JPS6017997B2 - Heat exchanger protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchanger protection device, and particularly to a heat exchanger that exchanges heat between high-pressure fluid and low-pressure fluid. The present invention relates to a heat exchanger protection device that can detect leakage of high-pressure fluid to a low-pressure fluid side.

In general, a heat exchanger is a device that transfers heat between a high-temperature fluid and a low-temperature fluid, and is arranged at a portion where heat exchange is required in a boiler plant, a nuclear power plant, or the like.

Moreover, among the heat exchangers mentioned above, those used in a high pressure system are constructed with a thick wall so as to be able to withstand the high pressure. By the way, for heat exchangers used in high-pressure systems in boiler plants equipped with once-through boilers,
There are some types that are used only when the plant starts and stops or when the load is low, and are not used during normal operation. However, even during this normal operation, the heat exchanger is exposed to high pressure, so if the high-pressure low-temperature fluid (for example, feed water) leaks, the steam-water separation tank of the once-through boiler must be rapidly cooled. This may lead to a major accident, and furthermore, a sudden drop in main steam temperature may lead to a turbine accident in a plant or the like. Furthermore, as is well known, the rate of load change in thermal power plants is becoming faster year by year.

Therefore, the heat exchanger changes its usage status (
Rapidly changes from heat exchange state to inconvenient state (heat exchange unnecessary state)
Or, conversely, it may be changed from a state of inconvenience to a state of use. As a result of being used under such conditions of repeated heating and cooling, a high thermal stress is applied to the heat exchanger as a thick-walled container, and there is a risk that cracks may occur in the heat exchanger. It is an object of the present invention to provide a heat exchanger protection device that eliminates the disadvantages of the prior art described above, suppresses the occurrence of thermal stress, and protects the heat exchanger by detecting leakage of high-pressure fluid. In order to achieve the above object, a predetermined amount of high-temperature fluid is passed through the high-temperature fluid piping system including the heat exchanger to generate heat even when the heat exchanger is inconvenient, and the flow of the high-temperature fluid is kept constant. The temperature drop of the high-temperature fluid at at least two different points in the high-temperature fluid piping system near the heat exchanger is detected when the system is stopped every hour.

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a system diagram showing an embodiment of a heat exchanger protection device according to the present invention.

As shown in FIG. 1, the first embodiment of the present invention is constructed as follows. Symbol 1 is a pump, and this pump 1
The discharge side thereof is connected to the inflow part of the high-pressure feed water heater 3 via a pipe 2, and the pump increases the pressure of feed water as a low-temperature fluid and supplies it to the high-pressure feed water heater 3. This high-pressure feed water heater 3 is a device that heats the high-pressure water supplied from its inlet to a constant temperature and flows out from its outlet. The heat exchanger 5 connects the water supply pipe 4A to the low-temperature side inflow part and allows high-pressure water supply to flow into the water supply pipe A. The heat exchanger 5 is connected to a boiler 6, and high-pressure feed water flows inside the heat exchanger 5 during heat exchange. The heat exchanger 5 also has a high-temperature side inlet and a high-temperature side outlet, and is a device that only transfers and exchanges heat without mixing high-temperature fluid and low-temperature fluid.
A bypass valve 7 is connected to the water supply pipe 4A and the water supply pipe 4B connected to the heat exchanger 5, and when heat exchange is not to be performed, the bypass valve 7 is opened so that the water supply does not flow through the heat exchanger 5 and is bypassed. . The boiler 6 supplies the water supplied from the water supply pipe 4B to the steam and moisture equipment 65 through the energy saver 61, the water wall pipe 62, the cage wall pipe 63, and the ceiling wall pipe 64, and the steam and water separator. The steam separated from steam and water in step 65 is further transferred to a primary superheater 66, a secondary heating device 67, and a tertiary superheater 68.
The steam is then superheated and supplied to a turbine 9 via a steam pipe 8.

