JPH0351602A - Operation support apparatus - Google Patents

Abstract

PURPOSE:To improve reliabilities without requiring skill by predicting future values of thermal stress of a heat exchanger outlet header and a gas-water separator by respectively appliying heat transfer rates corrected by the use of temperature distribution in thickness directions to obtain heating-up rates, pressure-rising rates and command values thereof respectively at the present time in an operation support apparatus of a steam generator etc. CONSTITUTION:On receipt steam temperature present value signals 17 and valve-opening signals at the present time 10, 13, 18, a first arithmetic means 27 outputs steam temperature future value prediction signals 37. Based on these signals 37, arithmetic means 28, 30 successively predict quantities of heat transfer and thermal stress, whereby an arithmetic means 31 outputs heating-up rate limiting value signals 41 to an optimum control variable computing means 32. The means 32 determines deviations between heating-up target temperature signals 38 and the signals 17 to output, based on the deviations, excessive steam, discharge valve actuation signals 10, fuel flow control valve actuation signals 13 and excessive steam feed valve actuation signals 18 within the range of the signals 41. In this manner, reliability can be improved without requiring skill.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an operation support device for steam generation equipment, etc., and in particular, to maintain high reliability of the equipment while frequently controlling steam temperature,
The present invention relates to a driving support device suitable for operations involving pressure changes.

[Conventional technology]

FIG. 3 shows an example of a heat exchange part of a steam generation facility to which the present invention is applied and an instrumentation system based on the prior art.

The steam to be superheated 1 is led to the heat exchanger heat exchanger tubes 5 via the heat exchanger inlet header 4 . The heat transfer tube 5 regulates the fuel from the fuel supply line 11 with a fuel flow control valve 12,
The steam passing through the heat exchanger tubes 5 is superheated and then sent to the superheated steam supply line 23 via the heat exchanger outlet header 6. At this time, the amount of superheated steam in the supply line 23 generated by the steam generation equipment is adjusted by the opening degree of the superheated steam supply valve 9, and the surplus steam at this time is discharged by the surplus steam discharge valve 2. Further, the temperature of the steam generated in this equipment is adjusted based on the measured value by the temperature detector 7 by adjusting the amount of fuel supplied to the parner 14 according to the flow rate of steam passing through the heat transfer tube 5.

In this steam generation equipment, if it is necessary to frequently change the steam temperature and flow rate in the superheated steam supply line 23, care must be taken in terms of equipment reliability. In other words, not only when changing the steam temperature intentionally, but also when changing the steam flow rate, it is necessary to precisely adjust the change in the amount of heat exchange in the heat transfer tubes 5 in response to the change in the steam flow rate. This causes steam temperature fluctuations and thermal stress in the containers that make up the equipment. Fatigue damage and creep damage caused by the thermal stress may eventually lead to cracking and explosion of the container.

In order to deal with such concerns, the thermal stress of the heat exchanger outlet header 6 is also monitored in the prior art.

This is because such a header is thick-walled and generates significant thermal stress essentially due to the metal temperature distribution, and in the unlikely event that cracks occur, it will This is a representative example of thermal stress in equipment that generates superheated steam. This is because it is suitable as a monitoring point.

Implementations of thermal stress monitoring based on prior art techniques are described, for example, by Miyagaki. Hodozuka: Boiler thermal stress monitoring device: Hitachi Review Vol. 65, No. 6, P3
91 (Sho 58-6), the method for calculating thermal stress can be summarized as follows.

In general, it is known that the temperature distribution of a cylindrical container such as a header can be determined by solving an axially symmetric one-dimensional heat conduction equation, since the length of the cylindrical portion is sufficiently long relative to the wall thickness. Shown in 2.

・・・・・・・・・(1) C K= ・・・・・・・・・(2) μ　ρ Here, the following symbols are given.

L Two hours elapsed (sec) ρ: Metal density (kg/m!) θ: Metal temperature [°C] k: Metal temperature conductivity (m"/sec) ': Distance in the radial direction of the cylindrical container (m) C: Metal thermal conductivity (kcal/m-sec・”C
) μ: Specific heat of metal (kcal/kg ・”C) Regarding the difference in how to give the boundary conditions when solving the differential equation (1),
Three types of embodiments can be shown, which will be described later.

By solving the differential equation (1), the metal temperature distribution at time t can be obtained as a function of r, θ(r, t), but the average temperature of the container is the same temperature θ(r, t), depending on the value of r.
t) Since the volumes in the vicinity are different, it is necessary to take this into consideration when calculating. This average metal temperature 0 is called the volume average temperature and is given by the following equation.

rm Here, subscripts a, ...... (7) b indicate the inner and outer surfaces of the cylindrical container, respectively. Therefore θ. = θ (rs, t), θ5 - θ (r
b, L).

It is generally known that the thermal stress on the inner surface of a cylindrical container is the most severe, and this can be calculated as follows.

σ,,=0 ・・・・・・・・・
...(8) Give the following symbol here.

μ: Metal linear expansion coefficient (1/”C) η: Metal Young’s modulus (kg/mm”) ν: Metal Poisson’s ratio σt: Internal thermal stress (kg/rrrm”) Also, subscript r,
s and z indicate the radial, circumferential, and axial directions, respectively.

Furthermore, in a pressure vessel, internal pressure stresses must be taken into account, and these are shown in Figure 2 below.

lυυ ・・・・・・・・・(11) ? The following symbol is given here.

σ. : Internal internal pressure stress (kg/mm") P, : Fluid pressure inside the container (kg/cm") Heat exchanger headers, steam separators, etc. have heat transfer tubes and communication pipes connected to the side of the cylindrical container. Its tip can be considered a nozzle. As is known, when there is a nozzle-like hole on the inner surface of a cylindrical container, the stress value is particularly high at a part of the corner of the hole, but this value is lower than the stress on the inner surface of the container without the nozzle-like hole. Since the stress can be evaluated by multiplying the value by the stress concentration constant, the stress at a part of the corner of the nozzle-shaped hole can be obtained as follows.

