JP2851868B2 - Driving support device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an operation support device in a steam generation facility or the like, and particularly to an operation with frequent steam temperature and pressure changes while maintaining high reliability of the facility. The present invention relates to a suitable driving support device.

[Conventional technology]

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

The superheated steam 1 is led to a heat exchanger heat transfer tube 5 via a heat exchanger inlet header 4. The heat transfer tube 5 is heated by a flame 15 obtained by adjusting the fuel from a fuel supply line 11 by a fuel flow regulating valve 12 and applied to a burner 14.
Is passed through a heat exchanger outlet header 6 and then sent to a superheated steam supply line 23. 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 excess steam at that time is discharged by the excess steam discharge valve 2. Further, the temperature of the generated steam of such equipment is adjusted based on the value measured by the temperature detector 7 by adjusting the amount of fuel supplied to the burner 14 in accordance with the flow rate of the steam passing through the heat transfer tube 5.

In this steam generation equipment, when it is necessary to frequently change the steam temperature and the flow rate in the superheated steam supply line 23, care must be taken in terms of equipment reliability. In other words, not only when the steam temperature is intentionally changed, but also when the steam flow rate is changed, the heat exchange amount change in the heat transfer tube 5 cannot be adjusted depending on the steam flow rate. For example, the steam temperature fluctuates, and thermal stress is generated in the container constituting the equipment. The fatigue damage and creep damage caused by the thermal stress may eventually lead to cracking and blasting of the container.

In order to cope with such a fear, monitoring of the thermal stress at the heat exchanger outlet header 6 is performed in the prior art. This is because such a header is thick, and the thermal stress inherently caused by the metal temperature distribution is remarkably generated.
In the event of a crack, etc., it is difficult to replace the heat transfer tube 5 in particular, and at the exit of the heat exchange site, heat balance imbalance is accumulated and steam temperature fluctuates most. This is because it is suitable as a representative monitoring point of the thermal stress in the facility that generates the superheated steam from the viewpoint of easily increasing the size.

For example, Miyazaki,
Hoduka: Boiler Thermal Stress Monitoring System: Hitachi Critic Review Vol. 65, No. 6, P391
The method of calculating the thermal stress is summarized in the following concept.

In general, the temperature distribution of a cylindrical container such as a header is known to solve an axially symmetric one-dimensional heat conduction equation because the length of the cylindrical portion is sufficiently long with respect to the wall thickness. It is shown in the equation.

Here, the following symbols are given.

t: elapsed time [sec] ρ: metal density [kg / m ³ ] θ: metal temperature [° C] k: metal temperature conductivity [m ² / sec] r: distance in the radial direction of 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 differential equation (1), show three examples. , Which will be described later.

By solving the differential equation (1), the metal temperature distribution at time t can be obtained as a function θ (r, t) of r.
t) Since the volumes in the vicinity are different, it is necessary to take this into consideration. The average metal temperature to be reduced is called a volume average temperature and is given by the following equation.

Here, the subscripts a and b indicate the inner and outer surfaces of the cylindrical container, respectively. Accordingly, θ _a = θ (r _a , t) and θ _b = θ (r _b , t).

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

σ _tr = 0 ... (8) The following symbols are given here.

μ: Metal linear expansion coefficient [1 / ° C] η: Metal Young's modulus [kg / mm ² ] ν: Metal Poisson's ratio σ _t : Thermal stress inside [kg / mm ² ] Also, the subscripts r, s, and z are radii in order , Circumferential and axial components.

Furthermore, in a pressure vessel, internal pressure stress must be taken into account, and these are expressed by the following formula.

Here, the following symbols are given.

σ _p : Inner surface pressure stress [kg / mm ² ] P _f : Vessel fluid pressure [kg / cm ² ] For heat exchanger headers, steam separators, etc., heat transfer tubes and connecting tubes are connected to the side of the cylindrical container. And its tip can be regarded as a nozzle. As is well known, when there is a hole on the nozzle that is applied to the inner surface of the cylindrical container, the stress value is particularly high at the corner of the hole, but the value is the stress value of the inner surface of the container without the nozzle-shaped hole. Is multiplied by the stress concentration constant, and the stress at the corner of the nozzle-shaped hole is determined as follows.

σ _r = K _pr σ _pr …… (12) σ _s = K _ts σ _ts + K _ps σ _ps …… (13) σ _z = K _tz σ _tz + K _pz σ _pz …… (14) The following symbols are given.

σ: Nozzle corner total stress [kg / mm ² ] Kt: Thermal stress concentration coefficient Kp: Internal pressure stress concentration coefficient Since the nozzle corner calculated as above is the place where the stress value is the severest in such a container, What is necessary is just to evaluate the damage related to the generated stress for the location.
As is well known, work damage is governed by the maximum absolute value of the three components of the principal stress difference, and creep damage is governed by the equivalent stress value. These quantities are determined by the following equations.

σ _sz = σ _s- σ _z (15) σ _zr = σ _z- σ _r ... (16) σ _rs = σ _r- σ _s (17) Here, the following symbols are defined.

