A method for simultaneous measurement of boiler heating surface temperature and ash accumulation based on LIP technology

Abstract

This invention relates to temperature measurement technology, aiming to provide a method for simultaneously measuring the temperature and ash accumulation status of boiler heating surfaces based on LIP technology. The method includes: irradiating a calibration plate in a blackbody furnace with an ultraviolet laser to generate a phosphorescent signal, simultaneously acquiring images of the phosphorescent signals at two characteristic wavelengths generated by the excitation, and completing calibration by changing the temperature and ash accumulation conditions; spraying the same phosphorescent material onto the ash-free surface of the boiler's internal heating surface to form a coating, and performing excitation and acquisition in the same manner during boiler operation and gradual ash accumulation; calculating the real-time two-dimensional temperature field of the heating surface and the current amount of ash accumulation on the boiler's internal heating surface based on the calibration curve. This invention requires only one set of equipment to simultaneously achieve two-dimensional temperature field measurement and ash accumulation status determination; the phosphorescent coating can be recycled on the boiler's heating surface, making it more economical; the measurement is not affected by the radiation properties of the object itself or environmental factors, and does not disrupt the internal thermal balance of the boiler; the measurement method is simpler and more accurate.

Description

Technical Field

[0001] This invention relates to the field of temperature measurement technology, and in particular to a method for simultaneously measuring the temperature and ash accumulation status of boiler heating surfaces based on laser-induced phosphorescence. Background Technology

[0002] Boilers are core power equipment in industries such as power, petrochemicals, metallurgy, building materials, and light industry. Timely acquisition of surface temperature information and ash accumulation data of boiler heating surfaces is crucial for the safe and economical operation of various power equipment. Existing technologies for measuring the temperature of solid surfaces like boiler heating surfaces can be divided into contact and non-contact temperature measurement methods. Contact temperature measurement methods, represented by thermocouples, suffer from drawbacks such as limited point measurement, slow response, and complex maintenance. Non-contact temperature measurement methods mainly include passive radiation thermometry and active laser thermometry. Passive radiation thermometry is widely used in engineering, but due to the uncertain emissivity of the object surface and the interference of background thermal radiation, it is difficult to achieve accurate temperature measurement in complex thermal environments.

[0003] In recent years, the rapid development of laser technology has led to significant attention being paid to laser-based online temperature field measurement technology. Active laser thermometry, represented by laser-induced phosphorescence (LIP), is a non-contact optical thermometry technique that measures temperature based on the temperature-sensitive phosphorescent signal generated by an excited phosphorescent coating on a target surface. By spraying a phosphorescent material onto the surface of the target and exciting it with a laser of a specific wavelength, electrons transition from the ground state to a higher energy state. When these electrons return to the ground state, the emitted photons are phosphorescence. The phosphorescence lifetime or characteristic spectral intensity ratio is temperature-sensitive; therefore, by calibrating and obtaining the phosphorescence characteristic spectral intensity ratio or lifetime versus temperature function calibration curve, solid surface temperature field measurements can be performed. Since the phosphorescence signal is independent of the material properties of the target surface and possesses multiple characteristic emission wavelengths, laser-induced phosphorescence thermometry is unaffected by unknown target emissivity and background thermal radiation, offering advantages such as high measurement accuracy, fast response, wide temperature range, and the ability to perform two-dimensional temperature field measurements.

[0004] During combustion, boilers continuously generate dust, which is adsorbed and retained on the inner wall of the furnace, becoming ash. Because ash has a very low thermal conductivity, its presence on the boiler's heating surfaces affects heat transfer, leading to a decrease in the temperature of the heat-absorbing medium and an increase in the flue gas temperature, thus reducing boiler thermal efficiency. Severe ash accumulation can reduce the cross-sectional area of ​​the flue gas flow, increase flow resistance, increase the power consumption of the induced draft fan, reduce the boiler's operating load, and even force a shutdown. Ash accumulation can also raise the temperature of the downstream flue gas, affecting the safe operation of the tail-end heating surfaces. If ash accumulation is severe in certain areas, it can even form a "flue gas corridor," causing increased wear and tear on the local heating surfaces due to increased flue gas velocity. Therefore, it is necessary to install a soot blowing device inside the boiler and periodically introduce compressed air to clean the boiler's heating surfaces. In current operations, compressed air or steam is typically introduced by periodically opening and closing valves on the gas line. However, the degree of ash accumulation on the boiler's heating surfaces does not change linearly with variations in production load, combustible composition, and combustion atmosphere. If a timed air blowing program is set based on experience, the following situations may occur: when there is little ash accumulation, too much air is blown, wasting compressed air and steam and affecting combustion; when there is a lot of ash accumulation, insufficient air is blown, making timely cleaning difficult and causing the ash accumulation to worsen. Therefore, measuring the degree of ash accumulation on the boiler's heating surfaces and adjusting the air blowing volume or frequency in a timely manner based on the measurement results is a necessary measure to ensure the efficient operation of the boiler.

