Phase state identification and early warning method and device for carbon dioxide multicomponent system under pipeline transportation conditions

Abstract

The present invention discloses a method and device for identifying and warning the phase state of a carbon dioxide multi-component system under pipeline transportation conditions, and relates to the technical field of CO2 phase state identification. The method comprises: determining and summarizing the phase state of the CO2 multi-component system in the pipeline area where each marked position is located based on the P-T phase diagram of the CO2 multi-component system within the pipeline temperature and pressure range, and the temperature data and pressure data at different marked positions of the target CO2 pipeline, to obtain the phase state trend of the CO2 multi-component system in the target CO2 pipeline area; when the phase state trend of the CO2 multi-component system in the target CO2 pipeline area meets any constraint condition in the constraint set, determining that the target CO2 pipeline is in a dangerous state, and performing a warning operation. The present invention overcomes the problem that existing pipeline safety monitoring technology is difficult to accurately reflect the operating status of the CO2 pipeline, and can provide a theoretical reference for the design of CO2 pipeline schemes.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 phase recognition, and in particular to a method and device for phase recognition and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions. Background Art

[0002] Under the current energy structure, carbon capture, utilization, and storage (CCUS) technology is the primary means of achieving CO2 emission reductions. As a bridge connecting carbon sources and carbon sinks in the CCUS process, CO2 pipeline transportation technology shows good prospects. Unlike natural gas and crude oil, CO2 can exist in gas, liquid, dense, and supercritical phases in pipelines. When the temperature drops to the freezing point, CO2 will exist in solid form. CO2 has a low critical temperature (31.1°C) and critical pressure (7.38MPa), and is prone to phase change during transportation, causing drastic changes in pipeline operating parameters. Existing pipeline safety monitoring technology mainly detects abnormalities in pipeline operating parameters through online monitoring of pipeline temperature, pressure, and flow rate changes. It cannot identify and issue early warnings for the phase state of the fluid in the pipeline, making it difficult to provide timely feedback on safety issues during CO2 pipeline operation. Summary of the Invention

[0003] The purpose of the present invention is to provide a method and device for phase state identification and early warning of a carbon dioxide multi-component system under pipeline transportation conditions, so as to overcome the problem that existing pipeline safety monitoring technology is difficult to accurately reflect the operating status of the CO2 pipeline, and provide a theoretical reference for the design of CO2 pipeline transportation schemes.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] In a first aspect, the present invention provides a method for phase state identification and early warning of a carbon dioxide multi-component system under pipeline transportation conditions, comprising:

[0006] During the operation of the target CO2 pipeline, temperature data and pressure data at different marked positions on the target CO2 pipeline are obtained;

[0007] According to the PT phase diagram of the CO2 multi-component system within the pipeline temperature and pressure range, and the temperature data and pressure data at different marked positions, the phase state of the CO2 multi-component system in the pipeline area where each marked position is located is determined; the horizontal axis of the PT phase diagram of the CO2 multi-component system is temperature, and the vertical axis of the PT phase diagram of the CO2 multi-component system is pressure; the temperature corresponding to the intersection of the bubble point line of the PT phase diagram of the CO2 multi-component system and the dew point line of the PT phase diagram of the CO2 multi-component system is the critical temperature, and the pressure corresponding to the intersection of the bubble point line and the dew point line is the critical pressure; the PT phase diagram of the CO2 multi-component system includes a gas phase region, a liquid phase region, a gas-liquid two-phase region, a dense phase region and a supercritical phase region; the gas phase region is the region below the dew point line, the liquid phase region is the region above the bubble point line and below the critical pressure line, the gas-liquid two-phase region is the region between the dew point line and the bubble point line, the dense phase region is the region above the critical pressure line and below the critical temperature line, and the supercritical phase region is the region above the critical temperature line and above the critical pressure line;

[0008] The phase states of the CO2 multicomponent system in the pipeline area where all marked positions are located are summarized to obtain the phase state trend of the CO2 multicomponent system in the target CO2 pipeline area;

[0009] When the phase trend of the CO2 multi-element system in the target CO2 pipeline area meets any constraint condition in the first constraint set, the target CO2 pipeline is determined to be in a dangerous state and an early warning operation is performed; wherein, the first constraint set includes constraints for shifting from the interior of the gas phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the liquid phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the dense phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the gas phase region to the quasi-critical region, constraints for shifting from the interior of the liquid phase region to the quasi-critical region, and constraints for shifting from the interior of the dense phase region to the quasi-critical region; the quasi-critical region is divided according to the physical properties of the CO2 multi-element system in the supercritical state; the interior of the gas phase region is the region within the gas phase region excluding the quasi-critical region; the interior of the dense phase region is the region within the dense phase region excluding the quasi-critical region; and the interior of the liquid phase region is the region within the liquid phase region excluding the quasi-critical region.

[0010] In a second aspect, the present invention provides a phase state identification and early warning device for a carbon dioxide multi-component system under pipeline transportation conditions, comprising:

[0011] A data acquisition module is used to acquire temperature data and pressure data at different marked positions on the target CO2 pipeline during its operation;

[0012] a marked position phase state determination module, for determining the phase state of the CO2 multi-component system in the pipeline area where each marked position is located based on the CO2 multi-component system PT phase diagram within the pipeline temperature and pressure range, and the temperature data and pressure data at different marked positions; the horizontal axis of the CO2 multi-component system PT phase diagram is temperature, and the vertical axis of the CO2 multi-component system PT phase diagram is pressure; the temperature corresponding to the intersection of the bubble point line of the CO2 multi-component system PT phase diagram and the dew point line of the CO2 multi-component system PT phase diagram is the critical temperature, and the pressure corresponding to the intersection of the bubble point line and the dew point line is the critical pressure; the CO2 multi-component system PT phase diagram includes a gas phase region, a liquid phase region, a gas-liquid two-phase region, a dense phase region and a supercritical phase region; the gas phase region is the region below the dew point line, the liquid phase region is the region above the bubble point line and below the critical pressure line, the gas-liquid two-phase region is the region between the dew point line and the bubble point line, the dense phase region is the region above the critical pressure line and below the critical temperature line, and the supercritical phase region is the region above the critical temperature line and above the critical pressure line;

[0013] The phase state trend determination module is used to summarize the phase states of the CO2 multi-element system in the pipeline area where all marked positions are located, and obtain the phase state trend of the CO2 multi-element system in the target CO2 pipeline area;

[0014] A dangerous state determination and early warning module is used to determine that the target CO2 pipeline is in a dangerous state and perform an early warning operation when the phase trend of the CO2 multi-component system in the target CO2 pipeline area meets any constraint condition in a first constraint set; wherein the first constraint set includes constraints for shifting from the interior of the gas phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the liquid phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the dense phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the gas phase region to the quasi-critical region, constraints for shifting from the interior of the liquid phase region to the quasi-critical region, and constraints for shifting from the interior of the dense phase region to the quasi-critical region; the quasi-critical region is divided according to the physical properties of the CO2 multi-component system in a supercritical state; the interior of the gas phase region is the region within the gas phase region excluding the quasi-critical region; the interior of the dense phase region is the region within the dense phase region excluding the quasi-critical region; and the interior of the liquid phase region is the region within the liquid phase region excluding the quasi-critical region.

[0015] In a third aspect, the present invention provides a phase state identification and early warning device for a carbon dioxide multi-component system under pipeline transportation conditions, comprising: a plurality of online monitoring devices, a signal receiving device connected to each of the online monitoring devices, and a data processing and analysis system connected to the signal receiving device; a plurality of marking positions are set along the target CO2 pipeline, and an online monitoring device is installed at each marking position;

[0016] The signal receiving device is used to receive the temperature data and pressure data at the marked position on the target CO2 pipeline collected by each online monitoring device, and send them to the data processing and analysis system;

[0017] The data processing and analysis system is used to execute the phase state identification and early warning method for a carbon dioxide multi-component system under pipeline transportation conditions described in the first aspect.

[0018] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0019] The present invention converts the real-time operation data of the pipeline into the phase state of the CO2 multi-element system in the pipeline area, and determines the pipeline safety status based on the phase state of the CO2 multi-element system in the pipeline area, solving the problem that traditional pipeline safety monitoring technology is difficult to detect CO2 pipeline operation anomalies in a timely and accurate manner, thereby discovering hidden dangers at the first time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 A schematic flow chart of a method for phase identification and early warning of a carbon dioxide multi-component system under pipeline transportation conditions provided by an embodiment of the present invention;

[0022] Figure 2 PT phase diagram of a CO2 multicomponent system within the pipeline transmission temperature and pressure range provided by an embodiment of the present invention;

[0023] Figure 3 A schematic flow chart of a method for phase state identification and early warning of a carbon dioxide multicomponent system, including data acquisition, entry, transmission, processing, analysis, display, and early warning functions, provided in an embodiment of the present invention;

[0024] Figure 4 This is a structural schematic diagram of a phase state identification and early warning device for a carbon dioxide multi-component system under pipeline transportation conditions provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Example 1

[0028] Pipeline transportation offers advantages such as high throughput, high efficiency, and low costs, making it the primary method for transporting CO2 in future large-scale CCUS projects. However, CO2 is prone to phase transitions during pipeline transportation, leading to dramatic changes in physical properties such as density, viscosity, and specific heat, causing unstable flow and compromising safe pipeline operation. Currently, no methods for identifying and providing early warning of the phase state of multicomponent CO2 systems during pipeline transportation have been reported.

[0029] like Figure 1 As shown, this embodiment provides a phase state identification and early warning method for a carbon dioxide multi-component system under pipeline transportation conditions, comprising the following steps.

[0030] Step 100: During the operation of the target CO2 pipeline, temperature data and pressure data at different marked positions on the target CO2 pipeline are obtained.

[0031] Step 200: Determine the phase state of the CO2 multi-component system in the pipeline area where each marked position is located based on the PT phase diagram of the CO2 multi-component system within the pipeline temperature and pressure range and the temperature data and pressure data at different marked positions.

[0032] like Figure 2 As shown, the horizontal axis of the CO2 multi-component system PT phase diagram is temperature, and the vertical axis of the CO2 multi-component system PT phase diagram is pressure; the horizontal axis of the CO2 multi-component system PT phase diagram is temperature, and the vertical axis of the CO2 multi-component system PT phase diagram is pressure; the temperature corresponding to the intersection of the bubble point line of the CO2 multi-component system PT phase diagram and the dew point line of the CO2 multi-component system PT phase diagram is the critical temperature, and the pressure corresponding to the intersection of the bubble point line and the dew point line is the critical pressure; the CO2 multi-component system PT phase diagram includes a gas phase region, a liquid phase region, a gas-liquid two-phase region, a dense phase region and a supercritical phase region; the gas phase region is the region below the dew point line, the liquid phase region is the region above the bubble point line and below the critical pressure line, the gas-liquid two-phase region is the region between the dew point line and the bubble point line, the dense phase region is the region above the critical pressure line and below the critical temperature line, and the supercritical phase region is the region above the critical temperature line and above the critical pressure line.

[0033] Step 300: Summarize the phase states of the CO2 multicomponent system in the pipeline area where all marked positions are located to obtain the phase state trend of the CO2 multicomponent system in the target CO2 pipeline area.

[0034] Step 400: When the phase trend of the CO2 multi-element system in the target CO2 pipeline area meets any constraint condition in the first constraint set, it is determined that the target CO2 pipeline is in a dangerous state and an early warning operation is performed; wherein the first constraint set includes constraints for shifting from the interior of the gas phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the liquid phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the dense phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the gas phase region to the quasi-critical region, constraints for shifting from the interior of the liquid phase region to the quasi-critical region, and constraints for shifting from the interior of the dense phase region to the quasi-critical region; the quasi-critical region is divided according to the physical properties of the CO2 multi-element system in a supercritical state; the interior of the gas phase region is the region within the gas phase region excluding the quasi-critical region; the interior of the dense phase region is the region within the dense phase region excluding the quasi-critical region; and the interior of the liquid phase region is the region within the liquid phase region excluding the quasi-critical region.

[0035] Furthermore, the method provided by an embodiment of the present invention also includes: when the phase trend of the CO2 multi-component system in the target CO2 pipeline area meets any constraint condition in a second constraint set, determining that the target CO2 pipeline is in a safe state; wherein the second constraint set includes constraint conditions within the gas phase region, constraint conditions within the liquid phase region, and constraint conditions within the dense phase region.

[0036] In the embodiment of the present invention, the impurity content of CO2 used for pipeline transportation is relatively low. Therefore, considering the characteristics of the physical property changes of the CO2 multi-component system and combining the definition method of the pure CO2 quasi-critical region, the quasi-critical region of the CO2 multi-component system is divided according to the following range, that is, the quasi-critical region is determined according to the following formula.

[0037] 0.8P c <P<2P c .

[0038]

[0039] T pc The system density of CO2 multimer is calculated using the following formula:

[0040]

[0041]

[0042] Where, P is the pressure corresponding to the quasi-critical region, T is the temperature corresponding to the quasi-critical region, and P c is the critical pressure of the CO2 multicomponent system, For CO2 multi-component system at 0.8P c Evaporation temperature under pressure, T pc is the critical temperature of the CO2 multicomponent system, and ρ is the density of the CO2 multicomponent system.

[0043] In the embodiment of the present invention, the process of determining the PT phase diagram of the CO2 multicomponent system within the pipeline temperature and pressure range is as follows:

[0044] (1) Obtain the mole fraction and thermodynamic parameters of each component in a CO2 multicomponent system sample for pipeline transportation.

[0045] (2) Based on the mole fraction and thermodynamic parameters of each component in the CO2 multicomponent system sample and the PVT data of the CO2 multicomponent system sample obtained by testing, the binary interaction coefficient of each component is regressed.

[0046] (3) Based on the mole fraction, thermodynamic parameters and binary interaction coefficient of each component in the CO2 multicomponent system sample, the bubble point pressure and dew point pressure of the CO2 multicomponent system sample at different temperatures are calculated.

[0047] (4) Draw the bubble point line and the dew point line based on all bubble point pressures and all dew point pressures.

[0048] (5) Based on the bubble point line and dew point line, draw the PT phase diagram of the CO2 multicomponent system within the pipeline temperature and pressure range.

[0049] In an embodiment of the present invention, obtaining the mole fraction and thermodynamic parameters of each component in a CO2 multicomponent system sample for pipeline transportation specifically includes:

[0050] Gas chromatography was used to obtain the mole fraction and thermodynamic parameters of each component in the CO2 multicomponent system sample for pipeline transportation.

[0051] In an embodiment of the present invention, the regressing the binary interaction coefficients of the components based on the mole fractions and thermodynamic parameters of the components in the CO2 multicomponent system sample and the PVT data of the CO2 multicomponent system sample obtained by testing specifically includes:

[0052] 1) Select m test points and use a PVT high-pressure physical property analyzer to obtain PVT data of the CO2 multi-component system sample in the gas phase or liquid phase at each test point; the PVT data includes temperature, pressure and specific volume.

[0053] 2) The mole fractions and thermodynamic parameters of each component in the CO2 multicomponent system sample, as well as the temperature, pressure, and specific volume of each test point, are substituted into the Peng-Robinson equation of state. The equation coefficients corresponding to each test point are calculated, and the form of the expression of the equation coefficients is transformed according to the van der Waals mixing rule to obtain an overdetermined ill-conditioned linear system of equations.

[0054] 3) The singular value decomposition method is used to solve the overdetermined ill-conditioned linear equations and obtain the least squares solution of the binary interaction coefficients of each component.

[0055] In an embodiment of the present invention, the bubble point pressure and dew point pressure of the CO2 multicomponent system sample at different temperatures are calculated based on the mole fraction and thermodynamic parameters of each component in the CO2 multicomponent system sample, specifically including: according to the determined pressure, temperature, and the mole fraction, thermodynamic parameters and binary interaction coefficient of each component in the CO2 multicomponent system sample, the Wilson formula and the Peng-Robinson state equation are used to calculate the gas phase fugacity coefficient and liquid phase fugacity coefficient of each component in the CO2 multicomponent system sample, and the bubble point pressure and dew point pressure are calculated based on the gas-liquid equilibrium constant when the gas phase fugacity coefficient and the liquid phase fugacity coefficient are the same, then the pressure and temperature are changed, and the above steps are repeated to calculate the bubble point pressure and dew point pressure of the CO2 multicomponent system sample at different temperatures.

[0056] The detailed process of the above steps is as follows:

[0057] S1: Determine pressure and temperature.

[0058] S2: Based on the pressure, temperature and thermodynamic parameters of each component in the CO2 multicomponent system sample, the Wilson formula is used to estimate the gas-liquid equilibrium constant of each component.

[0059] S3: Based on the mole fraction of each component in the CO2 multicomponent system sample and the gas-liquid equilibrium constant, the iterative method is used to calculate the CO2 multicomponent system gasification rate at the bubble point pressure and the CO2 multicomponent system gasification rate at the dew point pressure.

[0060] S4: Calculate the gas phase mole fraction and liquid phase mole fraction of each component in the CO2 multi-component system sample based on the CO2 multi-component system gasification rate at the bubble point pressure, the CO2 multi-component system gasification rate at the dew point pressure, and the mole fraction and gas-liquid equilibrium constant of each component in the CO2 multi-component system sample.

[0061] S5: Based on the gas phase mole fraction, liquid phase mole fraction and binary interaction coefficient of each component in the CO2 multicomponent system sample, the gas phase molar volume and liquid phase molar volume of the CO2 multicomponent system sample are iteratively calculated using the Peng-Robinson equation of state.

[0062] S6: Calculate the gas phase compressibility factor of the CO2 multicomponent system sample based on the gas phase molar volume of the CO2 multicomponent system sample.

[0063] S7: Calculate the liquid phase compressibility factor of the CO2 multicomponent system sample based on the liquid phase molar volume of the CO2 multicomponent system sample.

[0064] S8: Calculate the gas phase fugacity coefficient and liquid phase fugacity coefficient of each component in the CO2 multicomponent system sample based on the gas phase compressibility factor and liquid phase compressibility factor of the CO2 multicomponent system sample.

[0065] S9: Calculate the bubble point pressure and the dew point pressure based on the gas-liquid equilibrium constant when the gas phase fugacity coefficient and the liquid phase fugacity coefficient are the same; when the gas phase fugacity coefficient and the liquid phase fugacity coefficient are different, modify the gas-liquid equilibrium constant to the ratio of the liquid phase fugacity coefficient to the gas phase fugacity coefficient, and repeat steps S3 to S8 until the gas phase fugacity coefficient is the same as the liquid phase fugacity coefficient.

[0066] S10: Change the pressure and temperature, repeat steps S2 to S9, and calculate the bubble point pressure and dew point pressure of the CO2 multicomponent system sample at different temperatures.

[0067] Example 2

[0068] This embodiment provides a carbon dioxide multi-component system phase state identification and early warning method including data collection, entry, transmission, processing, analysis, display and early warning functions.

[0069] like Figure 3 As shown, the carbon dioxide multi-element system phase state identification and early warning method includes the following steps.

[0070] The first step is to collect and enter basic data for phase identification and early warning of CO2 multi-component systems.

[0071] A CO2 multicomponent system sample for pipeline transportation was extracted, and the mole fraction and thermodynamic parameters (critical temperature, critical pressure, eccentricity factor, relative molecular mass) of each component of the sample were measured by gas chromatography. The mole fraction and thermodynamic parameters of each component were then transferred to the data processing and analysis system for the regression of the binary interaction coefficients of each component and the drawing of the PT phase diagram of the CO2 multicomponent system.

[0072] Online monitoring devices are installed along the CO2 pipeline to record the changes in temperature and pressure at different locations during pipeline operation. The collected data are transmitted to the data processing and analysis system in real time through the signal receiving device, providing basic parameters for phase identification and early warning of the CO2 multi-component system.

[0073] In the second step, the PVT data of CO2 multicomponent system samples were tested and the binary interaction coefficients of each component were regressed.

[0074] ① Select m test points and use PVT high-pressure physical property analyzer to test the temperature, pressure and specific volume of CO2 multi-component system sample in gas phase or liquid phase (excluding gas-liquid coexistence state). It should be noted here that in order to ensure the accuracy of binary interaction coefficient regression, m should be no less than n is the number of components in the CO2 multicomponent sample. This step uses the Peng-Robinson equation of state as an example. When using this equation to calculate the physical properties of CO2 multicomponent systems, the accuracy is highest near the critical point, so the test point should be selected near the critical point. If other equations of state are used, the test point should be selected within the optimal range of that equation.

[0075] ②Substitute the temperature, pressure and specific volume of each test point into the Peng-Robinson state equation and calculate the corresponding equation coefficient a m :

[0076]

[0077] in:

[0078] b=∑z i b i .

[0079]

[0080] Where, P m The pressure at each test point, V m is the specific volume of each test point; T m is the temperature of each test point, R is the molar gas constant, z i is the mole fraction of each component, T ci is the critical temperature of each component, P ci is the critical pressure of each component, subscript m is the number of the test point, and subscript i is the number of the component.

[0081] ③ According to the van der Waals mixing rule, the coefficient a m It can be expressed as:

[0082]

[0083] in:

[0084]

[0085]

[0086]

[0087] Where k ij is the binary interaction coefficient between component i and component j, T rmi is the comparative temperature of component i at test point m, ω i is the eccentricity factor of component i.

[0088] ④For m test points, there are m equations in total, and the equation system can be written as:

[0089] A·X=B.

[0090] in:

[0091]

[0092] element a i,j,m Defined as:

[0093]

[0094] X is defined as:

[0095] X=[k 1.2 … k 1.n k 2.3 … k 2.n … k n-1.n ] T .

[0096] B is defined as:

[0097] B=[b1 b2 … b m-1 b m ] T .

[0098] Element b m Defined as:

[0099]

[0100] ⑤ The singular value decomposition (SVD) method is used to solve the above overdetermined ill-conditioned linear equations to obtain the binary interaction coefficient k of each component ij The least squares solution of .

[0101] The third step is to draw the PT phase diagram of the CO2 multicomponent system within the pipeline temperature and pressure range.

[0102] (1) Given the pressure P and temperature T, the Wilson formula is used to estimate the gas-liquid equilibrium constant of each component. The calculation formula for the gas-liquid equilibrium constant is shown below.

[0103]

[0104] Where K i is the gas-liquid equilibrium constant of the i-th component, P ci is the critical pressure of the i-th component, T ci is the critical temperature of the i-th component, P is the pressure, T is the temperature, ω i is the eccentricity factor of the i-th component.

[0105] (2) Based on the mole fractions of the components of the input data analysis system and the calculated gas-liquid equilibrium constant, the iterative method is used to calculate the gasification rate of the CO2 multicomponent system at the bubble point pressure and the gasification rate of the CO2 multicomponent system at the dew point pressure.

[0106] The bubble point pressure equation is:

[0107]

[0108] The dew point pressure equation is:

[0109]

[0110] Where z i is the mole fraction of the i-th component, and η is the gasification rate of the CO2 multicomponent system.

[0111] (3) Calculate the gas phase mole fraction and liquid phase mole fraction of each component in the CO2 multicomponent system.

[0112]

[0113]

[0114] Where y i is the gas phase mole fraction of the i-th component in the CO2 multicomponent system, x i is the liquid phase mole fraction of the i-th component in the CO2 multicomponent system.

[0115] (4) Substitute the binary interaction coefficient into the Peng-Robinson equation of state and iteratively calculate the gas phase molar volume and liquid phase molar volume of the CO2 multicomponent system.

[0116] Let’s take the calculation of liquid phase molar volume as an example to illustrate.

[0117]

[0118] in:

[0119]

[0120]

[0121]

[0122] The formula for calculating the molar volume of the gas phase is similar to that for the molar volume of the liquid phase, except that x in the formula for calculating the molar volume of the liquid phase is replaced by i Replace with y i , x j Replace with y j In addition, T ri is the relative temperature of the i-th component.

[0123] The gas phase compressibility factor of the CO2 multicomponent system is calculated based on the pressure, temperature and gas phase molar volume of the CO2 multicomponent system.

[0124] The liquid phase compressibility factor of the CO2 multicomponent system is calculated based on the pressure, temperature and liquid phase molar volume of the CO2 multicomponent system.

[0125] The calculation formula for the above gas phase compressibility factor or liquid phase compressibility factor is:

[0126] Where R is the molar gas constant, k ij is the interaction coefficient between the i-th component and the j-th component.

[0127] (5) Calculate the gas phase fugacity coefficient and liquid phase fugacity coefficient of each component:

[0128]

[0129] Where, φ i is the gas phase fugacity coefficient or liquid phase fugacity coefficient of each component. When the gas phase physical property parameters are substituted, the gas phase fugacity coefficient is obtained, which is recorded as φ Vi , when the liquid phase physical property parameters are substituted, the liquid phase fugacity coefficient is obtained, which is recorded as φ Li ;

[0130] If the gas and liquid fugacity of each component are equal, then:

[0131] x i φ Li P=y i φ Vi P.

[0132] The gas and liquid reach equilibrium, and K i It is the gas-liquid equilibrium constant at the bubble point pressure and dew point pressure. If the gas and liquid fugacity of each component are not equal, K i The value is corrected to φ Li / φ Vi , repeat steps (2) to (5) until the gas phase and liquid phase fugacity of each component are equal.

[0133] (6) Calculate the pressure at the bubble point and convert the obtained K i Substitute into the following equation:

[0134]

[0135] If δ b >1, the given pressure is too low, and P is corrected to P+0.001; if δ b <1, the given pressure is too high, and P is corrected to P-0.001; when δb =1, the pressure P is the bubble point pressure value corresponding to the temperature T.

[0136] Calculate the pressure at the dew point and convert the obtained K i Substitute into the following equation:

[0137]

[0138] If δ d >1, the given pressure is too high, and P is corrected to P-0.001; if δ d <1, the given pressure is too low, and P is corrected to P+0.001; when δ d When =1, the pressure P is the dew point pressure value corresponding to the temperature T.

[0139] (7) Repeat steps (1) to (6) to calculate the bubble point pressure and dew point pressure of the CO2 multi-component system at different temperatures, draw the bubble point line and the dew point line, and the temperature and pressure corresponding to the intersection of the bubble point line and the dew point line are the critical points. Based on the calculation results, draw the PT phase diagram of the CO2 multi-component system within the pipeline temperature and pressure range.

[0140] Step 4: Divide the quasi-critical region of the CO2 multicomponent system

[0141] This step is the same as the process of determining the quasi-critical region described in the first embodiment, and will not be described in detail here.

[0142] The fifth step is to identify the phase state of the CO2 multicomponent system at different times along the pipeline.

[0143] Taking the bubble point line and dew point line as the boundaries, the PT phase diagram of the CO2 multi-component system is divided into the gas phase region (below the dew point line), the liquid phase region (above the bubble point line and below the critical pressure), the gas-liquid two-phase region (between the dew point line and the bubble point line), the dense phase region (above the critical pressure and below the critical temperature) and the supercritical phase region (above the critical temperature and above the critical pressure). Figure 2 shown.

[0144] The real-time monitored temperature and pressure data at different positions of the pipeline are plotted on the PT phase diagram, and the phase state of the CO2 multicomponent system is determined based on the area where the data points are located.

[0145] The sixth step is to issue an early warning for locations in the pipeline where phase change may occur.

[0146] If the monitoring data is always inside the gas phase area, liquid phase area and dense phase area (outside the quasi-critical area) of the PT phase diagram, the pipeline is in a safe operating state at this time; if the monitoring data deviates from the gas phase area, liquid phase area and dense phase area (outside the quasi-critical area) to the two-phase area or quasi-critical area, the parts of the pipeline where phase change may occur can be discovered through data screening, and early warnings can be issued for dangerous parts.

[0147] The present invention first tests the composition and physical properties of a CO2 multicomponent system, regresses and derives the binary interaction coefficients of each component. It then plots a PT phase diagram of the CO2 multicomponent system under pipeline transportation conditions and delineates quasi-critical regions. Finally, through data screening, the phase state of the CO2 multicomponent system along the pipeline is identified, and early warnings are issued for locations where phase transitions may occur. This invention converts real-time pipeline operating data into early warning signals, resolving the difficulty of traditional pipeline safety monitoring technologies in timely and accurate detection of CO2 pipeline operational anomalies. This allows for the immediate identification of potential hazards and the implementation of measures to ensure safe and efficient operation of the CO2 pipeline.

[0148] Example 3

[0149] In order to execute the corresponding method of the above-mentioned embodiment 1 and achieve the corresponding functions and technical effects, a phase state identification and early warning device for a carbon dioxide multi-component system under pipeline transportation conditions is provided below.

[0150] like Figure 4 As shown, the phase state identification and early warning device for the carbon dioxide multi-element system under the pipeline transportation condition includes:

[0151] The data acquisition module 1 is used to acquire temperature data and pressure data at different marked positions on the target CO2 pipeline during operation of the target CO2 pipeline.

[0152] Marking position phase state determination module 2, marking position phase state determination module, is used to determine the phase state of the CO2 multi-component system in the pipeline area where each marking position is located based on the CO2 multi-component system PT phase diagram within the pipeline temperature and pressure range, and the temperature data and pressure data at different marking positions; the horizontal axis of the CO2 multi-component system PT phase diagram is temperature, and the vertical axis of the CO2 multi-component system PT phase diagram is pressure; the temperature corresponding to the intersection of the bubble point line of the CO2 multi-component system PT phase diagram and the dew point line of the CO2 multi-component system PT phase diagram is the critical temperature. The critical temperature is obtained by measuring the pressure at which the bubble point line intersects the dew point line. The pressure corresponding to the intersection of the bubble point line and the dew point line is the critical pressure. The PT phase diagram of the CO2 multi-component system includes a gas phase region, a liquid phase region, a gas-liquid two-phase region, a dense phase region and a supercritical phase region. The gas phase region is the region below the dew point line, the liquid phase region is the region above the bubble point line and below the critical pressure line, the gas-liquid two-phase region is the region between the dew point line and the bubble point line, the dense phase region is the region above the critical pressure line and below the critical temperature line, and the supercritical phase region is the region above the critical temperature line and above the critical pressure line.

[0153] The phase state trend determination module 3 is used to summarize the phase states of the CO2 multi-component system in the pipeline area where all marked positions are located, and obtain the phase state trend of the CO2 multi-component system in the target CO2 pipeline area.

[0154] The dangerous state determination and early warning module 4 is used to determine that the target CO2 pipeline is in a dangerous state and perform an early warning operation when the phase trend of the CO2 multi-element system in the target CO2 pipeline area meets any constraint condition in the first constraint set; wherein the first constraint set includes the constraint condition of shifting from the inside of the gas phase region to the gas-liquid two-phase region, the constraint condition of shifting from the inside of the liquid phase region to the gas-liquid two-phase region, the constraint condition of shifting from the inside of the dense phase region to the gas-liquid two-phase region, the constraint condition of shifting from the inside of the gas phase region to the quasi-critical region, the constraint condition of shifting from the inside of the liquid phase region to the quasi-critical region, and the constraint condition of shifting from the inside of the dense phase region to the quasi-critical region; the quasi-critical region is divided according to the physical properties of the CO2 multi-element system in the supercritical state; the inside of the gas phase region is the region within the gas phase region excluding the quasi-critical region; the inside of the dense phase region is the region within the dense phase region excluding the quasi-critical region; the inside of the liquid phase region is the region within the liquid phase region excluding the quasi-critical region.

[0155] Furthermore, the phase state identification and early warning device for a carbon dioxide multi-component system under pipeline transportation conditions further includes:

[0156] A safety state determination module is configured to determine that the target CO2 pipeline is in a safe state when the phase trend of the CO2 multi-element system within the target CO2 pipeline area meets any constraint condition in a second constraint set; wherein the second constraint set includes constraints within the gas phase region, constraints within the liquid phase region, and constraints within the dense phase region.

[0157] Example 4

[0158] An embodiment of the present invention provides a phase state identification and early warning device for a carbon dioxide multi-component system under pipeline transportation conditions, comprising: a plurality of online monitoring devices, a signal receiving device connected to each of the online monitoring devices, and a data processing and analysis system connected to the signal receiving device; a plurality of marking positions are set along the target CO2 pipeline, and one of the online monitoring devices is installed at each marking position.

[0159] The signal receiving device is used to receive the temperature data and pressure data at the marked position on the target CO2 pipeline collected by each online monitoring device, and send them to the data processing and analysis system.

[0160] The data processing and analysis system is used to execute the phase state identification and early warning method for a carbon dioxide multi-component system under pipeline transportation conditions described in Example 1.

[0161] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0162] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for phase identification and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions, characterized in that: include: During the operation of the target CO2 pipeline, temperature data and pressure data at different marked positions on the target CO2 pipeline are obtained; According to the PT phase diagram of the CO2 multi-component system within the pipeline temperature and pressure range, and the temperature data and pressure data at different marked positions, the phase state of the CO2 multi-component system in the pipeline area where each marked position is located is determined; the horizontal axis of the PT phase diagram of the CO2 multi-component system is temperature, and the vertical axis of the PT phase diagram of the CO2 multi-component system is pressure; the temperature corresponding to the intersection of the bubble point line of the PT phase diagram of the CO2 multi-component system and the dew point line of the PT phase diagram of the CO2 multi-component system is the critical temperature, and the pressure corresponding to the intersection of the bubble point line and the dew point line is the critical pressure; the PT phase diagram of the CO2 multi-component system includes a gas phase region, a liquid phase region, a gas-liquid two-phase region, a dense phase region and a supercritical phase region; the gas phase region is the region below the dew point line, the liquid phase region is the region above the bubble point line and below the critical pressure line, the gas-liquid two-phase region is the region between the dew point line and the bubble point line, the dense phase region is the region above the critical pressure line and below the critical temperature line, and the supercritical phase region is the region above the critical temperature line and above the critical pressure line; The phase states of the CO2 multicomponent system in the pipeline area where all marked positions are located are summarized to obtain the phase state trend of the CO2 multicomponent system in the target CO2 pipeline area; When the phase trend of the CO2 multi-element system in the target CO2 pipeline area meets any constraint condition in the first constraint set, the target CO2 pipeline is determined to be in a dangerous state and an early warning operation is performed; wherein, the first constraint set includes constraints for shifting from the interior of the gas phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the liquid phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the dense phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the gas phase region to the quasi-critical region, constraints for shifting from the interior of the liquid phase region to the quasi-critical region, and constraints for shifting from the interior of the dense phase region to the quasi-critical region; the quasi-critical region is divided according to the physical properties of the CO2 multi-element system in the supercritical state; the interior of the gas phase region is the region within the gas phase region excluding the quasi-critical region; the interior of the dense phase region is the region within the dense phase region excluding the quasi-critical region; and the interior of the liquid phase region is the region within the liquid phase region excluding the quasi-critical region.

2. The method for phase identification and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions according to claim 1, characterized in that: Also includes: When the phase trend of the CO2 multi-element system in the target CO2 pipeline area meets any constraint condition in the second constraint set, it is determined that the target CO2 pipeline is in a safe state; wherein the second constraint set includes constraints within the gas phase region, constraints within the liquid phase region, and constraints within the dense phase region.

3. The method for phase identification and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions according to claim 1, characterized in that: The quasi-critical region is determined according to the following formula: The formula is: 0.8P c <P<2P c ; Where, P is the pressure corresponding to the quasi-critical region, T is the temperature corresponding to the quasi-critical region, and P c is the critical pressure of the CO2 multicomponent system, For CO2 multi-component system at 0.8P c Evaporation temperature under pressure, T pc is the critical temperature of the CO2 multicomponent system.

4. The method for phase identification and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions according to claim 1, characterized in that: The process of determining the PT phase diagram of the CO2 multicomponent system within the pipeline temperature and pressure range is as follows: Obtain the mole fraction and thermodynamic parameters of each component in a CO2 multicomponent system sample for pipeline transportation; According to the mole fraction and thermodynamic parameters of each component in the CO2 multi-component system sample and the PVT data of the CO2 multi-component system sample obtained by testing, the binary interaction coefficient of each component is regressed; The bubble point pressure and dew point pressure of CO2 multicomponent system samples at different temperatures are calculated based on the mole fraction, thermodynamic parameters and binary interaction coefficient of each component in the CO2 multicomponent system sample. Draw bubble point lines and dew point lines based on all bubble point pressures and all dew point pressures; Based on the bubble point line and dew point line, draw the PT phase diagram of the CO2 multicomponent system within the pipeline temperature and pressure range.

5. The method for phase identification and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions according to claim 4, characterized in that: The method of obtaining the mole fraction and thermodynamic parameters of each component in the CO2 multicomponent system sample for pipeline transportation specifically includes: Gas chromatography was used to obtain the mole fraction and thermodynamic parameters of each component in the CO2 multicomponent system sample for pipeline transportation.

6. The method for phase identification and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions according to claim 4, characterized in that: The method of regressing the binary interaction coefficient of each component based on the mole fraction and thermodynamic parameters of each component in the CO2 multi-component system sample and the PVT data of the CO2 multi-component system sample obtained by testing specifically includes: Select m test points and use a PVT high-pressure physical property analyzer to obtain PVT data of the CO2 multi-component system sample in a gas phase or liquid phase at each test point; the PVT data includes temperature, pressure and specific volume; The mole fractions and thermodynamic parameters of each component in the CO2 multicomponent system sample, as well as the temperature, pressure, and specific volume of each test point, were substituted into the Peng-Robinson equation of state. The equation coefficients corresponding to each test point were calculated, and the expressions of the equation coefficients were transformed according to the van der Waals mixing rule to obtain an overdetermined ill-conditioned linear system of equations. The singular value decomposition method is used to solve the overdetermined ill-conditioned linear equations and obtain the least squares solution of the binary interaction coefficients of each component.

7. The method for phase identification and early warning of a carbon dioxide multicomponent system under pipeline transportation conditions according to claim 4, characterized in that: The calculation of the bubble point pressure and dew point pressure of the CO2 multicomponent system sample at different temperatures based on the mole fraction, thermodynamic parameters and binary interaction coefficient of each component in the CO2 multicomponent system sample specifically includes: According to the determined pressure, temperature, and the mole fraction, thermodynamic parameters and binary interaction coefficient of each component in the CO2 multicomponent system sample, the Wilson formula and the Peng-Robinson equation of state are used to calculate the gas phase fugacity coefficient and liquid phase fugacity coefficient of each component in the CO2 multicomponent system sample, and the bubble point pressure and dew point pressure are calculated based on the gas-liquid equilibrium constant when the gas phase fugacity coefficient and the liquid phase fugacity coefficient are the same. Then, the pressure and temperature are changed and the above steps are repeated to calculate the bubble point pressure and dew point pressure of the CO2 multicomponent system sample at different temperatures.

8. A phase state identification and early warning device for a carbon dioxide multicomponent system under pipeline transportation conditions, characterized in that: include: A data acquisition module is used to acquire temperature data and pressure data at different marked positions on the target CO2 pipeline during its operation; a marked position phase state determination module, for determining the phase state of the CO2 multi-component system in the pipeline area where each marked position is located based on the CO2 multi-component system PT phase diagram within the pipeline temperature and pressure range, and the temperature data and pressure data at different marked positions; the horizontal axis of the CO2 multi-component system PT phase diagram is temperature, and the vertical axis of the CO2 multi-component system PT phase diagram is pressure; the temperature corresponding to the intersection of the bubble point line of the CO2 multi-component system PT phase diagram and the dew point line of the CO2 multi-component system PT phase diagram is the critical temperature, and the pressure corresponding to the intersection of the bubble point line and the dew point line is the critical pressure; the CO2 multi-component system PT phase diagram includes a gas phase region, a liquid phase region, a gas-liquid two-phase region, a dense phase region and a supercritical phase region; the gas phase region is the region below the dew point line, the liquid phase region is the region above the bubble point line and below the critical pressure line, the gas-liquid two-phase region is the region between the dew point line and the bubble point line, the dense phase region is the region above the critical pressure line and below the critical temperature line, and the supercritical phase region is the region above the critical temperature line and above the critical pressure line; The phase state trend determination module is used to summarize the phase states of the CO2 multi-element system in the pipeline area where all marked positions are located, and obtain the phase state trend of the CO2 multi-element system in the target CO2 pipeline area; A dangerous state determination and early warning module is used to determine that the target CO2 pipeline is in a dangerous state and perform an early warning operation when the phase trend of the CO2 multi-component system in the target CO2 pipeline area meets any constraint condition in a first constraint set; wherein the first constraint set includes constraints for shifting from the interior of the gas phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the liquid phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the dense phase region to the gas-liquid two-phase region, constraints for shifting from the interior of the gas phase region to the quasi-critical region, constraints for shifting from the interior of the liquid phase region to the quasi-critical region, and constraints for shifting from the interior of the dense phase region to the quasi-critical region; the quasi-critical region is divided according to the physical properties of the CO2 multi-component system in a supercritical state; the interior of the gas phase region is the region within the gas phase region excluding the quasi-critical region; the interior of the dense phase region is the region within the dense phase region excluding the quasi-critical region; and the interior of the liquid phase region is the region within the liquid phase region excluding the quasi-critical region.

9. The device for phase identification and early warning of a carbon dioxide multi-component system under pipeline transportation conditions according to claim 8, characterized in that: Also includes: A safety state determination module is configured to determine that the target CO2 pipeline is in a safe state when the phase trend of the CO2 multi-element system within the target CO2 pipeline area meets any constraint condition in a second constraint set; wherein the second constraint set includes constraints within the gas phase region, constraints within the liquid phase region, and constraints within the dense phase region.

10. A phase state identification and early warning device for a carbon dioxide multicomponent system under pipeline transportation conditions, characterized in that: include: A plurality of online monitoring devices, a signal receiving device connected to each of the online monitoring devices, and a data processing and analysis system connected to the signal receiving device; exist A plurality of marking positions are set along the target CO2 pipeline, and one of the online monitoring devices is installed at each marking position; The signal receiving device is used to receive the temperature data and pressure data at the marked position on the target CO2 pipeline collected by each online monitoring device, and send them to the data processing and analysis system; The data processing and analysis system is used to execute the phase state identification and early warning method for a carbon dioxide multicomponent system under pipeline transportation conditions as described in any one of claims 1 to 7.

Images