CN107064113B - System and method for detecting pulverized coal combustion quality of burner by using optical fiber - Google Patents
System and method for detecting pulverized coal combustion quality of burner by using optical fiber Download PDFInfo
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- CN107064113B CN107064113B CN201710442165.8A CN201710442165A CN107064113B CN 107064113 B CN107064113 B CN 107064113B CN 201710442165 A CN201710442165 A CN 201710442165A CN 107064113 B CN107064113 B CN 107064113B
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
- G01N21/716—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited by measuring the radiation emitted by a test object treated by combustion gases for investigating the composition of gas mixtures
Abstract
The invention discloses a system and a method for realizing pulverized coal combustion quality detection of a burner by using optical fibers, wherein the system comprises an optical fiber sensor, a processor and a controller, wherein the optical fiber sensor is arranged at a burner port and is configured to collect flame light signals in the burner and transmit the flame light signals to the processor through a photoelectric converter; the processor is configured to sample and perform spectrum analysis on the signal converted by the photoelectric converter, so as to separate the radiation intensity in the signal and the flicker intensity of flame at each frequency point; calculating the corrected background radiation intensity by correcting the shielding effect of the unburned particles on the background; the combustion quality of the burner coal dust is described by the corrected background radiation intensity.
Description
Technical Field
The invention belongs to the field of thermal power generation, and particularly relates to a system and a method for detecting the combustion quality of pulverized coal of a burner by using optical fibers.
Background
In the field of thermal power generation, pulverized coal combustion power generation is the main form. Coal is pulverized into powder by a coal pulverizer and then is sent into a hearth for combustion through a pipeline (powder pipe) together with pulverized coal through hot air. The requirements of the boiler on combustion stability, economy, environmental protection indexes and the like all depend on the regulation and control of coal quality and the proportion of wind coal. The evaluation of coal quality mainly depends on chemical analysis and sampling inspection. The accurate control of the air-coal ratio is always a long-standing problem in the field of boiler combustion. The existing method for controlling the air-coal ratio mainly regulates and controls the rotating speed of a powder feeder, and the rotating speed and the coal feeding quantity of the powder feeder are nonlinear, so that the effect of an input air-coal online system is not ideal. The main reason for this is that the measurement and control of the coal dust concentration in the air-powder mixture is problematic. Concentration measurement is inaccurate, and control is not always mentioned, and concentration measurement is a prerequisite for realizing accurate control. At present, the concentration measurement generally adopts a charge principle method, namely, the coal powder is utilized to have positive charge, and the higher the coal powder concentration is, the higher the voltage on the induction electrode is.
The present thermal generator set basically realizes AGC control, the AGC is automatic power generation control, the generator set automatically tracks and responds to a load instruction from a power grid dispatching system, and the whole generator set is equivalent to an automatic following actuator. Thus, the nature of AGC control is energy balance control, and genset energy is derived from the heat generated by furnace combustion. Therefore, the monitoring of the heating value of the furnace is the most direct and effective monitoring. However, at present, the measurement of the concentration of the pulverized coal and the on-line system of the wind powder are only an indirect measurement and regulation of the energy at the supply side, and a monitoring means for monitoring and regulating the combustion condition of a hearth most directly is lacked.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a system for realizing the pulverized coal combustion quality detection of a burner by using an optical fiber, which directly performs photoelectric conversion on an optical fiber signal taking the burner as an observation point, respectively separates the radiation intensity of a reaction observation point and the flicker intensity of flame of unburned particulate matters by analyzing the converted signal, and calculates the corrected background radiation intensity by correcting the shielding effect of the unburned particulate matters on the background; the combustion quality of the burner coal dust is described by the corrected background radiation intensity.
