JP3083633B2 - Combustion diagnostic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion diagnostic device,
In particular, the present invention relates to a combustion diagnostic apparatus for diagnosing the combustion state of each burner flame in a combustion furnace provided with a burner for recirculating exhaust gas for the purpose of low NOx combustion or the like, based on a flame emission spectrum.

[0002]

2. Description of the Related Art For the purpose of preventing pollution, it is necessary not to generate nitrogen oxides, soot and carbon monoxide in a combustion furnace such as a boiler. In order to form such a combustion state, the fuel flow rate, the air flow rate, the mixed state of fuel and air, and the like in each burner are maintained in a predetermined state, so that an extremely high temperature region and an extremely low temperature It is necessary not to form a temperature region. As one of the measuring instruments used for forming such a combustion state, there is a device that detects a flame emission spectrum and diagnoses the combustion state from the spectrum characteristic (hereinafter, referred to as a combustion diagnosis device).

[0003] However, in this combustion diagnosis apparatus, the flame emission spectrum fluctuates due to the fluctuation of the flame and the mutual interference of the burner flame, making the combustion diagnosis difficult. Many conventional combustion diagnostic devices do not give sufficient consideration to fluctuations in the flame emission spectrum,
For this reason, there has been a problem that the combustion diagnosis accuracy is reduced and a diagnosis time is long.

To cope with this problem of emission spectrum variation, Japanese Patent Application No. 50252/1991 focuses on the fact that spectrum variation relates to variations in fuel flow rate and air flow rate. Installed and standardize the measured flame emission spectrum based on each flow rate,
Then, a method of applying the standardized flame emission spectrum to combustion diagnosis logic was proposed.

[0005] Although this method shortens the diagnosis time, it requires the installation of a flow meter for each system, which increases the equipment cost, and the maintenance of the flow meter consumes much labor. Problem.

[0006]

The above prior arts involve problems such as a decrease in the accuracy of combustion diagnosis and a problem of a long diagnosis time, an increase in equipment costs due to the installation of various flow meters, and an increase in maintenance labor for these meters. Had a problem. It is an object of the present invention to provide a combustion diagnostic device that can improve the accuracy of combustion diagnosis and reduce the diagnosis time without increasing the cost of the device and the maintenance labor.

[0007]

To achieve the above object, a first invention of the present application is a flame detecting means arranged for a flame, and a spectral analysis means for inputting a light detection signal from the flame detecting means. And data analysis means for inputting a signal from the spectrum analysis means and performing arithmetic processing, based on the spectrum intensity for each wavelength determined by the spectrum analysis means, the soot emission degree during normal combustion by the analysis means, The present invention relates to a combustion diagnostic apparatus characterized in that reference data of water vapor absorbance and data of soot light emission and water vapor absorbance at the time of detection to be diagnosed for combustion are created and the combustion state of the flame is diagnosed based on the data.

According to a second aspect of the present invention, there is provided a flame detecting means arranged for a flame, a spectral analyzing means for inputting a light detection signal from the flame detecting means, and a signal input from the spectral analyzing means for calculation. And a data analyzing means for processing, based on the spectral intensity for each wavelength obtained by the spectral analyzing means, by the analyzing means, soot luminescence during normal combustion and reference data of carbon dioxide absorbance and at the time of detection to perform combustion diagnosis The present invention relates to a combustion diagnostic apparatus characterized in that data on soot luminous intensity and carbon dioxide absorbance are created and the combustion state of a flame is diagnosed based on the data.

According to a third aspect of the present invention, there is provided a flame detecting means arranged for a flame, a spectral analyzing means for inputting a light detection signal from the flame detecting means, and a signal input from the spectral analyzing means for calculation. A data analyzing means for processing, based on the spectral intensity for each wavelength obtained by the spectral analyzing means, by the analyzing means, the value of soot luminescence and water vapor absorbance during normal combustion, the fluctuation range, and the time of detection for combustion diagnosis The value and / or fluctuation range of the soot luminous intensity and water vapor absorbance of the soot are determined, and thereby any one or more of a fuel flow rate, an air flow rate, and a recirculation flue gas flow rate is diagnosed. The present invention relates to a combustion diagnostic device.

According to a fourth aspect of the present invention, there is provided a flame detecting means arranged for a flame, a spectrum analyzer for inputting a light detection signal from the flame detecting means, and a signal input from the spectrum analyzing means for calculation. Data analyzing means for processing, based on the spectrum intensity for each wavelength obtained by the spectral analyzing means, the soot luminous intensity and carbon dioxide absorbance value during normal combustion, the fluctuation range and the detection to be diagnosed by combustion by the analyzing means. Determining the value and / or fluctuation range of the soot luminosity and the carbon dioxide absorbance at the time, and diagnosing at least one of the fuel flow rate, the air flow rate, and the recirculation flue gas flow rate based on the value. The present invention relates to a combustion diagnostic device characterized by the following.

[0011]

The soot emission characteristic and the water vapor absorption characteristic of the flame emission spectrum are detected for the normal operation combustion and the operation for which combustion diagnosis is to be performed, and the above two cases are compared. From the relationship between the various combustion adjustments and the flame emission spectrum behavior, it is possible to know the change in the fuel flow rate, the air flow rate, the recirculation exhaust gas flow rate, or the swirl force of the air / recirculation exhaust gas mixed gas.

[0012]

【Example】

i) Overall Configuration FIG. 1 shows an example of a combustion diagnosis apparatus to which the combustion diagnosis method is applied. This combustion diagnostic apparatus mainly includes a plurality of optical probes 1, a plurality of relay optical fibers 2, an optical channel selector 3, a spectroscopic analyzer 4, and a data analyzer 5. The optical probe 1 has one or more visual fields.

Thus, the light from the flame 10 is received by each optical probe 1 and transferred to the optical channel selector 3 through the relay optical fiber 2. The relay optical fiber 2 to be analyzed is selected by the optical channel selector 3,
The flame light transferred by the relay optical fiber 2 is spectrally analyzed by the spectroscopic analyzer 4 and then converted into an electric signal. The data analyzer 5 specifies the combustion state at this time based on the spectrum analysis result.

FIG. 2 shows an example of the emission spectrum of a heavy oil combustion flame. Optical transmission loss of relay optical fiber is small.
In the wavelength range of 4 to 1.6 μm, an emission spectrum of soot (carbonaceous particles) was observed on the longer wavelength side than 0.7 μm, and 1.1 μm and 1.4 μm on this emission spectrum.
Near m, a decrease in the spectrum intensity due to the absorption of water vapor is observed.

From the emission characteristics of the soot, the flame temperature can be known by using the relationship of Planck's radiation law. Planck's radiation law means that the relationship between the radiation wavelength and the radiation intensity at a certain temperature is determined as shown in FIG. Therefore, to determine the temperature of the flame, the relationship between the wavelength and the intensity may be determined. Since it is difficult to measure over the entire wavelength range, high-temperature ones are usually measured in the visible-near-infrared light wavelength range having a wavelength λ <1 μm or less. It is said that the flame emits light from soot (soot or carbon) in this wavelength range. The flame temperature is usually in the range of 1200 ° K to 2000 ° K, and in this temperature range, the intensity in the λ = 0.8 to 1.0 μm wavelength region almost linearly depends on the wavelength, as estimated from FIG. Therefore, the temperature can be calculated from the slope of the line connecting the measurement points only by measuring the intensity at the wavelengths at two or three points. Although there is no problem in principle even if the calculation is performed at λ <0.8 μm or less, the shorter the wavelength, the lower the intensity, so that the measurement becomes difficult. In the present invention, the slope value of the spectrum intensity in the wavelength range of 0.8 to 1.0 μm is called soot luminous intensity. The method of measuring the temperature is as follows. When the spectrum intensity at arbitrary plural wavelengths, for example, the spectrum intensity at 0.8 μm and the spectrum intensity at 1.0 μm are experimentally measured in advance, and the relationship between the measured value and the temperature is obtained, the relationship shown in FIG. Is obtained. Using this relationship, it is possible to convert the flame temperature from the spectral characteristics.

The absorption of water vapor is a phenomenon caused by the flow of recirculated flue gas containing water vapor between the flame and the optical probe. This decrease in spectral intensity increases as the concentration and flow rate of water vapor increase. In a boiler of a thermal power plant, the amount of air and the amount of recirculated gas corresponding to each load are adjusted, and when the load is constant, the air flow rate +
The recirculation gas flow rate is controlled so that the total flow rate of the entire boiler is constant, but control for individual burners is not performed. For this reason, although not strict, for each burner on average, as the air flow rate increases, the recirculation exhaust gas flow rate decreases. From the change in the decrease in the spectral intensity (= the decrease in the spectral intensity due to the absorption of water vapor), it is possible to know the change in the air flow rate, the flow rate of the recirculated flue gas, or the change in the mixing ratio of the combustion air and the recirculated flue gas. Is referred to as water vapor absorbance. In practice, the area of the dent, which is the amount of decrease in the spectrum intensity near 1.4 μm, is obtained).

FIG. 3 shows the normal combustion state of the flame in the heavy oil combustion (the optimum combustion state in which the combustion adjustment is completed in each load zone, that is, the combustion state optimized by the operation instructor during the test operation adjustment). ) And when the average value of only the fuel flow rate is reduced by 20% from the normal combustion state (therefore, the air flow rate and the recirculated flue gas flow rate remain at the flow rates optimized by the operation instructor). 6 shows the relationship between the fluctuation states of the absorbance. Constant load (fuel flow,
Even when operating at a constant air flow rate and recirculated flue gas flow rate throughout the boiler), the air and recirculated flue gas flow rates vary for each burner due to the mutual interference of the burners. For example, as the air or recirculated flue gas flow of the target burner increases, the air or recirculated flue gas flow of the adjacent burner decreases. Therefore, when observing the flame emission spectrum, because of the burner mutual interference,
Fluctuations in water vapor absorbance and soot luminescence are observed as shown in FIG. FIG. 4 shows a relationship between the soot luminous intensity and the fluctuation state of the water vapor absorbance at the time of normal combustion and when the average value of the air flow rate is increased by 15% from that at the time of normal combustion.

As can be seen from FIGS. 3 and 4, the soot luminous intensity and water vapor absorbance in the flame luminous spectrum show the normal combustion and the abnormal combustion in which the fuel flow rate, air flow rate and the like (the average value) have changed. It fluctuates within a certain range. At this time, there is an inverse relationship that the water vapor absorbance increases as the soot luminescence decreases. This phenomenon is
An increase in recirculated flue gas, such as an increase in water vapor absorbance, is believed to indicate slow combustion, lower flame temperature, and lower soot luminescence.

When the air flow rate increases, the fluctuation area (X) of the soot luminous intensity does not change, but the fluctuation area of the water vapor absorbance decreases (the fluctuation width decreases from Y ₁ to Y ₂ , and the absorbance itself also changes at a low level). (Transition to the domain). When the fuel flow rate decreases, both the soot luminous intensity fluctuation region and the water vapor absorbance fluctuation region decrease (shift to a low fluctuation region). Table 1 summarizes changes in the soot luminous intensity and water vapor absorbance fluctuation region when the fuel flow rate and the air flow rate change as described above.

[0020]

[Table 1]

In Table 1, an increase in the power generation load means that the fuel flow rate increases, and accordingly, the combustion air flow rate and the recirculated flue gas flow rate increase. Although the embodiment for heavy oil combustion flame has been described above, the combustion diagnosis in the combustion flame for gas fuel detects the soot luminescence and water vapor absorbance of the flame emission spectrum in the same manner as in the case of oil combustion flame. The same can be done.

However, in the case of a solid fuel such as coal (for example, pulverized coal), a change in water vapor absorbance does not appear significantly because the proportion of water vapor contained in the combustion product is small. Therefore, when the absorbance of carbon dioxide is used instead of the water vapor absorbance, combustion diagnosis can be performed in the same manner as in the case of oil combustion flame. In this case, since the absorption wavelengths of carbon dioxide are at 2.7 μm and 4.3 μm, the amount of decrease in the intensity of the spectrum and the area of the dent are determined around this wavelength. Since the absorbance of carbon dioxide cannot be measured when the light passes through an optical fiber, it is necessary to directly send the light detected by an optical probe to a spectrometer without passing through a relay optical fiber for analysis.

In carrying out the present invention, as shown in FIG. 3, a relational data area (normal data area) between the soot luminous intensity and the water vapor absorbance of a flame during normal combustion is previously experimentally obtained (experimental). Using this as a reference value, detection relation data of soot luminous intensity and water vapor absorbance of a burner flame during actual operation (in FIG. 3, the data area of a data area where fuel is reduced by 20%) All the data or a part of the data is obtained, and considering the relationship between the spectral behaviors shown in Table 1, the two data are compared to diagnose the burner combustion state. For example,
Comparing the reference value and the detection value, the burner in which the soot emission characteristic does not show a change and the flame behavior in which the water vapor absorbance is small is obtained is diagnosed that the air flow rate is increasing,
In such a case, it is estimated that a large amount of nitrogen oxide is generated in the combustion gas.

