JPH02242012A - Boiler combustion control search method and device - Google Patents

Abstract

PURPOSE:To search a manipulated variable in the boiler operation so as to keep the unburnt contents of ash below a predetermined value and the NOx value below an environment regulation value by estimating the variation in the evaluation index of the state of combustion for the variation in the manipulated variable when it is changed imaginarily and estimating the variation in the proportion of unburnt contents in the ash by the variation in the evaluation index of the state of combustion. CONSTITUTION:A picture of the flame 2 of a burner is transmitted to a photoelectric conversion device 5 through a bundle of optical fibers which is cooled by a cooling pipe 3, and there the picture is converted to electric signals. After those electric signals are sent to an A/D converter 7 to be changed into digital data, they are stored in a picture memory 8. The picture data stored in the picture memory 8 is processed by a computer 9. A CRT 10 connected to the computer 9 displays data inputted to the computer 9, the manipulated variable which makes minimum the proportion of unburnt content in the ash and keep the value of NOx below a regulation value, proportion of unburnt content in the ash that is actually measured, regulation value of NOx, etc. and a boiler controller 11 receives the manipulated variable outputted from the computer 10 and carries out the operation so as to keep the proportion of unburnt content in the ash minimum and the NOx value below the regulation value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and an apparatus for searching the manipulated variable for combustion control of a boiler, and in particular to a method for reducing unburned content in the ash of a pulverized coal-fired boiler. The present invention relates to a boiler combustion control search method and apparatus suitable for searching for a manipulated variable to control the combustion.

[Conventional technology]

Conventionally, the only way to adjust the combustion is to adjust the combustion so that C○ is balanced in the furnace during a test run. Further, during operation, only the control is performed so that the gas 0□ at the furnace outlet is kept constant.

Although there is a method for macroscopically estimating the unburned content in the ash as described in JP-A-62-123218,
Operational adjustments based on the Ox value and unburned content in the ash relied on the experience and intuition of the operators.

[Problem to be solved by the invention]

In the above conventional technology, NOx is kept below the environmental regulation value.
Adjusting the combustion inside the boiler to minimize the amount of unburned content in the ash used to rely on the experience and intuition of operators, but in modern boilers for thermal power generation, many methods are used to stabilize the fuel supply source. It has become customary to use different types of foreign charcoal,
This complicates the combustion adjustment by the operator, and as mentioned above, it is difficult to achieve combustion that keeps NOx below the regulation value and minimizes unburned content in the ash, depending on the operator's experience and intuition.

An object of the present invention is to search for a boiler operation amount that will keep the unburned content in the ash below a predetermined value and the NOx value below the environmental regulation value for any type of coal handled.

[Means to solve the problem]

The above purpose is based on the relationship between the operation amount of the boiler, the combustion state evaluation index obtained from the brightness distribution of the burner flame produced by the operation amount, and the unburned content in the ash generated corresponding to the combustion state evaluation index. By estimating the amount of change in the combustion state evaluation index with respect to the amount of change by virtually changing the This is achieved by a boiler combustion control search method that searches for a manipulated variable for which the amount of combustion is less than or equal to a predetermined value. From the relationship of the unburned content in the ash that occurs in response to the state evaluation index, the amount of change in the combustion state evaluation index is estimated with respect to the amount of change in which the manipulated variable is virtually changed, and the estimated amount of change in the combustion state evaluation index is estimated. This is achieved by a boiler combustion control search method that searches for a manipulated variable for which the unburned content in the ash is equal to or less than a predetermined value by estimating the amount of change in the unburned content in the ash.

The manipulated variable is the amount of air supplied to the boiler,
It is appropriate to set the amount of fuel, the temperature of the fuel, the opening degree of an air register damper that adjusts the mixing state of the air and the fuel, the vane angle, the amount of gas recirculation of the boiler, and the two-stage combustion ratio. It is.

Further, the burner flame is generated from at least one of a plurality of burners arranged in the boiler.

