JPS5930962B2 - How to automatically start a boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for starting a boiler whose plant characteristics change significantly during the start-up process so that the outlet temperature of a boiler reaches a predetermined temperature increase rate.

Traditionally, starting a boiler (boiler starting here refers to starting the boiler by igniting the burner of a stopped boiler to increase or decrease the amount of fuel to bring the boiler to a predetermined temperature increase rate, and then increasing the boiler outlet fluid (It does not matter whether it is a cold start or a real start), a particularly skilled operator increases or decreases the amount of fuel while monitoring the boiler outlet fluid temperature and boiler outlet gas temperature. One thing is done by doing this.

However, when the boiler is started, steam is not flowing to the superheater or reheater, so in order to prevent overheating of the superheater or reheater, the temperature increase rate of the boiler outlet fluid temperature and the boiler Strict limits are placed on the outlet gas temperature, so special care must be taken when increasing or decreasing the amount of fuel.

On the other hand, in recent electric power systems where thermal power generation has increased in proportion, it is necessary to start up thermal power plants as quickly as possible. It is becoming extremely difficult to start up safely within a set time.

For this reason, a high degree of automation using control computers and the like has become necessary.

However, there are problems with automatically starting the boiler, as listed below.

(1) The time constant of the boiler is large compared to the characteristics of the turbine and others.

By the way, in a turbine, the maximum time constant for a change in turbine speed in response to a change in steam amount is 2 to 3 minutes, whereas in a boiler, the time constant for a change in boiler outlet fluid temperature in response to a change in fuel amount is approximately 200 minutes and 100 minutes. About twice as big.

For a system with such a large time constant, the so-called feedback control method, which performs corrective action after a temperature deviation occurs, cannot improve the control characteristics.

(2) Changes in boiler startup characteristics have a large rate of change in degrees Celsius compared to changes in turbine and other characteristics.

When comparing the time constants mentioned above, the time constant of the turbine changes by 1 to 2 minutes, while the time constant of Boi 2 changes greatly from about 60 minutes to about 200 minutes.The reason for this is that the loss characteristics of the turbine On the other hand, in Boi 2, it is caused by changes in a number of parameters such as the specific weight and specific heat of the internal fluid.

For this reason, when starting a turbine, sufficient characteristics can be obtained by modifying the control parameters as a function of the turbine speed, but when starting a boiler, the control parameters cannot be modified using a single parameter.

(3) During the boiler startup process, no steam is allowed to flow into the superheater or reheater, so an upper limit is set on the temperature of the exhaust gas at the boiler outlet in order to prevent overheating of pipes, etc.

When the exhaust gas temperature rises above this upper limit, the amount of fuel is restricted to suppress the exhaust gas temperature to a predetermined value or less, but this must not interfere with the automatic activation of the boiler 2.

(4) As mentioned in (1), the time constant of the boiler outlet fluid temperature change with respect to the fuel amount change is long, so the follow-up of the control variable to the target value is poor (only the target value is changed according to a predetermined rate of change). If you do so, the control deviation will become thicker.

Furthermore, such an increase in control deviation leads to an increase in the amount of operation created by processing this deviation, and after the process control amount approaches the target value, it is likely to cause negative effects such as overshoot and bunching.

One object of the present invention is to provide a method that can be automatically activated with high precision so that the boiler outlet fluid temperature reaches a predetermined temperature increase rate.

Another object of the present invention is to provide a method for automatically starting the boiler in a safe and reliable manner without causing the exhaust gas temperature at the outlet of the boiler to exceed a predetermined limit value.

Another object of the present invention is to provide a method for automatically starting a boiler in the shortest possible time.

Note that objects and effects other than those described above will become clear from the following description and drawings.

The present invention employs a predictive control method to automatically discharge the boiler 2 so that the boiler outlet fluid temperature reaches a predetermined temperature increase rate.

In other words, to predict the boiler outlet fluid temperature after a predetermined time, calculate the enthalpy possessed by the current boiler outlet fluid from the boiler outlet fluid temperature at the present time, predict the enthalpy after a predetermined time from the state of change in this enthalpy, and calculate the enthalpy from the current boiler outlet fluid temperature. This is done by determining the corresponding boiler outlet fluid temperature.

