JPH0743086B2 - Boiler stress monitoring controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress monitoring control device for a boiler, and more particularly, to stress monitoring of a boiler plant for intermediate load operation in which frequent start / stop and load change operation are required. The present invention relates to a boiler stress monitoring control device suitable for control.

[Background of the Invention]

At the time of operation of the boiler plant, especially when starting and stopping and when the load changes, due to the difference between the temperature of the internal fluid and the metal temperature, especially at the nozzle corners of the thick wall pressure-resistant portion such as the header pipe side of the outlet of the secondary superheater Thermal stress is generated, which is the main cause of consumption of fatigue life.

Further, during the rated operation, the creep life consumption due to the main stress that is the sum of the thermal stress and the internal pressure stress due to the pressure of the internal fluid becomes remarkable.

Therefore, in order to ensure the safe operation of the boiler plant, it is necessary to suppress the above-mentioned thermal stress or principal stress that causes lifespan consumption so that excessive lifespan consumption does not occur.

Conventionally, as a method of monitoring control of thermal stress or main stress,
Estimate the current value of thermal stress or principal stress based on measured values such as metal temperature and internal fluid temperature, pressure, flow rate, etc.If the alarm value is exceeded, the operator manually
Empirically, the rate of temperature rise is reduced at startup, and during load operation,
The load change rate and load change width are reduced to suppress the thermal stress. However, in such a method, the operation amount of fuel or water is adjusted after detecting that the thermal stress exceeds the limit value. For,
Operation delays. That is, there is a problem that a time delay of the order of minutes occurs until the difference between the average temperature of the metal and the inner surface temperature decreases and the thermal stress decreases, and as a result, the thermal stress may exceed the limit value. .

On the other hand, the thermal stress limit value, which is set at the time of starting the plant operation, is used as a constant at the time of designing the boiler plant, assuming the pattern of start-stop operation and the number of times of each pattern with respect to the service life of the plant.

However, in reality, the operating pattern of the plant and the number of times of each pattern are different from the planned value, so that the cumulative life consumption, in other words, the remaining life, deviates from the planned value. As a result, the conditions for thermal stress limitation should be too tight or too lenient under the initially planned useful life.

This means that in the former case, the start-up or load responsiveness of the plant is unnecessarily limited, and in the latter case, the operation is shorter than expected. ing.

As a thermal stress evaluation point, set different points,
While it is necessary to monitor all of these, it is most desirable to bring the temperature rise rate and load close to the target value while keeping them below the stress limit value in any of these cases. Controlling the operation of the boiler plant was not considered at all.

[Object of the Invention]

The object of the present invention is to eliminate the above-mentioned conventional drawbacks, and to suppress the thermal stress at the evaluation point of the boiler plant within the limit range commensurate with the remaining life, while enabling safe and quick boiler start / stop and load operation. The present invention is to provide a boiler thermal stress monitor and control device.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention monitors and controls the stress at an evaluation point set at a desired point in the piping of a boiler plant.

The structural features are that means for calculating the current value of the internal fluid flow rate at the evaluation point, means for calculating the metal temperature distribution at the evaluation point based on the internal fluid flow rate calculation value, and the metal temperature distribution calculation A stress calculation unit composed of means for calculating thermal stress based on the value, means for calculating internal pressure stress from the pressure of the internal fluid, and means for calculating main stress from the thermal stress and internal pressure stress; Means for calculating the remaining life of the evaluation point from the principal stress obtained by the calculation unit, means for updating the stress limit value from the remaining life calculation value, and stress prediction for predicting the principal stress of the evaluation point at a future time point Means, main steam temperature predicting means for predicting the main steam temperature at the same time point, load predicting means for predicting the load at the same time point, deviation of stress prediction value from steam stress limit value, main steam temperature prediction value The main steam of At least one of the deviation with respect to the load set value and the deviation with respect to the load command of the predicted load value is held within the allowable value, and the evaluation value of the remaining deviation (for example, the sum of the squares of the deviations) is minimized. And a means for setting a main steam temperature set value and a load command value.

Example of Invention

Before showing an embodiment of the present invention, an outline of a main part of an oil-fired constant pressure once-through boiler plant, which is one of the objects to which the present invention is applied, will be described below with reference to Figs. 2 and 4.

In FIG. 4, the flow rate of the fuel is controlled by the fuel flow rate control valve 100 and is supplied to the burner 101. The flow rate of the combustion air is controlled by the damper 103 by the forced draft fan 102 and is controlled by the burner 10.
Sent to 1. On the other hand, the water supply is pressurized by the water supply pump 104, the flow rate is controlled by the water supply flow rate control valve 105, and the water is supplied to the boiler 200.

As can be seen from FIG. 2, the operation of the boiler plant has two modes, that is, start-up bypass operation from the ignition of the burner 101 to full opening of the superheater stop valve 6 and subsequent flow-through operation from load operation to stop operation. It is divided into

First, the startup bypass operation will be described. As shown in FIG. 4, the water supply supplied from the water supply pump 104 via the control valve 105 is preheated by the economizer 201 of the boiler 200,
It is heated by the water wall 202.

And the heating fluid passes through the primary superheater bypass valve 1,
And from the primary superheater 203 through the secondary superheater bypass valve 2 to the flash tank 206, respectively, while:
The steam is further passed through the superheater ventilation valve 5 to the secondary superheater 204.
Be vented to.

The steam superheated in the secondary superheater 204 is guided to the flash tank 206 and the condenser 400 through the turbine bypass valve 7, and warms the main steam pipe.

Next, when the pressure in the flash tank 206 has risen to a predetermined value, the main blocking valve bypass valve 9 is opened and the turbine 310,
Ventilate the 330 and accelerate the turbine. Turbine 310,330
When the number of rotations reaches the rated speed (3600 rpm in this example), it is synchronously inserted and the initial load is taken by the flash tank steam.

Then, so that the enthalpy of the outlet fluid of the primary superheater 203 is equal to the enthalpy of the flash tank vapor,
By controlling the opening degree of the secondary superheater bypass valve 2, the primary superheater outlet temperature is controlled to a specified value.

When the specified load is reached after the turbine initial load is combined, the control of the main blocking valve bypass valve 9 is switched to the control valve control by opening the main blocking valve 8.

After that, when the target load exceeds the specified value, the superheater pressure reducing valve 3 is opened, and when the pressure at the inlet of the secondary superheater 204 becomes higher than the flash tank operating pressure, the check valve on the superheater ventilation system is checked. The steam source is switched to the primary superheater 203 by means of a valve (installed downstream of the superheater ventilation valve 5).

In parallel with this, the secondary superheater bypass valve 2 is automatically closed, while the superheater ventilation valve 5 is closed when the inlet pressure of the superheater stop valve 6 becomes equal to or higher than a specified value.

