JP2756815B2 - Boiler combustion control search method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for searching for an operation amount for boiler combustion control, and in particular, to reduce unburned ash in ash of a pulverized coal-fired boiler. The present invention relates to a boiler combustion control search method and apparatus suitable for searching for an operation amount to be operated.

[Conventional technology]

Conventionally, the only method for adjusting combustion is to adjust combustion so that CO can be balanced in the furnace during test operation. During operation, it is only controlled to keep the gas O ₂ at the furnace outlet constant.

As described in Japanese Patent Application Laid-Open No. 62-123218, there is a method for estimating the unburned matter in ash macroscopically.
Driving control for unburned ash was based on operator experience and intuition.

[Problems to be solved by the invention]

In the above prior art, the combustion in the boiler was adjusted based on the experience of the operator to adjust the combustion in the boiler so that NOx was equal to or less than the environmental regulation value and the unburned portion in the ash was minimized. In boilers for boilers, it is customary to use various types of overseas coal for the purpose of stabilizing the fuel supply source, which makes the combustion control of the operator complicated, and as described above, depends on the experience and intuition of the operator. It is also difficult to realize combustion that minimizes the unburned content of ash, since NOx is also below the regulation value.

An object of the present invention is to search for an operation amount of a boiler that makes unburned ash in ash equal to or less than a predetermined value and NOx value equal to or less than an environmental regulation value for any kind of coal to be handled.

[Means for solving the problem]

The above object is based on the relationship between the operation amount of the boiler, the combustion state evaluation index obtained from the luminance distribution of the burner flame generated by the operation amount, and the unburned ash 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 in which the amount is virtually changed, and estimating the amount of change in unburned ash in the ash from the estimated amount of change in the combustion state evaluation index, It is achieved by a combustion control search method of a boiler that searches for an operation amount at which the minute amount is equal to or less than a predetermined value, and an operation amount of the boiler, a combustion state evaluation index obtained by a temperature distribution of a burner flame generated by the operation amount,
From the relationship of unburned ash in the ash generated corresponding to the combustion state evaluation index, the amount of change of the combustion state evaluation index with respect to the amount of change obtained by virtually changing the manipulated variable is estimated. By estimating the change amount of the unburned ash in the ash from the change amount, it is achieved by the combustion control search method of the boiler that searches for an operation amount at which the unburned ash in the ash becomes a predetermined value or less.

The operation amount is an air amount supplied to the boiler, a fuel amount, a temperature of the fuel, an air register damper opening for adjusting a mixing state of the air and the fuel, a vane angle, and a boiler angle. It is appropriate to set the gas recirculation amount and the two-stage combustion ratio.

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

Further, after obtaining the operation amount of the boiler in which the unburned portion in the ash is equal to or less than a predetermined value, the NOx value for the operation amount is equal to or less than the regulation value based on the actual operation value of the operation amount and the NOx value in the exhaust gas of the boiler. Good to check. However, if the NOx value does not fall below the regulation value, it is necessary to change the predetermined value of the unburned ash in the ash.

Further, the above object is, as an apparatus, an image detecting means for detecting an image of a burner flame of a boiler, a combustion state evaluation index calculating means for calculating a combustion state evaluation index of the burner flame from the image of the burner flame, Change operation amount input means for inputting a virtual change amount of the operation amount of the boiler used for the burner flame, and operating the boiler based on the virtual change amount of the operation amount of the boiler and the combustion state evaluation index of the burner flame A post-change combustion state evaluation index calculating means for calculating a combustion state evaluation index of the burner flame after the amount change, and an unburned ash in burner calculating means for calculating the unburned ash content in the boiler from the combustion state evaluation index. This is achieved by using a boiler combustion control search device.

[Action]

In the combustion process of the pulverized coal particles, decomposition combustion of volatile components is performed at the beginning of the combustion, and thereafter, surface combustion of coke-like residual carbonaceous material (char) proceeds. Since the surface combustion of char is slower than the decomposition combustion of volatiles, most of the time required for pulverized coal to completely burn out can be considered as the time required for surface combustion of the char.

