A method for measuring liquid level in pressure vessels used in the alumina industry.

Abstract

This invention discloses a method for measuring the liquid level of pressure vessels used in the alumina industry. The medium in the alumina pressure vessel generates sound waves during flow, and the frequency of these sound waves is related to the liquid level within the vessel. A sound-sensing element is installed at the bottom of the pressure vessel to receive these sound waves. The method then converts the sound wave frequency to the liquid level using a pre-established formula. This allows for non-invasive, real-time monitoring of the liquid level during production. This invention achieves non-invasive liquid level measurement based on the characteristic relationship between the sound waves generated by the medium during flow and the liquid level within the vessel. It not only solves the problem of difficult liquid level measurement under harsh conditions such as high temperature, high pressure, strong acids, and strong alkalis in alumina production processes, significantly reducing the impact of the working environment on liquid level measurement, but also significantly reduces the cost of liquid level measurement. The method is simple to operate, convenient to use, and consumes no additional energy during operation, making liquid level measurement more efficient, reliable, energy-saving, and safe.

Description

Technical Field

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

[0002] With the rapid development of national industry, the requirements for the level and precision of automation control in industrial production operations have also increased rapidly. In industrial automation control systems, liquid level measurement is one of the most widely used key process indicators, essentially covering 100% of industrial container equipment. Therefore, convenient, safe, and effective liquid level measurement methods hold a very broad and important position in the field of industrial automation control.

[0003] Pressure vessels used in the alumina industry are sealed devices that contain strong acid or alkaline gases or liquids during the alumina production process and operate under high temperature and pressure. The liquid level in these pressure vessels is a crucial data parameter during operation, directly indicative of the overall system's operational status, equipment safety, and production stability. However, due to the harsh internal environment of these pressure vessels (high temperature, high pressure, strong acids, strong alkalis, etc.), the material requirements for the level measuring instrument are high when it comes into direct contact with the medium inside the vessel, and there is a risk of contamination or leakage of the measured medium. Therefore, non-invasive measurement methods are more suitable for measuring the liquid level in pressure vessels used in the alumina industry.

[0004] In the alumina industry, non-invasive liquid level measurement methods commonly used in 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 level measurement, ultrasonic level measurement, and nuclear radiation level measurement. Among these, radar and nuclear radiation level measurement methods offer high accuracy but are relatively expensive. Ultrasonic level measurement is more moderately costly, but it is prone to errors when measuring volatile or foam-producing media. Summary of the Invention

[0005] The purpose of this invention is to provide a method for measuring the liquid level in pressure vessels used in the alumina industry. This invention achieves real-time liquid level monitoring based on the characteristic relationship between the sound waves generated during the flow of the medium in the pressure vessel and the liquid level within the vessel.

[0006] The technical solution of the present invention is a liquid level measurement method for pressure vessels used in the alumina industry. The medium in the alumina pressure vessel generates sound waves during the flow process. The frequency of the sound waves is related to the liquid level of the medium in the vessel. A sound sensing element is set at the bottom of the pressure vessel to receive the sound waves. The method is converted according to the established formula of sound wave frequency-liquid level characteristic relationship. During production operation, non-invasive real-time monitoring of the liquid level of the medium in the vessel is realized.

[0007] In the aforementioned method for measuring the liquid level of a pressure vessel used in the alumina industry, a sensor transmits sound waves to the liquid level measurement data backend. The liquid level measurement data backend automatically processes the data through the relationship between the sound wave frequency and the liquid level height standard characteristic curve, and returns the data to the field and control center in digital form.

[0008] In the aforementioned method for measuring the liquid level in a pressure vessel used in the alumina industry, the relationship between the acoustic frequency and the liquid level height can be expressed by the formula... It means that among them It is related to the medium inside the container and the container wall thickness;

[0009] 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.

[0010] In the aforementioned method for measuring the liquid level of a pressure vessel used in the alumina industry, the correction coefficient K is related to the acoustic 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.

[0011] In the aforementioned method for measuring the liquid level of a pressure vessel used in the alumina industry, the sound-sensing element is disposed inside a soundproof enclosure.

[0012] The advantages of this invention compared to the prior art are as follows:

[0013] 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;

[0014] ②The principle is simple, the components used are common and universal, and the cost is low;

[0015] ③ No additional energy consumption from radar, sonar, electromagnetic fields, or radiation is required during liquid level measurement, resulting in low operating costs and high safety performance;

[0016] ④ By utilizing the relationship between the sound waves generated by the medium in the pressure vessel during the flow process and the liquid level of the medium in the vessel, real-time monitoring can be achieved with high accuracy.

