CN119985689A - A method and system for monitoring the number and radius of bubbles in a sieve plate tower - Google Patents
A method and system for monitoring the number and radius of bubbles in a sieve plate tower Download PDFInfo
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Abstract
The invention relates to a method and a system for monitoring the number and the radius of bubbles in a sieve plate tower, wherein the method comprises the steps of dividing an audible sound range [20-20,000] Hz into two frequency bands of a bubble generation sounding zone and a bubble crushing sounding zone according to the frequency, installing sound sensors at the middle positions of the tower and/or the liquid layer height of the sieve plate tower, collecting sound signals of internal fluid in the driving process of the tower, preprocessing the collected sound signals, utilizing a fast Fourier transform algorithm to obtain the main frequency of each sound wave pulse in the sound signals, determining whether the sound signals belong to the bubble generation sounding zone or the bubble crushing sounding zone according to the frequency of the main frequency, substituting the sound signals into a corresponding correlation formula to determine the bubble radius of the sound signals, and counting the number of respective pulse peaks in the bubble generation sounding zone and the bubble crushing sounding zone in sample time to obtain the generation number of bubbles and the crushing number of the bubbles respectively. The real-time monitoring of the number and the size of the internal bubbles in the starting state of the sieve plate tower is realized.
Description
Technical Field
The invention relates to the technical field of monitoring of chemical production processes, in particular to a method and a system for monitoring the number and the radius of bubbles in a sieve plate tower.
Background
In the chemical production process, the sieve plate tower is used as a common gas-liquid mass transfer device and is widely applied to the fields of petrochemical industry, pharmacy, food and the like, and the stable and efficient operation of the sieve plate tower is important for the quality and the production safety of products. Therefore, a quick, accurate and efficient online monitoring method and system are developed, are used for monitoring the flowing state and the mixing degree of fluid in a tower in real time, and are important for accurately regulating and controlling production parameters, guaranteeing product quality and reducing the possibility of accidents.
With the development of modern industry, higher requirements are put on the monitoring technology of the rectifying tower. Traditional monitoring methods, such as measurement of parameters of temperature, pressure, flow and the like, can reflect the running state of equipment to a certain extent, but often have certain limitations. Monitoring techniques such as temperature, pressure, flow, etc. have the problem of low sensitivity and may not be able to detect accurately in time for some early, potential faults. The current radiation monitoring technology is often limited in operation condition, and the equipment cost and professional requirements for operators are high, so that the technology is not optimal for real-time monitoring of the operation process of the tower. The acoustic monitoring technology is used as a non-invasive monitoring means with long propagation distance and strong real-time performance, and provides a new thought and method for real-time monitoring of the rectification process.
The fluid flow process in the rectifying tower involves complex gas-liquid two-phase interactions, wherein the number and the size of bubbles are key parameters for measuring the gas-liquid contact state. For example, in petrochemical industry, when crude oil is fractionated, accurate knowledge of these parameters of bubbles in the column can better control the fractionation process and improve the separation accuracy of different fractions. For example, the size and number of bubbles can affect the gas-liquid contact area and mass transfer efficiency. If the size of the bubbles is large, the relative contact area is small, which may cause low mass transfer efficiency, and the number of the bubbles is too large, which may cause flooding or entrainment, affect the separation effect, and even cause unstable operation of the device. For the production of fine chemical products, such as pharmaceuticals, fragrances and other industries, the purity requirement of the products is extremely high, and the gas-liquid mass transfer efficiency can be improved and the energy consumption can be reduced by reasonably adjusting the number, the size and the density of bubbles. For example, in a large chemical device, optimizing bubble parameters (optimizing bubble parameters refers to regulating and controlling the generation speed, size and the like of bubbles) can enable a rectifying tower to achieve the same separation effect under a lower reflux ratio, so that the consumption of heating steam is reduced, and energy conservation and emission reduction are realized.
In addition, from the aspects of process optimization, energy conservation and emission reduction, the dynamic processes such as bubble generation and rupture in the sieve plate tower are the main sources of sound production in the tower. When bubbles are generated, gas enters the liquid phase from the mesh openings, and the process causes volume pulsation of the bubbles and disturbance of surrounding liquid, thereby generating sound with a specific frequency. The rapid change of the gas-liquid interface releases strong energy at the moment of bubble rupture, and produces more obvious sound. The sound signals generated by these bubble behaviors are rich in information about the mixing state of the fluid in the tower and the operating conditions of the equipment.
Under the trend of the chemical production towards the intelligent and fine development, the bubble parameter information captured by utilizing the passive acoustic monitoring technology during the running process of equipment can provide a key feedback data source for an automatic control system, and how to effectively utilize the passive acoustic monitoring data to obtain the number and the radius of bubbles in a sieve plate tower, so that the intelligent operation and the optimal control of the rectification process are realized, and the development of the chemical production towards the direction of higher quality and higher benefit is promoted.
Disclosure of Invention
The invention aims to provide a method and a system for monitoring the number and the radius of bubbles in a sieve plate tower, and the method and the system realize real-time monitoring of the number and the size of the bubbles in the sieve plate tower in a starting state.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
In a first aspect, the present invention provides a method for monitoring the number and radius of bubbles in a sieve plate tower, the method comprising the following steps:
1) Defining two frequency bands of a bubble generation sounding zone and a bubble breaking sounding zone according to the frequency in an audible sound range [20-20,000] Hz, wherein [20-3,000] Hz is the bubble generation sounding zone and [ 3,000-20,000] Hz is the bubble breaking sounding zone;
2) Preprocessing the collected sound signals to remove low-frequency noise and high-frequency interference components in the signals;
3) The method comprises the steps of carrying out frequency spectrum analysis on a preprocessed signal through a fast Fourier transform algorithm, obtaining a main frequency of each sound wave pulsation in an acoustic signal, determining whether the main frequency belongs to a bubble generation sounding zone or a bubble breaking sounding zone according to the frequency range of the main frequency, wherein the main frequency is acoustic frequency f d when the main frequency is generated in the bubble generation sounding zone, and the acoustic frequency f b when the main frequency is broken at a free interface in the bubble generation sounding zone;
For the bubble generation sounding zone, calculating a bubble generation radius according to formula (1);
calculating a bubble breaking radius for the bubble breaking sounding zone according to formula (2):
Wherein R d is the bubble generation radius (mm) when the bubble breaks away from the orifice, R b is the bubble breaking radius (mm) when the bubble breaks at the free interface, ρ is the surrounding medium density (kg/m 3);P0 is the pressure (Pa) acting on the bubble, γ is the ratio of the isobaric specific heat of the gas to the isocratic heat, f d is the acoustic frequency (Hz) when the bubble is generated, and f b is the acoustic frequency (Hz) when the bubble breaks at the free interface;
4) Based on the preprocessed signals, counting the number of respective pulsation peaks in the bubble generation sounding zone and the bubble breaking sounding zone in the sample time, respectively obtaining the generation number of bubbles and the breaking number of the bubbles, and further calculating the bubble generation frequency and the bubble breaking frequency, namely the number of bubbles generated or broken per second.
Further, γ=1.41, and p 0 is the monitored column internal pressure.
In a second aspect, the present invention provides a method for monitoring the number and radius of bubbles in a sieve plate tower, the method comprising the following steps:
Constructing a simulation test bed, wherein the simulation test bed comprises a tower main body with a transparent visual cup, a high-speed camera for observing the size of bubbles in the tower and a pressure sensor for monitoring the pressure in the tower main body;
Acquiring bubble radiuses and corresponding main frequencies under different liquid media through a simulation test bed, and recording the ratio gamma of the constant pressure of the pressure, the constant pressure and the constant specific heat of the gas which are currently acted on the bubbles and the surrounding medium density rho;
carrying out correlation and regression analysis on the bubble generation data set and the bubble crushing data set to respectively obtain correlation formulas of acoustic frequencies and bubble radiuses under different behaviors of the bubbles;
after the corresponding main frequency is obtained through the sound signal, which frequency band the main frequency belongs to is confirmed, the main frequency is substituted into the corresponding association formula to determine the bubble radius, and the pulse number of different frequency bands is counted to obtain the bubble number of the frequency band.
In a third aspect, the present invention provides a system for monitoring the number and radius of bubbles in a sieve tray column, the system comprising:
The sound monitoring device is used for collecting and transmitting sound signals in the sieve plate tower and mainly comprises a sound sensor, a signal amplifier and a data acquisition card, wherein the sound sensor is used for collecting the sound signals in the sieve plate tower, the signal amplifier is used for improving the signal-to-noise ratio of the sound signals, and the data acquisition card is used for temporarily storing the sound signals;
a pressure sensor for monitoring the pressure in the tower;
The pretreatment module is used for carrying out pretreatment on the collected sound signals;
The feature extraction module is used for extracting acoustic frequency features of the preprocessed sound signals to obtain a main frequency;
the model building module is used for obtaining a correlation formula of the acoustic frequency and the bubble radius under different behaviors of the bubble;
The model calculation module is used for determining the frequency band according to the main frequency, further calculating the bubble radius according to the association formulas of different frequency bands, and simultaneously counting the number of bubbles in the frequency band;
and the display module is used for displaying the number of bubbles and the bubble radius of different frequency bands.
Further, at least one sound sensor is correspondingly arranged on each measuring point of the tower, and the number and the layout of the sound sensors are optimized and adjusted according to the size and the monitoring requirement of the tower;
The bubble radius is divided into a bubble generation radius and a bubble crushing radius, and the bubble generation frequency and the bubble crushing frequency are respectively obtained according to the number of bubbles in different frequency bands in the statistical sample time;
The display module can display waveform diagrams, spectrograms, bubble generation frequencies, acoustic frequencies during bubble generation, bubble generation radius, bubble crushing frequency, acoustic frequencies during crushing at a free interface and crushing radius of bubble sound signals of different measuring points in the tower.
Further, the system is provided with a product discharge stability monitoring component, and whether product discharge is stable or not is monitored in real time at the initial operation stage of tower equipment;
recording the radius ranges of bubbles calculated by each measuring point of the tower equipment in the stable discharging period of the product, counting the distribution of the bubble radius according to the tower height direction, dividing different radius sections according to the distribution of the bubble radius, and recording the radius ranges of the bubbles in each radius section to be used as a standard range;
If the number of bubbles exceeds the threshold value of the number of bubbles, the gas phase speed is too high, so that abnormal behaviors such as flooding or entrainment and the like of the equipment are easily caused, the heating amount of the reboiler of the equipment is reduced, or the feed flow is increased, or the reflux ratio is increased to maintain proper gas-liquid ratio;
when the size of the generated bubbles is detected to be smaller than the standard range of the corresponding position, and the size of the generated bubbles is detected to be larger than the standard range of the corresponding position, the bubbles are represented to have more coalescence behavior, and the collision kinetic energy of the bubbles is reduced by adding the defoaming agent or reducing the steam amount until the product discharge is kept stable.
Compared with the prior art, the invention has the beneficial effects that:
The invention monitors the bubble generation behavior and the breaking behavior in the rectification process by using a passive acoustic monitoring technology in the audible sound range for the first time, namely, the application is monitoring through the sounding of the bubble per se behavior in the audible sound range of human ears. Passive acoustics, meaning that the bubbles themselves produce sound that is collected and analyzed by a receiving device.
The invention uses the acoustic monitoring technology for fault diagnosis of the rectifying tower, can perform nondestructive monitoring on bubbles in the continuous operation process of industrial equipment such as the rectifying tower or a reactor, monitors the generation number and the size of the bubbles in the equipment, and can timely regulate and control the operation parameters of the equipment if the generation number and the size of the bubbles exceed normal values so as to ensure efficient production.
The internal fluid has complex turbulence process during the running process of the equipment, the main acoustic signals are generated by bubbles, but the characteristics of the acoustic signals are numerous, mainly including the characteristics of duration, amplitude, power spectrum density, frequency and the like, the application creatively selects the main frequency as the reference of the acoustic frequency and the divided frequency band, and can effectively capture the generated sound frequency and the broken sound frequency in the bubble group. According to the application, through experimental data analysis, the close mathematical correlation exists between the acoustic frequency and the size of the bubble, the frequency characteristics of the two processes of generation and crushing have obvious difference, and the correlation is established between the acoustic frequency and the size of the bubble according to different frequency bands, so that even if the two processes of bubble generation and bubble crushing occur simultaneously, the two processes can be accurately distinguished.
Drawings
FIG. 1 is a schematic diagram of a system for monitoring the number and radius of bubbles in a sieve plate tower according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for monitoring the number and radius of bubbles in a sieve plate tower according to an embodiment of the present invention;
fig. 3 is a display of an operation panel of a monitoring system for the number and radius of bubbles in a sieve plate tower according to an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
The frequency refers to the number of events occurring per second in the present invention. Bubble collapse frequency refers to the number of bubbles that collapse per second. Breaking acoustic frequency (acoustic frequency at break-up at free interface) means that the break-up of a bubble produces an acoustic signal that fluctuates due to the vibration of the surface of the bubble, the number of vibrations per second being the acoustic frequency.
The invention mainly identifies and monitors the size and number of internal bubbles in the operation process of the tower equipment, and is used in subsequent reaction regulation and control according to the monitoring result, for example, when the size of the bubbles is detected to be too large, the gas phase speed is possibly too low, so that the bubbles are not easy to break, the heating amount of a reboiler of the equipment can be adjusted, the steam amount is increased, the gas speed is accelerated, and the breaking is promoted. If the number of bubbles is too large, the gas phase speed is too high, so that abnormal behaviors such as flooding or entrainment and the like of equipment are easily caused, and the heating amount of a reboiler of the equipment is required to be reduced, the feeding flow rate is increased, or the reflux ratio is increased to maintain the proper gas-liquid ratio. In addition, if the size at the time of bubble generation is detected to be smaller and the size at the time of crushing to be larger, it represents that there is more coalescence behavior of bubbles, and the collision kinetic energy of bubbles can be reduced by adding an appropriate amount of defoaming agent or appropriately reducing the amount of steam. By adjusting the operation parameters of the equipment and controlling the bubble state (temperature control, feeding speed control or other control means to control the size of boiling bubbles in the tower), the entrainment of impurities can be reduced, and the product quality can be improved.
Fig. 1 is a schematic structural diagram of a tower monitoring system according to an embodiment of the present invention, where the tower monitoring system 10 is configured to monitor an operation state of a tower in real time on line, and discover a number of bubbles generated, a number of broken bubbles, and an average size in the tower in time, so as to ensure product quality and improve efficiency of operation of the tower. Referring to fig. 1, a tower body 01 of the tower has multiple layers of sections to be tested 02 which are arranged in parallel, and at least one measuring point (not shown) is arranged on the outer wall of the tower body 01 corresponding to each section to be tested 02. One monitoring sensor 110 is correspondingly arranged at one measuring point, and the tower monitoring system 10 comprises a plurality of monitoring sensors 110, wherein the plurality of monitoring sensors 110 comprise a plurality of sound sensors. The monitoring system further comprises a control device 120, wherein the control device 120 is respectively and electrically connected with the plurality of monitoring sensors 110 or wirelessly connected with the plurality of monitoring sensors 110, and is used for acquiring sound signals related to the internal operation state of the tower through the monitoring sensors 110, and determining the generation number, the crushing number and the average size of bubbles in the sieve plate tower according to the sound signals so as to identify the bubble distribution condition in the tower.
It should be noted that, regarding the layout manner of the measuring points, fig. 1 only shows the layout manner of a single measuring point disposed on the outer wall of the tower body 01 corresponding to each section 02 to be tested, in other embodiments, each section 02 to be tested may be disposed with a single measuring point or multiple measuring points, and the monitoring of the operation state of the tower is achieved by placing the monitoring sensor 110 on the measuring point. Illustratively, in the present embodiment, the monitoring sensor 110 employs a sound sensor. The sound sensor has the advantages of low cost, small volume, convenience in installation and the like, has strong practicability, and can collect weak sound signals.
Example 1
The invention relates to a method for monitoring the number and the radius of bubbles in a sieve plate tower, which comprises the following steps:
1) Defining two frequency bands of a bubble generation sounding zone and a bubble breaking sounding zone according to the frequency in an audible sound range [20-20,000] Hz, wherein [20-3,000] Hz is the bubble generation sounding zone and [ 3,000-20,000] Hz is the bubble breaking sounding zone;
2) Preprocessing the collected sound signals to remove low-frequency noise and high-frequency interference components in the signals;
3) The method comprises the steps of carrying out frequency spectrum analysis on a preprocessed signal through a fast Fourier transform algorithm, obtaining a main frequency of each sound wave pulsation in an acoustic signal, determining whether the main frequency belongs to a bubble generation sounding zone or a bubble breaking sounding zone according to the frequency range of the main frequency, wherein the main frequency is acoustic frequency f d when the main frequency is generated in the bubble generation sounding zone, and the acoustic frequency f b when the main frequency is broken at a free interface in the bubble breaking sounding zone;
For the bubble generation sounding zone, calculating a bubble generation radius according to formula (1);
calculating a bubble breaking radius for the bubble breaking sounding zone according to formula (2):
Wherein R d is the bubble generation radius (mm) when the bubble breaks away from the orifice, R b is the bubble breaking radius (mm) when the bubble breaks at the free interface, ρ is the surrounding medium density (kg/m 3);P0 is the pressure (Pa) acting on the bubble, γ is the ratio of the isobaric specific heat of the gas to the isocratic heat, f d is the acoustic frequency (Hz) when the bubble is generated, and f b is the acoustic frequency (Hz) when the bubble breaks at the free interface;
4) Based on the preprocessed signals, counting the number of respective pulsation peaks in the bubble generation sounding zone and the bubble breaking sounding zone in the sample time, respectively obtaining the generation number of bubbles and the breaking number of the bubbles, and further calculating the bubble generation frequency and the bubble breaking frequency, namely the number of bubbles generated or broken per second.
The installation position of the sound sensor in the invention is required to be 1, and the installation position is usually arranged at the middle position between two layers of tower plates and at the height of the liquid layer. 2. The distribution number can be distributed at equal intervals according to the tower height, the number of layers of tower plates and the requirement, each layer is not required to be installed, and the number is not limited. The sieve plate tower body is provided with a plurality of layers of sections to be tested which are arranged in parallel, at least one measuring point is arranged on the outer wall of the tower body corresponding to each section to be tested, at least one sound sensor is correspondingly arranged on each measuring point of the sieve plate tower, and the number and the layout of the sound sensors are optimized and adjusted according to the size and the monitoring requirement of the sieve plate tower.
The invention carries out preprocessing on the collected sound signals, including pre-emphasis, filtering and noise reduction. The filtering is band-pass filtering, which is used for removing low-frequency noise and high-frequency interference components in signals, in the embodiment, the band-pass filter only allows signals in a specific frequency range (100-18000 Hz) to pass, the passing range is set to be 100-18000Hz, other signals below 100Hz or above 18000Hz captured in the signals are directly filtered, and then, the wiener filtering technology is adopted to remove in-band noise interference, such as interference signals of environmental noise and the like, so that the signal-to-noise ratio of the signals is further improved.
The reliability of the method is proved by a large number of experiments, the number and the size of bubbles in the tower are monitored based on the sound signal analysis technology, and the technology provides an important reference for the on-line monitoring of the sound signal for other types of bubbling equipment.
Example 2
The monitoring system of bubble number and radius in this embodiment sieve plate tower, the system includes:
The sound monitoring device is used for collecting and transmitting sound signals in the sieve plate tower and mainly comprises a sound sensor, a signal amplifier and a data acquisition card, wherein the sound sensor is used for collecting the sound signals in the sieve plate tower, the signal amplifier is used for improving the signal-to-noise ratio of the sound signals, and the data acquisition card is used for temporarily storing the sound signals;
a pressure sensor for monitoring the pressure in the tower;
The pretreatment module is used for carrying out pretreatment on the collected sound signals;
The feature extraction module is used for extracting acoustic frequency features of the preprocessed sound signals to obtain a main frequency;
the model building module is used for obtaining a correlation formula of the acoustic frequency and the bubble radius under different behaviors of the bubble;
The model calculation module is used for determining the frequency band according to the main frequency, further calculating the bubble radius according to the association formulas of different frequency bands, and simultaneously counting the number of bubbles in the frequency band;
and the display module is used for displaying the number and the radius of the bubbles in the sieve plate tower based on the acoustic frequency.
In the invention, one measuring point is correspondingly provided with a sound sensor, and a plurality of monitoring measuring points comprise a plurality of sound sensors which are used for collecting sound signals in the sieve plate tower;
the preprocessing module, the characteristic extraction module, the model construction module, the model calculation module and the display module form a control device, and the control device is respectively electrically or wirelessly connected with the sound sensor and is used for acquiring sound signals related to the size distribution of bubbles in the sieve plate tower.
The display module can display waveform diagrams, spectrograms, bubble generation frequencies, acoustic frequencies during bubble generation, bubble generation radius, bubble crushing frequencies, acoustic frequencies during crushing at a free interface, crushing radius and the like of bubble sound signals of different measuring points in the tower, and relevant information is visually displayed, so that operators can know the state of bubbles in the sieve plate tower in real time.
Example 3
The monitoring method of the embodiment comprises the following steps:
The method comprises the following steps of T1, connecting a sound sensor at a preset position of the outer wall of the tower, and collecting sound signals of internal fluid in the driving process of the tower;
And T2, preprocessing the collected sound signals, including pre-emphasis, filtering and noise reduction.
T3, converting the preprocessed sound signal from a time domain to a frequency domain through a fast Fourier transform algorithm, extracting frequency characteristics of the sound signal, and obtaining main frequencies of all sound wave pulsation in the sound fragment;
T4, defining a frequency interval corresponding to two actions of bubble generation and breaking; according to a large number of experimental researches, the sound production frequency ranges of the bubble generation and crushing processes are different, namely 20-3,000 Hz is defined as a bubble generation sound production area, and 3,000-20,000 Hz is defined as a bubble crushing sound production area; the main frequency of the acoustic frequency f b when the acoustic frequency f is located in the bubble breaking sounding zone and broken at the free interface;
And T5, based on the preprocessed signals, counting the number of pulsation peaks in the bubble generation sounding zone and the bubble breaking sounding zone in the sample time, and respectively calculating the bubble generation frequency and the bubble breaking frequency.
And T6, calculating the radius of the bubbles according to the association formulas of different frequency bands, and simultaneously counting the number of the bubbles in the frequency bands.
The tower is of a sieve plate tower type, the tower body is provided with a plurality of layers of sections to be tested which are arranged in parallel, at least one acoustic signal measuring point is arranged on the outer wall of the tower body corresponding to each section to be tested, and acoustic signals are monitored at each measuring point.
The sound sample collection interval and the sampling time length can be adjusted according to the monitoring requirement.
The number of pulsations in different frequency bands of the sound clip is counted to represent the number of bubbles in which this behaviour occurs.
The formula for the correlation of acoustic frequency with bubble radius is as follows:
bubble generation sounding area:
bubble breaking sounding area:
Where R d is a bubble generation radius (mm) when a bubble is detached from an orifice, R b is a bubble breaking radius (mm) broken at a bubble free interface, ρ is a surrounding medium density (kg/m 3),P0 is a pressure (Pa) acting on the bubble, γ is a ratio of isobaric specific heat of a gas to isocratic specific heat, γ=1.41 for air in a standard state, f d is an acoustic frequency (Hz) at the time of bubble generation, and f b is an acoustic frequency (Hz) at the free interface (obtained by performing the above FFT conversion by Matlab software after acoustic signal pretreatment), different densities, pressures, and specific heat ratios of substances are different, and when a substance type is determined, the density and the specific heat ratio can be regarded as constant.
According to the embodiment of the invention, the multi-layer cross sections to be tested are arranged on the tower body, at least one measuring point is distributed on the outer wall of the tower body corresponding to each cross section to be tested, so that the tower monitoring system collects sound signals related to the state of bubbles in the tower through the sound sensors arranged on the measuring points and transmits the sound signals to the control device, the control device analyzes the characteristics of the sounding time domain and the sounding frequency domain of the bubbles according to the obtained sound signals, counts the generation number and the crushing number of the bubbles in unit time (1 s), calculates the radius of the bubbles according to the acoustic frequency of the bubbles, and identifies the state of the bubbles in the tower. According to the embodiment of the invention, through acquisition, real-time monitoring and dynamic analysis of the sound signals generated in the operation process of the chemical tower, the on-line detection of the mixing state of the materials in the operation process of the chemical tower is realized, and powerful guarantee is provided for the efficient and safe operation of the chemical tower. The system mainly comprises the sound sensor, so that the cost is effectively reduced, the problem of high cost of the existing monitoring equipment for the operation state of the chemical tower is solved, the internal operation state of the tower is identified according to the sound signals of a plurality of sections to be tested, the monitoring precision is improved, and the problem of low accuracy of the existing monitoring equipment is solved.
Example 4
The embodiment of the invention discloses a method for monitoring the number of bubbles and the radius of bubbles in a rectifying tower based on acoustic frequency characteristics. The method comprises the steps of obtaining sound signals of internal fluid in a driving state of the tower through a microphone array, extracting frequency characteristics of the sound signals, defining sounding frequency intervals corresponding to bubble generation and crushing behaviors, counting the number of pulses in different frequency bands to represent the number of bubbles in the frequency bands, and calculating the generation radius and the crushing radius of bubbles in the tower according to correlation formulas of sounding frequencies and bubble radiuses in different behaviors of the bubbles.
The invention adopts passive acoustic nondestructive monitoring technology, does not need to carry out invasive operation on the tower, can realize monitoring on the quantity and the size of internal bubbles in the running process of the black box model tower, further obtains the mixing state and the reaction proceeding degree of internal fluid, and realizes the online detection and the accurate regulation of the running state of the chemical tower.
For example, in the tower monitoring system 10 shown in fig. 1, in practical application, for small-scale or pilot-scale experimental towers, a wired signal transmission manner may be used to implement data transmission between the sound sensor 110 and the control device 120, that is, the control device 120 is configured for each tower separately. For industrial equipment-level towers, a central control room can be configured for a plurality of towers, and data transmission is realized by adopting a wireless short-distance communication mode between each measuring point of the towers and an upper computer (the control device 120).
For example, a sensor with a wireless communication function can be installed at each measuring point, and data transmission can be performed in a wireless short-distance communication mode such as Bluetooth, wiFi and the like.
Fig. 2 is a schematic flow chart of a monitoring method adopted by the tower monitoring system according to the embodiment of the present invention. The method comprises the following steps:
S21, acquiring a sound signal which is transmitted by a sound sensor and is related to the state of air bubbles in the tower;
s22, preprocessing the sound signal through filtering enhancement and wavelet noise reduction to obtain a pure sound signal;
The single-channel sound signal transmitted by each sound sensor is first preprocessed. Because the sound of the internal operation state of the tower, which is monitored by the sound sensor on the tower wall, is a weak signal and can be submerged in the environmental noise, pretreatment such as windowing, framing, noise elimination, enhancement and the like are needed. Illustratively, the frame length is selected to be 10ms, the delay between frames is 5ms, and the observation signal x (n) is set:
x(n)=s(n)+d(n) (3)
Wherein s (n) is a clean sound signal, d (n) is ambient noise, and the observed signal is a 44.1kHz sample, 16bit code. The length of the sound signal per frame is l=512 and the number of frames is set to M depending on the total duration of the test signal. Removing environmental noise by Wiener filtering technology, and obtaining an optimal solution under the least square error by solving a Wiener-Hopf equation to be used as an estimated signal of a pure sound signal Y (n) is the pre-processed signal.
S23, performing Fast Fourier Transform (FFT) on the preprocessed signal y (n) according to a formula (4), transforming the signal from a time domain to a frequency domain, analyzing characteristic information of the time domain and the frequency domain of the sound signal, such as information of frequency, resolution, amplitude, phase and the like of the sound signal, and obtaining the frequency characteristic of the air bubble, namely a main frequency.
The above is the fourier series of the periodic sequence,Expressed as a base frequency sequence, j is an imaginary unit, k is a frequency index (0.ltoreq.k.ltoreq.N-1), this formula expresses the sequenceConversion from time domain to frequency domain, whereinRepresenting a kth frequency component in the frequency domain; for the nth sequence in the time domain, N is the number of cycles and ω (N) is a window function.
After the sound signal is transformed by the formula (4), the original pulsation waveform diagram is changed into a frequency peak diagram, the component size of the sound signal on each frequency is shown, and the highest peak is the main frequency.
S24, counting the pulse numbers in different frequency bands in the sound sample, and calculating the bubble generation frequency and the bubble breaking frequency.
S25, calculating the size radius of the bubble generation process and the size radius of the bubble breaking process according to the formula (1) and the formula (2) respectively by using the main frequency obtained in the S23 so as to identify the material mixing state in the tower.
In a practical scenario, the diameter of the tower monitoring method and system provided by the embodiment of the invention is as followsThe internal bubble distribution state of a certain middle-sized experimental tower is monitored, the layout of a monitoring sensor in a monitoring system refers to fig. 1, relevant test data are provided, and the operation state of the corresponding position of one section to be tested in the monitoring tower is taken as an example, so that the acoustic signals of bubbles in different states are proved to be different, and the reliability of the tower monitoring method based on the acoustic signal analysis technology provided by the embodiment is verified.
Fig. 3 is a schematic diagram of a monitoring panel, i.e. a display module, for monitoring the size of bubbles in a sieve plate tower according to an embodiment of the present invention, where an acoustic signal sampling interval and sampling time are autonomously set according to implementation requirements, and an acoustic sample is stored in a wav format. The monitoring panel can acquire a waveform diagram and a spectrogram of the sound signal. The system can respectively count the number of bubbles in each frequency band in the sample time according to a preset frequency range, and calculate the bubble generation frequency and the bubble breaking frequency. In addition, according to the set formulas (1) and (2), the average generation radius and the average crushing radius of the bubbles in the tower, that is, the bubble generation radius and the bubble crushing radius are obtained.
Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.
The invention is applicable to the prior art where it is not described.
Claims (6)
1. A method for monitoring the number and radius of bubbles in a sieve plate tower is characterized by comprising the following steps:
1) Defining two frequency bands of a bubble generation sounding zone and a bubble breaking sounding zone according to the frequency in an audible sound range [20-20,000] Hz, wherein [20-3,000] Hz is the bubble generation sounding zone and [ 3,000-20,000] Hz is the bubble breaking sounding zone;
2) Preprocessing the collected sound signals to remove low-frequency noise and high-frequency interference components in the signals;
3) The method comprises the steps of carrying out frequency spectrum analysis on a preprocessed signal through a fast Fourier transform algorithm, obtaining a main frequency of each sound wave pulsation in an acoustic signal, determining whether the main frequency belongs to a bubble generation sounding zone or a bubble breaking sounding zone according to the frequency range of the main frequency, wherein the main frequency is acoustic frequency f d when the main frequency is generated in the bubble generation sounding zone, and the acoustic frequency f b when the main frequency is broken at a free interface in the bubble generation sounding zone;
For the bubble generation sounding zone, calculating a bubble generation radius according to formula (1);
calculating a bubble breaking radius for the bubble breaking sounding zone according to formula (2):
Wherein R d is the bubble generation radius (mm) when the bubble breaks away from the orifice, R b is the bubble breaking radius (mm) when the bubble breaks at the free interface, ρ is the surrounding medium density (kg/m 3);P0 is the pressure (Pa) acting on the bubble, γ is the ratio of the isobaric specific heat of the gas to the isocratic heat, f d is the acoustic frequency (Hz) when the bubble is generated, and f b is the acoustic frequency (Hz) when the bubble breaks at the free interface;
4) Based on the preprocessed signals, counting the number of respective pulsation peaks in the bubble generation sounding zone and the bubble breaking sounding zone in the sample time, respectively obtaining the generation number of bubbles and the breaking number of the bubbles, and further calculating the bubble generation frequency and the bubble breaking frequency, namely the number of bubbles generated or broken per second.