On the other hand, a target value of the boiler outlet fluid temperature after a predetermined time is determined from the boiler outlet fluid temperature and a predetermined temperature increase rate.

Then, by adjusting the amount of fuel in the boiler according to the amount of deviation between the target value and the predicted value of the boiler outlet fluid temperature after a predetermined time determined as described above, the boiler outlet fluid temperature can be adjusted to a predetermined temperature increase rate. It will start automatically as follows.

The following explanation will be given for the case of boiler startup.

First, the configuration of the boiler 2 and its surroundings and the procedure for starting the boiler will be explained in detail with reference to FIG.

In FIG. 1, FWP is a feed water pump and PHP is a high-pressure feed water heater, which heats the feed water by extraction air from a turbine (not shown) and supplies it to the center of the boiler.

ECO is a energy saver and heats the feed water using boiler exhaust gas.

ff, PSH and SSH are the water wall, primary superheater and secondary superheater, respectively.
Next is the superheater.

FT separates steam and water in a flash tank.

RBT is a resistor bypass tube.

Also, 5H8V. S I (P RV and 5SHBV are the superheater stop valve, superheater pressure reduction valve, and secondary superheater bypass valve, respectively.

As is well known in such thermal power plants, boiler startup is subject to strict limitations on the rate of rise in fluid temperature at the boiler outlet and the temperature of the exhaust gas at the boiler outlet in order to protect the superheater and reheater (not shown). , and is generally activated through the following process.

(1) First, fully open valve SHP Rv# and valve 5f (SV) to start the feed water pump FWP, and then open the high pressure feed water heater f (PH, economizer ECO, water wall WW, and primary water heater P).
Fill SH with water.

Next, the outlet fluid pressure of the primary heating unit PSH is increased to the rated value.

(2) Next, ignite the boiler and start raising the temperature.

In this case, the internal fluid from the high-pressure feed water heater HPI (to the 7th rash tank FT is in a water state), so the secondary water heater S
SH is not vented.

For this reason, the boiler temperature increase is controlled by increasing or decreasing the amount of fuel so that the boiler outlet fluid temperature increases at a predetermined temperature increase rate.

(3) As the temperature continues to rise in this manner, steam is generated from the flash tank FT, and the steam pressure within the flash tank increases.

(4) When the steam pressure in the flash tank reaches a predetermined pressure, the superheater vent valve 5H8V is opened to vent the secondary weekly heater SSH and the turbine (not shown) to warm up the turbine.

(5) When warming up of the turbine is completed, the superheater pressure reducing valve 5HPRV is opened to increase the main steam pressure to the rated value.

(6) When the main steam pressure rises to the rated value and the main steam temperature rises to the rated temperature, the boiler startup is completed and normal operation begins.

Incidentally, when cold starting a boiler, it takes about 10 hours for the automatic boiler control device to be in a normal operating state and ready for operation.

In the above explanation, the boiler side and turbine side (not shown) are used until the internal pressure of the flash tank reaches a predetermined value.
and is separated by a heater pressure reducing valve 5HPRV and a superheater vent valve 5Hsv.

In the state up to this point, the boiler outlet fluid temperature means the temperature on the outlet side of the water wall WW.

Thereafter, when opening the valve 5H8V to start the secondary heating unit SSH, the boiler outlet fluid temperature means the so-called main steam temperature.

In the following explanation, the boiler outlet fluid temperature has the meaning as explained above.

FIG. 2 is a schematic block diagram showing the automatic starting method of boiler 2 according to the present invention, and shows the boiler outlet fluid flow rate θW of boiler B.
and boiler outlet gas temperature θg.

As mentioned above, when the boiler outlet fluid temperature θW rises to a predetermined level, the boiler characteristics, especially the boiler time constant, are long-term and large during fluctuations, so the so-called feedback control that is performed after a control deviation occurs, Sufficient controllability cannot be obtained.

For this reason, we have adopted a predictive control method for the temperature of the granules at the Gay 2 outlet.

In other words, first, the boiler outlet fluid temperature θW and this temperature θW
The determined temperature θW is obtained in advance in accordance with the above, and this is set as the target value θwr of θW.