This turbine 9 has its exhaust side connected to a condenser 101. The condensate separated in the steam and moisture equipment 65 of the boiler 6 is supplied to the heat exchanger 5 from the high temperature side inlet of the heat exchanger 5 via the startup bypass piping 11A as a low-pressure high-temperature fluid piping system. After heat exchange in the heat exchanger 5, the hot water is transferred from the high temperature side outlet to the IB via bypass piping.
The condensate is circulated to the deaerator 13 via the condensate recovery control valve 12. In other words, the condensate recovery control valve 12 is
The terminal end of bypass piping 11B as a low-pressure high-temperature fluid piping system connected to the high-temperature side outlet of the heat exchanger 5 and the deaerator 1
3, and when heat exchange is not performed, the valve 12
By closing the heat exchanger 5, condensate as a high-temperature fluid is prevented from flowing into the heat exchanger 5. A first on-off valve 14 is connected to the piping in the vicinity of the front and back of this condensate recovery control valve 12, and is opened when no heat exchange is performed to supply a predetermined amount of high-temperature fluid to the bypass piping 11A and the heat exchanger 6. , the high-temperature fluid piping system including the bypass piping blade B and the control valve 12, and is designed to overcome these problems. Again, the end of the bypass pipe QIA is connected to the dump valve shaft 5.
This dump valve 15 is connected to the condenser 10. The bypass piping 11A connects a second control valve 16 near the twilling portion of the dump valve 15 and the bypass piping 11A,
This second control valve S is connected to a deaerator 13. Note that the deaerator turtle 3 is connected to the suction side of the pump 1 to supply water. Further, signals regarding the control circuit 10, the rotational speed of the turbine 9, and the state of the generator,
It takes in other signals to monitor the load condition, closes the bypass valve 7 at startup, and controls the opening and closing of the control valve 12 and dump valve 15 when the load is low, below the boiler minimum water supply amount, and also opens and closes the first and second valves. The valves 14 and 16 are controlled to close, and when the load is high, the control valve 12 and the dump valve 15 are closed, the bypass valve 7 is opened, and the first and second
The opening/closing valves 14 and 16 are controlled to open.

The operation of the first embodiment configured as described above will be explained below. First, the feed water whose pressure has been increased by the feed water pump 1 is supplied to the boiler 6 via the high temperature feed water radiator 3, but during this time it is passed through a heat exchanger 5 in order to recover the heat of the high temperature fluid flowing through the startup bypass pipe 11A. At startup, the bypass valve 7 that bypasses the heat exchanger 5 is fully opened according to a command from the control circuit 100, and the energy saver 61 is passed through the heat exchanger 5.
supply to.

The water supply is provided through a wall pipe 62, a cage wall pipe 63, and a ceiling wall pipe 64.
The water is supplied to the steam/moisture broiler 65 through the. This steam and moisture porcelain 6
The condensate separated from steam and water in step 5 is transferred to startup bypass piping 1 1A
is supplied to the heat exchanger 5 via. The hot water after this heat exchange is circulated to the deaerator 13 via the bypass pipe 1IB and the control valve 12. On the other hand, the steam separated in the steam separator 65 is transferred to the primary superheater 66, the secondary superheater 67, and the
Next, it is superheated in a superheater 68 and then passed through piping 8 to a turbine 9.
supplied to

In addition, when the load is lower than the boiler minimum water supply amount and the control circuit 10
If it is determined to be 0, the control valve 12 and dump valve 15 are controlled by the control circuit 10 according to the load state.

When the control circuit 100 determines that the load is high,
The condensate recovery adjustment valve 12 and the dump valve 15 to the deaerator 13 are completely closed by a command from the control circuit 100, and all the water supplied to the boiler 6 is turned into steam and supplied to the boiler 9.

Therefore, in this state, it is necessary to control the steam/moisture broiler 65, the starting bypass pipe 11A, and the first and second on-off valves 14 and 16, and to open the on-off valves 14 and 16 in order to make the starting bypass system work. Warm up the entire startup bypass system. That is, the steam/moisture hatcher 65, the startup bypass piping 11
A, the fluid flows on the upstream side of the heat exchanger 5, the control valve 12, and the dump valve 15, and after warming up, the fluid flows into the deaerator 1.
It will be collected on 3rd. According to this embodiment, heat loss is small and it is possible to supply as much heat as the amount of heat radiated. Next, a second embodiment of the present invention will be described.

