JPS60238613A - Monitoring method for combustion state - Google Patents

Abstract

PURPOSE:To estimate and monitor an amount of NOx produced, by a method wherein an oxidation flame as a high luminance region is extracted through measurement of a picture of flame in the vicinity of a burner outlet, and parameter about the degree of reduction of NOx is computed from the extracted oxidation flame. CONSTITUTION:Photo picture data 100-1 and 100-2 of flame are converted into an electric signal by an ITV camera 12, and is transmitted as an analogue picture signal 101 to a channel switching device 13. The channel switching device 13 transmits the analogue picture signal 102 of an assigned channel to an A/D converter 14 according to a channel selecting signal 105 outputted from a processor 16. The analogue picture signal is further converted into a flame picture signal 103 by the A/D converter 14, and the assigned flame picture data is stored in a flame memory 15. By the use of the flame picture data, the processor 16 calculates an index INOx indicating the degree of reduction of NOx, and an NOx value produced by a burner is estimated by the use of an NOx-INOx characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to monitoring the combustion state of pulverized coal, CWM [coal/water slurry], etc., and particularly relates to a method of monitoring NOx generated during combustion.

[Background of the invention]

As coal is viewed as an energy alternative to oil, pulverized coal combustion technology is attracting attention. It is said that the combustion technology for pulverized coal has already been established, but in recent years, new technology has been required to comply with regulations on air pollutant emissions.

Suru H4-φhonri l soup appetizer 9 city -← 7→to tσ) prison red stone to return to honor ↓ Vr l sebe te 8 minutes Due to the high content, nitrogen oxidation which causes air pollution during combustion things (hereinafter NO
x) occurs at a high concentration. Furthermore, thermal NOx is generated by combining with nitrogen molecules in the fuel, and prompt N is generated by combining hydrocarbons in the fuel with oxygen molecules in the combustion air.
Compared to Ox, it is less dependent on combustion temperature.

From this relationship, in order to reduce NOx in pulverized coal combustion, it is necessary to
NOx produced rather than combustion methods that do not produce
It is believed that it is necessary to provide a means to reduce the amount of nitrogen into N2 or the like. In addition, pulverized coal fuel has many factors related to its properties, such as fuel ratio, ash content, caking property, and particle size distribution, so it fluctuates greatly during the combustion process, and there are also changes over time such as pulverization, transportation, and ejection from burners. It cannot be ignored compared to combustion equipment for heavy oil, naphtha, I, NG, etc.

As described above, in order to achieve low NOx combustion of pulverized coal, a combustion method that takes into account (i) the NOx reduction effect and (ii) fluctuations in combustion phenomena is required. In contrast, in current commercial or industrial pulverized coal-fired boilers, the NOx concentration in the exhaust gas is monitored at the boiler outlet. In other words, the total amount of NOx generated in the combustion region consisting of several dozen burners and a multi-stage configuration is monitored as an average value. Therefore, since the conventional combustion state monitoring method does not measure the state inside the furnace, it has not been possible to understand the NOx reduction effect or fluctuations in combustion phenomena.

There is also a method using a flame detector that measures flame light -i:. However, this flame detector only monitors the average light intensity over the entire field of view to check for the presence or absence of flame, and has the disadvantage that it cannot obtain information regarding NOx produced by combustion.

[Purpose of the invention]

An object of the present invention is to provide a method for monitoring NOxifll (lJt degree or amount) generated as a result of utilizing the IN Ox reduction phenomenon during pulverized coal combustion for each burner.

[Summary of the invention]

The present invention measures a flame image near the burner outlet, extracts an oxidizing flame as a high-intensity region, calculates a parameter related to the degree of NOx reduction from the extracted I' ablation flame, and calculates a parameter regarding the degree of NOx reduction. The feature is that the number of NOx generated is estimated and monitored using the parameters.

Specifically, the method is characterized in that the position of the center of gravity of the oxidizing flame, the distance between the centers of gravity, the slenderness of the oxidizing flame, etc. are used as parameters related to the degree of reduction of NOx.

