A calculation method for solving the storage tank inventory error caused by LNG liquid with different densities

Abstract

This invention belongs to the technical field of gas station operational inventory calculation, and specifically relates to a calculation method for addressing the inventory discrepancies caused by LNG liquids of different densities. This invention calculates the converted liquid level height H2 based on the vaporization rate K2 of the LNG liquid source purchased by the gas station. n The change in gas source density corresponds to the actual LNG mass M2 n Calculate the difference M4 between the inventory readings and the actual inventory readings. n This invention is applied to the acquisition of differential pressure signals in fixed storage tanks at LNG refueling stations. It can automatically detect and calculate corrections for deviations in tank inventory levels caused by changes in the gas source, based on table lookup calculations. It displays the current liquid level corresponding to the table quality and the corrected inventory quality, and calculates the difference between the two. This facilitates data statistics and management at the refueling station, reducing the impact of errors on the key loss amount in quantity and quality management during operation.

Description

Technical Field

[0001] This invention belongs to the technical field of gas station operation inventory calculation, and specifically relates to a calculation method for solving the error in tank inventory caused by LNG liquid of different densities. Background Technology

[0002] Currently, the on-site inventory is measured using the liquid level reference table calibrated at the factory for the storage tanks. On-site mechanical differential pressure level gauges and differential pressure transmitters transmit the collected liquid level signals to the KingSCADA software to calculate and display the current inventory level and inventory quality.

[0003] Because LNG comes from different gas sources, with varying alkane content such as shale gas and imported gas, the density of LNG varies. Therefore, comparing the LNG with the factory-calibrated liquid level in the table results in significant measurement errors, affecting the calculation of gas station operating inventory and losses. This large error is a common problem that urgently needs to be solved in the operation and management of LNG gas stations.

[0004] The KingSCADA system's lookup table showed a large error, requiring rewiring of the control cabinet, which involved a significant workload, affected the integrity of the original cabinet, and resulted in high upgrade and maintenance costs. The system software lacked algorithmic correction, and inventory deviations caused by density issues impacted the normal operation and quantity / quality management of the gas station. Summary of the Invention

[0005] In order to solve the above-mentioned problems in the existing technology, the purpose of this invention is to provide a calculation method for solving the storage tank inventory error caused by LNG liquid of different densities by correcting the operating inventory of gas filling stations.

[0006] The technical solution adopted in this invention is as follows:

[0007] A calculation method for resolving inventory discrepancies in LNG storage tanks caused by LNG of varying densities includes the following steps:

[0008] S1: Calculate the subdivided liquid level height H1 by subdividing the liquid level height H1 and the corresponding container volume, LNG volume, and LNG mass from the liquid level reference table provided by the storage tank manufacturer. n Volume V1 of the liquid source container in the storage tank n LNG volume V2 corresponding to the liquid source in the storage tank n LNG mass M1 corresponding to the liquid source in the storage tank n ;

[0009] S2: Calculate the LNG density corresponding to the subdivided tank liquid source: ρ1 n =M1 n / V1 n *1000;

[0010] Calculate the liquid-gas conversion expansion rate of the subdivided storage tank liquid source: K1 n =V2n / V1 n ;

[0011] S3: Calculate the LNG density corresponding to the purchased LNG source based on the vaporization rate K2 of the purchased LNG source: ρ2 n =(1000 / K2)*(K1) n / 1000);

[0012] S4: Calculate the converted liquid level height: H2 n =(ρ1) n *H1 n ) / ρ2 n ;

[0013] Calculate the liquid level height corresponding to the current value and the corresponding level gauge reading: H3 n =EVALUATE(H2) n );

[0014] S5: Calculate the corresponding volume of LNG in the storage tank:

[0015] V3 n =V1 n +((V1 b -V1 a ) / (H1 b -H1 a ))*(H2 n -H1 n );

[0016] Calculate the actual LNG mass corresponding to the change in gas source density:

[0017] M2 n =M1 n +((M1 b -M1 a ) / (H1 b -H1 a ))*(H2 n -H1 n );

[0018] S6: Calculate the mass corresponding to the current level gauge reading:

[0019] M3 n =LOOKUP(H3) n H1 n H1 a M1 n M1 a );

[0020] Calculate the difference in inventory readings: M4 n =M2 n -M3n ;

[0021] Where n is the sequence number.