In the next step, the superheater pressure reducing valve 3 is opened by the load request signal, and the load is increased from the combined load to about 20% load.
The superheater stop valve 6 turns the superheater pressure reducing valve 3 when the load reaches 20%.
Is gradually opened until fully opened, and after the valve 3 is fully opened, it is continuously opened. On the other hand, the primary superheater bypass valve 1 is closed corresponding to the above operation, and is fully closed when the load is about 25%.

As described above, until the superheater stop valve 6 is fully opened,
As shown in FIG. 2, this is called startup bypass operation.

In the once-through operation (normal operation), as can be seen from FIG. 2, in the operation phase after the superheater stop valve 6 is fully opened, the load is adjusted by the turbine control valve 10 until the plant is stopped.
The turbines 310 and 330 rotate due to adiabatic expansion of superheated steam, and the generator 500 generates electric power.

The secondary superheater outlet header pipe side portion 205 shown in FIG. 4, especially the inner nozzle corner NC, is made of thick metal and has a complicated structure. Therefore, all the operations of starting, loading and stopping the plant are performed. This is a part where significant stress is exerted over the region, and is a typical part of stress evaluation points under severe conditions in terms of life consumption.

In addition to this, the reheater outlet header pipe side portion 208 is also thinner than the above, but the inside is exposed to higher temperature steam, and a remarkable creep stress acts on the inner surface nozzle corner portion, so the stress evaluation point As an important part.

In addition, in the transformer operation boiler plant, the inner surface nozzle corners of the brackish water separator and the brackish water separator tank are also important evaluation points.

In order to operate such a thermal power plant smoothly according to the load request command, it is necessary to appropriately control each control valve, damper and the like. FIG. 3 shows a schematic diagram of a conventional thermal power plant automatic control system.

The outline of the functional operation will be described below with reference to FIG.

First, the load (output of the generator 500) request signal 600 to the thermal power plant is limited within the load change rate preset by the setter 602 by the load change rate limiter 601, and the main steam pressure correction bias addition is performed. Added to the vessel 603.

The output signal of the load change rate limiter 601 also becomes a demand signal to the governor control 604, and controls the turbine regulator valve 10 so that the MW 605 (generator output) becomes a specified value.

On the other hand, so that the main steam pressure 606 becomes equal to the set value 607,
A main steam pressure correction bias is created by the subtractor 608 and the main steam pressure control 609, and this is added to the signal by the adder 603 to create a boiler input command.

The boiler input command is converted by the water supply program 610 into a water supply flow rate command signal corresponding to the boiler input, and the water supply flow rate 611 is converted.
Is fed to the water supply control 612 as the set value of, and the water supply flow rate control valve 1
Used for control of 05.

The boiler input command is also converted into a fuel amount command signal commensurate with the load in the fuel program 613.

The main steam temperature correction bias signal created by the main steam temperature control 616 and the fuel amount command signal are added as a control signal corresponding to the deviation between the main steam temperature 614 and the set value 615 (obtained by the subtractor 615A). It is added by the device 617 and is given to the fuel control 619 as a set value (fuel amount command) of the fuel flow rate 618. Then, the fuel flow rate control valve 100 is controlled by the control output.

The fuel amount command also includes a deviation of the exhaust gas excess O ₂ 620 from the set value 621 (a control signal corresponding to the value obtained by the subtractor 622, an O ₂ correction bias signal generated by the O ₂ correction control 623, and an adder). It is added by 624 and becomes an air flow rate command signal.

In the air amount control 625, the forced draft fan damper 103 is controlled so that the air flow rate 626 becomes equal to the air flow rate command signal.

The above is the outline of the thermal power plant automatic control system.

FIG. 1 is a block diagram showing the overall configuration of an embodiment in which the present invention is applied to the boiler plant control system shown in FIG. In the figure, the same or equivalent elements as in FIG. 3 are represented by the same symbols. In this embodiment, the case where the stress evaluation point is the nozzle corner NC of the inner surface of the secondary superheater outlet header pipe will be described.

The difference from the conventional one in FIG. 1 is that the following functional blocks are added.

(1) Stress calculation function block 1000 (2) Remaining life calculation function block 1100 (3) Stress limit value calculation function block 1200 (4) Main steam temperature prediction function block 2000 (5) Stress prediction function block 2100 (6) Load prediction Function block 3000 (7) Control evaluation function block 4000 (8) Optimal operation amount search function block 5000 (9) Optimal operation amount output function block 6000 (10) Priority control selection function block 7000 Stress calculation function block 1000 is the stress evaluation point. This is a part to calculate the present value of the principal stress in consideration of both the thermal stress and the internal pressure stress.

The remaining life calculation function block 1100 is a part for calculating the cumulative life consumption rate based on the main stress present value calculated above and calculating the remaining life.

The stress limit value calculation function block 1200 is a part that recalculates the stress limit value based on the remaining life calculation value.

The main steam temperature prediction function block 2000 is a part that predicts the main steam temperature after a specified time.

The stress prediction function block 2100 is a part that predicts and calculates the stress after the specified time based on the steam main steam temperature prediction value.

The load prediction function block 3000 is a part that predicts the load level after a specified time.

The control evaluation function block 4000 determines that the stress prediction value is less than or equal to the stress limit value, and the deviation between the predicted main steam temperature value and the set value (deviation 1) and the deviation between the predicted load value and the load request signal correspond to the operation phase. This is a portion for judging and evaluating whether or not both or one of (deviation 2) is the minimum value.

If the determination result is not good, the optimum manipulated variable search function block 5000 searches for the optimum manipulated variables (main steam temperature change rate and load change rate) in the direction of reducing the corresponding deviation, and based on this, Then, the main steam temperature prediction function block 2000, the stress prediction function block 2100, and the load prediction function block 3000 recalculate each predicted value, and the control evaluation function block 4000 repeats the above search until the determination condition is satisfied.

When the determination condition is satisfied, the operation amount at that time is output as an optimum value via the optimum operation amount output function block 6000.

Hereinafter, each functional block will be described in detail.

FIG. 5 shows a detailed functional block diagram of the stress calculation functional block 1000. In this configuration example, the metal temperature distribution calculation at the stress evaluation point is switched between the steady temperature distribution calculation model and the unsteady temperature distribution calculation model according to the flow rate and pressure of the internal fluid as shown in FIG. , With high precision.

In this case, the flow rate calculation of the internal fluid is divided into before the synchronous merge (inflow calculation 1) and after the merge (flow rate calculation 2), for example, Japanese Patent Application No. 60-53856 (Japanese Patent Laid-Open No. 61-213403). ).

Hereinafter, a specific example of the stress calculation function block 1000 will be described in detail with reference to FIGS. 2, 4, and 5.

As described above, in FIG. 4, in the outlet header pipe side 205 (hereinafter, abbreviated as an evaluation point) of the secondary superheater 204, stress is generated in the inner surface nozzle corner NC even after the plant is stopped. From start to stop, of course,
Furthermore, it is necessary to continuously monitor the stress even after the stop.

