A method and apparatus for analyzing the content of impurities in liquid carbon dioxide in a pressure storage tank.

Abstract

This invention provides a method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank, comprising: determining the gas phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before taking out a specific volume of liquid carbon dioxide from the bottom of the tank; calculating the gas-liquid equilibrium constant, mole number, and mole fraction of each component in the pressure storage tank before taking out the liquid; calculating the liquid phase mole fraction of each component in the pressure storage tank before taking out the liquid; calculating the mole fraction of each component in the pressure storage tank after taking out the specific volume of liquid carbon dioxide; and determining the impurity content of the liquid carbon dioxide in the pressure storage tank after taking out the specific volume of liquid carbon dioxide. This invention enables dynamic analysis of the impurity content of liquid carbon dioxide in pressure storage tanks, solving the problems of high difficulty and low accuracy in measuring the composition of impurities in liquid carbon dioxide in pressure storage tanks, and providing a basis for subsequent research on carbon dioxide pipeline transportation technology.

Description

Technical Field

[0001] This invention relates to the field of carbon storage science and engineering technology, and is applied to carbon capture, utilization and storage (CCUS) technology. Specifically, it relates to a method and apparatus for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank. Background Technology

[0002] As a primary means of CO2 emission reduction, carbon capture, utilization, and storage (CCUS) technology is of great significance. In CCUS technology, CO2, after being captured and purified, is typically stored in a liquid pressure tank. Under normal operation, the upper part of the tank contains gas and the lower part contains liquid, with CO2 being removed from the drain port at the bottom of the tank.

[0003] Even after purification, CO2 stored in pressure tanks still contains certain impurities. As temperature and pressure change, the gas-liquid phase equilibrium within the tank alters, leading to changes in the impurity content of the extracted liquid CO2. Due to the high volatility of liquid CO2 containing impurities, measuring its impurity composition is difficult and requires low precision. Furthermore, impurities significantly impact the physical properties, phase characteristics, and pipeline transportation characteristics of CO2. Compared to traditional liquefied natural gas (LNG) storage and transportation technologies, the control of impurity content during CO2 storage and transportation is much more stringent, necessitating accurate measurement of the dynamic changes in the impurity content of liquid CO2. Currently, there is no mature method to accurately analyze the impurity content of liquid CO2 within pressure tanks.

[0004] To address the problems of existing technologies, this invention provides a method and apparatus for analyzing the content of impurities in liquid carbon dioxide inside a pressure storage tank. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a method and apparatus for analyzing the impurity content of liquid CO2 in pressure storage tanks, solving the problem that existing storage and transportation technologies cannot accurately measure the impurity content of liquid CO2 in pressure storage tanks, and laying the foundation for subsequent research on CO2 pipeline transportation technology.

[0006] This invention provides a method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank, the method comprising:

[0007] S1. Before taking out a specific volume of liquid carbon dioxide from the bottom of the pressure tank, obtain a sample of gaseous carbon dioxide from the top of the pressure tank to determine the gaseous mole fraction and thermodynamic parameters of each component in the pressure tank before taking out the liquid.

[0008] S2. Based on the gas phase mole fraction and thermodynamic parameters of each component in the pressure tank before liquid extraction, the gas-liquid equilibrium constant, mole number and mole fraction of each component in the pressure tank before liquid extraction are calculated.

[0009] S3. Calculate the liquid phase mole fraction of each component in the pressure tank before liquid extraction by using the gas-liquid equilibrium constant and mole fraction of each component in the pressure tank before liquid extraction.

[0010] S4. After taking out a specific volume of liquid carbon dioxide from the bottom of the pressure tank, calculate the mole fraction of each component in the pressure tank after taking out the liquid based on the number of moles of each component in the pressure tank before taking out the liquid and the mole fraction of each component in the liquid phase.

[0011] S5. Based on the mole fraction of each component in the pressure storage tank after liquid extraction, determine the impurity content of the liquid carbon dioxide in the pressure storage tank after extracting a specific volume of liquid carbon dioxide.

[0012] According to an embodiment of the present invention, step S1 includes: analyzing the gaseous carbon dioxide sample using gas chromatography to determine the type and content of impurities in the gaseous carbon dioxide sample, so as to determine the gas phase molar fraction and thermodynamic parameters of each component in the pressure storage tank before liquid collection, wherein the thermodynamic parameters include: critical temperature, critical pressure, eccentricity factor, and binary interaction coefficient.

[0013] According to an embodiment of the present invention, in step S2, the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are calculated through the following steps:

[0014] Using the critical temperature, the critical pressure, and the eccentricity factor, the estimated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained.

[0015] The mole fraction of each component in the liquid phase in the pressure tank before liquid extraction is calculated using the gaseous mole fraction of each component in the pressure tank before liquid extraction.

[0016] By using the equation of state, combined with the binary interaction coefficient and the molar volume of each component in the liquid phase, the molar volume of each component in the gas phase and liquid phase in the pressure storage tank before liquid extraction is calculated.

[0017] The compressibility factors of the gas and liquid phases in the pressure tank before liquid extraction are calculated using the molar volumes of each component in the gas and liquid phases.

[0018] The fugacity coefficients of each component in the gas and liquid phases of the pressure storage tank before liquid extraction are calculated using the compressibility factors of the gas and liquid phases in the pressure storage tank before liquid extraction.

[0019] When gas-liquid equilibrium is reached, the fugacity of the gas phase and liquid phase of each component is equal. Based on this, the calculated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained.

[0020] Compare the estimated and calculated values ​​of the gas-liquid equilibrium constants of each component. If the accuracy requirements are met, record the calculated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction.

[0021] According to an embodiment of the present invention, in step S2, the molar number of each component in the pressure storage tank before liquid extraction is calculated through the following steps:

[0022] Based on the shape and liquid level of the pressure tank, and combined with the molar volume of the gas and liquid phases in the pressure tank before liquid extraction, the number of moles of the gas and liquid phases in the pressure tank before liquid extraction can be calculated.

[0023] The number of moles of each component in the pressure tank before liquid extraction is calculated by using the number of moles of the gas and liquid phases in the tank before liquid extraction.

[0024] According to an embodiment of the present invention, in step S2, the mole fraction of each component in the pressure storage tank before liquid extraction is calculated through the following steps:

[0025] The carbon dioxide vaporization rate in the pressure storage tank before liquid extraction was calculated using the number of moles of each component in the tank before liquid extraction.

[0026] The mole fractions of each component in the pressure storage tank before liquid extraction are calculated using the liquid phase mole fractions, gas-liquid equilibrium constants, and carbon dioxide vaporization rates of each component in the tank before liquid extraction.

[0027] According to an embodiment of the present invention, step S3 includes:

[0028] The carbon dioxide vaporization rate in the pressure storage tank before liquid extraction is calculated using the gas-liquid equilibrium constants and mole fractions of each component in the tank before liquid extraction.

[0029] By utilizing the carbon dioxide vaporization rate, combined with the gas-liquid equilibrium constants and mole fractions of each component in the pressure storage tank before liquid extraction, the mole fractions of the liquid phase of each component in the pressure storage tank before liquid extraction can be calculated.

[0030] According to an embodiment of the present invention, step S4 includes:

[0031] The number of moles of each component in the pressure storage tank before liquid extraction, the mole fraction of each component in the liquid phase, and the molar volume of the liquid phase are used, combined with the volume of liquid extraction, to calculate the number of moles of each component in the pressure storage tank after liquid extraction.

[0032] The mole fraction of each component in the pressure storage tank after liquid extraction is calculated by using the number of moles of each component in the pressure storage tank after liquid extraction.

[0033] According to an embodiment of the present invention, step S5 includes:

[0034] Based on the mole fraction of each component in the pressure storage tank after liquid extraction, and combined with the mole fraction of each component in the liquid phase in the pressure storage tank before liquid extraction, the impurity content of the liquid carbon dioxide in the pressure storage tank after extracting a specific volume of liquid carbon dioxide is determined.

[0035] According to another aspect of the invention, a storage medium is also provided, which includes a series of instructions for performing the steps of the method described in any of the preceding claims.

[0036] According to another aspect of the present invention, an apparatus for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank is also provided, performing the method as described in any of the preceding claims, the apparatus comprising:

[0037] A gas outlet is located on the upper part of the pressure storage tank and is used to obtain gaseous carbon dioxide samples from the upper part of the pressure storage tank.

[0038] The drain section is located at the bottom of the pressure storage tank and is used to obtain liquid carbon dioxide from the bottom of the pressure storage tank.

[0039] The condition monitoring unit, located inside the pressure storage tank, is used to measure the pressure, temperature, gas-liquid interface position, and discharge flow rate of the drain section within the pressure storage tank.

[0040] This invention provides a method and apparatus for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank, which has the following advantages compared with the prior art:

[0041] This invention establishes a device for analyzing the impurity content of liquid carbon dioxide in pressure storage tanks and proposes a method for analyzing the impurity content of liquid CO2 based on the principles of thermodynamics and mass conservation. Using easily measurable parameters such as temperature, pressure, gas-liquid interface position, and discharge pipeline flow rate within the storage tank as a basis, the solubility of different impurities in liquid CO2 is calculated, enabling dynamic analysis of the impurity content of liquid CO2 in pressure storage tanks. This solves the problems of difficulty and low accuracy in measuring the composition of impurities in liquid CO2 within pressure storage tanks, providing a basis for subsequent research on CO2 pipeline transportation technology.

[0042] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0043] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0044] Figure 1 A flowchart illustrating the steps of a method for analyzing the content of impurities in liquid carbon dioxide in a pressure storage tank according to an embodiment of the present invention is shown.

[0045] Figure 2 A graph showing the relationship between cumulative liquid volume and pressure and liquid level according to an embodiment of the present invention is displayed.

[0046] Figure 3 The graph showing the relationship between the cumulative liquid volume and the mole fraction of each component in the liquid phase according to an embodiment of the present invention is shown.

[0047] Figure 4 A schematic diagram of a device for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank according to an embodiment of the present invention is shown.

