Impurity-containing CO2 pipeline transient flow simulation method

Abstract

The invention provides an impurity-containing CO2 pipeline transient flow simulation method which comprises the following steps: firstly, introducing a state equation, and initializing thermophysical parameters of impurity-containing CO2; then under a finite volume method framework, establishing an impurity-containing CO2 two-phase flow transient control equation and a mass source item, and determining a computational domain, an initial value condition and a boundary condition; thirdly, discretizing a control equation on the staggered grid, adopting a first-order implicit format for a time item, and adopting a second-order windward format for a space item; then, an SIMPLECST algorithm is adopted to solve a transient control equation of the impurity-containing CO2 two-phase flow dispersed on the staggered grids; and finally, outputting a solving result of the SIMPLECST algorithm. According to the method, the momentum conservation equation is solved through point iteration, and the influence of adjacent point coefficients on the convergence process is considered again, so that the calculation speed of the SIMPLECST algorithm is higher and more stable. The method provided by the invention can accurately simulate transient flow in the impurity-containing CO2 pipeline, and in addition, the method can also be expanded and applied to prediction of flow parameters of pure CO2, natural gas condensate, LNG, wet natural gas and the like.

Description

Technical Field

[0001] The present invention relates to a method for preparing a carbon monoxide containing impurities 2 The invention discloses a pipeline transient flow simulation method, belonging to the field of multiphase flow simulation. Background Art

[0002] Over the past few decades, the burning of fossil fuels has led to a massive accumulation of greenhouse gases, including CO 2 Currently, reducing CO 2 Carbon capture, utilization and storage is a key strategy in the plan and to achieve this goal, millions of tonnes of CO2 must be captured and stored each year. 2 Due to CO 2 Capture facilities and storage locations are often not in the same place, so it needs to be transported by pipeline, ship or rail, with pipeline transportation considered the safest, most sustainable and cost-effective option.

[0003] CO 2 Pipeline transportation can be divided into three types: gas phase, liquid phase and supercritical phase transportation, among which supercritical transportation is the most common transportation method. 2 With high density and low viscosity, it is conducive to transporting larger volumes while minimizing the energy consumption of transportation. 2 During the transportation process, the pressure in the pipeline must always be kept greater than the critical pressure to prevent CO from appearing in the pipeline. 2 Gas-liquid two-phase flow. However, in actual operation, pipeline conditions may deviate from the designed supercritical conditions. For example, in long-distance CO 2 In pipelines, CO is easily generated due to friction pressure drop along the line and heat exchange with the environment. 2 Two-phase flow significantly increases the energy consumption of transportation. In addition, the CO 2 May contain impurities, which are generally N 2 , H 2 , CO, CH 4 , C 2 H 6 , O 2 , H 2 S. SO 2 and H 2 O, etc. CO containing impurities 2 This will cause changes in its physical properties and phase characteristics, mainly manifested in the upward movement of the bubble point line and the expansion of the gas-liquid two-phase region. At the same time, the mutation positions of parameters such as density, viscosity, and specific heat capacity will shift, further increasing the concentration of impurities in CO 2 Therefore, developing a suitable flow model is very important for accurately predicting the flow parameters of impurities in CO. 2Flow parameters in the pipeline to ensure the presence of impurities in CO 2 Pipeline transportation safety is of vital importance.

[0004] For gas-liquid two-phase flow, the commonly used model is the classical two-fluid model. However, the classical two-fluid model is proposed for incompressible fluids, while the impurity CO 2 It is compressible, so the impure CO must be coupled in the two-fluid model. 2 The calculation method of thermophysical parameters accurately describes the impurity-containing CO 2 On the other hand, the mass source term describing the gas-liquid phase transition in the classic two-fluid model is also proposed for air and water, and cannot be directly used for impure CO 2 Two-phase flow. In addition, the method for solving the two-fluid model is generally the SIMPLE algorithm. Patent CN 111400950A uses the SIMPLE algorithm to solve the two-fluid model of the hydrate slurry multiphase pipeline, and the model has first-order accuracy. However, the convergence speed of the algorithm is slow, and when the parameters along the pipeline vary greatly, numerical oscillations may occur. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a CO 2 The pipeline transient flow simulation method is based on the finite volume method and introduces impurity CO 2 The state equation and mass source term provide a simulation method with simple algorithm, fast convergence and high-order accuracy.

