JP2896529B2 - Combustion diagnostic device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a combustion diagnostic device for diagnosing a combustion state of a flame in a combustion furnace.

[Conventional technology]

In order to prevent pollution, it is desired that combustion devices such as boilers do not generate nitrogen oxides, soot and carbon monoxide. Such a form of combustion forms a flame in which the fuel and air mix appropriately in the combustion furnace, thereby preventing the formation of an extremely high temperature region and the formation of an extremely low temperature region in the combustion furnace. It is necessary not to let them.

Normally, to form such a combustion state, various nitrogen oxide concentration meters (NOx meters), soot concentration meters, and carbon monoxide concentration meters are installed in the flue gas of the combustion exhaust gas, and the detected values of these measuring devices are measured. And adjust the fuel flow rate corresponding to this detection value,
By adjusting the air flow rate, the exhaust gas recirculation flow rate, and the like, the generation of nitrogen oxides, soot, and carbon monoxide was suppressed. Recently, a device for directly detecting the emission spectrum of the flame in the fuel furnace and diagnosing the fuel condition has appeared, and based on the result of the diagnosis, adjustment of the fuel flow rate, adjustment of the air flow rate, adjustment of the exhaust gas recirculation flow rate, and the like. Began to take place.

The conventional combustion diagnostic device based on emission spectrum detection compares the emission spectrum pattern received by the optical probe with the model emission spectrum pattern at the time of optimal combustion stored in the computer, and determines the combustion situation from the degree of the difference. There is one that has been diagnosed (see JP-A-60-159515).

[Problems to be solved by the invention]

However, the combustion diagnostic apparatus based on the detection of the emission spectrum simply compares the emission spectrum pattern received by the optical probe with the model emission spectrum pattern at the time of optimal combustion stored in the computer,
The specific comparison method was not clear. Therefore, assuming that the emission spectrum patterns are simply compared,
It is necessary to store all the model emission spectrum patterns, that is, the spectrum intensities for the sequentially different wavelengths, and it is necessary to store a large number (several tens to several hundreds) of data in the memory. In addition, the detected emission spectrum must be compared for all data, which causes a problem of a long calculation time.

Further, a conventional combustion diagnostic apparatus based on emission spectrum detection has the apparatus configuration shown in FIG. 3, and includes a plurality of optical probes 22 to 27, a plurality of optical fibers 32 to 37, an optical scanner 3
8, mainly composed of a spectroscopic analyzer 41 and a computer 51. One or more optical probes are attached to each burner. The spectroscopic analyzer 41 includes light receiving elements 42 to 44, an optical scanner 48, and an amplifier 45.

However, in the combustion diagnostic device based on the detection of the emission spectrum, the light amount of the emission spectrum received by the optical probe is
Until the photoelectric conversion by the light receiving element, no consideration was given to a significant attenuation.

That is, the attenuation of the light amount mainly occurs in the optical scanners 38 and 48. In the optical scanner 38, a large amount of light is attenuated at two points between the optical fiber 32, 36, or 37 and the movable mirror 40 and between the movable mirror 40 and the optical fiber 46. Optical scanner 48
In the above, between the optical fiber 46 and the moving mirror 50, the moving mirror 50
There is a large amount of light attenuation at two places between the light receiving element 42, 43, and 44. This is because there is a gap between the optical fiber and the movable mirror, and the light is scattered.
Since the attenuation of the light quantity per location is 10 to 30%, if there are four attenuation locations of the light quantity, the light receiving spectrum light quantity from the optical probe attenuates to 65 to 24% before reaching the light receiving element. Will be.

Therefore, in the combustion diagnosis apparatus based on the detection of the emission spectrum, it is necessary to receive a large amount of the emission spectrum with the optical probe, and there is a problem that the apparatus is not economical.

The present invention has been made based on such circumstances, and a first object of the present invention is to perform high-speed and high-accuracy comparison of a received light spectral pattern and a model spectral pattern in a combustion diagnostic device. It is an object of the present invention to provide a combustion diagnosis device that can perform the above.

Further, a second object of the present invention is to provide an economical combustion diagnostic apparatus which has a function equivalent to that of a conventional apparatus and can greatly reduce the apparatus cost.

[Means for solving the problem]

In order to achieve such an object, the present invention basically detects an emission spectrum of a flame in a combustion furnace, compares the detected emission spectrum with a model emission spectrum, and performs combustion diagnosis based on the comparison value. The combustion diagnostic apparatus that performs the above is characterized by comprising means for representing the detected emission spectrum as an approximate expression, and storage means for storing the model emission spectrum as an approximate expression.