In that case, the metal temperature distribution at the evaluation point 205 is the main steam pipe 20.
And when the internal fluid is flowing in the water pipe 22, it follows the unsteady temperature distribution characteristics, but when the internal fluid is not flowing,
Follow the steady temperature distribution characteristics.

Therefore, in order to accurately calculate the metal temperature distribution, it is necessary to appropriately switch the calculation model according to the state of the internal fluid.

However, the flow rate of the fluid inside the evaluation point 205 cannot be directly measured. Therefore, in the present invention,
Until the turbine synchronous insertion, it is calculated from the opening of the turbine bypass valve 7 and the differential pressure between the outlet fluid pressure of the secondary superheater 204 and the internal pressure of the flash tank 206.
It is supposed to be calculated from the turbine load.

As described above, the internal fluid does not flow to the outlet pipe of the secondary superheater, that is, at the evaluation point 205 after the boiler is ignited until the superheater ventilation valve 5 and the turbine bypass valve 7 are opened. Therefore, the metal temperature distribution at the evaluation point 205 is calculated according to the steady-state metal temperature distribution calculation model.

On the other hand, after opening both valves 5 and 7, the superheater stop valve 6
Since the internal fluid flows to the evaluation point 205 until is closed, the metal temperature distribution is calculated according to the unsteady metal temperature distribution calculation model.

In the unsteady metal temperature distribution calculation, the heat transfer amount from the internal fluid to the metal is calculated, and therefore the flow rate of the internal fluid needs to be calculated.

As shown in FIG. 2, the opening of the turbine bypass valve 7, the opening / closing of the upper seat drain valve 12 in front of the main blocking valve, the opening of the main steam pipe drain valve 11, and the initial load are increased until the synchronous insertion. The flow rate of the internal fluid is calculated using the turbine speed R in the speed increasing process of the low-pressure and medium / high-pressure turbines 310, 330 up to that time as an input signal (flow rate calculation 1 in FIG. 2).

On the other hand, after the parallel insertion, the flow rate is calculated using the turbine load MW (or the output of the generator 500) as an input signal (flow rate calculation 2 in FIG. 2).

Next, the operation of each part in FIG. 5 will be described.

First, when the operation of the apparatus is started, the metal temperature distribution initial value calculation unit 1001 uses the internal fluid temperature measurement value T _f at the evaluation point 205 and the outer surface metal temperature measurement value T _MO to calculate a steady metal temperature distribution calculation model ( The initial value of the metal temperature distribution at the evaluation point 205 is calculated based on (described later in detail).

Next, when the burner is ignited and the plant is started, the burner ignition signal is detected, the model switching condition determination unit 1002 is operated, and the pressure measurement value P _f of the internal fluid at the evaluation point and the flow rate calculation value G are continuously calculated. Let me watch.

Then, whether the superheater ventilation valve 5 and the turbine bypass valve 7 are opened and whether the internal fluid is flowing to the evaluation point 205 is whether both the pressure measurement value P _f of the internal fluid and the flow rate calculation value G are equal to or more than the specified values. I will judge it.

That is, when at least one of the flow rate calculated value G and the measured value P _f is less than the specified value, it is determined that the internal fluid is not flowing, and the steady metal temperature distribution calculation model 1003 is operated. Then, the changeover switch (A) 1004 is switched to the side a, that is, the steady metal temperature distribution calculation model side, and the calculation result is stored in the metal temperature distribution storage unit 1006.

When both measured values of both steams exceed the specified values, the unsteady metal temperature distribution calculation model 1005 is operated. Then, the changeover switch (A) 1004 is switched to the side b, that is, the unsteady metal temperature distribution calculation model 1005 side, and the calculation result is stored in the metal temperature distribution storage unit 1006.

In the steady-state metal temperature distribution calculation, first of all, the internal fluid flow rate calculation unit 1007 calculates the internal fluid flow rate based on various process amounts D _a by different calculation methods before and after synchronous inclusion as described above. Value G and calculated values of internal fluid temperature and pressure T _f
And P _f , the heat transfer coefficient calculation unit 1008 calculates the heat transfer coefficient from the internal fluid to the metal.

Next, the metal temperature distribution storage unit 1006 obtained by switching the changeover switch (B) 1009 to the b side based on the boundary condition of the inner surface metal obtained by substituting the above heat transfer coefficient into the equation (4) described later. The content (calculation result by the steady metal temperature distribution calculation model 1003) is used as the initial temperature distribution, and the unsteady metal temperature distribution calculation model 1005 is used to calculate the metal temperature distribution.

Further, the above calculation result is corrected by the outer surface metal temperature measurement value T _MO , and the correction result is stored in the metal temperature distribution storage 1006 via the b side input of the switch (A) 1004.

When the plant is stopped, the superheater stop valve 6 in FIG. 4 is closed and the internal fluid at the evaluation point 205 decreases.

At least one of the flow rate and the pressure of the internal fluid, when it is detected by the model switching condition determination unit 1002 that is less than a specified value, contrary to the above, a metal temperature distribution calculation model,
The unsteady metal temperature distribution calculation model 1005 is switched to the stationary metal temperature distribution calculation model 1003.

As the initial value of the metal temperature distribution at this time, the contents of the metal temperature distribution storage unit 1006 are used by switching the changeover switch (B) 1009 to the a side. Furthermore, changeover switch (A) 1004
Also, switch to the a side to calculate the steady-state metal temperature distribution calculation model 1003
The calculation result of is stored in the metal temperature distribution storage unit 1006.

The thermal stress is calculated as described above, and based on the content of the stored metal temperature distribution storage unit 1006, the thermal stress calculation unit
Calculate with 1010. On the other hand, the internal pressure stress is calculated by the internal pressure stress calculation unit 1011 based on the calculated pressure value P _f of the internal fluid.

The principal stress calculation unit 1012 calculates the principal stress from the calculated values of the thermal stress and the internal pressure stress obtained as described above.

Next, specific examples of the metal temperature distribution calculation and the stress calculation will be described in more detail.

First, the metal temperature distribution initial value calculation unit 1001 and the steady metal temperature calculation model 1003 that use the same calculation formula will be described.

The secondary superheater outlet header pipe side, that is, the evaluation point 205,
Considered as an infinite cylinder with dimensions of each part as shown in Fig. 1,
There is no axial temperature distribution-in other words, its radius b.
It is assumed that the temperature distribution in the direction of is the same at any position in the axial direction.

Then, as shown in FIG. 22, the metal temperature T _i (i is O to N) at the i-th division point among the N points in the radial direction at the evaluation point 205 is calculated as the steady temperature distribution of the following equation (1). Calculate using the formula.

T _i = Alnr _i + B ……… (1) Where r _i : distance from the center of the cylinder a: inner radius of the cylinder b: outer radius of the cylinder T _MO : measured value of the outer surface metal temperature T _f : measured value of the inner fluid temperature Next, the temperature distribution calculation in the transient metal temperature calculation model The formula will be described.