δsz: Principal stress difference (uniaxial component) [kg / mm ² ] δzr: Principal stress difference (axial-radial component) [kg / mm ² ] δrs: Principal stress difference (radius-circular component) [kg / mm ² ] δeg: Equivalent stress [kg / mm ² ] In applying the above-described equations, as described above, there are various examples related to how to give the boundary condition of equation (1), each of which has a feature, The structure shown in FIG. 3 is a typical structure hereinafter referred to as type I. After the type I is described in detail, FIG. 4 referred to as type II hereinafter and FIG. 5 referred to as type III hereinafter will be described.

In Type I, the following concept is followed. 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, the amount of heat transfer per unit area of the outer surface can be expressed by using the temperature gradient of the metal, so that the following equation is obtained.

Similarly, since the heat transfer amount on the inner surface is equal to the heat transfer amount between the inner surface and the internal fluid, the following expression is obtained for the unit area.

Here, the following symbols are defined.

α: Heat transfer coefficient between metal and fluid [kcal / m ² · sec · ° C] θf: Average fluid temperature [° C] In type I, while giving θf every moment,
Solve equation (1) by combining equations (19) and (20). Specifically, the fluid temperature signal 17 obtained by the temperature detecting means 7 is defined as θf, and the right side of the equation (20) is calculated by the second calculating means 107.
Along with the boundary condition in Eq. (19) that already assumed the value on the right side,
(1) is given to the third calculating means 109 for solving the equation.

The value of the heat transfer coefficient α in the equation (20) handled by the second calculating means 107 is an important parameter that governs the accuracy of calculating the thermal stress value, and is obtained as follows in the related art.

Here, the following symbols are defined.

λf: Thermal conductivity of internal fluid [Kcal / m · sec. ° C] Din: Representative dimensions (channel inner diameter) [m] Nuf: Internal fluid Nusselt number Ref: Internal fluid Reynolds number Prf: Prandtl number uf: Internal fluid flow rate [ m / sec] ζf: Kinematic viscosity of internal fluid [m ² / sec] Gf: Total mass flow rate of internal fluid [Kg / s] n: Number of circuits π: Pi Pf: Internal fluid density [kg / m ³ ] ( 21) The formula is called McAdams formula, and for details, refer to an appropriate reference (eg: Giedt; Yokobori, Kuga translation: Basic heat transfer engineering: Maruzen). In the formulas, n and Din are obtained from the structure of the header 6, and Gf is obtained from the operating state of the steam generating equipment.
λt, Prf, ζf, Pf can be found by using, for example, a steam table published by the Japan Society of Mechanical Engineers if the temperature, pressure, and dryness of the internal fluid are known. Based on these quantities, the values of all the variables according to equations (21) to (23) can be calculated.

According to the above concept, in the type I embodiment, the thermal stress present value signal 110 is calculated, and the fluid temperature signal 17 from the temperature measuring means 7 is constituted by the screen editing means 111 into a screen which is easy for the operator to grasp. It is displayed on 26. The operator monitors the display 26 and operates the signal setting units 101, 102, and 103 so that the thermal stress value does not exceed a specified value.

In the figure, 3 is an excess steam discharge line, 104 is a superheated steam supply drive signal, 105 is a fuel flow regulating valve drive signal, 106 is a surplus steam discharge drive signal, 108 is a heat transfer amount current value signal, and 112 is a display drive signal. It is.

FIG. 4 shows a type II embodiment. Most of the configuration of the apparatus and the concept of the operation are the same as those of the type I, so only the differences between them will be described. In FIGS. 3 and 4, components performing the same function are denoted by the same part numbers.

The biggest feature of Type II with the metal temperature detector 8 is that to obtain a signal 16 to provide an outer surface temperature theta _b. In type II, the measured θ is directly measured without assuming the conditions for heat insulation on the outer surface of the header relating to the heat insulating material 20 in equation (19).
_b is based on the method of solving the temperature distribution with the boundary condition of the equation (1). In particular, if the heat insulating material 20 has an insufficient thickness,
In the case where a considerable amount of heat is radiated to the atmosphere from the outer surface of the head 6, an effective improvement in accuracy can be expected as compared with the type I.

However, in a normal steam generator, a sufficient thickness of heat is usually performed from the viewpoints of both heat loss prevention and safety at the time of contact. ) Is still the most important factor that governs the thermal stress calculation accuracy.

FIG. 5 shows a type III embodiment. Most of the configuration of the apparatus and the concept of the operation are the same as those of the type I and the type II, so only the differences will be described. Components that perform the same function are the same as those in FIG. 3 and FIG.

The biggest feature of the Type III with a metal temperature detector 118, and to obtain a metal temperature signal 119 in the vicinity of inner surface can be regarded as the inner surface temperature theta _a, the value of this theta _a directly as a boundary condition (1 Equation (20) can be eliminated by solving equation (20).

Certainly, since the calculation of α basically depends on the empirical formula (21), the type III calculation method that does not use α that is inherently susceptible to errors has advantages. However, in addition to the difficulty in developing the thermal stress future value prediction calculation described later, the temperature gradient is generally sharp near the inner surface of the thick portion of the header 6, so that even when measuring near the inner surface, There is a problem that an error easily occurs with respect to the true value of the phase surface temperature.

In the above, the instrumentation technology according to the prior art has been described using the heat exchanger outlet header as an example.However, in the steam generator, the steam-water separator or the steam drum is similarly thick, and in the event of a crack occurring, It is a part that is difficult to replace and requires maximum attention to fatigue damage and creep damage due to thermal stress. In such a portion, since the fluid inside is a gas-water mixture, the fluid temperature and the saturation pressure uniquely correspond to each other. Therefore, it is customary to control the pressure by a pressure value or a pressure change rate. This is because pressure is generally easier to measure and control than temperature.

