JPH01312319A - Boiler combustion state monitoring device - Google Patents

Abstract

PURPOSE:To make it possible to estimate stabilized and steady unburnt substances contained in ash and monitor combustion flames with accuracy and satisfactory result by evaluating combustion volume of flames, time changes in luminance or temperature or luminance or temperature rise from a burner. CONSTITUTION:Flames 2 during the operation of a boiler are measured by an image fiber 5 so as to obtain the image of each flame luminance through respective filters 8 and 9 by way of a spectroscope 6. This image is photographed with a photoelectric converter 10. The respective wavelength analog signals 17 and 18 are converted into digital image data respectively with an analog/digital converter 11 and stored in an image storage device 12. Then, an attempt is made to obtain a deviation from the average luminance of each image. The average luminance distribution is then obtained from each image. The temperature distribution is further obtained so that the rise in the temperature from a burner may be evaluated. Furthermore, the combustion volume is evaluated. Based on the evaluation, the unburnt substances in the ash can be calculated and displayed on a display device, which makes it possible to monitor the combustion state properly and accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a monitoring device for the combustion state of a boiler, and particularly to a monitoring device suitable for estimating unburned content in ash.

[Conventional technology]

Conventional devices measure the flame shape near the burner as a brightness distribution, as described in Japanese Patent Application Laid-Open No. 60-228818,
The device extracted the shape of the oxidizing flame from the measured flame image and estimated the unburned content in the ash based on information about the position between the burner and the extracted oxidizing flame. However, no consideration was given to the combustion volume of the flame, temporal changes in brightness or temperature, and the rise in brightness or temperature from the burner, etc., which strongly affect the unburned content in the ash. Another problem is that it cannot be applied to flames other than those in which oxidized carbon exists one by one on each side of the burner shaft.

[Problem to be solved by the invention #]

When estimating the unburned content in the ash, the above conventional technology evaluates the ignitability of the flame and the size of the flame high temperature region using information regarding the position between the burner and the extracted oxidation flame, and estimates the unburned content in the ash. However, it does not take into account the combustion volume of the flame, temporal changes in brightness or temperature, and the rise in brightness or temperature from the burner, etc., which strongly affect the unburned content in the ash. Coal type, burner, combustion furnace,
There was a problem that the estimation method could not follow differences in operating conditions.

The purpose of the present invention is to evaluate temporal changes in flame combustion volume, brightness or temperature, and rise in brightness or temperature from a burner, and to be able to track differences in coal types, burners, combustion furnaces, and operating conditions.

The objective is to perform stable and reliable estimation of unburned content in ash and to monitor combustion flames well and accurately.

[Means for solving problems]

The problem described above is to analyze the combustion flame of the burner in two spectroscopic spectra.
- a spectrometer that separates light into two spectra, a filter that filters the two spectra into monochromatic light of different wavelengths, a photoelectric conversion device that converts the monochromatic light into an electrical signal, and a photoelectric conversion device that converts the electrical signal into a digital value. an analog-to-digital converter,
A boiler combustion state comprising a digital image storage device that stores the digital value as an image, a computer that calculates the combustion state of the boiler from the digital storage value of the digital image storage device, and a display device that displays the combustion state. In the monitoring device, the computer calculates, as the combustion state of the boiler, a first feature quantity in which the brightness or temperature at each position of the combustion flame shape of the burner is weighted by the distance between a predetermined position and each position, and a first feature quantity of the combustion flame shape. A second feature value in which the area is weighted by the brightness or temperature at each position of the combustion flame shape, the brightness or temperature at each position of the combustion flame shape, and at least one temporal change in the combustion flame shape. This problem is solved by a boiler combustion state monitoring device that calculates the unburned content in the ash from the third characteristic amount.

[Effect]

The combustion flame of the burner is split into two spectra by a spectrometer, passed through a filter into monochromatic light of different wavelengths, converted into an electrical signal by a photoelectric conversion device, converted into a digital value by an analog-to-digital conversion device, and converted into a digital image. A first feature quantity stored in a storage device, and using this stored data, a computer calculates the brightness or temperature at each position of the combustion flame shape of the burner, and weights this by the distance between the predetermined position and each position. , a second characteristic value in which the area of the combustion flame shape is weighted by the brightness or temperature at each position, and a second characteristic value representing the brightness or temperature at each position of the combustion flame shape, and at least one temporal change in the combustion flame shape. The unburned content in the ash is calculated from the three feature values using an estimation formula, and is displayed on a display device for monitoring.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. In FIG. 1, 1 is a burner, 2 is a flame, 3 is a boiler, 4 is a cooling device, 5 is an image fiber, 6 is a spectrometer, 7 is a half mirror, 18 is a filter (transmits wavelength λ1),
9 is a filter (transmits wavelength λ2), 10 is a photoelectric conversion device,
11 is an analog/digital converter, and 12 is a digital image storage device.

