JPS6036825A - Control method for combustion flame and device thereof - Google Patents

Abstract

PURPOSE:To enable highly precise control of a combustion flame without disturbance of a combustion flame, by measuring temperature distribution in a flame in non-contact manner. CONSTITUTION:In a plurality of positions in a combustion flame, spectral analysis is effected by a light detector 10, and vibration spectrum of the obtained OH is calculated to find temperature distribution in flame. A storing circuit 12 stores temperature distribution in flame measured under an optimum combustion condition. A comparing circuit 13 compares temperature distribution in flame at a present point of time, which is outputted from a computing circuit 11, with temperature distribution in flame under the stored optimum combustion condition, and a difference therebetween is outputted to a control circuit 14. The control circuit 14 inputs an output from the comparing circuit 13 to decide a proper control command to a control drive part and output a command as a control signal. The outputted control signal is fed to a control place to perform control of flame into an optimum combustion condition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for controlling a combustion flame, in which the combustion flame can be controlled with high precision by measuring the temperature distribution inside the flame in a non-contact manner.

[Background of the invention]

For example, in the main burner of a boiler in a thermal power plant or the like, it is necessary to control the combustion flame in order to obtain a combustion state with low NOx and low unburned content as an optimum combustion state. It's a size.
In addition to NOx, -1...carbon triride, oxygen, or sulfur dioxide gas is also determined and used to control the burnout flame.

Conventionally, when controlling a combustion flame, a method has generally been adopted in which gas analysis in exhaust gas is performed and the analyzed value is used to output a signal to a control system.

For example, in order to understand the NoXO concentration in exhaust gas, the exhaust gas is actually guided from the flue to various NOx meters and the concentration is measured. If it is not possible to directly introduce the flue gas into the measurement device, a sampling syringe is used to collect the exhaust gas from the flue, and the concentration is measured using a NOx meter. In either method, gas is collected and control is performed by outputting a control signal based on the analyzed value.

Such a combustion flame control method, which is performed by collecting exhaust gas and analyzing the exhaust gas and using the analyzed values, has the disadvantage that it cannot cope with sudden changes in the combustion state.

Therefore, it is conceivable to perform highly accurate control based on observation of the flame itself. For example, control that detects the gas concentration distribution, temperature distribution, etc. in the flame near the burner outlet and maintains the flame in the optimal combustion state based on this is considered to be a highly accurate system.

However, conventionally, even in such cases, the gas concentration distribution in the flame near the burner outlet is usually measured by inserting a sampling probe into the flame and sampling the gas. The temperature distribution is also measured by inserting a thermocouple. Therefore, either method disturbs the flame, making it difficult to accurately measure the distribution.

[Purpose of the invention]

An object of the present invention is to provide a combustion flame control method and apparatus W that can measure the temperature distribution of a combustion flame without disturbing the combustion flame, and can improve the accuracy of combustion flame control.

[Summary of the invention]

In the combustion flame control method according to the present invention, the temperature distribution in the flame is measured non-contact by an optical method, and the measured temperature distribution is used to control the combustion flame.

The combustion flame control method according to the present invention preferably involves X-spectroscopic analysis of the generation of hydroxyl radicals (hereinafter referred to as OH), which are present in large quantities in the combustion flame, and from the resulting spectral waves and emission intensity. The combustion flame is controlled by calculating the temperature of the flame, measuring the temperature distribution, and comparing the distribution with the temperature distribution of the flame in the optimum combustion state and outputting a control signal.

That is, the flame temperature is measured without contact, the measurement point is moved to determine the temperature distribution in the flame, and the flame is controlled based on the distribution.

In addition, in the combustion flame control device according to the present invention, a calculation circuit that inputs the results of spectroscopic analysis of the emission spectrum of OH in the flame and calculates the temperature distribution, A storage circuit that stores distributions, a comparison circuit that compares an output from the calculation circuit with an output from the storage circuit, and a control circuit that outputs a control signal based on the output from the comparison circuit. There is.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Flame is ejected from the burner 2 attached to the combustion furnace 1,
The flame light is from two viewports 3A.

It is designed to receive sunlight from 3B. The illuminated light is
Each of them is converted into an electric signal by a spectroscopic camera 4, and its output is led to a signal controller @1+ device 5, which outputs a control signal from a signal controller in response to the output.

As shown in FIG. 2, each spectroscopic camera 4 is provided with a condenser lens 6 and an imaging lens 7 for condensing light from the view boats 3A and 3B. The condensing point is the focal length position of the condensing lens 6, and the light around the focal point is most intensely observed.

These condensing lenses 6i-j.