2. The method of monitoring of claim 1, wherein γ = 1.41 and p 0 is the monitored pressure within the column.
3. A method for monitoring the number and radius of bubbles in a sieve plate tower, comprising the following steps:
Constructing a simulation test bed, wherein the simulation test bed comprises a tower main body with a transparent visual cup, a high-speed camera for observing the size of bubbles in the tower and a pressure sensor for monitoring the pressure in the tower main body;
Acquiring bubble radiuses and corresponding main frequencies under different liquid media through a simulation test bed, and recording the ratio gamma of the constant pressure of the pressure, the constant pressure and the constant specific heat of the gas which are currently acted on the bubbles and the surrounding medium density rho;
carrying out correlation and regression analysis on the bubble generation data set and the bubble crushing data set to respectively obtain correlation formulas of acoustic frequencies and bubble radiuses under different behaviors of the bubbles;
after the corresponding main frequency is obtained through the sound signal, which frequency band the main frequency belongs to is confirmed, the main frequency is substituted into the corresponding association formula to determine the bubble radius, and the pulse number of different frequency bands is counted to obtain the bubble number of the frequency band.
4. A system for monitoring the number and radius of bubbles in a sieve tray tower, said system comprising:
The sound monitoring device is used for collecting and transmitting sound signals in the sieve plate tower and mainly comprises a sound sensor, a signal amplifier and a data acquisition card, wherein the sound sensor is used for collecting the sound signals in the sieve plate tower, the signal amplifier is used for improving the signal-to-noise ratio of the sound signals, and the data acquisition card is used for temporarily storing the sound signals;
a pressure sensor for monitoring the pressure in the tower;
The pretreatment module is used for carrying out pretreatment on the collected sound signals;
The feature extraction module is used for extracting acoustic frequency features of the preprocessed sound signals to obtain a main frequency;
the model building module is used for obtaining a correlation formula of the acoustic frequency and the bubble radius under different behaviors of the bubble;
The model calculation module is used for determining the frequency band according to the main frequency, further calculating the bubble radius according to the association formulas of different frequency bands, and simultaneously counting the number of bubbles in the frequency band;
and the display module is used for displaying the number of bubbles and the bubble radius of different frequency bands.
5. The system of claim 4, wherein at least one sound sensor is correspondingly arranged at each measuring point of the tower, and the number and the layout of the sound sensors are optimally adjusted according to the size and the monitoring requirement of the tower;
The bubble radius is divided into a bubble generation radius and a bubble crushing radius, and the bubble generation frequency and the bubble crushing frequency are respectively obtained according to the number of bubbles in different frequency bands in the statistical sample time;
The display module can display waveform diagrams, spectrograms, bubble generation frequencies, acoustic frequencies during bubble generation, bubble generation radius, bubble crushing frequency, acoustic frequencies during crushing at a free interface and crushing radius of bubble sound signals of different measuring points in the tower.
6. The system according to claim 4, wherein the system is provided with a product discharge stability monitoring assembly for monitoring whether product discharge is stable in real time at an initial stage of operation of the tower apparatus;
recording the radius ranges of bubbles calculated by each measuring point of the tower equipment in the stable discharging period of the product, counting the distribution of the bubble radius according to the tower height direction, dividing different radius sections according to the distribution of the bubble radius, and recording the radius ranges of the bubbles in each radius section to be used as a standard range;
If the number of bubbles exceeds the threshold value of the number of bubbles, the gas phase speed is too high, so that abnormal behaviors such as flooding or entrainment and the like of the equipment are easily caused, the heating amount of the reboiler of the equipment is reduced, or the feed flow is increased, or the reflux ratio is increased to maintain proper gas-liquid ratio;
when the size of the generated bubbles is detected to be smaller than the standard range of the corresponding position, and the size of the generated bubbles is detected to be larger than the standard range of the corresponding position, the bubbles are represented to have more coalescence behavior, and the collision kinetic energy of the bubbles is reduced by adding the defoaming agent or reducing the steam amount until the product discharge is kept stable.
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