13 is a calculator, 14 is a display device, 15 is an analog/digital conversion timing signal, 16 is each burner fuel supply amount,
Air supply amount (including secondary and tertiary air distribution, etc.), air supply method (secondary and tertiary register, vane opening, etc.) signal control, 1
7 is a wavelength λ1 analog signal, and 18 is a wavelength λ2 analog signal.

Hereinafter, an embodiment will be described according to the process flow shown in FIG.

1) 100: Image input The flame 2 during boiler operation is measured using an image fiber 5, as shown in FIG. Filter (wavelength λ2 transmission) 9
Pass through. For example, λ1=600nm, λZ=700n
When m, flame brightness images at wavelengths of 600 nm and 700 nm are obtained.

The image is captured by the photoelectric conversion device 10, and the respective wavelength analog signals 17 and 18 are transferred to the analog/digital conversion device @11.
Each image is converted into digital image data and stored in the digital image storage device 12. Note that the digital image storage device 1
The analog/digital conversion execution timing signal 15 is used to determine the timing for analog/digital conversion of the video signal to be input to the analog/digital conversion. In this example, analog/
Although the timing signal 15 for digital conversion execution is given from the computer 13, the effect remains the same even if it is given manually. The above process is repeated a set number n times at a set cycle. Note that if the following processing is to be performed using only the luminance image, it is also possible to pass only the filter through the filter without using the spectroscope 6, and to process only the luminance image of one arbitrary wavelength.

The following processing is performed by the computer 13.

2) 110: Find the deviation from the average luminance structure of each image.

Obtain n digital images for two wavelengths, and extract only the flame by processing each sampled flame brightness image of any wavelength to zero the brightness level below a certain flame brightness image. do.

The average brightness of the wavelength is determined from the average brightness of each sampled flame brightness image after the processing, and the standard deviation is determined from the average brightness of each sampled flame brightness image, as shown in equation (1).

However, σR: standard deviation n: set sampling number γI: average brightness of each sampled image R: the average brightness of the set wavelength calculated from γ1 The standard deviation calculated represents the temporal change in flame brightness, Let the reciprocal number be the flame stability X(=-)σ R . Note that the effect remains the same no matter which of the two wavelengths the standard deviation is used for. Furthermore, even if the temperature is determined from the flame brightness image sampled at each wavelength and then the standard deviation is determined, the effect remains the same.

Further, when calculating the standard deviation, processing may be performed using flame information of an arbitrary region.

3) 120: Find the average brightness distribution from each image.

Using the brightness distribution of each sampled flame image for each wavelength, the average brightness distribution for each wavelength is determined as shown in equation (2).

R7oo(i + j) = □ ... (2) Reoo(ir j) = □ However, R7oo(it j): Average brightness of the (11j) coordinate of the image with a wavelength of 700 nm, Reoo(it, j): Average brightness of the (IIJ) coordinate of the image with a wavelength of 600 nm γ7ooh (it j): The brightness of the (i, j) coordinate of the image sampled at the second time with a wavelength of 700 nm γ700k (1 + j): The brightness of the second sampled image with a wavelength of 600 nm Brightness of the (i, j) coordinates of the image 4) 130: Find the temperature distribution.

The temperature distribution is calculated using the average brightness distribution of each wavelength described above. The method for calculating the temperature at each coordinate point of the flame digital image is shown below.

Using Wien's equation, the wavelength λ1. The relationship between the brightness and temperature of each coordinate point of λ2 is expressed by equation (3>, (4)).

However, R1 (11J): Wavelength 7 of (11j) coordinate
00nm brightness R2 (11J): (11J) coordinate wavelength 600nm
Luminance εl: Effective emissivity at wavelength 700 nm ε2: Effective emissivity at wavelength 600 nm λ1: Wavelength 700 nm λ2: Wavelength 600 nm T (i, j): Absolute temperature at (i, j) coordinates (°K
)C! :1st radiation constant (37403X 105erg
+i/s) C2: Second radiation constant (14381cm・0K) (3)
, the wavelength of the (i, j) coordinates in equation (4) is 700 nm, 600
If we take the brightness ratio in nm and solve it using the temperature T of the (i, j) coordinates, we get equation (5).