It is movable back and forth along the sight rail 8 via a lens drive device 9, and the focal point of the condenser lens 6, that is, the lighting point, can be moved back and forth. By moving the lighting point back and forth, it is possible to observe the fault lines inside and outside the flame.

Due to the characteristics of a convex lens, the light emitted from the focal point becomes parallel light after passing through the convex lens. Furthermore, the light that has entered the convex lens at i'lL as a parallel ray has a characteristic of being focused. Utilizing this characteristic, the parallel rays that have passed through the condenser lens 6 are focused by the imaging lens 7, and a photodetector 10 is placed at the focus position.
The condenser lens 6 is arranged 7/, ``.
The light collected at the focal point 1 (1 position) becomes a strong light and forms an image on the detection part of the photodetector 10.

Therefore, the focusing position, that is, the observation The position can be changed and the UT layer of flame can be observed both inside and outside.

In this embodiment, the temperature in the flame is measured without contact by spectroscopically analyzing the emission spectrum of .OH in the flame. That is, a photodetector lO1, such as a photomultiplier tube, which has a high detection capability is used in the wavelength range in which the emission spectrum of .OH is observed. In addition to a photomultiplier tube, the photodetector 10 includes a photodiode and a spectrum multichannel analyzer (S, M, A,
) etc. may be used. The photodetector 10 converts the optical signal into an electrical signal and sends the electrical signal to the signal processing system.

Next, the signal processing system will be explained using the diagram shown in FIG. This processing system inputs the results of spectroscopic analysis of the emission spectrum of .OH in the flame and calculates the temperature distribution using an arithmetic circuit 11. A memory circuit 12 records the temperature distribution in the flame in the optimum combustion state, a comparator circuit 13 compares and determines the output from the arithmetic circuit 11 and the output from the memory circuit 12, and control 1111 is performed by the output from the comparator circuit 13. It has an iti control circuit 14 that outputs newsletters.

The arithmetic circuit 11 includes a command circuit that outputs a command to the photodetector to convert an optical signal of an arbitrary wavelength into an electrical signal, a calculation circuit that inputs the output from the photodetector and calculates the temperature, and a flame detector. A lens drive control circuit for driving a lens drive device 9 in order to condense light at a position in the middle is formed.

The calculations performed by the calculation circuit are based on the emission intensity and wavelength of spectral lines obtained by spectroscopic analysis of the emission of .OH, which is widely confirmed to exist in flames. Fourth
・OH at any point in the combustion flame measured in the figure
An example of the spectroscopic analysis results is shown. This is an analysis result called a vibrational rotation spectrum of .OH, where the vertical axis is the emission intensity and the horizontal axis is the wavelength. The temperature is calculated from the values of the horizontal axis position (wavelength) and the vertical axis position (emission intensity) of the peak of the spectral line obtained as a result of the spectroscopic analysis.

The basic formula for calculation is given by the following formula.

1n(IW/W'-P-gI=-E/kT ten constant,
IIJ is the emission intensity at wavenumber W, W is the reciprocal of the growth of the spectral line, P is the transition probability to energy level E that emits light at wavenumber W, g is the multiplicity, k is Boltzmann's constant, and T is the absolute temperature. . That is, if we calculate the intensity of the spectral line obtained by performing spectroscopic analysis, calculate the flame on the left side, and plot it against E, then 1 of the 1M line is l/kT, and k is Since it is a constant, T is observed.

As a result of the above, the light is focused at an arbitrary point in the combustion flame and spectroscopically analyzed by the photodetector 10. By calculating, the temperature at any one point where the light is focused can be determined. Therefore, if this operation is performed at a plurality of locations in the flame, the temperature in the flame can be determined.

Next, the memory circuit 12 records the temperature distribution in the flame measured and calculated during the optimum combustion state. It is something that is φ.

The optimal combustion state referred to here varies depending on the nature of the flame and is determined at any time, but for example, in the case of a main burner of a boiler such as a thermal power plant, it is a combustion state with low NOx and low unburned content.

Further, as described above, the comparison circuit 13 receives the current temperature distribution in the flame output from the arithmetic circuit 11 and optionally the temperature distribution in the flame as described in 1.
The difference between the temperature distribution and the temperature distribution in the flame during the optimal combustion state is compared, and this difference is output to the control circuit 14.

Further, the control circuit 14 inputs the output from the 1-hi recovery circuit 13, determines an appropriate control side j command to the control section 11W, and outputs the command as a control signal.

Thus, the output combustion signal is guided to an arbitrary combustion point, for example, a shaft regulator, and control is performed to achieve an optimum combustion state. Below is an example of
This will be explained with reference to FIGS.