[0048] In the accompanying drawings, the same parts use the same reference numerals. Also, the drawings are not drawn to scale.

[0049] The meanings of the reference numerals in the attached drawings are as follows: 1-Pressure storage tank body; 2-Level gauge; 3-Pressure sensor; 4-Multi-point temperature sensor; 5-Gas outlet pipeline; 6-Drainage pipeline; 7-Flow meter; 8-First valve; 9-Second valve. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0051] Existing technology (CN215807871U) discloses a pressure relief device for a liquid carbon dioxide storage tank, including a carbon dioxide storage tank, a pressure relief box, and a pressure relief assembly. The pressure relief box is located on one side of the carbon dioxide storage tank, and the pressure relief assembly is located inside the pressure relief box. The carbon dioxide storage tank and the pressure relief box are connected by a connecting pipe, which transfers excess gas from the carbon dioxide storage tank to the pressure relief box, where it is released through the pressure relief assembly. The pressure relief box has a pressure relief chamber inside, and a regulating pipe is located inside the pressure relief chamber. The regulating pipe has a gas pressure storage chamber inside, and exhaust holes are located on both sides of the regulating pipe. This invention, through the coordinated use of a moving block, a turbine fan, a spiral spring, a fixed block, a slider, and a sliding groove, solves the problem of spring force attenuation caused by prolonged operation in existing pressure relief devices, thus reducing the impact force of high-pressure gas. However, the aforementioned prior art cannot achieve dynamic analysis of the impurity content of liquid CO2 in the pressure storage tank, nor can it solve the problems of difficulty and low accuracy in measuring the composition of impurities in liquid CO2 in the pressure storage tank.

[0052] The existing technology (CN217059537U) belongs to the field of food processing technology, specifically a sampling device for detecting food-grade carbon dioxide impurities. Addressing the problem of poor sealing during carbon dioxide sampling, the proposed solution includes a base, a placement seat fixed to the top of the base, a mounting frame fixed to the top of the base, an electric push rod at the top of the mounting frame, a lifting plate fixed to the output end of the electric push rod, and a mounting box fixed to the bottom of the lifting plate. In this invention, the lifting plate pushes a pressure plate to compress the mouth of the sampling bottle, causing the pressure plate to rise automatically. This allows a hollow probe to be inserted into the sampling bottle for sampling and testing. The tight fit between the pressure plate and the top of the sampling bottle ensures a tight seal during sampling. As the lifting plate descends, it also activates a clamping and sealing mechanism to seal around the mouth of the sampling bottle, further improving the airtightness of the device during sampling and testing, resulting in more accurate test data. However, the aforementioned existing technology cannot achieve dynamic analysis of the liquid CO2 impurity content in pressure storage tanks, nor can it solve the problems of difficulty and low accuracy in measuring the composition of liquid CO2 impurities in pressure storage tanks.

[0053] Existing technology (CN104713975B) discloses a method for simultaneously detecting hydrocarbon and nitrogen impurities in hydrogen, solving the problem that existing technologies cannot simultaneously detect these impurities. Using gas chromatography, under selected operating conditions, two gas samples are simultaneously introduced via an injection valve, entering two separate channels: one for analyzing hydrocarbons and the other for analyzing nitrogen content. The samples are separated using chromatographic columns, and then the hydrocarbon and nitrogen content in the samples are simultaneously detected using a thermal conductivity detector and a flame ionization detector. The results are calculated using the external standard method. This method is simple and fast. However, the aforementioned existing technology cannot achieve dynamic analysis of liquid CO2 impurities in pressure storage tanks, nor can it solve the problems of high difficulty and low accuracy in measuring the composition of liquid CO2 impurities in pressure storage tanks.

[0054] In CCUS (Chemical Compression System) technology, captured CO2 is typically stored in a pressure tank. When needed, the CO2 is removed from the drain port at the bottom of the tank. Impurities significantly affect the physical properties, phase characteristics, and pipeline transport characteristics of CO2, thus requiring accurate measurement of the impurity content in the removed CO2. However, liquid CO2 containing impurities is highly volatile, making direct measurement of its impurity composition difficult. Currently, no analytical methods have been reported for the impurity content of liquid CO2 within pressure tanks.

[0055] To address the shortcomings of existing technologies, this invention constructs a device for analyzing the impurity content of liquid carbon dioxide in pressure storage tanks. It proposes a method for analyzing the impurity content of liquid CO2 based on the principles of thermodynamics and mass conservation. Using easily measurable parameters such as temperature, pressure, gas-liquid interface position, and discharge pipeline flow rate within the tank as a basis, the solubility of different impurities in liquid CO2 is calculated. This enables dynamic analysis of the impurity content of liquid CO2 in pressure storage tanks, solving the problems of difficulty and low accuracy in measuring the composition of impurities in liquid CO2 within pressure storage tanks, and providing a basis for subsequent research on CO2 pipeline transportation technology.

[0056] Figure 1 A flowchart illustrating the steps of a method for analyzing the content of impurities in liquid carbon dioxide in a pressure storage tank according to an embodiment of the present invention is shown.