σ,=K,σ■ σ,=Ktlσ. +K■σp. σ8=K. σ,,+K. ,σ■ Here, the following symbols are given.

σ: Partial total stress of nozzle corner (kg/mm2)...
・・・・・・・・・(12) ・・・・・・・・・(l3) ・・・・・・・・・(14) Kt: Thermal stress concentration coefficient Kp: Internal pressure stress concentration coefficient As shown above Since the calculated part of the nozzle corner is the part of the container where the stress value is the most severe, it is sufficient to evaluate damage related to the generated stress in this part. As is well known, induced damage is determined by the maximum absolute value among the three parts of the principal stress difference, and creep damage is determined by the equivalent stress value, and these quantities are determined by the following formulas.

σ,2=σ3−σ2 ・・・・・・・・・
...(15)σ2r=σ2−σ, ・
・・・・・・・・・(16)σ,,=σ,−σ,
・・・・・・・・・(17)・・・・・・・
... (18) Here, define the symbol for lower two.

δsz: Principal stress difference (circumferential uniaxial force) (kg/mm2
) δzr: Principal stress difference (axis - radius) (kg/mm
”) δrs: Principal stress difference (one round of radius) (kg/m
m”) δeg: Equivalent stress (kg/mm
”) In applying the above-mentioned equations, as mentioned above, there are various examples regarding how to give the boundary conditions of equation (1), each with its own characteristics, and the structure shown in Figure 3 is as follows. This is a typical structure called Type 1.

After describing Type I in detail, FIG. 4, hereinafter referred to as Type ■, and FIG. 5, hereinafter referred to as Type ■, will be explained.

Type ■ follows the concept below. In FIG. 3, since the outer surface of the header 6 is surrounded by the heat insulating material 20, it is assumed that no heat enters or exits from the outer surface. Therefore, since the amount of heat transfer per unit area of the outer surface can be expressed using the temperature gradient of the metal, the following equation is obtained.

Similarly, since the amount of heat transfer on the inner surface is equal to the amount of heat transfer between the inner surface and the fluid inside, we obtain the following for unit area.

Here, the following symbols are defined.

α: Heat transfer coefficient between metal and fluid [kcaI/Illz・s
ec.゜cθf: Average fluid temperature [゜C] In type 1, while giving θr momentarily, (1)
Solve the equation by combining it with equations (19) and (20).

Specifically, the fluid temperature signal l7 obtained by the temperature detection means 7
As θr, the second calculation means 107 calculates the right-hand side of equation (20), and together with the boundary condition of equation (19), which already assumes the value of the right-hand side, the third calculation means 109 solves equation (1). By giving.

The value of the heat transfer coefficient α in equation (2o) handled in the second calculation stage 107 is an important parameter that governs the calculation accuracy of the thermal stress value, and in the conventional technology, it is determined as follows.

] ・・・・・・・・・(2l) Uf Din Re= (22) ζf Gf uf= (23) n πD1・Pf 4 Here, the following symbols are defined.

λf: Internal fluid thermal conductivity (Kcal/m-sec-'C
) Din: Representative dimension (channel inner diameter) [m] Nuf: Internal fluid Nusselt number Ref; Internal fluid Reynolds number Prf: Prandtl number ur: Internal fluid flow velocity (m/sec) ζf: Internal fluid dynamic viscosity coefficient (m”/ sec) Gf: Total internal fluid mass flow rate (Kg/S) n: Number of circuits π: Pi ratio Pr: Internal fluid density (kg/m') Equation (21) is called the McAdams equation, and the details are Please refer to appropriate references (for example: Giedt; Translated by Yokobori, Kuga: Basic Heat Transfer Engineering: Maruzen). In the formulas, n, D
in is determined from the structure of the header 6, Gf is determined from the operating state of the steam generation equipment, and λ'+Prf, ζf, Pf can be determined using the steam table published by the Japan Society of Mechanical Engineers, if the temperature, pressure, and dryness of the internal fluid are known. You can know. Based on these quantities, the values of all variables related to equations (21> to (23)) can be calculated.

In accordance with the above idea, in the embodiment of type (2), the thermal stress current value signal 110 is calculated, and the fluid temperature signal 17 from the temperature measuring means 7 is configured by the screen editing means 111 into a screen that is easy for the operator to understand. is displayed on the display 26. The operator monitors the display 26 and sets the signal setting devices 101 and 10 so that the thermal stress value does not exceed the specified value.
2, and 103.

In addition, 3 in the figure is an excess steam discharge line, 104 is a superheated steam supply drive signal, 105 is a fuel flow control valve drive signal, and 106
is the surplus steam discharge drive signal, 10B is the current value signal of the amount of heat transfer,
112 is a display drive signal. FIG. 4 shows an embodiment of type (2). Since most of the device configuration and the concept of calculation are the same as type (2), only the differences between the two will be explained. In addition, in FIG. 3 and FIG. 4, the same part numbers are given to the structural elements that perform the same function.

The biggest feature of Type■ is that it uses a metal temperature detector 8,
Outer surface temperature θ. This means that a signal l6 is obtained that gives the following. Type ■ is based on a method of directly solving the temperature distribution using the actually measured θ, as the boundary condition of equation (1), without assuming the condition of the header outer surface insulation related to the heat insulating material 20 of equation (19). In particular, in the case where the heat insulating material 20 is insufficiently thick and a considerable amount of heat is dissipated into the atmosphere from the outer surface of the head 6, an effective improvement in accuracy can be expected compared to type (2).

However, in normal steam generators, a sufficiently thick insulator is usually implemented from the viewpoint of both heat loss prevention and safety during contact, and type H as well as type I (20 ) remains the most important factor governing the thermal stress calculation accuracy.

FIG. 5 shows an embodiment of type (2). Since most of the device configuration and the concept of calculation are the same as Type I and Type II, only the differences will be explained. Components that perform the same function are given the same part numbers as in FIGS. 3 and 4.

