JPS5854322B2 - Control method and device for grand steam generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling a steam generator for gland sealing of a steam turbine in a boiling water nuclear power plant.

Conventionally, in boiling water nuclear power plants, part of the main steam is introduced into the shaft seal of the steam turbine to seal the shaft, and the steam discharged from the shaft seal is sent to the gland steam condenser. It was being discharged.

In the gland steam condenser, the steam discharged from the shaft seal is separated into steam and water, and the separated air is discharged into the atmosphere from the exhaust pipe, and the condensate is transferred to the main condenser. The force was discharged into the vessel.

In the above-mentioned conventional shaft sealing method, main steam containing radioactive substances is used as ground steam, so the exhaust gas released into the atmosphere from the exhaust stack contains radioactive noble gas, albeit in a small amount. It included 1 etc.

Therefore, recently, in order to further reduce the emission of radioactive materials from nuclear power plants, clean steam generated from in-house boilers is used as ground steam for steam turbines, while condenser discharge water is used as main steam or A method has been adopted in which a grand steam generator of a type that is heated by steam turbine extraction air is installed and the steam generated by the grand steam generator is used as grand steam.

In boiling water nuclear power plants that have adopted this improved shaft sealing method, the steam generated by the in-house boiler is used as ground steam while the steam turbine is stopped, before startup, and some time after startup. However, the steam generated by the grand steam generator is used as ground steam from the moment the steam pressure generated by the grand steam generator reaches a predetermined pressure after the steam turbine is started, but the steam generated by the in-house boiler is used as the ground steam. The longer the time, the greater the amount of condensate to the main system, so it is desirable to switch the ground steam generation source from the in-house boiler to the grand steam generator as soon as possible after starting the steam turbine.

Therefore, in the past, reactor-generated steam was controlled to be introduced into the grand steam generator from the time the steam turbine was started, but even with such control, the ground steam generation source was transferred from the in-house boiler to the grand steam generator. There was a phenomenon in which the ground vapor pressure significantly decreased when switching to

The cause of this is mainly the structure of the grand steam generator, but according to an investigation by the present inventor, it has been found that there is also a problem in the control method of the grand steam generator.

Therefore, an object of the present invention is to improve the conventional control method of a grand steam generator, and to prevent a significant drop in grand steam pressure and steam amount even when the ground steam generation source is switched from an in-house boiler to a grand steam generator. An object of the present invention is to provide a method and apparatus for controlling a grand steam generator.

An actual case of the present invention will be described below, but prior to this, the outline of the piping system of a known boiling water nuclear power plant equipped with a ground steam generator to which the present invention is applied is shown in Figs. 1 and 2. Explain with reference to.

In FIG. 1, 1 is a nuclear reactor, 2 is a steam turbine 3 is a condenser, 4 is a grand steam condenser, 5 is a grand steam generator, and 6 is an in-house boiler.

Steam generated in the nuclear reactor 1 is introduced into the steam turbine 2 through the main steam pipe 7, works in the steam turbine 2, and then is discharged into the condenser 3.

The main steam pipe 7 is provided with a main stop valve 8 and a control valve 9, and a bypass pipe 10 is connected from the main steam pipe T to the upstream side of the main stop valve 8.
is branching out.

The bypass pipe 10 is connected to the condenser 3, and the bypass pipe 10
is provided with a bypass valve 11.

A heating steam pipe 12 as a first means branches from the main steam pipe 7 on the front side (upstream side) of the main stop valve 8, and the heating steam pipe 12 is connected to the heating drum of the grand steam generator 5, that is, the heater. Connected to 5A.

The heating steam pipe 12 is provided with a control valve 13 as a first valve, and the turbine bleed pipe 1 is connected downstream of the control valve 13.
4 is connected.

A check valve 15 is attached to the turbine bleed pipe 14 .

The grand steam generator 5 has a cylindrical air-water drum, that is, a main body 5B, and the main body 5B contains condensate purified by a demineralizer 16 (when this condensate is directly introduced into the grand steam generator 5, and once After being returned to the condensate storage tank, new condensate (often referred to as make-up water) from the condensate storage tank may be introduced into the grand steam generator.