The invention discloses a system for realizing the pulverized coal combustion quality detection of a burner by using optical fibers, which comprises:
the optical fiber sensor is arranged at the burner port and is configured to collect flame optical signals in the burner and transmit the flame optical signals to the processor through the photoelectric converter;
the processor is configured to sample and perform spectrum analysis on the signal converted by the photoelectric converter, so as to separate the radiation intensity in the signal and the flicker intensity of flame at each frequency point; calculating the corrected background radiation intensity by correcting the shielding effect of the unburned particles on the background; describing the combustion quality of the pulverized coal of the burner by using the corrected background radiation intensity;
in the process of calculating the corrected background radiation intensity, firstly, the flicker intensity of flame at each frequency point is utilized to calculate the combustion degree of the pulverized coal for describing the shielding degree; and correcting the background radiation intensity by using the combustion degree of the pulverized coal, wherein the corrected background radiation intensity is the ratio of the radiation intensity to the combustion degree of the pulverized coal.
Further, the photoelectric converter comprises an integrated operational amplifier and a photoresistor connected with the integrated operational amplifier in parallel, and the negative feedback voltage of the negative phase end input of the integrated operational amplifier and the photoresistor is superposed and then output.
The photoelectric converter adopts undistorted resistance value-voltage conversion to the photoresistor, the input signal is superposed with the negative feedback voltage of the photoresistor at the inverting input end of the integrated operational amplifier and then output, and the output voltage and the infrared intensity (the resistance value of the photoresistor is inversely proportional to the infrared intensity) are in an inversely proportional relation.
Further, the processor is configured to sample and spectrally analyze the signal converted by the photoelectric converter using a least squares algorithm.
The method has high time-frequency analysis precision, can accurately identify the frequency spectrum characteristics of the signal, can accurately depict the position and the boundary of the reservoir and can further improve the precision of reservoir prediction.
Further, the processor is connected with the monitoring host through a bus.
The invention also provides a detection method for realizing the system for detecting the combustion quality of the pulverized coal of the burner by using the optical fiber.
The invention discloses a detection method for realizing a system for detecting the combustion quality of pulverized coal of a burner by using optical fibers, which comprises the following steps:
the optical fiber sensor collects flame optical signals in the burner and transmits the flame optical signals to the processor through the photoelectric converter;
the processor samples and performs spectrum analysis on the signals converted by the photoelectric converter, so as to separate the radiation intensity in the signals and the flicker intensity of flames at each frequency point; calculating the corrected background radiation intensity by correcting the shielding effect of the unburned particles on the background; describing the combustion quality of the pulverized coal of the burner by using the corrected background radiation intensity;
in the process of calculating the corrected background radiation intensity, firstly, the flicker intensity of flame at each frequency point is utilized to calculate the combustion degree of the pulverized coal for describing the shielding degree; and correcting the background radiation intensity by using the combustion degree of the pulverized coal, wherein the corrected background radiation intensity is the ratio of the radiation intensity to the combustion degree of the pulverized coal.
Further, sampling and spectrum analysis are carried out on the signals converted by the photoelectric converter by adopting a least square algorithm.
Further, the specific process of sampling and spectrum analysis of the signal converted by the photoelectric converter by using the least square algorithm is as follows:
determining the frequency and sampling period of the signal converted by the photoelectric converter according to Shennong sampling theory;
constructing a least square filter according to a least square algorithm;
and filtering the signal converted by the photoelectric converter according to a least square filter to obtain a direct current component of the signal converted by the photoelectric converter and harmonic amplitudes of each frequency point, which are respectively recorded as the radiation intensity and the flicker intensity of the flame at each frequency point.
Furthermore, the combustion degree of the coal dust is the ratio of the difference between the maximum average flicker intensity of the coal dust and the average flicker intensity of all the coal dust to the maximum average flicker intensity of the coal dust.
Further, when the flicker intensity of each frequency point of the pulverized coal reaches the maximum, the combustion degree of the pulverized coal is the minimum, which indicates that the shielding is serious.
Further, the method further comprises: the processor also transmits the combustion quality of the pulverized coal of the burner to the monitoring host through the bus for real-time monitoring.
