Method and device for analyzing impurity content of liquid carbon dioxide in pressure storage tank

Abstract

The invention provides a method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank, which comprises the following steps of: before taking a specific volume of liquid carbon dioxide from the bottom of the pressure storage tank, determining the gas phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before taking the liquid; calculating a gas-liquid equilibrium constant, a mole number and a mole fraction of each component in the pressure storage tank before liquid taking; calculating the liquid phase mole fraction of each component in the pressure storage tank before liquid taking; after liquid carbon dioxide with a specific volume is taken out from the bottom of the pressure storage tank, the mole fraction of each component in the pressure storage tank after liquid taking is calculated; and determining the impurity content of the liquid carbon dioxide in the pressure storage tank after the specific volume of liquid carbon dioxide is taken out. Dynamic analysis of the content of the liquid carbon dioxide impurities in the pressure storage tank is realized, the problems of high difficulty and low precision in measurement of the composition of the liquid carbon dioxide impurities in the pressure storage tank are solved, and a basis is provided for subsequent research on a carbon dioxide pipeline transportation technology.

Description

Technical Field

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

[0002] As a main means of CO 2 emission reduction, carbon capture, utilization and storage (CCUS) technology is of great significance. In CCUS technology, after being captured and purified, CO 2 is usually stored in a liquid pressure storage tank. During normal operation, the upper part of the storage tank is gas and the lower part is liquid. CO 2 is taken out from the liquid discharge port at the bottom of the storage tank.

[0003] The CO 2 stored in the pressure storage tank after purification still contains certain impurities. With the change of temperature and pressure, the gas-liquid phase equilibrium in the storage tank changes, and the impurity content of the taken-out liquid CO 2 also changes accordingly. Due to the high volatility of liquid CO with impurities, it is difficult to measure its impurity composition with high difficulty and low accuracy. And impurities have an important impact on the physical properties, phase characteristics and pipeline transportation characteristics of CO 2 . Compared with the traditional liquefied natural gas storage and transportation technology, the control requirements for the impurity content in the CO 2 storage and transportation process are more stringent, and it is necessary to accurately measure the dynamic change of the impurity content of liquid CO 2 . At present, there is no mature method to accurately analyze the impurity content of liquid CO 2 in a pressure storage tank. 2

[0004] In view of the problems of the existing technology, the present invention provides a method and device for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank. Summary of the Invention

[0005] Aiming at the defects of the current existing technology, the present invention aims to provide a method and device for analyzing the impurity content of liquid CO 2 in a pressure storage tank, to solve the problem that it is difficult to accurately measure the impurity content of liquid CO 2 in a pressure storage tank in the existing storage and transportation technology, and to lay a foundation for the subsequent research on CO 2 pipeline transportation technology.

[0006] The present invention provides a method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank, and the method includes:

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

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

[0009] S3. Through the gas-liquid equilibrium constant and the mole fraction of each component in the pressure storage tank before liquid extraction, calculate the liquid-phase mole fraction of each component in the pressure storage tank before liquid extraction.

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

[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 taking out 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 by gas chromatography to determine the type and content of impurities in the gaseous carbon dioxide sample, so as to determine the gas-phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before liquid extraction, wherein the thermodynamic parameters include: critical temperature, critical pressure, acentric factor, binary interaction coefficient.

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

[0014] Estimate the estimated value of the gas-liquid equilibrium constant of each component in the pressure storage tank before liquid extraction by using the critical temperature, the critical pressure, and the acentric factor;

[0015] Calculate the liquid-phase mole fraction of each component in the pressure storage tank before liquid extraction by using the gas-phase mole fraction of each component in the pressure storage tank before liquid extraction;

[0016] Calculate the gas-phase and liquid-phase molar volumes of each component in the pressure storage tank before liquid extraction through the equation of state, in combination with the binary interaction coefficient and the liquid-phase mole fraction of each component;

[0017] Calculate the gas-phase and liquid-phase compressibility factors in the pressure storage tank before liquid extraction by using the gas-phase and liquid-phase molar volumes of each component in the pressure storage tank before liquid extraction;

[0018] Using the gas-phase and liquid-phase compressibility factors in the pressure storage tank before liquid extraction, the fugacity coefficients of each component in the gas phase and liquid phase in the pressure storage tank before liquid extraction are calculated;

[0019] When gas-liquid equilibrium is reached, the fugacities of each component in the gas phase and liquid phase are 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 values and calculated values of the gas-liquid equilibrium constants of each component. When the accuracy requirements are met, record the calculated values of the gas-liquid equilibrium constants of each component as 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 number of moles of each component in the pressure storage tank before liquid extraction is calculated through the following steps:

[0022] According to the shape and liquid level height of the pressure storage tank, combined with the molar volumes of the gas phase and liquid phase in the pressure storage tank before liquid extraction, the number of moles of the gas phase and liquid phase in the pressure storage tank before liquid extraction are calculated;

[0023] Using the number of moles of the gas phase and liquid phase in the pressure storage tank before liquid extraction, the number of moles of each component in the pressure storage tank before liquid extraction is calculated.

[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] Using the number of moles of each component in the pressure storage tank before liquid extraction, the carbon dioxide gasification rate in the pressure storage tank before liquid extraction is calculated;

[0026] Using the liquid-phase mole fraction of each component, the gas-liquid equilibrium constant of each component, and the carbon dioxide gasification rate in the pressure storage tank before liquid extraction, the mole fraction of each component in the pressure storage tank before liquid extraction is calculated.

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

[0028] Using the gas-liquid equilibrium constant and mole fraction of each component in the pressure storage tank before liquid extraction, the carbon dioxide gasification rate in the pressure storage tank before liquid extraction is calculated;

[0029] Using the carbon dioxide gasification rate, combined with the gas-liquid equilibrium constant and mole fraction of each component in the pressure storage tank before liquid extraction, the liquid-phase mole fraction of each component in the pressure storage tank before liquid extraction is calculated.

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

[0031] Using the number of moles of each component, the liquid-phase mole fraction of each component, and the liquid-phase molar volume in the pressure storage tank before liquid extraction, combined with the liquid extraction volume, the number of moles of each component in the pressure storage tank after liquid extraction is calculated;

[0032] The mole fractions of each component in the pressure storage tank after liquid extraction are calculated 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 fractions of each component in the pressure storage tank after liquid extraction and in combination with the liquid-phase mole fractions of each component 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 present invention, there is also provided a storage medium, which includes a series of instructions for executing the method steps described in any one of the above.

[0036] According to another aspect of the present invention, there is also provided an analysis device for the impurity content of liquid carbon dioxide in a pressure storage tank, which executes the method described in any one of the above. The device includes:

[0037] A gas extraction part, which is arranged at the upper part of the pressure storage tank body and is used to obtain a gaseous carbon dioxide sample from the upper part of the pressure storage tank;

[0038] A liquid discharge part, which is arranged at the bottom of the pressure storage tank body and is used to obtain the liquid carbon dioxide from the bottom of the pressure storage tank;

[0039] A state monitoring part, which is arranged on the pressure storage tank body and is used to measure the pressure, temperature, gas-liquid interface position in the pressure storage tank and the discharge flow rate of the liquid discharge part.

[0040] The present invention provides a method and device for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank. Compared with the prior art, it has the following advantages:

[0041] The present invention constructs a set of analysis devices for the impurity content of liquid carbon dioxide in a pressure storage tank, and proposes an analysis method for the impurity content of liquid CO based on the principles of thermodynamics and mass conservation. 2 Based on the temperature, pressure, gas-liquid interface position in the storage tank, and the flow rate of the liquid discharge pipeline, which are easy to measure, the solubility of different impurities in liquid CO is calculated. 2 in 2 to realize the dynamic analysis of the impurity content of liquid CO in the pressure storage tank, and solve the problems of difficult measurement and low accuracy of the impurity composition of liquid CO in the pressure storage tank, providing a basis for the subsequent research on CO pipeline transportation technology. 2 in 2 in the pressure storage tank.

[0042] Other features and advantages of the present invention will be described in the subsequent specification, and some of them will become obvious from the specification or be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the specification, claims, and drawings. Brief Description of the Drawings

[0043] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0044] Figure 1 A flowchart showing the steps of a method for analyzing the impurity content of 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 the cumulative liquid extraction volume, pressure, and liquid level according to an embodiment of the present invention is shown;

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

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

[0048] In the drawings, the same components are denoted by the same reference numerals. Additionally, the drawings are not drawn to actual scale.

[0049] The meanings of the reference numerals in the drawings are as follows: 1 - pressure storage tank body; 2 - liquid level gauge; 3 - pressure sensor; 4 - multi-point temperature sensor; 5 - gas extraction pipeline; 6 - liquid discharge pipeline; 7 - flow meter; 8 - first valve; 9 - second valve. Detailed Description of the Embodiments

[0050] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the embodiments of the present invention in detail with reference to the drawings.

[0051] The prior art (CN215807871U) discloses a pressure relief device for a liquid carbon dioxide storage tank, which includes a carbon dioxide storage tank, a pressure relief box and a pressure relief component. A pressure relief box is arranged on one side of the carbon dioxide storage tank, and a pressure relief component is arranged inside the pressure relief box. The carbon dioxide storage tank and the pressure relief box are connected by a connecting pipe, and the connecting pipe transmits the excess gas in the carbon dioxide storage tank to the pressure relief box and conducts pressure relief work through the pressure relief component. A pressure relief cavity is opened inside the pressure relief box, a regulating pipe is arranged inside the pressure relief cavity, a gas pressure storage cavity is opened inside the regulating pipe, and exhaust holes are arranged on both sides of the regulating pipe. Through the mutual cooperation of the movable block, the vortex fan, the scroll spring, the fixed block, the slider and the sliding groove, the present utility model, compared with general pressure relief devices, solves the problem that the spring elasticity attenuation will occur in the existing pressure relief devices during long-term operation, and can reduce the impact force of high-pressure gas. However, the above prior art cannot achieve the dynamic analysis of the impurity content in the pressure storage tank, nor can it solve the problems of great difficulty and low precision in measuring the impurity composition in the liquid CO 2 in the pressure storage tank. 2 The prior art (CN217059537U) belongs to the technical field of food processing, and in particular, it is a sampling device for detecting the impurity content of food-grade carbon dioxide. Aiming at the problem of poor sealing effect during sampling and detection of carbon dioxide, the following solution is proposed. It includes a base, a placement seat is fixed at the top of the base, a mounting frame is fixed at the top of the base, an electric push rod is arranged at the top of the mounting frame, a lifting plate is fixed at the output end of the electric push rod, and a mounting box is fixed at the bottom of the lifting plate. In the present utility model, the lifting plate is used to push the pressing plate to squeeze the bottle mouth of the sampling bottle, so that the pressing plate automatically rises under force, and then the hollow probe needle is inserted into the sampling bottle for sampling and detection. The tight fit between the pressing plate and the top of the sampling bottle can ensure the sealing performance during sampling. When the lifting plate descends, it can also drive the clamping and sealing mechanism to seal the periphery of the bottle mouth of the sampling bottle, further improving the airtightness of the device during sampling and detection, and making the detection data more accurate. However, the above prior art cannot achieve the dynamic analysis of the impurity content in the pressure storage tank, nor can it solve the problems of great difficulty and low precision in measuring the impurity composition in the liquid CO

[0052] in the pressure storage tank. 2 in the pressure storage tank. 2 The prior art (CN217059537U) belongs to the technical field of food processing, and in particular, it is a sampling device for detecting the impurity content of food-grade carbon dioxide. Aiming at the problem of poor sealing effect during sampling and detection of carbon dioxide, the following solution is proposed. It includes a base, a placement seat is fixed at the top of the base, a mounting frame is fixed at the top of the base, an electric push rod is arranged at the top of the mounting frame, a lifting plate is fixed at the output end of the electric push rod, and a mounting box is fixed at the bottom of the lifting plate. In the present utility model, the lifting plate is used to push the pressing plate to squeeze the bottle mouth of the sampling bottle, so that the pressing plate automatically rises under force, and then the hollow probe needle is inserted into the sampling bottle for sampling and detection. The tight fit between the pressing plate and the top of the sampling bottle can ensure the sealing performance during sampling. When the lifting plate descends, it can also drive the clamping and sealing mechanism to seal the periphery of the bottle mouth of the sampling bottle, further improving the airtightness of the device during sampling and detection, and making the detection data more accurate. However, the above prior art cannot achieve the dynamic analysis of the impurity content in the pressure storage tank, nor can it solve the problems of great difficulty and low precision in measuring the impurity composition in the liquid CO

[0053] The prior art (CN104713975B) discloses a method for simultaneously detecting the contents of hydrocarbon impurities and nitrogen impurities in hydrogen, which solves the problem that the prior art cannot simultaneously detect the contents of hydrocarbon impurities and nitrogen impurities in hydrogen. By using gas chromatography, under the selected working conditions, two gas samples are simultaneously introduced by an injection valve and enter two channels respectively. One channel is used to analyze hydrocarbon substances, and the other channel is used to analyze the nitrogen content. The chromatographic column is used to separate the samples to be detected, and then the thermal conductivity detector and the hydrogen flame ionization detector are used to simultaneously detect the hydrocarbon impurities and nitrogen content in the samples, and the external standard method is used for calculation. This method is simple and fast to operate. However, the above prior art cannot achieve the dynamic analysis of the impurity content in the pressure storage tank of liquid CO 2 nor can it solve the problems of great difficulty and low accuracy in measuring the impurity composition of liquid CO 2 in the pressure storage tank.

[0054] In CCUS technology, the captured CO 2 is usually stored in a pressure storage tank. When in use, CO 2 is taken out from the liquid discharge hole at the bottom of the storage tank. Impurities have an important impact on the physical properties, phase properties, and pipeline transportation properties of CO 2 , so it is necessary to accurately measure the impurity content of the taken-out CO 2 . However, liquid CO containing impurities 2 has high volatility and it is difficult to directly measure its impurity composition. However, at present, there is no reported analysis method for the impurity content of liquid CO 2 in the pressure storage tank.

[0055] Aiming at the defects of the above prior art, the present invention builds a device for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank, and proposes an analysis method for the impurity content of liquid CO 2 based on the principles of thermodynamics and mass conservation. Based on the easily measurable temperature, pressure, gas-liquid interface position, and liquid discharge pipeline flow rate in the storage tank, the solubility of different impurities in liquid CO 2 is calculated to achieve the dynamic analysis of the impurity content of liquid CO 2 in the pressure storage tank, and solves the problems of great difficulty and low accuracy in measuring the impurity composition of liquid CO 2 in the pressure storage tank, providing a basis for the subsequent research on CO 2 pipeline transportation technology.

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

[0057] As Figure 1As shown, in step S1, before taking out a specific volume of liquid carbon dioxide from the bottom of the pressure storage tank, a gaseous carbon dioxide sample is taken from the upper part of the pressure storage tank to determine the gas-phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before liquid extraction.

[0058] In one embodiment, step S1 includes: analyzing the gaseous carbon dioxide sample by gas chromatography to determine the types and contents of impurities in the gaseous carbon dioxide sample, so as to determine the gas-phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before liquid extraction, where the thermodynamic parameters include: critical temperature, critical pressure, acentric factor, binary interaction coefficient.

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

[0060] In one embodiment, 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 S201 - S207.

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

[0062]

[0063] In the formula, K ie is the estimated gas-liquid equilibrium constant of each component, P ci is the critical pressure of each component, P is the pressure, ω i is the acentric factor of each component, T ci is the critical temperature of each component, T is the temperature, and the subscript i is the component number.

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

[0065]

[0066] In the formula, x i is the liquid-phase mole fraction of each component, y i is the gas-phase mole fraction of each component.

[0067] In step S203, by using the equation of state and combining the binary interaction coefficient and the liquid-phase mole fraction of each component, the gas-phase and liquid-phase molar volumes of each component in the pressure storage tank before liquid extraction are calculated. Specifically, taking the Peng-Robinson equation of state as an example, the gas-phase and liquid-phase molar volumes of each component in the pressure storage tank before liquid extraction are calculated through the following expressions (3)-(9):

[0068]

[0069] Where:

[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 gas-phase or liquid-phase molar volume, k ij is the binary interaction coefficient between component i and component j, T ri is the reduced temperature of component i, n i is the gas-phase or liquid-phase mole fraction of each component, and the subscript j is the component number.

[0077] It should be noted that in addition to using the Peng-Robinson equation of state, other equations of state such as the SRK equation, the BWRS equation, the Span-Wagner equation, and the GERG-2008 equation can also be used to calculate the gas-phase and liquid-phase molar volumes of each component in the pressure storage tank before liquid extraction. The present invention does not limit the selected equation of state.

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

[0079]

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

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

[0082]

[0083] Where:

[0084]

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

[0086] In step S206, when gas-liquid equilibrium is reached, the fugacities of each component in the gas phase and liquid phase are 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 calculated. Specifically, the calculated values of the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are calculated through the following expression (13):

[0087]

[0088] In the formula, K i is the calculated value of the gas-liquid equilibrium constant of each component.

[0089] In step S207, the estimated values and calculated values of the gas-liquid equilibrium constants of each component are compared. When the accuracy requirement is 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, judge the value of |K i -K ie |. If this value is within the accuracy range, then K i is the gas-liquid equilibrium constant of each component in the pressure storage tank before liquid extraction. If this value does not meet the accuracy requirement, then update K ie to K i , and repeat the above steps S201-S206 until the value of |K i -K ie | meets the accuracy requirement, that is, the gas-liquid equilibrium constants of each component in the pressure storage tank before liquid extraction are obtained. In the initial state before liquid extraction, the equilibrium constant of each component is 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 gas-phase molar volume is denoted as V ov , and the liquid-phase molar volume is denoted as V oL .

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

[0091] In step S208, according to the shape and liquid level height of the pressure storage tank, combined with the molar volumes of the gas phase and liquid phase in the pressure storage tank before liquid extraction, the number of moles of the gas phase and liquid phase in the pressure storage tank before liquid extraction is calculated. Specifically, the number of moles of the gas phase and liquid phase in the pressure storage tank before liquid extraction is calculated through the following expressions (14) - (18):

[0092]

[0093]

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

[0095]

[0096] When the liquid level is lower than the radius of the spherical tank, the liquid volume in the tank is:

[0097]

[0098] The gas volume in the tank is:

[0099]

[0100] In the formula, N ovi is the number of moles of the gas phase in the tank in the initial state before liquid extraction, V osv is the gas volume in the tank in the initial state before liquid extraction, N oLi is the number of moles of the liquid phase in the tank in the initial state before liquid extraction, V osL is the liquid volume in the tank in the initial state before liquid extraction, R s is the radius of the spherical tank, h o is the liquid level in the spherical tank in the initial state before liquid extraction.

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

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

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

[0104] In one embodiment, in step S2, the mole fractions of the components in the pressure storage tank before liquid extraction are calculated through the following steps S210 - S211.

[0105] In step S210, the gasification rate of carbon dioxide in the pressure storage tank before liquid extraction is calculated by using the mole numbers of the components in the pressure storage tank before liquid extraction. Specifically, the gasification rate of carbon dioxide in the pressure storage tank before liquid extraction is calculated through the following expression (20):

[0106]

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

[0108] In step S211, the mole fractions of the components in the pressure storage tank before liquid extraction are calculated by using the liquid-phase mole fractions of the components, the gas-liquid equilibrium constants of the components, and the gasification rate of carbon dioxide in the pressure storage tank before liquid extraction. Specifically, the mole fractions of the components in the pressure storage tank before liquid extraction are calculated through the following expression (21):

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

[0110] In the formula, z oi is the mole fraction of each component in the storage tank in the initial state before liquid extraction.

[0111] As Figure 1 shown, in step S3, the liquid-phase mole fractions of the components in the pressure storage tank before liquid extraction are calculated by using the gas-liquid equilibrium constants and the mole fractions of the components in the pressure storage tank before liquid extraction.

[0112] In one embodiment, step S3 includes: calculating the gasification rate of carbon dioxide in the pressure storage tank before liquid extraction by using the gas-liquid equilibrium constants and the mole fractions of the components in the pressure storage tank before liquid extraction; calculating the liquid-phase mole fractions of the components in the pressure storage tank before liquid extraction by using the gasification rate of carbon dioxide in combination with the gas-liquid equilibrium constants and the mole fractions of the components in the pressure storage tank before liquid extraction.

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

[0114]

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

[0116] Specifically, in step S3, the liquid-phase mole fractions of each component in the pressure storage tank before liquid extraction are calculated through the following expressions (23)-(24):

[0117]

[0118]

[0119] where x i is the liquid-phase mole fraction of each component, and y i is the gas-phase mole fraction of each component.

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

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

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

[0123] After taking out a liquid with a volume of dv from the liquid discharge port, the number of moles of each component in the storage tank is:

[0124]

[0125] where N ni is the number of moles of each component in the storage tank after taking out a liquid with a volume of dv in the current state.

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

[0127]

[0128] where z ni is the mole fraction of each component in the storage tank in the current state.

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

[0130] In one embodiment, step S5 includes: determining the impurity content of the liquid carbon dioxide in the pressure storage tank after removing a specific volume of liquid carbon dioxide based on the mole fractions of the components in the pressure storage tank after liquid extraction and in combination with the liquid-phase mole fractions of the components in the pressure storage tank before liquid extraction.

[0131] Specifically, when no liquid is taken out from the liquid discharge port, the mole fractions of the components in the storage tank in the initial state are z oi , and in combination with the pressure and average temperature measured by the storage tank working state monitoring device, the gas-liquid equilibrium constants K of the components in the storage tank are determined i . Through iterative calculation, the gas-liquid equilibrium constants of the components in the storage tank in the current state (denoted as K ni ) are determined, and then the gas-phase mole fraction (denoted as y ni ) and the liquid-phase mole fraction (denoted as x ni ) in the storage tank are obtained, and thus the impurity content of the liquid CO 2 in the current state can be determined. Denote the gas-phase molar volume in the current state as V nv , and the liquid-phase molar volume as V nL .

[0132] Furthermore, when liquid is taken out from the liquid discharge port, it is necessary to recalculate the mole fractions of the components in the storage tank. After determining the mole fractions z ni of each component, according to the calculated liquid-phase mole fraction in the storage tank in the current state, the impurity content of the liquid CO 2 in the storage tank after removing a liquid volume of dv can be determined.

[0133] In one embodiment, taking the current state as the initial state and repeating the above calculation process, the change in the impurity content of the liquid CO 2 during the liquid extraction process of the storage tank can be obtained. Taking the impurity-containing CO 2 with an N 4 mole fraction of 4% and a CH 2 mole fraction of 1% in the initial state as an example, in combination with the monitoring data of temperature, pressure, liquid level, and liquid discharge pipeline flow rate, the relationship curves of the impurity content of the liquid CO 2 with different parameters are plotted, as shown in Figure 2 , Figure 3 .

[0134] A method and device for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank provided by the present invention can also cooperate with a computer-readable storage medium. A computer program is stored on the storage medium, and the computer program is executed to run a method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank. The computer program can run computer instructions, and the computer instructions include computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc.

[0135] A computer-readable storage medium may include: any entity or device capable of carrying computer program code, a recording medium, a USB flash drive, a portable hard disk, a magnetic disk, an optical disc, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0136] It should be noted that the content included in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice within the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electrical carrier signals and telecommunication signals.

[0137] Figure 4 Shows a schematic diagram of an analysis device for the impurity content of liquid carbon dioxide in a pressure storage tank according to an embodiment of the present invention.

[0138] An analysis device for the impurity content of liquid carbon dioxide in a pressure storage tank, which executes an analysis method for the impurity content of liquid carbon dioxide in a pressure storage tank. The device includes: a gas extraction part, a liquid discharge part, and a state monitoring part. Among them, the gas extraction part is arranged at the upper part of the pressure storage tank body 1 and is used to obtain the gaseous carbon dioxide sample at the upper part of the pressure storage tank 1. The liquid discharge part is arranged at the bottom of the pressure storage tank body 1 and is used to obtain the liquid carbon dioxide at the bottom of the pressure storage tank 1. The state monitoring part is arranged on the pressure storage tank body 1 and is used to measure the pressure, temperature, gas-liquid interface position in the pressure storage tank 1, and the discharge flow rate of the liquid discharge part.

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

[0140] In one embodiment, as Figure 1 shown, the liquid discharge part includes a second valve 9 and a liquid discharge pipeline 6 that are sequentially connected to the bottom of the pressure storage tank body 1. Among them, when obtaining the gaseous carbon dioxide sample at the upper part of the pressure storage tank 1, the gas extraction pipeline 5 is connected to the sampling bottle. When in a stable state, the second valve 9 is closed, the first valve 8 is slowly opened. After taking out the gaseous carbon dioxide sample containing impurities, the first valve 8 is closed, and the gaseous carbon dioxide sample is sealed and stored. The pressure, temperature, and gas-liquid interface position in the pressure storage tank body 1 at this time are recorded as the initial state before taking the liquid.

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

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

[0143] In summary, the device includes the pressure storage tank body 1, the liquid level gauge 2, the flow meter 7, the pressure sensor 3, the multi-point temperature sensor 4, the gas extraction pipeline 5, the liquid discharge pipeline 6, the first valve 8, and the second valve 9. Among them, the pressure storage tank body 1 is used to contain liquid CO under pressure 2 , the liquid level gauge 2 is used to monitor the position of the gas-liquid interface inside the storage tank, the flow meter 7 is used to measure the liquid volume of CO taken out from the liquid discharge pipeline 5 2 , 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 extraction pipeline 5 is used to extract the CO gas sample at the top of the storage tank 2 , the liquid discharge pipeline 6 is used to extract the liquid CO at the bottom of the storage tank 2 , and the above device is used to monitor and record the liquid level, liquid extraction volume, pressure, and temperature changes inside the tank.

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

[0145] In summary, the present invention provides an analysis method and device for the impurity content of liquid carbon dioxide in a pressure storage tank. Compared with the prior art, it has the following advantages:

[0146] The present invention builds a set of analysis device for the impurity content of liquid carbon dioxide in a pressure storage tank, and proposes an analysis method for the impurity content of liquid CO based on the principles of thermodynamics and mass conservation. Based on the easily measurable temperature, pressure, gas-liquid interface position, and flow rate of the liquid discharge pipeline inside the storage tank, it calculates the solubility of different impurities in liquid CO 2 , realizes the dynamic analysis of the impurity content of liquid CO in the pressure storage tank, solves the problems of difficult measurement and low accuracy of the impurity composition of liquid CO in the pressure storage tank, and provides a basis for the subsequent research on CO pipeline transportation technology. 2 2 2 2

[0147] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and do not imply limitation.

[0148] In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0149] In the description of the present invention, it should be noted that, unless otherwise clearly specified and defined, the terms "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0150] Certain terms are used throughout this application document to refer to specific system components. As those skilled in the art will recognize, the same components may generally be referred to by different names, and thus this application document is not intended to distinguish components that differ only in name and not in function. In this application document, the terms "comprise", "include" and "have" are used in an open-ended fashion and should therefore be interpreted to mean "including but not limited to...". In addition, the terms "substantially", "essentially" or "approximately" as may be used herein relate to the industry-accepted tolerances for the corresponding terms. As the term "coupled" as may be used herein includes direct coupling and indirect coupling via additional components, elements, circuits, or modules, where for indirect coupling, the intervening components, elements, circuits, or modules do not change the information of the signal but may adjust its current level, voltage level, and / or power level. Inferred coupling (e.g., where one element is coupled to another element by inference) includes direct and indirect coupling between the two elements in the same manner as "coupled".

[0151] As used herein, the term "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the phrases "one embodiment" or "an embodiment" that appear throughout the specification do not necessarily refer to the same embodiment.

[0152] The embodiments of the present invention are provided for purposes of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations are obvious to those of ordinary skill in the art. The embodiments are chosen and described in order to best explain the principles of the invention and its practical application, and to enable those of ordinary skill in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

[0153] Although the embodiments disclosed in the present invention are as described above, the above content is only an embodiment adopted for the convenience of understanding the present invention, and is not intended to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains may make any modifications and variations in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A method for analyzing the impurity content of 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 storage tank, obtaining a gaseous carbon dioxide sample from the upper part of the pressure storage tank to determine the gas-phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before liquid extraction; S2. Based on the gas-phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before liquid extraction, calculating the gas-liquid equilibrium constant, the number of moles of each component, and the mole fraction of each component in the pressure storage tank before liquid extraction; S3. Through the gas-liquid equilibrium constant and the mole fraction of each component in the pressure storage tank before liquid extraction, calculating the liquid-phase mole fraction of each component in the pressure storage tank before liquid extraction; S4. After taking out a specific volume of liquid carbon dioxide from the bottom of the pressure storage tank, calculating the mole fraction of each component in the pressure storage tank after liquid extraction according to the number of moles of each component and the liquid-phase mole fraction of each component in the pressure storage tank before liquid extraction; S5. Based on the mole fraction of each component in the pressure storage tank after liquid extraction, determining the impurity content of the liquid carbon dioxide in the pressure storage tank after taking out a specific volume of liquid carbon dioxide.

2. A method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank according to claim 1, characterized in that, step S1 includes: analyzing the gaseous carbon dioxide sample by gas chromatography to determine the type and content of impurities in the gaseous carbon dioxide sample, so as to determine the gas-phase mole fraction and thermodynamic parameters of each component in the pressure storage tank before liquid extraction, wherein the thermodynamic parameters include: critical temperature, critical pressure, acentric factor, binary interaction coefficient.

3. A method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank according to claim 2, characterized in that, in step S2, the gas-liquid equilibrium constant of each component in the pressure storage tank before liquid extraction is calculated through the following steps: estimating the estimated value of the gas-liquid equilibrium constant of each component in the pressure storage tank before liquid extraction by using the critical temperature, the critical pressure, and the acentric factor; calculating the liquid-phase mole fraction of each component in the pressure storage tank before liquid extraction by using the gas-phase mole fraction of each component in the pressure storage tank before liquid extraction; calculating the gas-phase and liquid-phase molar volumes of each component in the pressure storage tank before liquid extraction through the equation of state, combining the binary interaction coefficient and the liquid-phase mole fraction of each component; calculating the gas-phase and liquid-phase compressibility factors in the pressure storage tank before liquid extraction by using the gas-phase and liquid-phase molar volumes of each component in the pressure storage tank before liquid extraction; calculating the fugacity coefficients of the gas phase and liquid phase of each component in the pressure storage tank before liquid extraction by using the gas-phase and liquid-phase compressibility factors in the pressure storage tank before liquid extraction; when reaching gas-liquid equilibrium, the fugacities of the gas phase and liquid phase of each component are equal, and accordingly, the calculated value of the gas-liquid equilibrium constant of each component in the pressure storage tank before liquid extraction is calculated; comparing the estimated value and the calculated value of the gas-liquid equilibrium constant of each component, and when the accuracy requirement is met, recording the calculated value of the gas-liquid equilibrium constant of each component as the gas-liquid equilibrium constant of each component in the pressure storage tank before liquid extraction.

4. A method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank according to claim 3, characterized in that, in step S2, the number of moles of each component in the pressure storage tank before liquid extraction is calculated through the following steps: According to the shape of the pressure storage tank and the liquid level height, combined with the molar volumes of the gas phase and liquid phase in the pressure storage tank before liquid extraction, the molar numbers of the gas phase and liquid phase in the pressure storage tank before liquid extraction are calculated; Using the molar numbers of the gas phase and liquid phase in the pressure storage tank before liquid extraction, the molar numbers of each component in the pressure storage tank before liquid extraction are calculated.

5. A method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank according to claim 3 or 4, characterized in that, In step S2, the molar fractions of each component in the pressure storage tank before liquid extraction are calculated through the following steps: Using the molar numbers of each component in the pressure storage tank before liquid extraction, the carbon dioxide gasification rate in the pressure storage tank before liquid extraction is calculated; Using the liquid-phase molar fractions of each component, the gas-liquid equilibrium constants of each component, and the carbon dioxide gasification rate in the pressure storage tank before liquid extraction, the molar fractions of each component in the pressure storage tank before liquid extraction are calculated.

6. A method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank according to any one of claims 1-5, characterized in that, Step S3 includes: Using the gas-liquid equilibrium constants and molar fractions of each component in the pressure storage tank before liquid extraction, the carbon dioxide gasification rate in the pressure storage tank before liquid extraction is calculated; Using the carbon dioxide gasification rate, combined with the gas-liquid equilibrium constants and molar fractions of each component in the pressure storage tank before liquid extraction, the liquid-phase molar fractions of each component in the pressure storage tank before liquid extraction are calculated.

7. A method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank according to any one of claims 3-6, characterized in that, Step S4 includes: Using the molar numbers, liquid-phase molar fractions, and liquid molar volume of each component in the pressure storage tank before liquid extraction, combined with the liquid extraction volume, the molar numbers of each component in the pressure storage tank after liquid extraction are calculated; Using the molar numbers of each component in the pressure storage tank after liquid extraction, the molar fractions of each component in the pressure storage tank after liquid extraction are calculated.

8. A method for analyzing the impurity content of liquid carbon dioxide in a pressure storage tank according to any one of claims 1-7, characterized in that, Step S5 includes: Based on the molar fractions of each component in the pressure storage tank after liquid extraction, combined with the liquid-phase molar fractions of each component 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.

9. A storage medium, characterized in that, it includes a series of instructions for executing the method steps according to any one of claims 1-8.

10. An analysis device for the impurity content of liquid carbon dioxide in a pressure storage tank, characterized in that, executing the method according to any one of claims 1-8, and the device includes: A gas extraction part, which is arranged at the upper part of the pressure storage tank body and is used to obtain a gaseous carbon dioxide sample from the upper part of the pressure storage tank; A liquid discharge part, which is arranged at the bottom of the pressure storage tank body and is used to obtain the liquid carbon dioxide at the bottom of the pressure storage tank; A state monitoring part, which is arranged on the pressure storage tank body and is used to measure the pressure, temperature, gas-liquid interface position in the pressure storage tank, and the discharge flow rate of the liquid discharge part.

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