Soot blowing system leakage detection system and method based on acoustic spectrum analysis

Abstract

The invention discloses a soot blowing system leakage detection system and method based on acoustic spectrum analysis, the detection system comprises a soot blowing system and an acoustic leakage detection system, the soot blowing system comprises a soot blowing medium mother pipe, a lifting valve, a soot blower inner pipe, a soot blowing gun pipe and the like, an inlet of the lifting valve is installed on the soot blowing medium mother pipe, and an outlet of the lifting valve is installed on the soot blowing gun pipe; an outlet of the lifting valve is connected with the soot blowing gun pipe through the soot blower inner pipe, and a soot blowing nozzle is arranged on the soot blowing gun pipe. The acoustic leakage detection system is installed on the soot blower inner tube between the outlet of the lift valve and the soot blowing gun tube, and comprises an upper cover plate, an acoustic resonance cavity, a sound pressure collecting tube, a sound guide tube, a lower cover plate and a high-frequency microphone. The number of the acoustic resonance cavities is generally 3-6, the volumes of the cavities are different, the acoustic resonance cavities have different resonance frequencies, and the range of the resonance frequencies is 20-50 kHz. When the lift valve leaks, the measured sound pressure level is increased, the proportion of high-frequency sound power higher than 20 kHz is also increased, the indexes can help to accurately identify leakage, and the running safety of the soot blower is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of boilers, and in particular to a sootblowing system leakage detection system and method based on acoustic spectrum analysis. Background Art

[0002] Sootblowers are important components of power station boilers. A large number of sootblowers are installed in the furnace water-cooled walls, superheaters, reheaters, economizers and air preheaters. They are operated regularly to clean the heating surfaces to ensure safe and economical operation of the boiler.

[0003] Sootblowers generally use high-pressure steam or compressed air as the sootblowing medium, with a pressure of 0.7-1.5MPa. After being accelerated by the Rafale nozzle, they have a strong blowing ability, but they also have a certain blowing damage effect on the heating surface. Usually, the sootblowers are started regularly and closed after blowing for a few minutes, which will not cause blowing damage to the heating surface. However, if the lifting valve in the sootblower system leaks internally, the heating surface will be continuously blown by steam or compressed air, which will waste a lot of energy on the one hand, and on the other hand, it is very easy to cause accidents such as pipe bursts under long-term blowing.

[0004] For a long time, factors such as improper sootblower purge and internal leakage of poppet valves have caused many boiler tube burst accidents, resulting in boiler shutdown and huge economic losses. Therefore, how to effectively detect sootblowing system leakage has become a major problem for safe operation of boilers. Some manufacturers install thermocouples at poppet valves and other places for leakage detection. However, on the one hand, the temperature change when internal leakage occurs is not obvious, and on the other hand, if the sootblowing medium is compressed air, this method is ineffective. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the purpose of the present application is to provide a sootblowing system leakage detection system and method based on acoustic spectrum analysis.

[0006] The technical solution adopted by the present invention is as follows: A sootblowing system leakage detection system based on acoustic spectrum analysis comprises a sootblowing system and an acoustic leakage detection system; the sootblowing system comprises a sootblowing medium main pipe, a lifting valve, a sootblower inner pipe and a sootblowing gun barrel, the inlet of the lifting valve is installed on the sootblowing medium main pipe, the outlet of the lifting valve is connected to the sootblowing gun barrel through the sootblower inner pipe, and the sootblowing gun barrel is provided with a sootblowing nozzle for generating a high-speed jet.

[0007] The acoustic leakage detection system is installed on the inner tube of the sootblower, that is, the outside of the pipeline between the outlet of the lifting valve and the sootblowing gun tube. The acoustic leakage detection system collects the acoustic signal passing through the inner tube of the sootblower and performs mathematical analysis to detect internal leakage of the lifting valve.