FIG. 6 shows an example of a steam / water separation part of a steam generating facility and an example of an instrumentation system based on the prior art. The water supplied from the water supply line 51 receives heat from the flame 63 in the evaporating pipe 52 to generate steam, and becomes a steam-water mixture. Air-water mixture nozzle
The air is blown in tangentially from the inner surface of the steam-water separator 53 so as to form a swirling flow along the inner wall of the steam separator 53. At this time, the liquid phase having a large specific gravity is pressed against the inner surface of the steam separator by centrifugal force, falls while rotating, and is discharged from the drain outlet 56. Since the gas phase having a small specific gravity has a small effect of the centrifugal force, it is collected at the center of the steam separator and sent to the steam supply liner 58 via the steam supply valve 57. The steam pressure in the facility is adjusted by adjusting the fuel flow regulating valve 64 in accordance with the amount of steam withdrawn by the steam supply valve 57 to adjust the amount of evaporation in the steam pipe 52.

The instrumentation system according to the prior art obtains a steam saturation temperature signal 67 from a steam pressure signal 82 obtained by a steam pressure detector 59 by an arithmetic means 78 having a function form of the pressure and the saturation temperature in the steam. The subsequent configuration is the same as that of FIG. 3 which is a conventional instrumentation system relating to the heat exchange outlet header. The device receives a thermal stress current value signal 158,
The fluid pressure signal 82 from the pressure measuring means 59 is displayed on the screen editing means 15
According to 9, the screen is configured to be easily understood by the operator and displayed on the display 75. The operator monitors the display 75 and sets the signal setting unit 151 so that the thermal stress value does not exceed the specified value.
And 152 are operated.

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 amount current value signal, 157 is a third calculation means, and 160 is a display drive Signal.

The apparatus shown in FIG. 6 belongs to the above-mentioned type I in the thermal stress calculation method similarly to the apparatus shown in FIG. 3, but relates to the method for calculating the thermal stress of the steam separator 53 in FIG. It is of course possible to apply a type II method similar to the apparatus and a type III method similar to the apparatus of FIG. Steam-water separator 53 type
Examples for II and Type III configurations are based on FIG.
Considering the differences between FIG. 3, FIG. 4, and FIG. 5, the configuration, features, and the like can be easily analogized, and thus the description is omitted.

The common feature of the above-described conventional instrumentation systems is that all of them monitor only the current value of the thermal stress generated in the thick part to be managed and, based on the information, expect the skill of the equipment operator to be skilled. Operation.

That is, the thermal stress generation is essentially caused by the phenomenon that the change in the fluid temperature inside the container is transmitted with a delay in the thickness direction of the container metal, for example, during the operation of increasing the fuel input amount. Even if the increase of the fuel input is stopped by knowing the high thermal stress value, the thermal stress value generally keeps increasing for a while. Therefore, inevitably, taking into account the current thermal stress value, if there is no prospect of the thermal stress value related to the current operation of the equipment,
Although a problem arises in the operation of the device, skill is required to obtain such a prospect.

Further, as described above, the monitoring accuracy of the current thermal stress value in the conventional technique also depends on the reliability of calculating the heat transfer coefficient of the inner surface of the container. Operating the device, including the prospect of future values of thermal stress, including in itself, requires a great deal of skill.

The above findings were solved with the function of predicting the future value of thermal stress based on the operating condition of the equipment up to the present point, which is basically used for calculating the thermal stress value in the conventional technology. It has already been known that this can be realized by applying the calculation means as a prediction simulator which sequentially advances the future under appropriate boundary conditions.

However, such prediction of the thermal stress value has not yet been put to practical use due to the following problems.

1) In the type I and type II thermal stress calculation methods, the heat transfer coefficient α on the inner surface of the container governs the accuracy. ,
It is performed under the idealized assumption of an infinitely long pipe, etc., and in the prediction calculation in which the time must be advanced and α must be used repeatedly, errors due to α accumulate and a reasonable thermal stress evaluation Is often impossible.

2) The type III thermal stress calculation method does not use α which causes the above-mentioned error, but on the other hand, it requires the metal temperature of the inner and outer surfaces of the thick-walled container as the boundary condition, which is the current value of the thermal stress for which the measured value can be used Although it does not hinder the calculation of, it is difficult to apply to the prediction of future values.

That is, the thick container is a passive part, and the inner and outer surface metal temperatures are determined as a result of the influence of the temperature of the internal fluid supplied from other heat exchange parts and the amount of fluid withdrawn from the container. It is impossible to determine the future value of the metal temperature on the inner and outer surfaces of the thick portion with high accuracy without considering the physical mechanism of the calculation in the calculation.

However, considering such a physical mechanism, it is necessary to calculate the heat transfer between the fluid in the container and the inner surface of the container, and the calculation requires a considerable number of parameters. Is the type
The same drawbacks as I and II are inevitable.

