JPS598721B2 - Steam generator operation control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a steam generator, particularly a shell-and-tube steam generator used in a fast breeder reactor.

For flows with large changes in specific volume due to phase changes,
There is always a possibility that flow instability phenomena may occur.

In a boiler, if the flow of the heated fluid, such as water, becomes unstable in the heat transfer tubes, the heat transfer tubes will immediately burn out. The fluid to be heated flowing through the multi-layer heat transfer tube is mixed at the gathering part and the pressure is equalized at the same time, thereby preventing the occurrence of unstable phenomena.

In a shell-and-tube steam generator (hereinafter referred to as a steam generator), even if an unstable phenomenon occurs within the heat exchanger tube through which the fluid to be heated flows, the heat exchanger tube will not burn out.

However, the integrity of heat transfer tubes is severely compromised by temperature cycling and mechanical vibrations associated with instability phenomena.

In a steam generator applied to a fast breeder reactor, high-temperature sodium, which is a heating fluid, flows on the shell side, and water, which is a heated fluid, flows on the heat transfer tube side, so the water is heated by the sodium and turns into superheated steam. and flows out from the steam generator.

In such steam generators, if the integrity of the heat transfer tubes is compromised due to the occurrence of an unstable phenomenon, water or sodium will be ejected to the side and cause an explosive chemical reaction. In this method, a method is adopted in which a restriction is provided at the water supply port of the heat exchanger tube.

Even if any of the above methods is adopted, it is difficult to guarantee the stability of the flow of the heated fluid in the heat transfer tubes under all operating conditions of the steam generator, including during startup and partial load. .

Therefore, in order to operate the steam generator soundly under all operating conditions, it is necessary to quantitatively detect the stability margin in that state, even if no instability phenomenon occurs, so that steam generation is possible only in the stable region. It would be even more convenient for the operation if a control method for operating the equipment could be established.

An object of the present invention is to provide an operation control device for a steam generator that can operate stably even in a steam generator having heat transfer tubes including only riser tubes.

Another object of the present invention is to provide an operation control device for a steam generator that provides good transient characteristics and is capable of stable operation.

The first feature of the present invention is that the measurement device is arranged in parallel with the heat transfer tube and is connected to the heated side fluid supply pipe and the heated side fluid discharge pipe, which are connected to both ends of the heat transfer tube or both ends of the heat transfer tube. a pipe, a flow rate control means provided on the measurement pipe outside the shell, and a first flow rate measurement means provided on the 11 pipe outside the shell to measure a first flow rate of the fluid to be heated in the measurement pipe. , a second flow rate measuring means provided in the fluid supply pipe on the heated side, and means for detecting flow instability in the measurement pipe based on the first flow rate when the flow rate leg means for reducing the first flow rate is operated. , the second flow rate of the heated fluid per heat transfer tube obtained based on the output signal of the second flow rate measuring means, and the first flow rate at the time when the flow instability detection means outputs the flow instability signal. means for determining the stability of the flow in the heat transfer tube based on the flow stability determination means; and means for adjusting the flow rate ratio of the side fluids.

The second feature of the present invention is that the measurement piping is arranged in parallel with the heat transfer tube and is connected to a heated side fluid supply pipe and a heated side fluid discharge pipe, respectively, and both ends thereof are connected to both ends of the heat transfer tube. a flow rate control means provided in the measurement piping outside the shell; a first flow measurement means provided in the measurement piping outside the shell to measure a first flow rate of the fluid to be heated in the measurement piping; a second flow rate measuring means provided on the side fluid supply pipe;
means for detecting flow instability in the measurement piping based on the first flow rate when operating the flow rate control means for reducing the flow rate; and one heat transfer tube a detected based on the output signal of the second flow rate measuring means means for determining the stability of the flow in the heat transfer tube based on the second flow rate of the fluid on the heated side and the first flow rate at the time when the flow instability detection means outputs the flow instability signal; It is a means for detecting the temperature of the heating side fluid flowing in, and includes means for controlling the flow rate of the heating side fluid based on the output signal of the flow stability determining means and the temperature detecting means.

