Method and apparatus for determining near-critical region of impurity-containing carbon dioxide transported via pipeline

Abstract

A method for determining a near-critical region of impurity-containing carbon dioxide transported via a pipeline, comprising: on the basis of the composition of impurity-containing carbon dioxide transported via a pipeline, calculating the critical temperature and critical pressure of the impurity-containing carbon dioxide, and on the basis of the maximum working temperature and maximum working pressure of the pipeline, determining a supercritical pipeline transportation temperature range and a supercritical pipeline transportation pressure range; within the supercritical pipeline transportation temperature range and the supercritical pipeline transportation pressure range, calculating the physical property parameters of the impurity-containing carbon dioxide; respectively determining the temperature range of drastic change of the physical property parameters under a constant pressure condition and the pressure range of drastic change of the physical property parameters under a constant temperature condition, and recording the temperature range and the pressure range as a first range and a second range; and on the basis of the first range and the second range, obtaining a near-critical region corresponding to the impurity-containing carbon dioxide transported via the pipeline.

Description

A method and device for determining the quasi-critical zone of pipeline-transported impurity-containing carbon dioxide

[0001] Cross-references to related art

[0002] This application claims priority to Chinese patent application No. 202311705043.5 filed on December 12, 2023, entitled “A method and device for determining the quasi-critical zone of pipeline-transported impurities-containing carbon dioxide,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of carbon storage science and engineering technology, and is applied to determining the quasi-critical zone of pipeline-transported carbon dioxide in carbon capture, utilization and storage, and relates to a method and device for determining the quasi-critical zone of pipeline-transported carbon dioxide containing impurities. Background Art

[0004] Pipeline transportation is the primary method for transporting CO2 in future carbon capture, utilization, and storage (CCUS) projects. Supercritical transportation technology offers the highest efficiency and lowest cost, and holds promising market prospects. Supercritical transportation technology places extremely high demands on pipeline temperature and pressure control. Even small fluctuations in temperature and pressure under supercritical conditions can cause dramatic changes in CO2 properties, such as density, viscosity, thermal conductivity, and specific heat capacity, thereby impacting safe and stable pipeline operation. The temperature and pressure range corresponding to dramatic changes in CO2 properties is typically referred to as the quasi-critical region. Clarifying the extent of this region is crucial for pipeline safety control.

[0005] Affected by the process technology level and purification cost, pipeline CO2 usually contains a certain amount of impurities, which causes the physical properties and phase characteristics of CO2 to shift, and the range of the quasi-critical zone also changes accordingly, increasing the difficulty of controlling supercritical CO2 pipeline transportation. At present, there is no mature method to quickly and accurately delineate the range of the quasi-critical zone of pipeline CO2 containing impurities.

[0006] In response to the problems of the prior art, the present invention provides a method and device for determining the quasi-critical zone of pipeline-transported impurity-containing carbon dioxide. Summary of the Invention

[0007] In order to accurately define the quasi-critical region of different types of impure CO2, the present invention provides a method for determining the quasi-critical region of pipeline-transported impure CO2, the method comprising:

[0008] Based on the composition of the impure carbon dioxide transported in pipelines, calculate the critical temperature and critical pressure of the impure carbon dioxide, and combine them with the maximum operating temperature and maximum operating pressure of the pipeline to determine the supercritical pipeline transmission temperature and pressure range;

[0009] Calculating the physical properties of carbon dioxide containing impurities within the supercritical pipeline temperature and pressure range;

[0010] Determine the temperature range in which the physical property parameters change dramatically under a constant pressure condition and the pressure range in which the physical property parameters change dramatically under a constant temperature condition, and record them as a first range and a second range;

[0011] According to the first range and the second range, a quasi-critical region corresponding to pipeline-transported impurity-containing carbon dioxide is obtained.

[0012] According to one embodiment of the present invention, the first range and the second range are determined by the following steps:

[0013] The numerical gradient components of each point in different directions on the three-dimensional curved surface of the physical property parameters of the impure carbon dioxide are calculated to obtain the first range and the second range.

[0014] According to one embodiment of the present invention, the three-dimensional surface is obtained by the following steps:

[0015] The three-dimensional surface of the physical property parameters of impure carbon dioxide is constructed with temperature as the X-axis, pressure as the Y-axis, and physical property parameters as the Z-axis.

[0016] According to one embodiment of the present invention, the first range is obtained by the following steps:

[0017] Calculating the numerical gradient component of each point on the three-dimensional surface in the X direction, and recording the calculation result as the first matrix corresponding to the physical property parameters;

[0018] In the first matrix, elements with a value smaller than a first threshold are screened, and the first range is obtained according to the temperature and pressure corresponding to the elements.

[0019] According to one embodiment of the present invention, the first threshold is determined by the following steps:

[0020] averaging the elements in the first matrix to obtain a first average value of the degree of change of the physical property parameter with temperature;

[0021] Set the temperature threshold correction factor based on the pipeline's operating conditions and design specifications;

[0022] The product of the temperature threshold correction coefficient and the first average value is calculated as the first threshold value of the degree of change of the physical property parameter with temperature.

[0023] According to one embodiment of the present invention, the second range is determined by the following steps:

[0024] Calculating the numerical gradient component of each point on the three-dimensional surface in the Y direction, and recording the calculation result as a second matrix corresponding to the physical property parameters;

[0025] In the second matrix, elements greater than a second threshold are screened, and the second range is obtained according to the temperature and pressure corresponding to the elements.

[0026] According to one embodiment of the present invention, the second threshold is determined by the following steps:

[0027] averaging the elements in the second matrix to obtain a second average value of the degree of change of the physical property parameter with pressure;

[0028] Set the pressure threshold correction factor based on the pipeline's operating conditions and design specifications;

[0029] The product of the pressure threshold correction coefficient and the second average value is calculated as the second threshold value of the degree of change of the physical parameter with pressure.

[0030] According to one embodiment of the present invention, the critical temperature and the critical pressure are calculated by the following steps:

[0031] Taking pipeline carbon dioxide as a sample, testing the composition of the sample, and determining the mole fraction and thermodynamic parameters of each component;

[0032] The critical temperature and the critical pressure are calculated based on the mole fraction of each component and the thermodynamic parameters.

[0033] According to one embodiment of the present invention, the physical property parameters of carbon dioxide containing impurities are calculated by the following steps:

[0034] According to the composition of the sample, a variety of state equations are used to calculate the theoretical results corresponding to the physical property parameters;

[0035] Measure the physical properties of pipeline-transported carbon dioxide containing impurities and obtain the corresponding measured results;

[0036] The mean square error between the measured result and each of the theoretical results is calculated, and the physical property parameters of the impure carbon dioxide are calculated using the state equation corresponding to the theoretical result with the smallest mean square error.

