Hydrate formation prediction method and system for supercritical carbon dioxide transmission pipeline containing impurities

Abstract

The application discloses a hydrate generation prediction method and system for a supercritical carbon dioxide pipeline containing impurities, and comprises the following steps: considering heat exchange between a pipeline and the surrounding environment and distribution of water droplets in the pipeline, considering hydrate generation thermodynamic factors, determining phase equilibrium parameters of hydrate generation in carbon dioxide containing impurities by using a Chen-Guo hydrate generation model, and determining a hydrate generation position in combination with a pipeline temperature-pressure distribution; calculating a volume of carbon dioxide hydrate particles according to a sum of a volume of the water droplets and a volume of a hydrate film covering the water droplets, considering hydrate growth kinetics factors, the volume of the hydrate film being related to a lateral growth rate and thickness of the hydrate film, the lateral growth rate being determined by using a comprehensive growth model, and the thickness growth of the hydrate film being analogous to condensation heat transfer; and predicting a generation amount of the hydrate particles in the pipeline in combination with distribution characteristics of the water droplets in the pipeline. The application realizes prediction of the hydrate generation position and the generation amount in the pipeline.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide transportation, and in particular relates to a method and system for predicting hydrate formation in a supercritical carbon dioxide transportation pipeline containing impurities. Background Art

[0002] Carbon dioxide (CO2) transportation is a key link connecting upstream and downstream in the CCUS industry chain. Pipeline transportation has good economic benefits. According to the transportation phase, CO2 pipeline transportation is generally divided into three modes of transportation: gas phase transportation, liquid phase transportation and supercritical dense phase transportation. During the transportation of supercritical CO2, as the pressure and temperature of CO2 decrease, the phase of CO2 will change from supercritical state to dense phase (when the pressure is above the critical pressure). The temperature and pressure of supercritical CO2 are both higher than the critical point (critical pressure 7.38MPa, critical temperature 31.4℃), the pressure of dense phase CO2 is higher than the critical pressure and the temperature is lower than the critical temperature, such as Figure 2 As shown. Supercritical CO2 combines the low viscosity and high fluidity of a gas with the high density of a liquid, making supercritical CO2 pipelines capable of transporting more CO2 than both gas and liquid CO2 pipelines. Furthermore, CO2 pressure fluctuations can easily lead to two-phase flow in gas or liquid CO2 pipelines, resulting in discontinuous flow. However, when CO2 transitions from supercritical to dense phase, two-phase flow does not occur, thus avoiding safety issues associated with two-phase flow. Therefore, supercritical-dense phase CO2 pipeline transportation is the most suitable method for large-scale, long-distance CO2 transportation in engineering projects.

[0003] Transported CO2 typically contains impurities (usually less than 5%) such as H2O, CH4, N2, H2, and CH3OH. These impurities significantly affect the physical properties of CO2. The presence of water can also lead to the formation of CO2 hydrates in dense phase pipelines. CO2 hydrates are non-stoichiometric crystalline solids formed by the guest molecule CO2 filling the cage-like pores formed by hydrogen bonds between water molecules. Hydrate particles deposit and block the flow cross-section, promoting the formation of more hydrates, creating a serious risk of pipeline blockage, leading to unstable transportation conditions, and increasing the risk of pipeline explosions and even outages. Furthermore, hydrates in pipelines can easily cause localized corrosion and generalized corrosion by carbonic acid, which can lead to pore leaks. Leaks of high-concentration, high-pressure CO2 can damage the ecological environment surrounding the pipeline and pose a suffocation hazard to people and animals near the leak point. Hydrate formation in transmission pipelines results in billions of dollars in economic losses annually. Therefore, accurately predicting hydrate formation in supercritical CO2 transmission pipelines is of great significance.

[0004] At present, scholars judge whether hydrate is generated at a specific temperature and pressure through a hydrate generation thermodynamic model, the method is simple to predict, but can only roughly predict the generation region of hydrate, and cannot predict the generation amount of hydrate. Some scholars use population balance theory, probability model and other big data methods to predict the deposition amount of hydrate, and the method needs a large amount of operation data to train the prediction model, and is inconvenient to use. SUMMARY

[0005] In view of the defects of the prior art, the application provides a hydrate generation prediction method and system for an impurity-containing supercritical carbon dioxide conveying pipeline. The application takes the impurity-containing supercritical carbon dioxide conveying pipeline as the object, adopts a theoretical analysis method, combines hydrate generation thermodynamics and kinetics factors, considers heat exchange between the pipeline and the surrounding environment and distribution of water droplets in the pipeline, and realizes prediction of hydrate generation position and generation amount in the pipeline. First, the hydrate generation thermodynamic factor is considered, the Chen-Guo hydrate generation model is used to determine the phase equilibrium parameters of hydrate generation in the impurity-containing carbon dioxide, and the hydrate generation position is determined in combination with the temperature-pressure distribution of the pipeline. Second, the volume of carbon dioxide hydrate particles is calculated according to the sum of the volume of water droplets and the volume of hydrate membranes covering the water droplets, the hydrate growth kinetics factor is considered, the volume of the hydrate membrane is related to the lateral growth rate and thickness of the hydrate membrane, the lateral growth rate is determined by using a comprehensive growth model, and the thickness growth of the hydrate membrane is analogous to condensation heat transfer. Finally, the generation amount of hydrate particles in the pipeline is predicted in combination with the distribution characteristics of water droplets in the pipeline.

[0006] In order to achieve the above purpose, the application adopts the following technical solutions:

[0007] The hydrate generation prediction method for the impurity-containing supercritical carbon dioxide conveying pipeline comprises the following steps.