The biggest feature of Type ■ is that it uses a metal temperature detector 118 to measure the inner surface temperature θ. A metal temperature signal 119 near the inner surface that can be considered as θ. (20) including α by solving equation (1) directly using the value of as a boundary condition.
The advantage is that no formula is required.

It is true that the calculation of α basically has to rely on equation (21), which is an experimental formula, so the calculation method of type (2), which does not use α, which is inherently prone to errors, has an advantage. However, in addition to the difficulty in developing calculations for predicting future thermal stress values, which will be described later, the temperature gradient is generally steep near the inner surface of the thick part of the header 6, so even if measurements are taken near the inner surface, There is a problem in that errors tend to occur due to the exact temperature of the phase surface.

The conventional instrumentation technology has been explained above using a heat exchanger outlet header as an example. However, in a steam generator, the steam separator or steam drum is also thick-walled, so in the event of a crack, Fatigue damage caused by thermal stress that is difficult to replace. This is the area that requires the utmost care for creep damage. In such parts, since the fluid inside is a mixture of air and water, the saturation pressure uniquely corresponds to the fluid temperature, so it is common practice to manage the pressure using the pressure value or the rate of pressure change. This is because pressure is generally easier to measure and control than temperature.

FIG. 6 shows an example of a steam/water separation section of a steam generation facility and an instrumentation system based on the prior art. The water supplied from the water supply line 5l receives heat from the flame 63 in the evaporation tube 52 and generates steam, becoming a mixture of air and water. The steam/water mixture is blown into the steam/water separator 53 from the nozzle 54 along the inner wall of the steam/water separator 53 in a direction along the inner surface so as to form a swirling flow. On this occasion,
The liquid phase having a large specific gravity is pressed against the inner surface of the steam/water separator by centrifugal force, falls while rotating, and is discharged from the drain outlet 56. Since the gas phase with low specific gravity is less affected by centrifugal force, it gathers in the center of the steam-water separator and is sent to the steam supply line 58 via the steam supply valve 57. The steam pressure in the equipment depends on the amount of steam extracted by the steam supply valve 57.
This is done by adjusting the fuel flow regulating valve 64 to adjust the amount of evaporation in the steam pipe 52.

In the prior art instrumentation system, a steam saturation temperature signal 67 is determined from a steam pressure signal 82 obtained by a steam pressure detector 59 using an arithmetic means 78 that incorporates a functional form of steam pressure and saturation temperature.

The following steps are similar to those shown in FIG. 3, which is a prior art instrumentation system for a heat exchange outlet header. In this device, the thermal stress current value signal 158 is received, and the pressure measuring means 59
The screen editing means 159 converts the fluid pressure signal 82 by
Display 75 is configured to be easy for operators to grasp.
to be displayed. The operator monitors the display 75 and operates the signal setters 151 and 152 so that the thermal stress value does not exceed a specified value.

In the figure, 153 is a steam supply valve drive signal, 154 is a fuel flow control valve drive signal, 155 is a second calculation means, 156 is a heat transfer current value signal, 157 is a third calculation means, and 160 is a display drive. It's a signal.

The device shown in FIG. 6 belongs to the above-mentioned type (2) in terms of thermal stress calculation method, like the device shown in FIG. Of course, it is also possible to apply the method of type (2) similar to the device and the method of type (2) similar to the device of FIG. An example of the structure of the type ■ and type ■ of the steam/water separator 53 is based on FIG. 6, and if the differences between FIGS. Since it can be easily inferred, the explanation will be omitted.

The common feature of the conventional instrumentation systems explained above is that they all monitor only the current value of thermal stress occurring in the thick-walled parts that are the target of management, and based on that information, they rely on the skill of the equipment operator to control the equipment. This means that the operation is being carried out.

In other words, the occurrence of thermal stress is essentially caused by the development in which changes in the fluid temperature inside the container are delayed in the direction of the thickness of the container metal. Even if the increase in fuel input amount is stopped after learning of the high stress value, the thermal stress value generally continues to increase for a while.

Therefore, problems will inevitably arise in the operation of the equipment if the current thermal stress value is not considered and the thermal stress value related to the current equipment operation is not foreseen. It requires.

Furthermore, as mentioned above, when the accuracy of monitoring the current value of thermal stress in the conventional technology depends on the reliability of calculating the heat transfer coefficient on the inner surface of the container, a certain amount of error must be assumed, and this should be considered. Obtaining an estimate of future values of thermal stresses, including operating the equipment, requires a high degree of skill.

In conclusion, the above-mentioned points can be solved with a function that predicts the future value of thermal stress based on the operating status of the equipment up to the present time. It is already known that this can be achieved by applying the method as a prediction simulator that sequentially advances time into the future under appropriate boundary conditions.

However, such prediction of thermal stress values has not yet been put to practical use due to the following problems. 1) In the thermal stress calculation methods of type I and type II, the accuracy is controlled by the heat transfer coefficient α of the inner surface of the container, but the calculation of α, including the typical equation (21), assumes that the internal fluid is a single-phase flow. , based on idealized assumptions such as an infinite elliptical tube,
In prediction calculations that require successive time advances and repeated use of α, errors due to α accumulate. Valid thermal stress evaluation is often not possible.

2) Type ■ thermal stress calculation method does not use α, which causes the error mentioned above, but requires the temperature of the inner and outer metal surfaces of the thick-walled container as a boundary condition. There is no problem in calculating values, but it is difficult to apply to predicting future values.

In other words, the thick-walled container is a passive part, and the internal and external metal temperatures are determined as a result of being influenced by the temperature of the internal fluid supplied from other heat exchange parts and the amount of fluid extracted from the container. Without taking this physical mechanism into account in calculations, it is impossible to accurately determine future values of metal temperatures on the inner and outer surfaces of thick-walled parts. However, if we consider this physical mechanism,
It becomes necessary to calculate the heat transfer between the fluid inside the container and the inside surface of the container, and this calculation requires a considerable number of parameters, so prediction calculations that cannot be applied to actual measured values have the same drawbacks as Types I and II. is unavoidable.