) is connected to a water supply pipe 17 for introducing water, and a steam pipe 19 communicating with a ground steam pipe 18 is connected.

The five heaters are immersed in purified condensate in the main body 5B, and a drain tank 5C is attached to one end of the heater.

The drain tank 5C is connected to the feedwater heater (not shown) and the condenser 3 via the drain pipe 20, and the steam in the heater 5A is normally condensed to the feedwater heater, but when the plant is started or stopped. etc. are discharged to the condenser 3.

The ground steam pipe 18 is further connected to a steam pipe 21 for guiding the steam generated by the in-house boiler 6, and the steam pipe 21 is provided with a control valve 22.

A control valve 23 is provided in the steam pipe 19 , and this control valve 23 and the control valve 13 constitute a part of the control device for the grand steam generator 5 .

In FIG. 1, 24 indicates a water supply pipe 25 to the nuclear reactor 1, and a water supply pump.

Moreover, the dotted line represents the air pipe line, 26 is the air extractor, 2
7 represents a gaseous waste treatment device, and 28 represents an exhaust stack.

FIG. 2 is an enlarged view of the grand steam generator 5 shown in FIG. 1, its control device, and a piping system related to the grand steam generator 5. As shown in FIG.

In FIG. 2, 29 is a controller for detecting the steam pressure at the inlet of the heater 5A and controlling the pressure to a specified value, and 30 is a controller for detecting the steam pressure in the main body 5B of the grand steam generator 5. and a controller for controlling the pressure to a specified value, 3
1 is a controller for detecting the ground steam pressure and controlling the pressure to a specified value; these controllers 29.30
．． 31 constitutes a control device for the grand steam generator 5 together with the control valves 13 and 23.

The control device further includes an output signal of the controller 29 and a controller 30.
A controller 32 (a high-level signal selector or a low-level signal selector is used depending on the operating characteristics of the valve) that controls the opening degree of the control valve 13 to the smaller side according to either value of the output signal.
Contains 1.

On the other hand, a controller 33 for controlling the control valve 22 is provided in the steam pipe 21 of the in-house boiler 6, and this controller 33 controls the opening degree of the valve 22 according to the detection result of the pressure inside the steam pipe 21. do.

Next, a conventional method of controlling a grand steam generator and its problems will be described with reference to FIGS. 1 and 2.

When the steam turbine 2 is started, the main blocking valve 8, the control valve 9, and the control valve 23 are closed, and the control valve 22 is opened.

Therefore, clean steam is supplied to the grand steam pipe 18 from the in-house boiler 6.

On the other hand, the temperature and pressure of the nuclear reactor 1 are increased after the degassing operation, but at this time the bypass valve 11 is controlled to keep the temperature increase rate constant so that the thermal stress of the reactor does not become excessive.

As a result, the pressure in the reactor 1 and the main steam pipe 7 is gradually increased.

The steam in the main steam pipe 7 is sent to the grand steam generator 5 through the heating steam pipe 12 and is also used for heating.

The heated steam from this main steam is used as a control 1 to control the steam pressure generated in the grand steam generator 5 to 0.7 kg/crrL2.
-1-3g output signal and its heating steam pressure 3kvc
Among the output signals of the controller 29 that controls IrL2, the controller 32 selects a signal that controls the valve opening to the smaller side, and sends it to the control valve 13 to control it.

When the grand steam generator 5 is started, the water contained in the main body 5B is empty and the steam pressure is low, so the controller 30 outputs a full open signal.

During the pressurization process of reactor 1, the main steam pressure is 3 kg/c.
A controller 29 that adjusts the heating steam pressure when the pressure is less than m2.
A fully open signal is issued, and the control valve 13 is operated fully open.

If the main steam pressure exceeds 3 to 9/cIIL2, the controller 29
A signal is issued to throttle the control valve 13, thereby controlling the heating steam pressure to 3 kg/crIL2.