[0057] like Figure 1 As shown, in step S1, before taking out a specific volume of liquid carbon dioxide from the bottom of the pressure tank, a sample of gaseous carbon dioxide from the top of the pressure tank is obtained to determine the gaseous molar fraction and thermodynamic parameters of each component in the pressure tank before liquid extraction.

[0058] In one embodiment, step S1 includes: analyzing a gaseous carbon dioxide sample using gas chromatography to determine the type and content of impurities in the gaseous carbon dioxide sample, so as to determine the gas phase molar fraction and thermodynamic parameters of each component in the pressure storage tank before liquid collection, wherein the thermodynamic parameters include: critical temperature, critical pressure, eccentricity factor, and binary interaction coefficient.

[0059] like Figure 1 As shown, in step S2, based on the gas phase mole fraction and thermodynamic parameters of each component in the pressure tank before liquid extraction, the gas-liquid equilibrium constant, the number of moles of each component, and the mole fraction of each component in the pressure tank before liquid extraction are calculated.

[0060] In one embodiment, in step S2, the gas-liquid balance constants of each component in the pressure storage tank before liquid extraction are calculated through the following steps S201-S207.

[0061] In step S201, the estimated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained using the critical temperature, critical pressure, and eccentricity factor. Specifically, the estimated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained using the following expression (1):

[0062]

[0063] In the formula, K ie To estimate the gas-liquid equilibrium constants of each component, P ci Let P be the critical pressure of each component, and ω be the pressure. i T represents the eccentricity factor of each component. ciT represents the critical temperature of each component, where T is the temperature and the subscript i is the component number.

[0064] In step S202, the mole fraction of the liquid phase of each component in the pressure tank before liquid extraction is calculated using the gaseous mole fraction of each component in the pressure tank before liquid extraction. Specifically, the mole fraction of the liquid phase of each component in the pressure tank before liquid extraction is calculated using the following expression (2):

[0065]

[0066] In the formula, x i y represents the liquid phase mole fraction of each component. i The value represents the gas phase mole fraction of each component.

[0067] In step S203, the molar volumes of the gas and liquid phases of each component in the pressure tank before liquid extraction are calculated using the equation of state, combined with the binary interaction coefficients and the molar fractions of each component in the liquid phase. Specifically, taking the Peng-Robinson equation of state as an example, the molar volumes of the gas and liquid phases of each component in the pressure tank before liquid extraction are calculated using the following expressions (3)-(9):

[0068]

[0069] in:

[0070]

[0071]

[0072]

[0073]

[0074] b = ∑n i b i (8)

[0075]

[0076] In the formula, R is the molar gas constant, V is the molar volume of the gas or liquid phase, and k ij T is the binary interaction coefficient between component i and component j. ri Let n be the comparison temperature of component i. i This represents the mole fraction of each component in the gas or liquid phase, with the subscript j indicating the component number.

[0077] It should be noted that, in addition to the Peng-Robinson equation of state, other equations of state such as the SRK equation, BWRS equation, Span-Wagner equation, and GERG-2008 equation can also be used to calculate the molar volumes of the gas and liquid phases of each component in the pressure storage tank before liquid extraction. This invention does not impose any restrictions on the choice of equation of state.

[0078] In step S204, the compressibility factors of the gas and liquid phases in the pressure tank before liquid extraction are calculated using the molar volumes of each component in the gas and liquid phases. Specifically, the compressibility factors of the gas and liquid phases in the pressure tank before liquid extraction are calculated using the following expression (10):

[0079]

[0080] In the formula, Z is the gas or liquid phase compressibility factor containing impurities such as carbon dioxide.

[0081] In step S205, the fugacity coefficients of the gas and liquid phases in the pressure tank before liquid extraction are calculated using the compressibility factors of the gas and liquid phases. Specifically, the fugacity coefficients of the gas and liquid phases in the pressure tank before liquid extraction are calculated using the following expressions (11)-(12):

[0082]

[0083] in:

[0084]

[0085] In the formula, φ i Here, φ represents the fugacity coefficient of each component in the gas or liquid phase. Vi The fugacity coefficient of the liquid phase is denoted as φ. Li .

[0086] In step S206, when gas-liquid equilibrium is reached, the fugacity of the gas and liquid phases of each component is equal. Based on this, the calculated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained. Specifically, the calculated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained through the following expression (13):

[0087]

[0088] In the formula, K i These are the calculated values ​​of the gas-liquid equilibrium constants for each component.

[0089] In step S207, the estimated and calculated values ​​of the gas-liquid equilibrium constants of each component are compared. If the accuracy requirements are met, the calculated values ​​of the gas-liquid equilibrium constants of each component are recorded as the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction. Specifically, |K is determined. i -Kie The value of |, if the value is within the precision range, then K i This is the gas-liquid balance constant of each component in the storage tank before liquid extraction. If this value does not meet the accuracy requirements, then K... ie Updated to K i Repeat steps S201-S206 above until |K i -K ie The value of | satisfies the accuracy requirement, that is, the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained. Under the initial state before liquid extraction, the equilibrium constants of each component are denoted as K. oi The gas phase mole fraction is denoted as y. oi The liquid phase mole fraction is denoted as x. oi The molar volume of the gas phase is denoted as V. ov The molar volume of the liquid phase is denoted as V. oL .

[0090] In one embodiment, in step S2, the molar number of each component in the pressure storage tank before liquid extraction is calculated through the following steps S208-S209.

[0091] In step S208, based on the shape and liquid level of the pressure tank, and combined with the molar volumes of the gas and liquid phases in the pressure tank before liquid extraction, the molar numbers of the gas and liquid phases in the pressure tank before liquid extraction are calculated. Specifically, the molar numbers of the gas and liquid phases in the pressure tank before liquid extraction are calculated using the following expressions (14)-(18):

[0092]

[0093]

[0094] Taking a common spherical pressure tank as an example, when the liquid level is higher than the radius of the spherical tank, the volume of the liquid phase inside the tank is:

[0095]

[0096] When the liquid level is below the radius of the spherical tank, the volume of the liquid phase inside the tank is:

[0097]

[0098] The volume of the gas phase inside the storage tank is:

[0099]

[0100] In the formula, N ovi V represents the number of moles of gas in the tank under the initial conditions before liquid extraction. osv The volume of the gas phase in the storage tank under the initial conditions before liquid extraction, N oLi V represents the number of moles of liquid phase in the tank under the initial conditions before liquid extraction. osLR represents the initial liquid volume in the tank before liquid extraction. s Let h be the radius of the spherical tank. o This represents the initial liquid level inside the spherical tank before liquid extraction.

[0101] In step S209, the molar number of each component in the pressure tank before liquid extraction is calculated using the molar number of the gas and liquid phases in the pressure tank before liquid extraction. Specifically, the molar number of each component in the pressure tank before liquid extraction is calculated using the following expression (19):

[0102] N oti =N oLi +N ovi (19)

[0103] In the formula, N oti This represents the number of moles of each component in the storage tank in the initial state before liquid extraction.

[0104] In one embodiment, in step S2, the mole fraction of each component in the pressure storage tank before liquid extraction is calculated through the following steps S210-S211.

[0105] In step S210, the carbon dioxide vaporization rate in the pressure storage tank before liquid extraction is calculated using the molar number of each component in the tank before liquid extraction. Specifically, the carbon dioxide vaporization rate in the pressure storage tank before liquid extraction is calculated using the following expression (20):

[0106]

[0107] In the formula, e o This represents the vaporization rate of carbon dioxide containing impurities in the storage tank under the initial state before liquid extraction.

[0108] In step S211, the mole fractions of each component in the pressure tank before liquid extraction are calculated using the liquid phase mole fractions, gas-liquid equilibrium constants, and carbon dioxide vaporization rates of each component in the pressure tank before liquid extraction. Specifically, the mole fractions of each component in the pressure tank before liquid extraction are calculated using the following expression (21):

[0109] z oi =x oi [(K oi -1)e o +1] (21)

[0110] In the formula, z oi This represents the mole fraction of each component in the storage tank under the initial conditions before liquid extraction.

[0111] like Figure 1 As shown, in step S3, the liquid phase mole fraction of each component in the pressure tank before liquid extraction is calculated by using the gas-liquid equilibrium constant and the mole fraction of each component in the pressure tank before liquid extraction.

[0112] In one embodiment, step S3 includes: calculating the carbon dioxide vaporization rate in the pressure tank before liquid extraction using the gas-liquid equilibrium constant and mole fraction of each component in the pressure tank before liquid extraction; and calculating the liquid phase mole fraction of each component in the pressure tank before liquid extraction using the carbon dioxide vaporization rate, combined with the gas-liquid equilibrium constant and mole fraction of each component in the pressure tank before liquid extraction.

[0113] Specifically, in step S3, the carbon dioxide vaporization rate in the pressure storage tank before liquid extraction is calculated using the following expression (22):

[0114]

[0115] In the formula, e is the carbon dioxide vaporization rate of impurities in the storage tank.

[0116] Specifically, in step S3, the molar fraction of each component in the liquid phase in the pressure storage tank before liquid extraction is calculated using the following expressions (23)-(24):

[0117]

[0118]

[0119] In the formula, x i y represents the liquid phase mole fraction of each component. i The value represents the gas phase mole fraction of each component.

[0120] like Figure 1 As shown, in step S4, after a specific volume of liquid carbon dioxide is taken out from the bottom of the pressure tank, the mole fraction of each component in the pressure tank after taking out the liquid is calculated based on the number of moles of each component in the pressure tank before taking out the liquid and the mole fraction of each component in the liquid phase.

[0121] In one embodiment, step S4 includes: calculating the number of moles of each component in the pressure tank after liquid extraction by using the number of moles of each component in the pressure tank before liquid extraction, the mole fraction of each component in the liquid phase, and the molar volume of the liquid phase, combined with the liquid extraction volume; and calculating the mole fraction of each component in the pressure tank after liquid extraction by using the number of moles of each component in the pressure tank after liquid extraction.

[0122] Specifically, in step S4, the molar number of each component in the pressure storage tank after liquid extraction is calculated using the following expression (25):

[0123] After a volume of liquid dv is removed from the drain outlet, the molar number of each component in the storage tank is:

[0124]

[0125] In the formula, N niThis represents the number of moles of each component in the storage tank after a volume of liquid of dv is removed from the tank under the current condition.

[0126] Specifically, in step S4, the mole fraction of each component in the pressure storage tank after liquid extraction is calculated using the following expression (26):

[0127]

[0128] In the formula, z ni This represents the mole fraction of each component in the tank under the current condition.

[0129] like Figure 1 As shown, in step S5, the impurity content of the liquid carbon dioxide in the pressure storage tank after a specific volume of liquid carbon dioxide is determined based on the mole fraction of each component in the pressure storage tank after liquid extraction.

[0130] In one embodiment, step S5 includes: determining the impurity content of the liquid carbon dioxide in the pressure tank after a specific volume of liquid carbon dioxide is taken out, based on the mole fraction of each component in the pressure tank after liquid extraction and the liquid phase mole fraction of each component in the pressure tank before liquid extraction.

[0131] Specifically, when the liquid is not removed from the drain port, the initial mole fraction of each component in the storage tank is z. oi Based on the pressure and average temperature measured by the tank's operating status monitoring device, the gas-liquid equilibrium constant K of each component inside the tank is determined. i Iterative calculations determine the gas-liquid equilibrium constants (denoted as K) of each component in the tank under the current state. ni This allows us to determine the mole fraction of the gas phase in the storage tank (denoted as y). ni ) and liquid phase mole fraction (denoted as x) ni This allows us to determine the impurity content of the liquid CO2 in its current state. The current molar volume of the gas phase is denoted as V. nv The molar volume of the liquid phase is denoted as V. nL .

[0132] Furthermore, when removing liquid from the drain outlet, it is necessary to recalculate the mole fraction of each component in the storage tank and determine the mole fraction z of each component. ni Then, by calculating the molar fraction of the liquid phase in the tank under the current condition, the impurity content of the liquid CO2 in the tank after taking out a volume of dv of liquid can be determined.

[0133] In one embodiment, by repeating the above calculation process with the current state as the initial state, the change in the liquid CO2 impurity content during the tank extraction process can be obtained. Taking CO2 containing impurities with an initial N2 molar fraction of 4% and a CH4 molar fraction of 1% as an example, and combining monitoring data of temperature, pressure, liquid level, and drain pipeline flow rate, a curve showing the relationship between the liquid CO2 impurity content and different parameters is plotted, such as... Figure 2 , Figure 3 As shown.

[0134] The present invention provides a method and apparatus for analyzing the content of impurities in liquid carbon dioxide in a pressure storage tank. This method and apparatus can also be used in conjunction with a computer-readable storage medium. The storage medium stores a computer program, which is executed to run the method for analyzing the content of impurities in liquid carbon dioxide in a pressure storage tank. The computer program is capable of executing computer instructions, which include computer program code. The computer program code can be in the form of source code, object code, executable file, or some intermediate form.

[0135] Computer-readable storage media can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0136] It should be noted that the contents of computer-readable storage media may be appropriately added to or subtracted from the contents according to the requirements of legislation and patent practice in a jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable storage media may not include electrical carrier signals and telecommunication signals.

[0137] Figure 4 A schematic diagram of a device for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank according to an embodiment of the present invention is shown.

[0138] An apparatus for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank is disclosed, comprising a gas extraction section, a liquid discharge section, and a status monitoring section. The gas extraction section is located at the upper part of the pressure storage tank body 1 and is used to acquire gaseous carbon dioxide samples from the upper part of the pressure storage tank 1. The liquid discharge section is located at the bottom of the pressure storage tank body 1 and is used to acquire liquid carbon dioxide from the bottom of the pressure storage tank 1. The status monitoring section is located in the pressure storage tank body 1 and is used to measure the pressure, temperature, gas-liquid interface position, and discharge flow rate of the liquid discharge section within the pressure storage tank 1.

[0139] In one embodiment, such as Figure 1 As shown, the gas outlet section includes a first valve 8 and a gas outlet pipeline 5, which are sequentially connected to the upper part of the pressure storage tank 1.

[0140] In one embodiment, such as Figure 1As shown, the gas-liquid discharge section includes a second valve 9 and a discharge pipeline 6 connected in sequence to the bottom of the pressure storage tank 1. When obtaining a gaseous carbon dioxide sample from the upper part of the pressure storage tank 1, the gas outlet pipeline 5 is connected to the sampling bottle. Under stable conditions, the second valve 9 is closed, the first valve 8 is slowly opened, and the gaseous carbon dioxide sample containing impurities is taken out. Then, the first valve 8 is closed, and the gaseous carbon dioxide sample is sealed and preserved. The pressure, temperature, and gas-liquid interface position inside the pressure storage tank 1 at this time are recorded as the initial state before liquid collection.

[0141] In one embodiment, such as Figure 1 As shown, the status monitoring unit includes: a level gauge 2, a pressure sensor 3, a multi-point temperature sensor 4, and a flow meter 7.

[0142] Specifically, the level gauge 2 is installed inside the pressure storage tank 1 to monitor the position of the gas-liquid interface within the tank. The pressure sensor 3 is installed on the inner wall of the pressure storage tank 1 to monitor the pressure inside the tank. The multi-point temperature sensor 4 is located in the pressure storage tank 1 to monitor the temperature at multiple points within the tank. The flow meter 7 is installed between the second valve 9 and the drain line 6 to measure the discharge flow rate of the drain section.

[0143] In summary, the device includes a pressure storage tank 1, a level gauge 2, a flow meter 7, a pressure sensor 3, a multi-point temperature sensor 4, a gas outlet pipeline 5, a drain pipeline 6, a first valve 8, and a second valve 9. The pressure storage tank 1 is used to hold liquid CO2 under pressure; the level gauge 2 is used to monitor the gas-liquid interface position within the tank; the flow meter 7 is used to measure the amount of liquid CO2 extracted from the drain pipeline 5; the pressure sensor 3 is used to monitor the pressure inside the tank; the multi-point temperature sensor 4 is used to monitor the average temperature inside the tank; the gas outlet pipeline 5 is used to extract CO2 gas samples from the top of the tank; and the drain pipeline 6 is used to extract liquid CO2 from the bottom of the tank. The device is used to monitor and record changes in the tank level, volume of liquid extracted, pressure, and temperature.

[0144] An analysis device for liquid carbon dioxide impurity content in a pressure storage tank further includes an analysis unit that performs an analysis method for liquid carbon dioxide impurity content in a pressure storage tank to analyze and calculate the liquid carbon dioxide impurity content in the pressure storage tank.

[0145] In summary, this invention provides a method and apparatus for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank, which has the following advantages compared with the prior art:

[0146] This invention establishes a device for analyzing the impurity content of liquid carbon dioxide in pressure storage tanks and proposes a method for analyzing the impurity content of liquid CO2 based on the principles of thermodynamics and mass conservation. Using easily measurable parameters such as temperature, pressure, gas-liquid interface position, and discharge pipeline flow rate within the storage tank as a basis, the solubility of different impurities in liquid CO2 is calculated, enabling dynamic analysis of the impurity content of liquid CO2 in pressure storage tanks. This solves the problems of difficulty and low accuracy in measuring the composition of impurities in liquid CO2 within pressure storage tanks, providing a basis for subsequent research on CO2 pipeline transportation technology.

[0147] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0148] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0149] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0150] Certain terms are used throughout this application to refer to specific system components. As those skilled in the art will recognize, the same components may often be referred to by different names, and therefore this application is not intended to distinguish those components that differ only in name and not in function. In this application, the terms “comprise,” “include,” and “have” are used in an open-ended manner and should therefore be interpreted as meaning “including, but not limited to…”. Furthermore, the terms “substantially,” “materially,” or “approximately” as used herein refer to industry-accepted tolerances for the corresponding terms. The term “coupling,” as may be used herein, includes direct coupling and indirect coupling via additional components, elements, circuits, or modules, wherein, for indirect coupling, the intermediate component, element, circuit, or module does not alter the information of the signal but may adjust its current level, voltage level, and / or power level. Inferred coupling (e.g., one element is inferredly coupled to another element) includes direct and indirect coupling between two elements in the same manner as “coupling.”

[0151] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0152] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

[0153] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for analyzing the content of impurities in liquid carbon dioxide in a pressure storage tank, characterized in that, The method includes: S1. Before taking out a specific volume of liquid carbon dioxide from the bottom of the pressure tank, a sample of gaseous carbon dioxide from the top of the pressure tank is obtained to determine the gas phase mole fraction and thermodynamic parameters of each component in the pressure tank before liquid extraction. The thermodynamic parameters include: critical temperature, critical pressure, eccentricity factor, and binary interaction coefficient. S2. Based on the gas phase mole fraction and thermodynamic parameters of each component in the pressure tank before liquid extraction, the gas-liquid equilibrium constant, mole number and mole fraction of each component in the pressure tank before liquid extraction are calculated. S3. Calculate the liquid phase mole fraction of each component in the pressure tank before liquid extraction by using the gas-liquid equilibrium constant and mole fraction of each component in the pressure tank before liquid extraction. S4. After taking out a specific volume of liquid carbon dioxide from the bottom of the pressure tank, calculate the mole fraction of each component in the pressure tank after taking out the liquid based on the number of moles of each component in the pressure tank before taking out the liquid and the mole fraction of each component in the liquid phase. S5. Based on the mole fraction of each component in the pressure storage tank after liquid extraction, determine the impurity content of the liquid carbon dioxide in the pressure storage tank after extracting a specific volume of liquid carbon dioxide. In step S2, the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are calculated through the following steps: Step S201: Using the critical temperature, the critical pressure, and the eccentricity factor, estimate the gas-liquid equilibrium constant K of each component in the pressure storage tank before liquid extraction. ie ; Step S202: Calculate the mole fraction of liquid phase of each component in the pressure tank before liquid extraction using the gaseous mole fraction of each component in the pressure tank before liquid extraction. Step S203: Using the equation of state, combined with the binary interaction coefficient and the molar volume of liquid phase of each component, calculate the molar volume of gas phase and liquid phase of each component in the pressure storage tank before liquid extraction. Step S204: Calculate the compressibility factors of the gas and liquid phases in the pressure tank before liquid extraction by using the molar volumes of the gas and liquid phases of each component in the pressure tank before liquid extraction. Step S205: Calculate the fugacity coefficients of the gas and liquid phases of each component in the pressure tank before liquid extraction using the compressibility factors of the gas and liquid phases in the pressure tank before liquid extraction. In step S206, when gas-liquid equilibrium is reached, the fugacity of the gas and liquid phases of each component is equal. Based on this, the calculated value K of the gas-liquid equilibrium constant of each component in the pressure storage tank before liquid extraction is obtained. i ; Step S207: Compare the estimated and calculated values ​​of the gas-liquid equilibrium constants of each component. If the accuracy requirements are met, record the calculated values ​​of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction. In step S207, it is determined that |K i -K ie The value of |, if the value is within the precision range, then K i This is the gas-liquid balance constant of each component in the storage tank before liquid extraction. If this value does not meet the accuracy requirements, then K... ie Updated to K i Repeat steps S202-S206 until |K i -K ie The value of | meets the precision requirements.

2. The method for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank as described in claim 1, characterized in that, Step S1 includes: analyzing the gaseous carbon dioxide sample using gas chromatography to determine the type and content of impurities in the gaseous carbon dioxide sample, so as to determine the gas phase molar fraction and thermodynamic parameters of each component in the pressure storage tank before liquid collection.

3. The method for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank as described in claim 1, characterized in that, In step S2, the molar number of each component in the pressure storage tank before liquid extraction is calculated through the following steps: Based on the shape and liquid level of the pressure tank, and combined with the molar volume of the gas and liquid phases in the pressure tank before liquid extraction, the number of moles of the gas and liquid phases in the pressure tank before liquid extraction can be calculated. The number of moles of each component in the pressure tank before liquid extraction is calculated by using the number of moles of the gas and liquid phases in the tank before liquid extraction.

4. The method for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank as described in claim 1, characterized in that, In step S2, the mole fraction of each component in the pressure storage tank before liquid extraction is calculated through the following steps: The carbon dioxide vaporization rate in the pressure storage tank before liquid extraction is calculated using the number of moles of each component in the tank before liquid extraction. The mole fractions of each component in the pressure storage tank before liquid extraction are calculated using the liquid phase mole fractions, gas-liquid equilibrium constants, and carbon dioxide vaporization rates of each component in the tank before liquid extraction.

5. The method for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank as described in claim 1, characterized in that, Step S3 includes: The carbon dioxide vaporization rate in the pressure storage tank before liquid extraction is calculated using the gas-liquid equilibrium constants and mole fractions of each component in the tank before liquid extraction. By utilizing the carbon dioxide vaporization rate, combined with the gas-liquid equilibrium constants and mole fractions of each component in the pressure storage tank before liquid extraction, the mole fractions of the liquid phase of each component in the pressure storage tank before liquid extraction can be calculated.

6. The method for analyzing the content of impurities in liquid carbon dioxide in a pressure storage tank as described in claim 1, characterized in that, Step S4 includes: The number of moles of each component in the pressure storage tank before liquid extraction, the mole fraction of each component in the liquid phase, and the molar volume of the liquid phase are used, combined with the volume of liquid extraction, to calculate the number of moles of each component in the pressure storage tank after liquid extraction. The mole fraction of each component in the pressure storage tank after liquid extraction is calculated by using the number of moles of each component in the pressure storage tank after liquid extraction.

7. A method for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank as described in any one of claims 1-6, characterized in that, Step S5 includes: Based on the mole fraction of each component in the pressure storage tank after liquid extraction, and combined with the mole fraction of each component in the liquid phase in the pressure storage tank before liquid extraction, the impurity content of the liquid carbon dioxide in the pressure storage tank after extracting a specific volume of liquid carbon dioxide is determined.

8. A storage medium, characterized in that, It includes a series of instructions for performing the method steps as described in any one of claims 1-7.

9. A device for analyzing the content of impurities in liquid carbon dioxide inside a pressure storage tank, characterized in that, The device includes: A gas outlet is located on the upper part of the pressure storage tank and is used to obtain gaseous carbon dioxide samples from the upper part of the pressure storage tank. The drain section is located at the bottom of the pressure storage tank and is used to obtain liquid carbon dioxide from the bottom of the pressure storage tank. The condition monitoring unit is installed in the pressure tank body and is used to measure the pressure, temperature, gas-liquid interface position and discharge flow rate of the liquid draining unit inside the pressure tank. The analysis unit performs a method for analyzing the content of liquid carbon dioxide impurities in a pressure storage tank as described in any one of claims 1-7, in order to analyze and calculate the content of liquid carbon dioxide impurities in the pressure storage tank.

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