[0006] The present invention is achieved through the following technical solutions:

[0007] Step 1: Introduce the state equation and initialize the impure CO 2 Physical properties of the material, including density, viscosity, gas-liquid mass fraction, etc.

[0008] Step 2: construct the impure CO 2 Two-phase flow transient control equations and mass source terms, determine the calculation domain, initial value conditions and boundary conditions according to the actual working conditions of the simulation;

[0009] Step 3: Under the framework of the finite volume method, the pipeline calculation domain is divided by staggered grids, the first-order implicit format is used for the transient term, and the second-order upwind format is used for the spatial term to construct the impure CO 2 Discrete momentum equation, pressure correction equation, phase fraction correction equation and temperature correction equation for two-phase flow;

[0010] Step 4: Use the SIMPLECST algorithm to solve the impure CO after the staggered grid is established in step 3. 2 Transient governing equations for two-phase flow;

[0011] Step 5: Output the solution results of the SIMPLECST algorithm, including pressure, temperature, liquid holdup, gas mass flow rate, liquid mass flow rate, etc.

[0012] In step 1, further technical solutions include the following:

[0013] S11, the impurities include N 2 , H 2 , CO, CH 4 , C 2 H 6 , O 2 , H 2 S. SO 2 and H 2 O;

[0014] S12, the state equation is the PR state equation, and the expression of the PR state equation is:

[0015]

[0016] Where T is temperature, K; R is gas constant, J / (kg·K); v is specific volume, m 3 / kg; d, b, δ are defined as follows,

[0017]

[0018]

[0019]

[0020] Where, T c is the critical temperature, K; P c is the critical pressure, Pa; ω is the eccentricity factor.

[0021] In step 2, further technical solutions include the following:

[0022] S21, the impurity-containing CO 2 The transient control equations of two-phase flow include the mass conservation equation, momentum conservation equation and energy conservation equation. The mass conservation equation is shown in equation (5):

[0023]

[0024] The momentum conservation equation is shown in equation (6):

[0025]

[0026] The energy conservation equation is shown in equation (7):

[0027]

[0028] Where k is the gas phase or liquid phase, k = g, l; m is the mixture; ρ is the density, kg / m 3 ; x is the transverse length of the pipeline, m; t is time, s; α is the phase fraction; u is the flow rate, m / s; P is the pressure, Pa; is the mass source term, kg / (m 3 ·s); g is the acceleration due to gravity, m 2 / s; θ is the pipeline inclination, rad; τ w is the shear stress of the tube wall, Pa; S w is the wetted perimeter of the phase in contact with the wall, m; u i is the gas-liquid interface velocity, m / s; A p is the cross-sectional area of ​​the pipe, m 2 ;D h is the pipe diameter, m; ΔP is the additional term, Pa; T is the temperature, K; h is the enthalpy, J / kg; e is the internal energy of the fluid, J / kg; Q is the heat loss of the fluid per unit mass, J / kg; C P is the specific heat capacity at constant pressure, J / kg·K; D i is the Joule-Thomson coefficient, K / Pa; K is the total heat transfer coefficient, W / (m 2 ·K); T a is the ambient temperature, K;

[0029] S22, the impurity-containing CO 2 The mass source term for two-phase flow is,

[0030]

[0031] In the formula, m gin is the gas mass flow rate flowing into the control body, kg / s; m gout is the gas mass flow rate out of the control body, kg / s; m g is the mass flow rate of gas phase, kg / s; m l is the mass flow rate of the liquid phase, kg / s; m tot is the total mass flow rate flowing into the pipeline, kg / s; w g is the mass fraction of the gas phase at equilibrium;

[0032] S23, the calculation domain is the total length of the pipeline; the initial value conditions are the basic parameter values ​​such as pressure, temperature, mass flow rate, etc. in the pipeline calculation domain under the initial conditions (t=0); the boundary conditions include the mass flow rate and temperature at the pipeline inlet and the pressure at the pipeline outlet.