An object of the present invention is to achieve the most effective operation from the viewpoint of easily realizing an operation in which frequent steam temperature and pressure changes are performed while maintaining high reliability of facilities other than those expected from the skill of operators in the prior art. To provide a driving support system centered on high-precision prediction of a future value of thermal stress, which is a practical means. Specifically, the present invention relates to the above-described heat transfer coefficient α, which is a path for practical use of the prediction function. It comes down to solving the error problem.

[Means for solving the problem]

In order to achieve the above object, the present invention is characterized by including 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 heat exchange amount between steam and the header using the future value of the steam temperature, and the future value of the heat exchange amount Means for predicting the thermal stress on the inner surface of the header by using 2) Regarding the steam-water separator, the future value of the fluid temperature, the future value of the heat exchange amount, the future value of the thermal stress of the inside surface of the steam-water separator in the same manner as in 1) 3) Means for displaying the relationship between the predicted value of the thermal stress at the heat exchanger outlet header and the current heating rate, 4) Displaying the relationship between the predicted value of the thermal stress of the steam separator and the current pressure rising rate 5) Means for determining a heating rate command value in accordance with the predicted value of the thermal stress at the heat exchanger outlet header; 6) Means for determining the pressure increasing rate value in accordance with the predicted thermal stress value of the steam separator 7) Heat exchange with the internal steam or fluid for each of the heat exchanger outlet header and steam-water separator. Means for calculating the current value of the temperature distribution in the thickness direction of the header or the separator by using the current value of the amount, means for measuring the metal temperature in the outer surface of the thick vessel or the thick wall of the header or the separator, such measurement Means for correcting the heat transfer coefficient α related to the calculation of the current heat exchange amount by comparing the heat transfer coefficient α with the current value of the temperature distribution, and calculating the future heat exchange amount in the items 1) to 6) based on the corrected heat transfer coefficient α. Means to apply to.

[Action]

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

The future prediction method of the steam temperature or the fluid temperature in the items 1) and 2) may be calculated according to the operating conditions given to the boiler by using a simulation analysis method using a physical model. Specifically, a method based on the research by the authors [Reference: Miyama et al., "Development and Application of Boiler Plant Simulator": Thermal Nuclear Power, Vol. 37, No. 11, P1189-P1199 (Showa 61
−11)] may be applied. The calculation method for calculating the future value of thermal stress from the future value of steam and fluid temperature is a method mode I [Expression (1)] in which the calculation of the current value of thermal stress is performed in the description of the prior art.
-Explanation related to equation (23)], starting from the current value of the thermal stress, based on the steam and fluid temperature predicted at appropriate calculation time intervals (usually about 0.1 to 10 seconds). The thermal stress value at the time can be calculated. In such calculations, steam,
Α (used in equation (20)) for obtaining the heat exchange amount from the fluid temperature is corrected according to the means of item 7) as described later,
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 rate of change of the internal fluid temperature, and such a phenomenon is theoretically supported by the inventors of the present invention. This is as described in detail in the specification of "Boiler control device" (JP-A-63-118503).

Generally, to maintain the reliability of the pressure vessel, the maximum value of the generated thermal stress must be limited.However, since the maximum value of the thermal stress generated in the future is governed by the current rate of temperature change due to the above-mentioned characteristics, heat exchange By predicting the future value of the thermal stress at the outlet of the vessel, it is possible to evaluate whether the current heating rate is appropriate or not so as not to exceed the control value.

Similarly, in the steam-water separator, since the internal fluid is in a saturation region and the saturation temperature and the pressure have a one-to-one relationship, the temperature is generally obtained as a function of obtaining a pressure that can be easily measured. Therefore, the maximum value of the future thermal stress of the steam separator will be governed by the current boost rate, and the validity of the current boost rate can be evaluated from the predicted value of the thermal stress.

Regarding the items 5) and 6), generally, when the steam conditions (temperature and pressure) of the steam generating equipment are changed, for example, a "boiler control device" according to the invention of the present inventors) is disclosed in JP-A-61-24905.
The steam condition may be adjusted by instructing an appropriate rate of temperature increase and rate of pressure increase by using the above (2). In this case, if a high thermal stress is expected at the temperature increase rate and the temperature increase pressure rate, For example, an operation of reducing the absolute values of the temperature rise rate and the boost rate command value can be realized by such adjustment so that the predicted value becomes equal to or less than the limit value. Here, the command values for the temperature increase rate and the pressure increase rate are 0 when the steam temperature and the pressure respectively match the target values, and are generally positive or negative.

Regarding the term 7), in short, in the above-mentioned calculating means for obtaining the future value of the thermal stress from the future value of the fluid temperature, the outer surface of the header or the steam-water separator or the current value of the fluid temperature is calculated prior to the calculation of the future value. Calculate the current value of the metal temperature in the thick wall. Since the metal temperature calculation is obtained when solving the equation (1) in the process of calculating the thermal stress value, the thermal stress calculation calculation unit can be used as it is.

By comparing the calculated value of the metal temperature with the corresponding example value,
In various operating states, if the calculated temperature value is a prior change (the phase is advanced) compared to the actually measured value, the above-described heat transfer coefficient α [Equation (20)] which governs the accuracy of the calculation is excessive. On the other hand, if it changes later than the actual measurement value, the value of α is too small. Therefore, if α is sequentially corrected while paying attention to such a tendency, sufficient accuracy can always be maintained. Therefore, 1) by the operation of item 7)
The functions of (6) to (6) can be realized with sufficient accuracy for practical use.

(Example of the invention)

FIG. 1 shows a driving support system according to one embodiment of the present invention, in which a heat exchanger outlet header is monitored.

This system is based on the conventional technology shown in Fig. 3 (mode I calculation method), Fig. 4 (mode II calculation method), and Fig. 5 (mode II).
I was developed to solve the problems that existed in each of the instrumentation systems shown above. In explaining the present system, FIG.
4 and 5 are denoted by 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 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 a drive signal for an excess steam discharge valve, 11 is a fuel supply line, 12 is a fuel flow control valve, and 13 is a fuel flow control valve drive signal. ,14
Is a burner, 15 is a flame, 16 is a metal temperature signal, 17 is a steam temperature signal, 18 is a drive signal of a superheated steam supply valve, 19 is 2 'arithmetic means, 20 is heat insulating material, 21 is 6th arithmetic means, 22 is the calculating means of FIG. 7, 23 is the superheated steam supply line, 24 is the 3 'calculating means, 25 is the screen editing means, 26 is the display, 27 is the first calculating means, 28 is the second calculating means , 29 is a state quantity correction signal, 30 is third computing means, 31 is fourth computing means, 32 is an optimal manipulated variable directing means, 33 is a signal setter, 34 is a heat transfer quantity present value signal, and 35 is a metal temperature. Current calculated value signal, 36 is an operation numerical correction signal, 37 is a steam temperature prediction signal, 38 is a steam temperature heating target signal, 39 is a heat transfer amount prediction signal, 40 is a thermal stress prediction signal, 41 is a steam temperature change rate limit value Signal, 42 is thermal stress present value signal, 43
Is a display drive signal.

The system shown in FIG. 1 receives a steam temperature present value signal 17 and valve opening degree signals 10, 13, and 18, which are plant operation amounts at the present time, and obtains a steam temperature future value prediction signal 37 by a first calculating means 27.
Enter The prediction signals 37 are output by the number obtained by dividing the future prediction application time width by the calculation step size in order to calculate the value to be predicted in the future at intervals of the calculation step size. For example, if prediction is performed 10 minutes ahead with a calculation step width of 30 seconds, 20 prediction signals are output.

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

The third calculating means 30 receives the heat transfer amount prediction signal 39 and obtains a corresponding thermal stress prediction signal 40 at each time point. Further, the fourth calculating means 31 receives the thermal stress prediction signal 40 and outputs a current temperature rise rate limit value signal 41 for preventing the thermal stress value from exceeding the limit value in the future.

The optimum manipulated variable calculating means 32 receives the target temperature rise signal 38 and the current steam temperature signal 17 and, within a limit value (absolute value) given by the temperature rise rate limit value signal 41, according to the difference between the two signals. An excess steam discharge valve drive signal 10, a fuel flow regulating valve drive signal 13, and an excess steam supply drive signal 18, which are plant operation amounts, are calculated.

On the other hand, as a configuration for ensuring the practical accuracy of the above-mentioned prediction calculation, the second 'calculation means 19 includes a steam temperature present value signal.
The sixth calculation means 21 calculates the metal temperature distribution in the thickness direction of the header at the outlet of the heat exchanger, and calculates the metal temperature distribution corresponding to the position where the measurement point 8 exists. The current temperature calculation value signal 35 is calculated. Seventh arithmetic means 22
Receives the corresponding measured metal temperature signal 16 and the calculated value signal 35, and calculates a calculated numerical value correction signal 36 for performing necessary corrections including the heat transfer coefficient α described above.

The thermal stress current value signal 42 is calculated from the heat transfer current value signal 34 by using the third 'arithmetic means 24, and the thermal stress future value prediction signal 40
The display is displayed on the display 26 via the screen editing means 25 together with the current steam temperature value signal 17.

The operation of the first calculation means 27 is a prediction simulation based on a physical model, and as described above, refer to the reference document (Thermal Nuclear Power Generation, Vol. 37, No. 11, P1189 to P1199).

The second 'and second calculating means 19 and 28 calculate the above-mentioned equations (21), (22) and (23), and calculate the heat transfer amount by the following equation based on the equation (20).

α ^* = α · δ (25) Here, the following symbols are defined.

q: Heat transfer amount per unit length in the axial direction of the inner surface [kcal / m · sec] α ^* : Heat transfer coefficient after correction [kcal / m ² · sec · ° C] δ: Heat transfer coefficient correction coefficient [−] The transmission rate correction coefficient δ is given by a seventh calculating means described later.

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

The third 'and third calculating means 24 and 30 solve the equations (1) and (2) in the same manner as the sixth calculating means 21 and also calculate the equations (7) to (18) related to the thermal stress calculation. Is calculated.

When the equation (1) is solved by a digital computer among the above various operations, the following method is efficient. (1)
When the equation is expanded to the central difference form, it can be approximated to the following equation.

Here, the following symbols are defined.

r _i = r _a + (Δr) i (i = 1,... n) (27) t _j = t ₀ + (Δt) j (j = 1,... m) (28) θ _ij = θ (r _i , t _j ) ……… (29) The above equations are derived by assuming that the heat exchanger outlet header and the steam separator are cylindrical and have a thick wall as a container, divide the container into n concentric circles, and assume that the metal temperature is constant in the section. It is known that if n = about 10, the accuracy is practically sufficient. Δr is the thickness of the section, and Δt is the above-mentioned calculation step size.