In addition, after determining the operating amount of the boiler at which the unburned content in the ash becomes equal to or less than a predetermined value, the operating amount and NOx in the boiler exhaust gas are calculated.
It is better to confirm that the NOx value for the manipulated variable is below the regulation value from the actual value of the NOx value.
If the value does not fall below the regulation value, it is necessary to change the predetermined value of the unburned content in the ash.

Furthermore, the above object includes, as an apparatus, an image detection means for detecting an image of a burner flame of a boiler, a combustion state evaluation index calculation means for calculating a combustion state evaluation index of the burner flame from an image of the burner flame; a change operation amount input means for inputting a virtual amount of change in the amount of operation of the boiler used for the burner flame; and operation of the boiler based on the amount of virtual change in the amount of operation of the boiler and the combustion state evaluation index of the burner flame. The combustion state evaluation index calculation means after the change calculates the combustion state evaluation index of the burner flame after the amount change, and the unburned content in ash calculation means calculates the unburned content in the ash of the boiler from the combustion state evaluation index. This is achieved by using a boiler combustion control search device.

[Effect]

In the combustion process of pulverized coal particles, volatile matter is decomposed and burned at the beginning of combustion, and then surface combustion of coke-like residual carbon (char) progresses.

Since the surface combustion of char is slower than the decomposition and combustion of volatile matter, most of the time required for the pulverized coal to completely burn out can be considered to be the time required for the surface combustion of char.

This decomposition and combustion of volatile matter is very short, but during this time the pulverized coal particles undergo an expansion phenomenon (the char becomes porous and its surface area increases), and this expansion increases the subsequent combustion rate of the char. and has a large effect on the amount of unburned matter in the ash. The faster the expansion occurs and the larger the amount of expansion, the better the surface combustion of the char. Therefore, in order to reduce the unburned content in the ash, it is necessary to We need to encourage this phenomenon.

To achieve this, it is necessary to rapidly release the volatile matter from the pulverized coal particles after the pulverized coal particles are ignited, so that the volatile components are sufficiently ejected and combusted before the molten ash produced by surface combustion of the char covers the surface of the pulverized coal particles. If the flame temperature rises rapidly near the burner outlet, the expansion of the pulverized coal particles will be promoted and the unburned content in the ash will be reduced.

In the present invention, the amount of unburned matter generated in ash during pulverized coal combustion is
As mentioned above, this method was developed based on the fact that the degree of temperature rise after ignition of pulverized coal particles strongly depends on the temperature distribution (or brightness distribution) of the burner flame in the flame ejection direction. The temperature distribution of the burner flame is determined by the amount of combustion air supplied to the flame, the amount of fuel, the temperature of the fuel, the air register damper function that adjusts the mixing state of the air and the fuel, the vane angle, and the combustion gas. This was done by focusing on the fact that the amount of recirculation and the two-stage combustion ratio depend on boiler operating variables.

In the boiler combustion control search method, a method for determining a combustion state evaluation index indicating the brightness distribution of the burner flame depending on the operating amount of the boiler will be explained with reference to FIG.

FIG. 3 shows an image of the burner flame obtained by the image detection means, with the distance X from the tip of the burner 16 on the X axis.

The burner flame image width distance is expressed three-dimensionally on the y-axis and the brightness of the burner flame is expressed in the height direction, that is, the z-axis. Here, calculate the brightness integral value S (x) in the y-axis direction of the brightness at the distance X from the tip of the burner 166. For example, x=a
Here, the luminance integral value is denoted by S (a), and at x=b and x=c, respectively, s (b).

It is shown as S (c). Using this luminance integral value S (x), the luminance rise index xb(
Combustion status evaluation index determined from burner flame brightness distribution)
to evaluate the brightness rise of the burner flame.

E, =/- and stop d, (1)a
X According to equation (1), the brightness near the burner tip is a weighted and integrated value, so the sharper the brightness rise of the burner flame (the higher the brightness of the flame near the burner tip), the brightness rise index Engineering.

becomes larger.

Next, boiler operation variables (supplied air amount, fuel amount, temperature of the fuel, air register damper opening that adjusts the mixing state of the air and fuel, vane angle, boiler gas recirculation amount, and two-stage combustion A method for estimating the amount of change in the combustion state evaluation index when changing the ratio) will be explained with reference to FIG. In the second @, the horizontal axis represents the boiler operation amount U, and the vertical axis represents the combustion state evaluation index E, and the relationship between the boiler operation amount and the combustion state evaluation index is represented by a smooth curve. The amount of operation at the time when the image of the burner flame was obtained.

uo, and created a combustion state evaluation index that indicates the rise in flame brightness at that time. (xb), then the manipulated variable is Δ
When only U is changed, the combustion state evaluation index 11 changes by Δk, and the combustion state evaluation index 11 after changing the manipulated variable becomes the following (2
) is obtained by the formula.

I,=I. A method for estimating unburned content in ash at the furnace outlet of a boiler with an n-stage burner arrangement will be described using the combustion state evaluation index after changing the manipulated variable obtained by +Δ engineering.

The combustion state of each stage burner varies depending on the combustion state in the trailing region of the flame, the coal properties, the residence time of coal particles, etc., and the unburned content in the ash that is generated is affected by these factors, so the unburned content in the ash is estimated. In order to achieve this, the combustion state evaluation index of each stage burner is weighted as follows.

Ill': Weighted burner combustion state evaluation index I
ii: Before weighting 〃: Coefficient determined by coal properties fi: Fuel amount of i-stage burner f: Total input fuel amount Using weighted I Estimate unburned content.

(100-c)=gz・Izl"gx・Lx"-gn・
Inn (4) gi (i=1-〇): Coefficient determined by oxygen concentration in the furnace, etc. C: Unburned coal skewer (%) A: Coal ash content (%) U: Unburned content in ash (%) Above, burner A method for estimating unburned content in ash has been shown using the flame brightness rise index Ib as a combustion state evaluation index, but by replacing the burner flame brightness rise index 1b with the burner flame temperature rise index, the above method can be used. The unburned content in boiler ash can be estimated using exactly the same process. In that case, the temperature may be plotted on the Z-axis in FIG. 1, and the temperature rise indicator may be determined by the above formula.

As described above, once the combustion state evaluation index is obtained based on the image of the flame during combustion, and the unburned content in the ash is estimated based on this combustion state evaluation index, the current boiler operation amount can be virtually calculated by ΔU. only changed.

The amount of change (Δ
(2) is calculated based on the relationship between the manipulated variable and the combustion state evaluation index as shown in Figure 2.
The combustion state evaluation index I after the change in the boiler operation amount is calculated by the formula, and after this combustion state evaluation index I is weighted by the formula (3), the change in the boiler operation amount is calculated by the formula (4). The unburned content in the ash is estimated. This operation is repeated to search for the required amount of boiler operation in order to reduce the unburned content in the ash to the target value or less.

In the method according to claim 5, furthermore, when the boiler operation amount that makes the unburned content in the ash equal to or less than the target value is determined, the NOx generation amount corresponding to the determined boiler operation amount is equal to the conventional boiler operation amount. , is calculated based on the actual value of the NOx generation amount, and it is determined whether the calculated NOx value is below the regulation value.

In the method according to claim 6, if the NOx value calculated based on the manipulated variable that makes the unburned content in the ash less than or equal to the target value exceeds the regulation value, the target value for the unburned content in the ash is not respected. First, the manipulated variable is virtually changed in the direction in which the NOx value decreases based on the actual value showing the relationship between the manipulated variable and the NOx value, and the NOx value is reduced.
The value of the manipulated variable that causes the Ox value to be less than the regulation value is output as the final manipulated variable.

According to the combustion control search device according to claim 7.

