flow from the deaerator to the pump, so when the turbine load suddenly decreases, the temperature inside the deaerator may drop. The water at the pump inlet tends to be at a higher temperature, and the water self-flashes at the pump inlet, making the pump more susceptible to cavitation. In order to prevent the occurrence of cavitation, in the prior art, for example, as in Japanese Patent Publication No. 59-81402, an index for the saturation temperature of the water pump inlet fluid is obtained from the pressure inside the deaerators, and the actual measured pump inlet temperature is calculated. Compare the fluid temperature with the aforementioned indicators,
There was a method to adjust the flow rate of condensate flowing into the deaerator as needed, but the level difference between the deaerator and the feed water pump was 20~
The length of the deaerator downpipe is 30 m, and the specific gravity of the fluid in the deaerator downpipe changes from time to time, so the saturation temperature of the feed water pump inlet fluid cannot be determined accurately from the deaerator pressure, and the temperature measuring device has a time constant. Since there is a primary response delay of approximately 1 minute, measuring the temperature at the inlet of the water supply pump would result in a 5-hour lag, making it impossible to effectively adjust the condensate flow rate.

[Problems to be Solved by the Invention] The above-mentioned prior art does not take into account the response delay of the temperature sensor, the sudden decrease in turbine load, or the change in the specific gravity of the fluid in the deaerator downcomer at the time of load cutoff. , due to the inability to effectively control the condensate flowing into the deaerator when the turbine load suddenly decreases or when the turbine is shut off.

There was a problem that cavitation prevention in the water pump was not sufficient.

An object of the present invention is to effectively prevent cavitation of a water supply pump when the turbine load suddenly decreases or is shut off.

[Means for solving problems]

The above purpose is to measure the flow rate passing through the deaerator downcomer pipe and the feed water pump, and based on this flow rate, calculate the time it takes for the fluid to flow from the deaerator outlet to the feed water pump, and calculate the response delay characteristics of the temperature sensor. Then, predict in advance the temperature when the fluid reaches the water supply pump inlet from the fluid temperature at the deaerator outlet, calculate the predicted saturation pressure of the water at the water supply pump inlet from this temperature, and calculate the predicted saturation pressure of the water at the water supply pump inlet from this temperature. This is achieved by comparing the measured values of pump inlet pressure and, if necessary, restricting the flow rate of condensate flowing into the deaerator to prevent a sudden drop in deaerator pressure.

[Effect]

Temperature detectors have a large response delay and generally have first-order lag characteristics with a time constant of about -minutes, but the fluid temperature is measured at the deaerator downcomer at the deaerator outlet.

The fluid flows from here to the feed pump for up to three minutes or so, and the flow lag time required for flow is inversely proportional to the flow rate in the deaerator downcomer. Therefore, by measuring the flow rate of the water supply pump and using the fact that the temperature measured by the temperature detector becomes the water supply pump inlet fluid temperature after the dead time of the flow delay time, we can calculate the saturation pressure at the pump inlet that changes moment by moment. Predict without delay.

Measure the water supply pump inlet pressure and compare it with the S pressure.

If the actual measured pressure is lower, by restricting the flow rate of condensate flowing into the deaerator, the pressure drop in the deaerator will be gradual and the water pump inlet pressure will stop decreasing. The pressure is higher, which prevents cavitation from occurring in the water pump.

〔Example〕

Hereinafter, a piping system according to an embodiment of the present invention will be explained with reference to FIG. The condenser 6 cools the exhaust gas of the turbine 4 with cooling water, converts it into condensate, and pressurizes it with a condensate pump 7 . Water discharged from the condensate pump 7 is sent to the low-pressure feed water heater 9 via the deaerator water level control valve 8, where the condensate is heated and heated by turbine oil air and then passed through the condensate flow meter 10 to the deaerator. 11 degassing chambers 1
Sent to 1a. The deaerator 11 includes a deaeration chamber 11a, a water storage tank 11b, a communication pipe LIC, and a pressure equalization pipe LID.