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

g _i θ _{i−1, j + 1} −f _i θ _{i, i + 1} + θ _{i + 1, j + 1} = −g _{i
θ i-1, j + h} i θ ij -θ i + 1j ......... (31) here, and define the following symbols.

F _i, g _i, because h _i are constants in (31), the value theta _i-1 of the time t = t _j On the right _{side, j,} theta _{i, j,} right if θ _{i + 1, j} is known Are constants, and as simultaneous equations, the values of t = t _{j + 1 on} the left side, θ _{i−1, j + 1} , θ _{i, j + 1} , θ
It is possible to obtain _{i + 1 and j + 1} .

Accordingly, the value at t = t _{j + 2} can be calculated in the same manner by successively substituting the value of t = t _{j + 1} into the right side, so that the future value of the temperature distribution and the temperature distribution By applying the equations (7) to (18) at each time, the future value of the thermal stress can be calculated successively. (31)
The solution by the equation is called the crank = Nicholson method, and stable calculation is possible even for a relatively large Δt. For details on the Crank-Nicholson method, reference can be made to appropriate references (eg, GD Smith; translated by Fujikawa: Solution of partial differential equations by computer: Science Inc. (Showa 46-1)).

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

In equation (31), n + 1 court formulas can be obtained in correspondence with the number of divisions, where the unknowns are θ _{−1j + 1} , θ _{oj + 1 to} θ
_{nj + 1} θn _{+ 1j + 1} , that is, n + 3. This is processed as follows.

 Expression (19) is expressed in the central difference form as follows.

Therefore, the following equation is obtained. This equation also holds at time j + 1.

θ _{n + 1, j} = θ _{n−1, j} (36) Similarly, if the expression (24) is expressed in the central difference form, the following expression is derived.

In the above equation, θ _a = θ _oj was used from the definition. Θ _fj is the measured signal 17 for the current θ _{fo and} the first for the future value.
Shows the predicted value (j-th value in the signal 37) at the time point j calculated by the calculating means. The following equation is obtained from the equation (37).

Since the expression (38) is similarly established at the time point j + 1, if the expressions (36) and (38) are used, θ
_{Since −1j + 1} and θ _{n + 1j + 1} can be eliminated, equation (31) can be solved as a simultaneous equation.

As the seventh calculating means 22, for example, a method of inputting a deviation between the signal 35 and the signal 16 to a general PI controller in a control device to obtain δ of the equation (25), a method of applying fuzzy control theory or knowledge engineering Various examples are conceivable. In this embodiment, an example in which the extended Kalman-Filter theory is applied will be introduced. The advantage of this method is that the method using the PI controller, fuzzy control, knowledge engineering, etc. described above generally does not guarantee that the value of δ will converge to a theoretically meaningful value, but uses the Kalman-Filter theory. It can be pointed out that δ is guaranteed to converge to an optimal value in the sense of minimum variance and unbiased estimation.

For details of the Kalman-Filter theory, refer to appropriate references [for example, Katayama: Applied Kalman Filter: Asakura Shoten (1983-
4)], the points for applying the theory to the present invention will be described below.

Equations (31), (36), and (38) can be expressed as follows using matrix expressions.

Here, various quantities are defined as follows.

In the above equations Is an observation vector, having as its component the value of the signal 16 from the temperature detector 8, and the dimension of the vector is equal to the number of detectors 8 provided at different positions of the depth of the thick container including the outer surface. . Especially when there is one detector 8, Is a scalar, but the following treatment is the same.

Has the value of the current calculated value signal 35 corresponding to. In the following development, the symbol ＾ is used to distinguish an estimated value obtained as a result of various operations from a corresponding measured value or the like.

Is a state vector at the next point k, and has a metal temperature at each of the above-described division points and the outer surface from the inner surface of the thick container as a component. When the metal temperature distribution is estimated by performing the correction described below, the above-mentioned symbols are used. It is expressed as The matrix C is Ingredients and Is given by equation (40). Ie (40) is the only component that is compared with the measured value signal 16
It can be considered that it is extracted using an expression.

The components f _i and g _i of A ^** shown in equation (42) are all positive, and A ^** is a so-called fri-diagonal matrix.
Since the inverse matrix (A ^** ) ^-1 exists and the inverse matrix can be easily obtained by using a sweeping-out method or the like, the equation (39) becomes the following equation. A = (A ^** ) ^-1 A ^* ... (51) B = (A ^** ) ^-1 B ^* ... (52) In the above formula, A and B are transition matrices and driving matrices, respectively, in the system theory. Called. Here, both A and B include α ^* in their components, and from formulas (21), (22), (23) and (25), α ^* is δ, λ
_f , D _in , P _rf , h _f , and P _f . (32), (3
From equations (3) and (34), the other components of A and B, f _i , g _i , and h _i are K,
It is a function of Δr, Δt. However, among these parameters, except for δ, including the process of the prediction calculation, the time k
In the above, δ is an unknown parameter for minimizing the metal temperature estimation error at each point in time, while δ can be deterministically determined by using the actually measured value or the first calculating means 27.
In the following discussion, parameters other than δ will not cause any problems as long as they are calculated properly, so for simplicity,
A and B are considered to be functions of only the unknown parameter δ. At this time, it is shown by the following equation.