[0022] This invention uses the liquid level reference table from the storage tank manufacturer to subdivide the liquid source container volume V1 of the storage tank. n LNG volume V2 corresponding to the liquid source in the storage tank n LNG mass M1 corresponding to the liquid source in the storage tank n Furthermore, the LNG density ρ1 corresponding to the liquid source in the storage tank is calculated in detail. n The expansion rate K1 of liquid source and gas conversion in the storage tank n Based on the vaporization rate K2 of the LNG liquid purchased by the gas station, the converted liquid level height H2 is calculated sequentially. n The change in gas source density corresponds to the actual LNG mass M2 n Calculate the difference M4 between the inventory readings and the actual inventory readings. n .

[0023] This invention is applied to the acquisition of differential pressure signals in fixed storage tanks of LNG refueling stations. It can automatically detect and calculate the deviation in tank inventory caused by changes in gas source when converting inventory levels from tables. It displays the current liquid level corresponding to the table quality and the corrected inventory quality, and calculates the difference between the two. This facilitates data statistics and management for refueling stations and reduces the impact of errors on the key loss amount in data quality management during operation.

[0024] In a preferred embodiment of the present invention, in step S1, the container volume, LNG volume, and LNG mass in the liquid level reference table provided by the storage tank manufacturer are subdivided into equal parts per 1mm of liquid level height. The present invention performs subdivision calculations based on the original liquid level reference table, facilitating the calculation of the actual LNG mass M2 corresponding to changes in gas source density. n Calculate the difference M4 between the inventory readings and the actual inventory readings. n This improves calculation accuracy.

[0025] As a preferred embodiment of the present invention, in step S1, during the detailed calculation, the volume of the liquid source container in the storage tank is:

[0026] V1 n =V1 n-1 +(V1 b -V1 a ) / (H1 b -H1 a );

[0027] Where a and b are two adjacent liquid level height values ​​in the liquid level reference table when the storage tank leaves the factory, and b > a.

[0028] As a preferred embodiment of the present invention, in step S1, during detailed calculation, the LNG volume corresponding to the liquid source in the storage tank is:

[0029] V2 n =V2 n-1 +(V2 b -V2 a ) / (H1 b -H1 a );

[0030] Where a and b are two adjacent liquid level height values ​​in the liquid level reference table when the storage tank leaves the factory, and b > a.

[0031] As a preferred embodiment of the present invention, in step S1, during the detailed calculation, the mass of LNG corresponding to the liquid source in the storage tank is:

[0032] M1 n =M1 n-1 +(M1 b -M1 a ) / (H1 b -H1 a );

[0033] Where a and b are two adjacent liquid level height values ​​in the liquid level reference table when the storage tank leaves the factory, and b > a.

[0034] As a preferred embodiment of the present invention, in step S4, the converted liquid level height H2 is calculated. n At that time, the subdivided liquid level height H1n is obtained by reading the liquid level in the storage tank.

[0035] As a preferred embodiment of the present invention, in step S3, the LNG density ρ2 corresponding to the purchased liquid source is calculated. n At that time, the user inputs the vaporization rate K2 of the purchased liquid source based on the gas quality report of the purchased liquid source.

[0036] The beneficial effects of this invention are as follows:

[0037] This invention is applied to the acquisition of differential pressure signals in fixed storage tanks of LNG refueling stations. It can automatically detect and calculate the deviation in tank inventory caused by changes in gas source when converting inventory levels from tables. It displays the current liquid level corresponding to the table quality and the corrected inventory quality, and calculates the difference between the two. This facilitates data statistics and management for refueling stations and reduces the impact of errors on the key loss amount in data quality management during operation. Attached Figure Description

[0038] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the invention can be combined with each other.

[0041] The parameters required for this calculation method are as follows:

[0042] Subdivided liquid level height (mm): H1 n ;

[0043] Storage tank liquid source container volume (m 3 ): V1 n ;

[0044] LNG volume corresponding to the liquid source in the storage tank (m³) 3 ):V2 n ;

[0045] Calculate the liquid-gas conversion expansion rate (m) of the subdivided storage tank liquid source. 3 / Nm 3 ): K1 n (where K1) n Indicates 1m 3 The volume (Nm³) of gaseous natural gas (NG) when LNG is completely vaporized into one standard atmosphere (1 atm = 760 mmHg = 101325 Pa). 3 ));

[0046] LNG mass (kg) corresponding to the liquid source in the storage tank: M1 n ;

[0047] LNG density (kg / L) corresponding to the liquid source in the storage tank: ρ1 n ;