The decomposition and combustion of this volatile matter is very short in time, but the pulverized coal particles expand during this time (the char becomes porous,
Surface area increases), and this expansion governs the subsequent burning rate of the char and greatly affects the amount of unburned ash in the ash. As the expansion is performed quickly and the expansion amount is large, the effect on the surface combustion of the char is more favorable. Therefore, in order to reduce the unburned content in the ash, the expansion due to the decomposition and combustion of the volatile matter in the early stage of the combustion of the pulverized coal particles We need to promote the phenomenon. For this purpose, the molten ash generated by the surface combustion of the char covers the surface of the pulverized coal particles, and the volatile matter sufficiently erupts from the pulverized coal particles. If the flame temperature rises sharply near the burner outlet, the expansion of the pulverized coal particles is promoted, and the unburned ash in the ash is reduced.

The present invention, the amount of unburned ash in pulverized coal combustion, the degree of temperature rise after pulverized coal particle ignition as described above,
In other words, it is made by paying attention to the fact that the burner flame strongly depends on the temperature distribution (luminance distribution may be used) in the flame ejection direction. Further, the temperature distribution of the burner flame is supplied to the flame. Combustion air amount, fuel amount, temperature of the fuel,
It is made by paying attention to the fact that it depends on a boiler operation amount such as an air register damper opening degree, a vane angle, a combustion gas recirculation amount and a two-stage combustion ratio for adjusting a mixing state of the air and the fuel. .

A method of obtaining a combustion state evaluation index indicating a brightness distribution of a burner flame depending on the operation amount of the boiler in the boiler combustion control search method will be described with reference to FIG.

FIG. 3 shows the image of the burner flame obtained by the image detecting means, the distance x from the tip of the burner 16 on the x-axis, the width of the burner flame image on the y-axis, and the brightness L of the burner flame in the height direction, that is, the z-axis. Is represented in three dimensions. Where burner
16 A luminance integrated value S (x) in the y-axis direction of the luminance at a distance x from the tip is obtained. For example, when x = a, the luminance integrated value is indicated by S (a), and when x = b, x = c, S (b), S
This is shown in FIG. Using the integrated brightness value S (x), the brightness rise index I _b (combustion state evaluation index obtained from the brightness distribution of the burner flame) is calculated by the following equation (1) to evaluate the brightness rise of the burner flame.

According to the formula (1), since the luminance closer to the burner tip is weighted and integrated, the brightness rise index of the burner flame is sharper (the higher the brightness of the flame near the burner tip is, the higher the brightness rise index Ib _). Becomes larger.

Next, the operation amount of the boiler (the amount of air to be supplied, the amount of fuel, the temperature of the fuel, the opening degree of the air register damper for adjusting the mixing state of the air and the fuel, the vane angle, the gas recirculation amount of the boiler, and the two-stage combustion) The method of estimating the amount of change in the combustion state evaluation index when the ratio is changed will be described with reference to FIG.
In FIG. 2, the horizontal axis represents the operation amount u of the boiler, and the vertical axis represents the combustion state evaluation index I, and the relationship between the operation amount of the boiler and the combustion state evaluation index is represented by a smooth curve. The operation amount at the time of obtaining the image of the burner flame is u ₀ ,
Assuming that the combustion state evaluation index indicating the rising of the brightness of the flame at that time is I ₀ ( _Ib ), if the operation amount is changed by Δu, the combustion state evaluation index I changes by ΔI, and the combustion after the operation amount is changed. condition evaluation index I ₁ is determined by the following equation (2).

I ₁ = I ₀ + ΔI (2) A method for estimating unburned ash in ash at the furnace outlet of a boiler having an n-stage burner arrangement using the combustion state evaluation index obtained after changing the manipulated variable obtained above.

The combustion state of each stage burner differs depending on the combustion state in the downstream area of the flame, the coal properties, the residence time of coal particles, etc., and the unburned ash in the ash generated is affected by these factors. For this purpose, the following weighting is applied to the combustion state evaluation index of each stage burner.

I ₁ i ′: Burning condition evaluation index for each stage burner after weighting I ₁ i: Burning condition evaluation index for each stage burner before weighting K: Coefficient determined by coal properties fi: Fuel amount of i-stage burner f: Total input fuel amount Using the weighted I ₁ i ′, the unburned ash in the ash is estimated by the equations (4) and (5).