[0008] Furthermore, the acoustic leakage detection system includes an upper cover plate, an acoustic resonance chamber, a sound pressure collecting pipe, a sound guide pipe, a lower cover plate and a high-frequency microphone. The upper cover plate is provided with a row of multiple acoustic resonance chambers, and all the acoustic resonance chambers are connected to the sound pressure collecting pipe through pipes respectively. The sound pressure collecting pipe is connected to the sound guide pipe, and the high-frequency microphone is arranged at one end of the sound guide pipe away from the sound pressure collecting pipe. The upper cover plate and the lower cover plate are spliced ​​and fixed together and are sleeved on the outer side of the side of the inner pipe of the soot blower, and are in contact and connected with the inner pipe of the soot blower.

[0009] Furthermore, the upper cover plate and the lower cover plate are both semicircular tubular, and the upper cover plate and the lower cover plate are spliced ​​to form a sleeve structure, and are fitted on the side outer wall of the sootblower inner tube; the upper cover plate and the lower cover plate are connected to the sootblower inner tube by welding or clamping.

[0010] Furthermore, the number of acoustic resonance cavities is generally 3-6, and their cavity volumes are different, so they have different resonant frequencies, and the resonant frequency range is 20-50 kHz.

[0011] Furthermore, the sound guide tube is made of stainless steel, with a diameter of no more than 20 mm and a length of no less than 1000 mm, and no surface insulation to prevent the high temperature generated when the soot blowing medium is high-temperature steam from adversely affecting the high-frequency microphone. The frequency response range of the high-frequency microphone is 200-50000 Hz.

[0012] Sootblowing system leak detection system based on acoustic spectrum analysis, which is applicable whether the sootblowing medium is steam or compressed air.

[0013] The present invention provides a sootblowing system leakage detection method based on acoustic spectrum analysis, and its principle and detection method are as follows: (1) An acoustic leakage detection system is installed on the inner tube of the sootblower between the outlet of the lifting valve and the sootblowing gun tube. If the lifting valve has an internal leakage, the generated airflow will generate a significant high-frequency acoustic signal at this position, which can be detected.

[0014] (2) The upper cover of the leakage detection equipment is provided with 3-6 acoustic resonance chambers of different volumes, with a resonance frequency range of 20-50 kHz, which are used to amplify the mid- and high-frequency parts of the audio.

[0015] (3) The audio signals of several acoustic resonance chambers are collected through the sound pressure collecting tube, and then connected to the high-frequency microphone through the sound guide tube. When the sootblowing medium is high-temperature steam, the temperature inside the sootblower tube can reach more than 200 degrees. At this time, since the slender stainless steel sound guide tube has good heat dissipation, it can ensure that the temperature at the high-frequency microphone has dropped to 50-60°C.

[0016] (4) Analyze the acoustic signal obtained by the high-frequency microphone to obtain indicators such as waveform, sound pressure level and spectrum distribution. Use a mathematical model to determine whether the lift valve has internal leakage. The processing steps of the mathematical model include: ① Add a Hanning window to the time domain signal; ② Perform FFT Fourier fast transform; ③ Identify the peak of the acoustic signal above 20kHz and calculate the proportion of acoustic power above 20kHz; ④ When the acoustic signal above 20kHz has an obvious peak and the proportion of high-frequency acoustic power is >5%, it is determined that leakage occurs; otherwise, no leakage occurs.

[0017] The beneficial effects of the present invention are: 1. Using acoustic signals as a method for detecting internal leakage of valves in sootblowing systems has the advantages of high sensitivity and accurate judgment.

[0018] 2. The system and method are applicable to soot blowing media such as steam or compressed air.

[0019] 3. The system structure is simple, the transformation work is small, and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a sootblowing system leakage detection system based on acoustic spectrum analysis according to the present invention; In the figure, 1-sootblowing gun barrel; 2-sootblowing nozzle; 3-sootblower inner tube; 4-acoustic leak detection system; 5-lift valve; 6-sootblowing medium main pipe.

[0021] Figure 2 It is a schematic diagram of the connection structure between the acoustic leak detection system, the inner tube of the sootblower, the lifting valve and the sootblowing medium main pipe, wherein 401 is an upper cover plate, 402 is an acoustic resonance chamber, 403 is a sound pressure collecting pipe; 404 is a sound guide pipe; and 405 is a lower cover plate.

[0022] Figure 3 Schematic diagram of the structure of an acoustic leak detection system, wherein 406 is a high-frequency microphone.

[0023] Figure 4 This is a schematic diagram of the connection structure between the upper cover, acoustic resonance chamber, sound pressure collecting tube, and sound guide tube in the acoustic leak detection system.

[0024] Figure 5 It is a schematic diagram of the structure of the lower cover.

[0025] Figure 6 Schematic diagram of the structure of the upper cover and the acoustic resonance chamber.

[0026] Figure 7 It is a cross-sectional view of the connection structure between the upper cover plate and the acoustic resonance chamber.

[0027] Figure 8It is a schematic diagram of the structure of the sound guide tube end and the high-frequency microphone, where 4061 is the microphone and preamplifier; 4062 is the power supply and signal pin.

[0028] Fig. 9 It is the sound pressure waveform under no leakage and leakage conditions.

[0029] Fig.10 It is the spectrum distribution of acoustic signal in the case of no leakage.

[0030] Fig.11 is the spectrum distribution of the acoustic signal in the case of leakage. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0032] like Figure 1 As shown, the sootblowing system consists of a sootblowing medium main pipe 6, a lifting valve 5, a sootblower inner pipe 3 and a sootblowing gun tube 1, wherein the sootblowing gun tube 1 is provided with a sootblowing nozzle 2 for generating a high-speed jet. An acoustic leakage detection system 4 is installed on the sootblower inner pipe 3, i.e., the outside of the pipeline between the outlet of the lifting valve 5 and the sootblowing gun tube 1, through which acoustic signals are collected and mathematically analyzed to detect internal leakage of the lifting valve 5. The inlet of the lifting valve 5 is installed on the sootblowing medium main pipe 6.

[0033] like Figure 2 As shown, the acoustic leakage detection system 4 is composed of an upper cover plate 401, an acoustic resonance cavity 402, a sound pressure collecting pipe 403, a sound guide pipe 404, a lower cover plate 405 and a high-frequency microphone 406. A plurality of acoustic resonance cavities 402 are arranged in a row on the upper cover plate 401, and all the acoustic resonance cavities 402 are connected to the sound pressure collecting pipe 403 through pipes, respectively. The sound pressure collecting pipe 403 is connected to the sound guide pipe 404, and the high-frequency microphone 406 is arranged at one end of the sound guide pipe 404 away from the sound pressure collecting pipe 403.

[0034] Comparison Figure 1-Figure 5 The upper cover plate 401 and the lower cover plate 405 are both semicircular tube-shaped, and the two cooperate with each other to be tightly sleeved on the side outer wall of the sootblower inner tube 3. The upper cover plate 401 and the lower cover plate 405 can be connected to the sootblower inner tube 3 by welding or clamping. The upper cover plate 401 and the lower cover plate 405 are spliced ​​to form a sleeve structure, which is tightly sleeved on the outer side of the side wall of the sootblower inner tube 3.

[0035] like Figure 3 , Figure 8As shown, the sound guide tube 404 is made of stainless steel, with a diameter of no more than 20 mm and a length of no less than 1000 mm, and the surface does not need to be insulated to prevent the high temperature generated when the soot blowing medium is high-temperature steam from adversely affecting the high-frequency microphone 406. The frequency response range of the high-frequency microphone 406 is 200-50000 Hz.

[0036] like Figure 4-7 As shown, there are generally 3 to 6 acoustic resonance cavities 402, and the volumes of the cavities are different from each other, so they have different resonant frequencies, and the resonant frequency range is 20 to 50 kHz. Figure 6-Figure 7 In the figure, the volume of the acoustic resonance cavity 402 gradually decreases from left to right. The bottom of the acoustic resonance cavity 402 is connected to the upper cover plate 401.