ε to ε2 By performing the calculation shown in equation (5) on a computer for all coordinate points, the temperature of each coordinate point can be determined. In the above, we used the luminance distribution of two wavelengths measured from the flame.
Although the method for determining the flame temperature distribution applying the color pyrometer method has been described, the temperature distribution can also be determined from the luminance distribution of one wavelength from the flame. The method is shown below.

The relationship between flame wavelength, brightness (radiant intensity), and temperature is (4)
It can be expressed by the blank equation shown in Eq.

However, λ: Wavelength (μm) T: Absolute temperature (0K) R: Luminance at the wavelength C1: First radiation constant (37403x i Oo-5er
°C1+? /S) C2: Second radiation constant (14337cm ・0K) (6)
By applying the formula and applying formula (7) to all points in the flame brightness image, the flame temperature distribution can be found.

However, T (L j): Absolute temperature at the (it j) coordinate R (i, j): Greater than or equal to the brightness at the (i, j) coordinate, (6)
In order to realize the formula, the spectroscope shown in FIG. 1 is not necessary, and it is sufficient to have a luminance image of any one wavelength passed through a filter.

5) 140: Evaluation of temperature rise from burner This will be explained below using FIG. As shown in FIG. 3(a), considering a flame, the average temperature at each point on the burner shaft is determined using equation (7).

□ ΣTxt Tx+=□ ...(7) However,
〒Ma,: Burner axis X + average temperature M: Burner axis x
Number of coordinate points in 1 section T x I: Burner axis , the average temperature of each section on the burner axis was determined.

If these average temperatures are plotted with the burner axis distance on the horizontal axis and the average temperature on the vertical axis, the result will be as shown in FIG. 3(b), and a temperature rise curve of the flame from the burner will be determined. A method for quantitatively evaluating the flame temperature rise will be described below.

In the combustion process of pulverized coal particles, volatile matter is decomposed and burned in the initial stage of combustion, and then coke-like residual carbon (char) is burned on the surface. Since the surface combustion of char is slower than the decomposition combustion of volatile matter, most of the time required for the pulverized coal to completely burn out is considered to be related to the surface combustion of char.

This decomposition and combustion of volatile matter is instantaneous, but during this time the pulverized coal particles are accompanied by an expansion phenomenon that later controls the burning rate of char, and this has a great effect on the unburned content in the ash. In this way, in order to reduce the unburned content in the ash, it is necessary to promote the expansion phenomenon due to extraction of volatile matter from pulverized coal particles.

To this end, it is necessary to raise the temperature rapidly after ignition in order to prevent the volatile matter from being trapped in the molten ash before it is fully ejected from the pulverized coal particles and combusted. From this, we believe that if the flame temperature rises rapidly from the burner outlet, the unburned content in the ash will be reduced, and the rise in flame temperature from the burner is also weighted by the distance from the burner. 8
) The evaluation method shown in the formula was used.

However, G: Flame temperature rise characteristic〒] 7: Average temperature of burner axis xL section xI: Position of Xt section on burner axis xa: Burner exit position xl,: Position determined by burner size, etc. Note that brightness is used It is also possible to perform the above evaluation.

6) 150: Combustion volume evaluation This will be explained below using FIG. Consider a flame as shown in Figure 4(a). For example, the sum of the temperatures at each point in the X1 zone 21 on the burner axis is expressed as the temperature area 28 in the X3 zone on the burner axis in FIG. 4(b).

In this way, the sum of the temperature areas of each zone on the burner coordinate axis is considered to be the combustion volume. In reality, the calculation shown in equation (9) will be performed.

■=Σ S (xt) ・ΔX ...(
9) However, V: Combustion volume 5 (xi): Temperature area in X+ section a: Burner exit position b: Position determined by burner size ΔX: Size of section between X+-1 and X. It is also possible to perform the above evaluation using

7) 160: Estimation of unburned content in the ash The unburned content in the ash is estimated from the flame stability X obtained above, the temperature rise G from the burner, and the combustion volume V.

The flame stability X indicates the stability of the combustion state near the burner, and the larger X is, the more stable the combustion is, and the more stable the ignition of the flame is.

As shown earlier, the temperature rise G from the burner is
A large temperature rise G from the burner indicates that the expansion phenomenon of the pulverized coal particles is promoted due to the extraction of volatile matter, which greatly affects the unburned content in the ash.

The combustion volume ■ evaluates the combustion temperature of the flame near the burner and the spread of the flame, and a large combustion volume V means that the combustion temperature is high, the spread of combustion is large, or the combustion temperature is high and the spread of the flame is high. This means that the spread of is large, indicating that the combustion of pulverized coal particles is promoted.