Further, in the combustion diagnostic apparatus, the emission spectrum at each position in the combustion furnace is taken out by an optical fiber group, and each emission spectrum from the optical fiber group is sequentially detected by a light receiving element and converted into an electric signal. As means for detecting each emission spectrum from the optical fiber group by a light receiving element, each output end of the optical fiber group and the light receiving element can relatively move, and this movement causes each output end of the optical fiber group to move. The light receiving elements are sequentially arranged to face each other.

[Action]

According to the combustion diagnostic apparatus configured as described above, first, the detected emission spectrum of the flame in the combustion furnace is expressed as an approximate expression, and this approximate expression is compared with an approximate expression of a model emission spectrum stored in advance. , Combustion diagnosis is performed.

For this reason, the amount of information to be stored in the storage means can be extremely reduced as compared with the related art, since the number of conditions for specifying the approximate expression can be reduced.

For example, when the approximate expression to be stored in the storage means can be expressed by a quartic equation, the approximate expression can be specified by five coefficients, so that five coefficient values may be stored.

Then, the detected emission spectrum is also represented by an approximate expression, and the approximate expression is compared with the approximate expression information stored in the storage means, so that the comparison can be performed at a very high speed.

For example, when the detected emission spectrum is represented by a quartic equation, the five coefficients of the quartic equation need only be compared with the five coefficient values stored in the storage means. Only the comparison process is needed.

Further, the diagnostic apparatus according to the present invention, as means for detecting each emission spectrum from the optical fiber group by the light receiving element, allows each output end of the optical fiber group and the light receiving element to relatively move, and by this movement, The light receiving element is arranged to sequentially approach each output end of the fiber group.

For this reason, the optical path between each output end of the optical fiber group and the light receiving element does not become long and the mirror is not interposed between the optical paths as in the related art. The amount can be extremely small.

〔Example〕

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

FIG. 1 shows an example of a combustion apparatus to which an embodiment of a combustion diagnosis apparatus based on emission spectrum detection according to the present invention is applied.

In FIG. 1, burners 12 to 17 are attached to the side wall of the combustion furnace 1, and optical probes 22 to 27 are arranged near each of the burners 12 to 17, respectively. The emission spectrum from the flame from the burners 12 to 17 is detected by the optical probes 22 to 27, and the output is
Through 27 to the spectrometer-side connection end 53.

The spectroscopic analyzer entrance-side connection end 53 serves as an optical fiber mounting base, and itself can be moved up and down in the figure by a servomotor 54.

On the other hand, there is a spectroscopic analyzer 52 disposed close to and opposed to the spectroscopic analyzer side connection end 53, and the optical fiber 32 at the spectroscopic analyzer side connection end 53 is provided in the spectroscopic analyzer 52.
The light receiving elements 42 to 44 are provided so as to face part of the light receiving elements 37 to 37.

Outputs from the light receiving elements 42 to 44 are input to a computer 51 via an amplifier.

As a result, the emission spectra from the flames 2 to 7 are received by the optical probes 22 to 27 and transferred to the connection end (optical fiber mounting base) 53 of the optical fiber through the optical fibers 32 to 37. Then, the light is received by the light receiving elements 42, 43, and 44 arranged facing the optical fiber mounting table 53, and is converted into an electric signal. The light receiving elements 42, 43, 44
It selectively receives only the light amount in a certain wavelength range. Light receiving element 4
The emission spectrum converted into an electric signal by 2, 43, and 44 is further converted into an electric signal that can be calculated by the computer by the amplifier 45, and becomes an input signal of the computer 51. The computer 51 diagnoses the combustion state of the flame in the combustion furnace from the electric signal. The connection end (optical fiber mounting base) 53 of the optical fiber on the spectrometer is moved by the servomotor 54 to relatively change the position of the connection end of the optical fiber on the spectrometer and the light receiving element. The light-receiving elements (42 to 44) are arranged in several to ten and several different detection wavelengths at pitches of several tens to 100 nm. In order to measure the spectrum intensity in a narrow band, a light selective transmissive filter may be provided on the front surface of the light receiving elements (42 to 44).

Further, FIG. 2 shows an example of a detected light emission spectrum pattern of a heavy oil combustion flame that has been processed by a computer in one embodiment of the present invention.

