An active vibration wave liquid level measurement method for pressure vessels used in the alumina industry

Abstract

This invention discloses an active vibration wave liquid level measurement method for pressure vessels used in the alumina industry. A vibration source and a sound-sensing element are installed at the bottom of the pressure vessel. The acoustic characteristics of this vibration source are significantly different from the acoustic waves of the alumina production process environment. Based on the change in the frequency of the acoustic waves generated by the contact between the vibration source and the medium inside the vessel, a conversion is performed using the acoustic frequency-liquid level characteristic curve. This enables non-invasive real-time liquid level monitoring of the pressure vessel under environmental interference during production operation. This invention not only solves the problem of difficult liquid level measurement in pressure vessels under harsh conditions such as high temperature, high pressure, strong acids, and strong alkalis in alumina production processes, greatly reducing the impact of the working environment on liquid level measurement, but also significantly reduces the cost of liquid level measurement. It is simple to operate, convenient to use, and consumes no additional energy during operation, making liquid level measurement in pressure vessels used in the alumina industry more efficient, reliable, energy-saving, and safe.

Description

Technical Field

[0001] This invention relates to a liquid level measurement method, and more particularly to an active vibration wave liquid level measurement method for pressure vessels used in the alumina industry. Background Technology

[0002] Pressure vessels in the alumina industry are commonly used in critical alumina production processes such as leaching, evaporation, and sedimentation. They require high strength and chemical stability, and the working media they contain are complex, including high-temperature, high-pressure, and highly alkaline gases, liquids, or liquid-solid mixtures. During operation, surrounding equipment (such as centrifugal pumps, vacuum pumps, and air compressors) generates noise, which can affect control or measurement components that rely on sound wave frequencies. Furthermore, the harsh internal environment of pressure vessels—high temperature, high pressure, strong acids, and strong alkalis—means that level measuring instruments in direct contact with the container's internal medium are at risk of corrosion, affecting measurement accuracy and reliability. This places high demands on the materials used in level measuring instruments. Therefore, a non-invasive measurement method resistant to environmental interference is preferable for level measurement in pressure vessels used in the alumina industry, avoiding contamination and accuracy degradation caused by direct contact with the measured liquid. Currently, commonly used non-invasive liquid level measurement methods for pressure vessels mainly utilize various principles such as radiation, electromagnetic waves, and light to indirectly obtain the liquid level value inside the vessel. Examples include radar liquid level measurement, ultrasonic liquid level measurement, and nuclear radiation liquid level measurement. Radar liquid level measurement uses microwave radar technology, while nuclear radiation liquid level measurement utilizes the principle that the intensity of nuclear radiation passing through materials varies with the thickness of the material layer. Both of these methods offer high accuracy but are relatively expensive, and nuclear radiation liquid level measurement poses certain safety hazards. Ultrasonic liquid level measurement utilizes the propagation characteristics of ultrasonic waves. While this method is easy to implement and moderately cost-effective, it is prone to errors when measuring volatile or foamy liquids.

[0003] Our team previously developed a method for measuring the liquid level of pressure vessels used in the alumina industry and applied for related patents. This technology discloses a method for measuring the liquid level of pressure vessels used in the alumina industry: based on the relationship between the sound waves generated during the flow of the medium in the pressure vessel and the liquid level characteristics of the medium inside the vessel, a sound-sensing element is installed at the bottom of the pressure vessel. The sound wave echo received by this element is converted with the obtained standard characteristic relationship between sound wave frequency and liquid level height to obtain the liquid level height. This method can effectively solve the problem of liquid level measurement in pressure vessels. However, when used in noisy environments or when the flow rate of the medium inside the vessel is slow, the measurement results still have some deviation. Summary of the Invention

[0004] The purpose of this invention is to provide an active vibration wave liquid level measurement method for pressure vessels used in the alumina industry. The principle of this method is based on the physical characteristics of sound wave reflection. According to the characteristic relationship between the change in echo frequency generated by the vibration source in the medium inside the vessel and the liquid level height inside the vessel, non-invasive real-time monitoring of the liquid level in the pressure vessel is achieved.

[0005] The technical solution of this invention is an active vibration wave liquid level measurement method for pressure vessels used in the alumina industry. A vibration source and a sound sensing element are set at the bottom of the pressure vessel. The acoustic characteristics of the vibration source are very different from the acoustic environment of the alumina industry production process. Based on the change in the frequency of the acoustic wave generated by the contact between the vibration source and the medium inside the container, the method is converted by referring to the acoustic frequency-liquid level characteristic curve. This enables non-invasive real-time liquid level monitoring of the pressure vessel under environmental interference during production operation.