[0008] Step 1: determining the phase equilibrium parameters of hydrate generation in the impurity-containing carbon dioxide according to the Chen-Guo hydrate generation model;

[0009] Step 2: preliminarily determining the temperature-pressure distribution of the pipeline at the initial time according to the pipeline specification parameters, flow parameters and fluid components;

[0010] Step 3: determining the position of hydrate generation in the pipeline in combination with the hydrate generation phase equilibrium parameters and the temperature-pressure distribution of the pipeline; when the temperature of the fluid in the pipeline is higher than the hydrate generation phase equilibrium temperature corresponding to the fluid pressure, no hydrate is generated; when the temperature of the fluid in the pipeline is lower than or equal to the hydrate generation phase equilibrium temperature corresponding to the fluid pressure, the pipeline is divided into M sections, the research time is divided into N intervals, j represents the jth pipeline section, and i represents the ith time interval;

[0011] Step 4: assigning i = 1;

[0012] Step 5: Assign j = 1;

[0013] Step 6: Assign initial value T' to the temperature at the outlet of the jth pipe segment;

[0014] Step 7: Assuming the distribution of hydrate particles in the pipe is Poisson distribution, calculate the volume of carbon dioxide hydrate particles according to the sum of the volume of water droplets and the volume of hydrate film covering the water droplets, the lateral growth rate of hydrate film adopts the Chen-Guo comprehensive growth model, and the thickness of hydrate film is calculated by the condensation approximation method, and the volume of hydrate generated in the jth pipe segment V p ′ is calculated;

[0015] Step 8: Calculate the pressure p" at the outlet of the jth pipe segment according to the pressure difference equation , where ΔP is the pressure drop in the pipe, ρ is the density of carbon dioxide, kg / m 3 ; r is the pipe radius, m, β is the pipe angle, °, v p is the velocity of hydrate particle flow, m / s, τ f is the shear stress of the pipe, N / m 2 , and L is the length of the pipe segment, m;

[0016] Step 9: Calculate the temperature T" at the outlet of the jth pipe segment according to the temperature difference equation , where Δq is the heat transfer rate per unit length of the carbon dioxide pipe, W / m, M is the mass flow rate of CO2 pipe, kg / s, v c is the flow rate of carbon dioxide in the pipe, m / s, and h is the enthalpy, kJ / kg;

[0017] Step 10: If |T'-T" |≤ε1 is true, assign T' as T", if not, re-assign T';

[0018] Step 11: Recalculate the volume of hydrate generated in the jth pipe segment V p ";

[0019] Step 12: If |V P '-V P " |≤ε2 is true, assign V p ' as V p "; if not, return to Step 6 to re-assign T', if true, proceed to Step 13;

[0020] Step 13: If j≥M is false, j = j + 1, repeat Steps 6-12 until j = M; if i≥N is false, i = i + 1, return to Step 5 until i = N.

[0021] A further improvement of the present invention is that, in step 1, the phase equilibrium parameters for hydrate formation in impurity-containing carbon dioxide are determined according to the Chen-Guo hydrate formation model, comprising:

[0022] (1) Determine the critical parameters of each component in the fluid and give the initial values ​​of p and T;

[0023] (2) Press Calculate the fugacity f of each component i ,in T c is the critical temperature, K; p c is the critical pressure, Pa;

[0024] (3) Press Calculate the Langmuir constant C of each component j , MPa, where X j ,Y j and Z j is a constant, fitted by the Lenard-Jones potential energy model;

[0025] (4) Press Determine the proportion θ of the connected cavities occupied by each j component gas j , and calculate

[0026] (5) Press formula f i,0 =f iT,0 (T)·f(P)·f(a w ) Calculate the minimum fugacity f required for pure gas component i to stabilize the hydrate structure i,0 ;in Among them, for carbon dioxide hydrate, β, λ1 and λ2 are 0.4242K / bar, 1 / 23 and 3 / 23 respectively; is the activity of water, a i ,b i and c i is the Antoine constant;

[0027] (6) Press Calculate the mole fraction of component i in the polynary gas hydrate and calculate ∑x i ;

[0028] (7) If |∑x i If -1|<ε holds, the phase equilibrium parameters p and T are output. If not, p and T are modified and (2) to (7) are recalculated.

[0029] A further improvement of the present invention is that, in step 2, preliminarily determining the temperature-pressure distribution of the pipeline at the initial moment based on pipeline specification parameters, flow parameters, and fluid composition includes:

[0030] Considering the heat exchange between the buried transportation pipeline and the soil, the temperature T of the carbon dioxide at a certain point on the pipeline x is calculated by the following formula:

[0031] T x = T0 + (T1 - T0)e -αx

[0032] T0 is the average soil temperature, K; T1 is the temperature of the carbon dioxide at the inlet of the infinitesimal pipe section, K; x is the length of the infinitesimal pipe section, m; wherein K is the total heat transfer coefficient of the carbon dioxide and the soil, W / (m 2 ·K), D is the outer diameter of the pipeline, m; M is the mass flow rate of the carbon dioxide pipeline, kg / s; C is the constant-pressure specific heat capacity of the carbon dioxide, J / (kg·K);

[0033] The pressure drop ΔP of the fluid in the pipeline is calculated by the following formula

[0034]

[0035] In the formula, λ is the friction loss coefficient along the pipeline; L is the length of the pipeline, m; d is the inner diameter of the pipeline, m; v c is the flow rate of the carbon dioxide, m / s; g is the acceleration of gravity, m / s 2 ; H is the elevation difference of the pipeline, m.

[0036] The further improvement of the present application is that, in step 7, the distribution of the hydrate particles in the pipeline is assumed to be Poisson distribution, the volume of the carbon dioxide hydrate particles is calculated according to the sum of the volume of the water droplets and the volume of the hydrate film covering the water droplets, the lateral growth rate of the hydrate film adopts the Chen-Guo comprehensive growth model, and the thickness of the hydrate film is calculated by the condensation approximation method, and the volume V p ′ of the hydrate generated in the jth pipeline section is calculated and includes:

[0037] The volume V p ′ of the hydrate generated in the jth pipeline section is calculated by the following formula:

[0038]

[0039] wherein v is the lateral growth rate of the hydrate, which is calculated according to the Chen-Guo comprehensive growth model, ρ h is the molar density, g·mol / mm 3 ; Δh h is the latent heat of the hydrate, J / (g·mol); k1 is the heat transfer coefficient, J / (s·mm 2 ·K); k2 is the reaction rate constant, (m / (s·K n )); Ts T is the hydrate film temperature, K; h is the hydrate film thickness, which is compared with the condensation process; R sys T is the system temperature, K; h is the hydrate film thickness, which is compared with the condensation process; R d R is the radius of the water droplet, m; N is the number of water droplets per unit length of the pipeline, M is the mass flow rate of the pipeline, kg / s; y w W is the mass fraction of water; t MN T is the time for the fluid in the pipeline to flow from point M to point N.

[0040] The further improvement of the present application is that the calculation formula of the thickness h of the hydrate film is as follows:

[0041]

[0042] Wherein, μ w and ρ f are the densities of water and fluid, kg / m 3 ; μ w is the viscosity of water, Pa·s; λ w is the thermal conductivity of water, W / (m·K); k is the condensation heat transfer coefficient.