The same spectrum pattern can be obtained as the optical spectrum pattern by using a spectrum analyzer or the like. In the wavelength range of 0.6 to 1.6 μm as shown in FIG.
A spectral pattern having two maxima and one minima is obtained. The maximum value near the wavelength of 1.0 μm indicates the peak of light emission by the soot, and the maximum value near 1.38 μm indicates the peak of light emission of water vapor. 1.1 μm
The local minimum in the vicinity appears due to the narrow range between the emission peaks of the soot and the water vapor (it does not appear in the case of the combustion flame of coal and the combustion flame of oil having a low hydrogen content).

This emission spectrum pattern is replaced with a mathematical expression and displayed using the least squares method or the like. This spectral pattern has two local maxima and one local minima,
It can be represented by a quartic equation (the use of a quintic or higher equation yields a more accurate approximation. Note that the present invention does not specify the order of the equation).

f (χ) = K ₄ · χ ⁴ + K ₃ · ＋ ³ + K ₂ · χ ² + K ₁ · χ ¹ +
K ₀ ... (1) Or, as a formula obtained by differentiating the above formula (1), f ′ (χ) = k · (χ−a) · (χ−b) · (χ−c) = 0 ... (2) or an expression obtained by integrating the above expression (2), f (χ) = ∫k ・ (χ-a) ・ (χ-b) ・ (χ-c) ・ dχ +
K ₀ (3) where f (χ): spectrum intensity, a, c: wavelength at the maximum point, ：: wavelength b: wavelength at the minimum point, Equations (1) and (2) Alternatively, the following equation is established between the above equation and the equation (3).

_{4 · K 4 = k -3 ·} K 3 = k · a (a + b + c) 2 · K 2 = k · (a · b + b · c + c · a) -K 1 = k · a · b · c equation (1) When used, the emission spectrum pattern of FIG. 2 is represented by the following equation:

f (χ) = - 714 · χ 4 +3314 · χ 3 -5714 · χ 2 +434
3 · χ−1263.5 (4) Also, using the equation (3), the emission spectrum pattern of FIG. 2 is expressed by the following equation.

f (χ) = ∫ (−2856) · (χ−a) · (χ−b) · (χ−c) · dχ + K ₀ ...
(5) Therefore, K ₄ = −714, K ₃ = 3314, K ₂ = −5714, K ₁ = 43
43 and K ₀ = 5 pieces of the value of -1263.5 (or a = 1.0, b = 1.1, c
1.38, k = 2857, with K 5 or a value of ₀ = -1263.5), may represent the emission spectrum pattern of Figure 2. For this reason, the emission spectrum pattern output from the spectrometer and the model spectrum pattern stored in the computer memory are also
Each of them can be represented by five values, and these five values need only be stored in the memory.

Therefore, in this combustion diagnostic device, the storage capacity of the internal memory used by the computer can be greatly reduced, and a large-capacity computer is not required. Further, even when comparing the detected emission spectrum patterns, the number of comparison data can be greatly reduced, so that the calculation time can be greatly reduced.

In one embodiment of the present invention, as the flame temperature increases, the spectral intensity increases over the entire wavelength and the wavelength of the maximum value a moves to the shorter wavelength side as the flame temperature increases. Therefore, when the change of the emission spectrum pattern at this time is expressed by using the expression (3), b and c do not change, k and a decrease, and K ₀ increases.

Further, when the thickness of the soot layer in the flame increases, the spectral intensity of the emission spectrum pattern generally increases. Therefore, using equation (3), a, b, c
And k do not change, and K ₀ will increase. Similarly,
When the water vapor layer thickness in the flame is increased, a, b and c does not change, k increases, K ₀ is decreased.

Here, in this specification, the above a, b, c,
The value of k or K ₀ is defined as a coefficient related to the approximate expression.

As described above, by using the equation (3) (or the equations (1) and (2)) to display the change in the spectral pattern, the flame temperature, the soot thickness in the flame, and the water vapor layer thickness are displayed. You can know the change. Since the flame temperature, the thickness of the soot layer and the thickness of the water vapor layer in the flame are closely related to the generation of nitrogen oxides, soot, and carbon monoxide, see the change in the expression of this spectral pattern. With this, combustion diagnosis becomes possible,
It is possible to configure a combustion diagnosis device that does not generate nitrogen oxides and the like.

As another embodiment of the present invention, the emission spectrum pattern may be replaced with a set of a plurality of approximate expressions. That is, this emission spectrum pattern is divided into a plurality of parts, and each of the divided spectrum patterns is replaced with an approximate expression. For example, the second
The spectral pattern shown in the figure is replaced with a set of three quadratic equations having wavelengths a, b, and c as central axes.