On the other hand, the temperature θwp after the predetermined time is predicted from the temperature θW.

Then, the fuel amount is controlled so that the deviation between the target value θwr of the temperature θW and the predicted value θwp becomes zero.

The present invention uses the enthalbin of the boiler outlet fluid to predict the temperature θW.

Next, we will discuss its operation.

Although the present invention shown in FIG. 2 can be implemented in either digital or analog format, the following description will be made assuming that it is implemented digitally using a control computer.

First, when the predetermined preparatory operations before starting the boiler described in FIG. 1 are completed, the boiler is ignited.

By igniting the boiler, the boiler outlet fluid temperature θW necessary for starting the boiler is taken into the boiler starting part (the part surrounded by the dashed line in FIG. 2).

Next, when the operator issues a control start command, the main activation section is activated.

Further, the sampling means 2 samples the temperature θW at a predetermined period and inputs it to the starting valve indicated by the dashed line in Figure 2.

In the starting part indicated by the dashed-dotted line, first, the target value θwr(i+n) of the boiler outlet fluid temperature θW is set to blocks A and B.

Find it in C.

Block A provides the rate of change (that is, the output of temperature θW) to block B and block C in advance with respect to the boiler outlet fluid temperature θW.

As will be described later, block B determines the output of block A (target temperature θwr(i) at the time of rising ring).

Here, the gay 2 outlet temperature when control is started by the operator is used as the initial value of θW, and thereafter the target value θwr ("i-1) calculated in the previous block B is used.

It should be noted that, as in the following description, each code, for example, it lsp shown here with a kanph appended to θwr, is the temperature target value at the current sampling time.

In other words, θwr(i+1) and θwr(i-1) are each n
This is temperature target value information after the sampling period and one sampling period before.

A detailed functional explanation of this block B will be omitted here, as problems at the time of starting the boiler will be discussed in detail later.

Block C is the target temperature θwr(i-1) at the current sampling point 0w(i) obtained from block A.
From this, the target temperature θwr(i+
n) is obtained, for example, as in (IX).

However, only when a control start command is issued, since there is no target temperature θwr(i-1) at the previous sampling time, the actually measured value θwr(i) is used as the initial value instead.

This θwr (i + n) is used as the target value of the present predictive control.

On the other hand, the predicted value θw of the temperature θW from blocks D, E, and F
p is found.

The use of enthalpy in this prediction has an important meaning in improving the accuracy of the method of the present invention.

As described above, when the boiler is started, the fluid pressure at the ice wall outlet is controlled to be constant.

Therefore, the relationship between temperature θW and enthalpy H is uniquely determined, and can be obtained from the steam table as shown in FIG. 3, for example.

Prologues D, E, and F predict the boiler outlet fluid temperature θW after a specified time using the relationship shown in FIG. 3, and are performed as shown in FIG. 4, for example.

In other words, first, for the boiler outlet fluid temperature θW sampled and input at a predetermined period in the sampling means 2, the corresponding enthalpy H7 is
It is calculated using the steam table shown in Figure 3 at each sampling time.

In block E, the rate of change of the enthalpy at each sampling time point is determined from the plural pieces of enthalpy information at each sampling time point thus obtained.

Equation (2) is an example of calculating the enthalpy change rate ΔH(i) at the current sampling point by the least squares method.

However, [H(i) is enthalpy information obtained through temperature-enthalpy conversion, and the number within 0 represents the boiler outlet fluid temperature sampling time.

For example, H(i-3) is enthalpy information three sampling periods before the current sampling time.

Equation (3) is an equation for predicting the enthalpy after n sampling periods by the method of excluding from the rate of change obtained in this way.

, [i ten n) − nXΔH(i) +H(i)
-----...---(3) In block F, the enthalpy H(i
+n), the corresponding temperature θwp (i +n
) is determined from the steam table in Figure 3.

This is the boiler outlet fluid temperature predicted value θwp after n sampling periods.

Incidentally, the shorter the sampling period in the sampling means 2 is, and the more data is used, the more accurate predictions can generally be made.

However, from a practical point of view, the sampling period is about 1 minute, and it is usable to predict the temperature after 7 minutes from 4 pieces of data.

The predicted boiler outlet fluid temperature value is determined in degrees Celsius by utilizing the fact that temperature and enthalpy are uniquely determined when the pressure is constant, as explained above.

Predicting temperature using enthalpy can be expected to be more accurate than predicting directly from temperature.

In other words, the boiler outlet fluid temperature is determined as a function of enthalpy, and is affected not only by specific weight but also by specific heat, and therefore has characteristics that are more nonlinear than enthalpy.

Therefore, using enthalpy to predict temperature as in the present invention can further improve prediction accuracy.

In block J, the target value θwr(i+n) of temperature after n sampling periods obtained in block C and block F
The predicted temperature value θwp(
The combustion amount f of the boiler is controlled so as to match i+n).

G is an adder, and θwr (i + n) and θwp
Find the deviation e(i+n) of (i +n).

Control of this fuel amount f in block J is performed as shown in equation (4) below.

Δf=1Xe(i+n)t-Kp(e(i+n)-e
(i+n l)) (4) where, Δf: control output (the fuel amount f increases or decreases by an amount corresponding to this magnitude (+ increases, - decreases).

)K1; Integral control gain Kp: Proportional control gain e(i+n)*θwr(i+n)−θwr(i+n)θ
wr(i+n); Boiler outlet fluid temperature target value after n sample periods (output of block C) θwr(i+n); Boiler outlet fluid temperature predicted value after n sample periods (output of block F) Thus, the present invention Basically, proportional-integral control is used in this system, but since it is normal for plant characteristics to change significantly when starting with a gain of 2, a fixed control gain will not work well throughout the startup process. It is difficult to desire precise control characteristics.

Figure 5 shows the plant gain and plant time constant T at startup when the boiler is expressed as a first-order lag element.
FIG. 3 is a diagram illustrating an example of how .

According to this figure, the gain changes within a range of approximately 30 times, and the time constant changes within a range of approximately 3 times.

Therefore, in the present invention, the characteristics of the plant, that is, the characteristics of the boiler outlet fluid temperature change ΔθW with respect to the fuel amount change Δf, are assumed in a delay circuit, and the control gain is corrected according to changes in the plant time constant and gain. We are working to further improve control characteristics during plant startup.

Assuming that, if the n-characteristic equation for the entire system at the time of plant startup is determined from the control using equation (4), it is obtained as shown in equation (5).

22-(P11+P2°)Z0P1, P2°-Pl.

P2□-0・・・・・・(5) In the characteristic equation of equation (5), in order to obtain a response that quickly follows the target value without causing the system to oscillate, z1
=0. Letting z2-β(0×β<l), the proportional/integral control gain Kp of equation (4) is 1, as shown in (6).

It can be obtained as shown in equation (7).

The control gain adjustment section M in Fig. 2 is the proportional gain K expressed by equation (4).
p, the integral gain is adjusted to 1, and the °C boiler startup control is modified in accordance with the boiler fluid outlet temperature θW.

For example, by inputting the boiler outlet fluid temperature θW, the plant gain and the plant time constant T are determined from the block L representing the startup characteristics shown in FIG.

By substituting T into the blocks (6) and (7) and finding 1 for the proportional gain Kp1 and the integral gain, Kp and Kp of block J are controlled to 1 so that the plant startup is optimal.

Although FIG. 5 assumes that Boi 2 is a first-order lag circuit, it may be assumed that it is a higher-order lag circuit for more optimal control.

However, it has the disadvantage that the characteristic equation becomes complicated, and in practical terms, approximation with a first-order lag is sufficient as a method of sequentially correcting it online using a computer.

As described in detail above, in the present invention, the boiler outlet fluid temperature is sampled and introduced at a predetermined period, and the target value θwr and predicted value θwp of the temperature after a predetermined time are derived from the temperature θW at each sampling time. This is what is controlled so that they match.

At this time, the accuracy of temperature prediction is improved by not using a temperature signal to predict the fluid temperature at the boiler outlet, but by using enthalpy, which corresponds to this temperature and has relatively good linearity.

The boiler is started as described above, but when the boiler outlet gas temperature θg exceeds the specified value qtDt during the startup process, it is necessary to protect the tubes that are not draining water vapor within the boiler.

In the automatic startup method of the present invention, the boiler outlet gas temperature θ
g is constantly monitored, and when it exceeds a specified value, the above-mentioned predictive control is stopped and the gas temperature θg is suppressed to below the specified value.

Incidentally, θg is sampled and inputted at a predetermined period by a sampling means Z'.

As shown in FIG. 2, the boiler outlet gas temperature θg is compared with its specified value θgr in an addition section N.

Then, the comparator O detects that the gas temperature θg is larger than the specified value θgr (when θg>θgr, the output of the comparator O is 1), and the normally open contact S1 is closed and the normally closed contact is opened.

That is, the output of block J is stopped at contact S2, and instead, the output of a predetermined power source Q is applied to adder U via integrator R to reduce the fuel amount.

However, the polarity of the power source Q is selected to reduce the fuel amount f and the gas temperature θg.

Note that the comparator 0 has a hysteresis characteristic and prevents unnecessary bunching from occurring near θgr when the gas temperature θg returns to the specified value θgr.

In other words, in comparison section 0, the human power Δθg is negative (θg〉θgr
), the output is first output, and when 30g becomes a positive predetermined value θgo (θgr-θg≧Δθgo), the output is stopped (the output of the comparison unit O is 0).

Then, the contacts S□ and S1 return to their original states, and the boiler is started again by predictive control.

On the other hand, the method of the present invention has a function of correcting the target value θwr of θW at the initial stage of startup and when the boiler outlet exhaust gas temperature θg exceeds a predetermined value.

In other words, in the initial stage of startup when the control start command has just been issued, θW does not easily increase even if the fuel amount f is increased.
If the target value of θW is unilaterally increased, the deviation between θwr and θwp will increase, making it impossible to perform good control.

This deviation monitoring is realized by V and WC.

That is, V indicates an adder, and the deviation Δθ between θwr and θwp is determined.

Block W checks whether Δθ exceeds the specified value or 5, and if it exceeds it, it is "l", and if it does not, it is "0".
By outputting , it is determined whether or not target value correction is necessary.

In addition, if the target value θwr is increased while the exhaust gas temperature θg exceeds the specified value and the output of the block J is stopped, the actual fuel amount f and the required amount will be The deviation causes a large disturbance to the boiler.

Block P takes the OR of block W and 00 output, and outputs if either one outputs.

Hereinafter, in the method of the present invention, the operations for determining the target value θwr shown in blocks A, B, and C will be described in detail with reference to FIG. 70.

FIG. 6 is a program representation of the operation shown in FIG.

First, after the boiler is ignited, a control start command is issued to start 5 tarts, and if the boiler has not started, the boiler outlet fluid temperature θw(i) is sampled at a predetermined period and input.

If the boiler startup is completed, it will end without doing anything.

The sampling force θw(i) is the initial temperature information θw(o)
If (θW at the time of control start command), then θW(O)
The target value θw r (o) at the current sampling point according to
Determine.

For example, as shown in FIG. 1, first, the detected temperature θw(o) at the control start time to is set as the initial value of the target temperature θwr(-1) at the time t(-1) one sampling period before. Assume.

Then, from the preset temperature increase rate Δt corresponding to θwr(-1)=θW(o) and θwr(-1), the temperature is determined by the following equation.

represents the temperature increase rate set in degrees Celsius corresponding to the target value θwr (-1) before the programming cycle.

If it is the second or more time, the i-th sampling time t(i)
Find the target value θwr (i) at .

At this time, since the (i-1)th target value θwr (i-1) has been determined, the initial value of the temperature target at the i sampling time is θwr (i-1), which is determined by the target value (9).

However, as shown in block A, the temperature increase rate become

Therefore, the temperature when the temperature increase rate changes (θ1.θ2...
・If θwr (i-1) and θwr(i) exist between θwr(i-1) and θwr(i), correct θwr(i). Determine the accurate target value of °C.

Whether θk is between θwr(i-1) and θwr(i) can be determined by determining θwr(i-1) (θwr(i)).

When θk exists, the following υO), 0w according to the 00 formula
Modify r(i).

However, the target value θwr(i) at any sampling time point obtained in the above manner from the time point when the tk1 temperature reaches θ and the sampling time point ti-1 may be further calculated as necessary. 2
It is corrected by the target value correction signal (output of block p) shown in the figure.

As described above, the target value correction signal is issued when the target value and the actual measured temperature are different from each other, or when the gas temperature θg becomes abnormal.

First, let's talk about the former phenomenon, which tends to occur in the early stages of startup.

In other words, this is because the temperature does not rise easily even if the fuel is increased during startup.

As shown in Fig. 2, this means that the deviation between the temperature target value θwr(i-1) one sampling period before and the actual measurement value θw(i) at the current sampling time is calculated by the adder V and this deviation is 30
This is done by detecting the above using the comparing section W.

For example, at sampling time t1 in FIG. 7, 0w(i) and 0w r (o) are compared.

When θwr(i-1)-0w(i)≧Δθ, the target value θwr(i) is corrected.

This correction is made from 0w(o) to the target value θw at the time of control start command.
This is done in the same way as for finding r(o).

In other words, if 10wr (i - 1) + 0w (i) ≧ Δθ, the initial value of the temperature target '0wr (i - 1) is set to 0
Correct it to w(i).

That is, assuming that the temperature θw(i) at the current sampling time is the target value θwr(i-1) one sampling period before, it is determined by the following equation.

Next, we will discuss the latter case of gas temperature abnormality.

Generally, if θg exceeds 540°, it is considered abnormal.

When the gas temperature becomes abnormal, the abnormality is first memorized (FE=1
) and correct the target value θwr(i) using the formula a'a.

(Since this method has already been explained, it will be omitted.) Also, the fuel amount is decreased by Δf.

Then, it waits until the next sampling input is taken in.

This reduction in fuel amount is maintained until θg becomes, for example, 530° or less, and when it becomes 530° or less, the record of gas temperature abnormality is cleared (FE=0).

Sampling time t7 in FIG. At t8 and t9, the target value θwr(i) is corrected due to the gas temperature abnormality.

The gas temperature abnormality is solved at 530° C. (5) This is equivalent to giving the comparison section θ in FIG. 2 a hysteresis characteristic.

Next, the target value θwr(i+n) after n samplings is determined from the target value θwr(i) at the current sampling time.

To obtain θwr (i + n) from θwr (i), use (9), GO), and θ as described above in formula 00.
It is found by the same method as finding 0w r (i) from wr (i-1).

First, θwr (i 10 n ) is determined. The temperature θk when changing the heating rate is θwr(i) and θwr(i+n
), θwr(i+n) is corrected.

However, it is assumed that there is at most one θ between θwr(i) and θwr(i+n).

In this way, the n sun 7' I of the boiler outlet fluid temperature
The target value θwr(i+n) after J-ing is determined.

Although the flowchart describes all of the operations shown in FIG. 2, explanations other than those for determining the target value will be omitted since it is believed that the explanation of FIG. 2 can be sufficiently understood.

However, in No. 6-), e(i+n) is the target value θwr (i + n) after n samplings and the predicted value θwp
(i+n), and P (i) is calculated by setting the deviation e(i-Z+n) one sampling period before as 0 for the odor hair at the start of control (first sampling).

FIG. 8 is a diagram showing the control characteristics of the boiler outlet fluid temperature when the present invention is applied, and as can be seen from the figure,
During the Gay 2 startup process, the maximum temperature deviation is within about 10°C, providing good and safe control.

As described in detail above, in the present invention, the boiler outlet fluid temperature is introduced by sampling, the target temperature value and the predicted value are derived from the temperature at each sampling time, and the target value and the predicted value of the temperature are controlled so that they match. At this time, the accuracy of temperature prediction is improved by not using a temperature signal to predict the boiler outlet fluid temperature, but by using a conturbi with relatively good linearity corresponding to this temperature.

Furthermore, in the present invention, in order to perform proportional-integral control that corresponds to changes in boiler characteristics such as gain time constant when starting the boiler, the boiler is approximated by a delay circuit, for example, a first-order delay circuit, and the gain of proportional-integral control is adjusted according to changes in the characteristics. By optimally adjusting the time constant, etc., the accuracy during boiler startup is further improved.

Although the present invention has been explained with reference to a block diagram having each function in FIG. 2, the present invention can be implemented by a control computer according to a flow diagram in FIG.
ct Digital Control) control is also possible, and automatic startup of the boiler can be easily performed.

In addition, in the present invention, the first-order delay was explained as an example, but
In order to obtain higher starting accuracy, an n-th order delay circuit may be used, but this inevitably complicates the calculations for determining the gain and time constant.

Further, in the present invention, only the boiler outlet fluid temperature θW is input at the time of the control start command, and it does not matter whether it is a real start or a cold start.

Switching from manual to automatic operation can be done smoothly.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a commonly used boiler and its surroundings, Fig. 2 is an example diagram expressing the boiler automatic starting force method of the present invention as blocks for each function, and Fig. 3 is a diagram showing the configuration of a commonly used boiler and its surroundings. Figure 4 is a characteristic diagram showing the relationship between the enthalpy possessed by the boiler and the boiler outlet fluid temperature when the boiler internal pressure is constant. Fig. 5 is a block diagram to explain what to predict, Fig. 5 is a characteristic diagram to explain that the plant gain and time constant of boiler 2 vary depending on the magnitude of the boiler outlet fluid temperature, and Fig. FIG. 2 is a flowchart showing a program when the present invention is implemented by a control calculator, and FIG. 1 explains how the temperature target value at the current sampling point is corrected and determined in accordance with the target value correction signal. FIG. 8 is a characteristic diagram showing changes in the boiler outlet temperature, gas temperature, and fuel amount with respect to the temperature target value when the boiler is started according to the method of the present invention. A...Target temperature increase rate setting block, B...
・Target temperature determination block at the current sampling point, C...
...Block for determining the target temperature after n sampling, D ...Temperature-enthalpy conversion block, E
...Enthalpy prediction to Bron F...Enthalpy-temperature conversion block, 09 mouth, V, N...
... Addition section, J... Block for adjustment operation,
L・----Block for simulating boiler characteristics, M...
Block that adjusts control gain.

Claims (1)

[Scope of Claims] 1. An automatic boiler startup method for controlling the boiler outlet fluid pressure to a constant level when the boiler is started, comprising a temperature sampling means for sampling and inputting the boiler outlet fluid temperature at a predetermined cycle; The first step is to calculate the enthalpy of the outlet fluid for each sampling value of the boiler outlet fluid temperature.
A step of calculating the current rate of change in enthalpy from the enthalpy value at the past sampling point among the outputs of the first step, and predicting the enthalpy after n samplings from this rate of change and the enthalpy value at the current sampling point. Step 2: determining the boiler outlet fluid temperature after n samplings in accordance with the predicted enthalpy after n samplings; determining the temperature increase rate in response to the boiler outlet fluid temperature sampled by the temperature sampling means; The fourth step is to determine the target value of the boiler outlet fluid temperature after the n samplings from the initial value of the target value of the boiler outlet fluid temperature and the predetermined temperature increase rate, and at the beginning of startup, calculate the target value of the boiler outlet fluid temperature at that time. The fifth step uses the boiler outlet fluid temperature as the initial value (7) of the boiler outlet fluid temperature, and thereafter uses the previous target value as the initial value of the boiler outlet fluid temperature (7), depending on the deviation type between the third step and the fifth step. and an adjustment step for controlling the amount of fuel given to the boiler 2 by adjusting the deviation between the target value of the boiler outlet fluid temperature at the previous time point in the fifth step and the boiler outlet fluid temperature at the current sampling time point of the temperature sampling means is a predetermined value. A method for automatically starting a boiler, characterized in that when the current temperature sampling means becomes larger, the output of the current temperature sampling means is used as the initial value of the target value of the current boiler outlet fluid temperature in the fifth step. 2. In the method for automatically starting the boiler 2 described in claim 1, when the boiler exhaust gas temperature rises above a predetermined value, the current boiler outlet fluid temperature obtained through the temperature sampling means is measured in the fifth step. A method for automatically starting a boiler, characterized in that the target value of the current boiler outlet fluid temperature is set as an initial value. 3. A method for automatically starting a boiler according to claim 2, characterized in that if the boiler exhaust gas temperature rises above a predetermined value, the amount of fuel given to the boiler is reduced.