[0043] The hydrate formation prediction system for the impurity-containing supercritical carbon dioxide conveying pipeline comprises:

[0044] The first parameter determination module determines the phase equilibrium parameters of hydrate formation in the impurity-containing carbon dioxide according to the Chen-Guo hydrate formation model;

[0045] The second parameter determination module preliminarily determines the temperature-pressure distribution of the pipeline at the initial time according to the pipeline specification parameters, the flow parameters and the fluid components;

[0046] The position determination module determines the position of hydrate formation in the pipeline by combining the hydrate formation phase equilibrium parameters and the temperature-pressure distribution of the pipeline; when the temperature of the fluid in the pipeline is higher than the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, no hydrate is formed; when the temperature of the fluid in the pipeline is lower than or equal to the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, the pipeline is divided into M sections, the research time is divided into N intervals, the jth pipeline section is represented by j, and the ith time section is represented by i;

[0047] The first assignment module assigns i=1;

[0048] The second assignment module assigns j=1;

[0049] The third assignment module assigns the initial value T' to the temperature at the outlet of the jth pipeline section;

[0050] The first calculation module calculates the volume of carbon dioxide hydrate particles according to the sum of the volume of water droplets and the volume of hydrate film covering the water droplets, assuming that the distribution of hydrate particles in the pipeline is Poisson distribution, the lateral growth rate of the hydrate film adopts the Chen-Guo comprehensive growth model, and the thickness of the hydrate film is calculated by the condensation approximation method, and the volume V of hydrate generated in the j pipeline section is calculated p ′

[0051] The second calculation module calculates the pressure p" of the j pipeline section outlet according to the pressure difference equation , wherein ΔP is the pressure drop in the pipeline, ρ is the density of carbon dioxide, kg / m 3 ; r is the pipeline radius, m, β is the pipeline angle, °, v p is the velocity of hydrate particle flow, m / s, τ f is the shear stress of the pipeline, N / m 2 , L is the length of the pipeline section, m;

[0052] The third calculation module calculates the temperature T" of the j pipeline section outlet according to the temperature difference equation , wherein Δq is the heat exchange rate per unit length of the carbon dioxide pipeline, W / m, M is the mass flow rate of the CO2 pipeline, kg / s, v c is the flow rate of carbon dioxide in the pipeline, m / s, and h is the enthalpy, kJ / kg;

[0053] The first judgment module assigns T' as T" if |T'-T" |≤ε1 is true, and re-assumes T' if it is not true;

[0054] The fourth calculation module recalculates the volume V of hydrate generated in the j pipeline section p ″

[0055] The second judgment module assigns V P ' as V P " if |V p '-V p " |≤ε2 is true, and returns the third assignment module to re-assume T' if it is not true, and proceeds to the third judgment module if it is true;

[0056] The third judgment module sets j=j+1 and repeats steps 6-12 until j=M if j≥M is false, and sets i=i+1 and returns to step 5 until i=N if i≥N is false.

[0057] A computer readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the hydrate generation prediction method for a supercritical carbon dioxide pipeline containing impurities.

[0058] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0059] The present application provides a hydrate formation prediction method and system for a supercritical carbon dioxide pipeline containing impurities, which determines the phase equilibrium parameters of hydrate formation in carbon dioxide containing impurities by using the Chen-Guo hydrate formation model, and considers the thermodynamic factors of hydrate formation; the hydrate formation position in the pipeline is determined by combining the hydrate formation phase equilibrium parameters with the pipeline temperature-pressure distribution; the present application calculates the lateral growth rate of the hydrate film by using the Chen-Guo comprehensive growth model, simulates the thickness growth of the hydrate film, calculates the thickness of the hydrate film, and calculates the volume of the hydrate film according to the lateral growth rate of the hydrate film and the thickness of the hydrate film, considers the kinetic factors of hydrate growth, and calculates the volume of the carbon dioxide hydrate particles according to the sum of the volume of the water droplets and the volume of the hydrate film covering the water droplets; the present application also considers the distribution of the hydrate particles in the pipeline, so that the generation amount of the hydrate particles in the pipeline can be quickly and accurately predicted. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 The present application provides a hydrate formation prediction method and system for a supercritical carbon dioxide pipeline containing impurities, which determines the phase equilibrium parameters of hydrate formation in carbon dioxide containing impurities by using the Chen-Guo hydrate formation model, and considers the thermodynamic factors of hydrate formation; the hydrate formation position in the pipeline is determined by combining the hydrate formation phase equilibrium parameters with the pipeline temperature-pressure distribution; the present application calculates the lateral growth rate of the hydrate film by using the Chen-Guo comprehensive growth model, simulates the thickness growth of the hydrate film, calculates the thickness of the hydrate film, and calculates the volume of the hydrate film according to the lateral growth rate of the hydrate film and the thickness of the hydrate film, considers the kinetic factors of hydrate growth, and calculates the volume of the carbon dioxide hydrate particles according to the sum of the volume of the water droplets and the volume of the hydrate film covering the water droplets; the present application also considers the distribution of the hydrate particles in the pipeline, so that the generation amount of the hydrate particles in the pipeline can be quickly and accurately predicted.

[0061] Figure 2 The present application provides a hydrate formation prediction method and system for a supercritical carbon dioxide pipeline containing impurities, which determines the phase equilibrium parameters of hydrate formation in carbon dioxide containing impurities by using the Chen-Guo hydrate formation model, and considers the thermodynamic factors of hydrate formation; the hydrate formation position in the pipeline is determined by combining the hydrate formation phase equilibrium parameters with the pipeline temperature-pressure distribution; the present application calculates the lateral growth rate of the hydrate film by using the Chen-Guo comprehensive growth model, simulates the thickness growth of the hydrate film, calculates the thickness of the hydrate film, and calculates the volume of the hydrate film according to the lateral growth rate of the hydrate film and the thickness of the hydrate film, considers the kinetic factors of hydrate growth, and calculates the volume of the carbon dioxide hydrate particles according to the sum of the volume of the water droplets and the volume of the hydrate film covering the water droplets; the present application also considers the distribution of the hydrate particles in the pipeline, so that the generation amount of the hydrate particles in the pipeline can be quickly and accurately predicted.