In FIG. 5, reference numeral 15 denotes a burner, and a fuel injection nozzle 18 having a circular combustion dispersion cone 17 whose diameter increases toward the outlet is provided near the outlet of a burner tip 16 for ejecting fuel. A gas firing nozzle 20 with a spark plug 19 for preheating the combustion furnace and combustion ignition is provided on a concentric circle around the outer circumference of this fuel injection tax nozzle 18, and an air nozzle 21 for sending combustion air is provided on a concentric circle around the outer circumference of this nozzle. It is said to be composed of Note that the circular fuel dispersion cone 17 includes:
In order to set the optimum cone position, a rod-shaped adjustment shaft 22A and an adjuster 2 are installed from the apex of the circular part to the outside of the burner.
2B is provided.

FIG. 6 shows the state of dispersion of pulverized coal when pulverized coal is used as a fuel. The pulverized coal conveyed through the central pipe is ejected from a pulverized coal injection nozzle 18 squeezed by a pulverized coal dispersion cone 17 and dispersed radially. At this time,
Combustion air is supplied from a pipe 23 arranged on the concentric outer circumference of the central pipe. As a result, sufficient air is supplied to the radially dispersed pulverized coal, and a high air particle and combustion zone are formed. Furthermore, if the front part of the cone is pierced, the pressure is more negative than the surrounding area, so a part of the pulverized coal is rolled up. However, since there is little diffusion of air supplied from the outer periphery, a low air specific firing area is formed.

That is, FIG. 7 shows the fuel concentration distribution and air ratio distribution. In the high air ratio combustion region, NOx is produced, and in the low air ratio combustion region, reducing substances such as NI-13, I-I CN, and hydrocarbons are produced and reduced. NH3 or IIcN NO
Since X is reduced to N2, NOx and these reducing substances are mixed, making low NOx baking possible. In addition, since the high air ratio combustion flame surrounds the low air ratio combustion flame, the unburned fraction t generated by the low air ratio combustion flame is combusted by the Takahashi vaporization/Notaka flame, and the unburned fraction decreases. I can figure it out.

In burner ]-5 shown in this embodiment, forming the fuel concentration distribution shown in FIG. 7 forms the optimum combustion state. It is used to adjust the cone by moving it back and forth depending on the tone and version. In other words, maintaining the fuel concentration distribution, air ratio distribution, and temperature distribution shown in Figure 7 is
This will maintain proper combustion conditions. Therefore, it is sufficient to observe only one of these distributions. In other words, fuel concentration distribution and air ratio distribution had to be measured by actually inserting a zumbling probe into the flame, which disturbed the flame and made time-responsive control impossible. When using the non-contact temperature measurement method according to this embodiment, ideal control can be performed by observing the flame temperature distribution as shown in FIG.

In addition, by non-contactly measuring the temperature distribution in the flame at the tip of the burner in a short time, determining the temperature distribution, and controlling the flame accordingly, it is possible to quickly respond to and highly accurate control of sudden changes, etc. becomes.

Next, a practical example using specific numerical values will be explained with reference to FIGS. 8 to 11.

Figures 8 and 9 show schematic diagrams of the burner used in this experiment, along with dimensions in m/m.

Air and propane are introduced into the burner through pipe C, and mixed chamber B
Mix them thoroughly to form a premixed fuel. The premixed fuel is uniformly ejected from the perforated plate A to form a premixed flame.

The situation is shown in FIG. F in the figure is a premixed flame. FIG. 11 shows the results of measuring the flame temperature distribution in the flame by collecting only the light from the center N1 of the flame. The distance l from the burner tip in Fig. 10 is the first
This corresponds to the distance from the burner tip in Figure 0. Therefore, the air ratio calculated from the exhaust gas analysis results when the flame temperature distribution was measured and the exhaust gas Eve Y value is shown in the table below.

Exhaust gas analysis value and air ratio (λ) From the table above (exhaust gas analysis results in ■ in Figure 11), the carbon monoxide (Co) concentration, which is an indicator of incomplete combustion, is approximately 1%, and the oxygen (0□) concentration is approximately 1%. It can be seen that the flame temperature is low and close to complete combustion.Furthermore, the flame temperature also shows a maximum of 1750C,
It can be seen that the combustion efficiency is close to the calculated value of propane's adiabatic flame temperature of 2000C.

The flame temperature distribution shown in (2) is a preferable distribution for the burner used in this experiment, both from the exhaust gas analysis value and from the flame temperature. Unfortunately, the air ratio of this flame is also 0.97.
This can be seen from the fact that the value is very close to 1.00, which indicates the best flammability. Therefore, the symbol (■) in FIG. 11 is memorized as the optimum flame temperature distribution of the burner used in this experiment.