Similarly to the above, assuming that the evaluation point 205 is an infinite cylinder and assuming that the temperature distribution in the axial direction does not occur, the radial unsteady metal temperature distribution is expressed by the following equations (3) to (5). Calculated.

Where λ: thermal conductivity of metal h: heat transfer coefficient from internal fluid into metal T _O : calculated inner surface metal temperature Note that the above equation (4) is transferred from the internal fluid to the metal at the evaluation point 205. The amount of heat is equal to the product of the temperature gradient on the inner surface of the metal and the thermal conductivity of the metal, and the equation (5) shows that the outer surface of the metal is in thermal equilibrium. It is shown.

The equations (3) to (5) are calculated by a digital computer (not shown).
In order to calculate in the same manner as in the case of the steady temperature distribution calculation, the evaluation point metal is divided into N in the radial direction, and the division unit flow is Δ so that the metal temperature T _i (j) at each division point is obtained.
It is necessary to convert to the differential format shown in FIG. 23, where r is the calculation cycle of the temperature distribution and Δt is the calculation cycle.

In FIG. 23, 60 is a table for storing the data before conversion, and 61 is a conversion unit for converting to the differential format. Reference numeral 62 is a table for storing the converted data.

The data stored in 60 is converted by the conversion unit 61 as shown in the following expression (6). That is, here, Where T _f (j): temperature of internal fluid at time j T _i (j): temperature of metal dividing point i at time j a _j : thermal diffusivity (value at time j) λ _j : thermal conductivity ( Value at time j) h _j : Heat transfer coefficient (value at time j) Δr: Unit length of cylindrical division of metal Next, the heat transfer coefficient h _j is calculated by the annual transfer coefficient calculation unit 1008.
It is calculated based on the following equations (7) to (10). (Refer to Shoji Isshiki, Co., Ltd., Morikita Publishing Co., Ltd., "Heat Transfer Engineering", page 89).

w = G ・ v / S ………… （7） h _j = 0.023 ・ R _e ^0.8・ R _r ^0.4・ K / 2a (10) where, w: Steam flow velocity G: Internal fluid flow rate v: Internal fluid specific volume (function of temperature T _f and pressure P _f ) S: Channel cross-sectional area R _e : Reynolds number ν: Dynamic viscosity coefficient (function of temperature T _f and pressure P) K: Thermal conductivity (function of temperature T _f and pressure P) P _r : Prandtl number (temperature T ₁ and Function of Pressure P) The internal fluid flow rate G in the above equation (7) is calculated by the internal fluid flow rate calculation unit 1007 using the following equation (11) before being merged.

Where G _{1 is} the flow rate of the turbine bypass valve G _{2 is} the flow rate of the main block valve front upper seat drain valve 12 G _{8 is} the flow rate of the main steam pipe drain valve 11 G _1RH is the steam flow rate of the one-stage reheater 207 The above G ₁ , G ₂ , and G ₈ can be obtained by a general flow rate calculation formula based on the differential pressure characteristic of each valve.

That is, the flow rate G ₁ is obtained by using the differential pressure between the secondary superheater outlet steam pressure and the flash tank internal pressure, and the flow rates G ₂ and G
₈ uses the differential pressure between the secondary superheater outlet steam pressure and the condenser pressure, based on the valve characteristics such as the valve flow passage cross-sectional area,
Each can be calculated.

On the other hand, G _1RH can be calculated by multiplying the maximum flow rate before _inclusion by the ratio to the rated speed of the turbine.

The coefficient 1/4 in the above equation is a coefficient for proportionally converting the flow rate of each pipe header from the total amount of steam in a plant in which two main steam pipes 20 are installed.

Next, as the internal fluid flow rate G after the merger, the main steam flow rate for the turbine load is stored in advance as a table,
It can be calculated by interpolation calculation based on this data.

The results of the unsteady metal temperature distribution calculation formula obtained by the above procedure are as follows: a) the metal inner surface heat transfer coefficient agrees with the equation (10) using the outer surface metal temperature measurement value T _MO , and b) the outer surface. Corrected to match the metal temperature to the measured value. That is, according to the size of the difference between the calculated inner surface metal temperature value T _o and the calculated outer surface metal temperature value T _N , when (1) | T _o −T _N | ≧ 0.5 ° C (large temperature difference), proportional Using the idea of allocation, here, Where T _{i is the} calculated metal temperature of the division point i before correction T _i ′ is the calculated metal temperature of the division point i after correction, and (2) | T _o −T _N | <0.5 No. 24 at ℃ (small temperature difference)
Using the idea of parallel movement as shown in the figure, the correction calculation of the metal temperature distribution is performed by the equation T _i ′ = T _i − ( _TN − T _MO ) ... (15).

Next, the thermal stress calculation unit 1010 will be described. Here, using the result (metal temperature distribution) that has been calculated and corrected by the above method and stored in the metal temperature distribution storage unit 1006, the general portion (nozzle corner portion) of the evaluation point 205 is calculated by the following equations (16) and (17). Calculate the thermal stress of parts other than NC.

Where σ _θt : circumferential inner surface thermal stress σ _zt : axial inner surface thermal stress T _ave : metal volume average temperature E: Young's modulus α: linear expansion coefficient ν: Poisson's ratio T _im : storage of metal temperature at division point i Value T _om : Memorized value of inner surface metal temperature T _Nm : Memorized value of outer surface metal temperature Young's modulus E and linear expansion coefficient α in the above equation depend on the metal volume average temperature. It is desirable to determine by calculation.

Next, the internal pressure stress calculation unit will be described. Here, based on the pressure measurement value of the internal fluid,
Calculation is performed using equation (19).

σ _rp = −P _f ……… （18） Where σ _rp : radial internal pressure stress σ _p : internal pressure stress strength R _f : internal pressure D _i : pipe inner diameter t: plate thickness Based on the thermal stress and internal pressure stress calculated above, the main stress calculation unit 1012 Considering the stress concentration in the inner nozzle corner NC with respect to the general part of the evaluation point 205, the following (20) (21)
The principal stress at the inner nozzle corner is calculated by the equation (22).

σ _r = K _rp · σ _rp ……… (20) σ _θ = K _θt · σ _θt + K _θp · σ _p ……… (21) σ _z = K _zt · σ _zt + K _zp · σ _p ……… ( 22) where K _θt : circumferential thermal stress concentration factor K _ZT : axial thermal stress concentration factor K _rp : radial internal pressure stress concentration factor K _θp : circumferential internal pressure stress concentration factor K _zp : axial internal pressure stress concentration factor σ _r : Radial principal stress σ _θ : Circumferential principal stress σ _z : Axial principal stress In the above-mentioned embodiment, the calculated value of the internal fluid flow rate and the measured value of the internal fluid pressure are compared with respective reference values. Based on the result, the switching between the steady state and the non-steady state of the metal temperature distribution calculation model is executed, but the above switching may be executed depending on the open / close state of the superheater stop valve 6.