[0062] Figure 3 The present application provides a hydrate formation prediction method and system for a supercritical carbon dioxide pipeline containing impurities, which determines the phase equilibrium parameters of hydrate formation in carbon dioxide containing impurities by using the Chen-Guo hydrate formation model, and considers the thermodynamic factors of hydrate formation; the hydrate formation position in the pipeline is determined by combining the hydrate formation phase equilibrium parameters with the pipeline temperature-pressure distribution; the present application calculates the lateral growth rate of the hydrate film by using the Chen-Guo comprehensive growth model, simulates the thickness growth of the hydrate film, calculates the thickness of the hydrate film, and calculates the volume of the hydrate film according to the lateral growth rate of the hydrate film and the thickness of the hydrate film, considers the kinetic factors of hydrate growth, and calculates the volume of the carbon dioxide hydrate particles according to the sum of the volume of the water droplets and the volume of the hydrate film covering the water droplets; the present application also considers the distribution of the hydrate particles in the pipeline, so that the generation amount of the hydrate particles in the pipeline can be quickly and accurately predicted.

[0063] Figure 4 The present application provides a hydrate formation prediction method and system for a supercritical carbon dioxide pipeline containing impurities, which determines the phase equilibrium parameters of hydrate formation in carbon dioxide containing impurities by using the Chen-Guo hydrate formation model, and considers the thermodynamic factors of hydrate formation; the hydrate formation position in the pipeline is determined by combining the hydrate formation phase equilibrium parameters with the pipeline temperature-pressure distribution; the present application calculates the lateral growth rate of the hydrate film by using the Chen-Guo comprehensive growth model, simulates the thickness growth of the hydrate film, calculates the thickness of the hydrate film, and calculates the volume of the hydrate film according to the lateral growth rate of the hydrate film and the thickness of the hydrate film, considers the kinetic factors of hydrate growth, and calculates the volume of the carbon dioxide hydrate particles according to the sum of the volume of the water droplets and the volume of the hydrate film covering the water droplets; the present application also considers the distribution of the hydrate particles in the pipeline, so that the generation amount of the hydrate particles in the pipeline can be quickly and accurately predicted. DETAILED DESCRIPTION

[0064] In the following, only certain example embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and description are considered to be exemplary in nature and not limiting.

[0065] It should be understood that when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0066] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0067] It is further to be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items, and that the term "at least one of' encompasses any and all possible combinations of one or more of the associated listed items.

[0068] Various structural diagrams according to the disclosed embodiments of the present application are shown in the accompanying drawings. These diagrams are not drawn to scale, in which certain details are shown in a somewhat exaggerated manner for purposes of clarity and understanding, and certain other details are omitted. The shapes and relative sizes of the various regions, layers, and the relative positions of the regions / layers shown in the drawings are merely exemplary, and in actuality, they can deviate due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, and relative positions can be additionally designed by those skilled in the art according to actual needs.

[0069] Embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0070] Embodiment 1

[0071] As shown in the accompanying drawings, the present application provides a hydrate formation prediction method for a pipeline containing impurities and supercritical carbon dioxide, which comprises: Figure 1

[0072] Step 1: determining the phase equilibrium parameters of hydrate formation in carbon dioxide containing impurities according to the Chen-Guo hydrate formation model;

[0073] Step 2: preliminarily determining the temperature-pressure distribution of the pipeline at the initial time according to the pipeline specification parameters, flow parameters and fluid components;

[0074] Step 3: determining the position of hydrate formation in the pipeline by combining the hydrate formation phase equilibrium parameters and the temperature-pressure distribution of the pipeline; when the temperature of the fluid in the pipeline is higher than the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, no hydrate is formed; when the temperature of the fluid in the pipeline is lower than or equal to the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, the pipeline is divided into M sections, and the research time is divided into N intervals, with j representing the jth pipeline section and i representing the ith time interval;

[0075] Step 4: assigning i = 1;

[0076] Step 5: assigning j = 1;

[0077] Step 6: assigning an initial value T' to the temperature at the outlet of the jth section.​

[0078] Step 7: Assuming the distribution of hydrate particles in the pipeline is Poisson distribution, the volume of carbon dioxide hydrate particles is calculated according to the sum of the volume of water droplets and the volume of hydrate film covering the water droplets, the lateral growth rate of the hydrate film adopts the Chen-Guo comprehensive growth model, and the thickness of the hydrate film is calculated by the condensation approximation method, and the volume V of hydrate generated in the jth pipeline segment is calculated p ′;

[0079] Step 8: According to the pressure difference equation , the pressure p" at the outlet of the jth pipeline segment is calculated, wherein ΔP is the pressure drop in the pipeline, ρ is the density of carbon dioxide, kg / m 3 ; r is the radius of the pipeline, m, β is the pipeline angle, °, v p is the velocity of the hydrate particle flow, m / s, τ f is the shear stress of the pipeline, N / m 2 , L is the length of the pipeline segment, m;

[0080] Step 9: According to the temperature difference equation , the temperature T" at the outlet of the jth pipeline segment is calculated; wherein Δq is the heat exchange rate per unit length of the carbon dioxide pipeline, W / m, M is the mass flow rate of the CO2 pipeline, kg / s, v c is the flow rate of carbon dioxide in the pipeline, m / s, h is the enthalpy, kJ / kg;

[0081] Step 10: If |T'-T" |≤ε1 is established, T' is assigned as T", if not, T' is re-assumed;

[0082] Step 11: The volume V of hydrate generated in the jth pipeline segment is recalculated p ″;

[0083] Step 12: If |V P '-V P " |≤ε2 is established, V p ' is assigned as V p "; if not, return to step 6 to re-assume T', if established, proceed to step 13;

[0084] Step 13: If j≥M is not, j=j+1, repeat steps 6-12 until j=M; if i≥N is not, i=i+1, return to step 5 until i=N.

[0085] Example 2

[0086] The hydrate generation prediction method for the impurity-containing supercritical carbon dioxide conveying pipeline provided by the application comprises:

[0087] Step 1: Determine the phase equilibrium parameters for hydrate formation in impure CO2 based on the Chen-Guo hydrate formation model. The determined phase equilibrium parameters for impure CO2 hydrate are used to subsequently determine whether hydrate formation occurs at a specific temperature and pressure. The specific steps are as follows:

[0088] (1) Determine the critical parameters of each component in the fluid and give the initial values ​​of p and T.

[0089] (2) Press Calculate the fugacity f of each component i ,in T c is the critical temperature, K; p c is the critical pressure, Pa.