[0037] Comparison Figure 8 The high frequency microphone 406 mainly includes two parts, the front end is the microphone and the preamplifier 4061, and the back end is the power supply and signal pin 4062.

[0038] Sootblowing system leak detection system based on acoustic spectrum analysis, which is applicable whether the sootblowing medium is steam or compressed air.

[0039] Specifically, a sootblowing system leakage detection system and method based on acoustic spectrum analysis, taking a 660 MW boiler low-temperature superheater sootblowing leakage detection as an example, comprises the following steps: (1) An acoustic leak detection system 4 is installed on the inner tube 3 of the sootblower between the outlet of the poppet valve 5 and the sootblowing gun tube 1. If the poppet valve 5 leaks internally, the generated airflow will generate a significant high-frequency acoustic signal at this location, which can be detected.

[0040] (2) The length of the sootblower inner tube 3 suitable for installing the acoustic leak detection system 4 is about 310 mm and the outer diameter is 65 mm. Therefore, the inner diameter of the upper cover of the leakage detection equipment is 65 mm, and there are 5 acoustic resonance cavities with different cavity volumes on the upper cover. Their cavity shapes are all cylindrical, with diameters of 35, 30, 25, 15, and 10 mm respectively, and the cavity height is 47.6 mm. The resonant frequency range is 20-50 kHz, which is used to amplify the high-frequency part of the audio. Without these resonance cavities, the acoustic signal transmitted to the high-frequency microphone 406 will become weak, and the acoustic signal above 20 kHz will be severely attenuated.

[0041] (3) The audio signals of several acoustic resonance chambers are collected through the Φ6mm sound pressure collecting tube 403, and then connected to the high-frequency microphone 406 through the Φ6mm sound guide tube 404. When the sootblowing medium is high-temperature steam, the temperature of the sootblower inner tube can reach 195°C. At this time, since the stainless steel slender sound guide tube 404 has good heat dissipation, it can ensure that the temperature of 406 at the high-frequency microphone has been reduced to a safe temperature, which can be reduced to about 45°C in actual measurement.

[0042] (4) Analyze the acoustic signal obtained by the high-frequency microphone 406 to obtain indicators such as waveform, sound pressure level and spectrum distribution.

[0043] Fig. 9 This is a comparison of the sound pressure waveforms in the absence of leakage and leakage, where the sootblowing medium is steam (pressure 1.02MPa, temperature 195℃, flow rate 4 t / h per unit), and the leakage refers to manually opening the lift valve 5 (opening degree is about 10%) to simulate the leakage. As can be seen from the figure, the sound pressure is low when there is no leakage, and the sound pressure increases significantly after the leakage occurs, and the waveform burrs become more. According to calculations, the sound pressure levels before and after the leakage are 87.9 dB and 98.1 dB respectively (both are linearly weighted).

[0044] Fig.10 and Fig.11 are the spectrum distribution of acoustic signals in the case of no leakage and leakage, respectively. Fig. 9 Frequency domain data obtained after Fourier transform. As can be seen from the figure, when there is no leakage, the sound waves are mainly distributed in the low frequency of 10 kHz; after the leakage occurs, the high-speed jet in the pipe generated by the leakage produces an obvious high-frequency acoustic signal with a frequency of 30-40 kHz. According to calculations, the proportion of sound power above 20 kHz before and after the leakage is 1.07% and 8.25% respectively, which is a significant increase.

[0045] Therefore, for this case, the following conditions can be used as leakage detection indicators, and they must meet the following conditions at the same time: (1) the sound pressure level increases by more than 5 dB; (2) the proportion of sound power above 20 kHz increases by more than 5%. For other different power plants and sootblower systems, similar detection and judgment indicators can be obtained through experiments, and the principles are the same.