[0033] In step 3, a further technical solution includes the following:

[0034] S31, the staggered grid stores scalars (pressure, temperature, density, viscosity, etc.) on the main grid nodes and stores velocities (gas phase velocity, liquid phase velocity) on the secondary grid nodes, and the secondary grid nodes are located on the main grid interface, thereby dislocating the grid;

[0035] S32, the transient term adopts the first-order implicit format, and the spatial term adopts the second-order upwind format to construct the impurity CO 2 The discrete momentum equation, pressure correction equation, phase fraction correction equation and temperature correction equation of two-phase flow include: The discrete momentum conservation equation:

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] The discretized pressure correction equation is:

[0044] A E P′ E +A P P′ P +A W P′ W =B m+1 (16)

[0045]

[0046]

[0047]

[0048]

[0049] The phase fraction correction equation after discretization is:

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] The discretized temperature correction equation is:

[0056]

[0057]

[0058]

[0059]

[0060]

[0061] Where m is the number of outer iterations; n is the number of time layers; subscripts w and e represent secondary grid nodes; subscripts WW, W, P, E, and EE represent primary grid nodes, and the meanings of other parameters are consistent with the previous text.

[0062] In step 4, a further technical solution includes the following:

[0063] S41, the momentum equation iteration method of the SIMPLECST algorithm is point iteration. Compared with the SIMPLE algorithm, the point iteration method has stronger convergence stability in solving the momentum equation. Its expression is as follows:

[0064]

[0065] Where, κ is the number of inner iterations; φ u is the sub-relaxation coefficient of the momentum equation; a k,nb is the connectivity coefficient of neighboring points.

[0066] S42, the speed correction equation of the SIMPLECST algorithm is:

[0067]

[0068] Compared with SIMPLE algorithm, SIMPLECST algorithm reconsiders the influence of neighboring coefficients of momentum equation on convergence process during speed correction, which makes SIMPLECST algorithm converge faster than SIMPLE algorithm.

[0069] S43, SIMPLECST algorithm to solve the impurity CO 2 The steps of the transient control equation of two-phase flow are to solve the discretized momentum conservation equation by point iteration to obtain the gas-liquid phase velocity;

[0070] S44, substituting the gas-liquid phase velocity into the pressure correction equation to obtain a corrected pressure and a corrected gas-liquid phase velocity;

[0071] S45, substituting the corrected pressure and the corrected gas-liquid phase velocity into the phase fraction correction equation to obtain a corrected phase fraction;

[0072] S46, substitute the corrected pressure, gas-liquid phase velocity and phase fraction into the temperature correction equation to obtain the corrected temperature. When the convergence condition is met, the algorithm terminates; when the convergence condition is not met, all values ​​are re-substituted into the discretized momentum conservation equation, and the above process is repeated until the convergence condition is met.

[0073] The beneficial features of the present invention are:

[0074] (1) Achieved the use of impure CO 2 The present invention provides a pipeline transient flow simulation. 2 The pipeline transient flow simulation method is based on the finite volume method and introduces the impure CO 2 The state equation and mass source term can accurately describe the impure CO 2 The variation law of flow parameters in the pipeline is that the impurity CO 2 The production operation of the pipeline provides data reference.

[0075] (2) A new two-fluid model solution algorithm is proposed. Based on the traditional SIMPLE algorithm, the present invention proposes a new SIMPLECST algorithm. When solving the momentum conservation equation, point iteration is used to enhance the solution stability. At the same time, the influence of neighboring point coefficients on the convergence process is considered to accelerate the convergence process. Compared with the traditional SIMPLE algorithm, the SIMPLECST algorithm has stronger stability and faster convergence.

[0076] (3) Applicable to a variety of fluids. The two-phase flow simulation method of the present invention can be used for impure CO 2 The prediction of two-phase flow parameters can also be applied to pure CO 2 , natural gas condensate, LNG, wet natural gas and other flow parameters prediction, with a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0078] Figure 1 is a basic flow chart of the present invention;

[0079] Figure 2 It is a schematic diagram of the calculation domain, initial conditions and boundary conditions of the present invention;

[0080] Figure 3 It is a schematic diagram of staggered grids under the framework of the finite volume method of the present invention;

[0081] Figure 4 It is a flow chart of the SIMPLECST algorithm of the present invention;

[0082] Figure 5 The impurity CO in the embodiment of the present invention 2 Pipeline elevation data;

[0083] Figure 6 The impurity CO in the embodiment of the present invention 2 Pressure prediction results of pipeline transient simulation;

[0084] Figure 7 The impurity CO in the embodiment of the present invention 2 Temperature prediction results of pipeline transient simulation;

