Method and system for monitoring number and radius of bubbles in sieve-plate tower

Abstract

The invention relates to a method and system for monitoring the number and radius of bubbles in a sieve-plate tower, and the process is as follows: dividing two frequency bands of a bubble generation sound production area and a bubble breaking sound production area according to the frequency in an audible sound range [20-20,000] Hz; sound sensors are installed between the sieve-plate towers and / or in the middle of the height of a liquid layer, and sound signals of fluid in the towers in the driving process are collected; the collected sound signals are preprocessed; obtaining the dominant frequency of each sound wave pulsation in the sound signal by using a fast Fourier transform algorithm, determining whether the dominant frequency belongs to a bubble generation sound production area or a bubble breaking sound production area according to the frequency band in which the dominant frequency is located, and substituting the dominant frequency into a corresponding correlation formula to determine the radius of the bubble; and counting the number of pulse peaks in the bubble generation sound production area and the bubble breaking sound production area within the sample time, and respectively obtaining the generation number of bubbles and the breaking number of bubbles. And real-time monitoring of the number and size of bubbles in the sieve-plate tower in a driving state is realized.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production process monitoring, and in particular to a method and system for monitoring the number and radius of bubbles in a sieve plate tower. Background Art

[0002] In the chemical production process, sieve plate towers, as a common gas-liquid mass transfer equipment, are widely used in many fields such as petrochemicals, pharmaceuticals, and food. Their stable and efficient operation is crucial to product quality and production safety. Therefore, developing a fast, accurate, and efficient online monitoring method and system for real-time monitoring of the flow state and mixing degree of the fluid in the tower is crucial for accurately controlling production parameters, ensuring product quality, and reducing the possibility of accidents.

[0003] With the development of modern industry, higher requirements are placed on the monitoring technology of distillation towers. Although traditional monitoring methods such as the measurement of temperature, pressure, flow and other parameters can reflect the operating status of the equipment to a certain extent, they often have certain limitations. For example, the monitoring technologies such as temperature, pressure, and flow have the problem of low sensitivity, and some early and potential faults may not be detected in a timely and accurate manner. The currently developed ray monitoring technology is often limited in operating conditions, and the equipment costs and professional requirements for operators required by this technology are high. Therefore, it is not the most ideal choice for real-time monitoring of the tower operation process. As a non-invasive, long-distance, and real-time monitoring method, acoustic monitoring technology provides a new idea and method for real-time monitoring of the distillation process.

[0004] The fluid flow process in the distillation tower involves complex gas-liquid two-phase interactions, among which the number and size of bubbles are key parameters for measuring the gas-liquid contact state. For example, in petrochemicals, when crude oil is fractionated, accurate understanding of these parameters of bubbles in the tower can better control the fractionation process and improve the separation accuracy of different fractions. For example, the size and number of bubbles will affect the gas-liquid contact area and mass transfer efficiency. If the bubble size is large, the relative contact area is small, which may result in low mass transfer efficiency; if the number of bubbles is too large, it may cause liquid flooding or mist entrainment, affecting the separation effect and even causing unstable equipment operation. For the production of fine chemical products, such as pharmaceuticals, spices and other industries, the purity requirements of the products are extremely high. By reasonably adjusting the number, size and density of bubbles, the gas-liquid mass transfer efficiency can be improved and energy consumption can be reduced. For example, in large chemical plants, optimizing bubble parameters (optimizing bubble parameters refers to regulating the generation speed and size of bubbles) can enable the distillation tower to achieve the same separation effect at a lower reflux ratio, thereby reducing the consumption of heating steam and achieving energy conservation and emission reduction.

[0005] In addition, from the perspective of process optimization and energy conservation and emission reduction, the dynamic process of bubble generation and rupture in the sieve plate tower is the main source of sound in the tower. When bubbles are generated, gas enters the liquid phase from the sieve holes. This process will cause the bubble volume pulsation and the disturbance of the surrounding liquid, thereby generating sound of a specific frequency. At the moment of bubble rupture, the rapid change of the gas-liquid interface will release strong energy and produce more obvious sound. The sound signals generated by these bubble behaviors contain rich information about the mixing state of the fluid in the tower and the operating status of the equipment.

[0006] As chemical production develops towards intelligence and refinement, the bubble parameter information captured during equipment operation using passive acoustic monitoring technology can provide a key feedback data source for the automated control system. How to effectively use these passive acoustic monitoring data to obtain the number and radius of bubbles in the sieve plate tower, and then realize intelligent operation and optimized control of the distillation process, and promote chemical production to develop in the direction of higher quality and higher efficiency is a technical problem that needs to be solved urgently. Summary of the invention

[0007] The purpose of the present invention is to provide a method and system for monitoring the number and radius of bubbles in a sieve plate tower, which method and system realize real-time monitoring of the number and size of bubbles inside the sieve plate tower when the sieve plate tower is in operation.

[0008] To achieve the above object, the technical solution of the present invention is:

[0009] In a first aspect, the present invention provides a method for monitoring the number and radius of bubbles in a sieve plate tower, the process of the method is:

[0010] 1) The audible sound range [20-20,000] Hz is divided into two frequency bands according to the frequency size: the bubble generation sound zone and the bubble break sound zone, wherein [20-3,000] Hz is the bubble generation sound zone, and [3,000-20,000] Hz is the bubble break sound zone; sound sensors are installed between towers and / or at the middle position of the liquid layer height of the sieve plate tower to collect the sound signals of the internal fluid during the tower start-up process;

[0011] 2) Preprocess the collected sound signal to remove low-frequency noise and high-frequency interference components in the signal;

[0012] 3) Perform spectrum analysis on the preprocessed signal through the fast Fourier transform algorithm to obtain the main frequency of each sound wave pulsation in the sound signal. According to the frequency band in which the main frequency is located, it is determined whether it belongs to the bubble generation sound generation area or the bubble collapse sound generation area. If it is in the bubble generation sound generation area, the main frequency is the acoustic frequency f when the bubble is generated. d ; If it is located in the bubble generation and sound generation area, the main frequency is the acoustic frequency f when it breaks at the free interface b ;

[0013] For the bubble generation sound area, the bubble generation radius is calculated according to formula (1);

[0014]

[0015] For the bubble breaking sound area, the bubble breaking radius is calculated according to formula (2):

[0016]

[0017] Among them, R d is the bubble generation radius when the bubble detaches from the orifice (mm), R b is the bubble breaking radius at the bubble free interface (mm); ρ is the surrounding medium density (kg / m 3 ); P0 is the pressure acting on the bubble (Pa); γ is the ratio of the isobaric specific heat to the isochoric specific heat of the gas; f d is the acoustic frequency when the bubble is generated (Hz), f b is the acoustic frequency of the crushing at the free interface (Hz);

[0018] 4) Based on the preprocessed signal, the number of pulsation peaks in the bubble generation sound zone and the bubble breakage sound zone within the sample time is counted to obtain the number of bubble generation and the number of bubble breakage respectively, and then the bubble generation frequency and the bubble breakage frequency are calculated, that is, the number of bubbles generated or broken per second.

[0019] Further, γ=1.41, and P0 is the monitored pressure inside the tower.

[0020] 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 contents:

[0021] Constructing a simulation test bench, the simulation test bench comprising a tower body with a transparent sight glass, a high-speed camera for observing the size of bubbles in the tower, and a pressure sensor for monitoring the pressure in the tower body;

[0022] The bubble radius and the corresponding main frequency under different liquid media are obtained through the simulation test bench, and the current pressure acting on the bubble, the ratio of the isobaric specific heat to the isochoric specific heat of the gas γ, and the surrounding medium density ρ are recorded; the frequency bands are classified according to the main frequency into the bubble generation sound zone and the bubble breakage sound zone, and the bubble generation data set and the bubble breakage data set are constructed respectively;

[0023] Correlation and regression analysis were performed on the bubble generation data set and the bubble breakage data set to obtain the correlation formulas between the acoustic frequency and the bubble radius under different bubble behaviors.

[0024] After obtaining the corresponding main frequency through the sound signal, confirm which frequency band it belongs to, substitute it into the corresponding correlation formula to determine the size of its bubble radius; at the same time, count the number of pulsations in different frequency bands to obtain the number of bubbles in the frequency band.

[0025] In a third aspect, the present invention provides a system for monitoring the number and radius of bubbles in a sieve plate tower, the system comprising:

[0026] The sound monitoring device is used for collecting and transmitting the sound signal in the sieve plate tower, and mainly includes: a sound sensor for collecting the sound signal in the sieve plate tower, a signal amplifier for improving the signal-to-noise ratio of the sound signal, and a data acquisition card for temporarily storing the sound signal;

[0027] Pressure sensor, used to monitor the pressure inside the tower;

[0028] A preprocessing module is used to preprocess the collected sound signals;

[0029] A feature extraction module is used to extract acoustic frequency features from the preprocessed sound signal to obtain the main frequency;

[0030] Model building module, used to obtain the correlation formula between acoustic frequency and bubble radius under different bubble behaviors;

[0031] The model calculation module is used to determine the frequency band according to the main frequency, and then calculate the bubble radius according to the correlation formula of different frequency bands, and count the number of bubbles in the frequency band;

[0032] The display module is used to display the number of bubbles and bubble radius in different frequency bands.

[0033] Furthermore, at least one sound sensor is correspondingly arranged for each measuring point of the tower, and the number and layout of the sound sensors are optimized and adjusted according to the size of the tower and the monitoring requirements; the preprocessing module uses digital filtering technology and noise reduction algorithm to preprocess the sound signal;

[0034] The bubble radius is divided into a bubble generation radius and a bubble breakage radius, and the bubble generation frequency and the bubble breakage frequency are obtained according to the number of bubbles in different frequency bands within the statistical sample time.

[0035] The display module can display the waveform diagram, spectrum diagram, bubble generation frequency, acoustic frequency during bubble generation, bubble generation radius, bubble breakage frequency, acoustic frequency and breakage radius during bubble breakage at the free interface of the bubble sound signal at different measuring points in the tower.

[0036] Furthermore, the system is provided with a product discharge stability monitoring component, which monitors in real time whether the product discharge is stable at the initial stage of tower equipment operation;

[0037] Record the bubble radius range calculated at each measuring point of the tower equipment during the stable product discharge period, count the distribution of the bubble radius in the tower height direction, divide different radius intervals according to the bubble radius distribution, record the bubble radius range of each radius interval, and use this as the standard range; at the same time, count the number of bubbles in each radius interval, and use this as the bubble number threshold;

[0038] When it is detected that the bubble size exceeds the standard range of the corresponding position, it is considered that the bubble size is too large, and the heating capacity of the equipment reboiler is adjusted, the steam volume is increased, the gas velocity is accelerated, and the breakage is promoted; if the number of bubbles exceeds the bubble number threshold, the gas phase velocity is too high, which may easily lead to abnormal behaviors such as liquid flooding or mist entrainment in the equipment, then the heating capacity of the equipment reboiler should be reduced, or the feed flow rate should be increased, or the reflux ratio should be increased to maintain an appropriate gas-liquid ratio;

[0039] When it is detected that the size of the bubble when it is generated is smaller than the standard range of the corresponding position, and the size when it is broken is larger than the standard range of the corresponding position, it means that there is a lot of aggregation behavior of the bubbles. By adding defoaming agent or reducing the amount of steam, the bubble collision kinetic energy can be reduced until the product discharge remains stable.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention uses passive acoustic monitoring technology within the audible range for the first time to monitor the bubble generation and breakage behavior of the distillation process, that is, the application is within the audible range of the human ear, and the sound produced by the bubble itself is used for monitoring. Passive acoustics: refers to the sound generated by the bubble itself, which is collected and analyzed by the receiving device.

[0042] The present invention applies acoustic monitoring technology to fault diagnosis of distillation towers, and can perform non-destructive monitoring of bubbles during the continuous operation of industrial equipment such as distillation towers or reactors, and monitor the number and size of bubbles generated in the equipment. If they exceed normal values, the equipment operating parameters can be adjusted in time to ensure efficient production.

[0043] During the operation of the equipment, the internal fluid undergoes a complex turbulent process, and the main acoustic signal is generated by bubbles. However, the sound signal has many characteristics, including duration, amplitude, power spectrum density, frequency and other characteristics. This application creatively selects the main frequency as the acoustic frequency and the basis for dividing the frequency band, which can effectively capture the generated sound frequency and the broken sound frequency in the bubble group. Through experimental data analysis, the present invention finds that there is a close mathematical correlation between the acoustic frequency and the size of the bubble, and there are obvious differences in the frequency characteristics of the two processes of generation and fragmentation. By establishing a correlation between the acoustic frequency and the bubble size according to different frequency bands, even if the bubble generation and bubble fragmentation processes occur simultaneously, they can be accurately distinguished. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 1 is a schematic diagram of the structure of a system for monitoring the number and radius of bubbles in a sieve plate tower provided by an embodiment of the present invention;

[0045] Figure 2 This is a flowchart of a method for monitoring the number and radius of bubbles in a sieve plate tower provided by an embodiment of the present invention;

[0046] Figure 3 The invention provides an operation panel display of a monitoring system for the number and radius of bubbles in a sieve plate tower. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0048] In the present invention, frequency refers to the number of times an event occurs per second. Bubble break frequency refers to the number of bubbles that break per second. Break acoustic frequency (acoustic frequency when breaking at a free interface) refers to the fluctuating sound signal generated when a bubble breaks. The fluctuation is caused by the vibration of the bubble surface, and the number of vibrations per second is the acoustic frequency.

[0049] The present invention mainly identifies and monitors the size and number of internal bubbles during the operation of the tower equipment, and uses the monitoring results in the subsequent reaction regulation. For example, when it is detected that the bubble size is too large, it may be that the gas phase velocity is too low, which makes the bubbles not easy to break. The heating amount of the equipment reboiler can be adjusted, and the steam amount can be increased to speed up the gas velocity and promote breaking. If the number of bubbles is too large, it means that the gas phase velocity is too high, which is easy to cause abnormal behaviors such as liquid flooding or mist entrainment in the equipment. At this time, it is necessary to reduce the heating amount of the equipment reboiler, or increase the feed flow rate, or increase the reflux ratio to maintain a proper gas-liquid ratio. In addition, if it is detected that the size of the bubble is small when it is generated, and the size is large when it is broken, it means that there are more coalescence behaviors in the bubble, and the bubble collision kinetic energy can be reduced by adding an appropriate amount of defoaming agent or appropriately reducing the amount of steam. By adjusting the equipment operating parameters and controlling the bubble state (temperature control, feed rate control or other control means to achieve the size control of boiling bubbles in the tower), the entrainment of impurities can be reduced and the product quality can be improved.

[0050] Figure 1 1 is a schematic diagram of a tower monitoring system provided by an embodiment of the present invention. The tower monitoring system 10 is used to perform online real-time monitoring of the operation status of the tower, and timely discover the number of bubbles generated, the number of bubbles broken and the average size in the tower, so as to ensure product quality and improve the efficiency of tower operation. Figure 1The tower body 01 of the tower has multiple layers of test sections 02 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 test section 02. A monitoring sensor 110 is arranged corresponding to one measuring point, and the tower monitoring system 10 includes multiple monitoring sensors 110, and the multiple monitoring sensors 110 include multiple sound sensors. The monitoring system also includes a control device 120, which is electrically or wirelessly connected to the multiple monitoring sensors 110, respectively, and is used to obtain sound signals related to the internal operating status of the tower through the monitoring sensors 110, and determine the number of bubbles generated, the number of bubbles broken and the average size in the sieve plate tower according to the sound signals, so as to identify the distribution of bubbles inside the tower.

[0051] It should be noted that regarding the layout of the measuring points, Figure 1 Only a single measuring point is arranged on the outer wall of the tower body 01 corresponding to each section 02 to be tested. In other embodiments, a single or multiple measuring points may be arranged on each section 02 to be tested, and the operation status of the tower is monitored by placing a monitoring sensor 110 on the measuring point. Exemplarily, in this embodiment, the monitoring sensor 110 is a sound sensor. The sound sensor has the advantages of low cost, small size, and convenient installation, and is highly practical and can collect weak sound signals.

[0052] Example 1

[0053] The method for monitoring the number and radius of bubbles in a sieve plate tower of the present invention comprises the following steps:

[0054] 1) The audible sound range [20-20,000] Hz is divided into two frequency bands according to the frequency size: the bubble generation sound zone and the bubble break sound zone, wherein [20-3,000] Hz is the bubble generation sound zone, and [3,000-20,000] Hz is the bubble break sound zone; sound sensors are installed between towers and / or at the middle position of the liquid layer height of the sieve plate tower to collect the sound signals of the internal fluid during the tower start-up process;

[0055] 2) Preprocess the collected sound signal to remove low-frequency noise and high-frequency interference components in the signal;

[0056] 3) Perform spectrum analysis on the preprocessed signal through the fast Fourier transform algorithm to obtain the main frequency of each sound wave pulsation in the sound signal. According to the frequency band in which the main frequency is located, it is determined whether it belongs to the bubble generation sound generation area or the bubble collapse sound generation area. If it is in the bubble generation sound generation area, the main frequency is the acoustic frequency f when the bubble is generated. d ; If it is located in the bubble breaking sound area, the main frequency is the acoustic frequency f when the bubble breaks at the free interface b ;

[0057] For the bubble generation sound area, the bubble generation radius is calculated according to formula (1);

[0058]

[0059] For the bubble breaking sound area, the bubble breaking radius is calculated according to formula (2):

[0060]

[0061] Among them, R d is the bubble generation radius when the bubble detaches from the orifice (mm), R b is the bubble breaking radius at the bubble free interface (mm); ρ is the surrounding medium density (kg / m 3 ); P0 is the pressure acting on the bubble (Pa); γ is the ratio of the isobaric specific heat to the isochoric specific heat of the gas; f d is the acoustic frequency when the bubble is generated (Hz), f b is the acoustic frequency of the crushing at the free interface (Hz);

[0062] 4) Based on the preprocessed signal, the number of pulsation peaks in the bubble generation sound zone and the bubble breakage sound zone within the sample time is counted to obtain the number of bubble generation and the number of bubble breakage respectively, and then the bubble generation frequency and the bubble breakage frequency are calculated, that is, the number of bubbles generated or broken per second.

[0063] The installation position requirements of the sound sensor in the present invention are as follows: 1. The installation position is usually set between two layers of tower plates and in the middle of the liquid layer height. 2. The distribution number can be distributed at equal intervals according to the tower height, the number of tower plates and the demand. It is not necessary to install it on each layer, and the number is not limited. The tower body of the sieve plate tower has multiple layers of test sections arranged in parallel, and at least one measuring point is set on the outer wall of the tower body corresponding to each section to be tested; at least one sound sensor is set corresponding to each measuring point of the sieve plate tower, and the number and layout of the sound sensors are optimized and adjusted according to the size of the sieve plate tower and the monitoring requirements.

[0064] In the present invention, the collected sound signal is preprocessed, including pre-emphasis, filtering and noise reduction. The filtering is a bandpass filtering, which is used to remove low-frequency noise and high-frequency interference components in the signal. In this embodiment, the bandpass filter only allows signals in a specific frequency range of (100-18000) Hz to pass through. The pass range is set to 100-18000 Hz, and other signals captured in the signal below 100 Hz or above 18000 Hz will be directly filtered out; then the Wiener filtering technology is used to remove in-band noise interference, such as interference signals such as environmental noise, to further improve the signal-to-noise ratio of the signal.

[0065] The reliability of the method of the present invention has been proven through a large number of experiments, and the monitoring of the number and size of bubbles in the tower based on sound signal analysis technology has been realized. This technology will provide an important reference for the use of sound signals for online monitoring of other types of bubbling equipment.

[0066] Example 2

[0067] The system for monitoring the number and radius of bubbles in the sieve plate tower of this embodiment comprises:

[0068] The sound monitoring device is used for collecting and transmitting the sound signal in the sieve plate tower, and mainly includes: a sound sensor for collecting the sound signal in the sieve plate tower, a signal amplifier for improving the signal-to-noise ratio of the sound signal, and a data acquisition card for temporarily storing the sound signal;

[0069] Pressure sensor, used to monitor the pressure inside the tower;

[0070] A preprocessing module is used to preprocess the collected sound signals;

[0071] A feature extraction module is used to extract acoustic frequency features from the preprocessed sound signal to obtain the main frequency;

[0072] Model building module, used to obtain the correlation formula between acoustic frequency and bubble radius under different bubble behaviors;

[0073] The model calculation module is used to determine the frequency band according to the main frequency, and then calculate the bubble radius according to the correlation formula of different frequency bands, and count the number of bubbles in the frequency band;

[0074] The display module is used to display the number of bubbles and bubble radius in different frequency bands. The identification system of the number and size of bubbles in the sieve plate tower is based on the acoustic frequency.

[0075] In the present invention, one measuring point is correspondingly provided with a sound sensor, and multiple monitoring measuring points include multiple sound sensors, and the sound sensors are used to collect sound signals in the sieve plate tower;

[0076] The above-mentioned preprocessing module, feature extraction module, model building module, model calculation module, and display module constitute a control device, which is electrically or wirelessly connected to the sound sensor to obtain the sound signal of the bubble size distribution inside the associated sieve plate tower.

[0077] The display module can show the waveform diagram, spectrum diagram, bubble generation frequency, acoustic frequency during bubble generation, bubble generation radius, bubble breakage frequency, acoustic frequency and breakage radius during breakage at the free interface, etc. of the bubble sound signal at different measuring points in the tower. The intuitive display of relevant information allows the operator to understand the status of the bubbles in the sieve plate tower in real time.

[0078] Example 3

[0079] The steps of the monitoring method of this embodiment are:

[0080] T1: Connect a sound sensor at a predetermined position on the outer wall of the tower to collect the sound signal of the internal fluid during the tower start-up process;

[0081] T2: Preprocess the collected sound signals, including pre-emphasis, filtering and noise reduction.

[0082] T3: The preprocessed sound signal is transformed from the time domain to the frequency domain through the fast Fourier transform algorithm, the frequency characteristics of the sound signal are extracted, and the main frequency of all sound wave pulsations in the sound segment is obtained;

[0083] T4: Define the frequency ranges corresponding to the two behaviors of bubble generation and bubble breakage; Based on a large number of experimental studies that prove that the sound frequency ranges of bubble generation and bubble breakage are different, [20-3,000] Hz is defined as the bubble generation sound zone, and (3,000-20,000] Hz is defined as the bubble breakage sound zone. Depending on the frequency band in which the main frequency is located, it is determined whether it belongs to the bubble generation sound zone or the bubble breakage sound zone. If it is in the bubble generation sound zone, the main frequency is the acoustic frequency f when the bubble is generated. d ; If it is located in the bubble breaking sound area, the main frequency is the acoustic frequency f when the bubble breaks at the free interface b ;

[0084] T5: Based on the preprocessed signal, the number of pulsation peaks in the bubble generation sound zone and the bubble collapse sound zone within the sample time is counted, and the bubble generation frequency and bubble collapse frequency are calculated respectively.

[0085] T6: Calculate the bubble radius according to the correlation formula of different frequency bands, and count the number of bubbles in the frequency band.

[0086] The tower is a sieve plate tower type, and the tower body has multiple layers of test sections arranged in parallel. At least one sound signal measuring point is arranged on the outer wall of the tower body corresponding to each of the test sections, and the sound signal is monitored at each measuring point.

[0087] The sound sample collection interval and sampling duration can be adjusted according to monitoring requirements.

[0088] Count the number of pulsations in different frequency bands of the sound clip to indicate the number of bubbles that have this behavior.

[0089] The formula for relating acoustic frequency to bubble radius is as follows:

[0090] Bubble generation sound area:

[0091]

[0092] Bubble breaking sound area:

[0093]

[0094] Where R d is the bubble generation radius when the bubble detaches from the orifice (mm), R b is the bubble breaking radius at the bubble free interface (mm), ρ is the surrounding medium density (kg / m 3 ), P0 is the pressure acting on the bubble (Pa), γ is the ratio of the isobaric specific heat to the isochoric specific heat of the gas. For air under standard conditions, γ = 1.41, f d is the acoustic frequency when the bubble is generated (Hz), f b is the acoustic frequency (Hz) at the free interface when it is broken (obtained by performing the above FFT transformation using Matlab software after acoustic signal preprocessing). Density, pressure, and specific heat ratio are different for different substances. When the substance type is determined, the density and specific heat ratio can be considered as constants.

[0095] The embodiment of the present invention arranges multiple layers of sections to be tested on the tower body, and arranges at least one measuring point on the outer wall of the tower body corresponding to each section to be tested, so that the tower monitoring system collects the sound signal of the bubble state inside the tower through the sound sensor arranged on the measuring point, and transmits it to the control device. The control device analyzes the bubble sound time domain and frequency domain characteristics according to the acquired sound signal, counts the number of bubbles generated and broken within a unit time (1s), and calculates the bubble radius according to the bubble acoustic frequency to identify the bubble state inside the tower. The embodiment of the present invention realizes the online detection of the mixing state of the internal materials of the chemical tower during operation by acquiring, real-time monitoring and dynamic analysis of the sound signals generated during the operation of the chemical tower, providing a strong guarantee for the efficient and safe operation of the chemical tower. The system is mainly composed of sound sensors, which effectively reduces the cost and solves the problem of high cost of the current chemical tower operation status monitoring equipment; the internal operation status of the tower is identified according to the sound signals of multiple sections to be tested, which improves the monitoring accuracy and solves the problem of low accuracy of the existing monitoring equipment.

[0096] Example 4

[0097] The embodiment of the present invention provides a method for monitoring the number of bubbles and bubble radius inside a distillation tower based on acoustic frequency characteristics. The method comprises the following steps: obtaining the sound signal of the internal fluid of the tower when the tower is in operation through a microphone array; extracting the frequency characteristics of the sound signal; defining the sound frequency interval corresponding to the bubble generation and breakup behavior; counting the number of pulsations in different frequency bands to represent the number of bubbles in the frequency band; and calculating the generation radius and breakage radius of the bubbles in the tower according to the correlation formula between the sound frequency and the bubble radius under different bubble behaviors.

[0098] The present invention adopts passive acoustic non-destructive monitoring technology, which does not require invasive operation on the tower. It can monitor the number and size of internal bubbles during the operation of the black box model tower, further understand the mixing state and reaction degree of the internal fluid, and realize online detection and precise control of the operating state of the chemical tower.

[0099] For example, Figure 1 In the tower monitoring system 10 shown, in actual application, for a small or pilot test tower, a wired signal transmission method can be used to realize data transmission between the sound sensor 110 and the control device 120, that is, a control device 120 is separately configured for each tower. For industrial equipment-level towers, a central control room can be configured for several towers, and wireless short-distance communication is used between each measuring point of the tower and the host computer (control device 120) to realize data transmission.

[0100] Exemplarily, sensors with wireless communication functions may be installed at each measuring point, and data may be transmitted through, for example, wireless short-range communication methods such as Bluetooth and WiFi.

[0101] For example, Figure 2 1 is a flow chart of a monitoring method adopted by a tower monitoring system provided by an embodiment of the present invention. The method comprises the following steps:

[0102] S21, obtaining a sound signal associated with the state of bubbles inside the tower transmitted by a sound sensor;

[0103] S22, preprocessing the sound signal by filtering enhancement and wavelet noise reduction to obtain a pure sound signal;

[0104] First, the single-channel sound signal transmitted by each sound sensor is preprocessed. Since the sound of the tower's internal operating status detected by the sound sensor on the tower wall is a weak signal, it will be drowned by the environmental noise, so preprocessing such as windowing, framing, and noise reduction enhancement is required. For example, the frame length is selected as 10ms, the delay between frames is 5ms, and the observed signal x(n):

[0105] x(n)=s(n)+d(n) (3)

[0106] Among them, s(n) is the pure sound signal, d(n) is the environmental noise, and the observed signal is sampled at 44.1kHz and encoded at 16bit. The length of each frame of the sound signal is L=512, and the number of frames depends on the total duration of the test signal, which is set to M. The Wiener filter technology is used to remove the environmental noise, and the optimal solution under the minimum square error is obtained by solving the Wiener-Hopf equation as the estimated signal of the pure sound signal. y(n) is the preprocessed signal.

[0107] S23. Perform fast Fourier transform (FFT) on the preprocessed signal y(n) according to formula (4), transform the signal from time domain to frequency domain, analyze the characteristic information of the sound signal in time domain and frequency domain, such as the frequency, resolution, amplitude, phase and other information of the sound signal, and obtain the frequency characteristics of the bubble, i.e., the main frequency.

[0108]

[0109] The above formula is the Fourier series of the periodic sequence. It is expressed as a base frequency sequence, j is an imaginary unit, and k is a frequency index (0≤k≤N-1); this formula means that the sequence Convert from time domain to frequency domain, where Represents the kth frequency component in the frequency domain; is the nth sequence in the time domain, N is the number of periods, and ω(n) is the window function.

[0110] After the sound signal is transformed by formula (4), it changes from the initial pulsating waveform diagram to a frequency peak diagram, indicating the size of the components of this sound signal at each frequency. The one with the highest peak is the main frequency.

[0111] S24. Count the number of pulsations in different frequency bands in the sound sample, and calculate the bubble generation frequency and bubble collapse frequency.

[0112] S25, using the main frequency obtained in S23 to calculate the size radius of the bubble generation process and the size radius of the bubble collapse process according to formula (1) and formula (2) respectively, so as to identify the material mixing state inside the tower.

[0113] In an actual scenario, the tower monitoring method and system provided by the embodiment of the present invention are used to monitor a tower having a diameter of The internal bubble distribution state of a medium-sized experimental tower is monitored. The layout of the monitoring sensors in the monitoring system refers to Figure 1 , provide relevant test data, take monitoring the operating status at the corresponding position of one of the sections to be tested in the tower as an example, to prove that the acoustic signals of bubbles in different states are different, thereby confirming the reliability of the tower monitoring method based on sound signal analysis technology provided in this embodiment.

[0114] Figure 3The monitoring panel of the bubble size in the sieve plate tower provided by the embodiment of the present invention, i.e., the display module, can independently set the acoustic signal sampling interval and sampling time according to the implementation needs, and the sound samples are stored in .wav format. The monitoring panel can obtain the waveform diagram and spectrum diagram of the sound signal. The system can count the number of bubbles in each frequency band within the sample time according to the preset frequency range, and calculate the bubble generation frequency and the bubble crushing frequency. In addition, according to the set formula (1) and formula (2), the average generation radius and the average crushing radius of the bubbles in the tower, i.e., the bubble generation radius and the bubble crushing radius, are obtained.

[0115] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

[0116] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for monitoring the number and radius of bubbles in a sieve plate tower, characterized in that: The process of the method is: 1) The audible sound range [20-20,000] Hz is divided into two frequency bands according to the frequency size: the bubble generation sound zone and the bubble break sound zone, wherein [20-3,000] Hz is the bubble generation sound zone, and [3,000-20,000] Hz is the bubble break sound zone; sound sensors are installed between towers and / or at the middle position of the liquid layer height of the sieve plate tower to collect the sound signals of the internal fluid during the tower start-up process; 2) Preprocess the collected sound signal to remove low-frequency noise and high-frequency interference components in the signal; 3) Perform spectrum analysis on the preprocessed signal through the fast Fourier transform algorithm to obtain the main frequency of each sound wave pulsation in the sound signal. According to the frequency band in which the main frequency is located, it is determined whether it belongs to the bubble generation sound generation area or the bubble collapse sound generation area. If it is in the bubble generation sound generation area, the main frequency is the acoustic frequency f when the bubble is generated. d ; If it is located in the bubble generation and sound generation area, the main frequency is the acoustic frequency f when it breaks at the free interface b ; For the bubble generation sound area, the bubble generation radius is calculated according to formula (1); For the bubble breaking sound area, the bubble breaking radius is calculated according to formula (2): Among them, R d is the bubble generation radius when the bubble detaches from the orifice (mm), R b is the bubble breaking radius at the bubble free interface (mm); ρ is the surrounding medium density (kg / m 3 ); P0 is the pressure acting on the bubble (Pa); γ is the ratio of the isobaric specific heat to the isochoric specific heat of the gas; f d is the acoustic frequency when the bubble is generated (Hz), f b is the acoustic frequency of the crushing at the free interface (Hz); 4) Based on the preprocessed signal, the number of pulsation peaks in the bubble generation sound zone and the bubble breakage sound zone within the sample time is counted to obtain the number of bubble generation and the number of bubble breakage respectively, and then the bubble generation frequency and the bubble breakage frequency are calculated, that is, the number of bubbles generated or broken per second.