The effect of this embodiment is that an approximate expression closer to the emission spectrum pattern can be obtained.

Also, the connection end (optical fiber mounting base) 53 of the optical fiber on the spectrometer is moved to thereby relatively change the position of the connection end of the optical fiber on the spectrometer and the light receiving element of the spectrometer. , Without using an optical scanner,
As in the conventional apparatus, an optical fiber for detecting the emission spectrum can be selected, and the emission spectrum that has been phase-shifted in the optical fiber can be transferred to each light receiving element.

Further, since there is no need to install an optical scanner, the light amount attenuation during the transfer is suppressed, and the light receiving amount of the optical probe can be reduced. That is, the size and simplification of the optical probe and the optical fiber can be reduced. Therefore, the cost of the combustion diagnostic device based on the detection of the emission spectrum can be significantly reduced, and an economical combustion diagnostic device can be provided.

In the present invention, the light quantity attenuation during the transmission of the emission spectrum is one point between the connection end of the optical fiber on the spectrum analysis side and the light receiving device of the spectrum analysis device. 70-90% of the spectrum light amount of the light can reach the light receiving element. On the other hand, in comparison with the conventional combustion diagnostic device based on emission spectrum detection, which can reach only the light receiving element of 24 to 65% of the spectrum light amount of the light received by the optical probe, the present invention shows that the light receiving amount of the light receiving element Will increase by 150-300%. In other words, in the present invention, the amount of spectral light received by the optical probe can be reduced to 1/3 to 2/3 of that of the conventional device. Therefore, the size and simplification of the optical probe and the optical fiber can be reduced, and the device cost of the combustion diagnostic device by detecting the emission spectrum can be greatly reduced.

The number of optical probes installed in each burner is not limited to one for each burner as shown in FIG. 1, but is preferably set to a plurality. This is because the more the number of installed optical probes, the more accurate the combustion diagnostic device can be configured. In a large combustion furnace, for example, in a thermal power plant, dozens of burners are installed. Therefore, in this large combustion furnace, several tens to one hundred and several tens of optical probes are installed. Emission spectra received by several tens to one hundred and several tens of optical probes are respectively transferred to the optical fiber-side connection end of the optical fiber by the optical fiber.

Thereby, several tens to one hundred and several tens of optical fibers are attached to the connection end (optical fiber attachment base) of the optical fiber on the spectrometer side.

The number of light receiving elements is not limited to three as shown in FIG. 1, but is preferably several to dozens.
As a result, a combustion diagnostic device with higher accuracy can be configured. The light receiving element has sensitivity characteristics depending on the wavelength. Therefore, when a plurality of light receiving elements having different sensitivity regions are selected and used, the emission spectrum characteristics can be measured. If an optical filter is provided in front of the light receiving element, it becomes possible to measure the spectrum intensity in a narrow band wavelength range. When a large number of light receiving elements with an optical filter are used, it is possible to detect emission spectrum characteristics more strictly.

The inventors installed 48 optical fibers in a straight line at a pitch of 10 mm at the connection end (optical fiber mounting base) of the optical multi-fiber on the spectrometer. In addition, eight light receiving elements were installed on a straight line at a pitch of 40 mm facing the optical fiber.
450n each so as to be in contact with the front face of this light receiving element
Optical filters of m, 520 nm, 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm and 1600 nm were installed. 450nm, 520nm, 600nm, 800nm, 10
For the light receiving element equipped with a 00 nm optical filter, use a silicon photodiode suitable for visible light detection.
A PbS photoconductive element suitable for detecting infrared light was used as a light receiving element equipped with an optical filter of 1,400 nm and 1600 nm.
The gap between the connection end of the optical fiber on the spectrometer side and the optical filter was set to 1 mm or less. And
The connection end of the optical fiber on the side of the spectrometer was slid by 10 mm by a servomotor. As a result of measuring the decay rate of the amount of light for 48 systems from the optical probe to the light receiving element, it was within 15% excluding the influence of the attenuation in the optical filter.

Further, as another embodiment of the present invention, when the positions of the connection end (optical fiber mounting base) 53 of the optical fiber and the light receiving elements 42, 43 and 44 of the spectral analysis device are relatively changed, What is made to be the connection end 53 of the optical fiber on the spectrometer side. When the light receiving element is moved in one embodiment of the combustion diagnostic apparatus based on the emission spectrum detection according to the present invention shown in FIG. 1, a noise signal is generated in the electric wiring connecting the light receiving element due to a change in an electric field and a magnetic field. Then, there arises a problem that a noise signal is added to the electrical conversion signal of the emission spectrum. On the other hand, even if the connection end 53 of the optical fiber on the spectrometer side moves, no noise signal is generated.