[0048] LNG vaporization rate (Nm³) for gas stations 3 / T): K2 (User inputs value based on the gas quality report of the purchased liquid source; where K2 represents the volume (Nm³) of 1T of LNG liquid completely vaporized into gaseous natural gas NG at one standard atmosphere (1atm=760mmHg=101325Pa). 3 ));

[0049] The density (kg / L) of the LNG source to be procured is: ρ2 n ;

[0050] Conversion of liquid level height (mm): H2 n ;

[0051] Convert the volume of LNG in the storage tank (m³) 3 ): V3 n ;

[0052] Gas source density change corresponds to actual LNG mass (kg): M2 n ;

[0053] The current value corresponds to the liquid level height (mm) of the level gauge reading: H3 n ;

[0054] The current value corresponds to the mass (kg) of the liquid level gauge reading: M3 n ;

[0055] Inventory reading difference (kg): M4 n .

[0056] M4 n When M4 is negative, it indicates that the data read from the table is more than the actual inventory; conversely, M4... n When the value is positive, it indicates that the data retrieved from the table is less than the actual inventory.

[0057] like Figure 1 As shown in the figure, the calculation method for solving the storage tank inventory error caused by LNG liquids of different densities in this embodiment includes the following steps:

[0058] S1: Calculate the subdivided liquid level height H1 by subdividing the liquid level height H1 and the corresponding container volume, LNG volume, and LNG mass from the liquid level reference table provided by the storage tank manufacturer. n Volume V1 of the liquid source container in the storage tank n LNG volume V2 corresponding to the liquid source in the storage tank n LNG mass M1 corresponding to the liquid source in the storage tank n .

[0059] When calculating in detail, the volume of the liquid source container in the storage tank is:

[0060] V1 n =V1 n-1 +(V1b -V1 a ) / (H1 b -H1 a ).

[0061] LNG volume corresponding to the liquid source in the storage tank:

[0062] V2 n =V2 n-1 +(V2 b -V2 a ) / (H1 b -H1 a ).

[0063] LNG mass corresponding to the liquid source in the storage tank:

[0064] M1 n =M1 n-1 +(M1 b -M1 a ) / (H1 b -H1 a );

[0065] Where a and b are two adjacent liquid level height values ​​in the liquid level reference table when the storage tank leaves the factory, and b > a.

[0066] S2: Calculate the LNG density corresponding to the subdivided tank liquid source: ρ1 n =M1 n / V1 n *1000;

[0067] Calculate the liquid-gas conversion expansion rate of the subdivided storage tank liquid source: K1 n =V2 n / V1 n .

[0068] S3: Calculate the LNG density corresponding to the purchased LNG source based on the vaporization rate K2 of the purchased LNG source: ρ2 n =(1000 / K2)*(K1) n / 1000).

[0069] Users input the vaporization rate K2 of the purchased liquid source based on the gas quality report of the purchased liquid source.

[0070] S4: Calculate the converted liquid level height: H2 n =(ρ1) n *H1 n ) / ρ2 n ;

[0071] Among them, the subdivided liquid level height H1 n This is obtained by reading the liquid level in the storage tank.

[0072] Calculate the liquid level height corresponding to the current value and the corresponding level gauge reading: H3 n =EVALUATE(H2) n ).

[0073] S5: Calculate the corresponding volume of LNG in the storage tank:

[0074] V3 n =V1 n +((V1 b -V1 a ) / (H1 b -H1 a ))*(H2 n -H1 n );

[0075] Calculate the actual LNG mass corresponding to the change in gas source density:

[0076] M2 n =M1 n +((M1 b -M1 a ) / (H1 b -H1 a ))*(H2 n -H1 n ).

[0077] S6: Calculate the mass corresponding to the current level gauge reading:

[0078] M3 n =LOOKUP(H3) n H1 n H1 a M1 n M1 a );

[0079] Calculate the difference in inventory readings: M4 n =M2 n -M3 n .

[0080] Where n is the sequence number.

[0081] This invention uses the liquid level reference table from the storage tank manufacturer to subdivide the liquid source container volume V1 of the storage tank. n LNG volume V2 corresponding to the liquid source in the storage tank n LNG mass M1 corresponding to the liquid source in the storage tank n Furthermore, the LNG density ρ1 corresponding to the liquid source in the storage tank is calculated in detail. n The expansion rate K1 of liquid source and gas conversion in the storage tank n Based on the vaporization rate K2 of the LNG liquid purchased by the gas station, the converted liquid level height H2 is calculated sequentially.n The change in gas source density corresponds to the actual LNG mass M2 n Calculate the difference M4 between the inventory readings and the actual inventory readings. n .

[0082] This invention is applied to the acquisition of differential pressure signals in fixed storage tanks of LNG refueling stations. It can automatically detect and calculate the deviation in tank inventory caused by changes in gas source when converting inventory levels from tables. It displays the current liquid level corresponding to the table quality and the corrected inventory quality, and calculates the difference between the two. This facilitates data statistics and management for refueling stations and reduces the impact of errors on the key loss amount in data quality management during operation.

[0083] In step S1, the container volume, LNG volume, and LNG mass in the liquid level reference table from the storage tank manufacturer are subdivided into equal 1mm increments based on the liquid level height. This invention performs subdivision calculations based on the original liquid level reference table, facilitating the calculation of the actual LNG mass M2 corresponding to changes in gas source density. n Calculate the difference M4 between the inventory readings and the actual inventory readings. n This improves calculation accuracy.

[0084] It is important to note that the temperature inside the storage tank varies depending on the LNG liquid level. The higher the liquid level, the lower the temperature and pressure inside the tank, and the lower the LNG density ρ1 corresponding to the liquid source in the tank. n The expansion rate K1 of liquid source and gas conversion in the storage tank n The density decreases. Therefore, the LNG density ρ1 corresponding to the liquid source in the storage tank is... n The expansion rate K1 of liquid source and gas conversion in the storage tank n The reduction is not constant and needs to be based on the volume V1 of the liquid source container in the storage tank at each liquid level. n LNG volume V2 corresponding to the liquid source in the storage tank n LNG mass M1 corresponding to the liquid source in the storage tank n Calculated.

[0085] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A method for solving the calculation error of tank inventory caused by different densities of LNG liquid, characterized in that: Includes the following steps: S1: Calculate the subdivided liquid level height H1 by subdividing the liquid level height H1 and the corresponding container volume, LNG volume, and LNG mass from the liquid level reference table provided by the storage tank manufacturer. n Volume V1 of the liquid source container in the storage tank n LNG volume V2 corresponding to the liquid source in the storage tank n LNG mass M1 corresponding to the liquid source in the storage tank n ; S2: Calculate the LNG density corresponding to the subdivided storage tank liquid source: p1 n = M1 n / V1 n 1000; Compute the conversion expansion ratio of the subdivided reservoir source liquid and gas: K1 n = V2 n = V1 n ; S3: According to the purchase liquid source gasification rate K2 of the LNG liquid purchased by the gas station, the LNG density corresponding to the purchase liquid source is calculated: p2 n = (1000 / K2) (K1 n / 1000); S4: Calculate the converted liquid level height: H2 n = (p1 n H1 n ) / p2 n ; Calculate the liquid level height corresponding to the current value of the liquid level gauge reading: H3 n = EVALUATE(H2 n ); S5: Calculate the corresponding volume of LNG in the storage tank: V3 n =V1 n +((V1 b -V1 a ) / (H1 b -H1 a )) (H2 n -H1 n ); Calculate the actual LNG mass corresponding to the change in gas source density: M2 n =M1 n +((M1 b -M1 a ) / (H1 b -H1 a )) (H2 n -H1 n ); S6: Calculate the mass corresponding to the current level gauge reading: M3 n =LOOKUP(H3 n , H1 n :H1 a , M1 n :M1 a ); Calculate inventory reading Calculate difference: M4 n = M2 n - M3 n ; Where n is the sequence number; In step S1, the container volume, LNG volume, and LNG mass in the liquid level reference table from the tank manufacturer are subdivided into equal parts of 1mm each according to the liquid level height. In step S1, during the detailed calculation, the volume of the liquid source container in the storage tank is: V1 n =V1 n-1 +(V1 b -V1 a ) / (H1 b -H1 a ); In step S1, during the detailed calculation, the LNG volume corresponding to the liquid source in the storage tank is: V2 n =V2 n-1 +(V2 b -V2 a ) / (H1 b -H1 a ); In step S1, during the detailed calculation, the mass of LNG corresponding to the liquid source in the storage tank is: M1 n =M1 n-1 +(M1 b -M1 a ) / (H1 b -H1 a ); Where a and b are two adjacent liquid level height values ​​in the liquid level reference table when the storage tank is shipped from the factory, and b > a; In step S4, the converted liquid level height H2 is calculated n The subdivided liquid level height H1 is obtained by reading the tank level n from the tank level reading In step S3, the LNG density p2 corresponding to the procurement liquid source is calculated n At this time, the user inputs the vaporization rate K2 of the procurement liquid source according to the procurement liquid source quality report.

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