2. The monitoring method according to claim 1, characterized in that: γ=1.41, P0 is the monitored pressure inside the tower.

3. A method for monitoring the number and radius of bubbles in a sieve plate tower, characterized in that: The method comprises the following: Constructing a simulation test bench, the simulation test bench comprising a tower body with a transparent sight glass, a high-speed camera for observing the size of bubbles in the tower, and a pressure sensor for monitoring the pressure in the tower body; The bubble radius and the corresponding main frequency under different liquid media are obtained through the simulation test bench, and the current pressure acting on the bubble, the ratio of the isobaric specific heat to the isochoric specific heat of the gas γ, and the surrounding medium density ρ are recorded; the frequency bands are classified according to the main frequency into the bubble generation sound zone and the bubble breakage sound zone, and the bubble generation data set and the bubble breakage data set are constructed respectively; Correlation and regression analysis were performed on the bubble generation data set and the bubble breakage data set to obtain the correlation formulas between the acoustic frequency and the bubble radius under different bubble behaviors. After obtaining the corresponding main frequency through the sound signal, confirm which frequency band it belongs to, substitute it into the corresponding correlation formula to determine the size of its bubble radius; at the same time, count the number of pulsations in different frequency bands to obtain the number of bubbles in the frequency band.

4. A system for monitoring the number and radius of bubbles in a sieve plate tower, characterized in that: The system comprises: The sound monitoring device is used for collecting and transmitting the sound signal in the sieve plate tower, and mainly includes: a sound sensor for collecting the sound signal in the sieve plate tower, a signal amplifier for improving the signal-to-noise ratio of the sound signal, and a data acquisition card for temporarily storing the sound signal; Pressure sensor, used to monitor the pressure inside the tower; A preprocessing module is used to preprocess the collected sound signals; A feature extraction module is used to extract acoustic frequency features from the preprocessed sound signal to obtain the main frequency; Model building module, used to obtain the correlation formula between acoustic frequency and bubble radius under different bubble behaviors; The model calculation module is used to determine the frequency band according to the main frequency, and then calculate the bubble radius according to the correlation formula of different frequency bands, and count the number of bubbles in the frequency band; The display module is used to display the number of bubbles and bubble radius in different frequency bands.

5. The system according to claim 4, characterized in that At least one sound sensor is correspondingly arranged at each measuring point of the tower, and the number and layout of the sound sensors are optimized and adjusted according to the size of the tower and the monitoring requirements; the preprocessing module uses digital filtering technology and noise reduction algorithm to preprocess the sound signal; The bubble radius is divided into a bubble generation radius and a bubble breakage radius, and the bubble generation frequency and the bubble breakage frequency are obtained according to the number of bubbles in different frequency bands within the statistical sample time. The display module can display the waveform diagram, spectrum diagram, bubble generation frequency, acoustic frequency during bubble generation, bubble generation radius, bubble breakage frequency, acoustic frequency during bubble breakage at the free interface and breakage radius of the bubble sound signal at different measuring points in the tower.

6. The system according to claim 4, characterized in that The system is provided with a product discharge stability monitoring component, which monitors in real time whether the product discharge is stable in the initial operation of the tower equipment; Record the bubble radius range calculated at each measuring point of the tower equipment during the stable product discharge period, count the distribution of the bubble radius in the tower height direction, divide different radius intervals according to the bubble radius distribution, record the bubble radius range of each radius interval, and use this as the standard range; at the same time, count the number of bubbles in each radius interval, and use this as the bubble number threshold; When the bubble size is detected to exceed the standard range of the corresponding position, it is considered that the bubble size is too large, and the heating amount of the equipment reboiler is adjusted to increase the steam volume, speed up the gas velocity, and promote breakage; If the number of bubbles exceeds the threshold value of the number of bubbles, the gas phase velocity is too high, which may easily lead to abnormal behaviors such as flooding or mist entrainment in the equipment. In this case, the heating capacity of the equipment reboiler should be reduced, or the feed flow rate should be increased, or the reflux ratio should be increased to maintain an appropriate gas-liquid ratio. When it is detected that the size of the bubble when it is generated is smaller than the standard range of the corresponding position, and the size when it is broken is larger than the standard range of the corresponding position, it means that there is a lot of aggregation behavior of the bubbles. By adding defoaming agent or reducing the amount of steam, the bubble collision kinetic energy can be reduced until the product discharge remains stable.

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