Oil from the turbine 4 is introduced into the deaeration chamber 11a through the oil air pipe 2b, fused with condensate sent to the deaeration chamber, mixed and heated, deaerated, and sent to the water storage tank llb as water supply to the steam generator 1. Can be stored.

The stored water is led to the water supply pump 18 through the downcomer pipe 25, the temperature sensor 14, and the pressure detector 15, is pressurized, and passes through the flow rate detector 19, and then passes through the piping 27, the high-pressure water supply heater 2o, and the water supply flow rate detection. The steam is sent to the steam generator 1 via the steam generator 21.

The steam generated in the steam generator 1 is sent to the turbine 4 via the piping 22 and the control valve 3 to perform work, and then sent to the condenser 6 where it is cooled and becomes condensed water and circulated again.

In FIG. 2, the temperature of the fluid at the outlet of the deaerator is detected by the temperature detector 14 and transmitted to the delay calculator 35.

Detecting the outlet flow rate of the water supply pump 18 with a flow rate detector 19,
It is transmitted to the delay time prediction calculator 34. Here temperature sensor 1
4, predict the flow delay time up to the water supply pump 18, subtract the primary response delay time at the temperature detector 14, predict the overall delay time, and convert the output signal to the delay calculator 35.
tell to.

The delay calculator 35 delays and outputs the signal from the temperature detector 14 in accordance with the output signal of the delay time prediction calculator 34, accurately predicts the temperature when the water flows to the inlet of the water supply pump 18, and outputs the signal. is transmitted to the saturation pressure calculator 36. The inlet pressure of the water supply pump 18 is detected by the pressure detector 15 and the subtractor 37
m, the signal from the pressure detector 15 is subtracted from the signal from the saturation pressure calculator 36, and the deviation signal between the predicted saturation pressure at the inlet of the water supply pump and the measured pressure is transmitted to the valve opening limit calculator 48. The valve opening limit calculator 48 is configured such that when the input signal is negative, the output is 100%, and when the input signal is positive, the output signal is decreased in proportion to the input signal. The output of the valve opening limit calculator 48 is transmitted to the low level signal selector 49.

The water level detector 28 detects the water level in the water storage tank llb of the deaerator 11.
, and transmits it to the subtracter 42a of the water level controller 42, and calculates the deviation from the setting device 42c to calculate the proportional f-integral operation opening calculator 4.
2b, and the calculation result is transmitted to the low-order signal selector 49.

When the water level in the water storage tank llb is higher than the water level set by the setting device 42c, the output of the deaerator water level controller 42 decreases, and when the water level in the water storage tank llb is lower, the output of the deaerator water level controller 42 decreases.
The output of the deaerator water level control valve 8 increases, and the low level signal selector 49 compares the signal of the valve opening limit calculator 48 with the output signal of the deaerator water level controller 42, selects the low level signal, and During normal operation, the deaerator water level control valve 8 is controlled by the output signal of the deaerator water level controller 42, and the water level in the water storage tank llb is controlled to be constant.

When the pressure signal actually measured by the pressure detector 15 becomes lower than the pressure signal predicted by the saturation pressure calculator 36 when the turbine load suddenly decreases or when the load is cut off, or when the pressure difference becomes less than the specified value α. In this case, the valve opening limit calculator 48
and a low level signal selector 49 to limit the opening degree of the deaerator water level control valve.

According to this embodiment, even when the turbine load suddenly decreases or when the load is cut off, the deaerator water level can be stably controlled without cavitation occurring in the water supply pump.

FIG. 3 shows a piping assembly showing another embodiment.

The condenser 6 cools the exhaust gas of the turbine 4 with cooling water to form condensate water, which is then pressurized by a condensate pump 7 .

Water discharged from the condensate pump 7 is sent to the low-pressure feed water heater 9 via the deaerator water level control valve 8, where the condensate is heated and heated by turbine oil air and then passed through the condensate flow meter 10 to the deaerator. It is sent to the deaeration chamber 11a of No. 11. The deaerator 11 includes a deaeration chamber 11a, a water storage tank llb, a communication pipe 11c, and a pressure equalization pipe lid.