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, 1 is an evaporation generator applied to a fast breeder reactor, which includes a shell 2 through which a heating side fluid (thorium) flows, and a shell 2 housed in this shell 2 through which a heated side fluid (water) flows. It is composed of a large number of heat transfer tubes 3, and each heat transfer tube 3 is connected to a water supply pipe 4 at one end and to a steam pipe 5 at the other end.

The sodium in the shell 2 is pressurized by a pump 10, flows through a pipe 8 into a heat source 7 (for example, a nuclear reactor, an intermediate heat exchanger), and is heated.

This heated sodium flows into the shell 2 via the pipe 9, exchanges heat with the water flowing through the heat transfer tube 3, and becomes humid.
It is then returned to the pump 10 again.

On the other hand, water is pressurized by a pump 6, flows into the steam generator 1 via the water supply pipe 4, is evenly distributed to a large number of heat transfer tubes 3 within the steam generator 1, and is preheated, boiled, and heated by heat exchange with sodium.
It is superheated, collected again and discharged into steam pipe 5.

This outflow steam is used for power or industrial purposes, but its temperature and pressure are usually specified from the load side, and the steam conditions are set by the pressure setting signal 17 and temperature setting signal 18.

Steam pressure is measured by a pressure gauge 11, and the measured pressure signal 11a is sent to an adder 24 and compared with a pressure setting signal 17.

If there is a difference between the two signals 11a and 17, the deviation signal is sent to the pump 6, and its rotation speed is adjusted so that the steam pressure is equal to the set value.

The steam temperature is measured by a thermometer 12, and this temperature signal 1
2a is sent to an adder 25 and compared with the temperature setting signal 18.

If there is a difference between the two 12a and 1B, the deviation signal is sent to the heat source 7 via the regulator 15, and the heat source 70 adjusts the calorific value so that the steam temperature becomes equal to the set value.

If the water supply flow rate of the pump 6 changes due to the pressure deviation signal, the steam temperature will naturally change, so if the pressure deviation signal is used to compensate for the change in the amount of heat generated by the heat source 70 via the regulator 15. Allows for better control.

In principle, the flow rate of sodium can be arbitrarily selected, but the maximum temperature is usually selected to be as low as possible within an allowable range in relation to the steam temperature.

The temperature of the sodium heated by the heat source 7 is measured by a thermometer 13, and this temperature signal 13a is sent to an adder 26 and compared with a sodium temperature setting signal 19 preprogrammed in relation to the load.

If there is a difference between the two signals 13a, 19, this deviation signal 22 is passed through an adder 28 and used to adjust the pump 100 rotational speed.

On the other hand, the flow state on the water side in the heat transfer tube 3 is determined by the stability detection device 1.
4, this stability signal 21 is sent to an adder 27 and compared with the stability margin signal 20.

If there is a difference between the two signals 21, 20, this deviation signal is rectified by the rectifier circuit 16, the positive signal is cut off, and only the negative deviation signal 23 is used to adjust the pump 100 rotation speed. Ru.

In other words, the sum signal of the deviation signals 22 and 23 causes the pump 10 to
The zero rotation speed is adjusted.

The deviation signal 22 is a signal representing a deviation from a pre-programmed operating state so that good followability can be changed, and the other deviation signal 23 is a signal representing a deviation from a pre-programmed operating state so that good followability can be changed. This is a signal indicating that there is insufficient power margin.

By determining the sodium side flow rate based on the balance between both signals 22 and 23, the steam generator can be operated in an operating state with good followability and sufficient stability.

The specific structure of the stability detector 14 will be explained with reference to FIG.

The stability detector 14 includes a flow meter 29, a measurement heat transfer tube 30, a flow meter 31, a flow rate control valve 32, a flow rate instability discriminator 34, and a stability calculator 35.

The heat exchanger tube 30 for measurement is arranged in parallel with the heat exchanger tube 3 in the shell 2, one end of this heat exchanger tube 30 is connected to the water supply pipe 4 via a flow rate control valve 31, and the other end is connected to a steam pipe via a flow meter 32. 5 respectively.