[0005] In existing technologies, the degree of ash accumulation is typically estimated or predicted by indirectly measuring heat transfer parameters related to ash accumulation. Among these, the furnace outlet flue gas temperature is a relatively mature parameter for predicting the degree of ash accumulation on heated surfaces. However, this method only infers the process from the result; that is, ash accumulation on the heated surface leads to deteriorated heat transfer, causing a further increase in the furnace outlet flue gas temperature. This method struggles to accurately predict the timing of soot blowing on the heated surface and cannot obtain the ash accumulation status of local heated surfaces. Furthermore, newer methods, such as those using image processing technology to directly observe the ash condition of heated surfaces, can effectively obtain local ash accumulation information. However, these methods usually require calibration of the camera coordinate system and the furnace coordinate system, as well as 3D reconstruction of feature points, making the process complex. This is particularly problematic when the ash accumulation is small in the early stages of ash accumulation, hindering rapid judgment and early warning.

[0006] Although the surface temperature and ash accumulation of the heating surface are both measured simultaneously around the boiler equipment, existing technologies treat these two measurements as independent processes, typically employing two separate measurement schemes. This results in drawbacks for measurement systems around the boiler heating surface, including complex structure, high overall cost, interference from background thermal radiation, unknown furnace emissivity, and the inability to provide early warning of ash accumulation.

[0007] In view of the above situation, the present invention aims 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 shortcomings of the prior art and provide a method for synchronously measuring the temperature and ash accumulation status of boiler heating surfaces based on LIP technology.

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

[0010] A method for simultaneously measuring boiler heating surface temperature and ash accumulation status based on LIP technology is provided, including the following steps:

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

[0012] (2) Spray a spray agent on the surface of the calibration plate to form a phosphorescent coating, and place it in a blackbody furnace with an optical window; irradiate the calibration plate with an ultraviolet laser with a wavelength of 355nm to generate a phosphorescent signal; use an image acquisition device to simultaneously acquire phosphorescent signal images of two characteristic wavelengths, 458nm and 497nm, and the coordinates on the two images correspond one-to-one.

[0013] (3) Continuously change the internal temperature of the blackbody furnace within the calibration range and record the phosphorescence signal images of the two characteristic wavelengths of the calibration plate under the condition of no ash accumulation; then, under different temperature conditions, gradually change the ash accumulation mass per unit area on the calibration plate and collect the phosphorescence signal images of the two characteristic wavelengths under each ash accumulation state.

[0014] (4) The intensity ratio of the acquired phosphorescent signal image is calculated and fitted, and the temperature-sensitive response curve of phosphorescent intensity ratio and the temperature-sensitive response curve of phosphorescent signal intensity at 458 nm characteristic wavelength under no-ash conditions are calibrated respectively. The intensity of phosphorescent signal at 458 nm wavelength on the no-ash heated surface is used as the normalization standard, and the intensity ratio of the phosphorescent signal acquired under different ash conditions is calculated and fitted, and the calibration of the ash amount response curve of phosphorescent signal intensity at 458 nm wavelength under different temperature conditions is completed.

[0015] (5) Spray the same phosphorescent material on the non-ash-accumulated surface of the heating surface inside the boiler to form a phosphorescent coating. The boiler wall is provided with an optical window. During the operation of the boiler and the gradual accumulation of ash, the heating surface is irradiated with an ultraviolet laser with a wavelength of 355nm to generate phosphorescent signals. The phosphorescent signal images of the two characteristic wavelengths of 458nm and 497nm are simultaneously acquired by an image acquisition device, and the coordinates on the two images correspond one-to-one.