The oil from the turbine 4 is introduced into the deaeration chamber 11a through the oil air pipe 2b, contacts the condensate sent to the deaeration chamber, is mixed and heated, deaerated, and is stored in the water storage tank llb as water to be supplied to the steam generator 1. It will be done.

The stored water is stored in three systems of deaerator precipitation equipment 25a.

♀5b, 25c and temperature detectors 14a, 14b.

14c and pressure detectors 15a, 15b, 15c, the water is led to water supply pumps 18a, 18b* 18c, and is pressurized.
After passing through the flow rate detectors 19 a r 19 b + 19 c, the water joins and is sent to the steam generator 1 via the pipe 27 , the high pressure feed water heater 2 o and the feed water flow rate detector 21 .

The steam generated in the steam generator 1 is sent to the turbine 4 via the piping 22 and the control valve 3 to do work, and then sent to the condenser 6 where it is cooled and becomes condensed water, which is circulated again. Furthermore, when the turbine load suddenly decreases, etc.

In order to replace the hot water in the deaerator downcomer pipes 25a, 25b, 25c with cold water, the hot water replacement valves 16a*16b* branch from the inlet of the water supply pumps 18a e b + c.
16'c and then pressurized by the hot water displacement pump 17.

It circulates through the pipes 24 and 23 to the deaeration chamber 11a.

As shown in FIG. 4, the fluid temperature at the deaerator outlet is detected by a temperature exchanger 14a and transmitted to a delay calculator 35a.

The outlet flow rate of the water supply pump 18a is detected by the flow rate detector 19a and transmitted to the adder 33a. Furthermore, when the hot water displacement pump 17 is operated, the flow rate equivalent to the hot water displacement pump is 33.3.
The output signal is added to the signal generator 32a which outputs a signal corresponding to %, and the resultant signal is transmitted to the delay time prediction calculator 34a. Here, the flow delay time from the temperature sensor 14a to the water supply pump 18a is predicted, the primary response delay time at the temperature sensor 14a is subtracted, the overall delay time is predicted, and the output signal is delayed. Tell a.

The delay calculator 35a delays and outputs the signal from the temperature detector 14a in accordance with the output signal of the delay time prediction calculator 34a, and sets the temperature when the water flows to the inlet of the feed pump 18a by 6.
The prediction is made a second in advance and the output is transmitted to the saturation pressure calculator 36a. The pressure at the inlet of the water supply pump 18a is detected by the pressure detector 15a, and transmitted to the subtractor 37a, which subtracts the signal from the pressure detector 15a from the signal from the saturation pressure calculator 36a to predict the inlet of the water supply pump 6 seconds earlier. A deviation signal between the saturation pressure and the measured pressure is transmitted to the high-level selector 38. The high-level signal selection 38 has three systems of water supply pumps 18a and 18b.

Among the signals obtained by subtracting the measured pressure signal from the predicted saturation pressure signal obtained for each of 18c, the signal on the highest pressure side is selected and output, and the subtracter 41 of the condensate flow rate restriction controller 41
a, the deviation from the setting device 41c is determined, and the output signal is sent to the proportional + integral moving plate calculation unit 41b, which outputs the signal to the low-level signal selector 44.
transmitted to.

Condensate flow control fIMi! The output of the i1 meter 41 increases when the actually measured pressure at the inlet of the water supply pump is higher than the predicted saturation pressure, and decreases when the pressure is lower than the predicted saturation pressure.

The water level in the deaerator water storage tank llb is determined by the deaerator water level detector 28.
is detected and transmitted to the subtractor 42a of the deaerator water level controller 42,
Calculate the deviation from the H constant device 42c and use the proportional + integral moving plate calculator 42
b, and the calculation result is transmitted to the adder 43. When the water level of the water storage tank llb is higher than the set water level of the setting device 42c, the output of the deaerator water level controller 42 decreases, and when the water level of the water storage tank 11b is lower, the output of the deaerator water level controller 42 increases. .

The output signal of the water supply flow rate detector 21 to the steam generator 1 is transmitted to the adder 43, where it is added to the output signal of the deaerator water level controller 42, and the signal is sent to the low level selector 44 as a target inflow signal for the inflow to the deaerator. It is transmitted to the subtractor 45a of the condensate flow rate controller 45 through the . The low-level signal selector 44 compares the output signal of the adder 43 and the output signal of the condensate flow rate limiting controller 41b, selects a low-level flow rate signal, and transmits it to the condensate flow rate controller 45.

The flow rate of condensate flowing into the deaerator 11 is detected by a condensate flow meter 10 provided on the outlet side of the low-pressure feed water heater 9 so as not to include the flow rate from the hot water displacement pump, and is detected by a subtractor of the condensate flow rate adjustment section 45. 45a, the deviation with the low-level signal selector 44 is determined, and the result is transmitted to the proportional + integral moving plate calculator 45b, whose output is transmitted to the deaerator water level control valve 8. The condensate flow rate regulator 45 uses the output signal of the low level signal selection 44 as a target value, and when the signal of the condensate flow rate detector 10 is lower than the target value, the output signal increases and the deaerator water level control valve 8 is opened. If the signal from the condensate flow rate detector 10 is higher than the target value, the output signal decreases and the opening degree of the deaerator water level control valve 8 is decreased so that the deaerator water level always remains at the set value. control so that

According to this embodiment, in the case of having a royal water supply pump and a hot water displacement pump, it is possible to stably control the deaerator water level without causing cavitation at the inlet of any of the water supply pumps.

FIG. 5 is a control flow diagram showing still another embodiment of the present invention.

The water level in the water storage tank llb is detected by the deaerator water level detector 28 and transmitted to the subtractor 42a of the deaerator water level controller 42, and the deviation from the setting signal from the water level setting calculator 46 is determined and proportional + integral moving plate calculation is performed. Tell the vessel 42b.

Its output is transmitted to adder 43.

The high-level signal selector 38 selects the highest pressure signal among the signals obtained by subtracting the measured pressure signal from the predicted pressure signal obtained for each of the three water supply pumps 18a, 18b, and 18c, just as shown in FIG. and outputs,
The water level setting calculator 46 sets the output signal to 50% when the input signal is positive, sets the deaerator water level controller 42 to the regular water level, and when the input signal is negative or below the specified value β. 5 The output signal is set to 50% or less, the output signal is decreased in proportion to the input signal, and the set water level of the deaerator water level controller 42 is set lower, so that the actually measured pressure is lower than the predicted saturation pressure at the water supply pump inlet pressure. If the pressure is low, lower the target flow rate of the condensate flow rate controller by lowering the set water level of the deaerator water level controller.

Substantially reduces the opening of the deaerator water level control valve.

According to this embodiment, when a royal water supply pump and a hot water displacement pump are installed, the deaerator water level can be stably controlled without cavitation occurring at the inlet of any of the water supply pumps. .

〔Effect of the invention〕

According to the present invention, the saturation pressure of the fluid at the inlet of the water pump can be predicted without any time delay.

Cavitation occurrence at the water supply pump and self-flushing at the water supply pump inlet can be prevented in advance.

[Brief explanation of the drawing]

FIG. 1 is a system diagram around a deaerator showing an embodiment of the present invention. 1... Steam generator, 4... Turbine, 6... Condenser, 8... Deaerator water level control valve.
, Eng. Bundle 1 Figure 18 - 11th generation Fuj ■ Soph 14 --- Staring, Reisui Blind Coming Figure 4

Claims (1)

[Scope of Claims] 1. Turbine exhaust gas is condensed in a condenser and guided to the deaerator through a water level control valve of the deaerator for deaeration, and a water supply pump provided below the deaerator. In the system where water is introduced through a downcomer pipe, pressurized by the water supply pump, and supplied to the steam generator, the saturation pressure at the inlet of the water supply pump is determined from the temperature at the outlet of the deaerator and the flow rate of the water supply pump. The predicted by calculation is compared with the actually measured inlet pressure of the water supply pump, and as a result, if the actually measured inlet pressure of the water supply pump is lower pressure or the pressure difference is less than the specified value, the above A deaerator water level control device that reduces the amount of condensate flowing into the deaerator and reduces the rate of decrease in the internal pressure of the deaerator.