JPH02306017A - Combustion method for burner - Google Patents

Abstract

PURPOSE:To enable easy reregulation of a burner into an ideal combustion state by a method wherein when the burner is previously in a given combustion state, a ratio of the area of a given section to the area of all sections is determined, and an air flow rate, a fuel flow rate, and a recirculating gas amount are controlled so as to maintain the same ratio during operation. CONSTITUTION:Temperatures at points at the side of flame obtained by measurement are divided at intervals of a proper temperature step, for example, 10 deg.C to prepare a constant temperature line distribution diagram ranging from 1500 deg.C to 1200 deg.C. The area of each temperature section is determined, the areas are S1, S2, S3, and S4. In the case S0=S1+S2+S3+S4, regards a ratio between R1=S1/S0 and R2=(S1+S2)/S0, a value in the combustion state of each burner in a normal combustion state is previously experimentally determined. An air flow rate control damper 11, a primary air flow rate regulating damper 13, and a secondary air flow rate regulating damper 14, and a fuel injection valve 08, a recirculating gas flow rate control damper 10, and a burner recirculating gas regulating damper 12 are operated so that R1 and R2 are adjusted to respective values. The combustion state of each burner can be easily maintained in an excellent state.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a combustion method for a burner such as a boiler.

[Conventional technology]

A conventional boiler will be explained with reference to FIGS. 7 to 9. FIG. 7 is an overall configuration diagram (fuel supply line and air line omitted), FIG. 8 is an overall configuration diagram including the fuel supply line, and FIG. 9 is an overall configuration diagram including the air line.

As shown in FIGS. 7 to 9, combustion in a conventional boiler is performed using air in which fuel is simultaneously mixed with fuel sprayed from a plurality of burners 02 provided in a boiler 01. In conventional low NOx combustion, combustion does not occur completely in the -flame combustion zone 03, but some unburned matter remains in the secondary combustion zone 04, where OFA or second-stage combustion air is separately blown. Complete combustion by 05. Thereafter, it passes through the flue 06 and is discharged from the chimney 07. In Figures 8 and 9, 0
8 is a fuel injection valve, 09 is air for each burner, recirculation gas piping, 15 is a recirculation gas flow rate control damper, 11 is an air flow rate control damper, 12 is an individual burner recirculation gas adjustment damper, 13 is individual burner secondary air Flow rate adjustment damper 14 does not indicate an individual secondary air flow adjustment damper.

In general, NOx in exhaust gas is regulated by 07 output l from the chimney, so the final exhaust gas Ij + NOx is 7Ii at the base of the chimney.
11 determined. The NOxfi degree in the exhaust gas is finally determined through this combustion process, so the NOxfi degree of a single burner
The Ox generation situation does not directly lead to the final NOx. However, since air is supplied to the collection of combustion gas from several burners in the secondary combustion zone 04, the fact that each burner burns stably and uniformly and has a constant NOx level means that the secondary combustion Although it is essential to secure the final NOx level by adjusting the amount of air 05 for second-stage combustion in area 04, there has been no technology to evaluate the NOx level of each burner based on its combustion results. Therefore, we had to look at the final output and adjust many parameters by estimation, which was a kind of virtuoso process.

[Problem to be solved by the invention]

The conventional method described above has the following problems and issues.

(a) The optimal combustion conditions set during the initial adjustment operation of the plant change depending on the progress of the plant operation.

However, there is no method to accurately grasp the combustion state of each burner.

(bl) If changes in the combustion state of each burner are accurately grasped and adjusted, it becomes easy to maintain the entire combustion system in a good state, that is, in a low NOx state.

[Means to solve the problem]

The present invention takes the following measures to solve the above problems.

(1) In a combustion device with multiple burners, the surface temperature distribution of the burner flame during combustion is determined for each predetermined temperature range l1j
When the burner is in a predetermined combustion state, calculate the ratio of the area of the predetermined section to the area of all sections, and adjust the air flow rate, fuel flow rate, and recycle to maintain the same ratio during operation. The amount of circulating gas can now be controlled.