And an extended state variable Z _k having δ _k as components are defined as follows. Where δ is a true value, but an estimated value Is assumed to change every moment while converging to the true value.

Vector function above In order to estimate Z _k by applying the extended Kalman filter theory to, the following equations may be calculated.

The above equations are the initial values of _k and _k , the calculation error,
If the degree of error accompanying the approximation of the physical phenomenon according to the model formula is given as R _k , Q _k at time k as a covariance matrix, at each time, the measurement signal 16 (64), (63), (62), (61),
What is necessary is to repeat the calculation in the order of the equations (60) and (59).
The symbols in the above formula can be treated as black boxes simply as variables that occur in the process of calculation, but it should be noted that the following names are especially given.

K _k : Kalman gain matrix P _k : estimated error covariance matrix In the seventh arithmetic means, the second arithmetic means 19 is calculated by using δ which is a component of _k obtained by calculating the above equations.
And the correction coefficient δ in 28.

Further, if attention is paid to the fact that the operation of the expression (60) can be rewritten into the following expression, another effect unique to the present embodiment can be pointed out.

This is obtained from equation (66). Are exactly the third computing means 24, 30 and the sixth computing means 21
Since the temperature distribution is determined by the following equation, the seventh calculating means 22 calculates the correction value of the temperature distribution corresponding to the signal 29 in addition to the correction value Δδ _{k of} δ corresponding to the signal 36. Can also be calculated.
Temperature distribution estimated value close to the temperature distribution status of the calculation target obtained from 16 Is obtained. The estimate at time k If the above-described prediction calculation is performed using the third calculation means 30 with the following as a new initial value, there is no argument that the future value of the 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 is applied in FIG. 1 is replaced with a steam-water separator, and the inside measured by the embodiment of FIG. Except that the fluid temperature is converted from the fluid pressure signal 82 to the fluid temperature signal 67 by using the saturation temperature calculating means 78, the configuration is almost the same as that of the embodiment of FIG.

In the figure, 51 is a water supply line, 52 is an evaporator, 53 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, and 59 is a fluid. Pressure detector, 60 is metal temperature detector, 61 is fuel supply line, 62 is burner, 63 is flame, 64 is fuel flow control valve, 65 is fuel flow control valve drive signal, 66 is steam supply valve, 67 is fluid Temperature signal,
68 is the metal temperature signal, 69 is the second 'arithmetic means, 70 is the signal setting element, 71 is the sixth arithmetic means, 72 is the seventh arithmetic means,
73 is a 3 'arithmetic means, 74 is a screen editing means, 75 is a display, 76 is a first arithmetic means, 77 is a second arithmetic means, 78
Is a saturation temperature calculating means, 79 is a third calculating means, 80 is a fifth calculating means, 81 is an optimum manipulated variable calculating means, 82 is a fluid pressure signal, 83 is a heat transfer amount current value signal, and 84 is a metal temperature calculated value. Signal, 85 is an operation numerical 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 pressure increase target signal, 90 is a heat transfer quantity prediction signal, 91 is a thermal stress prediction signal, 92 is a fluid pressure change rate command signal, and 93 is a state quantity correction signal. is there.

〔The invention's effect〕

Since the present invention is configured as described above, 1) it is determined whether or not the future value of the thermal stress at the heat exchanger outlet header, which has been determined based on the experience of the conventional operator, exceeds the limit value. Quantitatively possible.

2) It is possible to quantitatively determine whether or not the future value of the thermal stress of the steam separator exceeds the limit value based on the experience and intuition of the conventional operator.

3) It is possible to quantitatively determine whether or not the current steam temperature change rate is appropriate from the viewpoint of limiting the thermal stress value at the heat exchanger outlet header, which was conventionally based on the experience and intuition of the operator.

4) It is possible to quantitatively determine whether or not the current steam pressure change rate is appropriate from the viewpoint of limiting the thermal stress value of the steam separator, which was conventionally based on the experience and intuition of the operator.

5) It is possible to automatically carry out the operation in which the requirement for preventing the heat exchange outlet header from being damaged due to the thermal stress and the requirement for promptly changing the required steam temperature, which have been conventionally based on the experience and intuition of the operator, are harmonized.

6) An operation in which the requirement for preventing damage caused by thermal stress of the steam separator, which was based on the experience and intuition of the conventional operator, and the requirement for promptly changing the required steam pressure can be automatically implemented.

7) It is possible to highly accurately estimate the thermal stress value, which is an indispensable requirement for realizing the effects described in the above items 1) to 6). In particular, the problem relating to the value of the heat transfer coefficient between metal and fluid, which has conventionally been the largest error factor in calculating thermal stress, can be solved.