From the above, the combustibility of the flame becomes a function shown in equation (1).

F=f (X, G, V) - (11) Furthermore, when formula (11) is concretely expressed, it becomes, for example, formula (12).

However, F: Flammability X: Combustion stability G: Temperature rise from burner V: combustion volume a, b, c, αT'/T β : Fine particle size, fuel input amount, burner type Type, raw coal properties, air injection! (Secondary.

When estimating the unburned content in the ash from the combustibility shown by the constant formula (12) determined by the air input force method (including tertiary air distribution), air input force method (secondary and tertiary registers, vane opening degree), etc., (13) It becomes like the formula. Note that when evaluating the characteristic quantities of the combustion stability X, the temperature rise G from the burner, and the combustion volume V, the evaluation may be performed using different arbitrary regions of the combustion flame.

UBC=ni*F...(1
3) However, UBC: Unburned content in ash F: Combustibility K: Constant determined by combustion input amount, raw coal properties, burner type, and furnace condition 8) 170: Burner fuel supply amount, air supply amount, and air Supply method control If it is determined that the value of unburned content in the burner ash obtained by the method for estimating unburned content in ash shown above is still decreasing under the operating conditions such as coal type, load, NOx regulation value, etc. Flame stability and temperature rise are achieved by controlling at least one of the fuel supply amount, air supply amount (including secondary and tertiary air distribution), and air supply method.

The combustion volume will be improved and high-efficiency combustion operation will be performed to achieve the minimum unburned content in the ash under operating conditions such as coal type, load, NOx regulation value, etc. Furthermore, it is effective to display the value of unburned content in ash or stability X, temperature rise G from the burner, combustion volume V, etc. on one display device, and it is also effective as a monitoring device. Furthermore, since an actual boiler has a plurality of burners, the burner to be measured is selected depending on the operation of the boiler. For example, there is a method of measuring one piece for each stage or for each mill.

According to this embodiment, a first-order effect can be obtained.

(1) It becomes possible to estimate the unburned content in the ash, opening guidelines for highly efficient combustion operation.

(2) By measuring each burner stage, the combustion state of each stage can be grasped.

(3) Effective for understanding various combustion conditions such as high fuel ratio coal and water slurry.

(4) The combustion state can be grasped regardless of the burner structure or air supply method.

(5) It is possible to understand combustion conditions that follow various boiler operations.

(6) The burden on the operator can be reduced.

〔Effect of the invention〕

According to the present invention, the brightness or temperature at each position of the flame shape is calculated from the combustion flame of the burner, and the first feature quantity is weighted by the distance between a predetermined position and each position, and the area of the combustion flame shape is calculated. An estimation formula is calculated from the second feature weighted by the brightness or temperature at each position, and the third feature representing at least one temporal change in the brightness or temperature at each position of the combustion flame shape, or in the combustion flame shape. Since the unburned content in the ash can be calculated and displayed on the display device, the combustion status can be monitored accurately.

is a schematic processing flow diagram of the computer, FIG. 3(a) is an explanatory diagram of the temperature rise from the burner, FIG. 3(b) is a diagram of the temperature rise curve from the burner, and FIG. 4(a) is an explanatory diagram of the combustion volume. FIG. 4(b) is an explanatory diagram of the temperature area of each section on the burner axis.

1... Burner, 2... Flame, 6... Spectrometer, 7...
Half mirror 18...filter (wavelength λ1 transmission), 9...
... Filter (wavelength λ2 transmission), 10... Photoelectric conversion device, 11... Analog/digital conversion device, 12...
Digital image storage device, 13... Computer, 14...
Display device.

Claims (1)

[Claims] 1. A spectrometer that separates the combustion flame of the burner into two spectra, a filter that filters the two spectra into a single color with a different wavelength, and a photoelectric device that converts the single color into an electrical signal. A conversion device, an analog-to-digital conversion device that converts the electric signal into a digital value, a digital image storage device that stores the digital value as an image, and a combustion state of the boiler is calculated from the digital stored value of the digital image storage device. In a boiler combustion state monitoring device comprising a computer that displays the combustion state, and a display device that displays the combustion state, the computer calculates the brightness or temperature at each position of the combustion flame shape of the burner at a predetermined position and the combustion state of the boiler. a first feature weighted by the distance to each position; a second feature weighted the area of the combustion flame shape by the brightness or temperature at each position of the combustion flame shape; and each position of the combustion flame shape. A boiler combustion state monitoring device characterized in that the unburned content in the ash is calculated from the brightness or temperature at , and a third feature representing at least one temporal change in the shape of the combustion flame.