The purpose of the present invention is to provide the most effective method in terms of easily realizing operations that involve frequent changes in steam temperature and pressure while maintaining high reliability of equipment, which in the prior art relied only on the skill of operators. Our goal is to provide a driving support system centered on highly accurate prediction of future values of thermal stress, which will serve as a means of practical use. It comes down to solving the error problem.

[Means to solve the problem]

In order to achieve the above object, the present invention is characterized by comprising the following means 1) to 7).

1) Means for predicting the future value of the steam temperature in the heat exchanger outlet header, means for predicting the future value of the amount of heat exchange between the steam and the header using the future value of the steam temperature, and the future value of the amount of heat exchange. 2) Regarding the steam/water separator, a method for predicting the future value of the fluid temperature, the future value of the heat exchange amount, and the future value of the thermal stress on the interior surface of the steam/water separator in the same manner as in item (■). 3) A means for displaying the relationship between the predicted thermal stress value of the heat exchanger outlet header and the current temperature increase rate; 4) A means for displaying the relationship between the predicted thermal stress value of the steam-water separator and the current pressure increase rate. 5) Means for determining a temperature increase rate command value in accordance with a thermal stress prediction value of a heat exchanger outlet header; 6) Means for determining a pressure increase rate command value in accordance with a steam water separator thermal stress prediction value; 7) Heat Using the current value of heat exchange amount with internal steam or fluid for each exchanger outlet header and steam/water separator,
A means for calculating the current temperature distribution value in the thickness direction of the header or separator, a means for measuring the metal temperature on the outer surface or inside the thickness of the header or separator, and a means for calculating the current value of the temperature distribution in the thickness direction of the header or separator. Means for comparing and correcting the heat transfer coefficient α related to the calculation of the current value of the heat exchange amount, and means for applying the corrected heat transfer coefficient α to the calculation of the future value of the heat exchange amount in items 1) to 6).

[Effect]

The operations of the above-mentioned means 1) to 7) are roughly as follows.

The method for predicting the future steam temperature or fluid temperature in items 1) and 2) may be calculated using a simulation analysis method using a physical model according to the operating conditions given to the boiler. Specifically, the method based on the authors' research [References: Haka Miyama, "Development and Application of Boiler Plant Simulator": Thermal and Nuclear Power Generation Vol. 37, No. 11, P1189-P
1199 (Sho 6 1-1 1)) may be applied.

The calculation method for calculating the future value of thermal stress from the future value of steam and fluid temperature is the method mode in which the current value of thermal stress was calculated in the explanation of the conventional technology ■ [Explanation regarding equations (1) to (23)]
Starting from the current value of thermal stress, the thermal stress value at that point is calculated based on the steam and fluid temperature predicted at appropriate calculation time intervals (usually about 0.1 seconds to 10 seconds). can. In such calculations, α (used in equation (20)) when determining the amount of heat exchange from the steam and fluid temperature is corrected as described below according to the means in section 7) to ensure sufficient accuracy for practical use. .

Regarding items 3) and 4), it is known that the thermal stress value generated in the container is a high-order lag characteristic of the internal fluid temperature change rate, and the theoretical support for this phenomenon is based on the invention of the present inventors. This is as detailed in the specification of "Boiler Control Device" (Japanese Patent Laid-Open No. 118503/1983).

Generally, in order to maintain the reliability of pressure vessels, the maximum value of thermal stress that occurs must be limited, but due to the above-mentioned characteristics, the maximum value of thermal stress that will occur in the future is controlled by the current rate of temperature change, so heat exchange By predicting the future value of the thermal stress of the outlet header, it is possible to evaluate whether the current temperature increase rate is appropriate so as not to exceed the control value.

Similarly, in a steam/water separator, the internal fluid is in a saturated region and there is a one-to-one relationship between saturation temperature and pressure, so temperature is generally obtained as a function of pressure, which is easy to measure. Therefore, the future maximum thermal stress value of the steam/water separator will be controlled by the current pressure increase rate, and the validity of the current pressure increase rate can be evaluated from the predicted value of thermal stress.

Regarding items 5) and 6), in general, when changing the steam conditions (m degrees and pressure) of steam generation equipment, for example, the "boiler control device" invented by the present inventors) JP-A-61-24
905) to command an appropriate temperature increase rate and pressure increase rate, but in this case, the future thermal stress height is predicted at the temperature increase rate and the temperature increase pressure rate. If so, such adjustment can achieve the effect of reducing the absolute values of the temperature increase rate and pressure increase rate command values so that the predicted value becomes less than the limit value. Here, the temperature increase rate and pressure increase rate command values become O when the steam temperature and pressure respectively match the target values, and generally can be either positive or negative.

Regarding item 7), in the above-mentioned calculating means for calculating the future value of thermal stress from the future value of the fluid temperature, the external surface of the header or the steam/water separator or the Calculate the current value of metal temperature in thick wall. Since the metal temperature calculation is obtained when equation (1) is solved in the process of calculating the thermal stress value, the thermal stress calculation calculation section can be used as is.

Compare the metal temperature calculation value and the corresponding actual measurement value, and if the temperature calculation value has a leading change (advanced in phase) compared to the actual measurement value under various operating conditions, it will control the accuracy of the calculation. The aforementioned heat transfer coefficient α ((20) Equation 1 is too large, and conversely, if it changes with a delay compared to the actual measurement value, α is too small. Therefore, paying attention to this tendency, α should be corrected successively. Therefore, due to the effect of item 7), l)
The effects of items 6) to 6) can be realized with sufficient accuracy for practical use.

[Embodiment of the Invention] FIG. 1 shows an operation support system that monitors a heat exchanger outlet header, which is an embodiment of the present invention.

This system is not compatible with any of the instrumentation systems shown in the prior art shown in Figure 3 (Mode I calculation method), Figure 4 (Mode ■ calculation method), and Figure 5 (Mode ■ calculation method). It was developed to solve the problems that existed. To explain this system, Figures 3 and 4 are related to the prior art. The same parts as in FIG. 5 are given the same reference numerals.

In the figure, 1 is superheated steam, 2 is an excess steam discharge valve,
3 is an excess steam discharge line, 4 is a heat exchanger inlet header, 5 is
is a heat exchanger heat transfer tube, 6 is a heat exchanger outlet header, 7 is a steam temperature detector, 8 is a metal temperature detector, 9 is a superheated steam supply valve, 10 is an excess steam discharge valve drive signal, and II is a fuel supply line , ■2 is the fuel flow control valve, l3 is the fuel flow control valve drive signal,
l4 is the burner, l5 is the flame, 16 is the metal temperature signal, 1
7 is a steam temperature signal, l8 is a superheated steam supply valve drive signal, l
9 is a second calculating means, 20 is a heat insulating material, 2l is a sixth calculating means, 22 is a seventh calculating means, 23 is a superheated steam supply line, 24 is a third calculating means, 25 is a screen editing means, 26
is a display, 27 is a first calculation means, 28 is a second calculation means, 29 is a state quantity correction signal, 30 is a third calculation means, 31 is a fourth calculation means, 32 is an optimum operation amount calculation means, 33 is a signal setting device, 34 is a heat transfer amount current value signal, 35 is a metal temperature current calculated value signal, 36 is an arithmetic value correction signal,
37 is a steam temperature prediction signal, 3rd is a steam temperature increase target signal, 39 is a heat transfer amount prediction signal, 40 is a thermal stress prediction signal, 4l
42 is a steam temperature change rate limit value signal, 42 is a thermal stress current value signal, and 43 is a display drive signal.

The system shown in FIG. 1 includes a steam temperature current value signal 17, and valve opening degree signals 10, 13.
8 is received and input to the l-th calculation stage 27 for obtaining a steam temperature future value prediction signal 37. Since future predicted values are calculated at intervals of the calculation step width, the prediction signals 37 are output in the number obtained by dividing the future prediction application time width by the calculation step width. For example, if prediction is made 10 minutes into the future with a calculation step width of 30 seconds, 20 prediction signals will be output.

The second calculation means 28 receives the steam temperature future value prediction signal 37 and calculates a heat transfer amount prediction signal 39 at each corresponding time point. Since the heat transfer coefficient α is used in this calculation, the second calculation means 28 also inputs a correction signal 36 for α, which will be described later.

The third calculating means 30 receives the heat transfer amount prediction signal 39 and obtains a thermal stress prediction signal 40 at each corresponding time point. Further, the fourth calculation means 31 receives the thermal stress prediction signal 40, and
A current temperature increase rate limit value signal 41 is output to prevent the thermal stress value from exceeding the limit value in the future.

The optimum operation amount calculation means 32 receives the temperature increase target temperature signal 3 days and the current steam temperature signal l7, and calculates, according to the deviation between the two signals,
Limit value (absolute value) given by heating rate limit value signal 4l
Excess steam discharge valve drive signal 1, which is the plant operation amount within
0, the fuel flow control valve drive signal l3 and the excess steam supply drive signal 18 are calculated.

On the other hand, as a precautionary measure to ensure the practical accuracy of the above prediction calculation, the second calculation means 19 uses a steam temperature current value signal l9.
7 to obtain the current heat transfer value signal 34, and the sixth calculation means 21 calculates the metal temperature distribution in the wall thickness direction of the heat exchanger outlet header, and calculates the metal temperature distribution in the thickness direction of the heat exchanger outlet header, and A temperature current calculated value signal 35 is calculated. The seventh calculating means 22 receives the corresponding measured metal temperature signal 16 and calculated value signal 35, and calculates a calculated value correction signal 36 that performs necessary corrections including the aforementioned heat transfer coefficient α.

The thermal stress current value signal 42 is calculated from the heat transfer amount current value signal 34 using the third calculation means 24, and is sent to the screen editing means 2 together with the thermal stress future value prediction signal 40 and the steam temperature current value signal 17.
5 and then displayed on the display 26.

The action of the first calculation means 27 is a predictive simulation based on a physical model, and as mentioned above, details can be found in the reference literature (Thermal and Nuclear Power Generation Vol. 37, No. 11, pages 1189 to 119).
Please refer to 9).

The second calculation means 19 and 28 are based on the above-mentioned equation (21), (2
2) Calculate equation (23>), and calculate the amount of heat transfer in the second step based on equation (20>).

・・・・・・・・・(24) α0 = α・δ ・・
・・・・・・・・・(25) Here, the following symbols are defined. q: Heat transfer amount per unit length in the inner axial direction [kcal/m-
sec] α2: Heat transfer coefficient after correction [kcal/m”-s
ec·'C] δ: Heat transfer coefficient correction coefficient [-] Of these, the heat transfer coefficient correction coefficient δ is given by a seventh calculation means to be described later.

The sixth operation stage 21 calculates the metal temperature distribution θ(r) in the thickness direction by solving equations (1) and (2), and
The metal temperature θ,=θ(rp,t) corresponding to the measurement point used by the seventh calculation means 22 is determined.

The third calculation means 24 and 30, in addition to solving equations (1) and (2) similarly to the sixth calculation means 21, calculate equations (7) to (18) related to thermal stress calculation.

When solving equation (1) among the above operations using a digital computer, it is efficient to use the following method. Expanding equation (1) into central difference form allows approximation to the following equation.

θ(r+Δr, t+Δ0−θ(r,t)Δm Δr ・・・・・・・・・(26) The following symbols are defined here.

r▲=r, + (Δr)i (i=1....n) ・
...(27) tJ=to + (Δt)j (j”1,
... m) ”・(2B) θ1, = θ(ri, t7
) ・・・・・・・・・(29〉n) The above formulas assume that the heat exchanger outlet header and the steam/water separator are cylindrical thick-walled containers, and the container is divided concentrically into n sections. It is derived on the assumption that the metal temperature is constant.It is known that if n=10 or so, the accuracy is sufficient for practical use.