Next, as an example of a case where the combustion condition is poor, the amount of air introduced to the burner is changed excessively, and the flame temperature distribution in the flame is measured in the same manner as described above.
It was a far cry from ■. This indicates that the combustion condition is deteriorating. However, as a result of a 4-hour gas analysis of this flame, it can be seen from the results that 5% -carbon oxide was generated, and some oxygen remained, indicating extremely poor combustibility. Therefore, it is sufficient to control the flame so that the flame temperature distribution shown by ■ approaches the flame temperature distribution shown by ■, and in this experiment, control @1 can be achieved by changing the amount of air introduced into the burner. That is, control is performed by slightly changing the opening/closing of the pulp to change the amount of air, measuring the flame temperature distribution, and outputting the flame temperature distribution to the pulp opening/closing portion so as to approach the temperature distribution.

In addition, as another example, there is a case where the flame temperature distribution results as shown by ■ in FIG. 11. This result is also far from ■, and shows that the combustion efficiency is low (c combustion), which is far from the optimal combustion state.Therefore, as in the case of ■, the amount of air introduced into the burner is controlled by the pulp. Manipulate the opening degree and control the flame temperature distribution to become Ql.
Do the following.

Incidentally, the analysis results of the exhaust gas of the flame exhibiting the flame temperature distribution as shown in (■) are shown in the table above. Approximately 4% oxygen remains in the exhaust gas, indicating that an excessive amount of oxygen is being absorbed into the burner. Therefore, as a result, the pulp is adjusted in the direction of squeezing the air.

From the above examples, the flame temperature distribution can be measured non-contact by analyzing the flame emission, and the distribution during optimal combustion can be stored, and the flame temperature distribution when other combustion efficiency is low is stored. By comparing the contents, it was confirmed that the flame could be controlled.

〔Effect of the invention〕

As described above, according to the present invention, the flame temperature distribution near the burner outlet can be measured without contact, and the flame itself can be controlled with high accuracy based on the measured temperature distribution. Therefore, excellent effects such as being able to maintain an optimal combustion state for a long time and realizing highly efficient combustion are achieved.

[Brief explanation of the drawing]

The figures show one embodiment of the present invention, in which Fig. 1 is a cross-sectional view showing the flame measuring section, Fig. 2 is a cross-sectional view showing the spectroscopic camera, Fig. 3 is a diagram showing the signal processing system, and Fig. 4 is a cross-sectional view showing the flame measuring section. is a graph showing the vibrational rotation spectrum of ・OH in a combustion flame, the fifth
The figure is a cross-sectional view showing the 4'+J configuration of the nookuna, Figure 6 is a schematic diagram showing the dispersion status of pulverized coal, and Figure 7 is a diagram showing the fuel concentration distribution, air ratio distribution, and temperature distribution at the burner outlet piercing. Fig. 8 is a cross-sectional view showing the experimental burner, Fig. 9 is a plan view of Fig. 8, Fig. 10 is a schematic diagram showing the same combustion state, and Fig. 11 is the experimental result. It is a 71 yen sex diagram shown. 1... Combustion furnace, 2... Burner, 3A, 3B...
Pyu boat, 4... Spectroscopic camera, 5... No. 13 controller, 6... Condensing lens, 7... Imaging lens, 8
...Zydrail, 9...Lens drive device, IO・
...Photodetector, 11...Arithmetic circuit, 12...Storage circuit, 13...Comparison circuit, 14...jl; Control circuit. Agent Patent attorney Tatsuyuki Unuma / Figure 2 Figure r −−−−−−−−'−−−−−−−11 1 ψ jl) 3 1E21 4th figure Shake se θ times dry Mu mata pair y
5E2h Figure 6 Figure 713 (-High angle θ Figure 9 Figure 10 112 Immersion degree C'C')

Claims (1)

[Claims] 1. A combustion flame control method, characterized in that the temperature distribution in the flame is optically measured in a non-contact manner, and the combustion flame is controlled based on the measured temperature distribution. How to control flames. 2. The combustion flame control method according to claim 1, wherein the means for optically measuring the 2° flame is means for spectroscopically analyzing the emission spectrum of .OH in the flame. 3. An optical measuring device that finds the break in the combustion flame, an arithmetic circuit that inputs the results of spectroscopic analysis of the emission spectrum from this measuring device and calculates the temperature distribution, and a flame detector that detects the flame in the optimal combustion state. A storage circuit that stores the temperature distribution inside, a comparison circuit that compares an output from the arithmetic circuit and an output from the storage circuit, and a control circuit that outputs a control signal based on the output from the comparison circuit. A combustion flame control device characterized by: