A method of measuring the level of a tank

Abstract

The present application relates to the technical field of tank liquid level measurement, and relates to a kind of tank liquid level measurement method.The present application carries out temperature correction to the standard relative dielectric constant of electromagnetic wave in each gas component by the reference temperature of tank collected, calculates the real-time propagation wave velocity of electromagnetic wave in combination with the volume proportion of each gas component, obtains the height above the liquid level from tank top according to real-time propagation wave velocity, and obtains the correction accumulation thickness of sediment in tank according to the disturbance data of recent crude oil disturbance operation, calculates the initial liquid level height of oil storage tank in combination with the design internal height of oil storage tank, calculates the internal oil capacity of oil storage tank according to initial liquid level height, carries out micro change correction to the oil capacity in tank in combination with the influence degree of reference temperature corresponding tank body micro change, and outputs the final oil storage capacity, so that the final oil storage capacity measurement result is more close to actual value, and the reliability of trade settlement and production scheduling is improved.

Description

Technical Field

[0001] This invention relates to the field of tank liquid level measurement technology, and specifically to a method for measuring tank liquid level. Background Technology

[0002] With the continuous improvement of the level of intelligence in the petrochemical industry, tank level measurement, as a core monitoring link in the crude oil storage and transportation process, directly affects the accuracy of inventory management and trade settlement. The internal environment of storage tanks is complex, and level measurement is affected by various dynamic factors. How to achieve accurate measurement under complex operating conditions is a current technical challenge.

[0003] In the prior art, Chinese Patent Publication No. CN120467470A discloses a liquid level monitoring method and system based on radar liquid level gauge. The present invention matches the current temperature of the material stored in the target tank with its dielectric constant to determine whether the dielectric constant is abnormal. At the same time, it performs multi-dimensional evaluation of key obstacles in the target tank and identifies foam or steam interference through multiple verifications, thereby reducing measurement errors.

[0004] Chinese Patent Publication No. CN118960903B discloses an automatic liquid level measurement method, device, and system for storage tanks. This invention obtains the echo signal of a guided wave radar level gauge, as well as the distance of the guided wave radar to the liquid surface and the distance of the guided wave radar to the bottom of the storage tank. It identifies the material accumulation signal segment and calculates the corresponding wave velocity attenuation weight and electromagnetic wave velocity to construct the velocity vector of the material accumulation zone, thereby correcting the liquid level measurement results and reducing the error caused by material accumulation.

[0005] Although the above-mentioned existing technologies have optimized the accuracy of liquid level measurement to a certain extent, the following problems still exist: (1) Existing technologies only focus on the single effect of temperature on the dielectric constant of the storage medium and correct the medium parameters through temperature matching, but do not consider the coupling effect of the mixed gas composition in the tank on the propagation speed of electromagnetic waves, resulting in the deviation of the propagation speed calculation of electromagnetic waves in the gas environment in the tank, causing the height measurement from the top of the tank to the liquid surface to be deviated, affecting the accuracy of subsequent liquid level and capacity analysis.

[0006] (2) Existing technologies focus on solving the problem of material accumulation in guided wave radar, but do not fully consider the impact of long-term accumulation of sediment at the bottom of the tank and dynamic changes in thickness caused by disturbances such as crude oil input on the liquid level reference surface. This results in errors in the calculation of the actual liquid level height from the bottom of the tank to the liquid surface, which cannot accurately reflect the effective oil storage space inside the tank, leading to systematic deviations in liquid level height measurement.

[0007] (3) Existing technology ignores the micro-deformation effect of the tank metal structure caused by temperature field changes and directly calculates the capacity by multiplying the liquid level height and the tank cross-sectional area. Temperature changes will cause slight deformation of the tank, resulting in a difference between the actual cross-sectional area and the designed cross-sectional area. Ultimately, this leads to a large deviation between the oil storage capacity measurement result and the actual value, affecting the accuracy of trade settlement and production scheduling. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides a method for measuring the liquid level in a storage tank. The technical solution adopted by the present invention to solve its technical problems is as follows: A method for measuring the liquid level in a storage tank, comprising: S1, collecting the temperature and gas composition content at different locations inside the storage tank through a sensor group deployed inside the storage tank, and determining the reference temperature and reference gas composition content inside the tank.

[0009] S2. Correct the standard relative permittivity of electromagnetic waves in each gas component based on the reference temperature, and calculate the actual propagation speed of electromagnetic waves inside the tank by combining the volume ratio of each gas component in the reference gas component content.

[0010] S3. The radar level gauge installed on the top of the tank emits electromagnetic waves at different angles to the liquid surface according to the actual propagation wave speed, collects the echo time of electromagnetic waves at different angles, and analyzes the height of the liquid level above the top of the tank and the liquid surface.

[0011] S4. Based on the real-time accumulation thickness distribution of sediment in the tank and the disturbance data of recent crude oil disturbance operations, output the corrected accumulation thickness of sediment in the tank. Combined with the design internal height of the oil storage tank, calculate the initial liquid level height of the oil storage tank.

[0012] S5. Calculate the oil capacity inside the storage tank based on the initial liquid level height, extract the historical liquid level difference data of the storage tank at different temperatures, determine the degree of influence of slight changes in the tank body corresponding to the reference temperature, correct the slight changes in the oil capacity inside the tank, and output the final oil storage capacity.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention corrects the standard relative permittivity of electromagnetic waves in each gas component by collecting the reference temperature inside the tank, and calculates the actual propagation speed of electromagnetic waves by combining the volume ratio of each gas component. This effectively eliminates the interference of temperature and gas component content coupling effect on electromagnetic wave speed, improves the accuracy of electromagnetic wave propagation speed, and lays the foundation for the accurate measurement of the height above the liquid level.

[0014] (2) The present invention collects the real-time accumulation thickness distribution of sediment in the tank by using an ultrasonic detection device, and combines the parameters of recent crude oil flow disturbance operation with the constructed relationship between sediment accumulation thickness and time change to output the corrected accumulation thickness of sediment in the tank. This dynamically corrects the error of liquid level reference surface caused by sediment accumulation and disturbance, making the initial liquid level height closer to the real liquid level height, and significantly reducing the systematic deviation of sediment factors on capacity calculation.

[0015] (3) The present invention calculates the internal oil capacity of the oil storage tank based on the initial liquid level height, extracts the historical liquid level difference data of the oil storage tank at different temperatures, determines the degree of influence of the slight change of the tank body corresponding to the reference temperature, corrects the slight change of the oil capacity in the tank, and outputs the final oil storage capacity. This effectively compensates for the influence of the tank body deformation caused by temperature change on the capacity calculation, so that the final oil storage capacity measurement result is closer to the actual value, and improves the reliability of trade settlement and production scheduling. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the method steps of the present invention.

[0018] Figure 2 This is a schematic diagram illustrating the steps for determining the reference temperature and reference gas composition content in this invention.

[0019] Figure 3 This is a schematic diagram illustrating the steps for obtaining the actual propagation wave velocity in this invention.

[0020] Figure 4 This is a schematic diagram of the modified packing thickness analysis steps in this invention. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. Furthermore, it should be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale.

[0022] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification.

[0023] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0024] Please see Figure 1 As shown, the present invention provides a method for measuring the liquid level in a storage tank, comprising: S1, collecting the temperature and gas composition content at different locations inside the storage tank through a sensor group deployed inside the storage tank, and determining the reference temperature and reference gas composition content inside the tank.

[0025] In one embodiment of the present invention, the sensor group includes an infrared thermal sensor and an electrochemical gas sensor, which respectively collect the temperature and gas composition content at different locations inside the oil storage tank. The different locations need to cover different height areas of the oil storage tank, for example, divided into 3 layers according to the total height of the tank. The common layering method is the bottom layer, the middle layer and the top layer of the tank, to ensure the comprehensiveness and redundancy of data collection.

[0026] Considering the differences in temperature and gas composition at different heights within the oil storage tank—for example, light gases tend to accumulate at the top of the tank, and the temperature is more affected by the environment; while the bottom of the tank has a more stable temperature and the gas composition is mainly heavy components—if data from all locations were directly mixed for calculation, regional differences would be masked, leading to distorted reference values. Therefore, it is necessary to first classify the data by collection height.

[0027] Based on this, such as Figure 2 As shown, the reference temperature and reference gas composition content inside the tank are determined as follows: S11, the temperature and gas composition content at different locations inside the oil storage tank collected by the sensor group are classified into layers according to the collection height to obtain the temperature subset and gas composition content subset corresponding to each height layer.

[0028] S12. Perform outlier detection on the corresponding feature values ​​within each subset, remove abnormal feature values ​​that exceed the distribution feature range, and retain the effective temperature and effective gas component content.

[0029] Since the sensor may exhibit abnormal readings due to vibrations inside the tank or interference from oil and gas, outlier detection is required for the corresponding feature values ​​within each subset to ensure data validity. This embodiment preferably employs the 3σ principle, that is, first calculating the mean of the corresponding feature values ​​within each subset. with characteristic standard deviation Remove excess For abnormal characteristic values ​​within a range, all remaining characteristic values ​​within the temperature subset are recorded as effective temperatures, and all remaining characteristic values ​​within the gas composition content subset are recorded as effective gas composition contents.

[0030] S13. Take the average of all effective temperatures and effective gas component contents in each altitude layer as the corresponding inter-layer temperature and inter-layer gas component contents.

[0031] S14. Based on the temperature correlation weight and gas composition content weight corresponding to each height layer in the oil storage tank, the interlayer temperature and interlayer gas composition content of each height layer are weighted and summed to obtain the reference temperature and reference gas composition content.

[0032] It should be noted that, due to the different influences of different height layers inside the tank on electromagnetic wave propagation, for example, the middle layer of the tank is the main area for electromagnetic wave propagation and has the highest influence weight, it is necessary to set corresponding correlation weights for each height layer. In this embodiment, the weights of temperature and gas composition content in the middle layer of the tank are both set to 0.5, and the weights of the bottom layer and the top layer of the tank are both set to 0.25.

[0033] In another embodiment, the implementer can adjust the associated weights corresponding to each height layer.

[0034] S2. Correct the standard relative permittivity of electromagnetic waves in each gas component based on the reference temperature, and calculate the actual propagation speed of electromagnetic waves inside the tank by combining the volume ratio of each gas component in the reference gas component content.

[0035] In one embodiment of the present invention, such as Figure 3 As shown, the actual propagation wave speed is obtained as follows: S21, based on the reference gas composition content, extract the standard relative permittivity of radar electromagnetic waves under standard conditions in each gas composition from the gas physical property database.

[0036] It should be noted that the gas physical properties database stores the standard relative permittivity of radar electromagnetic waves of common gas components in oil storage tanks under standard conditions. These common gas components include, but are not limited to, methane, ethane, propane, carbon dioxide, nitrogen, and hydrogen sulfide.

[0037] The standard state is defined as a space environment with a temperature of 25℃ and an atmospheric pressure of 101.325kPa, according to existing requirements.

[0038] S22. Compare the standard thermodynamic temperature corresponding to the standard state with the reference temperature, and calculate the ratio with the standard relative permittivity of each gas component to determine the corrected relative permittivity of each gas component at the reference temperature.

[0039] It should be noted that the formula for calculating the corrected relative permittivity is as follows: .

[0040] in, This represents the corrected relative permittivity of the gas composition at a reference temperature. The standard relative permittivity of this gas component is... The standard thermodynamic temperature corresponds to the standard state. The thermodynamic temperature is obtained by converting the reference temperature.

[0041] In the above corrected calculation formula, This represents the difference between the relative permittivity of the gas component at the reference temperature and 1. It reflects the relative permittivity of the gas component under the current tank temperature conditions and the degree of difference between the permittivity and the standard conditions. The larger the difference, the more significant the impact of the deviation between the actual temperature inside the tank and the standard temperature on the gas's dielectric properties.

[0042] The corrected relative permittivity is obtained by summing the above difference with 1. The corrected relative permittivity is the core basis for subsequent calculations of the equivalent relative permittivity of the mixed gas in the tank and the actual propagation speed of electromagnetic waves. It effectively eliminates the interference of temperature factors on dielectric properties and improves the accuracy of subsequent liquid level measurement.

[0043] S23. Based on the content of reference gas components, obtain the volume percentage of each gas component, and combine the corrected relative permittivity of each gas component at the reference temperature to analyze the equivalent relative permittivity of the electromagnetic wave.

[0044] The equivalent relative permittivity corresponding to the electromagnetic wave is obtained by linearly summing the corrected relative permittivity of each gas component at the reference temperature through volume weighting.

[0045] S24. Substitute the equivalent relative permittivity corresponding to the electromagnetic wave into the standard formula for electromagnetic wave speed to output the actual propagation speed of the electromagnetic wave inside the tank.

[0046] It should be noted that the standard formula for calculating the electromagnetic wave speed is as follows: .

[0047] in, The actual propagation speed of electromagnetic waves. The standard propagation speed of electromagnetic waves in a vacuum. Let be the equivalent relative permittivity corresponding to the electromagnetic wave. The above standard formula for the electromagnetic wave speed is an existing technical formula and will not be repeated here.

[0048] This invention uses the collected reference temperature inside the tank to correct the standard relative permittivity of electromagnetic waves for each gas component, and calculates the actual propagation speed of the electromagnetic waves by combining the volume percentage of each gas component. This effectively eliminates the interference of the coupling effect of temperature and gas component content on the electromagnetic wave speed, improves the accuracy of electromagnetic wave propagation speed, and lays the foundation for the accurate measurement of the height above the liquid level.

[0049] S3. The radar level gauge installed on the top of the tank emits electromagnetic waves at different angles to the liquid surface according to the actual propagation wave speed, collects the echo time of electromagnetic waves at different angles, and analyzes the height of the liquid level above the top of the tank and the liquid surface.

[0050] The steps for analyzing the height above the liquid level from the top of the tank to the liquid surface are as follows: First, based on the echo time of electromagnetic waves at different angles, and combined with the correlation between the propagation distance of electromagnetic waves and the actual propagation speed and echo time, the propagation distance of electromagnetic waves at each angle is calculated.

[0051] In one embodiment of the present invention, the relationship between electromagnetic wave propagation distance and actual propagation speed and echo time is already existing technology. Specifically, the electromagnetic wave propagation distance is the product of actual propagation speed and echo time divided by 2. The division by 2 is because the electromagnetic wave is reflected back to the radar level gauge after being emitted from the top of the tank to the liquid surface. The echo time corresponds to the round-trip path from the top of the tank to the liquid surface and back to the top of the tank. The propagation distance is the one-way path length.

[0052] Secondly, the propagation distance of electromagnetic waves at each angle is corrected to obtain the straight-line propagation distance of electromagnetic waves at each angle, and the average value is taken as the height above the liquid level from the top of the tank to the liquid surface.

[0053] In one embodiment of the present invention, the propagation distance of the electromagnetic wave at each angle is corrected by multiplying the propagation distance of the electromagnetic wave at each angle by the cosine value of the corresponding angle to obtain the linear propagation distance of the electromagnetic wave at each angle.

[0054] S4. Based on the real-time accumulation thickness distribution of sediment in the tank and the disturbance data of recent crude oil disturbance operations, output the corrected accumulation thickness of sediment in the tank. Combined with the design internal height of the oil storage tank, calculate the initial liquid level height of the oil storage tank.

[0055] Considering the uneven accumulation of sediment at the bottom of the tank, such as thicker sediment near the inlet and thinner sediment further away from the inlet, and the recent disturbances such as crude oil inputs that wash away the sediment at the bottom of the tank, causing dynamic changes in its accumulation thickness, relying solely on a single detection point or static data cannot accurately reflect the true accumulation state of the sediment.

[0056] Based on this, such as Figure 4As shown, the method for correcting the accumulation thickness of sediment in the output tank is as follows: First, the initial accumulation thickness of sediment in different areas of the bottom of the oil storage tank is collected in real time by an ultrasonic detection device to form a set of real-time accumulation thickness distribution of sediment in the tank.

[0057] In one embodiment of the present invention, an ultrasonic detection device is deployed at the bottom of the oil storage tank in a grid-like uniform layout. Specifically, the center of the tank bottom is used as the origin, and the area is divided into several uniform regions according to a predetermined area, ensuring coverage of the entire tank bottom area. This avoids undetected localized sediment buildup and accurately captures differences in sediment thickness across different regions.

[0058] The method of detecting the initial accumulation thickness of sediments using an ultrasonic detection device, as described above, is existing technology and will not be elaborated further.

[0059] The second step involves extracting the initial liquid level, input oil volume, and interval duration during recent crude oil flow disturbance operations from the tank operation database. Based on the constructed formula for the time variation of sediment accumulation thickness, correction values ​​for sediment accumulation thickness in different regions are matched.

[0060] Specifically, the most recent crude oil flow disturbance operation is the crude oil input operation most recent to the present time, and its interval is the time interval between the most recent crude oil flow disturbance operation and the present time. Since the most recent crude oil input operation has the most significant impact on the sediment, the subsequent re-deposition process is not disturbed by other disturbance operations, and can accurately reflect the current sediment accumulation thickness.

[0061] Considering that recent crude oil flow disturbances will have a scouring effect on the sediment at the bottom of the tank, the lower the initial liquid level, the greater the impact force when crude oil is input, and the more significant the scouring effect on the sediment; the larger the input oil volume, the higher the duration and intensity of scouring, and the more obvious the migration and redeposition of sediment; while the interval directly affects the redeposition time of sediment after scouring, the longer the interval, the more complete the redeposition of sediment, and the more significant the change in the accumulation thickness.

[0062] Based on this, the formula for the time variation of sediment accumulation thickness is constructed as follows: First, the input oil volume and initial liquid level in each crude oil flow disturbance operation are retrieved from the tank operation database, and the crude oil flow disturbance operations corresponding to each input oil volume in each initial liquid level range are statistically analyzed.

[0063] It should be noted that each initial liquid level range can be divided into equal parts according to the designed internal height of the oil storage tank. In one embodiment of the present invention, the set height is 1m, but the implementer can also set its own height.

[0064] Secondly, based on the initial thickness of sediment in different areas of the tank before each crude oil flow disturbance operation, the time sequence of sediment accumulation thickness changes in different areas of the tank after each crude oil flow disturbance operation is extracted, and the mode of sediment accumulation thickness in different areas of the tank at each time period is obtained.

[0065] It should be noted that the time series of changes in the accumulation thickness of sediment in different regions is represented by the accumulation thickness corresponding to each time period after the crude oil flow disturbance operation. If the accumulation thickness corresponding to a certain time period is the same as the initial thickness of sediment in the corresponding region in the tank before the crude oil flow disturbance operation, then that time period is taken as the cutoff time period, and the accumulation thickness between the corresponding time period after the crude oil flow disturbance operation and the cutoff time period constitutes the time series of changes in accumulation thickness.

[0066] Finally, linear fitting was performed on the mode of the sediment accumulation thickness at each time period to construct the relationship between the sediment accumulation thickness and time, and the relationship between the sediment accumulation thickness and time of each input oil volume in different regions within each initial liquid level range was statistically analyzed.

[0067] In one specific embodiment, the relationship between the sediment accumulation thickness and time is a linear equation in one variable, where time is the independent variable and the sediment accumulation thickness is the dependent variable.

[0068] The third step is to correct the real-time accumulation thickness distribution set based on the accumulation thickness correction values ​​of sediments in different regions, and obtain the corrected accumulation thickness distribution set.

[0069] The fourth step is to determine the uniformity of the thickness of the corrected stacking thickness distribution set. If the thickness is uniform, the average thickness in the corrected stacking thickness distribution set is used as the corrected stacking thickness. If the thickness is not uniform, the maximum and minimum thicknesses in the corrected stacking thickness distribution set are selected, and their average is used as the corrected stacking thickness.

[0070] It should be noted that the basis for determining the uniformity of thickness is as follows: when the thickness difference between all stacked thicknesses in the corrected stacked thickness distribution set is less than the set allowable thickness difference, the stacked thickness distribution set is determined to be uniform in thickness.

[0071] The process of calculating the initial liquid level height of the oil storage tank is as follows: obtain the design internal height of the oil storage tank from the design parameters of the oil storage tank, compare the difference between the design internal height and the height above the liquid level from the top of the tank to the liquid surface to obtain the theoretical liquid level height from the bottom of the tank to the liquid surface, and use the difference between this and the corrected accumulation thickness of the sediment in the tank as the initial liquid level height of the oil storage tank.

[0072] This invention uses an ultrasonic detection device to collect the real-time distribution of sediment thickness in the tank, combines the parameters of recent crude oil flow disturbance operations with the constructed relationship between sediment thickness and time, and outputs the corrected sediment thickness in the tank. This dynamically corrects the error in the liquid level reference surface caused by sediment accumulation and disturbance, making the initial liquid level height closer to the true liquid level height, and significantly reducing the systematic deviation of the sediment factor on the capacity calculation.

[0073] S5. Calculate the oil capacity inside the storage tank based on the initial liquid level height, extract the historical liquid level difference data of the storage tank at different temperatures, determine the degree of influence of slight changes in the tank body corresponding to the reference temperature, correct the slight changes in the oil capacity inside the tank, and output the final oil storage capacity.

[0074] Specifically, the calculation method for the internal oil capacity of the oil storage tank is as follows: obtain the design internal cross-sectional area of ​​the oil storage tank from the design parameters of the oil storage tank, multiply the initial liquid level height of the oil storage tank by the design internal cross-sectional area, and use the product result as the internal oil capacity of the oil storage tank.

[0075] Preferably, in one embodiment of the present invention, the oil storage tank is cylindrical. Furthermore, the deformation of a cylindrical tank under temperature changes is relatively regular, facilitating the establishment of a micro-variation impact model through historical data analysis. Therefore, it is suitable for industrial oil storage scenarios requiring high metering accuracy.

[0076] In other embodiments, the oil storage tank may also be square, ellipsoidal, or other types. The present invention does not limit the specific type of oil storage tank.

[0077] Considering that the material of the oil storage tank has the characteristics of thermal expansion and contraction, the temperature change inside the tank will cause slight deformation of the tank body, which will affect the actual internal cross-sectional area of ​​the tank body, resulting in a deviation between the basic capacity calculated based on the design cross-sectional area and the actual capacity; while historical liquid level measurement records contain data such as liquid level and capacity at different temperatures, which can reflect the correlation between temperature and tank deformation.

[0078] Furthermore, considering the continuous functional relationship between temperature and slight changes in the tank, a correlation equation is established using discrete temperature and slight change influence samples and a data fitting method. This enables the prediction of the influence of slight changes at any temperature. Compared to relying solely on discrete sample points, the correlation equation has stronger versatility and interpolation capabilities, and can cover reference temperatures not included in historical data.

[0079] Based on this, the method for determining the degree of influence of slight changes in the tank corresponding to the reference temperature is as follows: First, extract the tank temperature, initial liquid level height and real-time oil storage capacity from the historical liquid level measurement records of each oil storage tank, and combine the real-time oil storage capacity with the designed internal cross-sectional area to obtain the theoretical liquid level height of the real-time oil storage capacity.

[0080] The second step is to analyze the deviation between the initial liquid level height and the theoretical liquid level height in each historical liquid level measurement record to obtain the liquid level height deviation rate, which is used as the degree of influence of slight changes in the tank.

[0081] The liquid level height deviation rate is the difference between the initial liquid level height and the theoretical liquid level height, and the ratio of this difference to the theoretical liquid level height is used as the liquid level height deviation rate.

[0082] The third step is to statistically analyze the impact of slight changes in the tank body on the temperature inside each tank in each historical liquid level measurement record, and calculate the impact of slight changes in the tank body on the temperature inside each tank by means of the average value.

[0083] The fourth step involves using temperature as the independent variable and the degree of influence of slight changes in the tank body as the dependent variable, and then using the least squares method to fit the correlation equation between temperature and the degree of influence of slight changes in the tank body.

[0084] The fifth step is to input the reference temperature inside the tank into the fitted correlation equation and output the corresponding degree of influence of the slight change in the tank.

[0085] Preferably, in one embodiment of the present invention, by analyzing data from historical liquid level measurement records, a linear correlation was found between temperature and the degree of influence of slight changes in the tank. A least squares method was used for linear fitting to obtain the correlation equation between temperature and the degree of influence of slight changes in the tank. The general form of the linearly fitted correlation equation is: .

[0086] in To determine the degree of impact of minor changes in the tank body, To fit the slope, reflecting the change in the degree of influence of a small change in the tank body for every 1°C change in temperature, For temperature, The intercept is a benchmark value reflecting the degree of influence of slight changes in the tank body at a temperature of 0℃.

[0087] In other embodiments, if historical data shows a non-linear relationship between temperature and the degree of influence of slight changes in the tank body—that is, different temperatures correspond to different degrees of influence of slight changes in the tank body, such as higher temperatures resulting in greater influence—a non-linear correlation equation needs to be fitted using a cubic function. The general form of the cubic function correlation equation is: In the formula The coefficients are those of a cubic polynomial, and This determines the number of inflection points and the trend of change in the curve.

[0088] The specific details of outputting the final oil storage capacity are as follows: calculate the oil capacity correction value by multiplying the oil capacity inside the storage tank by the degree of influence of the slight change in the tank body corresponding to the reference temperature, and then summing the correction value with the oil capacity inside the storage tank to output the final oil storage capacity.

[0089] This invention calculates the internal oil capacity of an oil storage tank based on the initial liquid level height, extracts historical liquid level difference data of the oil storage tank at different temperatures, determines the degree of influence of slight changes in the tank body corresponding to the reference temperature, corrects the slight changes in the internal oil capacity, and outputs the final oil storage capacity. This effectively compensates for the influence of tank body deformation caused by temperature changes on the capacity calculation, making the final oil storage capacity measurement result closer to the actual value and improving the reliability of trade settlement and production scheduling.

[0090] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0091] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0092] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0093] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0094] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring liquid level in a storage tank, characterized in that, include: By collecting the temperature and gas composition content at different locations inside the oil storage tank using a sensor array deployed inside the tank, a reference temperature and reference gas composition content inside the tank can be determined. The standard relative permittivity of electromagnetic waves in each gas component is corrected based on the reference temperature, and the actual propagation speed of electromagnetic waves inside the tank is calculated by combining the volume percentage of each gas component in the reference gas component content. The radar level gauge installed on the top of the tank emits electromagnetic waves at different angles to the liquid surface according to the actual propagation wave speed, collects the echo time of electromagnetic waves at different angles, and analyzes the height of the liquid level above the top of the tank and the liquid surface. Based on the real-time accumulation thickness distribution of sediment in the tank and the disturbance data of recent crude oil disturbance operations, the corrected accumulation thickness of sediment in the tank is output. Combined with the design internal height of the oil storage tank, the initial liquid level height of the oil storage tank is calculated. The method for correcting the buildup thickness of the sediment in the output tank is as follows: The initial accumulation thickness of sediment in different areas of the bottom of the oil storage tank is collected in real time by an ultrasonic detection device, forming a set of real-time accumulation thickness distribution of sediment in the tank. The initial liquid level, input oil volume and interval of recent crude oil flow disturbance operations are extracted from the tank operation database. Based on the constructed relationship between the time variation of sediment accumulation thickness, the correction value of sediment accumulation thickness in different regions is matched. Based on the correction values ​​of sediment accumulation thickness in different regions, the real-time accumulation thickness distribution set is corrected to obtain the corrected accumulation thickness distribution set. The thickness uniformity of the corrected stacking thickness distribution set is determined. If the thickness is uniform, the average thickness in the corrected stacking thickness distribution set is used as the corrected stacking thickness. If the thickness is not uniform, the maximum and minimum thicknesses in the corrected stacking thickness distribution set are selected, and their average is used as the corrected stacking thickness. The oil capacity inside the storage tank is calculated based on the initial liquid level. Historical liquid level difference data of the storage tank at different temperatures is extracted. The degree of influence of slight changes in the tank body corresponding to the reference temperature is determined. The slight changes in the oil capacity inside the tank are then corrected, and the final oil capacity is output.

2. The method for measuring liquid level in a storage tank according to claim 1, characterized in that: The reference temperature and reference gas composition content inside the tank are determined as follows: The temperature and gas composition content at different locations inside the oil storage tank collected by the sensor group are stratified and classified according to the collection height to obtain the temperature subset and gas composition content subset corresponding to each height layer; Outlier detection is performed on the corresponding feature values ​​within each subset to remove abnormal feature values ​​that exceed the distribution feature range, while retaining the effective temperature and effective gas component content; The average of all effective temperatures and effective gas composition contents in each altitude layer is taken as the corresponding inter-layer temperature and inter-layer gas composition contents; Based on the temperature correlation weight and gas composition content weight corresponding to each height layer in the oil storage tank, the interlayer temperature and interlayer gas composition content of each height layer are weighted and summed to obtain the reference temperature and reference gas composition content.

3. The method for measuring liquid level in a storage tank according to claim 1, characterized in that: The actual propagation wave speed was obtained as follows: Based on the reference gas composition content, the standard relative permittivity of radar electromagnetic waves under standard conditions in each gas composition is extracted from the gas physical property database. The standard thermodynamic temperature corresponding to the standard state is compared with the reference temperature, and the ratio is fused with the standard relative permittivity of each gas component to calculate the corrected relative permittivity of each gas component at the reference temperature. The volume percentage of each gas component is obtained based on the content of the reference gas component, and the equivalent relative permittivity of the electromagnetic wave is analyzed by combining the corrected relative permittivity of each gas component at the reference temperature. Substituting the equivalent relative permittivity of the electromagnetic wave into the standard formula for electromagnetic wave speed, the actual propagation speed of the electromagnetic wave inside the tank is output.

4. The method for measuring liquid level in a storage tank according to claim 3, characterized in that: The steps for determining the height of the liquid level above the top of the analysis tank are as follows: Based on the echo time of electromagnetic waves at different angles, and combined with the correlation between electromagnetic wave propagation distance and actual propagation speed and echo time, the propagation distance of electromagnetic waves at each angle is calculated. The propagation distance of electromagnetic waves at each angle is corrected by angle to obtain the straight-line propagation distance of electromagnetic waves at each angle, and the average value is taken as the height above the liquid level from the top of the tank to the liquid surface.

5. The method for measuring liquid level in a storage tank according to claim 1, characterized in that: The formula for the time-varying relationship of the sediment accumulation thickness is constructed as follows: Retrieve the input oil volume and initial liquid level from each crude oil flow disturbance operation from the tank operation database, and statistically analyze each crude oil flow disturbance operation corresponding to each input oil volume within each initial liquid level range. Based on the initial thickness of sediment in different areas of the tank before each crude oil flow disturbance operation, the time sequence of sediment accumulation thickness changes in different areas of the tank after each crude oil flow disturbance operation is extracted, and the mode of sediment accumulation thickness in different areas of the tank at each time period is obtained. Linear fitting was performed on the mode of the sediment accumulation thickness at each time period to construct the relationship between the sediment accumulation thickness and time. The relationship between the sediment accumulation thickness and time variation of each input oil volume in different regions within each initial liquid level range was statistically analyzed.

6. The method for measuring liquid level in a storage tank according to claim 1, characterized in that: The process of calculating the initial liquid level height of the oil storage tank is as follows: The design internal height of the oil storage tank is obtained from the design parameters of the oil storage tank. The difference between the design internal height and the height above the liquid level from the top of the tank to the liquid surface is compared to obtain the theoretical liquid level height from the bottom of the tank to the liquid surface. The difference between this theoretical internal height and the corrected accumulation thickness of the sediment in the tank is used as the initial liquid level height of the oil storage tank.

7. The method for measuring liquid level in a storage tank according to claim 1, characterized in that: The method for calculating the internal oil capacity of the oil storage tank is as follows: Obtain the design internal cross-sectional area of ​​the oil storage tank from the design parameters, multiply the initial liquid level height of the oil storage tank by the design internal cross-sectional area, and use the product as the internal oil capacity of the oil storage tank.

8. The method for measuring liquid level in a storage tank according to claim 7, characterized in that: The method for determining the degree of influence of slight changes in the tank corresponding to the reference temperature is as follows: Extract the tank temperature, initial liquid level and real-time oil capacity from the historical liquid level measurement records of the oil storage tank, and combine the real-time oil capacity with the designed internal cross-sectional area to obtain the theoretical liquid level height of the real-time oil storage capacity. The initial liquid level height and the theoretical liquid level height in each historical liquid level measurement record are analyzed to obtain the liquid level height deviation rate, which is used as the degree of influence of slight changes in the tank. The influence of slight changes in the tank body on the temperature inside each tank is statistically analyzed according to the historical liquid level measurement records. The influence of slight changes in the tank body on the temperature inside each tank is calculated by averaging the values. With temperature as the independent variable and the degree of influence of slight changes in the tank body as the dependent variable, the correlation equation between temperature and the degree of influence of slight changes in the tank body was obtained by fitting using the least squares method. Input the reference temperature inside the tank into the fitted correlation equation, and output the corresponding degree of influence of slight changes in the tank.

9. A method for measuring liquid level in a storage tank according to claim 8, characterized in that: The final output oil storage capacity is as follows: The oil capacity is calculated by multiplying the oil capacity inside the storage tank by the degree of influence of the slight change in the tank body corresponding to the reference temperature, and the oil capacity slight change correction value is obtained. This value is then added to the oil capacity inside the storage tank to calculate the final oil capacity.

Images