Next, a specific example of the remaining life calculation function block 1100 will be described. FIG. 6 shows a remaining life calculation flow. The calculation method will be described below along this flow.

First, the procedure of fatigue life calculation will be described.

First, in step 1101, the inner surface principal stress difference (S _{1 to} S ₃ ) is calculated by the following equations (23) to (25) based on the equations (20) to (22).
Ask by.

In _{S 1 = σ θ -σ z .........} (23) S 2 = σ z -σ r ......... (24) S 3 = σ r -σ θ ......... (25) then step 1102, the For each of the main stress differences S _{1 to} S ₃ calculated by the equations (23) to (25), the stress amplitude is captured, and the life consumption is calculated from the design fatigue diagram based on this.

For example, if the main stress difference S ₁ shows a temporal variation as shown in FIG. 7, the stress total amplitudes Z ₁ ^I and Z ₂ ^I for S ₁ can be obtained. Similarly for S ₂ and S ₃ , Z ₁ ^II , Z ₂ ^II , ..., Z ₁
^III , Z ₂ ^III , ... Can be obtained respectively.

In other words, from among the many minimum and maximum values appearing on the change curve of each principal stress difference, first, the minimum / maximum value pair with the maximum amplitude is picked up, and then the remaining minimum / maximum values are similarly picked up. Thus, for S ₁ , Z ₁ ^I , Z ₂ ^I ... (Z ₁ ^I > Z ₂ ^I > ...) For S ₂ Z ₁ ^II , Z ₂ ^II ... (Z ₁ ^II > Z ₂ ^II > ...) for S _{3 ^{is, Z 1 III, Z 2 III}} ... (Z 1 III> Z 2 III> ...) determined as in the.

Next, the total stress amplitude Z _i ^I , Z _i ^III (i = 1, ... n)
As shown in the following equation (26), the maximum value is sequentially selected and the stress piece amplitudes H ₁ , H ₂ , ... Are obtained.

In step 1103, the allowable number of repetitions N ₁ , N ₂ , ... Is obtained from the design fatigue diagram as shown in FIG. 8 in correspondence with the stress piece amplitudes H ₁ , H ₂ . In addition, the allowable number of repetitions of these
From the reciprocal of N ₁ , N ₂ , ... In step 1104, the following equation (2
Calculate the fatigue life consumption φf per cycle shown in 7).

Next, the procedure for calculating the creep damage life consumption will be described.

Regarding the temporal fluctuation of the main stress difference at the time of starting the boiler, if the one in the θ direction (circumferential direction) is schematically shown for the secondary superheater outlet pipe vicinity, it will be irrespective of whether it is cold start or hot start. It looks like Figure 9. That is, after starting, the pressure temporarily changes to the compression side, but then changes to the tension side as the pressure rises, and gradually relaxes after reaching the initial stress σ _A.

As for the creep damage life, as shown in FIG. 10, relaxation curves for various initial stresses σ _A are stored in a computer, and relaxation curves corresponding to the values of the initial stress σ _A are selected.
The stress σ (T) and the time width ΔT at the elapsed time T from the relaxation start point S of the stress relaxation curve shown in FIG. 11 (a) are obtained.

Then, using this σ (T), the fracture time tr (σ (T)) is obtained from the creep rupture curve as shown in FIG. 11 (b), and the creep damage during the above ΔT is obtained as Δt / tr. .

In step 1106 of FIG. 6, the stress σ _{θ in} the inner surface circumferential direction obtained by the equation (21) is in the compression direction (that is, the negative side in FIG. 9).
When it corresponds to step 1107, the process proceeds to step 1107,
It is checked whether the equivalent stress σ _M shown in the following equation (28) calculated in step 3 is the maximum value so far.

If it is the maximum, this and the average metal temperature at this time are stored in the memory.

When the stress σ _{θ in the} circumferential direction of the inner surface is changed to the tensile direction (that is, the positive side in FIG. 9), the metal average temperature is in the creep range in step 1108 (for example, 510 ° C for the secondary superheater outlet header pipe side). It is determined whether or not it entered.

When the creep region is entered, a creep holding time counter for counting the relaxation elapsed time T after the initial stress of the stress relaxation curve is started. Then, in step 1109, the initial stress σ _A is calculated.

FIG. 12 shows a detailed flowchart of the initial stress calculation in step 1109 of FIG. The procedure for calculating the initial stress will be described below with reference to this flowchart and FIGS. 13 to 17.

In the example of the stress-strain diagram shown in Fig. 13, the maximum equivalent stress on the compression side occurs when the initial point is at 0 point, and the value exceeds the compression-side yield stress Y ₁ at the temperature at that time. Indicates a path that has changed to the tensile direction and reached the maximum value σ _A , where σ _A is the initial stress, and its value is expressed by the following equation (29).

Further, when the initial stress exceeds the yield stress Y ₃ at the rated temperature, it becomes as shown in σ _A ′ in the figure, which is expressed by the following equation (30).

Here, E ₁ is Young's modulus at rated temperature, and F ₁ is high temperature tensile property gradient at rated temperature.

First, in step 1109A, using the stress-strain diagram shown in FIG. 13, the yield stress Y _{1 on} the compression side, the high-temperature tensile characteristic gradient F at the compression-side maximum stress generation temperature, and the compression-side maximum equivalent stress generation time Calculate Young's modulus E at temperature.

In the next step 1109B, as shown in FIG. 14, the compression-side maximum stress SB is calculated from the stress relaxation final value SO during the previous operation, the rated-operation equivalent stress σ _P2, and the compression-side maximum equivalent stress σ ₂ by the following equation ( 31)

_{SB = SO-σ P2 + σ} 2 ......... (31) Step 1109 and the compression side maximum stress SB and yield stress -Y ₁
The comparison is made in C. If SB <−Y ₁ , the process proceeds to step 1109D, and if not, the process proceeds to step 1109H.

In Step 1109D, the tensile side equivalent stress SA is shown in FIG. 13 at the first activation and at the second and subsequent activations.
It is calculated by the following equation (32) by the method shown in FIG.

The tensile side equivalent stress SA and the yield stress Y ₃ at the rated temperature are compared in step 1109E. If SA> Y ₃ , the process proceeds to step 1109F, and otherwise proceeds to step 1109G.

When shifting to step 1109F, that is, when yielding on both the compression side and the tension side, the initial stress σ _A2 is calculated by the following equation (33) as shown in FIG.

As shown in FIG. 14, the process proceeds to step 1109G, i.e., when the stress is relaxed and restarted after the boiler is stopped when SO reaches the initial stress σ when yielding on the compression side. _Ask for _A.

In Step 1109H, the tensile side equivalent stress SO is compared with the yield stress Y ₃ at the rated temperature. If SO ≦ Y ₃ , Step 1109H
Move to I, and if SO> Y ₃ , move to step 1109J.

When the process proceeds to step 1109I, that is, when the yield does not occur on the compression side or the tension side as shown in FIG. 15, the initial stress is
Since it does not change with SO, the initial stress σ _A1 ′ is set equal to SO.
Alternatively, the initial stress σ _A1 ′ is calculated.