[0085] Figure 8 The impurity CO in the embodiment of the present invention 2 Liquid holdup prediction results from pipeline transient simulation;

[0086] Fig. 9 The impurity CO in the embodiment of the present invention 2 Gas phase mass flow prediction results of pipeline transient simulation;

[0087] Fig.10 The impurity CO in the embodiment of the present invention 2 Liquid mass flow prediction results of pipeline transient simulation;

[0088] Fig.11 The impurity CO in the embodiment of the present invention 2 Comparison of the computational time of SIMPLECST algorithm and SIMPLE algorithm for pipeline transient simulation. DETAILED DESCRIPTION

[0089] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be fully described below in conjunction with the drawings in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0090] like Figure 1 As shown, a CO 2The pipeline transient flow simulation method includes the following steps:

[0091] Step 1: Introduce the PR state equation and initialize the impure CO 2 Thermophysical parameters, including density, viscosity, gas-liquid mass fraction, etc.

[0092] Step 2: Establish the impure CO 2 The transient control equations and mass source terms of two-phase flow are used to determine the calculation domain, initial value conditions and boundary conditions according to the actual working conditions of the simulation. The calculation domain, initial value conditions and boundary conditions of the pipeline are shown in Figure 2 ;

[0093] Step 3: Under the framework of the finite volume method, the pipeline calculation domain is divided using staggered grids. Figure 3 For the transient terms, the first-order implicit format is used, and for the spatial terms, the second-order upwind format is used to construct the impure CO 2 Discrete momentum equation, pressure correction equation, phase fraction correction equation and temperature correction equation for two-phase flow;

[0094] Step 4: Use the SIMPLECST algorithm to solve the impure CO after the staggered grid is established in step 3. 2 The two-phase flow transient control equations, the SIMPLECST algorithm solution steps are shown in Figure 4 ;

[0095] Step 5: Output the solution results of the SIMPLECST algorithm, including pressure, temperature, liquid holdup, gas mass flow rate, liquid mass flow rate, etc. Specific embodiments

[0097] There is a line containing impurities CO 2 The pipeline is 144km long and 610mm in diameter. The terrain along the route is undulating. See the elevation data for details. Figure 5 , the ambient temperature is 5°C, the inlet mass flow rate is 5kg / s, the inlet temperature is 15°C, the inlet fluid composition is shown in Table 1, and the outlet pressure is 6.0MPa. Due to an accident in the downstream, the pressure at the pipeline outlet suddenly dropped from 6.0MPa to 4.0MPa. The flow parameters of the pipeline are now calculated according to the method of the present invention.

[0098] Table 1 Pipeline fluid composition (mol%)

[0099] <![CDATA[CO 2 ]]> 91.83 <![CDATA[N 2 ]]> 5.11 <![CDATA[H 2 S]]> 3.06

[0100] The implementation steps are as follows:

[0101] Step 1: Introduce the PR state equation and initialize the impure CO 2Thermophysical parameters of impurity CO include density, viscosity and gas-liquid mass fraction. 2 The thermal properties of the samples are shown in Table 2.

[0102] Table 2 Contains impurities CO 2 Thermophysical parameters

[0103]

[0104]

[0105] Step 2: Establishment of impure CO 2 The two-phase flow transient control equation and the mass source term are determined according to the actual working conditions of the simulation. The calculation domain is 144 km long and the calculation domain step is 100 m. The initial value conditions and boundary conditions are set according to the given values ​​of the embodiment.

[0106] Step 3: Under the framework of the finite volume method, the pipeline calculation domain is divided by staggered grids. For transient terms, the first-order implicit format is used, and for spatial terms, the second-order upwind format is used to construct the impure CO 2 Discrete momentum equation, pressure correction equation, phase fraction correction equation and temperature correction equation for two-phase flow;

[0107] S31, storing the scalars (pressure, temperature, density and other parameters) of the embodiment in the main grid; storing the speed of the embodiment in the secondary grid;

[0108] S32, the momentum conservation equation after discretization is:

[0109]

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] The discretized pressure correction equation is:

[0117] A E P′ E +A P P′ P +A W P′W =B m+1 (40)

[0118]

[0119]

[0120]

[0121]

[0122] The phase fraction correction equation after discretization is:

[0123]

[0124]

[0125]

[0126]

[0127]

[0128] The discretized temperature correction equation is:

[0129]

[0130]

[0131]

[0132]

[0133]

[0134] Step 4: Use the SIMPLECST algorithm to solve the impure CO after the staggered grid is established in step 3. 2 Transient governing equations for two-phase flow.

[0135] S41, the point iteration method is used to solve the momentum conservation equation, the expression is as follows:

[0136]

[0137] S42, calculate the speed correction value using the following formula:

[0138]

[0139] S43, using point iteration to solve the discretized momentum conservation equation to obtain the gas-liquid phase velocity;

[0140] S44, substituting the gas-liquid phase velocity into the pressure correction equation to obtain a corrected pressure and a corrected gas-liquid phase velocity;

[0141] S45, substituting the corrected pressure and the corrected gas-liquid phase velocity into the phase fraction correction equation to obtain a corrected phase fraction;

[0142] S46, substitute the corrected pressure, gas-liquid phase velocity and phase fraction into the temperature correction equation to obtain the corrected temperature. When the convergence condition is met, the algorithm terminates; when the convergence condition is not met, all values ​​are re-substituted into the discretized momentum conservation equation, and the above process is repeated until the convergence condition is met.

[0143] Step 5: Output the solution results of the SIMPLECST algorithm, including pressure, temperature, liquid holdup, gas mass flow rate, liquid mass flow rate, etc.

[0144] By using the method in step 1 to step 5, the impurity CO 2 In the pipeline, accurate prediction results of parameters such as pressure, temperature, gas mass flow rate, liquid mass flow rate and liquid holdup are obtained.

[0145] like Figure 6 to Figure 10 As shown in Figure 1, the pressure, temperature, liquid holdup, gas mass flow rate and liquid mass flow rate along the pipeline change with time within 44.4 hours (160,000 seconds) after the pipeline pressure is reduced. Fig.11 As shown in the figure, the calculation speed of SIMPLECST algorithm is faster under the same pipeline unit length.

[0146] From the above description, it can be seen that this embodiment is based on a CO 2 The pipeline transient flow simulation method realizes the 2 The transient simulation of the pipeline can accurately calculate the key parameters such as pressure, temperature, liquid holdup, gas mass flow rate and liquid mass flow rate along the pipeline, and accurately predict the possible CO 2 Two-phase flow, and the calculation speed is faster than the traditional SIMPLE algorithm. In summary, the present invention is effective in ensuring the safety of CO containing impurities. 2 Efficient pipeline transportation and the promotion of the development of carbon capture, utilization and storage technologies are of great significance.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for simulating transient flow of a CO2 pipeline containing impurities, characterized in that: The following steps are involved: Step 1, introduce the state equation and initialize the physical property parameters of impure CO2, including density, viscosity, gas-liquid phase mass fraction, etc.; Step 2: Under the framework of the finite volume method, the transient control equations and mass source terms of the two-phase flow of CO2 containing impurities are constructed, and the calculation domain, initial value conditions and boundary conditions are determined according to the actual working conditions of the simulation; Step 3: Under the framework of the finite volume method, the pipeline calculation domain is divided by staggered grids, the first-order implicit format is used for the transient terms, and the second-order upwind format is used for the spatial terms to construct the discrete momentum equation, pressure correction equation, phase fraction correction equation, and temperature correction equation for the two-phase flow of CO2 containing impurities; Step 4, using the SIMPLECST algorithm to solve the transient control equation of the two-phase flow of CO2 containing impurities after the staggered grid is established in step 3; Step 5: Output the solution results of the SIMPLECST algorithm, including pressure, temperature, liquid holdup, gas mass flow rate, liquid mass flow rate, etc.

2. A method for simulating transient flow of a CO2 pipeline containing impurities as claimed in claim 1, characterized in that: The step 1 includes the following contents: S11, the impurities include N2, H2, CO, CH4, C2H6, O2, H2S, SO2 and H2O; S12, the state equation is the PR state equation, and the expression of the PR state equation is: Where T is temperature, K; R is gas constant, J / (kg·K); v is specific volume, m 3 / kg; d, b, δ are defined as follows, Where, T c is the critical temperature, K; P c is the critical pressure, Pa; ω is the eccentricity factor.

3. A method for simulating transient flow of a CO2 pipeline containing impurities as claimed in claim 1, characterized in that: The step 2 includes the following contents: S21, the transient control equations of the impure CO2 two-phase flow include the mass conservation equation, the momentum conservation equation and the energy conservation equation; the mass conservation equation is shown in equation (5): The momentum conservation equation is shown in equation (6): The energy conservation equation is shown in equation (7): In the formula, k is the gas phase or liquid phase, k = g, l; m is the mixture; ρ is density, kg / m 3 ; x is the transverse length of the pipeline, m; t is time, s; α is phase fraction; u is flow velocity, m / s; P is pressure, Pa; is the mass source term, kg / (m 3 ·s); g is the acceleration due to gravity, m 2 / s; θ is the pipeline inclination, rad; τ w is the shear stress of the tube wall, Pa; S w is the wetted perimeter of the phase in contact with the wall, m; u i is the gas-liquid interface velocity, m / s; A p is the cross-sectional area of ​​the pipe, m 2 ;D h is the pipe diameter, m; ΔP is the additional term, Pa; T is the temperature, K; h is the enthalpy, J / kg; e is the internal energy of the fluid, J / kg; Q is the heat loss of the fluid per unit mass, J / kg; C P is the specific heat capacity at constant pressure, J / kg·K; D i is the Joule-Thomson coefficient, K / Pa; K is the total heat transfer coefficient, W / (m 2 ·K); T a is the ambient temperature, K; S22, the mass source term of the impure CO2 two-phase flow is: In the formula, m gin is the gas mass flow rate flowing into the control body, kg / s; m gout is the gas mass flow rate out of the control body, kg / s; m g is the mass flow rate of gas phase, kg / s; m l is the mass flow rate of the liquid phase, kg / s; m tot is the total mass flow rate flowing into the pipeline, kg / s; w g is the mass fraction of the gas phase at equilibrium; S23, the calculation domain is the total length of the pipeline; the initial value conditions are the basic parameter values ​​such as pressure, temperature, mass flow rate, etc. in the pipeline calculation domain under the initial conditions (t=0); the boundary conditions include the mass flow rate and temperature at the pipeline inlet and the pressure at the pipeline outlet.

4. A method for simulating transient flow of a CO2 pipeline containing impurities as claimed in claim 1, characterized in that: The step 3 includes the following contents: S31, the staggered grid stores scalars (pressure, temperature, density, viscosity, etc.) on the main grid nodes and stores velocities (gas phase velocity, liquid phase velocity) on the secondary grid nodes, and the secondary grid nodes are located on the main grid interface, thereby dislocating the grid; S32, the first-order implicit format is used for the transient term, and the second-order upwind format is used for the spatial term to construct the discrete momentum equation, pressure correction equation, phase fraction correction equation and temperature correction equation of the impure CO2 two-phase flow, including: the momentum conservation equation after discretization: The discretized pressure correction equation is: A E P E ′+A P P P ′+A W P W ′ W =B m+1 (16) The phase fraction correction equation after discretization is: The discretized temperature correction equation is: Where m is the number of outer iterations; n is the number of time layers; subscripts w and e represent secondary grid nodes; subscripts WW, W, P, E, and EE represent primary grid nodes, and the meanings of other parameters are consistent with the previous text.

5. The method for simulating transient flow of a CO2 pipeline containing impurities as claimed in claim 1, characterized in that: The step 4 includes the following contents: S41, the momentum equation iteration method of the SIMPLECST algorithm is point iteration, and its expression is as follows: Where, κ is the number of inner iterations; φ u is the sub-relaxation coefficient of the momentum equation; a k,nb is the connection coefficient of neighboring points; S42, the speed correction equation of the SIMPLECST algorithm is: S43, the steps of solving the transient control equation of the two-phase flow of CO2 containing impurities by the SIMPLECST algorithm are to solve the discretized momentum conservation equation by point iteration to obtain the gas-liquid phase velocity; S44, substituting the gas-liquid phase velocity into the pressure correction equation to obtain a corrected pressure and a corrected gas-liquid phase velocity; S45, substituting the corrected pressure and the corrected gas-liquid phase velocity into the phase fraction correction equation to obtain a corrected phase fraction; S46, substituting the corrected pressure, gas-liquid phase velocity and phase fraction into the temperature correction equation to obtain a corrected temperature; When the convergence condition is met, the algorithm terminates; When the convergence condition is not met, all values ​​are re-substituted into the discretized momentum conservation equation and the above process is repeated until the convergence condition is met.

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