(100−c) = g ₁ · I ₁₁ ′ + g ₂ · I ₁₂ ′ +... G _n · I _1n ′ (4) gi (i = 1 to n): Coefficient determined by the oxygen concentration in the furnace, etc. c: Coal unburned rate (%) A: Coal ash (%) U: Unburned content in ash (%) Above, the brightness rise of burner flame as an index I _b the combustion state evaluation index I, although the method for estimating the ash unburned, a luminance rising index I _b of the burner flame, replacing the temperature rise indicator I _t of the burner flame, exactly as above A similar process can be used to estimate unburned boiler ash. In that case, taking the temperature to the Z axis in FIG. 3, the temperature rise indicator I _t may be determined by the following equation (6).

As described above, the combustion state evaluation index is obtained based on the image of the burning flame, and if the unburned portion in the ash is estimated based on the combustion state evaluation index, the current boiler operation amount is virtually Δu The change amount (ΔI) of the combustion state evaluation index I accompanying the change of Δu is calculated based on the relationship between the manipulated variable and the combustion state evaluation index as shown in FIG. By then (2), the combustion state evaluation index I ₁ after the boiler operation amount change, is calculated, after the weighting is performed according to (3) in the combustion state evaluation index I _1, the equation (4) The unburned ash in the ash after the change in the boiler operation amount is estimated. This operation is repeated to search for a necessary boiler operation amount in order to reduce the unburned portion in the ash to a target value or less.

In the method according to claim 5, further, when a boiler operation amount that makes the unburned ash in the ash equal to or less than the target value is obtained, the NOx generation amount corresponding to the obtained boiler operation amount is different from 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 equal to or less than the regulation value.

In the method according to claim 6, when the NOx value calculated based on the manipulated variable for setting the unburned ash content in the ash to be equal to or less than the target value, regardless of the target value of the unburned ash content in the ash, , Based on the actual value indicating the relationship between the manipulated variable and the NOx value,
The value of the operation amount that is virtually changed in the direction in which the value decreases and the NOx value becomes a value below the regulation value is output as the final operation amount.

According to the combustion control search device of claim 7, first,
The burner flame is imaged by the image detection means. Based on the luminance distribution or the temperature distribution of the flame image, a combustion state evaluation index of the flame is obtained by the evaluation instruction calculation means, and based on the obtained combustion state evaluation index, the unburned ash in the ash is converted into the ash. It is determined by the unburned portion calculating means. Further, a virtual change amount for virtually changing the operation amount with respect to the boiler operation amount at the time when the burner flame is imaged is input by the change operation amount input means, and the virtual change amount and the combustion From the state evaluation index, a combustion state evaluation index after a change in the operation amount is calculated and obtained by the post-change fuel state evaluation index calculation means based on a relationship between the operation amount and the combustion state evaluation index which are obtained in advance. Next, the changed unburned ash content is calculated by the ash unburned content calculating means based on the combustion state evaluation index after the manipulated variable change.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of a boiler combustion control device according to an embodiment of the present invention, and FIG. 4 is a flowchart showing an embodiment of a combustion control search method. Furnace 1
The image of the burner flame 2 ejected from the burner installed in the (boiler) is transmitted to the photoelectric conversion device 5 through the optical fiber bundle 4 cooled by the cooling pipe 3 (the objective part can be purged as a measure to prevent soot adhesion). Transmitted and converted there into electrical signals. The electric signal is transmitted to an analog / digital converter (hereinafter, referred to as an AD converter) 7 via a signal cable 6, converted into digital data, and stored in an image memory 8. The optical fiber bundle 4, the photoelectric conversion device 5, and the AD conversion device 7 constitute an image detecting means. The image data stored in the image memory 8 is processed by the computer 9, and the CRT 10 connected to the computer 9 minimizes the data input to the computer 9 and unburned ash in the ash, and keeps the NOx value below the regulation value. The manipulated variable to be performed, the measured value of unburned ash in ash, the NOx regulation value, and the like are displayed. Perform the operation as follows.