First, the burner flame is imaged by the image detection means. Based on the brightness distribution or temperature distribution of this flame image, a combustion state evaluation index of the flame is determined by the evaluation index calculation means, and based on the determined combustion state evaluation index, the unburned content in the ash is determined. It is determined by the unburned content calculation means. Furthermore, with respect to the boiler operation amount at the time when the burner flame is imaged, a virtual change amount for virtually changing the operation amount is inputted by the change operation amount input means, and this virtual change amount and the combustion Based on the state evaluation index, the combustion state evaluation index after the manipulated variable has been changed is calculated by the changed fuel state evaluation index calculation means based on the relationship between the manipulated variable and the combustion state evaluation index that has been determined in advance. Next, the unburned content in the ash after the change is calculated by the unburned content in the ash calculation means based on the combustion state evaluation index after the changed operation amount.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram showing the main configuration of a combustion control device for a boiler which is an embodiment of the present invention, and FIG. 4 is a flowchart showing an embodiment of a combustion control search method. The image of the burner flame 2 ejected from the burner installed in the furnace 1 (boiler) is photoelectrically converted through the optical fiber bundle 4 cooled by the cooling tube 3 (the objective section is purgable to prevent soot adhesion). It is transmitted to device 5 where it is converted into an electrical signal. The electrical signal is transmitted to an analog/digital converter (hereinafter referred to as AD converter) 7 via a signal cable 6, converted into digital data, and then stored in an image memory 8.

The image data stored in the image memory 8, in which the optical fiber bundle 4, the photoelectric conversion device 5, and the AD conversion device 7 constitute image detection means, is processed by a computer 9, and the CRTIO connected to the computer 9 is , displays the data input to the calculator 9, the operation amount to minimize the unburned content in the ash and the NOx value below the regulation value, the measured value of the unburned content in the ash, the NOx regulation value, etc.
The boiler control device ull receives the manipulated variable output from the computer 10 and performs the operation so that the unburned content in the ash is the minimum and the NOx is below the regulation value.

The computer 9 includes the following circuits as shown in FIG. That is, it is connected to the image memory 8.

connected to a burner flame image input circuit 36 into which burner flame images of each stage are input;
A combustion state evaluation index calculation circuit 40 is a combustion state evaluation index calculation means that calculates and outputs a combustion state evaluation index based on a burner flame image, and the combustion state evaluation index calculation circuit and a changed manipulated variable are changed manipulated variable input means. A changed combustion state evaluation index calculation circuit 41, which is a changed combustion state evaluation index calculation means, is connected to the input circuit 37, and a changed combustion state evaluation index calculation circuit 41 is connected to the coal property input circuit 38. An unburned content in ash calculation circuit 42 which is an unburned content in ash calculation means, and a comparison of unburned content in ash connected to the unburned content in ash calculation circuit 42 and the unburned content in ash target value input circuit 39. The circuit 43 is connected to the NOx actual value input circuit 48 after the manipulated variable change which is connected to the changed manipulated variable input circuit 37, the NOx actual value input circuit 48 after the manipulated variable change, and the NOxllt limit input circuit 45. NOx regulation value comparison circuit 44, unburned content in ash/NOx value determination circuit 49 connected to the unburned content in ash comparison circuit 43 and NOx regulation value comparison circuit 44, and NOx regulation value comparison circuit 44. and an optimum operation amount output circuit 47 connected to the unburned content in ash/NOx value determination circuit 49.

Combustion state evaluation index calculation@ro calculates the brightness rise index K or temperature rise index N of the burner flame based on the input flame image data, and calculates the obtained index I.
b or h is output to the changed combustion state evaluation index calculation circuit 41 as a combustion state evaluation index.

The change operation amount input circuit 37 receives an input of the amount of change in the virtual operation amount with respect to the operation amount of the boiler (hereinafter referred to as the operation amount) in the state where the burner flame image is detected, and this change amount After changing the combustion state evaluation index calculation circuit 41
, the optimal manipulated variable output circuit 47, and after the manipulated variable change NO
The x actual value is output to the Kugata circuit 48.

The changed combustion state evaluation index calculation circuit 41 receives the combustion state evaluation index and the amount of change in the manipulated variable as input, and calculates the changed combustion state at the manipulated variable that has changed by the inputted amount of change from the manipulated variable at the time of detecting the burner flame image. An evaluation index is calculated and sent to the unburned content calculation circuit 42.

The coal property input circuit 38 receives the properties of the pulverized coal that is the fuel, which differ depending on the type of coal, in accordance with the type of coal being burned, and outputs the required data to the unburned content in ash calculation circuit 42 .

The unburned content calculation circuit 42 calculates the post-change combustion state evaluation index I!
! ! (or combustion state evaluation index) and the properties of the type of coal being burned (e.g. coefficient and ash content %), the combustion state evaluation index is weighted to calculate the unburned content in the ash, and the It is output to the unburned content comparison circuit 43.

The unburned content in ash comparison circuit 43 compares the unburned content in ash target value inputted via the unburned content in ash target value input circuit 39 and the unburned content in ash inputted from the unburned content in ash calculation circuit. Compare with the value of
A signal indicating whether or not the value is below the target value is output to the unburned content in ash/NOx value determination circuit 49.

The NOx actual value input circuit 48 receives the manipulated variable and the changed amount of the manipulated variable when detecting the burner flame image, and inputs the NOx actual value input circuit 48 based on the conventional performance corresponding to the changed manipulated variable.
The value is output to the NOx regulation value comparison circuit 44.

The NOx regulation value comparison circuit 44 compares the NOx value, which is a conventional actual value corresponding to the manipulated variable after the change, with the NOx regulation value inputted via the NOx regulation value input circuit 45,
A signal indicating which one is larger is output to the unburned content in ash/NOx value determination circuit 49 and the alarm output circuit 46.

The unburned content in ash/NOx value determination circuit 49 receives a signal indicating whether the unburned content in the ash is higher or lower than the target value and a signal indicating whether the NOx value is higher or lower than the regulation value, and determines whether the unburned content in the ash is higher or lower than the regulation value. When the fuel content is lower than the target value and the NOx value is lower than the regulation value,
A manipulated variable output signal is output to the optimal manipulated variable output circuit 47.

The alarm output circuit 46 issues an alarm (audio, light, etc.) when a signal indicating that the NOx value is larger than the regulation value is input.The optimum manipulated variable output circuit 47 issues a change when a manipulated variable output signal is input. The amount of change in the manipulated variable input from the manipulated variable input circuit 37 is output to the CRTIO and the boiler control device 11.

Next, a method of searching for the operating amount of the boiler in order to make the unburned content in the ash reach the target value will be explained according to the steps of the flowchart shown in FIG.

Step 100: Setting the target value of unburned content in ash, etc. (1) Set the target value of unburned content in ash to, for example, 5% or less.

This is because the ash left after burning coal can be used as an admixture for concrete, but to use it as an admixture, the unburned content in the ash must be reduced to approximately 5% or less. .

(2) Set past actual values of unburned content in the ash for boiler operation amounts that vary depending on the type of coal handled (mixed coal ratio), boiler load, etc. In addition, if a disturbance occurs due to a change in coal type, load change, etc., it is necessary to reset the settings. In addition, various coefficients that differ depending on the coal properties and the relationship between the boiler operation amount and the NOx actual value in the exhaust gas are set.

(3) Set the NOx regulation value.

Step 110: Evaluate the flame combustion state of each stage burner
The image data of the burner flame obtained by the boiler combustion control search device explained in the figure is processed by the computer 9 in the method shown in FIG. 3, and the combustion state is evaluated by the brightness rise of the flame. In this evaluation, it is desirable that the 0 image data, for which it is effective to perform noise removal etc. as pre-processing, be data obtained by averaging the detection results of several times.

FIG. 3 is a diagram showing a flame image three-dimensionally, with the brightness of the flame image on two axes, the distance from the burner tip on the xttx axis, and the burner flame image width distance on the y axis. Let S (x) be the integral value of the brightness of the burner flame in the y-axis direction at the distance X from the burner tip, for example, x=a, x=b,
The integral value of the brightness of the burner flame at each x=c is:
5(a) (20 in the figure)S(b) (21 in the figure), 5(c)
(22 in the figure).