[0090] (3) Press Calculate the Langmuir constant C of each component j , MPa, where X j ,Y j and Z j is a constant, fitted by the Lenard-Jones potential energy model.

[0091] (4) Press Determine the proportion θ of the connected cavities occupied by each j component gas j . and calculate

[0092] (5) Press formula f i,0 =f iT,0 (T)·f(P)·f(a w ) Calculate the minimum fugacity f required for pure gas component i to stabilize the hydrate structure i,0 .in Among them, for carbon dioxide hydrate, β, λ1 and λ2 are 0.4242 K / bar, 1 / 23 and 3 / 23 respectively. is the activity of water, a i ,b i and c i is the Antoine constant.

[0093] (6) Press Calculate the mole fraction of component i in the polynary gas hydrate. And calculate Σx i .

[0094] (7) If |Σx i If -1|<ε holds, the phase equilibrium parameters p and T are output. If not, p and T are modified and (2) to (7) are recalculated.

[0095] Step 2: According to the pipe specification parameters, flow parameters and fluid components, the temperature-pressure (T-P) distribution of the pipeline at the initial moment is preliminarily determined. Considering the heat exchange between the buried transportation pipeline and the soil, the temperature T of the carbon dioxide at a certain point on the pipeline is x (K) is calculated according to the following formula:

[0096] T x = T0 + (T1 - T0) e -αx T0 is the average soil temperature, K; T1 is the temperature of the carbon dioxide at the inlet of the micro-element pipe section, K; x is the length of the micro-element pipe section, m; wherein K is the total heat transfer coefficient of the carbon dioxide and the soil, W / (m 2 ·K), D is the outer diameter of the pipeline, m; M is the mass flow rate of the carbon dioxide pipe, kg / s; C is the constant-pressure specific heat capacity of the carbon dioxide, J / (kg·K).

[0097] The pressure drop ΔP of the fluid in the pipeline is calculated according to the following formula

[0098]

[0099] In the formula, ρ is the density of the carbon dioxide, kg / m 3 ; λ is the friction loss coefficient; L is the length of the pipeline, m; d is the inner diameter of the pipeline, m; v c is the flow rate of the carbon dioxide, m / s; g is the acceleration of gravity, m / s 2 ; H is the elevation difference of the pipeline, m.

[0100] Step 3: The position of the hydrate generation in the pipeline is determined in combination with the hydrate generation phase equilibrium parameters and the temperature-pressure distribution of the pipeline. When the temperature of the fluid in the pipeline is higher than the phase equilibrium temperature of the hydrate at the pressure, no hydrate is generated, and when the temperature of the fluid in the pipeline is lower than or equal to the phase equilibrium temperature of the hydrate at the pressure, the pipeline is divided into M sections (represented by j) and the research time is divided into N intervals (represented by i), and j=1 and i=1 are assigned.

[0101] Step 4: The temperature of the outlet of the jth pipe section is assigned an initial value T'.

[0102] Step 5: The volume of the carbon dioxide hydrate particles is calculated according to the sum of the volume of the water droplets and the volume of the hydrate film covering the water droplets, the lateral growth rate of the hydrate film adopts the Chen-Guo comprehensive growth model, the thickness of the hydrate film is calculated by the condensation approximation method, and it is assumed that the distribution of the hydrate particles in the pipeline is Poisson distribution. The volume V p ′ of the hydrate generated in the jth pipe section at the ith time is calculated according to the following formula:

[0103]

[0104] Where v is the lateral growth rate of hydrate, calculated according to the Chen-Guo comprehensive growth model, ρ h is the molar density, g·mol / mm 3 ; Δh h is the latent heat of hydrate, J / (g·mol); k1 is the heat transfer coefficient, J / (s·mm 2 ·K); k2 is the reaction rate constant, (m / (s·K n ));T s is the hydrate film temperature, K; T sys is the system temperature, K. h is the thickness of the hydrate film, which is compared with the condensation process. Calculate, ρ w and ρ f are the densities of water and fluid, kg / m 3 ;μ w is the viscosity of water, Pa·s; λ w is the thermal conductivity of water, W / (m·K). R d is the radius of the water droplet, m; is the number of water droplets per unit length of the pipeline, M is the pipeline mass flow rate, kg / s; y w is the mass fraction of water. MN It is the time it takes for the fluid in the pipe to flow from point M to point N.

[0105] Step 6: According to the pressure difference equation Calculate the pressure p″ at the outlet of pipe section j.

[0106] Step 7: According to the temperature difference equation Calculate the temperature T″ at the outlet of pipe section j. Where Δq is the heat transfer rate per unit length of the carbon dioxide pipe, W / m. c is the flow rate of carbon dioxide in the pipeline, m / s. p is the pipeline angle, °.

[0107] Step 8: If |T'-T"|≤ε1 holds, assign T' to T", if not, re-assume T'.

[0108] Step 9: Recalculate the hydrate volume V generated in the jth pipeline section during the i-th period p ″.

[0109] Step 10: If |V P '-V P ”|≤ε2 holds true, then V p ′ is assigned the value of V p If not, re-assume T′.

[0110] Step 11: sequentially calculate hydrate volume V of each pipe section at i time p ′.

[0111] Step 12: sequentially calculate hydrate volume V of each pipe section at each time p ′.

[0112] Example 3

[0113] The hydrate generation amount in a supercritical CO2 conveying pipeline containing impurities is predicted by using the present application. The components of the fluid in the pipeline include CO2, CO, H2, N2 and H2O, and the mole fractions are 99.08%, 0.5%, 0.2%, 0.2% and 0.02% respectively. The pipeline design parameters are shown in Table 1. The mass flow rate of CO2 in the pipeline is 310,000 tons / year, the fluid pressure at the pipeline inlet is 15 MPa, and the temperature is 14.58℃. Through the calculation of p-T along the pipeline, the fluid pressure at the pipeline outlet is 13.98 MPa, and the temperature is 7.02℃. The hydrate generation amount along the pipeline at different times is obtained by using the hydrate generation amount prediction method provided by the present application, as shown in Table 2. Figure 3

[0114] Table 1. Pipeline design parameters

[0115]

[0116] Example 4

[0117] As shown in Table 2, the present application provides a hydrate generation prediction system for a supercritical carbon dioxide conveying pipeline containing impurities, which comprises: Figure 4 A first parameter determination module determines the phase equilibrium parameters of hydrate generation in the carbon dioxide containing impurities according to the Chen-Guo hydrate generation model;