[Brief description of the drawings]

FIGS. 1 and 2 are schematic structural views for explaining each embodiment of the present invention, and FIGS. 3, 4, 5 and 6 are schematic structural views for explaining the prior art. is there. 1 ... steam to be heated, 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, 11… Fuel supply line, 12 …… Fuel flow control valve, 13 …… Fuel flow control valve drive signal, 16 …… Metal temperature signal, 17 …… Steam temperature signal, 18…
.., A superheated steam supply valve drive signal, 19.
21... Sixth arithmetic means, 22... Seventh arithmetic means, 24.
3 'arithmetic means, 35 ... screen editing means, 26 ... display, 27 ... first arithmetic means, 28 ... second arithmetic means, 29 ... state quantity correction signal, 30 ... third Arithmetic means of 31
... 4th calculation means, 32 ... Optimal operation amount calculation means, 33 ...
... Signal setting unit, 34 ... Heat transfer current value signal, 35 ... Metal temperature present value signal, 36 ... Computed numerical value correction signal, 37 ...
Steam temperature prediction signal, 38 ... Steam temperature heating target signal, 39 ...
... heat transfer amount prediction signal, 40 ... thermal stress prediction signal, 41 ... steam temperature change rate limit value signal, 42 ... thermal stress present value signal, 43 ...
… Display drive signal, 53… water-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 calculating means 70 signal setting element 71 sixth calculating means 72 seventh calculating means 73 ... 3rd computing means 74... Screen editing means 75... Display 76.
First arithmetic means, 77 second arithmetic means, 78 saturated temperature calculating means, 79 third arithmetic means, 80 fifth arithmetic means, 81 optimal operation amount calculating means, 82: Fluid pressure signal, 83: Heat transfer current value signal, 84: Metal temperature calculation value signal, 85: Computed numerical value correction signal, 86: 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 prediction signal, 92 ... fluid pressure change rate command signal, 93 ... state quantity correction signal.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F22B 35/00 F22B 35/18 F22B 37/38

Claims (6)

(57) [Claims] 1. An operation support device for a device having a heat exchange portion through which steam passes and a steam flow passage near an outlet of the heat exchange portion, wherein a first value of a future value of a steam temperature at an outlet of the heat exchange portion is predicted. A second calculating means for calculating a future predicted value of the heat transfer between the steam in the heat exchange part and the inner surface of the heat exchange part using the future predicted value of the steam temperature obtained by the first calculating means. Calculating means, using the future predicted value of the heat transfer amount, third calculating means for obtaining a predicted value of the thermal stress generated on the inner surface of the heat exchange portion, and a current value of the steam temperature at the outlet of the heat exchange portion On the basis of,
Second 'arithmetic means for calculating a current value of heat transfer between the steam in the heat exchange part and the inner surface of the heat exchange part; and the heat value based on the current value of heat transfer obtained by the second' arithmetic means. A third calculating means for calculating a thermal stress generated on an inner surface of the exchange part; a measuring means for measuring a metal temperature of at least one of an outer surface and a point in a thickness of the heat exchange part; 'Calculates the metal temperature at the measuring point of the measuring means based on the current value of the heat transfer amount obtained by the calculating means.
And a set of a metal temperature measurement value obtained by the measurement means corresponding to the measurement point and a calculation set obtained by the sixth calculation means are input, and at least a calculation operation by the second calculation means is performed. A driving support device comprising: a seventh calculating means for calculating a numerical correction amount. 2. An operation assisting apparatus for a device having a portion for performing steam-water separation through a fluid that is water or steam, or a mixture thereof, and a flow passage near an outlet of the portion, wherein the temperature of the fluid passing through the portion is controlled. A first calculating means for predicting a future value; and a future predicted value of the heat transfer amount between the fluid in the part and the inner surface of the part using the future predicted value of the fluid temperature obtained by the first calculating means. A second calculating means for obtaining; a third calculating means for obtaining a future predicted value of thermal stress generated on the inner surface of the part using the predicted value of the heat transfer amount; and a current value of the fluid temperature at the outlet of the part. Second 'calculating means for calculating the current value of the heat transfer between the fluid in the part and the inner surface of the part based on the current value of the heat transfer generated on the inner surface of the part based on the current value of the heat transfer obtained by the second' calculating means 3 'to calculate the thermal stress Calculating means, among the points of the outer surface or meat Atsunaka of the site, at least 1
Measuring means for measuring the metal temperature at the point; and sixth calculating the metal temperature at the measuring point of the measuring means based on the current value of the heat transfer amount obtained by the second 'calculating means.
And a set of a metal temperature measurement value obtained by the measurement means corresponding to the measurement point and a calculation value obtained by the sixth calculation means, and at least calculation by the second calculation means is performed. A seventh calculating means for calculating the correction amount of the numerical value,
A driving assistance device comprising: 3. The driving support device according to claim 1, wherein the predicted value and the current value of the thermal stress generated on the inner surface of the heat exchange portion obtained by the third and third arithmetic means and the heat exchange. A driving support device comprising a display unit for displaying a current steam temperature at an exit of a part. 4. The driving support apparatus according to claim 2, wherein a predicted future value and a present value of thermal stress generated on the inner surface of the part determined by the third and third 'arithmetic means and an outlet of the part. A driving support device comprising a display means for displaying a current steam pressure. 5. The driving support device according to claim 1, further comprising control means for controlling an outlet steam temperature of the heat exchange part, and instructing the control means based on a future predicted value of a thermal stress of the heat exchange part. A driving support device comprising: a fourth calculating means for calculating a steam temperature target value or a steam temperature change rate target value. 6. The driving support device according to claim 2, further comprising a control unit for controlling a fluid pressure in a portion where the water / water separation is performed, wherein the control unit controls the fluid pressure based on a future predicted value of thermal stress in the portion. A driving support device comprising: a fifth calculating means for calculating a commanded steam pressure target value or a steam pressure change rate target value.