When shifting to step 1109J, that is, when yielding on the tension side without yielding on the compression side as shown in FIG. 16, the initial stress σ _A2 ′ is obtained by the following equation (34).

Thus, the initial stress σ obtained in step 1109 is
Based on _A , in step 1110 of FIG. 6, first, the stress relaxation curve shown in FIG. 10 is used, and as shown in FIG. 18, the stress relaxation curve (chain line) to be applied by the interpolation method. Ask for. The solid line in FIG. 18 is the stress relaxation curve stored in advance.

Then, the creep damage life is calculated in the following manner in correspondence with the value T of the creep holding time counter.

The creep damage life calculation procedure is shown in Fig. 19 (a) to (c).
A description will be given according to the specific example shown in FIG. Figure 19 (a)
The applied stress relaxation curves are shown in (c).

The stress relaxation curve is the creep retention time on the horizontal axis (Fig. 9,
Elapsed time after the principal stress difference shows a peak value) 0.1,0.2,
The stress at 0.4, 0.7 and 1.0 hours is σ (0.
1), σ (0.2), σ (0.4), σ (0.7), σ (1.0) are given (that is, stored).

FIGS. 19 (a) to 19 (c) show that the creep holding time T is on the left side with respect to two intermediate time points adjacent to each other in the above time (in FIG. 19a, the intermediate point 0.55 of 0.4 and 0.7). (T is located on the left side of) and is on the right side with respect to the intermediate time point when it coincides with the above time point (in FIG. 19c, T is on the right side of the intermediate point 0.3 between 0.2 and 0.4). positioned)
Is represented.

In this example, the stress for creep damage evaluation is assumed to match the stress at the time point, and the duration ΔT is set by using this stress as a representative, so that the creep damage life consumption can be reduced. It is intended to simplify the calculation.

According to the example of FIG. 19 (a), the relationship between stress and its duration ΔT is as follows: σ (0.1) stress is ΔT ₁ = (0.15-0.1) hours, σ (0.2) stress is ΔT ₂ = It is assumed that the stress of (0.3−0.15) hours and the stress of σ (0.4) are held for ΔT ₃ = (T−0.3) hours.

In the example of FIG. 19 (b), the stress of σ (0.1) is held for ΔT ₁ ′ = (0.15-0.1) time, and the stress of σ (0.2) is held for ΔT ₂ ′ = (0.4−0.15) time. It is assumed that the
In the example of Figure (c), the stress of σ (0.1) is held for ΔT ₁ ″ = (0.15-0.1) hours, and the stress of σ (0.2) is held for ΔT ₂ ″ = (T−0.15) hours. I am assuming.

Here, σ (0.1), σ (0.2), σ (0.4), ...
The break times corresponding to are given as t ₁ , t ₂ , t ₃ , .... From them, creep damage life consumption φ _c
Are expressed by the following equations (35) to (37), respectively, in the case of FIGS. 19 (a) to (c).

Creep damage life consumption φ determined in this way
_{Based on c} and the fatigue life consumption φ _f , in steps 1111 and 1112 of FIG. 6, the total life consumption φ _i and the cumulative total life φ _T are calculated as follows.

First, in step 1111, the total life consumption φ _{i is} calculated by the following equation (38) for each cycle, that is, for each cycle i.

φ _i = φ _fi + φ _ci (...) (38) Next, in step 1112, the cumulative total life φ _T up to this N-th cycle is calculated by the following equation (39). Step 1113 calculates the allowable life per cycle as described above.

Therefore, as the reference data, for example, for each start mode, that is, for each cold start mode, warm start mode, and hot start mode, the allowable number of starts is N ^o _c , N ^o _W , N ^o _H , and the total life consumption _Are respectively assigned as φ ^o _TC , φ ^o _TW , and φ ^o _TH in the initial stage.

Therefore, the permissible life cycle consumption φ ^o _PC , φ ^o _PW , and φ ^o _PH corresponding to each mode are expressed by the following equation (40).

In accordance with this, the number of operations in each mode up to the i-th cycle is N ⁱ _C , N ⁱ _W , and N ⁱ _H , and the total life consumption is φ ⁱ _TC ,
Assuming φ ⁱ _TW and φ ⁱ _TH , the allowable life of the next cycle (i + 1) is calculated by the following equation (41) for each mode.

Here, the numerator of the equation (41) is the remaining allowable life, that is, the remaining life, and the denominator is the remaining allowable number of operations.

Next, the stress limit calculation function block 1200 (FIG. 1) will be described.

In this block, in the remaining life calculation function block 1100, the total life consumption φ _i calculated using the equation (38) and the maximum compression-side equivalent stress σ _M [determined by the equation (28)] in the cycle are calculated. By accumulating and learning, the diagram shown in Fig. 20 is updated and created for each cold, warm, and hot operation mode.

In FIG. 20, σ _{o on} the horizontal axis is the initial stress limit value, σ _{i + 1}
Is the stress limit value for the (i + 1) th cycle, φ _{o on the} vertical axis is the initial allowable life consumption (per cycle), φ _i is the total life consumption per cycle, and φ _{i + 1} is (i + 1) It shows the allowable life for each cycle.

Based on this diagram, in the block 1200 of FIG. 1, the stress that does not exceed the allowable life newly calculated by the equation (41), that is, in the example shown in FIG. 20, the stress corresponding to the intersection point P is newly added. Determined as the stress limit value.

The main steam temperature predicting unit 2000 shown in FIG.
As disclosed in the specification of Japanese Patent No. 429 (Japanese Patent Laid-Open No. 59-157402), it is formed from the functional blocks shown in FIG. 25, and n · Δt (however, n
Is an integer, Δt is the sampling cycle) and the main steam temperature after time
T _fp (j + n, i) is predicted.

As shown in FIG. 25, the main steam temperature T _f of the process detected values at time i is taken in as a calculation variable X ₁ (i) and input to the adder 131 together with the observation noise W (i). To be done.

The addition output of the adder 131 is input to the operation block 133 via the adder 132. The output of the operation block 133 is an adder
It is input via the delay element 135 and the first stage of the secondary superheater dynamic characteristic models 136-1 to 136-n provided in the n stage.

The secondary superheater input steam temperature TS is calculated as a calculation variable U ₁ (i) by the calculation block 136 of the secondary superheater dynamic characteristic model 136-0.
Entered in a. The output of the delay element 135 is input to the other calculation block 136b of the dynamic characteristic model 136-0.

The outputs of these arithmetic blocks 136a and 136b are the adders.
The addition is performed by 136c, and the addition signal is input to the adder 132 and the addition signal is input to the adder 134, respectively.

Although the internal description of the secondary superheater dynamic characteristic models 136-1 to n is omitted, it has the same configuration as 136-0.
Further, the process detection value necessary for the calculation is input to the secondary superheater dynamic characteristic model 136-0 as described later.