[Embodiments of the invention]

First, matters that form the basis of the present invention will be described.

Figure 1 shows three typical cases with different flame shapes of pulverized coal combustion, which are the motivation for the invention, (a) ItJ, N O
(b) shows a flame with extremely high x concentration;
The flame that is intermediate between a) and (b), (C) is N0xdl
Indicates a flame treatment with low At. The flame, that is, the combustion region of pulverized coal, consists of the primary combustion region Fl, where volatile matter is the main component, and the char (
2-burn combustion region 1 (2, 2,
and 4Y in the denitrification areas 1- and 4Y where the reduction action is promoted.
There is an extremely high correlation between the result of these "fake governments" and the NOx concentration generated.

In FIG. 1(a), there is no denitration region F3. In (b), a denitration region F3 is formed between the primary combustion head region F1 and the secondary combustion region. In (C), the primary combustion region F1 is not thick and short, and the denitrification region F3 is correspondingly wide.

The present invention cleverly utilizes the phenomenon that the NOx reduction effect increases as the primary combustion region becomes wider and shorter during pulverized coal combustion. This phenomenon can be explained qualitatively as follows.

When pulverized coal is ejected from a burner into a furnace in a high-m atmosphere, it ignites on the surface, is heated by combustion on the surface, and the volatile matter contained in the pulverized powder is separated and diffused to the surrounding area, forming a primary combustion area. be done. In this primary combustion region, a large amount of NO is produced by the reaction of equation (1) N2 (volatile N content) + 02
IN O-(1). On the other hand, HC is generated from the center of the heated flame, and the reaction of equation (2) occurs.

NO+・HC→・NX ...(2) Here, ・NXH・NH Afuiha・CNf Asu-Ko・
NX reduces NO in the downstream denitration region according to equation (3).

-NX+NO-+N2...(3) This becomes the NOx reducing agent. When oxygen is present, NX causes an increase in No.

-NX+0-)NO...(4) The key to low NOx combustion in Shikatsu-C1 is to burn near the volatile tone burner and make the central part of the flame high in temperature and lacking in M element. This combustion method is extremely effective in reducing NOx because most of the NOx produced by pulverized coal combustion is due to the combustion of volatile matter and only a small amount of NOx is produced by char combustion. In terms of flame shape, the primary combustion area is wide to promote the combustion of volatile matter and to reduce the diffusion of air to the center of the flame, and the overall amount of air is small to make the denitrification area oxygen deficient. Therefore, the primary combustion region becomes shorter.

Based on the above considerations, the index of low NOx combustion is INO! will be explained with reference to FIG.

We will call the region of high brightness near the burner an oxidation flame, and for this oxidation flame, the center of gravity is ti! I X+ = d z / d n ・”
(5) Distance between centers of gravity X 2 = d x / d B
-(6) Slenderness X3=ty/SF As (7), the index INox representing the degree of NOx reduction is lN0
Defined by X2Xi' ・X2 ・Kari' - (8).

Where, dII Nithroat diameter, tF: Perimeter length, SF two-sided ram (Fig. 2)/Touching part) Fig. 3 shows the NOx-lNOx obtained from the results of the combustion experiment.
Show characteristics. The present invention estimates the amount of NOx generated during combustion by determining this characteristic in advance and actually measuring INox.

An embodiment of the present invention will be described with reference to FIGS. 4 and 5. The combustion state monitoring device according to the present invention has an image guide (11
-1,1l-2), ■TV camera 12 (12-1,1
2-2), a channel switching device 13, an A/D converter 14, a frame memory 5, a processor 16, and a display device 17.

Pulverized coal burner 2 (2-t, 2-2., '2-3)
The image guide 11 is attached to the viewing window of the foiler 1 so that the nearby flame image ν is equal to itl'd+'l. The head of the image guide 11 is cooled with water or air so that it can withstand the atmosphere, and is also structured to inject air from around the front to prevent pulverized coal combustion ash from accumulating. The optical plane image of the flame 100-1゜100-2 is I
The analog image signal 101 (101-1, 1
01-2) and is transmitted to the channel switching device 13.