The second embodiment has the same structure and functions as the first embodiment, and has the following additional features. That is, at least two high-temperature fluid temperature detectors 20 and 21 are disposed at two different points on the bypass pipe 11A as the inlet-side high-temperature fluid piping system of the heat exchanger 5, and the temperature is detected by the detectors 20 and 21. At the same time, the detection signal is taken into the control circuit 100. The control circuit 100' fully closes the first on-off valve 14 at regular intervals, and detects and compares the rate of temperature drop for a specified time using the temperature detection signals from the temperature detectors 20 and 21, and performs the steps in parentheses. It is arranged to generate an alarm signal or a signal for stopping the device when the difference exceeds a predetermined value. As described above, the control circuit 10 has the configuration of the first embodiment, and further includes the additional configuration as described above. FIG. 2 is a block diagram showing the configuration of this additional part. In this figure, numeral 101 is a program timer, and this program timer 101
outputs a signal to the solenoid section 14A of the on-off valve 14 to close the first on-off valve 14 for a predetermined time t every fixed period T. This closing signal from the program timer 101 causes the solenoid 14A to operate and close the valve body 1.
When the valve 148 is closed, the contact 14C of the limit switch attached to the on-off valve 14 is closed, and when the valve 148 is opened, the contact 14C is opened. One electrode of this contact 14C is connected to the positive pole (10) of the DC power supply, and the other electrode is connected to the negative pole (-) of the DC wire via the auxiliary relay 102, and when the contact 14C is closed, the auxiliary relay 1
The fins are attached to the 02. This auxiliary relay 10
2 has contacts 102A, 102B, and 102C, and moves in the direction of the arrow in the figure when the coil of the auxiliary relay 102 is energized. Reference numerals 103 and 104 are amplifier circuits, and these amplifier circuits 103 and 104 take in the detection signals from the temperature detectors 20 and 21 and amplify them to a predetermined voltage signal.

The amplifier circuit 103 has its output end connected to the normally closed contact of the relay contact 102A, and supplies a signal to the analog memory circuit 105 via this contact. This analog memory circuit 105 has its output terminal connected to the deviation calculation circuit 06 and also to the normally open contact of the contact 102A. This deviation calculation circuit 106 is an amplifier circuit 10
It takes in the output signal of 4 and outputs the deviation from the signal from the analog memory circuit turtle Q5, and its output end is connected to the proportional circuit turtle 07. The output terminal is connected to the normally open contact of the relay contact blade Q28, and when the normally open contact closes, the analog-digital conversion circuit (AD conversion circuit) 08 is connected and its output signal is The AD conversion circuit 88 digitizes the input signal and closes the contact 189 when the input signal exceeds a predetermined value. This contact turtle crab 9 is connected in series with the contact turtle Q2C and the coil of the auxiliary relay 316 and connected to the DC power supply, and both the contacts 189 and 1
When 82C is opened at the same time, the coil of the auxiliary relay turtle 18 is energized. When the auxiliary relay quantity IQ is energized, the alarm circuit trigger 9 issues an alarm. Further, the contact point OA may be used for generating a signal to stop the device. Furthermore, the code blade 12 is a signal generator, and its output is connected to the normally open contact of Q2B with a relay contact, and a Q% signal is always supplied to prevent malfunction when the AD conversion circuit J Tatehako is inconvenient. It is something. Therefore, the signal generator Tomomi 2 is not necessary if measures against malfunction have been taken. The operation of the second embodiment configured as described above will be explained below.

Since the pressure on the water supply side of the heat exchanger S is high, if there is a leak, the water supply as a high-pressure low-temperature fluid will flow backwards and flow into the steam/water separator 6.
6 will be cooled down.

Therefore, in this embodiment, "every fixed time T, for a specified time t,
The on-off valve 14 is fully opened and the temperature drop in those parts is measured based on the detection signals from the temperature detectors 2Q and 2 provided at the inlet side bypass pipe IA of the heat exchanger 5. This is to confirm that there are no leaks. That is, t high load operation occurs, and the control valve blade 2 and the dump valve tortoise 6 are closed by a command from the control circuit tortoise fin Q.
The on-off valves turtle 4 and turtle 6 are opened.