Claims

1. A sootblowing system leakage detection system based on acoustic spectrum analysis, characterized in that: Includes sootblowing system and acoustic leak detection system; The sootblowing system comprises a sootblowing medium main pipe (6), a lifting valve (5), a sootblower inner pipe (3) and a sootblowing gun pipe (1), wherein the inlet of the lifting valve (5) is mounted on the sootblowing medium main pipe (6), the outlet of the lifting valve (5) is connected to the sootblowing gun pipe (1) via the sootblower inner pipe (3), and the sootblowing gun pipe (1) is provided with a sootblowing nozzle (2) for generating a high-speed jet; The acoustic leakage detection system is installed on the inner tube (3) of the sootblower, that is, on the outer side of the pipeline between the outlet of the lifting valve (5) and the sootblowing gun tube (1). The acoustic leakage detection system collects acoustic signals passing through the inner tube (3) of the sootblower and performs mathematical analysis to detect internal leakage of the lifting valve.

2. A sootblowing system leakage detection system based on acoustic spectrum analysis according to claim 1, characterized in that: The acoustic leakage detection system comprises an upper cover plate (401), an acoustic resonance cavity (402), a sound pressure collecting tube (403), a sound guide tube (404), a lower cover plate (405) and a high-frequency microphone (406); a row of multiple acoustic resonance cavities (402) are provided on the upper cover plate (401); all acoustic resonance cavities (402) are connected to the sound pressure collecting tube (403) via pipes; the sound pressure collecting tube (403) is connected to the sound guide tube (404); and the high-frequency microphone (406) is provided at one end of the sound guide tube (404) away from the sound pressure collecting tube (403); The upper cover plate (401) and the lower cover plate (405) are spliced ​​and fixed together and sleeved on the outside of the side of the sootblower inner tube (3), and are in close contact and connection with the sootblower inner tube (3).

3. A sootblowing system leakage detection system based on acoustic spectrum analysis according to claim 2, characterized in that: The upper cover plate (401) and the lower cover plate (405) are both semicircular tube-shaped, and are tightly fitted together on the side outer wall of the sootblower inner tube (3); the upper cover plate (401) and the lower cover plate (405) are connected to the sootblower inner tube (3) by welding or clamping.

4. A sootblowing system leakage detection system based on acoustic spectrum analysis as claimed in claim 2, characterized in that: The number of the acoustic resonance cavities (402) is 3-6, and their cavity volumes are different, so they have different resonance frequencies, and the resonance frequency range is 20-50 kHz.

5. A sootblowing system leakage detection system based on acoustic spectrum analysis as claimed in claim 2, characterized in that: The sound guide tube (404) is made of stainless steel, has a diameter not greater than 20 mm, a length not less than 1000 mm, and has no surface insulation.

6. A sootblowing system leakage detection system based on acoustic spectrum analysis according to claim 2, characterized in that: The frequency response range of high frequency microphones is 200-50000 Hz.

7. A sootblowing system leakage detection method based on acoustic spectrum analysis, characterized in that: The sootblowing system leakage detection system based on acoustic spectrum analysis described in any one of claims 1 to 6 is used, and its principle and detection method are as follows: S1: The acoustic leak detection system is installed on the inner tube of the sootblower between the outlet of the lifting valve and the sootblowing gun tube. If the lifting valve leaks internally, the generated airflow will generate significant high-frequency acoustic signals at the position of the inner tube of the sootblower, which can be detected; S2: The acoustic leak detection system is equipped with 3-6 acoustic resonance chambers of different volumes, with a resonant frequency range of 20-50 kHz, which is used to amplify the mid- and high-frequency parts of the audio; S3: The audio signals of several acoustic resonance chambers are aggregated through a sound pressure collecting tube, and then transmitted to a high-frequency microphone through a sound guide tube. The sound signals obtained by the high-frequency microphone are analyzed to obtain a series of indicators such as waveform, sound pressure level and spectrum distribution. Through a mathematical model, it is determined whether the lifting valve of the sootblowing system has internal leakage.

8. A sootblowing system leakage detection method based on acoustic spectrum analysis according to claim 7, characterized in that: The soot blowing medium of the soot blowing system is steam or compressed air.

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