[0118] A second parameter determination module preliminarily determines the temperature-pressure distribution of the pipeline at the initial time according to the pipeline specification parameters, flow parameters and fluid components;

[0119] A position determination module determines the position of hydrate generation in the pipeline by combining the hydrate generation phase equilibrium parameters and the temperature-pressure distribution of the pipeline. When the temperature of the fluid in the pipeline is higher than the hydrate generation phase equilibrium temperature corresponding to the fluid pressure, no hydrate is generated. When the temperature of the fluid in the pipeline is lower than or equal to the hydrate generation phase equilibrium temperature corresponding to the fluid pressure, the pipeline is divided into M sections, and the research time is divided into N intervals. The j-th pipe section is represented by j, and the i-th time section is represented by i;

[0120] A first assignment module assigns i = 1;

[0121] A second assignment module assigns j = 1;

[0122] ​​

[0123] a third assignment module, assigning an initial value T' to the temperature at the outlet of the jth pipe section;

[0124] a first calculation module, calculating the volume of the carbon dioxide hydrate particles generated in the jth pipe section V according to the volume of the water droplets and the volume of the hydrate film covering the water droplets, assuming that the distribution of the hydrate particles in the pipe is Poisson distribution, the lateral growth rate of the hydrate film is calculated by using the Chen-Guo comprehensive growth model, and the thickness of the hydrate film is calculated by using the condensation approximation method; p ′;

[0125] a second calculation module, calculating the pressure p" at the outlet of the jth pipe section according to the pressure difference equation , wherein ΔP is the pressure drop in the pipe, ρ is the density of carbon dioxide, kg / m3, r is the radius of the pipe, m, β is the pipe angle, °, v is the velocity of the hydrate particle flow, m / s, τ is the shear stress of the pipe, N / m, and L is the length of the pipe section, m; 3 ; p f 2 ;

[0126] a third calculation module, calculating the temperature T" at the outlet of the jth pipe section according to the temperature difference equation , wherein Δq is the heat exchange rate per unit length of the carbon dioxide pipe, W / m, M is the mass flow rate of the CO2 pipe, kg / s, v is the flow rate of carbon dioxide in the pipe, m / s, and h is the enthalpy, kJ / kg; c ;

[0127] a first judgment module, if |T'-T"|≤ε1 is established, then assigning T' as T", and if not, then re-assuming T';

[0128] a fourth calculation module, re-calculating the volume of the hydrate particles V generated in the jth pipe section p ′;

[0129] a second judgment module, if |V P '-V P "|≤ε2 is established, then assigning V p ′ as V p ", and if not, then returning to the third assignment module to re-assume T', and if established, then performing a third judgment module;

[0130] the third judgment module, if j≥M is not, then j=j+1, repeating steps 6-12 until j=M, and if i≥N is not, then i=i+1, returning to step 5 until i=N.

[0131] ​​The application provides a computer readable storage medium, the computer readable storage medium stores a computer program, and the computer program realizes steps of the impurity-containing supercritical carbon dioxide pipeline hydrate generation prediction method when being executed by a processor.

[0132] Those skilled in the art will appreciate that embodiments of the application can be supplied as methods, systems, or computer program products. Accordingly, the application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the application can be embodied in the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk memory, CD-ROM, optical memory, etc.) having computer usable program code embodied therein.

[0133] The application is described with reference to flowcharts and / or block diagrams of methods, systems and computer program products according to embodiments of the application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as combinations of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, a special purpose computer, an embedded processing machine, or other programmable data processing equipment to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing equipment produce an apparatus for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 a system to perform the functions specified in one or more flows and / or blocks.

[0134] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing equipment to work in a specific way, so that the instructions stored in the computer readable memory produce a product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 a system to perform the functions specified in one or more flows and / or blocks.

[0135] These computer program instructions can also be loaded into a computer or other programmable data processing equipment, so that a series of operation steps are performed on the computer or other programmable equipment to produce a computer implemented process, so that the instructions executed on the computer or other programmable equipment provide steps for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 a system to perform the functions specified in one or more flows and / or blocks.

[0136] The application protects the following invention points:

[0137] 1. The present application combines the thermodynamic and kinetic factors of hydrate formation, combines the temperature-pressure distribution of the pipeline and the distribution of water droplets in the pipeline, and establishes a prediction method for the amount of hydrate formation in the pipeline. The formation position and amount of hydrate in the pipeline are predicted, and the calculation is simple and accurate.

[0138] 2. The present application simulates the growth of hydrate film thickness with condensation, and calculates the thickness of hydrate film.

[0139] 3. The present application calculates the volume of carbon dioxide hydrate particles according to the sum of the volume of water droplets and the volume of hydrate film covering the water droplets.

[0140] 4. The present application considers the distribution of water droplets in the pipeline.

[0141] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting in any respect, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended to encompass all changes falling within the meaning and scope of the equivalent elements of the claims. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0142] In addition, it should be understood that although the present specification is described in terms of embodiments, each embodiment does not contain only one independent technical solution, and the description manner of the specification is only for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that can be understood by those skilled in the art. The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the claims of the present application.

Claims

1. A method for predicting hydrate formation in a supercritical carbon dioxide pipeline containing impurities, characterized in that: include: Step 1: Determine the phase equilibrium parameters for hydrate formation in impurity-containing carbon dioxide according to the Chen-Guo hydrate formation model; Step 2: Preliminarily determine the temperature-pressure distribution of the pipeline at the initial moment based on pipeline specifications, flow parameters, and fluid composition; Step 3: Determine the location of hydrate formation in the pipeline by combining the hydrate formation phase equilibrium parameters with the pipeline temperature-pressure distribution. When the temperature of the fluid in the pipeline is higher than the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, no hydrate is formed. When the temperature of the fluid in the pipeline is lower than or equal to the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, the pipeline is divided into M sections and the study time is divided into N intervals, with j representing the jth pipe section and i representing the ith time period. Step 4: Assign i=1; Step 5: Assign j = 1; Step 6: Assign an initial value T' to the temperature at the outlet of pipe section j; Step 7: Assuming that the distribution of hydrate particles in the pipeline is Poisson distribution, the volume of the CO2 hydrate particles is calculated based on the sum of the volume of the water droplet and the volume of the hydrate film covering the water droplet. The lateral growth rate of the hydrate film is calculated using the Chen-Guo comprehensive growth model, and the thickness of the hydrate film is calculated using the condensation analogy method. The hydrate volume V generated in the jth pipeline section is calculated. p '; Step 8: According to the pressure difference equation Calculate the pressure p″ at the outlet of pipe section j, where ΔP is the pressure drop in the pipe and ρ is the density of carbon dioxide, kg / m 3 ; r is the pipeline radius, m, β is the pipeline angle, °, v p is the velocity of hydrate particle flow, m / s, τ f is the pipe shear stress, N / m 2 , L pipe section length, m; Step 9: According to the temperature difference equation Calculate the temperature T″ at the outlet of pipe section j; where Δq is the heat transfer rate per unit length of the carbon dioxide pipeline, W / m, M is the CO2 pipeline mass flow rate, kg / s, v c is the flow rate of carbon dioxide in the pipeline, m / s, h is the enthalpy, kJ / kg; Step 10: If |T'-T"|≤ε1 holds, assign T' to T", if not, re-assume T'; Step 11: Recalculate the hydrate volume V generated in the jth pipeline segment p ″; Step 12: If |V P '-V P ”|≤ε2 holds true, then V p ′ is assigned to V p If not, return to step 6 and re-assume T′. If it is true, proceed to step 13. Step 13: If j ≥ M, then j = j + 1, and repeat steps 6 to 12 until j = M; If i≥N is not, then i=i+1 and return to step 5 until i=N.

2. The method for predicting hydrate formation in a supercritical carbon dioxide transmission pipeline containing impurities according to claim 1, wherein: In step 1, the phase equilibrium parameters for hydrate formation in impurity-containing carbon dioxide are determined according to the Chen-Guo hydrate formation model, including: (1) Determine the critical parameters of each component in the fluid and give the initial values ​​of p and T; (2) Press Calculate the fugacity f of each component i ,in T c is the critical temperature, K; p c is the critical pressure, Pa; (3) Press Calculate the Langmuir constant C of each component j , MPa, where X j ,Y j and Z j is a constant, fitted by the Lenard-Jones potential energy model; (4) Press Determine the proportion θ of the connected cavities occupied by each j component gas j , and calculate (5) Press formula f i,0 =f iT,0 (T)·f(P)·f(a w ) Calculate the minimum fugacity f required for pure gas component i to stabilize the hydrate structure i,0 ;in Among them, for carbon dioxide hydrate, β, λ1 and λ2 are 0.4242K / bar, 1 / 23 and 3 / 23 respectively; is the activity of water, a i ,b i and c i is the Antoine constant; (6) Press Calculate the mole fraction of component i in the polynary gas hydrate and calculate ∑x i ; (7) If |∑x i If -1|<ε holds, the phase equilibrium parameters p and T are output. If not, p and T are modified and (2) to (7) are recalculated.

3. The method for predicting hydrate formation in a supercritical carbon dioxide transmission pipeline containing impurities according to claim 2, wherein: In step 2, based on pipeline specifications, flow parameters, and fluid composition, the initial temperature-pressure distribution of the pipeline is preliminarily determined, including: Considering the heat exchange between the buried pipeline and the soil, the temperature of carbon dioxide at a certain point on the pipeline is T x Calculate as follows: T x =T0+(T1-T0)e -αx T0 is the average soil temperature, K; T1 is the temperature of carbon dioxide at the inlet of the micro-element pipe segment, K; x is the length of the micro-element pipe segment, m; Where K is the total heat transfer coefficient between carbon dioxide and soil, W / (m 2 ·K), D is the outer diameter of the pipeline, m; M is the mass flow rate of carbon dioxide in the pipeline, kg / s; C is the specific heat capacity of carbon dioxide at constant pressure, J / (kg·K); The pressure drop ΔP of the fluid in the pipeline is calculated as follows: Where λ is the resistance loss coefficient along the pipeline; L is the pipeline length, m; d is the inner diameter of the pipeline, m; v c is the carbon dioxide flow rate, m / s; g is the acceleration due to gravity, m / s 2 ; H is the pipeline elevation difference, m.

4. The method for predicting hydrate formation in a supercritical carbon dioxide transmission pipeline containing impurities according to claim 3, wherein: In step 7, the distribution of hydrate particles in the pipeline is assumed to be Poisson distribution. The volume of the carbon dioxide hydrate particles is calculated based on the sum of the volume of the water droplet and the volume of the hydrate film covering the water droplet. The lateral growth rate of the hydrate film is calculated using the Chen-Guo comprehensive growth model, and the thickness of the hydrate film is calculated using the condensation analogy method. The hydrate volume V generated in the jth pipeline section is calculated. p ',include: The hydrate volume V generated in the jth pipeline section is calculated as follows: p ′: Where v is the lateral growth rate of hydrate, calculated according to the Chen-Guo comprehensive growth model, ρ h is the molar density, g·mol / mm 3 ; Δh h is the latent heat of hydrate, J / (g·mol); k1 is the heat transfer coefficient, J / (s·mm 2 ·K); k2 is the reaction rate constant, (m / (s·K n ));T s is the hydrate film temperature, K; T sys is the system temperature, K; h is the thickness of the hydrate film, which is compared with the condensation process; R d is the radius of the water droplet, m; is the number of water droplets per unit length of the pipeline, M is the pipeline mass flow rate, kg / s; y w is the mass fraction of water; t MN It is the time it takes for the fluid in the pipe to flow from point M to point N.

5. The method for predicting hydrate formation in a supercritical carbon dioxide transmission pipeline containing impurities according to claim 4, characterized in that: The calculation formula of the hydrate film thickness h is as follows: Among them, ρ w and ρ f are the densities of water and fluid, kg / m 3 ;μ w is the viscosity of water, Pa·s; λ w is the thermal conductivity of water, W / (m·K); k is the condensation heat transfer coefficient.