The computer 9 has the following circuit as shown in FIG. That is, the burner flame image input circuit 36 is connected to the image memory 8 and receives the burner flame image of each stage. The burner flame image input circuit 36 is connected to the burner flame image input circuit 36, and the combustion state evaluation index is calculated based on the burner flame image. A combustion state evaluation index calculation circuit 40 which is a combustion state evaluation index calculation means for calculating and outputting,
A post-change combustion state evaluation index operation circuit 41 as a post-change combustion state evaluation index operation means connected to the combustion state evaluation index operation circuit and a change operation amount input circuit 37 as a change operation amount input means; The unburned ash in the ash calculation circuit 42, which is a means for calculating unburned ash in the ash, connected to the combustion state evaluation index calculation circuit 41 and the coal property input circuit 38; the unburned ash in the ash calculation circuit 42; The unburned ash in-ash comparison circuit 43 connected to the fuel target value input circuit 39, the manipulated variable changed NOx actual value input circuit 48 connected to the changed manipulated variable input circuit 37, and the manipulated variable changed NOx NOx connected to the actual value input circuit 48 and the NOx regulation value input circuit 45
The regulated value comparison circuit 44, the unburned ash in the ash comparison circuit 43 and NOx
An unburned ash / NOx value determination circuit 49 connected to the regulation value comparison circuit 44, an alarm output circuit 46 connected to the NOx regulation value comparison circuit 44, and the ash unburned content / NOx value decision circuit 49 is provided with an optimum manipulated variable output circuit 47 connected to 49.

Combustion state evaluation index computing circuit based on the inputted flame image data, the luminance rising index burner flame I _b or, determine the temperature rising index I _t, calculated indicator I _b,
Or I _t as a combustion state evaluation index, and outputs the changed after combustion state evaluation index calculating circuit 41.

The change manipulated variable input circuit 37 receives a virtual manipulated variable change with respect to the boiler manipulated variable in the state where the burner flame image is detected (the boiler manipulated variable is hereinafter referred to as the manipulated variable). After changing the combustion state evaluation index calculation circuit 41,
Output to the optimal manipulated variable output circuit 47 and the manipulated variable changed NOx actual value input circuit 48.

The changed combustion state evaluation index calculation circuit 41 receives the combustion state evaluation index and the change amount of the operation amount, and changes the combustion state after the change in the operation amount changed by the change amount input from the operation amount at the time of burner flame image detection. The evaluation index is calculated and output to the unburned ash content calculation circuit.

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

The unburned ash calculation circuit 42 receives the post-change combustion state evaluation index (or the combustion state evaluation index) and the properties of the burning coal type (for example, the coefficient K and the ash%), and receives the combustion state evaluation index. Calculate unburned ash in ash by weighting,
Output to the unburned ash in-ash comparison circuit 43.

The ash unburned portion comparison circuit 43 is a ash unburned portion target value input circuit.
By comparing the target value of unburned ash in ash input through 39 with the value of unburned ash in ash input from the unburned ash in arithmetic circuit, a signal indicating whether or not the target value is equal to or less than the target value is obtained. Fuel / NOx value judgment circuit 4
Output to 9.

The manipulated variable changed NOx actual product value input circuit 48 receives the manipulated variable at the time of burner flame image detection and the manipulated variable change amount,
NOx value based on the past performance corresponding to the manipulated variable after change
Output to the Ox regulation value comparison circuit 44.

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

The unburned ash in NO / NOx value determination circuit 49 receives a signal indicating whether the unburned ash in 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. When the minute is smaller than the target value and the NOx value is smaller than the regulation value, an operation amount output signal is output to the optimum operation amount output circuit 47.

The alarm output circuit 46 issues an alarm when a signal indicating that the NOx value is larger than the regulation value is input. (Voice, light, etc.) When the operation amount output signal is input, the optimum operation amount output circuit 47 outputs the change amount of the operation amount input from the change operation amount input circuit 37 to the CRT 10 and the boiler control device 11.

Next, a method of searching for the operation amount of the boiler to make the unburned ash in the ash reach the target value will be described with reference to the steps of the flowchart shown in FIG.

Step 100: Setting the target value of unburned ash in ash, etc. (1) The target value of unburned ash in ash is set to, for example, 5% or less. This is because the ash left after burning coal is available as an admixture for concrete, but to use it as an admixture,
This is because it is necessary to reduce the unburned content in the ash to approximately 5% or less.

(2) Set a past actual value of unburned ash in ash for different boiler operation amounts depending on the type of coal to be handled (coal blend ratio), boiler load, and the like. In addition, when disturbance occurs due to a change in coal type, a change in load, or the like, resetting is necessary. In addition, the relationship between various coefficients and the boiler operation amount that differ depending on the coal properties and the actual value of NOx in the exhaust gas is set.