However, the steam pressure generated by the grand steam generator is 0.71
cg/cm2, the deviation from the set value of the controller 30 reverses from negative to positive, and a signal is issued to further throttle the control valve 13 by proportional + integral action (control liquid calculation), reducing the generated pressure to 0. It comes to be controlled at 71cg/cm2.

The controller 32 compares the output signals of the controllers 29 and 30 and controls the valve opening of the control valve 13 to the smaller side. The heater 5 rises to 1 (setting value of controller 30).
In order to prevent the pressure in section A from becoming excessive, the controller 29 is used to control the pressure to a specified level (the set pressure of the controller 29 is 3 kg/cm2).

The heating steam pressure required to maintain the generated steam pressure at 0.7 kg/cIn2 is the evaporation amount (kVHr) of the grand steam generator.
However, during normal operation, 1.51 cg/cm2 is required to cover the required amount of turbine gland seal steam, and when the gland steam generator is started, illustrations are omitted in Figures 1 and 2. Although the amount of evaporation is ensured by the startup line for discharging the generated steam from the grand steam generator 5 to the condenser 3, the amount of evaporation is generally less than the amount of evaporation during normal operation, so the amount of evaporation is The pressure is 1.51
It is balanced in a state that is even lower than cg/C1rL2.

The evaporation pressure generated by the grand steam generator is the specified value (0,71
cg/cm2), the discharge from the startup line to the condenser is stopped, and the control valve 23 installed in the generated steam pipe 19 is gradually opened by the manual operator of the controller 31 ( Until then, the turbine gland steam pressure was controlled to a specified pressure using steam from the in-house boiler 6, so the control valve 23, which could cause disturbance, was forcibly closed.)
, switching the turbine gland steam from the in-house boiler to the gland steam generator.

Generally, this switching operation can be accomplished by setting the controller 31 on the ground steam generator side to automatic mode, and switching the controller 33 on the in-house boiler side to manual mode and gradually closing it.

The control system (controller 31 and control valve 23) on the grand steam generator side follows this and increases the valve opening degree to complete the switching, but in the inventor's experience, as described below, the grand steam generator Due to the poor starting characteristics of the control valve 2, a problem occurred in which the pressure in the gland steam pipe 18 decreased.
3 was adopted, but the switching operation required a long time.

When this switching operation is completed, the gland steam generator is controlled to control the generated steam pressure to 0.71cg/am2, and the heating steam pressure at this time is 1.51cg/am2.
g/cm2.

As the plant output increases, in this example the plant output 3
In the 8th gear, the extraction pressure from the steam turbine 2 is 1.5, g/
At CTL2fx, extracted steam begins to enter, and if the output is higher than this, the generated steam pressure will increase due to the extracted steam pressure, and the heating steam from the main steam will be shut off (when the generated steam pressure is 0.7 kg/am)
2, the output becomes a fully closed signal due to the integral operation of the controller 30).

Conventionally, according to such a control method, when the ground steam source is switched from the in-house boiler 6 to the grand steam generator 5, the required amount of steam cannot be obtained from the grand steam generator 5, and the pressure in the grand steam pipe 18 increases. There is a problem of rapidly decreasing
It was necessary to solve this problem.

In order to solve this problem, the present invention has investigated the structure and control method of the grand steam generator, and found that although there are points to be improved in the grand steam generator itself, it is possible to solve the above problems by improving the control method. It turned out that the problem could be solved.

The main cause of the above-mentioned problems lies in the structure of the gland steam generator.

In other words, in conventional ground steam generators, convection of the retained water is relatively difficult to occur due to its structure, so if sufficient heat is not given to the retained water, a layer of high-temperature water forms only near the water surface. On the other hand, cold water gathers around the heater 5A.

Therefore, even if heating steam is supplied to the heater 5A in such a state, the heat of the heating steam is taken away by the cold water around the heater and is not given to the high temperature water near the water surface. Heating of the vessel 5A does not immediately lead to an increase in the amount of evaporation.

In the conventional control method, the steam pressure generated by the gland steam generator is set to 0.7 kg/am2, which is the pressure required to stably supply turbine gland seal steam, so that operation can be performed using turbine bleed air to the maximum extent possible. be.

Performance and sufficient evaporation amount can be obtained during normal operation even when the generated steam pressure is 0.7 kg7cm2.

This is presumed to be because during normal operation, sufficient convection occurs within the gland steam generator body, and the retained water is heated to a state 1 close to saturated water corresponding to the generated steam pressure.

When starting the grand steam generator, steam is discharged to the condenser 3 through the above-mentioned starting line to ensure the amount of steam.
In general, this amount of evaporation is small, so sufficient convection cannot be obtained in the gland steam generator, and the water held in the main body is cold at the beginning of startup, so it takes a long time for it to be heated with saturated water 1. .

It has been found that the insufficient amount of evaporation in the gland steam generator 5, which is pressed when the gland steam source is switched, is caused by the low amount of heat retained in the gland steam generator at the time of switching.

The present invention solves the problems of the conventional control methods as described above, and provides a method for controlling a gland steam generator that does not cause insufficient evaporation when switching the gland steam source.

A feature of the control method of the present invention is that the steam pressure generated by the grand steam generator is controlled by changing the set value of the controller 30 according to the output state of the steam turbine or equipment related to the steam turbine. The purpose is to change the output state according to the output state of related equipment.

In this case, the setting value of the controller 30 increases when the output of the steam turbine or related equipment is small, and increases as the output of the equipment increases.
It is desirable that the setting value of 0 is changed to become smaller.

According to such a control method, it is possible to maximize the operating range of the grand steam generator 5 by turbine extraction as in the conventional technology, and when the plant output is small, the steam pressure generated by the grand steam generator 5 by the main steam is reduced. can be increased.

As with the conventional technology, even if the convection inside the grand steam generator main body 5B is not sufficient at startup and the retained water temperature is not heated to around the saturated water temperature 1 when switching the grand steam source, the generated steam pressure is increased. As a result, the amount of heat retained within the grand steam generator body increases compared to the case of the conventional technology, so even if the ground steam source is switched from the in-house boiler to the grand steam generator 5, the amount of evaporation in the grand steam generator will be insufficient. There is no fear.

FIG. 3 is a diagram showing a configuration for implementing the control method of the present invention as described above.

Since the same reference numerals as those shown in FIG. 2 indicate the same parts shown in FIG. 2, the explanations for these same parts will be omitted.

In the figure, 34 is a signal representing the output state of equipment such as a steam turbine, and 35 is a function generator that generates a predetermined function signal in response to the signal.

The output of the function generator 35 is applied to the controller 30 and the set value of the controller 30 is changed according to the output signal of the function generator 35.

The function signal generated from the function generator 35 has a negative differential coefficient, and therefore tends to be large when the output of equipment such as a steam turbine is small, and to become smaller as the output becomes larger.

Therefore, the controller 32 selects the output of the controller 30 to
3, when the output of the steam turbine 2 is small, the steam pressure generated by the grand steam generator 5 is high, and as the output of the steam turbine 2 increases, the steam pressure generated is controlled to be low. .

As a result, a large amount of heat is stored in the heater 5A of the grand steam generator 5 even when the steam turbine 2 is started, so that there is no shortage of evaporation in the grand steam generator 5 even when switching the grand steam source. Since this does not occur, the ground steam source can be switched from the in-house boiler to the grand steam generator 5 earlier than in the prior art.

FIG. 4 shows an example of the operating characteristics of the grand steam generator 5 operated with the configuration shown in FIG.

In Fig. 4, the horizontal axis is the plant output of the steam turbine, etc., and the vertical axis is the pressure, and the curve C1 is the pressure variation curve C2 of the heating steam supplied to the grand steam generator 5. 5 shows the change in the generated steam pressure.

In the figure, when the plant output is 0 to 38%4, control is performed by the control valve 13 using heating from the main steam, and from 38 to 38%.
100% i indicates the range heated (uncontrolled) by turbine bleed air, as in the prior art.

Further, the weight reduction control of the heated steam by the main steam (control by the controller 29) is controlled to 3I-cq/crI12 as in the prior art.