6. Hydrate formation prediction system for supercritical carbon dioxide transportation pipeline containing impurities, characterized by: include: A first parameter determination module determines the phase equilibrium parameters of hydrate formation in impurity-containing carbon dioxide according to the Chen-Guo hydrate formation model; The second parameter determination module preliminarily determines the temperature-pressure distribution of the pipeline at the initial moment based on pipeline specification parameters, flow parameters and fluid composition; The location determination module combines the hydrate formation phase equilibrium parameters with the pipeline temperature-pressure distribution to determine the location of hydrate formation in the pipeline. When the temperature of the fluid in the pipeline is higher than the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, no hydrate is formed. When the temperature of the fluid in the pipeline is lower than or equal to the hydrate formation phase equilibrium temperature corresponding to the fluid pressure, the pipeline is divided into M sections and the study time is divided into N intervals, with j representing the jth pipe section and i representing the ith time period. The first assignment module assigns i=1; The second assignment module assigns j=1; The third assignment module assigns an initial value T′ to the temperature at the outlet of pipe segment j; The first calculation module assumes that the distribution of hydrate particles in the pipeline is Poisson distribution. The volume of carbon dioxide hydrate particles is calculated based on the sum of the volume of the water droplet and the volume of the hydrate film covering the water droplet. The lateral growth rate of the hydrate film is calculated using the Chen-Guo comprehensive growth model. The thickness of the hydrate film is calculated using the condensation analogy method. The hydrate volume V generated in the jth pipeline section is calculated. p '; The second calculation module, based on the pressure difference equation Calculate the pressure p″ at the outlet of pipe section j, where ΔP is the pressure drop in the pipe and ρ is the density of carbon dioxide, kg / m 3 ; r is the pipeline radius, m, β is the pipeline angle, °, v p is the velocity of hydrate particle flow, m / s, τ f is the pipe shear stress, N / m 2 , L pipe section length, m; The third calculation module, based on the temperature difference equation Calculate the temperature T″ at the outlet of pipe section j; where Δq is the heat transfer rate per unit length of the carbon dioxide pipeline, W / m, M is the CO2 pipeline mass flow rate, kg / s, v c is the flow rate of carbon dioxide in the pipeline, m / s, h is the enthalpy, kJ / kg; The first judgment module, if |T'-T"|≤ε1 holds, then assign T' to T", if not, then re-assume T'; The fourth calculation module recalculates the hydrate volume V generated in the jth pipeline segment p ″; The second judgment module, if |V P '-V P ”|≤ε2 holds true, then V p ′ is assigned to V p If not, return to the third assignment module and re-assume T'. If it is true, proceed to the third judgment module. The third judgment module, if j≥M is not, then j=j+1, and repeat steps 6-12 until j=M; If i≥N is not, then i=i+1 and return to step 5 until i=N.

7. The hydrate formation prediction system for supercritical carbon dioxide transportation pipeline containing impurities according to claim 6 is characterized in that: In the first parameter determination module, the phase equilibrium parameters for hydrate formation in impurity-containing carbon dioxide are determined according to the Chen-Guo hydrate formation model, including: (1) Determine the critical parameters of each component in the fluid and give the initial values ​​of p and T; (2) Press Calculate the fugacity f of each component i ,in T c is the critical temperature, K; p c is the critical pressure, Pa; (3) Press Calculate the Langmuir constant C of each component j , MPa, where X j ,Y j and Z j is a constant, fitted by the Lenard-Jones potential energy model; (4) Press Determine the proportion θ of the connected cavities occupied by each j component gas j , and calculate (5) Press formula f i,0 =f iT,0 (T)·f(P)·f(a w ) Calculate the minimum fugacity f required for pure gas component i to stabilize the hydrate structure i,0 ;in Among them, for carbon dioxide hydrate, β, λ1 and λ2 are 0.4242K / bar, 1 / 23 and 3 / 23 respectively; is the activity of water, a i ,b i and c i is the Antoine constant; (6) Press Calculate the mole fraction of component i in the polynary gas hydrate and calculate Σx i ; (7) If |Σx i If -1|<ε holds, the phase equilibrium parameters p and T are output. If not, p and T are modified and (2) to (7) are recalculated.

8. The hydrate formation prediction system for supercritical carbon dioxide transportation pipeline containing impurities according to claim 7 is characterized in that: In the second parameter determination module, the temperature-pressure distribution of the pipeline at the initial moment is preliminarily determined based on the pipeline specification parameters, flow parameters, and fluid composition, including: Considering the heat exchange between the buried pipeline and the soil, the temperature of carbon dioxide at a certain point on the pipeline is T x Calculate as follows: T x =T0+(T1-T0)e -αx T0 is the average soil temperature, K; T1 is the temperature of carbon dioxide at the inlet of the micro-element pipe segment, K; x is the length of the micro-element pipe segment, m; Where K is the total heat transfer coefficient between carbon dioxide and soil, W / (m 2 ·K), D is the outer diameter of the pipeline, m; M is the mass flow rate of carbon dioxide in the pipeline, kg / s; C is the specific heat capacity of carbon dioxide at constant pressure, J / (kg·K); The pressure drop ΔP of the fluid in the pipeline is calculated as follows: Where λ is the resistance loss coefficient along the pipeline; L is the pipeline length, m; d is the inner diameter of the pipeline, m; v c is the carbon dioxide flow rate, m / s; g is the acceleration due to gravity, m / s 2 ; H is the pipeline elevation difference, m.

9. The hydrate formation prediction system for supercritical carbon dioxide transportation pipeline containing impurities according to claim 8, characterized in that: In the first calculation module, the distribution of hydrate particles in the pipeline is assumed to be Poisson distribution. The volume of carbon dioxide hydrate particles is calculated based on the sum of the volume of the water droplet and the volume of the hydrate film covering the water droplet. The lateral growth rate of the hydrate film is calculated using the Chen-Guo comprehensive growth model, and the thickness of the hydrate film is calculated using the condensation analogy method. The hydrate volume V generated in the jth pipeline section is calculated. p ',include: The hydrate volume V generated in the jth pipeline section is calculated as follows: p ′: Where v is the lateral growth rate of hydrate, calculated according to the Chen-Guo comprehensive growth model, ρ h is the molar density, g·mol / mm 3 ; Δh h is the latent heat of hydrate, J / (g·mol); k1 is the heat transfer coefficient, J / (s·mm 2 ·K); k2 is the reaction rate constant, (m / (s·K n ));T s is the hydrate film temperature, K; T sys is the system temperature, K; h is the thickness of the hydrate film, which is compared with the condensation process; R d is the radius of the water droplet, m; is the number of water droplets per unit length of the pipeline, M is the pipeline mass flow rate, kg / s; y w is the mass fraction of water; t MN It is the time it takes for the fluid in the pipe to flow from point M to point N.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the method for predicting hydrate formation in a supercritical carbon dioxide transmission pipeline containing impurities according to any one of claims 1 to 5.

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