A flow meter 29 is provided on the pump 6 outlet side of the water supply pipe 4.

When the stability detector 14 detects the flow stability of water in the heat transfer tube 3, first, the valve driving device 33 gradually closes the flow control valve 32 to reduce the flow rate of water supplied to the measurement heat transfer tube 30. do.

Then, in the heat exchanger tube for measurement 30, the ratio of the flow rate of water flowing inside the tube and the flow rate of the water flowing outside the tube becomes large, and an unstable phenomenon occurs in the flow of water inside the heat exchanger tube for measurement 30. .

Whether or not this unstable phenomenon has occurred is determined by analyzing the waveform of the flow rate signal 36 from the flow meter 31 using the flow instability discriminator 34.

In addition, the stability calculator 35 calculates the feed water flow rate per heat transfer tube 3 from the measurement signal 38 of the total feed water flow rate measured by the flow meter 29, and this calculated value and the flow instability discriminator 34 calculate the feed water flow rate per heat transfer tube 3.
The average value 3γ of the flow rate of water flowing through the measurement heat exchanger tube 30 at the time of occurrence of the unstable phenomenon sent from
From the relationship between both 37 and 38, the flow stability of water in the heat exchanger tube 3 is quantitatively calculated.

Further, at the same time as the signal 39 indicating that unstable flow has occurred in the measurement heat transfer tube 30 is generated, the stability signal 21 is held, and furthermore, the flow control valve 3 is held by the operation of the valve drive device 33.
2 is reset to the initial state.

Figure 3 shows the temperature distribution on the water side and sodium side under load of a once-through steam generator. Corresponds to the outlet and sodium inlet locations.

This figure also shows two types of temperature distributions in which the feed water flow rate, feed water temperature, and steam temperature are the same, but the operating conditions are different.

In other words, the combination of sodium temperature A and water-vapor temperature A shown by solid lines 40.42 is an example of operating state A when the sodium flow rate is low but the sodium inlet temperature is high, and the sodium temperature combination shown by broken lines 41.43, respectively The combination of temperature B and water-steam temperature B is an example of operating state B in which the sodium inlet temperature is low in exchange for a high sodium flow rate.

In the former operating state A, the flow of the water-steam system is stable, as will be described later, but because the temperature difference between the sodium inlet temperature and the steam outlet temperature is large, it is difficult to operate in a transient state such as when there is a change in the feed water flow rate. This increases the fluctuation range of the steam outlet temperature, which is undesirable from the viewpoint of steam temperature control.

In the latter operating condition B, on the contrary, the flow of the water-steam system tends to become unstable, but because the temperature difference between the sodium inlet temperature and the steam outlet temperature is extremely small, even in transient conditions, there is a large amount of steam in response to changes in the feedwater flow rate. This is preferable in terms of control because it does not cause temperature fluctuations.

In this way, ensuring flow stability and achieving favorable transient characteristics require mutually contradictory operating conditions, so the sodium flow rate must be within a range that satisfies the above two requirements. It is preferable to use the stability detection device 14 to monitor the flow stability of the water-steam system in the heat transfer tube 3 to ensure a reasonable stability margin, and to change the sodium temperature to have good transient characteristics. By adjusting the sodium pump 100 rotation speed so that it approaches the programmed sodium temperature set point within the range specified, it is possible to operate the steam generator with stable flow and good load following. become.

Since the flow instability discriminator 34 is used, the steam generator 1
It is possible to reliably detect the phenomenon of unstable flow within the heat exchanger tube 3 consisting of only the riser tube portion as shown in FIG.

Figure 4 shows an IJ heating steam generator with a heat exchanger tube 50 m long, with a feed water temperature of 240°C and a steam temperature of approximately 500°C.
The analysis results when operating under the condition of steam pressure 170 ky/cm are plotted by plotting the amplification factor of the amplitude of the 1st to 3rd order natural vibration mode on the vertical axis and plotting the flow rate ratio of sodium and water on the horizontal axis. It can be considered that the value with the opposite sign of the amplification factor quantitatively indicates the stability of the flow.