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

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

[0018] As a preferred embodiment of the present invention, the ultraviolet laser used to excite and generate phosphorescent signals is obtained by means of: controlling the laser to emit 355nm ultraviolet laser with a timing synchronization controller, expanding it into a planar light source through a beam expander composed of concave and convex lenses, and then irradiating the phosphorescent coating.

[0019] As a preferred embodiment of the present invention, the image acquisition device for simultaneously acquiring phosphorescent signal images of two characteristic wavelengths is provided by installing two narrowband filters in front of the imaging lens of the camera, which respectively maximize the transmittance of the two characteristic wavelengths of 458nm and 497nm, to ensure that only phosphorescent signals of these two characteristic wavelengths enter the camera's photosensitive device.

[0020] As a preferred embodiment of the present invention, the continuous change of the internal temperature of the blackbody furnace within the calibration range in step (3) refers to changing the internal temperature of the blackbody furnace within the range of 300K to 1000K at intervals of 10K.

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

[0022] The ratio of the average signal intensity of two phosphorescent 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 that temperature condition; the signals under all temperature conditions within the continuous range are processed and calculated to obtain the response curve f1(R,T) of the signal ratio R with temperature T, and the temperature-sensitive response curve of the phosphorescence intensity ratio is calibrated.

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

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

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

[0026] The calibration plate is evenly loaded with fly ash, with fly ash mass m per unit area. h As a quantitative value for the ash accumulation state; the calibration plate is placed in the blackbody furnace, and the furnace is adjusted to a specific temperature T. s Conditions; based on each ash accumulation state m h The resulting 458nm phosphorescent image G2 will have different average signal intensities I2; the phosphorescent signals under fixed temperature conditions and specific dust accumulation states are recorded, and then the ratio R of the signal intensity under the specific dust accumulation state to the 458nm phosphorescent signal intensity without dust accumulation is calculated. h =I2(T S ) / I x (T S Then, curve fitting is performed to obtain the signal intensity ratio R. h Response curve f3(R) as a function of average dust accumulation h ,m h The response curves of phosphorescent signal intensity and ash accumulation at a wavelength of 458 nm under different temperature conditions were obtained.

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

[0028] The laser generating device includes 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 in the laser beam path of the laser.

[0029] The image acquisition device consists of two independent cameras or a single camera equipped with a stereo lens; a narrowband filter of a specific wavelength is installed in front of the camera's imaging lens.

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

[0031] The timing synchronization controller is connected to the laser and the image acquisition device via signal lines, and the image acquisition device is connected to the data processing device via signal lines. The host computer's memory contains a software program, and the central processing unit can load the software program to perform the calculations in the aforementioned 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 electromagnetic radiation or ion beam excitation. During long-term in-depth research, the applicant discovered that the phosphorescent material exhibits a temperature-sensitive characteristic with a monotonic change in the ratio of phosphorescence intensity at its two characteristic emission peaks of 458 nm and 497 nm. Based on this discovery, the applicant proposed the innovative technical solution of this application.

[0035] The technical solution of this invention is based on laser-induced phosphorescence technology to achieve simultaneous 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 phosphorescence signals. These signals are then acquired using an image acquisition device. Based on the temperature-sensitive characteristics of the phosphorescence spectral signals, and using the phosphorescence signal intensity value of the ash-free heating surface as a normalization standard, the invention simultaneously achieves two-dimensional temperature field measurement and ash accumulation status determination of the boiler heating surface.

[0036] After in-depth theoretical research and experimental verification, the applicant's research team discovered that the phosphorescence intensity ratio method based on laser-induced phosphorescence technology is unaffected by the unknown emissivity of the target and background thermal radiation; the temperature measurement result depends only on the temperature of the surface being measured. Therefore, this invention selects Y3Al5O, a phosphorescent material suitable for the phosphorescence intensity ratio method. 12 The temperature-sensitive characteristic of this material is that when excited by a laser of a specific wavelength of 355nm, it produces two characteristic wavelengths: 458nm and 497nm. Furthermore, the intensity ratio of these two wavelengths exhibits a monotonic change with temperature. By calibrating the monotonic functional relationship between the ratio of these two characteristic wavelengths and temperature, the two-dimensional temperature field information of the measured surface can be obtained in an engineering environment by reverse derivation based on the monotonic functional relationship and the measured ratio of the two characteristic wavelengths.

[0037] Meanwhile, the changes in the phosphorescence signal generated after the phosphorescent coating is excited are mainly determined by temperature and the state of dust accumulation, with secondary factors including background scattering. Since the phosphorescence signal shows a monotonically decreasing trend with increasing dust accumulation, and the use of ratio calculation can reduce the interference of other factors such as background scattering, the dust accumulation state determination result is ultimately determined solely by the degree of dust accumulation.

[0038] Before applying this invention to practical engineering, it is necessary to first use a calibration plate with a phosphorescent coating and a blackbody furnace with an optical window to perform calibration work based on laser irradiation and phosphorescent signal recording. This involves calibrating the temperature-sensitive response curves of the phosphorescence intensity ratio, the temperature-sensitive response curves of the phosphorescence signal intensity at 458 nm wavelength under ash-free conditions, and the ash accumulation response curves of the phosphorescence signal intensity at 458 nm wavelength under different temperature conditions. Based on this, the invention can be applied to practical engineering applications involving the simultaneous measurement of boiler heating surface temperature and ash accumulation status.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] 1. After the phosphorescent coating is applied to the measuring area of ​​the boiler heating surface, this invention only requires one set of equipment to simultaneously measure the two-dimensional temperature field of the heating surface and determine the ash accumulation. Furthermore, due to the high temperature resistance and high adhesion of the phosphorescent coating, the phosphorescent coating used in this invention can be recycled on the boiler heating surface, making it more economical.

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

[0042] 3. In this invention, the ash state of the boiler heating surface is measured based on the attenuation of phosphorescent signals. It has high sensitivity and higher ash accumulation perception capability compared with the existing direct observation method, enabling timely early warning of the ash accumulation progress.

[0043] 4. Based on the use of this invention, the blowing strategy can be flexibly adjusted according to the ash accumulation in actual production, saving compressed air and steam while better avoiding the impact on the stable operation of the boiler. Attached Figure Description

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

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

[0046] Figure 3 The phosphorescence intensity ratio temperature-sensitive response curve is shown in the embodiment of the present invention.

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

[0048] Figure 5 The graph shows the response of the phosphorescence signal intensity ratio at 458 nm wavelength under 300 K conditions to the amount of ash accumulation.

[0049] Figure 6 The graph shows the response curve of the phosphorescence signal intensity ratio at 458 nm wavelength under 774 K conditions as a function of the amount of ash accumulation.

[0050] Figure labels: 1. Calibration plate; 2. Thermal environment (blackbody furnace during calibration, boiler 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 Implementation

[0051] The specific embodiments of the present invention will be described in detail below with reference to 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 way. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all of them. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and all such modifications and improvements should fall within the protection scope of the present invention.

[0052] Part One: Implementation Scheme of the Invention

[0053] 1. Structural layout of the measurement system

[0054] To achieve the measurement objective of this invention, it is first necessary to build a system for calibration and measurement. Except for the object being measured, all other components of this system are reused.

[0055] The measurement system includes a laser generator, an image acquisition device, and a data processing device. The laser generator comprises a timing synchronization controller, a laser, and a beam expander. The beam expander consists of a concave lens and a convex lens, arranged in the laser beam path of the laser. The image acquisition device consists of two independent cameras, or a single camera equipped with a stereo lens. A narrowband filter of a specific wavelength is installed in front of the camera's imaging lens. 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 via signal lines, and the image acquisition device is connected to the data processing device via signal lines. The host computer's memory contains a software program, which the central processing unit can load to execute the calculations in the measurement method described in this 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. Operational procedures for the measurement method

[0058] The method for synchronously measuring boiler heating surface temperature and ash accumulation status based on LIP technology described in this invention includes two main parts: calibration operation and actual measurement operation, as detailed below:

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

[0060] (2) Spray an aerosol onto the surface of the calibration plate to form a phosphorescent coating, and place it in a blackbody furnace (or boiler) 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 by a beam expander composed of concave and convex lenses, and then irradiates the phosphorescent coating to generate a phosphorescent signal.

[0061] Narrowband filters with center wavelengths of 458nm and 497nm were installed in front of the camera's imaging lens in the image acquisition device to ensure that only phosphorescent signals of these two characteristic wavelengths enter the camera's photosensitive device. The image acquisition device simultaneously acquires images of these two characteristic wavelength phosphorescent signals, and the coordinates of the two images correspond one-to-one.

[0062] (3) Calibration operation:

[0063] Within a calibrated range (e.g., in 10K intervals, between 300K and 1000K), the internal temperature of the blackbody furnace was continuously varied, and phosphorescence signal images of two characteristic wavelengths were recorded under no-ash-accumulation conditions. Then, under different temperature conditions, the ash accumulation mass per unit area on the calibration plate was gradually changed, and phosphorescence signal images of two characteristic wavelengths were acquired under each ash-accumulation condition.

[0064] (4) The intensity ratio of the acquired phosphorescent signal images was calculated and fitted to calibrate the phosphorescence intensity ratio temperature-sensitive response curve and the temperature-sensitive response curve of the phosphorescence signal intensity at the characteristic wavelength of 458 nm under no-ash accumulation conditions. Using the phosphorescence signal intensity at a wavelength of 458 nm on a no-ash-accumulation heated surface as a normalization standard, the intensity ratio of the phosphorescence signals at the same characteristic wavelength acquired under different ash accumulation conditions was calculated and fitted to calibrate the ash accumulation response curve of the phosphorescence signal intensity at the characteristic wavelength of 458 nm under different temperature conditions; among which,

[0065] (4.1) The calibration procedure for the phosphorescence intensity ratio temperature-sensitive response curve includes:

[0066] The ratio of the average signal intensity of two phosphorescent 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 that temperature condition; the signals under all temperature conditions in the continuous range are processed and calculated to obtain the response curve f1(R,T) of the signal ratio R with temperature T, and the temperature-sensitive response curve of the phosphorescence intensity ratio is calibrated.

[0067] (4.2) Calibration of the temperature-sensitive response curve of the phosphorescence signal intensity at the characteristic wavelength of 458nm under dust-free conditions, specifically including:

[0068] Curve fitting was performed on the phosphorescence signal at a characteristic wavelength of 458 nm obtained at each temperature T to obtain the phosphorescence signal intensity I of the dust-free calibration plate. x The response curve f2(I) with temperature T x The temperature-sensitive response curve of the phosphorescence signal intensity at the characteristic wavelength of 458nm under dust-free conditions was calibrated.

[0069] (4.3) Calibration of the phosphorescence signal intensity and dust accumulation response curves at a characteristic wavelength of 458 nm under different temperature conditions, specifically including:

[0070] The calibration plate is evenly loaded with fly ash, with fly ash mass m per unit area. h As a quantitative value for the ash accumulation state; the calibration plate is placed in the blackbody furnace, and the furnace is adjusted to a specific temperature T. s Conditions; based on each ash accumulation state m h The resulting phosphorescent image G2 will have different average signal intensities I2; the phosphorescent signals under fixed temperature conditions and specific dust accumulation states are recorded, and then the ratio R of the signal intensity under the specific dust accumulation state to the phosphorescent signal intensity without dust accumulation is calculated. h =I2(T S ) / I x (T S Then, curve fitting is performed to obtain the signal intensity ratio R. h Response curve f3(R) as a function of average dust accumulation h ,m h The response curves of phosphorescent signal intensity and ash accumulation at the characteristic wavelength of 458nm under different temperature conditions were completed.

[0071] (5) Actual test operation: The phosphorescent material spray is sprayed on the non-ash-accumulated surface of the heating surface inside the boiler to form a phosphorescent coating. The boiler wall is provided with an optical window. During the operation of the boiler and the gradual accumulation of ash, the heating surface is irradiated with a 355nm ultraviolet laser to excite the generation of phosphorescent signals. The phosphorescent signal images at two characteristic wavelengths of 458nm and 497nm are simultaneously acquired using an image acquisition device, and the coordinates on the two images correspond one-to-one.

[0072] (6) After calculating the ratio of two phosphorescence images with 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 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 phosphorescence intensity signal image of the same characteristic wavelength of the boiler heating surface; by referring to the phosphorescence signal intensity ash accumulation response curve under the corresponding temperature condition, the amount of ash accumulation on the heating surface inside the boiler is obtained.

[0073] (7) After calculating the amount of ash accumulation on the heating surface inside the boiler, the soot blowing time and compressed air pressure can be adjusted according to the preset soot blowing control scheme to maximize the overall energy efficiency.

[0074] Part Two: A Specific Implementation Case

[0075] The calibration device provided in this embodiment is as follows: Figure 1 As shown, the measuring device is as follows Figure 2 As shown. The image acquisition device used was an ICCD camera (i.e., an enhanced CCD camera). The processing and calculation of image signal data were implemented using software programs installed on the host computer 8. This part is a conventional technical method and is not the focus of this invention, so it will not be described in detail.

[0076] The complete process of calibration and measurement operations is illustrated below:

[0077] (1) Phosphorescent material Y3Al5O 12 A phosphorescent material spray is prepared by mixing Dy and high-temperature adhesive in a certain proportion and spraying it onto the surface of calibration plate 1 to form a phosphorescent coating. Calibration plate 1 is placed in the inner cavity of blackbody furnace 2, and the furnace wall is provided with an optical window.

[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 shines on the phosphorescent coating of the calibration plate 1 in the form of a planar light source and generates a phosphorescent signal.

[0079] (3) The first ICCD camera 6 and the second ICCD camera 7 (or reference) Figure 2 The first ICCD camera 6) with a stereo lens 9 is aligned with the optical window of the blackbody furnace. By installing narrowband filters with center wavelengths of 458nm and 497nm in front of the imaging lens, it is possible to simultaneously acquire phosphorescent signal images of two characteristic wavelengths and make the coordinates of the two images correspond one-to-one.

[0080] (4) The internal temperature of the blackbody furnace 2 is changed in 10K intervals within the range of 300K to 1000K. The phosphorescence signal image at each temperature is recorded by the CCD camera and transmitted to the host computer 8 for processing. The ratio of the average signal intensities I1 and I2 of the two phosphorescence images G1 and G2 obtained simultaneously at each temperature T at different characteristic wavelengths is calculated to obtain the phosphorescence signal intensity ratio R = I1 / I2 at that temperature. The signal processing at all temperatures is completed to obtain the response curve f1(R,T) of the phosphorescence signal ratio R with temperature T. The temperature-sensitive curve calibration of the phosphorescence intensity ratio is completed, and the obtained response curve is shown in Figure 1. Figure 3 As shown.

[0081] (5) Select the phosphorescence signal I2 of the 458nm characteristic emission peak acquired 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 I of the dust-free calibration plate. 458 The response curve f2(I) with temperature T 458 The intensity calibration of the 458nm phosphorescent signal was completed under dust-free conditions (T), and the resulting response curve is shown in Figure 1. Figure 4 As shown.

[0082] (6) Evenly load the calibration plate with fly ash, with fly ash mass m per unit area. h As a quantitative value of the ash accumulation state; the calibration plate is placed in a blackbody furnace at a specific temperature T inside the furnace. s Under the condition, based on each ash accumulation state m h The resulting phosphorescent image G2 will have different average signal intensities I2; the phosphorescent signals under fixed temperature conditions and specific dust accumulation states are recorded, and then the ratio R of the signal intensity under the specific dust accumulation state to the phosphorescent signal intensity without dust accumulation is calculated. h =I2(T S ) / I 458 (T S Then perform curve fitting to obtain the ratio R. h Response curve f3(R) with average dust accumulation h ,m h This allows for the calibration of the dust accumulation response curves for phosphorescence signal intensity under different temperature conditions. For example, Figure 5 and Figure 6 The graphs show the response of the phosphorescence signal intensity ratio at 458 nm as a function of ash accumulation per unit area at 300 K and 774 K, respectively. The latter is an example of boiler operating temperature conditions.

[0083] (7) The phosphorescent material spray prepared in step (1) is sprayed onto the ash-free surface of the boiler heating surface to form a phosphorescent coating, and the furnace wall surface is provided with an optical window.

[0084] (8) The first ICCD camera 6 (or reference) equipped with stereo lens 9 Figure 1 Two ICCD cameras were used to target the optical windows of the boiler, and narrowband filters with center wavelengths of 458nm and 497nm were installed in front of the imaging lenses. During the boiler operation and gradual ash accumulation, the heated surface was irradiated with a 355nm ultraviolet laser to excite phosphorescence signals; at the same time, two characteristic wavelength phosphorescence signal images, namely G3 and G4, were acquired, and the coordinates of the two images corresponded one-to-one.

[0085] (9) The phosphorescent signal image is recorded by the CCD camera and transmitted to the host computer 8 for processing. The ratio of the two phosphorescent images G3 and G4 with different characteristic wavelengths is calculated to obtain the phosphorescent signal intensity ratio R = I3 / I4 of the two characteristic wavelengths. Based on the calibrated phosphorescent 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) of the phosphorescence signal intensity at a characteristic wavelength of 458 nm under ash-free conditions. 458 The phosphorescence intensity signal of the dust-free heated surface at that temperature is obtained. Using this value as a normalization standard, the phosphorescence signal G4 of the 458nm emission peak collected in step (9) is selected as the detection source to obtain its phosphorescence intensity signal I4. The ratio R of the phosphorescence intensity signal under dust-free conditions is calculated. h =I4 / I 458 (T); Based on the ash accumulation state calibration plate phosphorescence signal intensity response curve f3(R) obtained in step (6) under the corresponding temperature conditions, determine the phosphorescence signal intensity response curve f3(R). h ,m h The amount of ash accumulated on the heating surface inside the boiler is calculated.

[0087] (11) Based on the values ​​obtained in step (9), adjust the soot blowing time nodes and compressed air pressure according to the preset soot blowing control scheme.

Claims

1. A method for synchronously measuring boiler heating surface temperature and ash accumulation status based on LIP technology, characterized in that, Includes the following steps: (1) Phosphorescent material Y3Al5O 12 :Dy is mixed with an appropriate amount of high-temperature adhesive to prepare a phosphorescent material spray; (2) Spray a spray agent on the surface of the calibration plate to form a phosphorescent coating, and place it in a blackbody furnace with an optical window; irradiate the calibration plate with an ultraviolet laser with a wavelength of 355nm to generate a phosphorescent signal; use an image acquisition device to simultaneously acquire phosphorescent signal images of two characteristic wavelengths, 458nm and 497nm, and the coordinates on the two images correspond one-to-one. (3) Continuously change the internal temperature of the blackbody furnace within the calibration range and record the phosphorescence signal images of the two characteristic wavelengths of the calibration plate under the condition of no ash accumulation; then, under different temperature conditions, gradually change the ash accumulation mass per unit area on the calibration plate and collect the phosphorescence signal images of the two characteristic wavelengths under each ash accumulation state. (4) The intensity ratio of the acquired phosphorescent signal image is calculated and fitted, and the temperature-sensitive response curve of phosphorescent intensity ratio and the temperature-sensitive response curve of phosphorescent signal intensity at a characteristic wavelength of 458nm under no-dust conditions are calibrated respectively. Using the phosphorescence signal intensity at a wavelength of 458 nm on a dust-free heated surface as a normalization standard, the intensity ratio of phosphorescence signals obtained under different dust accumulation conditions was calculated and fitted to complete the calibration of the response curve of phosphorescence signal intensity at a wavelength of 458 nm under different temperature conditions. (5) Spray the same phosphorescent material on the non-ash-accumulated surface of the heating surface inside the boiler to form a phosphorescent coating. The boiler wall is provided with an optical window. During the operation of the boiler and the gradual accumulation of ash, the heating surface is irradiated with an ultraviolet laser with a wavelength of 355nm to generate phosphorescent signals. The phosphorescent signal images of the two characteristic wavelengths of 458nm and 497nm are simultaneously acquired by an image acquisition device, and the coordinates on the two images correspond one-to-one. (6) After calculating the ratio of two phosphorescent signal images with different characteristic wavelengths, the real-time two-dimensional temperature field of the boiler heating surface is obtained according to the calibrated phosphorescent intensity ratio temperature-sensitive response curve. Based on the real-time temperature field data and the temperature-sensitive response curve of the phosphorescent signal intensity of the 458nm characteristic wavelength under no-ash conditions, the phosphorescent intensity signal value of the heating surface without ash under the corresponding temperature conditions is obtained. This value is used as the normalization standard and the intensity ratio is calculated with the collected phosphorescent signal image of the boiler heating surface at a wavelength of 458nm. By referring to the phosphorescent signal intensity ash accumulation response curve under the corresponding temperature conditions, the amount of ash accumulation on the heating surface inside the boiler is obtained.

2. The method according to claim 1, characterized in that, The method further includes adjusting the soot blowing time and compressed air pressure according to a preset soot blowing control scheme based on the calculated amount of ash accumulated on the heating surface inside the boiler.

3. The method according to claim 1, characterized in that, The ultraviolet laser used to excite and generate phosphorescent signals is obtained by controlling the laser to emit 355nm ultraviolet laser with a timing synchronization controller, expanding it into a planar light source through a beam expander composed of concave and convex lenses, and then irradiating the phosphorescent coating.

4. The method according to claim 1, characterized in that, The image acquisition device for simultaneously acquiring phosphorescent signal images of two characteristic wavelengths consists of two narrowband filters installed in front of the camera's imaging lens, which respectively maximize the transmittance of the two characteristic wavelengths, 458nm and 497nm, ensuring that only phosphorescent signals of these two characteristic wavelengths enter the camera's photosensitive device.

5. The method according to claim 1, characterized in that, The continuous change of the internal temperature of the blackbody furnace within the calibration range mentioned in step (3) refers to changing the internal temperature of the blackbody furnace within the range of 300K to 1000K at intervals of 10K.

6. The method according to claim 1, characterized in that, In step (3), the calibration operation of the phosphorescence intensity ratio temperature-sensitive response curve specifically includes: The ratio of the average signal intensity of two phosphorescent 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 that temperature condition; the signals under all temperature conditions within the continuous range are processed and calculated to obtain the response curve f1(R,T) of the signal ratio R with temperature T, and the temperature-sensitive response curve of the phosphorescence intensity ratio is calibrated.

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

8. The method according to claim 1, characterized in that, In step (3), the calibration operation of the phosphorescence signal intensity and ash accumulation response curves under different temperature conditions specifically includes: The calibration plate is evenly loaded with fly ash, with fly ash mass m per unit area. h As a quantitative value for the ash accumulation state; the calibration plate is placed in the blackbody furnace, and the furnace is adjusted to a specific temperature T. s Conditions; based on each ash accumulation state m h The resulting 458nm phosphorescent image G2 will have different average signal intensities I2; the phosphorescent signals under fixed temperature conditions and specific dust accumulation states are recorded, and then the ratio R of the signal intensity under the specific dust accumulation state to the 458nm phosphorescent signal intensity without dust accumulation is calculated. h =I2(T S ) / I x (T S Then, curve fitting is performed to obtain the signal intensity ratio R. h Response curve f3(R) as a function of average dust accumulation h ,m h The response curves of phosphorescent signal intensity and ash accumulation at a wavelength of 458 nm under different temperature conditions were obtained.

9. A boiler heating surface temperature and ash accumulation state synchronous measurement system based on LIP technology for implementing the method of claim 1, characterized in that, The measurement system includes: a laser generator, an image acquisition device, and a data processing device; wherein, The laser generating device includes 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 in the laser beam path of the laser. The image acquisition device consists of two independent cameras or a single camera equipped with a stereo lens; a narrowband filter of a specific wavelength is installed in front of the camera's imaging lens. A data processing device is a host computer, including a central processing unit, memory, and data transmission interface; The timing synchronization controller is connected to the laser and the image acquisition device via signal lines, and the image acquisition device is connected to the data processing device via signal lines; the host computer's memory contains a software program, and the central processing unit can load the software program to perform the calculation work in the method of claim 1.

10. The system according to claim 9, characterized in that, 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.

Images