Compared with the prior art, the invention has the beneficial effects that:
(1) in the pulverized coal combustion quality detection method provided by the invention, the corrected background radiation intensity is calculated by correcting the shielding effect of unburned particulate matters on the background; the combustion quality of the pulverized coal of the burner is described by using the corrected background radiation intensity, so that a theoretical basis is provided for flame state detection, combustion quality detection and the like;
(2) the pulverized coal combustion quality detection method provided by the invention realizes the quantitative evaluation index of the pulverized coal combustion degree;
(3) the combustion quality detection method provided by the invention has a direct help effect on improving the refined combustion adjustment level and the environmental protection level of the boiler in the current thermal power generation field, fills the blank of the field, and has great economic benefit and social benefit.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a schematic structural diagram of a system for detecting the combustion quality of pulverized coal in a burner by using optical fibers according to the present invention;
FIG. 2 is a schematic diagram of the structure of the photoelectric converter of the present invention;
FIG. 3 is a picture of boiler combustion monitoring implemented in accordance with the present invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Fig. 1 is a schematic structural diagram of a system for detecting the combustion quality of pulverized coal of a burner by using an optical fiber according to the present invention.
As shown in fig. 1, the system for detecting the combustion quality of pulverized coal by a burner using an optical fiber according to the present invention includes:
the optical fiber sensor is arranged at the burner port and is configured to collect flame optical signals in the burner and transmit the flame optical signals to the processor through the photoelectric converter;
the processor is configured to sample and perform spectrum analysis on the signal converted by the photoelectric converter, so as to separate the radiation intensity in the signal and the flicker intensity of flame at each frequency point; calculating the corrected background radiation intensity by correcting the shielding effect of the unburned particles on the background; describing the combustion quality of the pulverized coal of the burner by using the corrected background radiation intensity;
in the process of calculating the corrected background radiation intensity, firstly, the flicker intensity of flame at each frequency point is utilized to calculate the combustion degree of the pulverized coal for describing the shielding degree; and correcting the background radiation intensity by using the combustion degree of the pulverized coal, wherein the corrected background radiation intensity is the ratio of the radiation intensity to the combustion degree of the pulverized coal.
Due to the shielding effect of the pulverized coal, the radiation intensity of the separated signal, that is, the direct current component of the flame light signal is actually the radiation intensity of the observation point, but not the background radiation intensity, and the background radiation intensity must be corrected according to the shielding rate of the pulverized coal to the background light.
The sizes and the flicker characteristics of the flame on the fundamental wave point and each subharmonic frequency point reflect the motion characteristics of particles in a hearth wind field, the more obvious the characteristics are, the larger the concentration of the particles is, the more serious the shielding of the background light is caused if the concentration is higher, and therefore, the characteristics negatively contribute to the background light.
The degree of occlusion is described by the degree of pulverized coal combustion E as follows:
wherein, U
max-maximum average scintillation intensity. When each flicker intensity reaches the maximum, E is minimum (tends to be 0), indicating that the shielding is serious, and when each flicker intensity is small, E is large (tends to be 1), indicating that the shielding effect is small.
Therefore, the real background intensity U should be inversely corrected according to the magnitude of E. The corrected background intensity U is:
the above formula comprehensively describes the radiation intensity U directly observed by an observation point
0The relationship between the degree of combustion E of the pulverized coal and the radiation intensity U of the burnout front of the pulverized coal also describes and represents the combustion quality of the burner.
As shown in fig. 2, the photoelectric converter includes an integrated operational amplifier and a photoresistor connected in parallel with the integrated operational amplifier, and the inverting terminal input of the integrated operational amplifier is superposed with the negative feedback voltage of the photoresistor and then output.
The photoelectric converter adopts undistorted resistance value-voltage conversion to the photoresistor, the input signal is superposed with the negative feedback voltage of the photoresistor at the inverting input end of the integrated operational amplifier and then output, and the output voltage and the infrared intensity (the resistance value of the photoresistor is inversely proportional to the infrared intensity) are in an inversely proportional relation.
Wherein the processor is further configured to sample and spectrally analyze the converted signal from the photoelectric converter using a least squares algorithm.