[0037] According to one embodiment of the present invention, the supercritical pipeline transmission temperature and pressure range is determined by the following steps:

[0038] Taking the critical temperature as the lower temperature limit and the maximum operating temperature as the upper temperature limit, combined with the temperature step, the supercritical pipeline temperature range is obtained;

[0039] Taking the critical pressure as the lower pressure limit and the maximum working pressure as the upper pressure limit, combined with the pressure step length, the supercritical pipeline pressure range is obtained;

[0040] The supercritical pipeline transportation temperature and pressure range is obtained based on the supercritical pipeline transportation temperature range and the supercritical pipeline transportation pressure range.

[0041] According to one embodiment of the present invention, the physical property parameters include any one of density, expansion coefficient, compressibility, dynamic viscosity, thermal conductivity, and specific heat capacity, or a combination thereof.

[0042] According to one embodiment of the present invention, the density of impure carbon dioxide within the supercritical pipeline temperature and pressure range is calculated by the following steps:

[0043] Step a, calculating the compressibility factor of the impure carbon dioxide using the critical temperature as the initial temperature and the critical pressure as the initial pressure;

[0044] Step b, calculating the average relative molecular mass of the impure carbon dioxide based on the relative molecular mass of each component of the impure carbon dioxide and the mole fraction of each component;

[0045] Step c, calculating the density of the impure carbon dioxide based on the average relative molecular mass and the compressibility factor of the impure carbon dioxide;

[0046] Step d: Repeat steps a to c within the supercritical pipeline temperature and pressure range to obtain the density of impurity-containing carbon dioxide within the supercritical pipeline temperature and pressure range.

[0047] According to one embodiment of the present invention, the quasi-critical region is obtained by the following steps:

[0048] The union of the first range and the second range is taken as the quasi-critical region for pipeline transportation of impurity-containing carbon dioxide.

[0049] According to one embodiment of the present invention, the method comprises:

[0050] Calculate the critical temperature and critical pressure of the impure carbon dioxide according to the composition of the pipeline-transported impure carbon dioxide;

[0051] Determine the supercritical pipeline transmission temperature and pressure range by using the critical temperature and the critical pressure in combination with the maximum operating temperature and pressure of the pipeline, and calculate the physical property parameters of the impure carbon dioxide within the supercritical pipeline transmission temperature and pressure range;

[0052] Within the supercritical pipeline temperature and pressure range, combined with the physical properties of the impurity-containing carbon dioxide, determine the temperature range in which the physical properties change dramatically under constant pressure conditions, and record it as the first range;

[0053] Within the supercritical pipeline transmission temperature and pressure range, combined with the physical properties of the impurity-containing carbon dioxide, determine the pressure range where the physical properties change dramatically under constant temperature conditions, and record it as the second range;

[0054] The first range and the second range are combined to obtain a quasi-critical region for pipeline transportation of impurity-containing carbon dioxide.

[0055] According to one embodiment of the present invention, the physical property parameters include but are not limited to: density, dynamic viscosity, and thermal conductivity. The density of impure carbon dioxide within the supercritical pipeline temperature and pressure range is calculated by the following steps:

[0056] Step a, calculating the compressibility factor of the impure carbon dioxide using the critical temperature as the initial temperature and the critical pressure as the initial pressure;

[0057] Step b, calculating the average relative molecular mass of the impure carbon dioxide based on the relative molecular mass of each component of the impure carbon dioxide and the mole fraction of each component;

[0058] Step c, calculating the density of the impure carbon dioxide based on the average relative molecular mass and the compressibility factor of the impure carbon dioxide;

[0059] Step d: Set the temperature step and the pressure step to determine the supercritical pipeline temperature and pressure range. Repeat steps a to c within the supercritical pipeline temperature and pressure range to obtain the density of impure carbon dioxide within the supercritical pipeline temperature and pressure range.

[0060] According to one embodiment of the present invention, in step b, the average relative molecular mass of the impurity-containing carbon dioxide is calculated by the following expression:

[0061] Where, M is the average relative molecular mass of impurity carbon dioxide; i is the mole fraction of the i-th component; M i is the relative molecular mass of the i-th component;

[0062] In step c, the density of impure carbon dioxide is calculated by the following expression:

[0063] Wherein, ρ is the density of impure carbon dioxide; M is the average relative molecular mass of impure carbon dioxide; P is the pressure; Z is the compressibility factor of impure carbon dioxide; R is the molar gas constant; and T is the temperature.

[0064] According to one embodiment of the present invention, the temperature range in which the physical property parameters change dramatically under a constant pressure condition is determined by the following steps:

[0065] Constructing a three-dimensional surface of the physical property parameters of impure carbon dioxide with temperature as the X-axis, pressure as the Y-axis, and physical property parameters as the Z-axis, the temperature step as the X-axis spacing, and the pressure step as the Y-axis spacing;

[0066] Calculating the numerical gradient component of each point on the three-dimensional surface in the X direction with the temperature step length as the interval, and recording the calculation result as the first matrix of each physical property parameter;

[0067] averaging the elements in the first matrix to obtain an average value of the degree of change of the physical property parameter with temperature, and combining the average value with the temperature threshold correction coefficient to obtain a first threshold value of the degree of change of the physical property parameter with temperature;

[0068] In the first matrix, elements whose values ​​are smaller than the first threshold are screened, and the temperature range in which the physical properties change dramatically under constant pressure conditions is determined based on the temperature and pressure corresponding to the elements.

[0069] According to one embodiment of the present invention, the pressure range in which the physical property parameters change dramatically under a constant temperature condition is determined by the following steps:

[0070] Calculate the numerical gradient component of each point on the three-dimensional surface in the Y direction with the pressure step length as the spacing, and record the calculation result as the second matrix of each physical property parameter;

[0071] averaging the elements in the second matrix to obtain an average value of the degree of change of the physical property parameter with pressure, and combining the average value with the pressure threshold correction coefficient to obtain a second threshold value of the degree of change of the physical property parameter with pressure;

[0072] In the second matrix, elements greater than the second threshold are screened, and the pressure range in which the physical property parameters change dramatically under a constant temperature condition is determined based on the temperature and pressure corresponding to the elements.

[0073] According to one embodiment of the present invention, the first threshold value of the degree of change of the physical property parameter with temperature is obtained by the following expression: S T =n T F Ta

[0074] Where S T is the first threshold; n T is the temperature threshold correction coefficient; F Ta is the average value of the degree of change of physical parameters with temperature, that is, the average value of the first matrix;

[0075] The second threshold value of the variation of the physical property parameter with pressure is obtained by the following expression: S P =n P F Pa

[0076] Where S P is the second threshold; n P is the pressure threshold correction coefficient; F Pa is the average value of the degree of change of the physical parameters with pressure, that is, the average value of the second matrix.

[0077] According to one embodiment of the present invention, the quasi-critical region of pipeline-transported carbon dioxide containing impurities is obtained by the following steps: fusing the first range and the second range of required physical property parameters to obtain the quasi-critical region of pipeline-transported carbon dioxide containing impurities.

[0078] According to another aspect of the present invention, a storage medium is provided, which contains a series of instructions for executing the method steps described in any one of the above.

[0079] According to another aspect of the present invention, there is provided a device for determining a quasi-critical zone of pipeline-transported impurity-containing carbon dioxide, configured to execute any of the above methods, the device comprising:

[0080] A critical temperature and pressure calculation module, which is used to calculate the critical temperature and critical pressure of the impure carbon dioxide based on the composition of the pipeline-transported impurity-containing carbon dioxide;

[0081] a physical property parameter calculation module connected to the critical temperature and pressure calculation module, configured to determine the supercritical pipeline transmission temperature and pressure range based on the critical temperature and critical pressure, in combination with the maximum operating temperature and maximum operating pressure of the pipeline, and calculate the physical property parameters of the impure carbon dioxide within the supercritical pipeline transmission temperature and pressure range;

[0082] a range demarcation module connected to the physical property parameter calculation module, configured to perform the following steps: determining, within the supercritical pipeline transmission temperature and pressure range, a temperature range in which the physical property parameter changes dramatically under a constant pressure condition, and recording the range as the first range; determining, within the supercritical pipeline transmission temperature and pressure range, a pressure range in which the physical property parameter changes dramatically under a constant temperature condition, and recording the range as the second range;

[0083] A quasi-critical region determination module is connected to the range delineation module and is used to obtain the quasi-critical region corresponding to the pipeline-transported impurity-containing carbon dioxide according to the first range and the second range.

[0084] The present invention provides a method and device for determining the quasi-critical zone of pipeline-transported impurity-containing carbon dioxide, which has the following advantages over the prior art:

[0085] The present invention proposes a method and apparatus for determining the quasi-critical zone of pipeline-transported impure carbon dioxide. The method first tests the impurity composition of the pipeline-transported CO2, then calculates the physical properties of the CO2 within the supercritical pipeline temperature and pressure range using an equation of state. The method then divides the temperature range within which the physical properties change dramatically at a constant pressure into the pressure range within which the physical properties change dramatically at a constant temperature. The two division results are then combined to determine the quasi-critical zone of the impure CO2. The method considers the effect of pressure at a constant temperature on the physical properties of CO2, based on the quasi-critical temperature. Furthermore, the method uses the gradient of the physical property parameters as a threshold to define the temperature and pressure ranges, thereby narrowing the scope of the quasi-critical zone and providing a more accurate division of the quasi-critical zone of the impure CO2. This method can provide a basis for the safe control of supercritical CO2 pipeline transportation.

[0086] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0088] FIG1A shows a flowchart of a method for determining a quasi-critical zone of pipeline-transported impurity-containing carbon dioxide according to one embodiment of the present invention;

[0089] FIG1B shows a flowchart of a method for determining a quasi-critical zone for pipeline transportation of impurities-containing carbon dioxide according to another embodiment of the present invention;

[0090] FIG2 shows a three-dimensional curved surface diagram of the density of impurity-containing carbon dioxide according to one embodiment of the present invention;

[0091] FIG3 shows a schematic diagram of a first range in a pressure-temperature coordinate diagram according to an embodiment of the present invention;

[0092] FIG4 shows a schematic diagram of a second range in a pressure-temperature coordinate diagram according to an embodiment of the present invention;

[0093] FIG5 shows a schematic diagram of a quasi-critical region for pipeline transportation of impurity-containing carbon dioxide according to an embodiment of the present invention.

[0094] In the accompanying drawings, the same reference numerals are used for the same parts. In addition, the accompanying drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0095] To make the objectives, technical solutions and advantages of the present invention more clear, embodiments of the present invention are described in further detail below with reference to the accompanying drawings.

[0096] The prior art (CN211513994U) relates to a system for purifying impure carbon dioxide acid gas. The purification system includes a carbon dioxide acid gas absorption device, a spray agitator, a constant pressure container, and a molecular sieve adsorption and filtration device. The first input end of the carbon dioxide acid gas absorption device is connected to an associated gas pipeline containing carbon dioxide, and the output end of the carbon dioxide acid gas absorption device is connected to the spray agitator. The absorbed impurity-containing carbon dioxide acid gas is transported to the spray agitator to generate hydrate slurry and methane gas. The spray agitator is connected to the constant pressure container and the hydrate slurry is transported to the constant pressure container for gasification. The constant pressure container is connected to the molecular sieve adsorption and filtration device and the gasification product is transported to the molecular sieve adsorption and filtration device for adsorption and filtration to obtain pure carbon dioxide dry gas.

[0097] The prior art (CN216512855U) discloses a device for high-value and efficient conversion and utilization of carbon dioxide using solar energy, comprising a carbon dioxide capture and purification system, a catalytic reaction system and a product separation system. The carbon dioxide capture and purification system, the catalytic reaction system and the product separation system are connected in sequence. The exhaust gas is first purified by the carbon dioxide capture and purification system and then transported to the catalytic reaction system for catalytic reaction. The gas after the reaction enters the product separation system to separate the synthesis gas in the mixed gas, and the unreacted raw gas is recycled to the catalytic reaction system to continue to participate in the reaction. At the same time, the methane / carbon dioxide intake ratio is dynamically adjusted to improve the methane / carbon dioxide conversion rate. The new device also provides a photovoltaic power generation subsystem, which supplies power to the entire device and system, realizing complete self-sufficiency of the system, achieving efficient utilization of solar energy while achieving negative carbon emissions, and realizing high-value and efficient conversion and utilization of carbon dioxide using solar energy.

[0098] Prior art (CN101231131B) uses a mass transfer separation column system to remove a first impurity selected from oxygen and carbon monoxide from impure liquid carbon dioxide, which is then reboiled via indirect heat exchange with a crude carbon dioxide stream, where the impure liquid carbon dioxide has a higher concentration than the crude carbon dioxide stream. The present invention is particularly suitable for recovering carbon dioxide from flue gases generated by oxyfuel combustion processes or waste gases from hydrogen PSA processes. It has the advantage of reducing the content of the first impurity to no more than 1000 ppm.

[0099] However, none of these existing technologies can quickly and accurately define the quasi-critical zone for pipeline transport of impure CO2. During supercritical CO2 pipeline transportation, even small fluctuations in temperature and pressure can lead to dramatic changes in CO2 properties. Determining the quasi-critical zone, where the most dramatic property changes occur, is essential to ensuring safe and stable pipeline operation.

[0100] In the prior art, the method for determining the quasi-critical region of pure CO2 is to divide the area where the physical properties of CO2 change most dramatically in the PT coordinate diagram, with the CO2 critical pressure (7.38MPa) and the quasi-critical temperature line (a curve connecting the quasi-critical temperatures of CO2 at different pressures) as the center. The quasi-critical region delineated by this method is relatively large, and in practice, pipeline CO2 contains a variety of impurities, which causes the range of the CO2 quasi-critical region to shift. Therefore, the method for determining the quasi-critical region of pure CO2 is not suitable for pipeline CO2 containing impurities. Currently, there is no report on the method for determining the quasi-critical region of pipeline CO2 containing impurities. In addition, the existing CO2 quasi-critical region division method is mainly used for the study of supercritical fluid heat transfer characteristics. For pipeline transportation, its range is too broad, covering almost all pipeline operating conditions, making it difficult to cope with in actual operation.

[0101] In order to solve the problems of the current existing technology, the present invention aims to provide a method and device for determining the quasi-critical zone of pipeline-transported impure carbon dioxide, which can accurately delineate the range of the quasi-critical zone of different types of impure CO2, thereby preventing pipeline conditions from entering this area and causing unstable flow of the fluid, and providing a theoretical reference for the formulation of supercritical CO2 pipeline transportation safety control plan.

[0102] FIG1A shows a flowchart of the steps of a method for determining a quasi-critical zone of pipeline-transported impurity-containing carbon dioxide according to an embodiment of the present invention.

[0103] As shown in FIG1A , in step S1 , the critical temperature and critical pressure of the impure carbon dioxide are calculated based on the composition of the pipeline-transmitted impurity-containing carbon dioxide, and the supercritical pipeline temperature and pressure range is determined in combination with the maximum operating temperature and maximum operating pressure of the pipeline.

[0104] As shown in FIG1A , in step S2 , the physical properties of the impure carbon dioxide are calculated within the supercritical pipeline temperature and pressure range.

[0105] As shown in FIG1A , in step S3 , the temperature range in which the physical property parameter changes drastically under a constant pressure condition and the pressure range in which the physical property parameter changes drastically under a constant temperature condition are determined respectively, and recorded as a first range and a second range.

[0106] As shown in FIG1A , in step S4 , a quasi-critical region corresponding to pipeline-transported impurity-containing carbon dioxide is obtained based on the first range and the second range.

[0107] In one embodiment, the first range and the second range are determined by the following steps: calculating the numerical gradient components of each point in different directions on the three-dimensional surface of the physical property parameters of the impure carbon dioxide to obtain the first range and the second range.

[0108] In one embodiment, a three-dimensional surface is obtained by the following steps: a three-dimensional surface of the physical property parameters of impure carbon dioxide is constructed with temperature as the X-axis, pressure as the Y-axis, and physical property parameters as the Z-axis.

[0109] In one embodiment, the first range (the temperature range in which the physical property parameters change dramatically under constant pressure conditions) is obtained by the following steps: calculating the numerical gradient component of each point in the X direction on the three-dimensional surface, and recording the calculation results as the first matrix corresponding to the physical property parameters; in the first matrix, screening elements less than a first threshold, and obtaining the first range based on the temperature and pressure corresponding to the elements.

[0110] It should be noted that the present invention can capture the drastic changes in physical parameters under constant pressure conditions by screening elements smaller than the first threshold value in the first matrix.

[0111] In one embodiment, the first threshold is determined by the following steps: averaging the elements in the first matrix to obtain a first average value of the degree of change of the physical property parameter with temperature; setting a temperature threshold correction coefficient based on the operating conditions and design specifications of the pipeline; and calculating the product of the temperature threshold correction coefficient and the first average value as the first threshold of the degree of change of the physical property parameter with temperature.

[0112] In one embodiment, the second range (the pressure range in which the physical property parameters change dramatically under constant temperature conditions) is determined by the following steps: calculating the numerical gradient component in the Y direction of each point on the three-dimensional surface, and recording the calculation results as a second matrix corresponding to the physical property parameters; in the second matrix, screening elements greater than a second threshold, and obtaining the second range based on the temperature and pressure corresponding to the elements.

[0113] It should be noted that the present invention can capture the drastic changes of physical parameters under constant temperature conditions by screening elements with a value greater than the second threshold in the second matrix.

[0114] In one embodiment, the second threshold is determined by the following steps: averaging the elements in the second matrix to obtain a second average value of the degree of change of the physical parameter with pressure; setting a pressure threshold correction coefficient based on the operating conditions and design specifications of the pipeline; and calculating the product of the pressure threshold correction coefficient and the second average value as the second threshold of the degree of change of the physical parameter with pressure.

[0115] In one embodiment, the critical temperature and the critical pressure are calculated by the following steps: taking pipeline carbon dioxide as a sample, testing the composition of the sample, and determining the mole fraction and thermodynamic parameters of each component; and calculating the critical temperature and the critical pressure based on the mole fraction and thermodynamic parameters of each component.

[0116] In one embodiment, the physical property parameters of the impure carbon dioxide are calculated by the following steps: based on the composition of the sample, multiple state equations are used to calculate and obtain theoretical results corresponding to the physical property parameters; the physical property parameters of the pipeline-transported impure carbon dioxide are measured to obtain measured results corresponding to the physical property parameters; the mean square error between the measured results and each theoretical result is calculated, and the physical property parameters of the impure carbon dioxide are calculated using the state equation corresponding to the theoretical result with the smallest mean square error.

[0117] In one embodiment, the supercritical pipeline temperature and pressure range is determined by the following steps: taking the critical temperature as the lower temperature limit, the maximum operating temperature as the upper temperature limit, and combining the temperature step to obtain the supercritical pipeline temperature range; taking the critical pressure as the lower pressure limit, the maximum operating pressure as the upper pressure limit, and combining the pressure step to obtain the supercritical pipeline pressure range; based on the supercritical pipeline temperature range and the supercritical pipeline pressure range, the supercritical pipeline temperature and pressure range is obtained.

[0118] In one embodiment, the physical property parameter includes any one of density, expansion coefficient, compressibility, dynamic viscosity, thermal conductivity, and specific heat capacity, or a combination thereof.

[0119] In one embodiment, the density of impure carbon dioxide within the supercritical pipeline temperature and pressure range is calculated by the following steps: step a, calculating the compressibility factor of the impure carbon dioxide with the critical temperature as the initial temperature and the critical pressure as the initial pressure; step b, calculating the average relative molecular mass of the impure carbon dioxide based on the relative molecular mass of each component of the impure carbon dioxide and the mole fraction of each component; step c, calculating the density of the impure carbon dioxide based on the average relative molecular mass and the compressibility factor of the impure carbon dioxide; step d, repeating steps a to c within the supercritical pipeline temperature and pressure range to obtain the density of the impure carbon dioxide within the supercritical pipeline temperature and pressure range.

[0120] In one embodiment, the quasi-critical region is obtained by the following steps: taking the union of the first range and the second range as the quasi-critical region for pipeline transport of impurity-containing carbon dioxide.

[0121] This paper introduces impurity effect analysis to comprehensively describe the changes in carbon dioxide's physical properties. Specifically, traditional methods for delineating the carbon dioxide quasi-critical region ignore the presence of impurities, which actually have a significant impact on carbon dioxide's physical properties. This paper innovatively considers the impact of impurities on the carbon dioxide quasi-critical region, making the delineation results more realistic.

[0122] This paper employs a dual-variable fusion strategy to further enhance the accuracy and adaptability of the delineation. Specifically, by simultaneously considering temperature and pressure variations (i.e., the variation of carbon dioxide properties with temperature at constant pressure and with pressure at constant temperature), it overcomes the limitations of traditional single-variable analysis methods and more accurately defines the quasi-critical zone for impure carbon dioxide.

[0123] This invention considers pipe material properties and related support and reinforcement measures, enhancing guidance for engineering applications. Specifically, the traditional CO2 quasi-critical zone demarcation method is based on a fixed temperature and pressure range and does not account for pipeline differences. This invention considers pipe material properties (affecting the maximum operating temperature and pressure of the pipeline) as well as operating conditions and design specifications (affecting the temperature threshold correction factor and pressure threshold correction factor of the pipeline), making it more practical and providing more targeted guidance for engineering applications.

[0124] FIG1B shows a flowchart of a method for determining a quasi-critical zone of pipeline-transported impurity-containing carbon dioxide according to another embodiment of the present invention.

[0125] As shown in FIG. 1B , in step S101 , the critical temperature and critical pressure of the impurity-containing carbon dioxide are calculated according to the composition of the pipeline-transmitted impurity-containing carbon dioxide.

[0126] In one embodiment, in step S101, the critical temperature and critical pressure of the impure carbon dioxide are calculated by the following steps: taking a pipeline carbon dioxide sample, testing the sample composition, and determining the mole fraction and thermodynamic parameters of each component; and calculating the critical temperature and critical pressure of the impure carbon dioxide based on the mole fraction and thermodynamic parameters of each component.

[0127] Specifically, a pipeline CO2 sample is taken and its composition is tested using gas chromatography to determine the mole fraction and thermodynamic parameters of each component (thermodynamic parameters include but are not limited to: critical temperature, critical pressure, critical volume, eccentricity factor, relative molecular mass, and interaction coefficient between components). Based on this, the critical temperature and critical pressure of the impure CO2 are calculated. Furthermore, the critical temperature and critical pressure of the impure CO2 can be calculated using the mole fraction weighting method, volume fraction weighting method, group contribution method, etc., which are not limited to the present invention.

[0128] As shown in Figure 1B, in step S102, the supercritical pipeline transmission temperature and pressure range is determined using the critical temperature and critical pressure, combined with the pipeline's maximum operating temperature and pressure. Within this range, the physical properties of the impure carbon dioxide are calculated. Specifically, these physical properties include, but are not limited to, density, dynamic viscosity, and thermal conductivity.

[0129] In one embodiment, in step S102, the density of impure carbon dioxide within the supercritical pipeline temperature and pressure range is calculated through the following steps a) to d). It should be noted that the calculation process for other physical parameters (such as dynamic viscosity and thermal conductivity) is similar to that for density. Methods capable of calculating other physical parameters (such as dynamic viscosity and thermal conductivity) can also be applied to the present invention, and the present invention does not limit the calculation process for other physical parameters (such as dynamic viscosity and thermal conductivity).

[0130] Step a: Calculate the compressibility factor of the impure carbon dioxide using the critical temperature as the initial temperature and the critical pressure as the initial pressure.

[0131] Specifically, the critical temperature T c is the initial temperature, the critical pressure P c The initial pressure is used to calculate the compressibility of the impure CO2 using an equation of state. Furthermore, the compressibility of the impure CO2 can be calculated using equations of state such as the PR equation (Peng-Robinson equation, referred to as the PR equation), the BWRS equation (Benedict-Webb-Rubin equation, also known as the BWR equation; in 1970, KE Starling improved the BWR equation and proposed the 11-parameter BWRS equation, which has a wider range of applications than the BWR equation), the RK equation (Redlich-Kwong equation of state, referred to as the RK equation), and the Span-Wagner equation (referred to as the SW equation).

[0132] Step b: Calculate the average relative molecular mass of the impure carbon dioxide based on the relative molecular mass of each component of the impure carbon dioxide and the mole fraction of each component.

[0133] In one embodiment, in step b, the average relative molecular mass of the impure carbon dioxide is calculated by the following expression:

[0134] Where, M is the average relative molecular mass of impurity carbon dioxide; i is the mole fraction of the i-th component; M i is the relative molecular mass of the i-th component.

[0135] Step c: Calculate the density of the impure carbon dioxide based on the average relative molecular mass and compression factor of the impure carbon dioxide.

[0136] In one embodiment, in step c, the density of the impure carbon dioxide is calculated by the following expression:

[0137] Wherein, ρ is the density of impure carbon dioxide; M is the average relative molecular mass of impure carbon dioxide; P is the pressure; Z is the compressibility factor of impure carbon dioxide; R is the molar gas constant; and T is the temperature.

[0138] Step d: Set the temperature step and the pressure step to determine the supercritical pipeline temperature and pressure range. Repeat steps a to c within the supercritical pipeline temperature and pressure range to obtain the density of impurity-containing carbon dioxide within the supercritical pipeline temperature and pressure range.

[0139] Specifically, δ T is the temperature step length, with δ P is the pressure step, and steps a to c are repeated within the supercritical pipeline temperature and pressure range to obtain the density of impure CO2. The lower limit of the supercritical pipeline temperature and pressure range is the initial temperature (e.g., the critical temperature T c , or the lower temperature limit may be lower than the critical temperature), the upper temperature limit is T max (For example, the maximum operating temperature of the pipeline is 50°C), the lower limit of pressure is the initial pressure (for example, the critical pressure P c ), the upper limit of pressure is P max (For example, the maximum working pressure of the pipeline is 15MPa).

[0140] As shown in FIG1B , in step S103, within the supercritical pipeline transmission temperature and pressure range, the physical property parameters of the impure carbon dioxide are combined to determine a temperature range in which the physical property parameters vary dramatically under a constant pressure condition, and this range is recorded as a first range. In practical applications, a single temperature range in which any single physical property parameter varies dramatically under a constant pressure condition may be determined as the first range; two temperature ranges in which any two physical properties vary dramatically under a constant pressure condition may be determined as the first range; or three temperature ranges in which three physical properties vary dramatically under a constant pressure condition may be determined as the first range, and the present invention is not limited thereto.

[0141] In one embodiment, in step S103, the temperature range in which the physical property parameters change drastically under constant pressure conditions is determined through the following steps S1031-S1034.

[0142] In step S1031, a three-dimensional surface of the physical property parameters of carbon dioxide containing impurities is constructed with temperature as the X-axis, pressure as the Y-axis, physical property parameters as the Z-axis, temperature step as the X-axis spacing, and pressure step as the Y-axis spacing. Specifically, temperature is the X-axis, pressure is the Y-axis, CO2 physical property parameters as the Z-axis, and temperature step δ is the Z-axis spacing. T is the X-axis spacing, pressure step δ P is the Y-axis spacing, and a three-dimensional surface of the physical property parameters of impure CO2 is constructed.

[0143] In step S1032, the numerical gradient component of each point on the three-dimensional surface in the X direction is calculated with the temperature step length as the interval, and the calculation result is recorded as the first matrix of each physical property parameter. Specifically, with the temperature step length δ T For the spacing, calculate the numerical gradient component of each point in the X direction on the three-dimensional surface of the physical property parameters of impurity CO2, and record the calculation results as the first matrix F of each physical property parameter T .

[0144] In step S1033, the average value of each element in the first matrix is ​​calculated to obtain the average value of the degree of change of the physical property parameter with temperature, and the first threshold value of the degree of change of the physical property parameter with temperature is obtained by combining the temperature threshold correction coefficient. Specifically, the first matrix F T The average value of each element in the supercritical pipeline is obtained, that is, the average value F of the degree of change of CO2 physical properties with temperature within the supercritical pipeline temperature and pressure range. Ta , determine the correction factor n based on the pipeline operating conditions and design specifications T , get the first threshold S of the degree of change of CO2 physical parameters with temperature T .

[0145] In one embodiment, the first threshold value of the degree of change of the physical property parameter with temperature is obtained by the following expression: S T =n T F Ta (3)

[0146] Where S T is the first threshold; n T is the temperature threshold correction coefficient; F Ta is the average value of the degree of change of physical parameters with temperature, that is, the average value of the first matrix.

[0147] In step S1034, in the first matrix, elements with a value less than the first threshold are screened, and the temperature range in which the physical property parameters change dramatically under a constant pressure condition is determined based on the temperature and pressure corresponding to the elements. Specifically, the first matrix F is screened. T is less than the first threshold S T For elements, the temperature range in which the physical properties change dramatically under a certain pressure is divided according to the temperature and pressure corresponding to the elements.

[0148] As shown in FIG1B , in step S104, within the supercritical pipeline transmission temperature and pressure range, the physical property parameters of the impure carbon dioxide are combined to determine a pressure range within which the physical property parameters vary dramatically under a constant temperature condition, and this range is recorded as the second range. In practical applications, a single pressure range within which any single physical property parameter varies dramatically under a constant temperature condition may be determined as the second range; two pressure ranges within which any two physical properties vary dramatically under a constant temperature condition may be determined as the second range; or three pressure ranges within which any three physical properties vary dramatically under a constant temperature condition may be determined as the second range, although the present invention is not limited thereto.

[0149] In one embodiment, in step S104, the pressure range in which the physical property parameters change drastically under a constant temperature condition is determined through the following steps S1041-S1043.

[0150] In step S1041, the numerical gradient component of each point on the three-dimensional surface in the Y direction is calculated with the pressure step length as the spacing, and the calculation result is recorded as the second matrix of each physical property parameter. Specifically, with the pressure step length δ p For the spacing, calculate the numerical gradient component of each point in the Y direction on the three-dimensional surface of the physical property parameters of impurity CO2, and record the calculation results as the second matrix F of each physical property parameter P .

[0151] In step S1042, the average value of each element in the second matrix is ​​calculated to obtain the average value of the degree of change of the physical property parameter with pressure, and the second threshold value of the degree of change of the physical property parameter with pressure is obtained by combining the pressure threshold correction coefficient. Specifically, the second matrix F P The average value of each element in the supercritical pipeline is obtained, that is, the average value F of the degree of change of CO2 physical properties with pressure within the supercritical pipeline temperature and pressure range. Pa , determine the correction factor n based on the pipeline operating conditions and design specifications P , and obtain the second threshold S of the degree of change of CO2 physical parameters with pressure P .

[0152] In one embodiment, the second threshold value of the degree of change of the physical property parameter with pressure is obtained by the following expression: S P =n P F Pa (4)

[0153] Where S P is the second threshold; n P is the pressure threshold correction coefficient; F Pa is the average value of the degree of change of physical parameters with pressure, that is, the average value of the second matrix.

[0154] In step S1043, in the second matrix, elements greater than the second threshold are screened, and the pressure range where the physical property parameters change dramatically under a constant temperature condition is determined based on the temperature and pressure corresponding to the elements. Specifically, the second matrix F is screened. P is greater than the second threshold S P For elements, the pressure range in which the physical properties change dramatically at a certain temperature is divided according to the temperature and pressure corresponding to the elements.

[0155] As shown in FIG. 1B , in step S105 , the first range and the second range are merged to obtain a quasi-critical region for pipeline-transported impurity-containing carbon dioxide.

[0156] In one embodiment, in step S105, the quasi-critical region for pipeline-transported carbon dioxide containing impurities is obtained by fusing the first range and the second range of the desired physical property parameter to obtain the quasi-critical region for pipeline-transported carbon dioxide containing impurities. In practical applications, the first range and the second range of any single physical property parameter can be fused, the first range and the second range of any two physical property parameters can be fused, or the first range and the second range of three physical property parameters can be fused, and the present invention is not limited thereto.

[0157] In one embodiment, the temperature range in which physical properties change dramatically at a constant pressure is denoted as Set A, and the pressure range in which physical properties change dramatically at a constant temperature is denoted as Set B. The union of Sets A and B is taken to obtain the quasi-critical region for pipeline transport of impure CO2. It should be noted that other fusion methods capable of obtaining the quasi-critical region for pipeline transport of impure CO2 can also be applied to the present invention, and the present invention does not limit the method for fusion of the first and second ranges.

[0158] The present invention proposes a method and device for determining the quasi-critical zone of pipeline-transported impure carbon dioxide. First, the impurity composition of the pipeline-transported CO2 is tested, and the physical properties of CO2 within the supercritical pipeline temperature and pressure range are calculated using the state equation. Then, using the CO2 physical properties as reference parameters, the temperature range where the physical properties change dramatically at a constant pressure and the pressure range where the physical properties change dramatically at a constant temperature are divided. The two division results are combined to determine the quasi-critical zone of the impure CO2.

[0159] The present invention considers the influence of pressure at a constant temperature on the physical properties of CO2 on the basis of the quasi-critical temperature, and at the same time delineates the temperature and pressure ranges using the gradient of the physical property parameters as the threshold, thereby narrowing the range of the quasi-critical zone. The demarcation results of the quasi-critical zone for impure CO2 are more accurate, and can provide a basis for the safe control of supercritical CO2 pipeline transportation.

[0160] The method and device for determining the quasi-critical zone of pipeline-transported impurity-containing carbon dioxide provided by the present invention can also be used in conjunction with a computer-readable storage medium, which stores a computer program. The computer program is executed to run a method for determining the quasi-critical zone of pipeline-transported impurity-containing carbon dioxide.

[0161] A computer program can run computer instructions, which include computer program code. The computer program code can be in source code form, object code form, executable file or some intermediate form.

[0162] Computer-readable storage media may include: any entity or device that can carry computer program code, recording media, USB flash drives, mobile 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.

[0163] It should be noted that the content contained in computer-readable storage media can be appropriately increased or decreased according to the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practices, computer-readable storage media do not include electrical carrier signals and telecommunications signals.

[0164] According to another aspect of the present invention, a device for determining the quasi-critical zone of pipeline-transported impurity-containing carbon dioxide is also provided, which is configured to execute a method for determining the quasi-critical zone of pipeline-transported impurity-containing carbon dioxide. The device includes: a critical temperature and pressure calculation module, a physical property parameter calculation module, a range demarcation module, and a quasi-critical zone determination module.

[0165] In one embodiment, the critical temperature and pressure calculation module is used to calculate the critical temperature and critical pressure of the impure carbon dioxide based on the composition of the pipeline-transported impure carbon dioxide.

[0166] In one embodiment, the physical property parameter calculation module is connected to the critical temperature and pressure calculation module, and is used to determine the supercritical pipeline temperature and pressure range through the critical temperature and critical pressure, combined with the maximum operating temperature and maximum operating pressure of the pipeline, and calculate the physical property parameters of impure carbon dioxide within the supercritical pipeline temperature and pressure range.

[0167] In one embodiment, the range definition module is connected to the physical property parameter calculation module to perform the following steps: within the supercritical pipeline temperature and pressure range, determine the temperature range in which the physical property parameters change dramatically under constant pressure conditions, and record it as the first range; within the supercritical pipeline temperature and pressure range, determine the pressure range in which the physical property parameters change dramatically under constant temperature conditions, and record it as the second range.

[0168] In one embodiment, the quasi-critical region determination module is connected to the range delineation module, and is configured to obtain a quasi-critical region corresponding to the pipeline-transported impurity-containing carbon dioxide according to the first range and the second range.

[0169] In one embodiment, taking the impure CO2 with N2 mole fraction of 4% and CH4 mole fraction of 1% as an example, assuming that δ T 0.5K, δ P 0.2MPa, n T and n P are all 1. According to a method for determining the quasi-critical zone of pipeline-transported impure carbon dioxide provided by the present invention, the quasi-critical zone of pipeline-transported impure CO2 is calculated. The three-dimensional surface of the density of impure CO2 is shown in FIG2 . The first range, that is, the range of set A in the P (pressure)-T (temperature) coordinate diagram is shown in FIG3 . The second range, that is, the range of set B in the P (pressure)-T (temperature) coordinate diagram is shown in FIG4 . The quasi-critical zone of pipeline-transported impure CO2 is shown in FIG5 .

[0170] In summary, the present invention provides a method and device for determining the quasi-critical zone of pipeline-transported impurity-laden carbon dioxide, which has the following advantages over the prior art:

[0171] The present invention proposes a method and apparatus for determining the quasi-critical zone of pipeline-transported impure carbon dioxide. The method first tests the impurity composition of the pipeline-transported CO2, then calculates the physical properties of the CO2 within the supercritical pipeline temperature and pressure range using an equation of state. The method then divides the temperature range within which the physical properties change dramatically at a constant pressure into the pressure range within which the physical properties change dramatically at a constant temperature. The two division results are then combined to determine the quasi-critical zone of the impure CO2. The method considers the effect of pressure at a constant temperature on the physical properties of CO2, based on the quasi-critical temperature. Furthermore, the method uses the gradient of the physical property parameters as a threshold to define the temperature and pressure ranges, thereby narrowing the scope of the quasi-critical zone and providing a more accurate division of the quasi-critical zone of the impure CO2. This method can provide a basis for the safe control of supercritical CO2 pipeline transportation.

[0172] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should extend to equivalent substitutions of these features understood by those skilled in the relevant art. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0173] In the description of the present invention, unless otherwise specified, "plurality" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," "tail," etc., indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present 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.

[0174] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0175] Certain terms are used throughout this application document to indicate specific system components. As will be appreciated by those skilled in the art, different names may be used to indicate the same component, and thus this application document is not intended to distinguish between 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 format and should therefore be interpreted as meaning "including, but not limited to...". In addition, the terms "substantially," "essentially," or "approximately" as may be used herein relate to the tolerances for the corresponding terms accepted by the industry. The term "coupling," as may be used herein, includes direct coupling and indirect coupling via another component, assembly, circuit, or module, wherein for indirect coupling, the intervening component, assembly, circuit, or module does not change the information of the signal but can adjust its current level, voltage level, and / or power level. Inferred coupling (e.g., where one component is coupled to another component by inference) includes direct and indirect coupling between two components in the same manner as "coupling."

[0176] References in this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, appearances of the phrases "one embodiment" or "an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment.

[0177] The embodiments of the present invention are presented 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 will be apparent to those skilled in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as suited for specific applications.

[0178] Although the embodiments disclosed herein are as described above, the contents described herein are merely embodiments for facilitating understanding of the present invention and are not intended to limit the present invention. Any person skilled in the art of the present invention may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed herein. 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 determining the quasi-critical region of pipeline-transported impurity-containing carbon dioxide, characterized in that: The method comprises: Based on the composition of the impure carbon dioxide transported in pipelines, the critical temperature and critical pressure of the impure carbon dioxide are calculated, and combined with the maximum working temperature and maximum working pressure of the pipeline to determine the supercritical pipeline temperature and pressure range; Calculating the physical property parameters of the impure carbon dioxide within the supercritical pipeline transmission temperature and pressure range; Determine the temperature range in which the physical property parameters change drastically under a constant pressure condition and the pressure range in which the physical property parameters change drastically under a constant temperature condition, and record them as a first range and a second range; According to the first range and the second range, a quasi-critical region corresponding to pipeline-transported carbon dioxide containing impurities is obtained.

2. The method according to claim 1, characterized in that The first range and the second range are determined by the following steps: The numerical gradient components of each point in different directions on the three-dimensional surface of the physical property parameters of the impure carbon dioxide are calculated to obtain the first range and the second range.

3. The method according to claim 2, characterized in that The three-dimensional surface is obtained by the following steps: With temperature as the X-axis, pressure as the Y-axis, and physical property parameters as the Z-axis, the three-dimensional surface of the physical property parameters of impure carbon dioxide is constructed.

4. The method according to claim 3, characterized in that The first range is obtained by the following steps: Calculating the numerical gradient component of each point on the three-dimensional surface in the X direction, and recording the calculation result as the first matrix corresponding to the physical property parameter; In the first matrix, elements whose values ​​are smaller than a first threshold are screened, and the first range is obtained according to the temperature and pressure corresponding to the elements.

5. The method according to claim 4, characterized in that The first threshold is determined by the following steps: Calculating the average value of each element in the first matrix to obtain a first average value of the degree of change of the physical property parameter with temperature; Set the temperature threshold correction factor based on the operating conditions and design specifications of the pipeline; The product of the temperature threshold correction coefficient and the first average value is calculated as the first threshold value of the degree of change of the physical property parameter with temperature.

6. The method according to any one of claims 3 to 5, characterized in that The second range is determined by the following steps: Calculate the numerical gradient component of each point on the three-dimensional surface in the Y direction, and record the calculation result as the second matrix corresponding to the physical property parameter; In the second matrix, elements greater than a second threshold are screened, and the second range is obtained according to the temperature and pressure corresponding to the elements.

7. The method according to claim 6, characterized in that The second threshold is determined by the following steps: averaging the elements in the second matrix to obtain a second average value of the degree of change of the physical property parameter with pressure; Set the pressure threshold correction factor based on the pipeline's operating conditions and design specifications; The product of the pressure threshold correction coefficient and the second average value is calculated as the second threshold value of the degree of change of the physical property parameter with pressure.

8. The method according to any one of claims 1 to 7, characterized in that The critical temperature and the critical pressure are calculated by the following steps: Taking pipeline carbon dioxide as a sample, testing the composition of the sample, and determining the mole fraction and thermodynamic parameters of each component; The critical temperature and the critical pressure are calculated based on the mole fraction of each component and the thermodynamic parameters.

9. The method according to claim 8, characterized in that The physical properties of carbon dioxide containing impurities are calculated by the following steps: According to the composition of the sample, a variety of state equations are used to calculate theoretical results corresponding to the physical property parameters; Measure the physical property parameters of pipeline-transported carbon dioxide containing impurities and obtain the measured results corresponding to the physical property parameters; The mean square error between the measured result and each of the theoretical results is calculated, and the physical property parameters of the impure carbon dioxide are calculated through the state equation corresponding to the theoretical result with the smallest mean square error.

10. The method according to any one of claims 1 to 9, characterized in that The supercritical pipeline transmission temperature and pressure range is determined by the following steps: Taking the critical temperature as the lower temperature limit and the maximum operating temperature as the upper temperature limit, combined with the temperature step, the supercritical pipeline temperature range is obtained; Taking the critical pressure as the lower pressure limit and the maximum working pressure as the upper pressure limit, combined with the pressure step length, the supercritical pipeline pressure range is obtained; Based on the supercritical pipeline transportation temperature range and the supercritical pipeline transportation pressure range, the supercritical pipeline transportation temperature and pressure range is obtained.

11. The method according to any one of claims 1 to 10, characterized in that The physical property parameters include any one of density, expansion coefficient, compression coefficient, dynamic viscosity, thermal conductivity, and specific heat capacity, or a combination thereof.

12. The method according to claim 11, characterized in that The density of impure carbon dioxide within the supercritical pipeline temperature and pressure range is calculated by the following steps: Step a, taking the critical temperature as the initial temperature and the critical pressure as the initial pressure, calculating the compressibility factor of the impure carbon dioxide; Step b, calculating the average relative molecular mass of the impure carbon dioxide based on the relative molecular mass of each component of the impure carbon dioxide and the mole fraction of each component; Step c, calculating the density of the impure carbon dioxide according to the average relative molecular mass of the impure carbon dioxide and the compression factor; Step d, repeating steps a to c within the supercritical pipeline temperature and pressure range to obtain the density of impure carbon dioxide within the supercritical pipeline temperature and pressure range.

13. The method according to any one of claims 1 to 12, characterized in that The quasi-critical region is obtained by the following steps: The union of the first range and the second range is taken as the quasi-critical zone for pipeline transportation of impurity-containing carbon dioxide.

14. A storage medium, characterized in that: It contains instructions for executing the method as claimed in any one of claims 1-13.

15. A device for determining the quasi-critical zone of impure carbon dioxide transported in a pipeline, characterized in that: The device is configured to perform the method according to any one of claims 1 to 13, the device comprising: A critical temperature and pressure calculation module, which is used to calculate the critical temperature and the critical pressure of the impure carbon dioxide based on the composition of the pipeline-transported impure carbon dioxide; A physical property parameter calculation module, which is connected to the critical temperature and pressure calculation module, and is used to determine the supercritical pipeline temperature and pressure range through the critical temperature and the critical pressure, combined with the maximum working temperature and the maximum working pressure of the pipeline, and calculate the physical property parameters of the impurity-containing carbon dioxide within the supercritical pipeline temperature and pressure range; A range delimiting module is connected to the physical property parameter calculation module and is used to perform the following steps: within the supercritical pipeline temperature and pressure range, determine the temperature range in which the physical property parameters change dramatically under a constant pressure condition, and record it as the first range; within the supercritical pipeline temperature and pressure range, determine the pressure range in which the physical property parameters change dramatically under a constant temperature condition, and record it as the second range; A quasi-critical region determination module is connected to the range delimitation module and is used to obtain the quasi-critical region corresponding to the pipeline-transported impurity-containing carbon dioxide according to the first range and the second range.

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