Generated air positive force control by main steam (control by controller 30)
In the conventional technology, the setting value of the controller is 0.7 mq/CIrL.
2, but the set value was changed to 0.7 kq.
/cm2, but in one embodiment of the present invention, the generated steam pressure when the plant output is 38 is set to the control setting value of 0.7 kq 7cm2 according to the prior art,
A function generator 35 generates a signal that increases the set value as the plant output decreases so that it becomes 3 kg/cI'r12 when the plant output is 0, and this signal is given as a cascade setting signal to the controller 30.

In this case, the heating steam pressure is controlled to be constant (3 kq/cm2) by the controller 29 when the plant output is from O to about 19.
When the plant output is approximately 19 to 38, the generated steam pressure is variable controlled by the controller 30 (setting value cascade setting).

As explained above, according to the present invention, the internal pressure of the gland steam generator is increased at the time of starting the steam turbine compared to the conventional technology.
2, the present invention can generate 1.81 cq/cm2), which increases the amount of heat retained in the gland steam generator. Even at times, there is no shortage of ground steam.

Therefore, this switching of the ground steam can be easily carried out by setting the controller 31 to automatic mode, switching the station steam side controller 33 to manual mode, and gradually closing it.

Note that the plant output signal 3 applied to the function generator 35
4 may be a value that changes proportionally to the plant output, such as a signal representing the extraction pressure of the steam turbine or a signal representing the feed water flow rate, or may be another program signal.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the piping system of a nuclear turbine plant equipped with a ground steam generator to which the present invention is applied, Fig. 2 is a detailed view of a part of Fig. 1, and Fig. 3 is a diagram showing the implementation of the method of the present invention. FIG. 4 is a diagram showing the operating characteristics when the grand steam generator is operated with the configuration shown in FIG. 3. 2... Steam turbine, 5... Grand steam generator, 5N... Heater, 5B...
Main body, 6... In-house boiler, 12... Main steam pipe for heating, 14... Turbine bleed pipe, 19
・・・・・・Generating steam pipe.

Claims (1)

[Scope of Claims] 1. A grand steam generator having a main body into which condensate from a nuclear turbine plant is introduced, and a heater housed within the main body into which nuclear reactor generated steam and bleed air from the nuclear turbine are introduced. In the control method, when starting up the nuclear turbine, reactor-generated steam having a pressure sufficiently higher than the minimum required steam pressure necessary for generating steam in the ground steam generator is introduced into the heater, and the heating The bleed air is supplied through a check valve, and when the heating steam pressure on the main steam side decreases, it is automatically supplied to compensate for this, and the reactor generated steam introduced into the heater is In a low load region, the heating steam pressure of the grand steam generator is controlled to a constant value, and in an intermediate load region, the generated steam pressure of the grand steam generator is controlled to continuously change in inverse proportion to the output of the nuclear turbine plant. . A method for controlling a grand steam generator, characterized in that the introduction of reactor generated steam to the heater is stopped when the generated steam pressure of the grand steam generator becomes equal to a final setting value. 2. first means for introducing reactor-generated steam into said heater of a gland steam generator having a body into which nuclear turbine brand condensate is introduced and a heater housed within said body; , for detecting the pressure of the reactor-generated steam introduced into the heater with a first valve provided in the first means, and controlling the first valve so that the pressure becomes a specified value; with the first pressure regulator. a second means connected to the heater for introducing bleed air from a nuclear turbine into the heater through a check valve to compensate for a drop in heating steam on the main steam side; and detecting the steam pressure generated within the main body. and a second valve that generates a signal for controlling the first valve so that the generated steam pressure becomes the cascade set value by comparing it with a set value separately given as a cascade signal, and performing control calculations based on the deviation. and a controller that compares the output of the first pressure regulator and the output of the second pressure regulator and controls the first valve according to the result. In the control device that controls the equipment. a device that is connected to the second pressure regulator and changes the set value of the second pressure regulator in inverse proportion to the output of the nuclear turbine plant; A control device for a grand steam generator, characterized in that the control device automatically switches to turbine bleed air when the pressure falls below bleed air pressure.