(2) As a burner-generated NOx monitoring method, in a combustion device with multiple burners, the surface temperature distribution of the burner flame during combustion is sequentially divided into predetermined temperature ranges, the area of each division is determined, and the area of each division is determined. Determine the ratio of the area to the area of all sections, and calculate the ratio determined in advance and the N of the combustion device described above.
The amount of NOx generated is monitored from the correlation with the amount of Ox generated.

[Function] (1) With the above F stage, the surface temperature distribution of the burning burner flame is measured using, for example, a thermal camera, and is sequentially divided into predetermined temperature ranges from the high temperature side to the low temperature side. Next, for example, the ratio of the area of the maximum temperature section and the area of the maximum temperature section plus the next temperature section to the area of all the sections is determined. The air flow rate, the fuel fuel 4 flow rate, and the recirculation gas amount are adjusted so as to maintain the above-mentioned ratio in a predetermined combustion state determined in advance. Since there is a strong correlation between the combustion state and the above ratio, the combustion state of the burner can be maintained in a good state in this way.

(2) By the means described above, the surface temperature distribution of the burner flame during combustion is measured using, for example, a thermal camera, and is sequentially divided into predetermined temperature ranges from the high temperature side to the low temperature side. Next, for example, the ratio of the area of the maximum temperature section and the area of the maximum temperature section plus the next temperature section to the area of all the sections is determined. The amount of NOx generated is determined from the correlation between the ratio determined in advance and the amount of NOx generated by the combustion device and the actual δ ratio, and the amount of NOx generated is monitored.

In this way, burner-generated NOx can be easily monitored.

〔Example〕

(1) An embodiment to which the method of the present invention described in claim (1) is applied will be described with reference to FIGS. 1 to 4, FIG. 8, and FIG. 9.

Note that the description of the portions described in the conventional example will be omitted to avoid redundancy, and the description will mainly focus on the portions related to the present invention.

First, as shown in FIG. 1, the surface temperature distribution of the flame during combustion in the burner 02 is measured by an optical method.

In this case, the definition of the surface temperature of the flame is complicated because the transmittance changes depending on the type of flame, but in this example, the NOx generation status is estimated by comparing combustion using the same fuel and the same burner. The method and definition of the temperature to be measured are not very strict.

As the measurement method, any of the known methods such as optical method (thermal camera method, spectral method), thermocouple method, etc. can be adopted. For example, for a screen obtained with a thermal camera, the screen can be divided into appropriate dimensions and the area can be determined for each temperature range. Divide the temperature at each point on the flame side obtained by measurement into appropriate temperature steps, for example, every 100°C as shown in Figure 1, and create an iso-dot line distribution map from 1,500°C to 1 and 200°C. . The flame is at its highest temperature in the center of the warp 15
The temperature gradually decreases outward from the point, but in order to determine which point is the flame, the point where there is no difference in temperature from the surrounding gas temperature is defined as the entire flame (total area) 12.

Next, find the area of each temperature category and calculate 511Sz+S:++S
Set it to 4. At this time, the relationship between the area of each section and the temperature range is as shown in Table 1.

Table 1 Therefore, the area S0 of the entire section is given by (1) 2.

S o = S + + S z + S s + S
a -...-...-(1) Next highest temperature category N
The area of , S, is the ratio R1 to the area of all sections of (2)
Ask from the second.

R+ ” S , / S o '−・・−・−・・−
.--(2) Similarly, the ratio R2 of Sl and S2 to So is determined from equation (3).

Rz= (S++Sz)/So --knee・(3) Regarding the above ratios R+ and Rz, the values for the combustion state of each burner in the normal combustion state of the boiler are experimentally determined in advance, and the values are determined in advance during actual operation. , 11, . 11. Distribution of air flow rate (opening/closing of air flow rate control damper 11, secondary air flow rate adjustment damper 13, and secondary air flow rate adjustment damper 14 in Fig. 9) and adjustment of fuel flow rate (in Fig. 8) so that (opening/closing of fuel injection valve 08), adjustment of recirculation gas amount (9th
Opening and closing of the recirculation gas flow rate control damper 10 and the burner recirculation gas adjustment damper 12 shown in the figure are performed. In this way, the combustion state of each burner can be easily maintained in good condition.