Next, the calculation operation of the steam temperature prediction unit 2000 will be described. Now, at time t, the main steam temperature T _f is X ₁ , the secondary superheater metal temperature T _M is X ₂ , the secondary superheater inlet steam temperature TS is U ₁ ,
Given that the secondary superheater gas temperature T _G is U _2, and considering the minute fluctuations of these variables near the steady state, and assuming that the heat transfer of the secondary superheater is a constant pressure process, the dynamic characteristic model of the secondary superheater is Formula (42)
It can be represented by ~ (49).

In the above formula, C _pi : Secondary superheater inlet constant pressure specific heat C _po : Secondary superheater outlet constant pressure specific heat WF: Secondary superheater internal fluid flow rate WFR: Secondary superheater internal fluid rated flow rate γ _s : Secondary Superheater internal fluid specific weight V: Secondary superheater internal volume FG: Boiler gas flow rate FGR: Boiler gas rated flow rate M _m : Secondary superheater metal weight C _m : Secondary superheater metal specific heat A _s : Secondary superheater heat transfer Area α _{gm, R} : Heat transfer coefficient in the rated state from gas to metal α _{ms, R} : Heat transfer coefficient in the rated state from metal to steam The above equations (42) and (43) are U ₁ , U Assuming that ₂ is held at the value at t = 0, the following equations (50) and (5
It becomes 1).

Based on these equations (50) and (51), the calculation cycle Δt (Δ
t = t−t ₀ ) When transformed into a discrete value type equation for obtaining X ₁ (Δt) and X ₂ (Δt) ahead of time, the following equation (52) is obtained.

In the above formula (52) X ₁ (Δt), X ₂ (Δ
Replace t) with X ₁ (O) and X ₂ (O), respectively, and repeat the operation of equation (52) n times to obtain n · Δ
It is possible to predict the main steam temperature T _f (n · Δt) and the secondary superheater metal temperature T _MO (n · Δt) after t hours.

The dynamic characteristic model of the secondary superheater expressed by equation (52) is
It corresponds to the block 136 surrounded by the alternate long and short dash line in FIG. In addition, in the same figure, in order to simplify the figure, it is expressed by the following equation (63) using an arbitrary time i.

(I) = (i-1). (I-1) + (i-1). (I-1) (63) Further, the process of observing the process detected value is expressed by the following equation (64). When the signal (i) Can be expressed by the following equation (65) by applying the Kalman filter theory.

(I) = (i) ・ (i) + (i) ……… (64) where (i): m-dimensional observation vector C (i): m × n observation matrix (i): m-dimensional observation noise vector here, (I) = { ^-1 (i) + C ^-1 (i) ^.- 1.C (i)} ^-1 ...
(67) (i) = (i-1). (I-1) '(i-1) + (i-1). (I-1).' (I-1) ...
(68) Is the value of the n-dimensional state variable vector at time i And is the same as (i) in the previous equation (63). (I) in the above equation is the r-dimensional system noise Is the same as. (I) is an n × n state transition matrix,
(I) is an n × r driving matrix.

As mentioned above, the main steam temperature T _f calculated value obtained by equation (63) Is passed through the Kalman filter to obtain a highly accurate predicted value.

The secondary superheater gas temperature U ₂ is obtained by calculating with the following equation (69).

Here, H _f : heat value of fuel, Hrg: enthalpy of recirculation gas, FS: fuel flow rate, HG: flow rate of recirculation gas, Ha: enthalpy of air, Cpg: specific heat of gas, FA: air flow rate, K: constant.

In the stress prediction function block 2100 of FIG. 1, based on the main steam temperature change rate R _sk from the optimum manipulated variable search function block 5000, the main steam temperature T _fp of the future is calculated by the following equation (n.Δt). 7
0) is used for estimation and prediction.

T _fp = T _f + R _sk · n · Δt ……… (70) where T _f : current main steam temperature Next, using the above main steam temperature T _fp , the same calculation method as the stress calculation function block 1000. At time j after n · Δt time To calculate.

However, in this embodiment, it is assumed that the various process amounts Da for calculating the internal fluid flow rate and the internal fluid pressure P _f do not change even after n · Δt time, and the metal temperature distribution calculation value is corrected by the outer surface metal temperature T _MO. No calculation is made.

On the other hand, when the load change rate is used as the manipulated variable, the load predicting function block 3000 (FIG. 1) selects N load change rates R ₁ > R ₂ > R ₃ ... Based on the load MW,
The load after n · Δt time (n sampling cycle ahead) is estimated by the following equation (71).

MWP _j = MW + R _j · n · Δt ……… (71) (j = 1,2,… N) And, from the main steam flow rate, fuel flow rate, and air flow rate corresponding to this predicted load, the above-mentioned main steam temperature Predict stress using prediction and stress prediction methods.

In the control evaluation function block 4000 of FIG. 1, the various quantities calculated above are defined as follows.

σ _L : Stress limit value _fj : Main steam temperature predicted value at time j T _sj : Main steam temperature set value at time j MWP _j : Load predicted value at time j MW _sj : Load command value at time j ε ₁ : Upper air stress limit value and stress prediction tolerance value epsilon _2: upper respiratory main steam temperature tolerance of the predicted value and the set value epsilon _3: selection from tolerance priority control selection function block 7000 of the upper respiratory load prediction value and the load command value, stress limit priority , The main steam temperature is prioritized, or the load is prioritized.

(1) When stress limit value is prioritized The following formula (72) Until the above condition is satisfied, the main steam temperature change rate R _sj and the load change rate R _{Lj are} searched by the optimum manipulated variable search function block 5000. And among the values that satisfy the above equation, the remaining evaluation value is expressed by the following evaluation function difference was a function _{(73) I 1j I 1j =} (fj -T sj) 2 + (MW j -MW sj) ² ... Outputs the value that minimizes (73) via the optimum manipulated variable output function block 6000.

(2) the main steam temperature priority if: (74) Equation | _fj -T _sj | R _sj until ≦ epsilon ₂ ......... (74) is satisfied, to explore the R _Lj, the values that satisfy the above equation , The evaluation value I _2j expressed by the following evaluation function (75) using the remaining deviation as a function The value that minimizes is output from the optimum manipulated variable output function block.

(3) When load is prioritized _Rsj , _RLj are searched until the following equation (76) | MW _j −MW _sj | ≤ ε ₃ ……… (76) is satisfied, and among the values that satisfy the above equation Then, the evaluation value I _3j expressed by the following evaluation function (77) with the remaining deviation as a function The value that minimizes is output via the optimum manipulated variable output function block 6000. In addition, any combination of formulas (72), (74), and (76) is possible.

If no priority is specified, the formulas (72), (74), (7
Search for R _sj and R _Lj that simultaneously satisfy 6). If a satisfactory solution cannot be obtained, the mode is set to steam (1) because the stress is large during the start-up bypass operation and the stop operation shown in FIG. ,
To prioritize rapid temperature change, go to mode (2), and after full load operation, go to mode (3) to prioritize load change.
Automatically switch each.