Specifically, the specific process of sampling and spectrum analysis of the signal converted by the photoelectric converter by using the least square algorithm is as follows:
the method comprises the following steps: determining the frequency and sampling period of the signal converted by the photoelectric converter according to Shennong sampling theory;
according to the fourier function theory, any one of the functions can be expressed as the following fourier function with a fundamental frequency ω:
wherein, U
0-a direct current component; λ -the dc component attenuation coefficient; u shape
k-the amplitude of the kth harmonic; ω -angular frequency of the fundamental current or voltage; theta
k-initial phase angle of the k-th harmonic. k is 1,2, …, M.
According to shennong's sampling theory, as long as the sampling frequency f is more than twice the signal frequency, a continuous function can be recovered from discrete sampling samples, including each periodic function component sin (k ω t) in u (t), and the like. Here, for example, if the highest recognizable frequency is 119Hz, the sampling frequency f must be 238Hz or more, and in the fast fourier algorithm, the sampling frequency f is generally ten times or more of the signal frequency, and for example, to recover a 119Hz signal, the sampling frequency generally needs a frequency of 1190Hz or more.
Step two: constructing a least square filter according to a least square algorithm;
the spectrum analysis is to obtain U finally by sampling the signal sequence
0、λ、U
k、θ
k. Currently, there are two methods to achieve this, the fourier algorithm and the least squares algorithm. The invention adopts a least square algorithm. For this purpose, the fourier function is first expanded and simplified.
Converting U in Fourier function
0e
-λtExpanding according to Taylor series, taking the first two terms, then:
U
0e
-λt≈U
0-U
0λt
sin (k ω t + θ)
k) Expanding according to a trigonometric function, and finishing, then:
U
ksin(kωt+θ
k)＝sin(kωt)U
kcos(θ
k)+cos(kωt)U
ksin(θ
k)
from the perspective of a complex function, where U
kcos(θ
k) And U
ksin(θ
k) Exactly the real and imaginary parts of the kth harmonic vector that needs to be measured. In the case of fixed fundamental wave and sampling frequencyNext, the function space sequence sin (k ω t)
i) And cos (k ω t)
i) In the time window of each cycle period is a fixed value. Therefore, according to the least square criterion, the relation equation between the sampled sample after each sampling and each function component is:
t
i-the ith sampling instant. After N consecutive samplings, N equations will be obtained. If it will be U
0、U
0λ, and the real and imaginary parts of all harmonics as unknowns and are represented by a matrix, the N-times sampling result can be represented by the following matrix equation:
if sampling at equal intervals is adopted, then
T is the period of the fundamental function.
If a is used to represent the coefficient matrix of N rows and 2(M +1) columns, X is used to represent the variable matrix to be measured of 2(M +1) rows in a single column, and U is used to represent the sampling matrix in a single column, the sampling matrix can be represented as:
A·X＝U
the third column element of the coefficient matrix a represents the value of sin (ω t) at each sampling instant and the fourth column element of a represents the value of cos (ω t) at each sampling instant. The fifth column element of a represents the value of the second harmonic sin (2 ω t) at each sampling instant, and so on.
Since the coefficient matrix A must have an inverse matrix A
-1Thus:
X＝A
-1·U
wherein, the inverse matrix A
-1Has a dimension of 2(M +1) × N.
A
-1I.e. a least squares filter. Once the sampling period has been selected according to the first step, A
-1Is a prioriA matrix of calculated constants.
Step three: and filtering the signal converted by the photoelectric converter according to a least square filter to obtain a direct current component of the signal converted by the photoelectric converter and harmonic amplitudes of each frequency point, which are respectively recorded as the radiation intensity and the flicker intensity of the flame at each frequency point.
According to the definition of matrix X and equation X ═ A
-1U, then:
the fundamental wave content calculation process is as follows:
the k-th harmonic is calculated by the following process:
the method has high time-frequency analysis precision, can accurately identify the frequency spectrum characteristics of the signal, can accurately depict the position and the boundary of the reservoir and can further improve the precision of reservoir prediction.
For example: aiming at the #2 furnace fire detection temperature measurement of Hua Dyeqing island power generation Limited company, the set has 28 optical fiber sensors which are respectively optical fiber flame detection devices, each device is divided into a front-end probe and a rear-end controller, the front-end probe realizes optical fiber sampling and photoelectric conversion, and a circuit in the probe is a circuit shown in figure 2. The flame light signal is converted into a current signal without distortion, and the current signal enters a controller at the rear end for analysis and processing.
28 optical fiber sensors and a monitoring host form a set of complete monitoring system through an RS-485 bus, and the burning condition and the quality of the pulverized coal in the boiler are displayed in a monitoring picture of the host.
The invention also provides a detection method for realizing the system for detecting the combustion quality of the pulverized coal of the burner by using the optical fiber.
The invention discloses a detection method for realizing a system for detecting the combustion quality of pulverized coal of a burner by using optical fibers, which comprises the following steps:
(1) the optical fiber sensor collects flame optical signals in the burner and transmits the flame optical signals to the processor through the photoelectric converter;
(2) the processor samples and performs spectrum analysis on the signals converted by the photoelectric converter, so as to separate the radiation intensity in the signals and the flicker intensity of flames at each frequency point; calculating the corrected background radiation intensity by correcting the shielding effect of the unburned particles on the background; describing the combustion quality of the pulverized coal of the burner by using the corrected background radiation intensity;
in the process of calculating the corrected background radiation intensity, firstly, the flicker intensity of flame at each frequency point is utilized to calculate the combustion degree of the pulverized coal for describing the shielding degree; and correcting the background radiation intensity by using the combustion degree of the pulverized coal, wherein the corrected background radiation intensity is the ratio of the radiation intensity to the combustion degree of the pulverized coal.
Specifically, a least square algorithm is adopted to sample and perform spectrum analysis on the signal converted by the photoelectric converter.
Specifically, the specific process of sampling and spectrum analysis of the signal converted by the photoelectric converter by using the least square algorithm is as follows:
the method comprises the following steps: determining the frequency and sampling period of the signal converted by the photoelectric converter according to Shennong sampling theory;
according to the fourier function theory, any one of the functions can be expressed as the following fourier function with a fundamental frequency ω:
wherein, U
0-a direct current component; λ -the dc component attenuation coefficient; u shape
k-the amplitude of the kth harmonic; ω -angular frequency of the fundamental current or voltage; theta
k-initial phase angle of the k-th harmonic. k is 1,2, …, M.
According to shennong's sampling theory, as long as the sampling frequency f is more than twice the signal frequency, a continuous function can be recovered from discrete sampling samples, including each periodic function component sin (k ω t) in u (t), and the like. Here, for example, if the highest recognizable frequency is 119Hz, the sampling frequency f must be 238Hz or more, and in the fast fourier algorithm, the sampling frequency f is generally ten times or more of the signal frequency, and for example, to recover a 119Hz signal, the sampling frequency generally needs a frequency of 1190Hz or more.
Step two: constructing a least square filter according to a least square algorithm;
the spectrum analysis is to obtain U finally by sampling the signal sequence
0、λ、U
k、θ
k. Currently, there are two methods to achieve this, the fourier algorithm and the least squares algorithm. The invention adopts a least square algorithm. For this purpose, the fourier function is first expanded and simplified.
Converting U in Fourier function
0e
-λtExpanding according to Taylor series, taking the first two terms, then:
U
0e
-λt≈U
0-U
0λt
sin (k ω t + θ)
k) Spreading according to a trigonometric function, sorting,then:
U
ksin(kωt+θ
k)＝sin(kωt)U
kcos(θ
k)+cos(kωt)U
ksin(θ
k)
from the perspective of a complex function, where U
kcos(θ
k) And U
ksin(θ
k) Exactly the real and imaginary parts of the kth harmonic vector that needs to be measured. Whereas the functional space sequence sin (k ω t) is determined for a given fundamental and sampling frequency
i) And cos (k ω t)
i) In the time window of each cycle period is a fixed value. Therefore, according to the least square criterion, the relation equation between the sampled sample after each sampling and each function component is:
t
i-the ith sampling instant. After N consecutive samplings, N equations will be obtained. If it will be U
0、U
0λ, and the real and imaginary parts of all harmonics as unknowns and are represented by a matrix, the N-times sampling result can be represented by the following matrix equation:
if sampling at equal intervals is adopted, then
T is the period of the fundamental function.
If a is used to represent the coefficient matrix of N rows and 2(M +1) columns, X is used to represent the variable matrix to be measured of 2(M +1) rows in a single column, and U is used to represent the sampling matrix in a single column, the sampling matrix can be represented as:
A·X＝U
the third column element of the coefficient matrix a represents the value of sin (ω t) at each sampling instant and the fourth column element of a represents the value of cos (ω t) at each sampling instant. The fifth column element of a represents the value of the second harmonic sin (2 ω t) at each sampling instant, and so on.
Since the coefficient matrix A must have an inverse matrix A
-1Thus:
X＝A
-1·U
wherein, the inverse matrix A
-1Has a dimension of 2(M +1) × N.
A
-1I.e. a least squares filter. Once the sampling period has been selected according to the first step, A
-1It is a matrix of constants that can be calculated in advance.
Step three: and filtering the signal converted by the photoelectric converter according to a least square filter to obtain a direct current component of the signal converted by the photoelectric converter and harmonic amplitudes of each frequency point, which are respectively recorded as the radiation intensity and the flicker intensity of the flame at each frequency point.
According to the definition of matrix X and equation X ═ A
-1U, then:
the fundamental wave content calculation process is as follows:
the k-th harmonic is calculated by the following process:
due to the shielding effect of the pulverized coal, the radiation intensity of the separated signal, that is, the direct current component of the flame light signal is actually the radiation intensity of the observation point, but not the background radiation intensity, and the background radiation intensity must be corrected according to the shielding rate of the pulverized coal to the background light.
The sizes and the flicker characteristics of the flame on the fundamental wave point and each subharmonic frequency point reflect the motion characteristics of particles in a hearth wind field, the more obvious the characteristics are, the larger the concentration of the particles is, the more serious the shielding of the background light is caused if the concentration is higher, and therefore, the characteristics negatively contribute to the background light.
The degree of occlusion is described by the degree of pulverized coal combustion E as follows:
wherein, U
max-maximum average scintillation intensity. When each flicker intensity reaches the maximum, E is minimum (tends to be 0), indicating that the shielding is serious, and when each flicker intensity is small, E is large (tends to be 1), indicating that the shielding effect is small.
Therefore, the real background intensity U should be inversely corrected according to the magnitude of E. The corrected background intensity U is:
the above formula comprehensively describes the radiation intensity U directly observed by an observation point
0The relationship between the degree of combustion E of the pulverized coal and the radiation intensity U of the burnout front of the pulverized coal also describes and represents the combustion quality of the burner.
The method further comprises the following steps: the processor also transmits the combustion quality of the pulverized coal of the burner to the monitoring host through the bus for real-time monitoring.
In the pulverized coal combustion quality detection method provided by the invention, the corrected background radiation intensity is calculated by correcting the shielding effect of unburned particulate matters on the background; the combustion quality of the pulverized coal of the burner is described by using the corrected background radiation intensity, so that a theoretical basis is provided for flame state detection, combustion quality detection and the like;
the pulverized coal combustion quality detection method provided by the invention realizes the quantitative evaluation index of the pulverized coal combustion degree;
the combustion quality detection method provided by the invention has a direct help effect on improving the refined combustion adjustment level and the environmental protection level of the boiler in the current thermal power generation field, fills the blank of the field, and has great economic benefit and social benefit.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (8)
1. A system for detecting the pulverized coal combustion quality of a burner by using optical fibers is characterized by comprising:
the optical fiber sensor is arranged at the burner port and is configured to collect flame optical signals in the burner and transmit the flame optical signals to the processor through the photoelectric converter;
the processor is configured to sample and perform spectrum analysis on the signal converted by the photoelectric converter so as to separate the radiation intensity U in the signal
0And the maximum average flicker intensity of the coal fines; calculating the background radiation intensity U by correcting the shielding degree of the unburned particles to the background; describing the combustion quality of the pulverized coal of the burner by using the background radiation intensity U;
wherein, in the process of calculating the background radiation intensity U, the maximum average flicker intensity U of the coal powder is firstly utilized
maxAnd calculating the combustion degree E of the pulverized coal, wherein,
n is the number of samplings, U
kDescribing the shielding degree by using the combustion degree E of the coal powder as the flicker intensity of the coal powder; then the combustion degree E of the pulverized coal is utilized to correct the radiation intensity U
0Thus obtaining a corrected radiation intensity, i.e. background radiation intensity U, the formula of the correction being: u is equal to U
0E, i.e. the background radiation intensity U is the radiation intensity U
0The ratio to the degree of combustion E of the pulverized coal.
2. The system for detecting the quality of pulverized coal combustion of a burner by using an optical fiber as claimed in claim 1, wherein the photoelectric converter comprises an integrated operational amplifier and a photoresistor connected in parallel with the integrated operational amplifier, and the input of the inverting terminal of the integrated operational amplifier is superposed with the negative feedback voltage of the photoresistor and then output.
3. The system for performing burner pulverized coal combustion quality detection using optical fiber according to claim 1, wherein the processor is further configured to sample and spectrally analyze the converted signal from the photoelectric converter using a least squares algorithm.
4. The system for detecting the combustion quality of the pulverized coal of the burner by using the optical fiber as claimed in claim 1, wherein the processor is further connected with the monitoring host through a bus.
5. The method for detecting the combustion quality of the pulverized coal of the burner by using the optical fiber according to claim 1, comprising the following steps:
the optical fiber sensor collects flame optical signals in the burner and transmits the flame optical signals to the processor through the photoelectric converter;
the processor samples and performs spectrum analysis on the signal converted by the photoelectric converter, thereby separating the radiation intensity U in the signal
0And the maximum average flicker intensity of the coal fines; calculating the background radiation intensity U by correcting the shielding effect of the unburned particles on the background;describing the combustion quality of the pulverized coal of the burner by using the background radiation intensity U; wherein, in the process of calculating the background radiation intensity, the maximum average flicker intensity U of the coal powder is firstly utilized
maxAnd calculating the combustion degree E of the pulverized coal, wherein,
n is the number of samplings, U
kDescribing the shielding degree by using the coal powder combustion degree E as the flicker intensity of the coal powder, and when the maximum average flicker intensity of the coal powder reaches the maximum, the coal powder combustion degree is minimum, which indicates that the shielding is serious; then the combustion degree of the pulverized coal is utilized to correct the radiation intensity U
0Thus obtaining a corrected radiation intensity, i.e. background radiation intensity U, the formula of the correction being: u is equal to U
0E, i.e. the background radiation intensity U is the radiation intensity U
0The ratio to the degree of combustion E of the pulverized coal.
6. The method for detecting the quality of combustion of pulverized coal in a burner by using an optical fiber as claimed in claim 5, wherein the least square algorithm is used to sample and spectrally analyze the signal converted by the photoelectric converter.
7. The method for detecting the burner pulverized coal combustion quality detection system by using the optical fiber as claimed in claim 6, wherein the specific process of sampling and spectrum analysis of the signal converted by the photoelectric converter by using the least square algorithm is as follows:
determining the frequency and sampling period of the signal converted by the photoelectric converter according to Shennong sampling theorem;
constructing a least square filter according to a least square algorithm;
and filtering the signal converted by the photoelectric converter according to a least square filter to obtain a direct current component of the signal converted by the photoelectric converter and harmonic amplitudes of each frequency point, which are respectively recorded as the radiation intensity and the maximum average flicker intensity of the pulverized coal.
8. The method for detecting the combustion quality of the pulverized coal of the burner by using the optical fiber as claimed in claim 5, wherein the method further comprises: the processor also transmits the combustion quality of the pulverized coal of the burner to the monitoring host through the bus for real-time monitoring.
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