[0006] The specific steps of the aforementioned active vibration wave liquid level measurement method for pressure vessels used in the alumina industry are as follows:

[0007] (1) A vibration source and a sound sensing element that are different from the ambient sound waves in the alumina industry are set at the bottom of the pressure vessel. The distance from the horizontal plane where the vibration source and the sound sensing element are located to the liquid surface of the medium in the vessel is the height H of the liquid surface to be measured.

[0008] (2) The vibration source outputs vibration in a fixed frequency band P0 = [a,b]. The vibration beam propagates in the container medium and is reflected back at the liquid surface. The reflected echo is received by the sound sensing element and transmitted to the liquid level measurement data backend for processing. The liquid level height H to be measured is obtained by converting the relationship between the sound wave frequency and the liquid level height.

[0009] In the aforementioned active vibration wave liquid level measurement method for pressure vessels used in the alumina industry, the echo P received by the acoustic sensor... r Extract the maximum peak value segment {P} within the vibration wave frequency range [a,b]. r (x), x = a, ..., b}, filter out noise and retain valid data.

[0010] In the aforementioned active vibration wave liquid level measurement method for pressure vessels used in the alumina industry, the relationship between the sound wave frequency and the liquid level height characteristic curve can be expressed by the formula... It means that among them The value is related to the medium inside the container and the container wall thickness, and is taken as an average. As the final liquid level value, in the above formula, H is the height of the liquid level to be measured; T is the temperature of the liquid to be measured; K is the correction coefficient, with a value ranging from 0.01 to 2.5; X is the sampling array; P r - The total attenuated audio amplitude received by the sound sensor; P0 - The amplitude of the original sound wave frequency generated by the flow; Z m- Acoustic impedance of the medium container; w - Attenuation coefficient.

[0011] In the aforementioned active vibration wave liquid level measurement method for pressure vessels used in the alumina industry, the correction coefficient K is related to the sound wave influencing factors: internal pressure of the vessel, medium temperature, and impurity deposition. Where P i P is the internal pressure of the container. s The pressure is standard atmosphere, and ΔT is the difference between the actual temperature and the temperature under standard conditions. When the contents of the container are gas, liquid, and slurry, A is taken as 0.5, 1, and 2, respectively.

[0012] In the aforementioned active vibration wave liquid level measurement method for pressure vessels used in the alumina industry, the vibration source and the sound sensing element are installed inside the soundproof enclosure.

[0013] In the aforementioned active vibration wave liquid level measurement method for pressure vessels used in the alumina industry, the reflected echo is received by a sound sensing element and transmitted to the liquid level measurement data backend for processing through a sensor, thereby obtaining the liquid level height H to be measured. The liquid level height H to be measured is displayed through the on-site liquid level display screen.

[0014] The beneficial effects of the present invention are as follows: Compared with the prior art, the present invention has the following advantages due to the adoption of the above-mentioned technical solution:

[0015] ① Non-invasive liquid level measurement has a wider range of applications, no special requirements for the medium itself, and is suitable for alumina production processes;

[0016] ② It has a low dependence on environmental noise and the flow rate and pressure of the medium inside the pressure vessel. The introduction of active vibration results in higher measurement accuracy and a larger measurement range of liquid level.

[0017] ③ The principle is simple, the components used are common and universal, and the cost is low;

[0018] ④ The liquid level measurement process does not involve high additional energy consumption from radar, sonar, electromagnetic fields, or radiation, resulting in low operating costs and high safety performance;

[0019] ⑤ By utilizing the relationship between the sound waves generated by the vibration source installed at the bottom of the pressure vessel and the liquid level of the medium inside the vessel, real-time monitoring can be achieved with high accuracy.

[0020] In summary, this invention achieves real-time liquid level monitoring based on the characteristic relationship between the acoustic echo generated during vibration at the bottom of the pressure vessel and the liquid level of the medium inside the vessel. The principle is simple, easy to use, significantly reduces the cost of liquid level measurement, is inexpensive, and has low additional energy consumption during operation. This makes the liquid level measurement of pressure vessels used in the alumina production process more efficient, reliable, energy-saving, and safe, with more accurate measurement results. The error range can be controlled within 1% to 2%, which is less than the error standard of most liquid level gauge measurement methods on the market. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the present invention.

[0022] Attached reference numerals: 1-Vibration source, 2-Sound sensing element, 3-Soundproof enclosure, 4-Sensor, 5-Liquid level measurement data backend, 6-On-site liquid level display screen. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0024] An embodiment of the present invention: An active vibration wave liquid level measurement method for pressure vessels used in the alumina industry. A vibration source 1 and a sound sensing element 2 are set at the bottom of the pressure vessel, and both are equipped with a soundproof cover 3. The vibration source 1 vibrates at a fixed frequency and force. The acoustic characteristics of the vibration source 1 are very different from the acoustic waves of the alumina industry production process environment. The sound waves emitted by the vibration source 1 within the fixed frequency band propagate through the container wall to the liquid surface, are reflected at the liquid surface, and form echoes. The sound sensing element 2 collects the echoes and converts them into electrical signals of different amplitudes. The sensor 4 transmits the acoustic wave electrical signals generated by the medium in the pressure vessel during the vibration process received by the sound sensing element 2 to the liquid level measurement data backend 5. The liquid level measurement data backend 5 automatically processes the data according to the standard characteristic relationship between echo frequency and liquid level height. During production operation, it realizes non-invasive real-time liquid level monitoring of the pressure vessel under environmental interference, obtains the liquid level height H to be measured, and returns the liquid level height H to the on-site liquid level display screen 6 and the control center in digital form.

[0025] The specific steps are as follows:

[0026] (1) A vibration source 1 and a sound sensing element 2, which are different from the ambient sound waves in the alumina industry, are set at the bottom of the pressure vessel. The distance from the horizontal plane where the vibration source 1 and the sound sensing element 2 are located to the liquid surface of the medium in the vessel is the height H of the liquid surface to be measured.

[0027] (2) Vibration source 1 outputs vibration in a fixed frequency band P0 = [a,b]. The vibration beam propagates in the container medium and is reflected back at the liquid surface. The reflected echo is received by the sound sensing element 2 and transmitted to the liquid level measurement data backend 5 through the sensor 4 for processing. The liquid level measurement data backend 5 uses the relationship between the sound wave frequency and the liquid level height characteristic curve to calculate the liquid level height H to be measured.

[0028] The echo P received by the sound sensor 2 r Extract the maximum peak value segment {P} within the vibration wave frequency range [a,b]. r The data (x), x = a, ..., b}, needs to be processed by the liquid level measurement data backend 5 to filter out noise and retain valid data.

[0029] The relationship between sound wave frequency and liquid level height characteristic curve can be expressed by the formula. It means that among them The value is related to the medium inside the container and the container wall thickness, and is taken as an average. As the final liquid level value, in the above formula, H is the height of the liquid level to be measured; T is the temperature of the liquid to be measured; K is the correction coefficient, with a value ranging from 0.01 to 2.5; X is the sampling array, for example, if there are 'a' sampling results, all the results are aggregated into an array X, and the average value of this array is taken as the average acoustic result; P r - The total attenuated audio amplitude received by the sound sensor; P0 - The amplitude of the original sound wave frequency generated by the flow; Z m - Acoustic impedance of the medium container; w - Attenuation coefficient.

[0030] The key technology of the above method lies in the frequency detection and data processing of the vibration wave echo. The established formula for the relationship between the sound wave frequency and the liquid level height standard characteristic curve is derived from the average value of multiple experimental measurements and the results of linear fitting statistical analysis. This reduces the measurement error caused by medium sedimentation and temperature changes in the container to a certain extent, and controls the error range to 1% to 2%, which is less than the error standard of most liquid level gauge measurement methods on the market.

[0031] Because vibration waves may encounter factors such as alumina impurity deposition, alkaline bubbles, and container wall thickness when propagating inside a pressure vessel, the vibration waves and reflected echoes do not always propagate perpendicularly. The attenuation effect during beam propagation is represented by a correction factor K, thereby reducing measurement errors caused by uncertainties. The correction factor K is related to the following factors affecting the sound waves: container internal pressure, medium temperature, and impurity deposition. Where P i P is the internal pressure of the container. s The pressure is standard atmosphere, and ΔT is the difference between the actual temperature and the temperature under standard conditions. When the contents of the container are gas, liquid, and slurry, A is taken as 0.5, 1, and 2, respectively.

[0032] When impurities accumulate at the bottom of the container, the acoustic frequency at the boundary between the impurities and the test medium weakens. At this point, it is necessary to continuously move the acoustic sensor along the outer wall of the pressure vessel to observe changes in the acoustic signal, performing multiple measurements to roughly locate the solid-liquid interface of the impurity deposition (below the critical deposition point below the liquid level, where the acoustic frequency is relatively stable and no longer changes), rather than directly measuring the liquid level. After obtaining an estimated value of the deposition interface height, the liquid level inside the container can then be measured and calculated. 液-固 The value is taken as 1.8 to 2.5 based on the deposition height.

[0033] The vibration source and sound-sensing element are located inside the soundproof enclosure to avoid the influence of external environmental noise.

[0034] Taking the evaporator in the evaporation workshop of a Bayer alumina plant as an example, this evaporator is a split-type tubular falling film evaporator with an elliptical head and conical bottom structure, a diameter of 5m, a straight section height of 5m, an operating pressure of 0.5MPa, and an operating temperature of 158℃. The medium inside the tank is sodium aluminate solution and steam. Typically, nuclear radiation level gauges are used for measurement, which are expensive. Furthermore, due to the presence of nuclear radiation, a nuclear source must be installed, making operation complex and requiring cumbersome approval procedures for safety. After installing a level gauge using this method, real-time level measurement can be achieved with an accuracy of ±5%, and it is inexpensive, easy to operate, and safe.

Claims

1. An active vibration wave liquid level measurement method for pressure vessels used in the alumina industry, characterized in that: A vibration source and a sound sensing element are installed at the bottom of the pressure vessel. The acoustic characteristics of the vibration source are different from the ambient sound waves in the alumina industry production process. Based on the change in the frequency of the sound waves generated by the contact between the vibration source and the medium inside the vessel, the conversion is performed by referring to the characteristic curve of sound wave frequency-liquid level. During production operation, non-invasive real-time liquid level monitoring of the pressure vessel under environmental interference is realized. The specific steps are as follows: (1) A vibration source and sound sensing element different from the ambient sound waves in the alumina industry are set at the bottom of the pressure vessel. The distance from the horizontal plane where the vibration source and sound sensing element are located to the liquid surface of the medium in the vessel is the height H of the liquid surface to be measured. (2) The vibration source outputs vibration in a fixed frequency band P0=[a, b]. The vibration beam propagates in the container medium and is reflected back at the liquid surface. The reflected echo is received by the sound sensing element and transmitted to the liquid level measurement data backend for processing. The liquid level height H to be measured is obtained by converting the relationship between the sound wave frequency and the liquid level height. The relationship between sound wave frequency and liquid level height characteristic curve can be expressed by the formula. It means that among them The value is related to the medium inside the container and the container wall thickness, and is taken as an average. As the final liquid level value, in the above formula, H is the height of the liquid level to be measured; T is the temperature of the liquid to be measured; K is the correction coefficient, with a value ranging from 0.01 to 2.5; X is the sampling array; P r -The total attenuated audio amplitude received by the sound sensor; P0 - The flow generates the original acoustic wave frequency amplitude; Z m - Acoustic impedance of the dielectric container; w - Attenuation coefficient; The correction factor K is related to the factors affecting sound waves: internal pressure of the container, temperature of the medium, and impurity deposition. , where P i P is the internal pressure of the container. s The pressure is standard atmosphere, and ΔT is the difference between the actual temperature and the temperature under standard conditions. When the contents of the container are liquid and slurry, A is taken as 1 and 2 respectively.

2. The active vibration wave liquid level measurement method for pressure vessels used in the alumina industry according to claim 1, characterized in that: The echo P received by the sound sensing element r Extract the maximum peak value segment {P} within the vibration wave frequency range [a, b]. r (x), x=a, ..., b}, filter out noise and retain valid data.

3. The active vibration wave liquid level measurement method for pressure vessels used in the alumina industry according to claim 1, characterized in that: The vibration source and sound-sensing element are located inside the soundproof enclosure.

4. The active vibration wave liquid level measurement method for pressure vessels used in the alumina industry according to claim 1, characterized in that: The reflected echo is received by the sound sensing element and transmitted to the liquid level measurement data backend for processing through the sensor, thereby obtaining the liquid level height H to be measured. The liquid level height H to be measured is displayed through the on-site liquid level display screen.

Images