The effect of this embodiment is that it is possible to select an optical fiber for detecting the emission spectrum while suppressing the noise signal from entering the electric signal conversion of the emission spectrum. In addition, the occurrence of noise due to the movement of the optical fiber is caused when light is dissipated from the peripheral surface of the optical fiber when the optical fiber is extremely bent, so that the optical spectrum is disturbed.
In a general use without applying an external force, no light is dissipated because the optical fiber is covered with the cladding layer.

The connection end of the optical fiber on the side of the spectrometer and the light-receiving element of the spectrometer are arranged on the two facing plates on the circumference of the same radius, and the optical fiber mounting plate is rotated. Even if it does, the same effect as the arrangement on the straight line shown in FIG. 1 can be obtained.

〔The invention's effect〕

According to the first invention (the invention described in claim (1)), the number of data of one spectrum pattern is greatly reduced from several tens to several hundreds to several to several tens in order to replace an emission spectrum pattern with an approximate expression. Can be reduced. For this reason, the storage means used in the combustion diagnosis apparatus based on the detection of the emission spectrum does not need to have a large capacity. Further, even in the case of comparing and evaluating the detected emission spectrum pattern and the model spectrum pattern in the storage means, the number of comparison data can be greatly reduced, so that the calculation time can be greatly reduced. Therefore, an effect that a simple and highly accurate combustion diagnosis device can be provided is obtained.

Next, according to the second invention (the invention according to claim (4)), the amount of light received by the optical probe can be reduced by reducing the attenuation of the amount of light during the transfer of the flame emission spectrum from the optical probe to the light receiving element. Thus, the size and simplification of the optical probe and the optical fiber can be reduced. Therefore, the cost of the combustion diagnostic device based on the detection of the emission spectrum can be significantly reduced, and an economical combustion diagnostic device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a combustion apparatus to which an embodiment of a combustion diagnosis apparatus based on emission spectrum detection according to the present invention is applied.
FIG. 2 is a diagram showing an example of a detected emission spectrum pattern,
FIG. 3 is a diagram showing a configuration of a conventional combustion diagnostic apparatus based on detection of a flame emission spectrum in a combustion furnace. 1 Combustion furnace 2-7 Flame 12-17 Burner 22-27 Optical probe 32-37 Optical fiber 42-44 Light receiving element 45 Amplifier 51 Computer 52 Spectroscopic analyzer 53: Connection end of optical fiber on the spectrometer (optical fiber mount) 54: Servo motor 60: Flue

──────────────────────────────────────────────────続 き Continuation of the front page (72) Koji Yamamoto, Inventor 6-9 Takara-cho, Kure City, Hiroshima Pref. Inside the Kure Plant of Babcock Hitachi Ltd. (56) References 1-197631 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F23N 5/08 G01J 1/02 G01J 3/28-3/443

Claims (5)

(57) [Claims] 1. An emission spectrum of a flame in a combustion furnace is detected.
In a combustion diagnostic apparatus that compares the detected emission spectrum with a model emission spectrum and performs combustion diagnosis based on the comparison value, a unit that represents the detected emission spectrum as an approximate expression, and stores the model emission spectrum as an approximate expression. A combustion diagnostic apparatus comprising: a storage unit for storing the information. 2. The combustion diagnostic apparatus according to claim 1, wherein each of the approximate expressions of the detected emission spectrum and the model emission spectrum is a set of approximate expressions divided by a wavelength range. . 3. A method according to claim 1, wherein the comparison between the detected emission spectrum and the model emission spectrum is performed using coefficients related to the respective approximate expressions. Combustion diagnostic device. 4. A combustion diagnostic apparatus comprising means for extracting an emission spectrum at each position in a combustion furnace with an optical fiber group, sequentially detecting each emission spectrum from the optical fiber group with a light receiving element, and converting the spectrum into an electric signal. In the above, each output end of the optical fiber group and the light receiving element can relatively move as a means for detecting each emission spectrum from the optical fiber group by a light receiving element, and this movement allows each output of the optical fiber group to be detected. A combustion diagnostic apparatus, wherein the light receiving elements are sequentially brought close to the ends. 5. The combustion diagnostic apparatus according to claim 4, wherein the light receiving element is fixed, and each output end of the optical fiber group moves.