In other words, in a mode where the amplification factor is positive, the vibration amplitude increases over time and the flow becomes unstable, and conversely, in a mode where the amplification factor is negative.

In this case, even if vibration occurs, the amplitude attenuates over time, so the flow is stable.

In the example shown in Figure 4, the flow rate ratio of sodium and water is 11:
It can be seen that if it is 4 or less, unstable flow does not occur in any mode, and the stability of flow is improved under operating conditions where the sodium flow rate is low.

In the above example, a method of reducing the flow rate on the sodium side was adopted as an operation to stabilize the flow on the water side, but in this case, the steam generator does not follow the load, but instead the load side follows the steam generator. In a nuclear reactor, a similar effect can be obtained by increasing the feedwater flow rate instead of decreasing the sodium flow rate.

According to the first feature of the present invention, it is possible to reliably detect flow instability in the heat transfer tube consisting of only the riser pipe portion, and it is possible to stably operate the steam generator.

Furthermore, according to the second feature, it is possible to simultaneously secure flow stability and achieve favorable transient characteristics, which are contradictory operating conditions.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the method of operating the steam generator of the present invention;
Figure 2 is a system diagram showing the configuration of the stability detection device used in the present invention, Figure 3 is an explanatory diagram showing the operating status of the steam generator, and Figure 4 is unstable flow in the heat transfer tube. FIG. 3 is an explanatory diagram showing characteristics. Explanation of symbols 1...Steam generator, 2...Shell, 3
...Heat transfer tube, 6,10...Pump, 14...Stability detection device, 30...Measurement heat transfer tube.

Claims (1)

[Scope of Claims] 1. An operation control device for a steam generator having a shell in which a heating fluid flows, and a plurality of heat transfer tubes disposed within the shell and in which a heated fluid flows. A measurement pipe arranged in parallel with the heat tube and whose both ends are connected to the heated side fluid supply pipe and the heated side fluid discharge pipe, respectively, and outside the shell a flow rate control means provided on the measurement pipe; a first flow rate measurement means provided on the measurement pipe outside the shell to measure a first flow rate of the fluid on the heated side in the measurement pipe; a second flow rate measurement means provided in the fluid supply pipe; and means for detecting flow instability in the measurement pipe based on the first flow rate when operating the flow rate control means that controls the first flow rate; the second flow rate of the fluid on the heated side of the heat exchanger tube a obtained based on the output signal of the second flow rate measuring means and the second flow rate at the time when the flow instability detection means outputs the flow instability signal; a means for determining the stability of the flow in the heat exchanger tube based on the flow rate; and a means for determining the stability of the flow in the heat exchanger tube based on the output signal of the flow stability determination means; A steam generator operation control device comprising means for adjusting the flow ratio of a heating side fluid and a heated side fluid. 2. An operation control device for a steam generator having a shell in which a heating fluid flows, and a plurality of heat transfer tubes disposed within the shell and in which a heated fluid flows, the heat transfer tubes being arranged in parallel with the heat transfer tubes. , and measurement piping whose both ends are connected to the heated side fluid supply pipe and the heated side fluid discharge pipe, respectively, and the flow rate provided in the measurement piping outside the shell. a control means, a first flow rate measuring means provided in the measurement piping outside the shell and measuring a first flow rate of the heated fluid in the measurement piping, and a first flow rate measuring means provided in the heated fluid supply pipe. 2 flow rate measuring means, means for detecting flow instability in the measurement piping based on the first flow rate when the flow rate control means is operated to reduce the first flow rate, and an output signal of the second flow rate measuring means. The second flow rate of the heated fluid per heat transfer tube obtained based on the flow rate and the first flow rate at the time when the flow instability detection means outputs the flow instability signal. means for determining the stability of the flow; means for detecting the temperature of the heating fluid flowing into the steam generator; and determining the flow rate of the heating fluid based on the output signals of the flow stability determining means and the temperature detecting means. A steam generator operation control device comprising means for controlling.