Next, using this ratio R2 as an index, an evaluation test of the combustion state of the burner was conducted in an actual plant, and the results are shown in FIG. Furthermore, FIG. 3 shows a layout diagram of the burners during the above test. As can be seen from FIG. 2, the optimum combustion state is the low NOx and low dust state obtained under condition 4. In the test, a wide range of combustion conditions were simulated by changing the amount of O1, which is a typical element that changes combustion conditions. That is, the air flow rate control damper 11 (FIG. 9) was opened and closed to increase or decrease the total air amount. Under optimal combustion condition 4, R2 shows a high value for all three burners, indicating that the combustion state is good and uniform. Under conditions 1 to 3, the R2 values of the three burners are low and vary widely. This indicates that the combustion condition of the burner has deteriorated and that uniformity has disappeared. As a result, the amount of NOx or soot generated increased.

The above experimental results also demonstrate that the combustion state can be accurately evaluated using the indicators R1 and/or R2 of this example.

Although the measurement of the surface temperature distribution has been described only conceptually above, the apparatus for determining the surface temperature distribution of the burner flame will be described in detail below.

In FIG. 4, one or more image fibers 3 for observing the flame 2 of the burner 02 are installed in the furnace l, and a color television camera 4 is connected to the image fibers 3. The output of the camera 4 is a dynamic color video display 20.
It is also connected to a decoder 5, and its output is manually input to a frame memory 7 via a red (R), green (G), and blue (B) video device 6. The output of the same frame memory 7 is a primary calculation circuit (
R/B) 8. Primary calculation circuit that calculates the time difference between G signals (
G(t,)-G(h)) 9 and a primary arithmetic circuit (R-B) 10 that calculates smoke. The output of the primary arithmetic circuit (R/B) 8 is sequentially connected to a temperature distribution display 16, a secondary arithmetic circuit 17, and an evaluation circuit 1. Similarly, the above-mentioned -order arithmetic circuit (G(t,)-G(t,
)) 9 and the outputs of the arithmetic circuit ('R-B) 10 are each directly connected to the R-1 circuit 18. Furthermore, the output of the evaluation circuit 18 is connected to a display 19.

In the above apparatus, an image captured by the color television camera 4 via the image fiber 3 is directly sent to the dynamic color image display 20 to provide a monitor image to the operator and the like, and at the same time is sent to the decoder 5. Generally, the output signal of the color television camera 4 is sent over a single line by combining red, green, and blue separated images in order to save on transmission lines, so this is separated into the original two-color image 6. . This three-color (red, green, blue) image is proportional to the intensity of each component of the spectrum radiated by the flame 2. The images separated into these three colors are used for later calculations.
It is recorded in the H frame memory 7 in the form of a video. Based on this video record, the temperature distribution representing the flame is calculated based on the following principle.

The radiation from a black body at a certain temperature T' is expressed as the following (4) 2 according to Blank's radiation law.

E(λ・T)=C,/λ'flXp(Cz/λT-1)
-(4) where λ: wavelength (I!m) T: absolute temperature (K) C1 first radiation constant of blank 3.74xlO' (W-1 cm-") C, second radiation constant of blank 1438B (-・k) The radiant energy distribution of a substance other than a blackbody, that is, a flame, is (
4) The radiation curve in Figure 5 is obtained by multiplying the equation by its emissivity ελ.
In this case, if the flame temperature changes, a group of radiation curves with the same tendency can be obtained using the temperature T as a parameter. Note that this curve changes similarly when the emissivity ελ changes. However, it is well known that even if the emissivity changes, the radiant energy ratio of two wavelengths is a function only of temperature as long as the ratio of emissivity ε at the two wavelengths is constant, and it has been commercialized as a dichroic temperature section. ing. R (red), G (green), B (blue) as shown by the dotted lines superimposed on the radiation curve in Figure 4.
For example, for a color television camera with a relative sensitivity curve of R
The temperature is calculated from the and B signals using R/B in the same manner as the two-color temperature section. In this case, the color signal is obtained by integrating components around the center wavelength of the relative sensitivity curve of the color along the radiation curve.