Δr is the thickness of the section, and Δt is the calculation step width described above.

Equation (26) can be simplified to the following form.

gi θ Ben-1+j◆I − `` . θ 5・
5 ◆ Heavy + θ i・1 j ◆ Neck = 1 g 5 θ + - +.
) + h 5th θ 1 θ 1 river j (31) Here, the following symbols are defined.

1 1 1 ■ Δr 2r▲? 31) In the equation, ft, gt+ht are constants, so on the right side, time 1. =1. , the value θj−1+j l
θ． ,j. θ1. ．． If is known, the right-hand side becomes a constant, and
As a simultaneous equation, t. =Lj** value θI-1n
It is possible to obtain j1+θl+j■ and θi41+j■.

Therefore, 1 = 1 j. Substitute the value of , on the right-hand side? Then, in the same way, 1 = 1, . Since the value in (1) can be calculated, the future value of the temperature distribution can be calculated sequentially using this method, and the future value of the thermal stress can be calculated sequentially by applying the temperature distribution to equations (7)2 to (18) at each point in time. can do. Note that the solution method using equation (31) is called the Crank-Nicholson method, and stable calculation is possible even for relatively large Δt. For details on the Crank-Nicholson method, please refer to appropriate references [e.g. GD Smith; Translated by Fujikawa: How to solve partial differential equations using a computer: Science Publishing (1973-
1)].

As mentioned above, the method for solving equation (31) as a simultaneous equation will be slightly supplemented below.

Formula (3l) can obtain nfi court formulas corresponding to the number of divisions, but in this case, the unknowns are θ−. ．． 1,θoj・
1 to θnj-1θ+s+Ij+l, n+3f.

This is handled as follows.

Expressing equation (l9) in central difference form is as follows.

2λr Therefore, it becomes lower two. This equation also holds at time j+l.

θ+1. ．． J=θn-1+J...
(36) Similarly, when formula (24) is expressed in central difference form, the following formula is derived.

・・・・・・・・・(37) In the above formula, from the definition, θ. =θ. , was used. Also, θ,j is the current θ,. For , the actual measured signal 17 is shown, and for the future value, the predicted value at time j calculated by the first calculation means (the j-th {i in the signal 37) is shown. From equation (37), we obtain lower 2.

(38) Since equation (38) also holds true at time j+l, using equations (36) and (38), of these, θ−. ．． , and θ**Ij+1 can be eliminated, so (3
l) Is it possible to solve equations as simultaneous equations? be. As the seventh calculation means 22, for example, the signal 35 and the signal l6
In the control device, the deviation is input to a general PI controller (
Various methods can be considered, such as finding δ in equation 25) and applying fuzzy control theory or knowledge engineering, but in this embodiment, an example will be introduced in which extended Kalman filter theory is applied. The advantage of this method is that, in general, there is no guarantee that the value of δ will converge to a theoretically meaningful value in the methods using the above-mentioned PI adjuster, fuzzy control, knowledge engineering, etc., but because it uses Kalman filter theory, It can be pointed out that there is a guarantee that δ converges to an optimal value in the sense of minimum variance and unbiased estimation.

For details on the Kalman filter theory, refer to appropriate references [e.g. Katayama: Applied Kalman Filter; Asakura Shoten (1984-4
)), and the main points for applying the theory to the present invention will be described below.

Equations (3l), (36), and (3B) can be expressed as follows using matrix representation.

A''/IF■,=A'''&k+B”θ■...
・・・・・・(39)yk 10δk ・・・・・・・・・(40〉) Here, various quantities are defined as follows.

・・・・・・・・・(42) ・・・・・・・・・(44) In the above formulas, y is the observation vector, and the temperature detector 8
The dimension of the vector is equal to the number of detectors 8 provided at different depths of the thick vessel, including the outer surface.

In particular, when there is only one detector 8, y is a scalar, but the following handling is the same. ? k has as a component the value of the current calculated value signal 35 corresponding to yk.

In the subsequent development, the symbol ' is used to distinguish estimated values obtained as a result of various operations from corresponding actual measured values.

/? is the state vector at the next point k, which has the metal temperature at each of the above-mentioned dividing points and the outer surface from the inner surface of the thick-walled container. When the metal temperature distribution is estimated by applying corrections, etc., which will be described later, the above symbol is used to represent the layer. The matrix C represents the correspondence between the precepts of δ and the precepts of 2k (40)
It is given by the formula. That is, it is only necessary to consider that among the precepts of the layer, only the object to be compared with the measured value signal 16 is extracted using equation (40).

The power of A1 shown in equation (42) is r. , g. Everything? Since A'' is a so-called fri-diagonal matrix, there is an inverse matrix (A'')-', and the inverse matrix can be easily obtained by using the sweep method etc., so (
39) The formula becomes lower 2/? picture. 1 =Aθk+Bθ■ ・・・・・・
...(50)A= (A")-1A"
・・・・・・・・・(51)B=(A”)−1B
” ・・・・・・・・・(52) In the above formula, A and B are called transition matrix and driving matrix, respectively, in system theory.Here, both A and B include α1 in the precept (
From equations 2 1), (2 2), (2 3) and (25), α9 is δ, λf + Dill+ Prf,
It is a function of hf +P. Also, (3 2), (3
3), fi which is another precept of A and B from formulas (34)
+ gi , }li are functions of K, Δr, Δm. However, among these parameters, other than δ can be determined definitively at time k using the actual measurement value or the first calculation means 27, including the process of prediction calculation, whereas δ is determined by the metal value at each time point. The temperature estimation error is an unknown parameter to be minimized. Are parameters other than δ properly calculated in the following discussion? Therefore, for simplicity, consider A and B to be functions of only the unknown parameter δ. At this time, it is shown in the formula below.