According to the present invention, even if the above equation (72) is not satisfied, in the next cycle, the stress limit value considering the current life consumption is reset, so that the life of the boiler is not shortened. However, the stress limit value per cycle thereafter becomes small.

In the above embodiment, the case where the stress evaluation point is one point has been described, but even in the case where there are a plurality of stress evaluation points, it is easy to set the stress limit value for each evaluation point. It goes without saying that the present invention can be applied to.

〔The invention's effect〕

According to the present invention, while suppressing the stress of the boiler thick wall pressure resistant portion within an appropriate limit value range commensurate with the operation history of the plant,
It enables safe and quick start, load, and stop operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, FIG. 2 is a time chart explaining the relationship between the present invention and boiler plant operation, and FIG. 3 is a block diagram of a conventional boiler plant control device. FIG. 4 is a schematic configuration diagram of a boiler plant to which the present invention is applied, FIG. 5 is a detailed block diagram showing an example of a stress calculation function block of FIG. 1, and FIG. 6 is a residual life calculation of FIG. 7 and 9 are graphs showing changes in principal stress difference, FIG. 8 is a graph showing changes in stress piece amplitude, and FIG.
10 and 11 are graphs showing examples of changes in stress, FIG. 12 is a detailed flowchart of the initial stress calculation procedure of FIG. 6, and FIG.
~ Fig. 17 is a graph showing the stress-strain relationship used for residual life calculation, Fig. 18 is a graph for explaining how to obtain the desired stress relaxation curve, and Fig. 19 is a procedure for creep damage life calculation. A graph showing a stress-time relationship for explaining,
FIG. 20 is a graph for explaining the operation of the stress limit value calculation function block of FIG. 1, and FIGS. 21-24 are diagrams for explaining the temperature distribution calculation means near the secondary superheater outlet header pipe. twenty five
The figure is a detailed block diagram of the main steam temperature predicting section in FIG. 1000 …… Stress calculation function block, 1100 …… Remaining life calculation function block, 1200 …… Stress limit value calculation function block, 20
00 …… Main steam temperature prediction function block, 2100 …… Stress prediction function block, 3000 …… Load prediction function block, 4000…
… Control evaluation function block, 5000 …… Optimal manipulated variable search function block, 6000 …… Optimal manipulated variable output function block, 7000
...... Priority control selection function block

Claims (12)

[Claims] Claim: What is claimed is: 1. A boiler stress monitoring control device for monitoring and controlling stress at an evaluation point set at a desired point of a boiler plant pipe, a means for calculating a current value of an internal fluid flow rate at the evaluation point, Means for calculating the metal temperature distribution at the evaluation point based on the internal fluid flow rate calculation value, means for calculating thermal stress based on the metal temperature distribution calculation value, means for calculating internal pressure stress from the internal fluid pressure, and A stress calculation unit composed of means for calculating the principal stress from thermal stress and internal pressure stress, means for calculating the remaining life at the evaluation point from the principal stress obtained by the stress calculation unit, and the remaining life calculation value Means for updating and calculating the stress limit value from, the stress predicting means for predicting the main stress at the evaluation point in the future, the main steam temperature predicting means for predicting the main steam temperature at the future simultaneous point, and the simultaneous point Oh Load prediction means for predicting a load, and at least one of a deviation of the stress prediction value from the stress limit value, a deviation of the main steam temperature prediction value from the main steam temperature set value, and a deviation of the load prediction value from the load command value. A means for setting the main steam temperature set value and the load command value so as to minimize the evaluation value obtained by an evaluation function in which the deviation is held as a variable and the remaining deviation is kept as a variable. Boiler stress monitoring and control equipment. 2. The boiler stress monitoring control device according to claim 1, wherein the prediction of the main steam temperature at a future time is performed based on the main steam temperature change rate and the current main steam temperature. 3. A boiler stress monitoring control apparatus according to claim 1, wherein the load prediction at a future time is performed based on the load change rate and the current load. 4. The main stress prediction at the evaluation point according to claim 1, the thermal stress obtained based on the metal temperature distribution, and the internal pressure obtained based on the pressure of the internal fluid and the size of the pipe metal. A boiler stress monitor and control device characterized by being calculated from both stresses. 5. The evaluation value obtained by an evaluation function using the remaining deviation as a variable according to claim 1,
A boiler stress monitor and control device which is characterized by the sum of the squares of the remaining deviations. 6. The method according to claim 1, wherein thermal stress at a future time is predicted by using the main steam temperature change rate as a parameter, and the deviation of the predicted thermal stress value from the limit value is within an allowable range. While setting the steam temperature set value and the load command value, predict the deviation between the main steam temperature set value at the future point based on the main steam temperature change rate and the main steam temperature predicted value at the future simultaneous point, and match the deviation. A boiler stress monitoring and controlling apparatus characterized in that the fuel bias is configured to be added to a fuel amount command value. 7. The main steam temperature according to claim 1, wherein thermal stress at a future time is predicted using the load change rate as a parameter, and the deviation of the predicted thermal stress value from the limit value falls within an allowable range. While setting the set value and the load command value, the change rate that minimizes the deviation between the load command value at the future time point based on the load change rate and the predicted load value at the future time point is determined, and water supply is performed in accordance with the deviation. And a boiler stress monitoring and control device characterized by operating fuel. 8. The main unit according to claim 1, wherein the stress is predicted for each of a plurality of different evaluation points, and the deviation of all predicted values from the stress limit value is within an allowable range. A boiler stress monitoring and control device characterized in that it is configured to set a steam temperature set value and a load command value. 9. The boiler according to claim 1, wherein the portion for calculating the metal temperature is constituted by a theoretical calculation model, and the calculation model is switched according to the state of the internal fluid at the stress evaluation point. Stress monitoring control device. 10. The theoretical calculation model according to claim 9, comprising a steady metal temperature distribution calculation model and an unsteady metal temperature distribution model, wherein at least one of the pressure and the flow rate of the internal fluid at the stress evaluation point is A boiler stress monitor and control device characterized by calculating the metal temperature distribution using the former model when the values are less than the specified value and the latter model when both values are the specified values or more. 11. The unsteady metal temperature distribution calculation model according to claim 10, comprising a portion for calculating the metal temperature distribution based on the calculated values of the temperature, pressure and flow rate of the fluid inside the stress evaluation point, and A boiler stress monitoring and controlling apparatus, characterized in that it is configured with a portion for correcting the metal temperature distribution by using an outer surface metal temperature measurement value at an evaluation point. 12. The correction amount of the metal temperature distribution according to claim 11, wherein the heat transfer coefficient on the inner surface of the metal at the evaluation point is the same in both the pre-correction and post-correction metal temperature distributions, and A boiler stress monitoring and controlling apparatus, characterized in that the temperature at each metal outer surface is determined so as to match the outer surface metal temperature measurement value.