(3) Set the NOx regulation value.

Step 110: Evaluation of Burner Flame Combustion State for Each Stage Burner flame image data obtained by the boiler combustion control search device described in FIG. 1 is processed by the computer 9 by the method shown in FIG. Is evaluated based on the rise in luminance. At the time of this evaluation, it is effective to perform noise removal or the like as preprocessing. It is desirable that the image data be data obtained by averaging several detection results.

FIG. 3 is a diagram showing the flame image three-dimensionally, in which the luminance L of the flame image is set on the z-axis, the distance x from the burner tip is set on the x-axis, and the burner flame image width distance is set on the y-axis. . The integrated value of the brightness of the burner flame in the y-axis direction at a distance x from the tip of the burner is S (x). For example, the integrated value of the brightness of the burner flame at x = a, x = b, x = c is S ( a)
(20 in the figure) S (b) (21 in the figure) and S (c) 22 in the figure.

The luminance rise index I _b of the burner flame obtained by the following equation (1) was evaluated rising luminance.

x: Distance from burner end a: Value as close as possible to burner end.

According to the equation (1), since the luminance value becomes closer to the burner end, the integrated value becomes more weighted. Therefore, the luminance rise index _Ib increases as the luminance rises sharply.

It is also possible to use the temperature distribution of the burner flame instead of the above-mentioned luminance rise index to evaluate the combustion state by the flame temperature rise. FIG. 5 shows an embodiment of the device configuration for obtaining the flame temperature distribution. Each stage burner flame 2 is captured as an image through the optical fiber bundle 4 cooled by the cooling pipe 3, is divided into the wavelengths λ ₁ and λ ₂ by the spectroscope 23, is photoelectrically converted by the photoelectric conversion device 5, and is analogized. /
The digital signal is converted by the digital converter 7 into a digital signal. The flame images of the respective wavelengths λ ₁ and λ ₂ converted into digital signals are stored in the image memory 8. The flame images of the respective wavelengths λ ₁ and λ ₂ are subjected to the following processing by the computer 9 to determine the temperature distribution of the burner flame.

According to Wien's equation, the relationship between the luminance and the temperature at each coordinate point of the wavelengths λ ₁ and λ ₂ is expressed by equations (7) and (8).

Here, R ₁ (i, j): the luminance of the wavelength λ _{1 in} the (i, j) coordinate R ₂ (i, j): the luminance of the wavelength λ _{2 in} the (i, j) coordinate ε ₁ : the effective wavelength λ ₁ emissivity epsilon _2: effective emissivity lambda ₁ of the wavelength lambda _2: wavelength lambda _2: wavelength T (i, j) :( i , j) absolute coordinates (K) C _1: first radiation constant (3,7403 × 10 ⁵ erg · cm ² / s) C ₂ : Second radiation constant (1,4387 cm · K ゜) Luminance ratio of wavelengths λ ₁ and λ ₂ at (i, j) coordinates in equations (7) and (8) And solving at the temperature T at the (i, j) coordinate yields equation (9).

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

Performs the same processing as by at obtained above by temperature distribution (1) above, it is possible to obtain a flame temperature rising index I _t in equation (6).

T (x): the distance the I _t or preceding I _b the combustion state evaluation index I _0, from the burner end: distance temperature integral value x of x from each burner end.

Step 120: Virtually change the operation amount The computer 9 virtually changes the operation amount of the boiler. Examples of the manipulated variables include an air volume, a fuel volume, a fuel temperature, tertiary and secondary air register damper opening degrees, a secondary vane angle, a gas recirculation amount, and a two-stage combustion ratio.

Step 130: Evaluation of combustion state at the time of change of operation amount The combustion state of each stage burner flame when the operation amount is changed at step 120 is estimated. FIG. 2 shows the estimation method. Referring to FIG. 2, the operation amount at the time of the evaluation in step 110 “Evaluation of burner flame combustion state of each stage” is u ₀ , and the combustion state evaluation index at that time is I ₀ . Here, assuming that the manipulated variable u and the combustion state evaluation index I have a relationship as shown in FIG.
When the manipulated variable u is decreased by Δu from u ₀ , the combustion state evaluation index I increases by ΔI from I _0, and the combustion state evaluation index I ₁ when the operation amount is changed can be obtained by the above equation (2). it can.

As described above, the change amounts Δu and ΔI are used in the calculation because the combustion state of the burner flame also changes depending on factors such as the state of the furnace, which cannot be measured, so that the absolute value of the combustion state evaluation index I can be accurately determined. Although it is difficult to estimate, even if the combustion state changes due to a state measurement impossible factor, it has been confirmed by various tests that the change of the combustion state evaluation index I relative to the operation amount change does not relatively change. This is because the actual combustion state evaluation index I ₁ after the operation amount changing by assumed method the variation ΔI from combustion state evaluation index I ₀ as assessed by the burner flame can be accurately estimated.

By calculating the combustion state evaluation index from the flame image of each burner while changing each manipulated variable at the time of test operation, and confirming and grasping the relationship shown in FIG. 2, it is possible to obtain from the flame image during plant operation. Using the combustion state evaluation index as a reference, the change amount ΔI of the combustion state evaluation index when the operation amount is changed by Δu is estimated from the operation amount in that state, and the combustion after the operation amount is changed using this change amount ΔI. The state evaluation index is obtained, and further, the unburned ash in the ash after the operation amount change can be estimated using the combustion state evaluation index.

Step 140: Estimate the ash in unburned furnace exit with the combustion state evaluation index I ₁ of the later operation amount changing in each stage burner flame obtained in the ash unburned estimated above by the combustion state. A method for estimating unburned ash in ash of a boiler having an n-stage burner arrangement will be described below.

As mentioned above, the combustion state near the burner strongly affects the unburned ash content, but to quantitatively estimate the unburned ash content,
It is also necessary to consider the combustion state in the downstream area of the flame. Also,
In each stage burner, the fuel amount, coal properties, residence time of coal particles, etc. are different, and the influence rate on the unburned matter in the ash at the furnace outlet differs for each stage burner. From the above, the combustion state evaluation index of each stage burner is weighted as shown in the above equation (3) in order to consider the influence rate of each stage burner on the unburned matter in the furnace exit ash.

Using the weighted I ₁ i ′, the above (4), (5)
Estimate the unburned ash content using the equation.

Step 150: Determine whether or not the unburned ash in the ash estimated below the target value of the unburned ash in the ash is lower than the target value.If the unburned ash in the ash is larger than the target value, the manipulated variable is further virtually changed. The processing of steps 120 to 150 is repeated until the target value is reached.

Step 160: manipulated variable determination If the unburned ash in the ash reaches the target value in step 150,
The manipulated variable imagined at that time is the manipulated variable that causes the unburned ash in the ash to reach the target value. In addition, when the operation amount is executed,
Considering the actual values of exhaust gas components such as NOx, if it cannot be controlled below the regulation value by denitration, it is necessary to issue an alarm to the operator and change the target value of unburned ash in ash.

The computer 9 performs the processing of steps 110 to 160 as described above, and the manipulated variable is determined, whereby the boiler control device 11 performs combustion control. Also, it monitors whether the combustion state (combustion state evaluation index, unburned ash content) changes as estimated at the time of the operation amount change, corrects the data shown in FIG. 2 as the actual data, and, if necessary, By repeating the processing of steps 110 to 160, the reliability is further improved. Also, CRT
If an image of the flame, an image colored for each luminance or temperature level, or the like is displayed, it is more effective for the operator to understand the combustion state.

In addition, instead of performing direct control, for example, an operation amount is displayed on a CRT to provide operation guidance to an operator, and thereby the operator can change a necessary operation amount.

In the above embodiment, the image detecting means is provided in each stage burner. However, in a boiler having a plurality of burners, if the relationship between the combustion state evaluation indices between the burner flames is grasped, it is not always all necessary. Even if no burner image is detected, at least one of the flames is detected, the combustion state is evaluated, and the combustion state evaluation index is calculated for the other flames in relation to the detected image. Alternatively, the unburned ash content may be calculated.

According to the present embodiment, even when a plurality of types of coal are burned, it is possible to perform combustion that reduces unburned ash in the ash without imposing a burden on the operator.

〔The invention's effect〕

According to the present invention, the combustion state is quantified from the image of the burner flame during combustion, and this numerical value is related to the operation amount of the boiler and the amount of unburned ash in the ash. By using this, the amount of unburned ash in the ash can be searched without the need for manual operation of the boiler to minimize the amount of unburned ash in the ash, so the amount of unburned ash in the ash can be reduced without relying on the operator's experience and intuition It is possible to effectively use fuel.

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

According to the fifth and sixth aspects of the present invention, it is possible to prevent the NOx value from rising above the regulation value as the unburned ash in the ash decreases, and to limit the NOx value to the regulation value or less. While reducing unburned ash in the ash.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a boiler combustion control search device according to the present invention, FIGS. 2 and 3 are conceptual diagrams illustrating the principle of the present invention, and FIG. 4 is an embodiment of a method according to the present invention. FIG. 5 is a block diagram showing another embodiment of the boiler combustion control search device according to the present invention, and FIG. 6 shows a configuration of a main circuit of the computer shown in FIG. It is a block diagram. 2 ... burner flame, 4 ... image detecting 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... Post-change combustion state evaluation index calculation means (post-change combustion state evaluation index calculation circuit), 42... Ash unburned portion calculation means (ash unburned portion calculation circuit).

Continued on the front page (72) Inventor Hisanori Miyagaki 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Inside the Omika Plant of Hitachi, Ltd. (72) Inventor Makoto Shimoda 4026 Kujimachi, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi, Ltd. Inside the laboratory (72) Inventor Yoshio Watanabe 1-73-3, Kashiwagi, Sendai-shi, Miyagi (72) Inventor Kazuhiro Ishiyama 4-7-16, Miyamachi, Sendai-shi, Miyagi (56) References JP-A-61-180829 (JP, A) JP-A-62-84222 (JP, A) JP-A-62-237221 (JP, A)

Claims (3)

(57) [Claims] An operation amount of a boiler, a combustion state evaluation index obtained by quantifying a luminance distribution or a temperature distribution in a burner ejection direction of a burner flame generated by the operation amount, and a combustion state evaluation index. From the relationship of the unburned ash content, the change amount of the combustion state evaluation index with respect to the change amount obtained by virtually changing the operation amount is estimated, and the change amount of the unburned ash content in the ash is estimated based on the estimated change amount of the combustion state evaluation index. In the boiler combustion control search method for searching for an operation amount at which the unburned ash content is equal to or less than a predetermined value by estimating the amount, the operation amount includes an air amount supplied to the boiler, a fuel amount, and the fuel amount. Temperature, an air register damper opening for adjusting the mixing state of the air and the fuel, a vane angle, a gas recirculation amount of the boiler, and a two-stage combustion ratio. And the said Among unburned of the operation amount and the boiler in the exhaust gas after obtaining an operation amount of the boiler equal to or less than a predetermined value
A boiler combustion control search method characterized by confirming from a NOx value actual value whether a NOx value corresponding to the manipulated variable is equal to or less than a regulation value. 2. When the NOx value does not fall below a regulation value,
The method according to claim 1, wherein a predetermined value of the unburned portion in the ash is changed. 3. An image detecting means for detecting an image of a burner flame of a boiler, a combustion state evaluation index calculating means for calculating a combustion state evaluation index of the burner flame from the image of the burner flame, and detecting the burner flame image. Change operation amount input means for inputting a virtual change amount of the operation amount with respect to the operation amount of the boiler, and changing the operation amount of the boiler based on the virtual change amount of the operation amount of the boiler and the combustion state evaluation index of the burner flame. The post-change combustion state evaluation index calculating means for calculating the combustion state evaluation index of the subsequent burner flame and the output of the post-change combustion state evaluation index calculation means as inputs, and calculate the unburned ash in the ash of the boiler after the manipulated variable change. Ash unburned portion calculating means, ash unburned portion comparing means for determining whether or not the output of the ash unburned portion calculating device is higher or lower than the ash unburned portion target value, and outputting the boiler operation amount Actual NOx value in boiler exhaust gas NOx regulation value comparison means for judging whether the NOx value corresponding to the virtual manipulation quantity is larger or smaller than the regulation value from the relationship between the values and the virtual manipulation quantity of the boiler which is the basis of the post-change combustion state evaluation index. , A boiler combustion control search device comprising: