Boiler heating surface temperature and ash deposition state synchronous measurement method based on LIP technology

Abstract

The invention relates to a temperature measurement technology, and aims to provide a boiler heating surface temperature and ash deposition state synchronous measurement method based on an LIP technology. Comprising the following steps: irradiating a calibration plate in a blackbody furnace with ultraviolet laser to generate a phosphorescence signal, simultaneously collecting phosphorescence signal images of two characteristic wavelengths formed by excitation, and completing calibration by changing temperature and dust deposition conditions; the same phosphorescent material is sprayed on the dust-deposition-free surface of the heating surface in the boiler to form a coating, excitation and collection are carried out in the same mode in the boiler operation and gradual dust deposition process, and the real-time two-dimensional temperature field of the heating surface and the current dust deposition amount on the heating surface in the boiler are calculated according to the calibration curve. According to the invention, two-dimensional temperature field measurement and dust deposition condition determination can be realized at the same time by using only one set of equipment; the phosphorescent coating can be recycled on the heating surface of the boiler, so that the economical efficiency is higher; the measurement is not interfered by radiation properties of objects and environmental factors, and the heat balance state in the boiler is not damaged; the measuring method is simpler and high in accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of temperature measurement, and in particular to a method for synchronously measuring the temperature of a boiler heating surface and an ash accumulation state based on laser-induced phosphorescence. Background Art

[0002] Boilers are core power equipment in the electric power, petrochemical, metallurgy, building materials, light industry and other industries. Timely acquisition of surface temperature information and dust accumulation data of boiler heating surfaces is crucial to the safe and economical operation of various power equipment. In the prior art, the means of measuring temperature on solid surfaces such as boiler heating surfaces can be divided into contact temperature measurement and non-contact temperature measurement. The contact temperature measurement method represented by thermocouples has problems such as only point measurement, slow response, and complex maintenance. The non-contact temperature measurement method mainly includes passive radiation temperature measurement technology and active laser temperature measurement technology. Among them, passive radiation temperature measurement is widely used in engineering, but due to the uncertainty of the surface emissivity of the object and the presence of background thermal radiation interference, it is difficult to achieve accurate temperature measurement in complex thermal environments.

[0003] In recent years, the rapid development of laser technology has made laser-based online temperature field measurement technology attract much attention. Active laser temperature measurement technology is represented by laser induced phosphorescence (LIP), which is a non-contact optical temperature measurement technology based on the temperature-sensitive phosphorescence signal generated by the stimulated phosphorescent coating on the target surface to achieve temperature measurement. By spraying phosphorescent material on the surface of the target to be measured, and exciting the phosphorescent material with a laser of a specific wavelength to make its electrons transition from the ground state to the high energy state, when it returns from the high energy state to the ground state, the photons radiated outward are phosphorescence. The luminescence lifetime or characteristic spectral intensity ratio of phosphorescence has temperature-sensitive characteristics. Therefore, by calibrating the characteristic spectral intensity ratio of phosphorescence or the function calibration curve of lifetime and temperature, the solid surface temperature field measurement can be carried out based on this. Since the phosphorescence signal is independent of the material properties of the target surface to be measured and there are multiple characteristic emission wavelengths, the laser induced phosphorescence temperature measurement method is not interfered by the unknown emissivity of the target and the background thermal radiation, and has the advantages of high measurement accuracy, fast response, wide temperature range, and the ability to achieve two-dimensional temperature field measurement.

[0004] During the combustion process, the boiler will continuously generate dust, which will be adsorbed and retained on the inner wall of the furnace body to form ash accumulation. Since the thermal conductivity of ash accumulation is very small, it will affect heat transfer when it is retained on the boiler heating surface, resulting in a decrease in the temperature of the heat-absorbing medium and an increase in the exhaust gas temperature, thereby reducing the thermal efficiency of the boiler. When ash accumulation is serious, the flue gas flow cross-sectional area will be reduced, the flow resistance will be increased, the power consumption of the induced draft fan will be increased, the boiler operating load will be reduced, and even the boiler will be forced to shut down. Ash accumulation will also increase the flue gas temperature at the rear, affecting the safe operation of the tail heating surface. If the local ash accumulation is serious, it may even form a "smoke corridor", causing the local heating surface to increase due to the increase in smoke velocity and aggravated wear. Therefore, it is necessary to set up a soot blowing device inside the boiler and regularly introduce compressed air to blow the boiler heating surface to keep it clean. In existing operations, compressed air or steam is usually introduced by timing the opening and closing of valves on the gas path, but with the changes in production load, combustion material components, and combustion atmosphere, the degree of ash accumulation on the boiler heating surface is not a linear process. If a timed air blowing program is set based on experience, the following situations are likely to occur: when there is little ash accumulation, there will be too much air blowing, which will waste compressed air and steam and affect combustion; when there is a lot of ash accumulation, there will be insufficient air blowing, which will make it difficult to clean in time and cause the ash accumulation to become serious. Therefore, it is necessary to measure the ash accumulation degree on the boiler heating surface and adjust the air blowing volume or frequency in time according to the measurement results to ensure the efficient operation of the boiler.

[0005] In the prior art, the degree of ash accumulation is usually estimated or predicted by indirectly measuring heat transfer parameters related to ash accumulation. Among them, the furnace outlet flue gas temperature is a relatively mature parameter for predicting the ash degree of the heating surface, but the process is only inferred based on the result based on this parameter; that is, ash accumulation has occurred on the heating surface, resulting in deterioration of heat transfer, causing the furnace outlet flue gas temperature to further increase. This method is difficult to accurately predict the soot blowing moment of the heating surface, and it is impossible to obtain the ash accumulation situation of the local heating surface. In addition, a new method of directly observing the ash condition of the heating surface represented by graphics processing technology can effectively obtain the ash condition of the local heating surface, but it usually requires calibration of the camera coordinate system and the furnace coordinate system and three-dimensional reconstruction of the feature points. The process is relatively complicated, especially for the initial ash accumulation when the amount of ash is small, it is impossible to make a quick judgment and early warning.

[0006] Although the surface temperature and ash accumulation of the heating surface are measured simultaneously around the boiler equipment, the two measurement activities are independent of each other in the existing technology, and two independent measurement schemes are generally adopted. This leads to the disadvantages of the measurement system around the heating surface of the boiler, such as complex structure, high comprehensive cost, background thermal radiation interference, unknown emissivity in the furnace, and inability to provide early warning of ash accumulation.

[0007] In view of the above situation, the present invention intends to provide a technical solution that can simultaneously realize boiler heating surface temperature measurement and ash accumulation monitoring. Summary of the invention

[0008] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for synchronously measuring the temperature and ash accumulation state of a boiler heating surface based on the LIP technology.

[0009] To solve the technical problem, the technical solution of the present invention is as follows:

[0010] A method for synchronously measuring the temperature and ash accumulation state of a boiler heating surface based on LIP technology is provided, comprising the following steps:

[0011] (1) Phosphorescent material Y3Al5O 12 :Dy is mixed with a proper amount of high temperature glue to prepare a phosphorescent material spray;

[0012] (2) spraying a spray on the surface of the calibration plate to form a phosphorescent coating, and placing the calibration plate in a black body furnace with an optical window; irradiating the calibration plate with an ultraviolet laser of a wavelength of 355 nm to excite and generate phosphorescent signals; using an image acquisition device to simultaneously acquire phosphorescent signal images of two characteristic wavelengths of 458 nm and 497 nm, and the coordinates on the two images correspond one to one;

[0013] (3) continuously changing the inner cavity temperature of the black body furnace within the calibration range, and recording the phosphorescence signal images of the calibration plate at the two characteristic wavelengths in the absence of dust accumulation; then gradually changing the dust accumulation mass per unit area on the calibration plate under different temperature conditions, and collecting the phosphorescence signal images of the two characteristic wavelengths in each dust accumulation state;

[0014] (4) performing intensity ratio calculation and fitting processing on the acquired phosphorescence signal image, and completing calibration of the phosphorescence intensity ratio temperature-sensitive response curve and the temperature-sensitive response curve of the phosphorescence signal intensity at a characteristic wavelength of 458 nm under dust-free conditions; using the phosphorescence signal intensity at a wavelength of 458 nm on the dust-free heated surface as the normalization standard, performing intensity ratio calculation and fitting processing on the phosphorescence signals acquired under different dust accumulation conditions, and completing calibration of the dust accumulation response curve of the phosphorescence signal intensity at a wavelength of 458 nm under different temperature conditions;

[0015] (5) Spraying the same phosphorescent material spray on the dust-free surface of the heating surface inside the boiler to form a phosphorescent coating, and an optical window is provided on the boiler wall; while the boiler is running and gradually accumulating dust, irradiating the heating surface with an ultraviolet laser of a wavelength of 355 nm to stimulate the generation of phosphorescent signals, and using an image acquisition device to simultaneously acquire phosphorescent signal images of two characteristic wavelengths of 458 nm and 497 nm, and the coordinates on the two images correspond one to one;

[0016] (6) After calculating the ratio of the phosphorescence signal images of two different characteristic wavelengths, the real-time two-dimensional temperature field of the boiler heating surface is obtained according to the calibrated phosphorescence intensity ratio temperature-sensitive response curve; based on the real-time temperature field data and the 458nm characteristic wavelength phosphorescence signal intensity temperature-sensitive response curve under the condition of no ash accumulation, the phosphorescence intensity signal value of the heating surface without ash accumulation under the corresponding temperature condition is obtained; this value is used as a normalization standard and the intensity ratio is calculated with the collected phosphorescence signal image of the boiler heating surface at a wavelength of 458nm, and the ash accumulation amount response curve of the phosphorescence signal intensity under the corresponding temperature condition is compared to obtain the current ash accumulation amount on the heating surface inside the boiler.

[0017] As a preferred embodiment of the present invention, the method further comprises adjusting the soot blowing time node and the compressed air pressure according to a preset soot blowing control scheme based on the calculated value of the current soot accumulation on the internal heating surface of the boiler.

[0018] As a preferred embodiment of the present invention, the ultraviolet laser used to excite and generate phosphorescence signals is obtained in the following manner: a timing synchronization controller is used to control the laser to emit a 355nm ultraviolet laser, which is expanded into a planar light source by a beam expander composed of a concave lens and a convex lens, and then irradiated onto the phosphorescent coating.

[0019] As a preferred embodiment of the present invention, the image acquisition device for simultaneously acquiring phosphorescence signal images of two characteristic wavelengths is a device that installs two narrow-band filters that respectively make the transmittance of the two characteristic wavelengths of 458nm and 497nm the highest in front of the imaging lens of the camera, thereby ensuring that only the phosphorescence signals of these two characteristic wavelengths enter the photosensitive device of the camera.

[0020] As a preferred embodiment of the present invention, the step (3) of continuously changing the inner cavity temperature of the black body furnace within the calibration range refers to changing the inner cavity temperature of the black body furnace within the range of 300K to 1000K at intervals of 10K.

[0021] As a preferred embodiment of the present invention, in step (3), the calibration operation of the phosphorescence intensity ratio temperature sensitive response curve specifically includes:

[0022] The ratio of the average signal intensities of two phosphorescence signal images corresponding to different characteristic wavelengths obtained simultaneously at each temperature T is calculated to obtain the signal intensity ratio R of the two characteristic wavelengths under the temperature condition; the signals under all temperature conditions within the continuous change range are processed and calculated to obtain the response curve f1(R,T) of the signal ratio R to the temperature T, and the calibration of the temperature-sensitive response curve of the phosphorescence intensity ratio is completed.

[0023] As a preferred embodiment of the present invention, in step (3), the calibration operation of the temperature-sensitive response curve of the phosphorescence signal intensity at a characteristic wavelength of 458 nm under dust-free conditions specifically includes:

[0024] The phosphorescence signal with a wavelength of 458 nm obtained at each temperature T was curve fitted to obtain the phosphorescence signal intensity I under the condition of no dust accumulation. x The response curve f2(I x ,T), complete the calibration of the temperature-sensitive response curve of the phosphorescence signal intensity at the characteristic wavelength of 458nm under dust-free conditions.

[0025] As a preferred embodiment of the present invention, in step (3), the calibration operation of the phosphorescence signal intensity dust accumulation response curve under different temperature conditions specifically includes:

[0026] The calibration plate is evenly loaded with fly ash, with the fly ash mass per unit area m h As a quantitative value of the dust accumulation state; the calibration plate is placed in a black body furnace and the furnace is adjusted to a specific temperature T s Conditions; Based on each dust accumulation state m h The generated 458nm phosphorescence image G2 will have different average signal intensities I2; record the phosphorescence signal under fixed temperature conditions and specific dust accumulation conditions, and then calculate the ratio R of the signal intensity under the specific dust accumulation condition to the 458nm phosphorescence signal intensity under no dust accumulation. h =I2(T S ) / I x (T S ), and then curve fitting is performed to obtain the signal intensity ratio R h The response curve f3(R h ,m h ), complete the dust accumulation response curve of the phosphorescence signal intensity at 458nm wavelength under different temperature conditions.

[0027] The present invention further provides a boiler heating surface temperature and ash accumulation state synchronous measurement system based on LIP technology for implementing the above method, comprising: a laser generating device, an image acquisition device and a data processing device; wherein,

[0028] The laser generating device comprises a timing synchronization controller, a laser and a beam expander; the beam expander is composed of a concave lens and a convex lens and is arranged on the laser optical path of the laser;

[0029] The image acquisition device is two independent cameras, or a single camera with a stereo lens; a narrow-band filter with a specific wavelength is installed in front of the imaging lens of the camera;

[0030] The data processing device is a host computer, including a central processing unit, a memory and a data transmission interface;

[0031] The timing synchronization controller is connected to the laser and the image acquisition device through signal lines, and the image acquisition device is connected to the data processing device through signal lines; the memory of the host computer is loaded with a software program, and the central processing unit can load the software program to perform the calculation work in the above method.

[0032] As a preferred embodiment of the present invention, the laser is a pulsed laser or a continuous laser, and the laser energy is adjustable; the image acquisition device is a CCD camera, an enhanced CCD camera, a CMOS camera or an enhanced CMOS camera.

[0033] Description of the invention principle:

[0034] Phosphorescent material Y3Al5O 12 It is common knowledge that Dy can generate phosphorescent signals under the excitation of electromagnetic radiation or ion rays. During the long-term in-depth research process, the applicant found that the phosphorescent intensity ratio of the two characteristic emission peaks of 458nm and 497nm of the phosphorescent material has a monotonically changing temperature-sensitive property, so based on this discovery, the innovative technical solution of the present application is proposed.

[0035] The technical solution of the present invention is based on laser induced phosphorescence technology to achieve synchronous measurement of boiler heating surface temperature and ash accumulation status. Specifically, a specific wavelength laser is used to excite the phosphorescent coating on the boiler heating surface to induce the generation of phosphorescent signals, and an image acquisition device is used to collect signals. Based on the temperature sensitive characteristics of the phosphorescent spectrum signal, and the intensity value of the phosphorescent signal of the heating surface without ash accumulation is used as the normalization standard, the two-dimensional temperature field measurement of the boiler heating surface and the ash accumulation status determination are achieved at the same time.

[0036] After in-depth theoretical research and experimental verification, the applicant's research team found that the phosphorescence intensity ratio method based on laser-induced phosphorescence technology is not affected by the unknown emissivity of the target and the background thermal radiation, and the temperature measurement result only depends on the measured surface temperature. Therefore, the present invention selects the phosphorescent material Y3Al5O suitable for the phosphorescence intensity ratio method. 12 :Dy, the temperature sensitivity of this material is that when the phosphorescent material is excited by a laser with a specific wavelength of 355nm, two characteristic wavelengths of 458nm and 497nm are obtained, and the intensity ratio of the two wavelengths shows a monotonic change trend with temperature. By calibrating the monotonic function relationship between the ratio of the two characteristic wavelengths and the temperature, the two-dimensional temperature field information of the measured surface can be obtained based on the monotonic function relationship and the measured ratio of the two characteristic wavelengths in an engineering environment.

[0037] At the same time, the change of phosphorescence signal generated after the phosphorescent coating is excited is mainly determined by temperature and dust accumulation state, and secondary factors include background scattering, etc. Since the phosphorescence signal shows a monotonically weakening trend with the increase of dust accumulation degree, and the use of ratio calculation can reduce the interference of other factors such as background scattering, the dust accumulation state determination result is finally achieved only by the dust accumulation degree.

[0038] Before applying the present invention to actual projects, it is necessary to first use a calibration plate with a phosphorescent coating and a black body furnace with an optical window, based on laser irradiation and phosphorescent signal recording, to calibrate the phosphorescent intensity ratio temperature-sensitive response curve, the phosphorescent signal intensity temperature-sensitive response curve of 458nm wavelength under no ash accumulation conditions, and the phosphorescent signal intensity ash accumulation amount response curve of 458nm wavelength under different temperature conditions. On this basis, the present invention can be applied to actual projects for synchronous measurement of boiler heating surface temperature and ash accumulation status.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. After the phosphor coating is sprayed on the boiler heating surface measurement area, only one set of equipment is needed to simultaneously realize the two-dimensional temperature field measurement of the heating surface and the determination of the dust accumulation. In addition, due to the high temperature resistance and high adhesion of the phosphor coating, the phosphor coating used in the present invention can be recycled on the boiler heating surface, which is more economical.

[0041] 2. The temperature measurement of the boiler heating surface in the present invention is based on the principle of laser-induced phosphorescence, which is not affected by the radiation properties of the object itself and environmental factors, and does not destroy the internal thermal equilibrium state of the boiler. Compared with various solutions in the prior art, the method used in the present invention is simpler and has higher measurement accuracy.

[0042] 3. The ash state of the boiler heating surface in the present invention is measured based on the attenuation of the phosphorescence signal, which has high sensitivity and higher ash accumulation perception ability compared with the existing direct observation method, thereby achieving timely warning of the progress of ash accumulation.

[0043] 4. Based on the use of the present invention, the blowing strategy can be flexibly adjusted according to the dust accumulation situation in actual production, which can save compressed air and steam while better avoiding the impact on the stable operation of the boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the calibration device of the present invention;

[0045] Figure 2 It is a schematic diagram of the measuring device of the present invention;

[0046] Figure 3 The phosphorescence intensity ratio temperature-sensitive response curve of the embodiment of the present invention;

[0047] Figure 4 This is a temperature-sensitive response curve of the phosphorescence signal intensity at a characteristic wavelength of 458 nm under dust-free conditions according to an embodiment of the present invention;

[0048] Figure 5 This is the response curve of the phosphorescence signal intensity ratio at a wavelength of 458nm to the amount of dust accumulation under 300K conditions;

[0049] Figure 6 This is the response curve of the phosphorescence signal intensity ratio at a wavelength of 458nm to the amount of dust accumulation under 774K conditions.

[0050] Figure numerals: 1 calibration plate; 2 thermal environment (black body furnace during calibration, boiler furnace body during measurement); 3 laser; 4 timing synchronization controller; 5 beam expander; 6 first ICCD camera; 7 second ICCD camera; 8 host computer; 9 stereo lens. DETAILED DESCRIPTION

[0051] The specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. For those of ordinary skill in the art, without departing from the concept of the present invention, several variations and improvements can also be made, all of which should belong to the protection scope of the present invention.

[0052] Part I Implementation of the Invention

[0053] 1. Structural layout of the measurement system

[0054] In order to achieve the measurement purpose of the present invention, it is first necessary to build a system for calibration and measurement. Except for the object to be measured, all other components of the system are reused.

[0055] The measuring system comprises: a laser generating device, an image acquisition device and a data processing device; wherein the laser generating device comprises a timing synchronization controller, a laser and a beam expander; the beam expander consists of a concave lens and a convex lens and is arranged on the laser optical path of the laser; the image acquisition device is two independent cameras, or a single camera with a stereo lens; a narrow-band filter of a specific wavelength is installed in front of the imaging lens of the camera; the data processing device is a host computer, comprising a central processing unit, a memory and a data transmission interface; the timing synchronization controller is connected to the laser and the image acquisition device respectively through signal lines, and the image acquisition device is connected to the data processing device through signal lines; a software program is loaded in the memory of the host computer, and the central processing unit can load the software program to execute the calculation work in the measuring method described in the present invention.

[0056] As an optional example, the laser is a pulsed laser or a continuous laser, and the laser energy is adjustable; the image acquisition device is a CCD camera, an enhanced CCD camera, a CMOS camera or an enhanced CMOS camera.

[0057] 2. Operation content of measurement method

[0058] The method for synchronously measuring the temperature and ash accumulation state of the boiler heating surface based on the LIP technology of the present invention includes two parts: calibration operation and actual measurement operation, which are as follows:

[0059] (1) Phosphorescent material Y3Al5O 12 :Dy is mixed with a proper amount of high temperature glue to prepare a phosphorescent material spray;

[0060] (2) Spray a spray on the surface of the calibration plate to form a phosphorescent coating, and place it in a black body furnace (or boiler) equipped with an optical window; use a timing synchronization controller to control the laser to emit a 355nm ultraviolet laser, which is expanded into a planar light source through a beam expander composed of a concave lens and a convex lens, and then irradiated on the phosphorescent coating to stimulate the generation of phosphorescent signals.

[0061] Narrowband filters with central wavelengths of 458nm and 497nm are installed in front of the camera imaging lens of the image acquisition device to ensure that only the phosphorescence signals of these two characteristic wavelengths enter the photosensitive device of the camera. The image acquisition device is used to simultaneously acquire the phosphorescence signal images of these two characteristic wavelengths, and the coordinates on the two images correspond one to one.

[0062] (3) Calibration operation:

[0063] The inner cavity temperature of the black body furnace is continuously changed within the calibration range (e.g., 300K to 1000K at intervals of 10K), and the phosphorescence signal images of two characteristic wavelengths are recorded without dust accumulation. Then, under different temperature conditions, the dust accumulation mass per unit area on the calibration plate is gradually changed, and the phosphorescence signal images of two characteristic wavelengths are collected under each dust accumulation state.

[0064] (4) Calculate and fit the intensity ratio of the acquired phosphorescence signal image, and complete the calibration of the phosphorescence intensity ratio temperature-sensitive response curve and the temperature-sensitive response curve of the phosphorescence signal intensity at a characteristic wavelength of 458nm under dust-free conditions. Take the phosphorescence signal intensity at a wavelength of 458nm on the dust-free heating surface as the normalization standard, calculate and fit the intensity ratio of the phosphorescence signal at the same characteristic wavelength acquired under different dust accumulation conditions, and complete the calibration of the dust accumulation response curve of the phosphorescence signal intensity at a characteristic wavelength of 458nm under different temperature conditions; wherein,

[0065] (4.1) The calibration operation of the phosphorescence intensity ratio temperature sensitive response curve includes:

[0066] The ratio of the average signal intensities of the two phosphorescence signal images corresponding to different characteristic wavelengths obtained simultaneously at each temperature T is calculated to obtain the signal intensity ratio R of the two characteristic wavelengths of 458nm and 497nm under the temperature condition; the signals under all temperature conditions within the continuous change range are processed and calculated to obtain the response curve f1(R,T) of the signal ratio R to the temperature T, and the calibration of the phosphorescence intensity ratio temperature-sensitive response curve is completed.

[0067] (4.2) The calibration operation of the temperature-sensitive response curve of the phosphorescence signal intensity at a characteristic wavelength of 458 nm under dust-free conditions specifically includes:

[0068] The phosphorescence signal at the characteristic wavelength of 458 nm obtained at each temperature T was curve fitted to obtain the phosphorescence signal intensity I of the dust-free calibration plate. x The response curve f2(I x ,T), complete the calibration of the temperature-sensitive response curve of the phosphorescence signal intensity at the characteristic wavelength of 458nm under dust-free conditions.

[0069] (4.3) The calibration operation of the phosphorescence signal intensity dust accumulation response curve at the characteristic wavelength of 458nm under different temperature conditions specifically includes:

[0070] The calibration plate is evenly loaded with fly ash, with the fly ash mass per unit area m h As a quantitative value of the dust accumulation state; the calibration plate is placed in a black body furnace and the furnace is adjusted to a specific temperature T s Conditions; Based on each dust accumulation state m h The generated phosphorescence image G2 will have different average signal intensities I2; record the phosphorescence signal under fixed temperature conditions and specific dust accumulation conditions, and then calculate the ratio R of the signal intensity under the specific dust accumulation condition to the phosphorescence signal intensity under no dust accumulation. h =I2(T S ) / I x (T S ), and then curve fitting is performed to obtain the signal intensity ratio R h The response curve f3(R h ,m h ), and complete the response curve of phosphorescence signal intensity and dust accumulation amount at the characteristic wavelength of 458nm under different temperature conditions.

[0071] (5) Measurement operation: Spray the phosphorescent material onto the dust-free surface of the heating surface inside the boiler to form a phosphorescent coating. An optical window is provided on the boiler wall. When the boiler is running and gradually accumulating dust, the heating surface is irradiated with an ultraviolet laser of wavelength 355 nm to stimulate the generation of phosphorescent signals. An image acquisition device is used to simultaneously acquire phosphorescent signal images at two characteristic wavelengths of 458 nm and 497 nm. The coordinates on the two images correspond to each other.

[0072] (6) After calculating the ratio of the phosphorescence images of two different characteristic wavelengths, the real-time two-dimensional temperature field of the boiler heating surface is obtained according to the calibrated phosphorescence intensity ratio temperature-sensitive response curve; based on the real-time temperature field data and the temperature-sensitive response curve of the phosphorescence signal intensity of the 458nm characteristic wavelength under the condition of no ash accumulation, the phosphorescence intensity signal value of the 458nm characteristic wavelength of the heating surface without ash accumulation under the corresponding temperature conditions is obtained; the value is used as the normalization standard, and the intensity ratio is calculated with the phosphorescence intensity signal image of the same characteristic wavelength of the boiler heating surface collected; the ash accumulation amount on the heating surface inside the current boiler is obtained by comparing the phosphorescence signal intensity ash accumulation amount response curve under the corresponding temperature conditions;

[0073] (7) After calculating the current value of the ash accumulation on the internal heating surface of the boiler, the soot blowing time node and the compressed air pressure can be adjusted according to the preset soot blowing control scheme to achieve the purpose of maximizing the overall energy efficiency.

[0074] Part II: A specific implementation case

[0075] The calibration device provided in this embodiment is as follows Figure 1 As shown, the measuring device is as Figure 2 As shown. The image acquisition device used is an ICCD camera (i.e., an enhanced CCD camera). The processing and calculation of the image signal data are all implemented using a software program installed in the host computer 8. This part of the content belongs to conventional technical means and is not the focus of the present invention, so it will not be repeated.

[0076] The entire process of calibration and measurement operations is shown below:

[0077] (1) Phosphorescent material Y3Al5O 12 :Dy and high temperature glue are mixed in a certain proportion to prepare a phosphorescent material spray, which is sprayed on the surface of the calibration plate 1 to form a phosphorescent coating. The calibration plate 1 is placed in the inner cavity of the black body furnace 2, and an optical window is provided on the furnace wall.

[0078] (2) Under the control of the timing synchronization controller 4, the laser 3 emits a 355nm ultraviolet laser; after being expanded by the beam expander 5 composed of a concave lens and a convex lens, it irradiates the phosphorescent coating of the calibration plate 1 in the form of a planar light source and excites the generation of a phosphorescent signal.

[0079] (3) The first ICCD camera 6 and the second ICCD camera 7 (or reference Figure 2 A first ICCD camera 6) with a stereo lens 9 is used to aim at the optical window of the black body furnace. Narrowband filters with central wavelengths of 458nm and 497nm are installed in front of the imaging lens to simultaneously capture two characteristic wavelength phosphorescence signal images, and make the coordinates on the two images correspond one to one.

[0080] (4) The inner cavity temperature of the black body furnace 2 is changed within the range of 300K to 1000K at intervals of 10K, and the phosphorescence signal image at each temperature is recorded by a CCD camera and transmitted to the host computer 8 for processing; the average signal intensities I1 and I2 of the two phosphorescence images G1 and G2 simultaneously obtained at different characteristic wavelengths at each temperature T are calculated to obtain the phosphorescence signal intensity ratio R=I1 / I2 of the two characteristic wavelengths at the temperature; the signal processing is completed at all temperatures to obtain the response curve f1(R,T) of the phosphorescence signal ratio R with temperature T, and the phosphorescence intensity ratio temperature sensitivity curve is calibrated. The obtained response curve is as follows: Figure 3 shown.

[0081] (5) Select the phosphorescence signal I2 of the characteristic emission peak of 458 nm collected in step (4), and perform curve fitting on the average signal intensity I2 of the phosphorescence image G2 obtained at each temperature T to obtain the phosphorescence signal intensity I2 of the dust-free calibration plate 458 The response curve f2(I 458 ,T), complete the 458nm phosphorescence signal intensity calibration under dust-free conditions, and the resulting response curve is as follows Figure 4 shown.

[0082] (6) The calibration plate is evenly loaded with fly ash, with the fly ash mass per unit area m h As a quantitative value of the dust accumulation state; the calibration plate is placed in a black body furnace at a specific temperature T s Under the condition, based on each dust accumulation state m h The generated phosphorescence image G2 will have different average signal intensities I2; record the phosphorescence signal under fixed temperature conditions and specific dust accumulation conditions, and then calculate the ratio R of the signal intensity under the specific dust accumulation condition to the phosphorescence signal intensity under no dust accumulation. h =I2(T S ) / I 458 (T S ) ; then perform curve fitting to obtain the ratio R h The response curve f3(R h ,m h ), complete the calibration of the dust accumulation response curve corresponding to the phosphorescence signal intensity under different temperature conditions. For example, Figure 5 and Figure 6 The response curves of the 458nm phosphorescence signal intensity ratio to the ash accumulation per unit area at 300K and 774K are shown respectively. The latter is an example of boiler operating temperature conditions.

[0083] (7) Spraying the phosphorescent material spray prepared in step (1) onto the dust-free surface of the boiler heating surface to form a phosphorescent coating, and providing an optical window on the furnace wall.

[0084] (8) The first ICCD camera 6 (or reference Figure 1 Two ICCD cameras were used to aim at the optical window of the boiler, and narrow-band filters with central wavelengths of 458nm and 497nm were installed in front of the imaging lens. When the boiler was running and gradually accumulating dust, the heating surface was irradiated with a 355nm ultraviolet laser to stimulate the generation of phosphorescence signals; at the same time, two characteristic wavelength phosphorescence signal images at a certain moment were collected, namely G3 and G4, and the coordinates on the two images corresponded one to one.

[0085] (9) The phosphorescence signal image is recorded by a CCD camera and transmitted to the host computer 8 for processing. The ratio of the two phosphorescence images G3 and G4 obtained at different characteristic wavelengths is calculated to obtain the phosphorescence signal intensity ratio R=I3 / I4 of the two characteristic wavelengths. According to the calibrated phosphorescence temperature-sensitive response curve f1(R,T), the real-time two-dimensional temperature field of the boiler heating surface is obtained.

[0086] (10) Based on the temperature field data of the boiler heating surface obtained in step (9), and the temperature sensitive response curve f2(I 458 ,T), obtain the phosphorescence intensity signal value of the dust-free heating surface at this temperature; use this value as the normalization standard, select the phosphorescence signal G4 of the 458nm emission peak collected in step (9) as the detection source to obtain its phosphorescence intensity signal I4, and calculate the ratio R of the phosphorescence intensity signal under the dust-free condition h =I4 / I 458 (T); according to the phosphorescence signal intensity response curve f3 (R) of the dust accumulation state calibration plate under the corresponding temperature conditions obtained in step (6) h ,m h ), calculate the current amount of ash accumulation on the internal heating surface of the boiler.

[0087] (11) According to the values ​​obtained in step (9), the soot blowing time node and the compressed air pressure are adjusted according to the preset soot blowing control scheme.

Claims

1. A method for synchronously measuring boiler heating surface temperature and ash accumulation state based on LIP technology, characterized in that: The following steps are involved: (1) Phosphorescent material Y3Al5O 12 :Dy is mixed with a proper amount of high temperature glue to prepare a phosphorescent material spray; (2) spraying a spray on the surface of the calibration plate to form a phosphorescent coating, and placing the calibration plate in a black body furnace with an optical window; irradiating the calibration plate with an ultraviolet laser of a wavelength of 355 nm to excite and generate phosphorescent signals; using an image acquisition device to simultaneously acquire phosphorescent signal images of two characteristic wavelengths of 458 nm and 497 nm, and the coordinates on the two images correspond one to one; (3) continuously changing the inner cavity temperature of the black body furnace within the calibration range, and recording the phosphorescence signal images of the calibration plate at the two characteristic wavelengths in the absence of dust accumulation; then gradually changing the dust accumulation mass per unit area on the calibration plate under different temperature conditions, and collecting the phosphorescence signal images of the two characteristic wavelengths in each dust accumulation state; (4) performing intensity ratio calculation and fitting processing on the acquired phosphorescence signal image, and completing the calibration of the phosphorescence intensity ratio temperature-sensitive response curve and the phosphorescence signal intensity temperature-sensitive response curve at a characteristic wavelength of 458 nm under dust-free conditions; Taking the intensity of phosphorescence signal at 458nm wavelength of the dust-free heating surface as the normalization standard, the intensity ratio of phosphorescence signals obtained under different dust accumulation conditions was calculated and fitted, and the calibration of the dust accumulation response curve of phosphorescence signal intensity at 458nm wavelength under different temperature conditions was completed. (5) Spraying the same phosphorescent material spray on the dust-free surface of the heating surface inside the boiler to form a phosphorescent coating, and an optical window is provided on the boiler wall; while the boiler is running and gradually accumulating dust, irradiating the heating surface with an ultraviolet laser of a wavelength of 355 nm to stimulate the generation of phosphorescent signals, and using an image acquisition device to simultaneously acquire phosphorescent signal images of two characteristic wavelengths of 458 nm and 497 nm, and the coordinates on the two images correspond one to one; (6) After calculating the ratio of the phosphorescence signal images of two different characteristic wavelengths, the real-time two-dimensional temperature field of the boiler heating surface is obtained according to the calibrated phosphorescence intensity ratio temperature-sensitive response curve; based on the real-time temperature field data and the 458nm characteristic wavelength phosphorescence signal intensity temperature-sensitive response curve under the condition of no ash accumulation, the phosphorescence intensity signal value of the heating surface without ash accumulation under the corresponding temperature condition is obtained; this value is used as the normalization standard, and the intensity ratio is calculated with the collected phosphorescence signal image of the boiler heating surface at a wavelength of 458nm, and the ash accumulation amount response curve of the phosphorescence signal intensity under the corresponding temperature condition is compared to obtain the current ash accumulation amount on the heating surface inside the boiler.

2. The method according to claim 1, characterized in that The method further includes adjusting the soot blowing time node and the compressed air pressure according to a preset soot blowing control scheme based on the calculated value of the current soot accumulation on the internal heating surface of the boiler.

3. The method according to claim 1, characterized in that The ultraviolet laser used to excite and generate phosphorescent signals is obtained in the following manner: a timing synchronization controller is used to control the laser to emit 355nm ultraviolet laser, which is expanded into a planar light source through a beam expander composed of a concave lens and a convex lens, and then irradiated on the phosphorescent coating.

4. The method according to claim 1, characterized in that: The image acquisition device for simultaneously acquiring phosphorescence signal images of two characteristic wavelengths is a device that installs two narrow-band filters that respectively have the highest transmittance of the two characteristic wavelengths of 458nm and 497nm in front of the camera's imaging lens, ensuring that only the phosphorescence signals of these two characteristic wavelengths enter the camera's photosensitive device.

5. The method according to claim 1, characterized in that The step (3) of continuously changing the inner cavity temperature of the black body furnace within the calibration range refers to changing the inner cavity temperature of the black body furnace within the range of 300K to 1000K at intervals of 10K.

6. The method according to claim 1, characterized in that In the step (3), the calibration operation of the phosphorescence intensity ratio temperature-sensitive response curve specifically includes: The ratio of the average signal intensities of two phosphorescence signal images corresponding to different characteristic wavelengths obtained simultaneously at each temperature T is calculated to obtain the signal intensity ratio R of the two characteristic wavelengths under the temperature condition; the signals under all temperature conditions within the continuous change range are processed and calculated to obtain the response curve f1(R,T) of the signal ratio R to the temperature T, and the calibration of the temperature-sensitive response curve of the phosphorescence intensity ratio is completed.

7. The method according to claim 1, characterized in that In the step (3), the calibration operation of the temperature-sensitive response curve of the phosphorescence signal intensity at a characteristic wavelength of 458 nm under dust-free conditions specifically includes: The phosphorescence signal with a wavelength of 458 nm obtained at each temperature T was curve fitted to obtain the phosphorescence signal intensity I under the condition of no dust accumulation. x The response curve f2(I x ,T), complete the calibration of the temperature-sensitive response curve of the phosphorescence signal intensity at the characteristic wavelength of 458nm under dust-free conditions.

8. The method according to claim 1, characterized in that In the step (3), the calibration operation of the phosphorescence signal intensity dust accumulation response curve under different temperature conditions specifically includes: The calibration plate is evenly loaded with fly ash, with the fly ash mass per unit area m h As a quantitative value of the dust accumulation state; the calibration plate is placed in a black body furnace and the furnace is adjusted to a specific temperature T s Conditions; Based on each dust accumulation state m h The generated 458nm phosphorescence image G2 will have different average signal intensities I2; record the phosphorescence signal under fixed temperature conditions and specific dust accumulation conditions, and then calculate the ratio R of the signal intensity under the specific dust accumulation condition to the 458nm phosphorescence signal intensity under no dust accumulation. h =I2(T S ) / I x (T S ), and then curve fitting is performed to obtain the signal intensity ratio R h The response curve f3(R h ,m h ), complete the dust accumulation response curve of the phosphorescence signal intensity at 458nm wavelength under different temperature conditions.

9. A synchronous measurement system for boiler heating surface temperature and ash accumulation state based on LIP technology for implementing the method described in claim 1, characterized in that: The measuring system comprises: a laser generating device, an image acquisition device and a data processing device; wherein, The laser generating device comprises a timing synchronization controller, a laser and a beam expander; the beam expander is composed of a concave lens and a convex lens and is arranged on the laser optical path of the laser; The image acquisition device is two independent cameras, or a single camera with a stereo lens; a narrow-band filter with a specific wavelength is installed in front of the imaging lens of the camera; The data processing device is a host computer, including a central processing unit, a memory and a data transmission interface; The timing synchronization controller is connected to the laser and the image acquisition device respectively through signal lines, and the image acquisition device is connected to the data processing device through signal lines; the memory of the host computer is loaded with a software program, and the central processing unit can load the software program to perform the calculation work in the method described in claim 1.

10. The system according to claim 9, characterized in that The laser is a pulse laser or a continuous laser, and the laser energy is adjustable; the image acquisition device is a CCD camera, an enhanced CCD camera, a CMOS camera or an enhanced CMOS camera.

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