[0017] In summary, this invention realizes a non-invasive liquid level measurement method based on the characteristic relationship between the sound waves generated by the medium in the pressure vessel during the flow process and the liquid level of the medium in the vessel. It not only solves the problem of difficult liquid level measurement in pressure vessels under harsh working conditions such as high temperature and high pressure, strong acid and strong alkali in the alumina production process, but also greatly reduces the impact of the working environment on liquid level measurement. It can also significantly reduce the cost of liquid level measurement, is simple to operate, convenient to use, and has no additional energy consumption during operation, making liquid level measurement of pressure vessels used in the alumina industry more efficient, reliable, energy-saving and safe. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the present invention.

[0019] Attached reference numerals: 1-Sound sensor, 2-Soundproof enclosure, 3-Sensor, 4-Liquid level measurement data backend, 5-Liquid level display screen. Detailed Implementation

[0020] 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.

[0021] Embodiments of the present invention: In order to overcome the shortcomings of existing liquid level measurement methods, the present invention provides a liquid level measurement method for pressure vessels used in the alumina industry. Based on the fact that the medium in the alumina pressure vessel generates sound waves during the flow process, and the frequency of the sound waves is related to the liquid level of the medium in the vessel, a sound sensing element 1 is set at the bottom of the pressure vessel to receive the sound waves. The liquid level is obtained by converting the sound wave frequency-liquid level height characteristic relationship formula. During production operation, non-invasive real-time monitoring of the liquid level of the medium in the vessel is realized.

[0022] Throughout the process, sensor 3 transmits sound waves to the liquid level measurement data backend 4. The liquid level measurement data backend 4 automatically processes the data using the standard characteristic curve relationship between sound wave frequency and liquid level height, and returns the data in digital form to the on-site liquid level display screen 5 for liquid level display and control center. This process enables automatic calculation of the liquid level.

[0023] The relationship between sound wave frequency and liquid level height can be expressed by the formula: It means that among them The formula above is related to the medium inside the container and the container wall thickness. In this formula, H represents the liquid level height to be measured; T represents the liquid temperature to be measured; K represents the correction coefficient, ranging from 0.01 to 2.5; X represents the sampling array (e.g., if there are *a* sampling results, all 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.

[0024] When the pressure inside the container, the bottom sediment, or the temperature of the medium changes, the density of the medium changes, which in turn causes changes in the acoustic impedance of the medium and attenuation of sound wave reflection, affecting the accuracy of the signal received by the final sound sensing element. At this time, the measurement error is reduced by the correction coefficient K. The correction coefficient K is related to the sound wave influencing factors: container 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.

[0025] 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.

[0026] The sound-sensing element 1 is located inside the soundproof enclosure 2 to avoid being affected by external environmental noise.

[0027] Taking the flash tank in the leaching workshop of the Bayer process alumina plant as an example, this flash tank has a double elliptical head, a diameter of 5m, a straight section height of 7m, a working pressure of 3.4MPa, and a working temperature of 270℃. The medium inside the tank is red mud slurry, and the liquid part is sodium aluminate solution (caustic soda concentration N). k =200~240g / L), the solid part is red mud, and the two are mixed evenly. The sodium aluminate solution in the flash evaporator flashes out alkaline vapors, therefore the container is in a state where gas, liquid, and solid coexist. Typically, nuclear radiation level gauges are used for measurement, but these are expensive, require a nuclear source due to radiation, and are complex to operate and require cumbersome approval procedures. 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. A method for measuring the liquid level in a pressure vessel used in the alumina industry, characterized in that: The medium in the alumina pressure vessel generates sound waves during the flow process. The frequency of the sound waves is related to the liquid level of the medium in the vessel. A sound sensor is installed at the bottom of the pressure vessel to receive the sound waves. The sound waves are converted according to the established formula of sound wave frequency-liquid level relationship. During production operation, non-invasive real-time monitoring of the liquid level of the medium in the vessel can be achieved. The sensor transmits the sound wave to the liquid level measurement data backend. The liquid level measurement data backend automatically processes the data through the standard characteristic curve relationship between sound wave frequency and liquid level height, and returns it to the field and control center in digital form. The relationship between sound wave frequency and liquid level height can be expressed by the formula. It means that among them It is related to the medium inside the container and the container wall thickness; 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 liquid level measurement method for a pressure vessel used in the alumina industry according to claim 1, characterized in that: The sound-sensing element is located inside the soundproof enclosure.

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