This channel switching device u13 transmits the analog image signal 102 of the designated channel to the A/D converter 14 in accordance with the channel selection signal 105 output from the processor 16. Further, the flame image data is converted into a digital image signal 103 by the A/D converter 14, and the specified flame image data is stored in the frame memory 15.

Using this flame image take, the processor 16 executes (8)
INo, 'il- defined by the formula is calculated, and the NOx value generated from the burner is estimated using the NOx to INox characteristics shown in FIG. The processing procedure in this Brissor 16 is shown in FIG. In FIG. 5(a), ■In the flame image take input 200, the flame image data of the designated channel is taken into the frame memory, and ■In the flame shape feature extraction 201, the centroid coordinates and perimeter of the oxidation flame are
Start by following the procedure shown in Figure (13). (15ox) Calculation 202 is performed according to equation (8). ■NOx estimation 2
In 03, N stored in advance as a data table
Using the Ox -lNOx characteristics and the throat diameter, l
Convert NOx value to NOx value.

■The display 204 shows the frame memory flame image take, channel number, N'Ox value, lN0IT value, Xl-X
3 is displayed on the display device 205.

Repeat the operations from ■ to ■ above until all channels are completed.

According to this embodiment, the NOx value in each burner of the boiler can be determined.

According to the above embodiment, N generated by pulverized coal combustion
Ox value can be measured for each burner, so (1
) Combustion conditions in the burner, e.g. primary combustion zone and 2
It is possible to maintain appropriate air distribution in the next combustion area and swirl strength when blowing out air, (2) it is possible to understand imbalances in combustion conditions between burners, (3) load and fuel properties. This has the advantage of being able to detect changes in combustion conditions due to changes in equipment over time.

〔Effect of the invention〕

According to the present invention, the amount of NOx produced by pulverized coal combustion can be estimated for each burner.

[Brief explanation of the drawing]

FIG. 1 is a diagram comparing flame patterns that are the basis of the present invention. FIG. 2 is a diagram showing a flame shape monitoring method according to the present invention. FIG. 3 is a diagram showing the relationship between the NOx value (concentration) generated by combustion and INox. FIG. 4 shows the configuration of a device ego showing a simple embodiment of the present invention, and FIG.
A) (2) shows the calculation flow. l... Wheeler, 2... Differential coal burner, 11... Image guide, 12... Imaging device, 13... Channel switching device, 14... A/D converter, 15... Frame memory, 16...Processor, 1'7...Display device, 100 baskets 1 (-2<) (22<) 箭 2nd INOx (-1 躬 S (,4)

Claims (1)

[Scope of Claims] 1. The combustion state of combustion by a noise composed of a fuel injection nozzle that injects a mixture of pulverized coal fuel and gas or water and a combustion air nozzle provided around the fuel injection nozzle. In the monitoring method, a flame image near the burner outlet is measured to extract an oxidation flame as a high-speed region, a parameter related to the degree of NOx reduction is calculated from the extracted oxidation flame, and the calculated parameter is A combustion state monitoring method characterized by: estimating the amount of N and Ox produced using the method, and monitoring the amount of NOx produced in a furnace. 2. A combustion state monitoring method characterized in that at least the position of the center of gravity of the oxidizing flame is used as a parameter regarding the degree of reduction of NOx as set forth in claim 1. A combustion state monitoring method characterized in that the distance between the centers of gravity of at least two oxidation flames formed on a flame monitoring plane is used as a parameter regarding the original degree. 4. A combustion state characterized in that the ratio of the circumferential length and area of the oxidizing flame is used at least as an index representing the slenderness of the oxidizing flame as a parameter regarding the degree of reduction of NO8 as set forth in claim 1. Monitoring method.