According to the present invention, when the reference values of the soot luminescence and the water vapor absorbance (carbon dioxide absorbance) are measured in advance during normal operation, the soot luminescence and the water vapor absorbance (carbon dioxide absorbance) during the operation to be diagnosed are determined. Even if the data of the entire fluctuation range of the absorbance is not obtained, the combustion diagnosis can also be performed by obtaining a part of the data and comparing it with the reference value, so that the diagnosis time can be shortened.

[0025]

According to the present invention, there is a problem that the accuracy of combustion diagnosis is reduced and a diagnosis time is long, which is a problem with the conventional combustion diagnosis device, or the cost of the device is increased due to the installation of various flow meters, and the cost for these devices is reduced. Problems such as an increase in maintenance labor are eliminated, and it is possible to provide combustion diagnosis software that can improve the accuracy of combustion diagnosis and reduce the diagnosis time without increasing the cost of the apparatus and the maintenance labor.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a combustion diagnosis system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an emission spectrum of an oil combustion flame.

FIG.

FIG. 4 is a diagram showing measured values of soot luminescence and water vapor absorbance in a flame emission spectrum and the relationship between the two.

FIG. 5 is a diagram showing Planck's radiation law.

FIG. 6 is a relationship diagram for obtaining a flame temperature from measurement of spectrum intensity.

[Explanation of symbols]

1 optical probe, 2 relay optical fiber, 3 optical channel selector, 4 spectral analyzer, 5 data analyzer.

Continuation of the front page (56) References JP-A-62-276326 (JP, A) JP-A-4-270820 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23N 5 / 08 F23M 11/04 104

Claims (4)

(57) [Claims] 1. Flame detecting means arranged for a flame, spectral analyzing means for inputting a light detection signal from the flame detecting means, and data analysis for inputting and processing a signal from the spectral analyzing means. Means, based on the spectral intensity for each wavelength determined by the spectral analysis means, by the analysis means, soot luminescence during normal combustion and reference data of water vapor absorbance and soot luminescence and water vapor at the time of detection for combustion diagnosis A combustion diagnostic apparatus characterized in that data on absorbance is created and the combustion state of the flame is diagnosed based on the data. 2. Flame detecting means arranged for a flame, spectral analyzing means for inputting a light detection signal from the flame detecting means, and data analysis for inputting a signal from the spectral analyzing means and performing arithmetic processing. With means, based on the spectral intensity for each wavelength determined by the spectral analysis means, by the analysis means, soot luminescence at normal combustion and reference data of carbon dioxide absorbance and soot luminescence at the time of detection for combustion diagnosis and A combustion diagnostic apparatus characterized in that data of carbon dioxide absorbance is created and the combustion state of the flame is diagnosed based on the data. 3. A flame detecting means arranged for a flame, a spectral analyzing means for inputting a light detection signal from the flame detecting means, and a data analysis for inputting a signal from the spectral analyzing means and performing arithmetic processing. Means, based on the spectral intensity for each wavelength determined by the spectroscopic analysis means, the analysis means, soot luminescence during normal combustion and the value and variation of water vapor absorbance and soot luminescence at the time of detection to be diagnosed combustion A combustion diagnostic apparatus characterized by determining a value of a water vapor absorbance and / or a fluctuation range, and diagnosing at least one of a fuel flow rate, an air flow rate, and a recirculation flue gas flow rate. . 4. A flame detecting means arranged for a flame, a spectroscopic analyzer for inputting a light detection signal from the flame detecting means, and a data analysis for inputting a signal from the spectroscopic analyzing means and performing arithmetic processing. Means, based on the spectral intensity for each wavelength determined by the spectroscopic analysis means, the soot emission at the time of normal combustion, soot emission and carbon dioxide absorbance values and fluctuation range and soot emission at the time of detection to be diagnosed by combustion And a value and / or a fluctuation range of the carbon dioxide absorbance are obtained, and a state of at least one of a fuel flow rate, an air flow rate, and a recirculation flue gas flow rate is diagnosed based on the determined value. Combustion diagnostic device.