The burner flame brightness rise indicator is as follows (1
) to evaluate the brightness rise.

X: Distance from burner end a: Value as close to the burner tip as possible do.

According to equation (1), since the brightness near the burner end is a weighted integral value, the brightness rise index 1b becomes larger as the brightness rises more rapidly.

Furthermore, it is also possible to use the temperature distribution of the burner flame instead of the luminance rise index described above to evaluate the combustion state based on the flame temperature rise. FIG. 5 shows an example of an apparatus configuration for determining the flame temperature distribution. The burner flame 2 of each stage is captured as an image through an optical fiber bundle 4 cooled by a cooling pipe 3, and a spectrometer 23 captures the wavelength λ1. The luminance of wavelength λ2 is separated and photoelectrically converted by the photoelectric conversion device 5, and analog/
The digital converter 7 converts the signal into a digital signal.

Each wavelength λ8 converted into a digital signal. The flame image of λ2 is stored in the image memory 8. Each wavelength λ,.

The flame image of λ2 is subjected to the following processing by the computer 9 to determine the temperature distribution of the burner flame.

According to the equation of W i e n , the wavelength λ8. The relationship between the brightness and temperature of each coordinate point of λ2 is shown by equations (7) and (8).

However, Rt(itj): Luminance Rx of wavelength λ of (isj) coordinates
(itj): Brightness ε1 of wavelength λ2 at coordinate (im, i):
Effective emissivity i2 of wavelength λ, effective emissivity λi of two wavelengths λ2: wavelength λ□: wavelength T(i, j) = absolute temperature (K) at (i, j-) coordinates C,
:1st radiation constant (3,7403X10'erg"c
m''/s) C3: Second radiation constant (1,4387 cm-') (7
), the wavelength λ8 of the (xtj) coordinate in equation (8). If we take the brightness ratio of λ2 and solve for the temperature T of the (i, j) coordinates, we get (9)
The formula becomes

However, the temperature at each coordinate point can be determined by performing the calculation shown in equation (9) for all coordinate points on a computer.

Using the temperature distribution obtained above, it is possible to perform the same process as in equation (1) above and obtain the flame temperature rise indicator using equation (6).

■t=f Tsuiyama 2d x (6)X T(x): Temperature integral value X of distance X from each burner end:
The distance from the burner end Ic above or Ib above is the combustion state evaluation index.

shall be.

Step 12o: Virtually change the amount of operation The amount of operation of the boiler is changed virtually using the computer 9.

Possible manipulated variables include air amount, fuel amount, fuel temperature, tertiary and secondary air register damper openings, secondary vane angle, gas recirculation amount, and two-stage combustion ratio.

Step 130: Evaluate the combustion state when the manipulated variable is changed. The combustion state of each stage burner flame when the manipulated variable is changed in step 120 above is estimated. The estimation method is shown in Figure 2.
From the figure, the manipulated variable at the time of evaluation in step 110 "evaluation of flame combustion state of each stage burner" is U. , calculate the combustion status evaluation index at that point. Assuming that the manipulated variable U and the combustion state evaluation index have a relationship as shown in FIG. 2, when the manipulated variable U decreases by ΔU from uo, the combustion state evaluation index becomes . The combustion state evaluation index when the manipulated variable is changed by increasing by ΔI from ΔI can be obtained from the above equation (2).

The reason why the amount of change ΔU and Δme are used in calculations as described above is that the combustion state of the burner flame changes due to factors that cannot be measured, such as the condition of the furnace, so the absolute value of the combustion state evaluation index Although it is difficult to estimate accurately, we have confirmed through various tests that even if the combustion state changes due to factors that cannot be measured, the change in the combustion state evaluation index in response to the change in the manipulated variable remains relatively the same. The combustion status evaluation index was actually evaluated using burner flame. This is because the combustion state evaluation index after the manipulated variable change can be estimated with high accuracy by the method that assumes the amount of change ΔI from .

By calculating the combustion status evaluation index from the flame image of each burner while changing each operation amount during trial operation, and confirming and understanding the relationship shown in Figure 2, it is possible to obtain the combustion status evaluation index from the flame image during plant operation. Based on the combustion condition evaluation index,
From the manipulated variable in that state, estimate the amount of change Δk in the combustion state evaluation index when the manipulated variable is changed by ΔU, use this change amount Δk to find the combustion state evaluation index after the manipulated variable change,
Furthermore, using this combustion state evaluation index, it is possible to estimate the unburned content in the ash after changing the manipulated variable.

Step 140: Estimating the unburned content in the ash based on the combustion state The unburned content in the ash at the furnace outlet is estimated using the combustion state evaluation index of the operation amount change report for each stage burner flame obtained above. A method for estimating unburned content in the ash of a boiler with an n-stage burner arrangement is shown below.

As mentioned above, the combustion state near the burner strongly influences the unburned content in the ash, but in order to quantitatively estimate the unburned content in the ash, it is also necessary to consider the combustion state in the trailing region of the flame. In addition, each stage burner has a different amount of fuel, coal properties, residence time of coal particles, etc., and each stage burner has a different influence rate on the unburned content in the ash at the furnace outlet, which is more than 0. In order to consider the influence rate on the unburned content in the ash at the furnace outlet, see (3) above.
The combustion state evaluation index of each burner stage is weighted as shown in the formula.

(4) above using weighted I, i'.

The unburned content in the ash is estimated using equation (5).

Step 15o: Determine whether the estimated unburned content in ash is lower than the target value or not, and if it is higher than the target value, further virtually change the manipulated variable. The processes of steps 120 to 150 are repeated until the target value is reached.

Step 16o: If the unburned content in the ash reaches the target value in the manipulated variable determination step 150,
The manipulated variable assumed at that time becomes the manipulated variable that causes the unburned content in the ash to reach the target value. In addition, considering the actual value of exhaust gas components such as NOx when implementing the operation amount, if denitrification cannot reduce the amount below the regulation value, a warning will be issued to the operator and the target value for unburned content in ash will be changed. There is a need.

The computer 9 processes steps 110 to 160,
The manipulated variable is determined, and the boiler control device 11 performs combustion control based on the manipulated variable.It also monitors whether the combustion state (combustion state evaluation index, unburned content in ash) changes as estimated when the manipulated variable changes, and checks the actual performance. In addition to correcting the data shown in FIG. 2 as data, if necessary, further step 11
If the processing from 0 to 160 can be repeated, the reliability will be further improved.

Furthermore, displaying flame images, colored images for each brightness or temperature level, etc. on the CRT will be more effective for operators to understand the combustion state.

In addition, instead of performing direct control, it is also possible to provide operational guidance to the operator by displaying the manipulated variable on a CRT, thereby allowing the operator to change the required manipulated variable.

In the above embodiment, each stage burner is provided with an image detection means, but in a boiler equipped with a plurality of burners,
If you understand the relationship between the combustion state evaluation index between each burner flame, you can detect at least one flame and evaluate the combustion state without necessarily always detecting images of all burners. For other flames, the combustion state evaluation index may be calculated based on the relationship with the detected image, and the unburned content in the ash may be calculated.

According to this embodiment, even when a plurality of types of coal are combusted, combustion can be performed to reduce unburned content in the ash without placing a burden on the operator.

〔Effect of the invention〕

According to the present invention according to claims 1 to 3 and 7, the combustion state is quantified from the image of the burner flame during combustion, and this numerical value is related to the operating amount of the boiler and the amount of unburned content in the ash. By taking advantage of this fact, the amount of boiler operation that minimizes the amount of unburned matter in the ash is searched for without manual intervention, so the amount of unburned matter in the ash can be reduced without relying on the operator's experience or intuition. This makes it possible to use fuel more effectively.

According to the present invention as set forth in claim 4, in a boiler equipped with a plurality of burners, it is possible to reduce unburned content in ash without providing an image detection means for all burners, and it is possible to reduce fuel economy at low cost. It has the effect of improving sex.

According to the present invention as set forth in claims 5 and 6, it is possible to prevent the NOx value from rising above the regulation value due to a decrease in unburned content in the ash, and to limit the NOx value to below the regulation value. It has the effect of reducing unburned content in the ash.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the boiler combustion control search device of the present invention, FIGS. 2 and 3 are conceptual diagrams explaining the present invention in detail, and FIG. 4 is an embodiment of the method of the present invention. FIG. 5 is a block diagram showing another embodiment of the boiler combustion control search device of the present invention, and FIG. 6 shows the configuration of the main circuits of the computer shown in FIG. 3. It is a block diagram. 2... Burner flame, 4... Image detection means (optical fiber bundle), 5... Image detection means (photoelectric conversion device), 7...
Image detection means (AD conversion device), 37... Change operation amount input means (change operation amount input circuit), 40... Combustion state evaluation index calculation means (combustion state evaluation index calculation circuit), 41
. . . changed combustion state evaluation index calculation means (changed combustion state evaluation index calculation circuit), 42 . . . unburned content in ash calculation means (unburned content in ash calculation circuit).

Claims (1)

[Scope of Claims] 1. From the relationship between the operating amount of the boiler, the combustion state evaluation index obtained from the brightness distribution of the burner flame generated by the operating amount, and the unburned content in the ash that occurs in response to the combustion state evaluation index. ,
By estimating the amount of change in the combustion state evaluation index with respect to the amount of change by virtually changing the operation amount, and estimating the amount of change in the unburned content in the ash based on the amount of change in the estimated combustion state evaluation index, A combustion control search method for a boiler that searches for a manipulated variable that causes unburned content to be less than or equal to a predetermined value. 2. From the relationship between the operating amount of the boiler, the combustion state evaluation index obtained from the temperature distribution of the burner flame generated by the operating amount, and the unburned content in the ash that occurs in response to the combustion state evaluation index,
By estimating the amount of change in the combustion state evaluation index with respect to the amount of change by virtually changing the operation amount, and estimating the amount of change in the unburned content in the ash based on the amount of change in the estimated combustion state evaluation index, A combustion control search method for a boiler that searches for a manipulated variable that causes unburned content to be less than or equal to a predetermined value. 3. The manipulated variables include the amount of air supplied to the boiler, the amount of fuel, the temperature of the fuel, the opening degree of an air register damper that adjusts the mixing state of the air and the fuel, and the vane angle;
3. The boiler combustion control search method according to claim 1, wherein the combustion control search method is any one or more of the boiler gas recirculation amount and the two-stage combustion ratio. 4. The boiler combustion control search method according to claim 1 or 2, wherein the burner flame is generated from at least one of a plurality of burners arranged in the boiler. 5. After calculating the operating amount of the boiler at which the unburned content in the ash is below a predetermined value, the NO_x value for the operating amount is below the regulation value from the operating amount and the actual NO_x value in the boiler exhaust gas. Claim 1 or 2 is characterized in that
The boiler combustion control search method described. 6. The combustion control search method for a boiler according to claim 5, further comprising changing the predetermined value of the unburned content in the ash if the NO_x value does not become less than a regulation value. 7. an image detection means for detecting an image of a burner flame of a boiler; a combustion state evaluation index calculation means for calculating a combustion state evaluation index of the burner flame from an image of the burner flame; a change operation amount input means for inputting a virtual amount of change in the amount of operation; and combustion of the burner flame after changing the amount of operation of the boiler based on the amount of virtual change in the amount of operation of the boiler and the combustion state evaluation index of the burner flame. A combustion control search device for a boiler, comprising: a changed combustion state evaluation index calculation means for calculating a state evaluation index; and an unburned content in ash calculation means for calculating unburned content in the ash of the boiler from the combustion state evaluation index.