/? Defining an extended state variable Z having ■ and δ5 as precepts is as follows. However, it is assumed that the true value of δ is a constant value, but the estimated value 3k changes from time to time while converging slightly.

・・・・・・・・・(54) )/f = (c; o)Z,=# (z*)・・
(55) To estimate Z by applying the extended Kalman filter theory to the above vector functions ψ(z.,k) and φ(Zk), the following equations may be calculated.

・・・・・・・・・(56) 1 2Δδ [(A (&k+Δδ) A(3, Δδ)} Button+ {B(,}k+Δδ)−B(&k−Δδ)}θ,,
]・・・・・・・・・(57) 2 l+− + = 6 k( 2 k)Qw=”;l
w+Kw (!/K-Qi+)2k=φm(zm) K. = 100 mHm” (Hhνk}{k'+Rk) 100k・.
=FKPkF,” ・・・・・・・・・(59) ・・・・・・・・・(60) ・・・・・・・・・(6I) ・・・・・・・・・( 62) ・・・・・・・・・(63) P1101FkHkT CHk100, Hy” + Rh)
One year old? ,・・・・・・・・・(64) The above equations are calculated using the initial values of 2k and 100, the calculation error, and the degree of error accompanying the approximation of the physical phenomenon related to the model formula as a covariance matrix at each point in time. R in k. If it is given as Q*, then at each time point, each time C related to the measurement signal l6 is obtained, Equation (64), Equation (63), Equation (62), Equation (61),
Calculations may be repeated in the order of equations (60) and (59). The symbols in the above formula can simply be treated as blank boxes as variables that occur during the calculation process, but it should be noted that they are given the following names.

K, : Kalman gain matrix Pk : Estimated error covariance matrix In the seventh calculation means, the second calculation means 19 uses δ, which is the component of 2, obtained by calculating the above equations.
and the correction coefficient δ in 28.

Furthermore, by noting that the calculation in equation (60) can be rewritten as the following equation, another effect unique to this embodiment can be pointed out.

? *=A(L−+)δk−+ + B (8 k−+)θ■−1・・・・・・・・・(66) This means that 1, found by equation (66), is exactly the third Since the temperature distribution is calculated by the calculation means 24.30 and the sixth calculation means 2l, the seventh calculation means 22 calculates the temperature distribution corresponding to the signal 29 in addition to the correction value Δδ6 of δ corresponding to the signal 36. A correction value Δj, can also be calculated, and by this correction, an estimated temperature distribution value δ5 that is closer to the temperature distribution state of the calculation target that can be known from the actual measurement signal 16 can be obtained. The estimated value layer at time k is set as the new initial value, and the third
If the above-mentioned prediction calculation is performed using the calculation means 30 of
It goes without saying that the future value of thermal stress can be estimated with the highest accuracy.

FIG. 2 shows another embodiment of the present invention, in which the heat exchanger outlet header to which the present invention was applied in FIG. Except that the fluid temperature is converted from the fluid pressure signal 82 to the fluid temperature signal 67 by the saturation temperature calculation means 78,
The structure is almost the same as the embodiment shown in the figure.

In the figure, 5l is a water supply line, 52 is an evaporator, and 53
54 is a steam separator, 54 is a nozzle, 55 is a steam outlet, 56 is a drain outlet, 57 is a steam supply valve, 58 is a steam supply line, 59 is a fluid pressure detector, 60 is a metal temperature detector, 6
1 is a fuel supply line, 62 is a burner, 63 is a flame, 64
is a fuel flow control valve, 65 is a fuel flow control valve drive signal, 66 is a steam supply valve, 67 is a fluid temperature signal, 68 is a metal temperature signal,
69 is a second calculation means, 70 is a signal setting element, 7l is a sixth calculation means, 72 is a seventh calculation means, 73 is a third calculation means, 74 is a screen editing means, 75 is a display, 7
6 is a first calculation means, 77 is a second calculation means, 78 is a saturation temperature calculation means, 79 is a third calculation means, 80 is a fifth calculation means, 81 is an optimum operation amount calculation means, and 82 is a fluid 83 is a heat transfer amount current value signal, 84 is a metal temperature calculation value signal, 85 is an arithmetic value correction signal, 86 is a thermal stress current value signal, 87 is a display drive signal, 88 is a steam temperature prediction signal, 89 is a fluid 90 is a heat transfer amount prediction signal, 9l is a thermal stress prediction signal, 92 is a fluid pressure change rate command signal, and 93 is a state quantity correction signal.

〔Effect of the invention〕

Since the present invention has the above-mentioned configuration, ■) the determination of whether the future thermal stress value of the heat exchanger outlet header, which conventionally relied on the experience and intuition of the operator, will exceed the limit value can now be made quantitatively. It becomes possible.

2) It becomes possible to quantitatively determine whether the future thermal stress value of the steam/water separator, which conventionally relied on the experience and intuition of the operator, will exceed the limit value.

3) It becomes possible to quantitatively determine whether or not the current rate of change in steam temperature is appropriate from the perspective of limiting the thermal stress value of the heat exchanger outlet header, which conventionally relied on the experience and intuition of operators.

4) It becomes possible to quantitatively determine whether or not the current rate of change in steam pressure is appropriate from the perspective of limiting the thermal stress value of the steam/water separator, which conventionally relied on the experience and intuition of operators.

5) It is possible to automatically perform an operation that harmonizes the requirement to prevent damage caused by thermal stress to the heat exchanger outlet header, which conventionally relied on the experience and intuition of operators, and the requirement to quickly change the required steam temperature.

6) It is possible to automatically perform an operation that harmonizes the requirement to prevent damage to the steam/water separator due to thermal stress, which conventionally relied on the experience and intuition of operators, and the requirement to quickly change the required steam pressure.

7) It is possible to estimate thermal stress values with high accuracy, which is an essential requirement for realizing the effects shown in items 1) to 6) above. In particular, the problem related to the value of the metal-fluid heat transfer coefficient, which was the biggest error factor in conventional thermal stress calculation, can be solved.

[Brief explanation of drawings]

1 and 2 are schematic diagrams for explaining each embodiment of the present invention, and FIGS. 3, 4, 5, and 6 are schematic diagrams for explaining the prior art. It is a diagram. ■・・・・・・Superheated steam, 4・・・・・・・・・
・Heat exchange inlet header, 5... Heat exchanger heat transfer tube, 6... Heat exchanger outlet header, 7.
・・・・・・・・・Steam temperature detector, 8・・・・・・・・・
・Metal temperature detector, 9...Superheated steam supply valve, 10...Excess steam discharge valve drive signal, 1l...Fuel supply Line, 12...
...Fuel flow control valve, l3...Fuel flow control valve drive signal, l6...Metal temperature signal, 17... ...Steam temperature signal, 18...
...Superheated steam supply valve drive signal, l9...
...Second calculation means, 2l...Sixth
calculation means, 22...7th calculation means,
24...Third calculation means, 25...
...Screen editing means, 26...Display, 27...Lth calculation means, 2
8... Second calculating means, 29...
...State quantity correction signal, 30...3rd
calculation means, 31...4th calculation means,
32...Optimum operation amount calculation means, 33...
...... Signal setting device, 34... Heat transfer amount current value signal, 35... Metal temperature current calculated value signal, 36... ...... Arithmetic value correction signal, 37... Steam temperature prediction signal, 38.
......Steam temperature increase target signal, 39...
...Heat transfer amount prediction signal, 40...Thermal stress prediction signal, 41...Steam temperature change rate limit value signal, 42... ...Thermal stress current value signal, 43...Display drive signal, 53
・・・・・・・・・Sea water separator, 59・・・・・・・・・
・Fluid pressure detector, 60...Metal temperature detector, 64...Fuel flow control valve, 65...
......Fuel flow control valve drive signal, 66...
...Steam supply valve, 67...Fluid temperature signal, 68...Metal temperature signal, 69...
......Second calculation means, 70...
・Signal setting element, 71...Sixth calculation means, 72...Seventh calculation means, 73...
......Third calculation means, 74...
・Screen editing means, 75...Disp L・
A, 76...First calculation means, 77...
......Second calculation means, 78...
・Saturation temperature calculation means, 79...Third calculation means, 80...Fifth calculation means, 81
......Optimum operation amount calculation means, 82...
...Fluid pressure signal, 83...Densen! Current value signal, 84...Metal temperature calculation value signal, 85......Calculated value correction signal, 8
6...Thermal stress current value signal, 87...
...Display drive signal, 88...
...Steam temperature prediction signal, 89...Fluid pressure increase target signal, 90...Heat transfer amount prediction signal, 91...Thermal stress Predicted signal, 92...
...Fluid pressure change rate command signal, 93...
...State quantity correction signal. Figure 3 Figure 4 Happy Heron Figure 5

Claims (7)

[Claims] (1) An operation support device for a device having a heat exchange section through steam, comprising: a first calculation means for predicting a future value of the steam temperature at the outlet of the section; and a container forming a steam flow path near the outlet of the section. a second calculation means for calculating the amount of heat transfer between the steam inside the container and the inner surface of the container based on at least the steam temperature; and a second calculation means for calculating the thermal stress generated in the container based on at least the amount of heat transfer related to the inner surface of the container. a third calculation means for determining the future value of the amount of heat transfer using the second calculation means using the future value of the steam temperature determined by the first calculation means; A driving support device characterized in that the device is configured to use the future value of the amount of heat transfer to obtain a predicted future value of thermal stress. (2) In an operation support device for an apparatus having a part that performs steam and water separation through a fluid that is water, steam, or a mixture thereof, a first calculation means for predicting a future value of the temperature of the fluid passing through the part. and a second calculating means for calculating the amount of heat transfer between the fluid in the container and the inner surface of the container based on at least the fluid temperature in the container constituting the flow path in or near the part itself, and at least the inner surface of the container. It has a third calculation means for calculating the thermal stress generated in the container based on the amount of heat transfer, and the second calculation means uses the future value of the fluid temperature obtained by the first calculation means to calculate the thermal stress generated in the container. A driving support device characterized in that it is configured to obtain a future value of heat amount, and further calculate a future predicted value of thermal stress using the future value of heat transfer amount in a third calculating means. (3) In claim (1), at least the third
1. An operation support device comprising display means for displaying a predicted value of future thermal stress obtained by the calculation means, a current rate of change in steam temperature, and a history of changes in steam temperature. (4) In claim (2), at least the third
1. An operation support device comprising display means for displaying a predicted future value of thermal stress obtained by the calculation means, and a current rate of change in steam pressure or a history of changes in steam pressure. (5) The steam temperature target value according to claim (1), comprising means for controlling the steam temperature at the outlet of the heat exchange section, and commanding the control means based on a future predicted value of thermal stress of the container; or the fourth to calculate the steam temperature change rate target value.
A driving support device characterized by being provided with a calculation means. (6) In claim (2), the steam-water separator includes means for controlling fluid pressure within the steam-water separator, and a steam pressure target value is commanded to the control means based on a future predicted value of thermal stress of the container. , or a fifth calculation means for calculating a steam pressure change rate target value. (7) In any one of claims (1) to (6), a measuring means for measuring the temperature at at least one point among the outer surface of the container or a point in the wall thickness of the container; inputting at least one set of the corresponding temperature measurement value and the temperature calculation value; It has a seventh calculation means for calculating the amount of correction of various numerical values in the second calculation means, and calculates the current value of the amount of heat transfer in the second calculation means from the current value of the fluid or steam temperature, and calculates the current value of the amount of heat transfer from the current value of the fluid or steam temperature. Based on the current temperature calculation value obtained by applying the calculation means 6 and the corresponding current temperature measurement value, the seventh calculation means calculates the second
What is claimed is: 1. A driving support device characterized by being configured to perform an operation for correcting the calculating means of and calculate a future value of thermal stress in such a state.