Next, a signal from the program timer 08 causes the opening/closing valve Kamekawa to be closed for a specified time t at regular intervals T.
Then, the contact point 4C is opened and the auxiliary relay 102 is energized. When the auxiliary relay 102 is energized, each contact IQ
2A, 102B and 102C each move in the direction of the arrow in the figure. The analog memory circuit Q5 stores the detection signal of the temperature detector 28 at the time when the on-off valve 14 is closed, and supplies it to the deviation calculation circuit 106. The deviation calculation circuit IQ6 uses the signal from the temperature detector 21 and the analog memory circuit 10.
The signal is subtracted from 5 and the result of the calculation is uniformly supplied to the AD conversion circuit 08 via the proportional circuit 1 pupil 7. When the deviation signal from the deviation calculation circuit mother mouse 6 is large, it is assumed that a leak has occurred in the heat exchanger 5, and the contact IQ9 is closed, and the relay contact 102C is closed. The auxiliary relay 110 is energized, the relay contact 1 8A is opened, and the alarm circuit 118 is operated to issue an alarm.Also, when the deviation signal from the deviation calculation circuit 1 Q6 is small, ``Of course, the contact IQ9 is opened. In other words, in this control circuit Tsuru Tsuru, the temperature detection signal from the temperature detector 28 when the on-off valve 84 is closed is stored, and the temperature detection signal from the temperature detector 21 is stored for a specified time t. Comparison with the recorded value indicates that the contact point 09 will not be closed due to the deviation signal when the temperature drops during normal heat dissipation.If there is a leak in the heat exchanger 5, the temperature detector 28 will be activated. The temperature of the temperature sensor 21 drops faster than that caused by normal heat dissipation, and then the temperature of the temperature sensor 21 drops rapidly. Since the two temperature detectors are compared for a period of time t, the deviation can be detected without fail.The second embodiment operates as described above.Furthermore, since it is configured as described above, Since the approximate amount of leakage can be determined from the time difference between when the temperature of the temperature detectors 2Q and 21 starts decreasing and the volume of the pipe 1 1A during this period, it is extremely advantageous for subsequent plant processing.Heat exchange during high load. The bypass valve of the heat exchanger 5 is fully open, but a small amount of feed water corresponding to the pressure loss of the valve 7 flows through the heat exchanger 5, so the thick walled portion on the water feed side is warmed up.

As described above, according to the present invention, the occurrence of thermal stress can be suppressed by making it possible to reduce the occurrence of thermal stress, and leakage of high-pressure fluid can be detected, which has the excellent effect of protecting the heat exchanger. have

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a specific example of a control circuit. 4... High pressure low temperature fluid piping, 5... Heat exchanger, 6... Boiler, 7... Bypass valve, 11... First on-off valve 20 and 21... ...Temperature detector,
100...Control circuit. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A heat exchanger connected to the low-temperature fluid piping system and the high-temperature fluid piping system to exchange heat between fluids flowing in the piping, and a heat exchanger connected to the low-temperature fluid piping system to exchange heat when heat exchange is not required. a bypass valve that detours low-temperature fluid flowing into the exchanger; a control valve that is connected to a high-temperature fluid piping system on the outlet side of the heat exchanger and prevents high-temperature fluid from flowing through the heat exchanger when heat exchange is not required; On-off valves connected before and after the control valve allow a predetermined amount of high-temperature fluid to flow even when heat exchange is not required, and monitor the heat load state and open the bypass valve and on-off valve and open/close the control valve when heat exchange is not required. A heat exchanger protection device comprising: a control circuit for controlling a heat exchanger; 2. A heat exchanger connected to the low-temperature fluid piping system and the high-temperature fluid piping system to exchange heat between the fluids flowing in the piping, and a low-temperature fluid connected to the low-temperature fluid piping system and flowing to the heat exchanger when heat exchange is not required. a bypass valve that bypasses the heat exchanger; a control valve that is connected to the high-temperature fluid piping system on the outlet side of the heat exchanger to prevent high-temperature fluid from flowing to the heat exchanger when heat exchange is not required; an on-off valve that is connected and allows a predetermined amount of high-temperature fluid to flow even when heat exchange is not required, at least two temperature detectors disposed at different parts of the high-temperature fluid piping on the inlet side of the heat exchanger, and monitors the heat load state, When heat exchange is not required, the bypass valve and the on-off valve are opened, and the opening and closing of the control valve is controlled, and the on-off valve is fully closed for a specified time at regular intervals, and the temperature detection signal from the temperature sensor at this time is 1. A heat exchanger protection device comprising: a control circuit that generates an alarm or device stop signal based on the above.