In this way, the temperature distribution of the flame is calculated.

(2) An embodiment to which the method of the present invention described in claim (2) is applied will be described with reference to FIGS. 6 and 7.

Note that the explanations of the parts explained in the conventional example and the above-mentioned embodiments will be omitted to avoid redundancy, and the parts related to the present invention will be mainly explained.

As described above, the ratios R+ and Rz, which are indicators of the combustion state of each burner, are determined by the above formula (1) or 3),
The amount of NOx generated by the boiler and R1 determined experimentally in advance
The amount of NOx generated is monitored based on its correlation with +R1.

In order to concretely demonstrate the above, an experimental example will be shown in which one burner is burned in a test furnace and the correlation between the total amount of NOx at the furnace outlet and the ratio RI + lh is determined, and the relationship shown in Figure 6 is obtained. It is being Therefore, if the correlation between the above ratios R1 and R2 of each burner 02 (Fig. 7) and the NOx generation amount of boiler 01 is determined in advance, and the above ratios R1 and RZ are measured and determined, NOx generation due to changes in combustion conditions can be determined. Volume changes can be monitored.

〔Effect of the invention〕

As explained above, according to the present invention, (1) changes over time in the combustion state of individual burners can be grasped by a target GTJ;
This can be easily readjusted to a more ideal combustion state, and the boiler as a whole can be maintained in a well-balanced combustion state.

(2) Since changes over time in the combustion state of individual burners can be understood as NOx-related amounts, it is possible to easily readjust to a more ideal combustion state, and reduce the NOx emissions of the boiler as a whole.
This allows for a well-balanced combustion state to be maintained.

[Brief explanation of drawings]

FIG. 1 is a flame temperature distribution diagram as an explanatory diagram of the operation of an embodiment related to claim (1) of the present invention, FIG. 2 is an explanatory diagram of the operation of the same embodiment, and FIG. 4 is a block diagram of the temperature distribution measuring device of the same embodiment, FIG. 5 is an explanatory diagram of the operation of the temperature distribution measuring device of the same embodiment, and FIG. 6 is a claim of the present invention. Fig. 7 is an overall configuration diagram of a conventional boiler (fuel supply line and air line omitted), and Fig. 8 is an overall configuration diagram of the conventional boiler (fuel supply line and air line omitted). FIG. 9 is an overall configuration diagram (including air lines) of the conventional example. 0! ... Boiler body, 02 ... Burner, 03
...-Secondary combustion zone, 04...Secondary combustion zone, 05
...Secondary air blown in, 06...Arrow indicating flue, 07...Chimney, 08...Fuel injection valve, 09...Air in burner unit, recirculation gas piping, 1,
2...Flame total side area, 11...Air fL amount control damper, 12...Individual burner recirculation gas regulating damper, 13...
・Individual burner next air flow I#JR damper, 14...
Individual burner secondary air flow rate adjustment damper, 15... Recirculation gas flow rate control damper. Agent Patent attorney Akira Sakama 2 persons Fig. 2 ft-f + Fig. 4 □ Matanaga (M) High School) Graduated from large area (R1, R2) Fig. 8

Claims (2)

[Claims] (1) In a combustion device with multiple burners, the surface temperature distribution of the burner flame during combustion is sequentially divided into predetermined temperature ranges, and when the burner is in a predetermined combustion state, the area of the predetermined division is A burner combustion method characterized by determining the ratio of all sections to the area and manipulating the air flow rate, fuel flow rate, and recirculation gas amount so as to maintain the same ratio during operation. (2) In a combustion device with multiple burners, the surface temperature distribution of the burner flame during combustion is sequentially divided into predetermined temperature ranges, the area of each division is determined, and the area of the predetermined division is the area of all divisions. A combustion method for a burner, in which the amount of NOx generated is monitored from the correlation between the predetermined ratio and the amount of NOx generated by the combustion device.