Segmented design method and device for wall thickness of long-distance supercritical CO2 pipeline

Abstract

The invention discloses a segmented design method and device for the wall thickness of a long-distance supercritical CO2 pipeline, and the method comprises the steps: building a pipeline conveying model according to parameters needed by model building, calculating the pressure drop and the temperature drop of the pipeline along the way, and segmenting the pipeline according to a preset length to determine the maximum pressure and the maximum temperature of each segment; calculating the highest pressure step of each section according to the highest pressure and the highest temperature of each section; calculating the wall thickness required by toughness crack arrest of each section of pipeline according to the highest pressure step; the wall thickness is calculated according to the internal pressure of the whole pipeline, and the wall thickness required by toughness crack arrest is selected as the final wall thickness for the pipeline section with the pipeline medium temperature higher than a preset threshold value; and the wall thickness required by internal pressure is selected as the final wall thickness for other pipeline sections. According to the method, the purpose of evaluating the wall thickness of the pipeline in a segmented manner is achieved, and the problem of high toughness crack arrest wall thickness caused by the fact that inlet temperature condition analysis is still adopted after the middle and rear sections of the long-distance pipeline are subjected to on-way temperature drop is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of pipeline design, and in particular relates to a method and a device for designing the wall thickness of a long-distance supercritical CO2 pipeline by segmentation. Background Art

[0002] Long-distance pipeline transportation is a key way to support the capture and utilization of carbon dioxide. The critical temperature of carbon dioxide is about 31.1℃, and the critical pressure is about 7.38MPa. When transporting carbon dioxide over long distances through pipelines, it is generally recognized that a supercritical transport phase mode with a pressure higher than the critical pressure is used to improve the economic efficiency of transportation.

[0003] Similar to conventional oil and gas pipelines, CO2 pipelines also face operational risks, but they have typical characteristics. CO2 medium is non-flammable, and after leakage, it mainly spreads over a large area along the surface, creating the risk of poisoning and suffocation. Supercritical CO2 is in a supercritical state or dense state with a higher density during pipeline transportation. After a leak occurs, the medium leaked out of the pipe will form a gaseous state due to a significant drop in pressure; the medium accumulated in the pipe will undergo a transformation from supercritical state → gas-liquid two-phase state → gas state during the continuous depressurization process, and a relatively obvious pressure step will appear in the gas-liquid two-phase state. The emergence of this pressure step produces a relatively stable continuous cracking pressure, which poses a challenge to the toughness and crack arrest performance of the ruptured CO2 pipeline along the way. Appropriate measures need to be taken to ensure the toughness and crack arrest performance of the steel pipeline along the way.

[0004] According to the characteristics of the medium and the leakage (rupture) characteristics, the industry has carried out experiments and simulations on toughness arrest along the supercritical CO2 pipeline. In actual projects at home and abroad, the main measures taken are to increase the wall thickness of the pipeline (in the case of internal pressure design wall thickness, additional wall thickness is added to meet the toughness arrest requirements) to ensure the toughness of the CO2 pipeline. This has increased the investment in the project to a certain extent.

[0005] However, the industry has only studied the small-scale supercritical CO2 crack arrest toughness in rupture experiments, and has not yet studied the wall thickness design method of long-distance supercritical CO2 pipelines. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art, provide a long-distance supercritical CO2 pipeline wall thickness segmentation design method and device, further improve, efficiently, economically and safely ensure the safe operation of the supercritical CO2 pipeline.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] A long-distance supercritical CO2 pipeline wall thickness segmentation design method, the method comprising:

[0009] Establish a pipeline transportation model based on the parameters required for model establishment, calculate the pressure drop and temperature drop along the pipeline, and divide the pipeline into sections according to the preset length to determine the maximum pressure and maximum temperature of each section;

[0010] Calculate the highest pressure step of each section according to the highest pressure and highest temperature of each section;

[0011] Calculate the wall thickness required for toughness crack arrest of each section of the pipeline according to the highest pressure step;

[0012] The wall thickness is calculated based on the internal pressure of the entire pipeline. For pipeline sections where the pipeline medium temperature is higher than the preset threshold, the wall thickness required for ductile crack arrest is selected as the final wall thickness; for the remaining pipeline sections, the wall thickness required by the internal pressure is selected as the final wall thickness.

[0013] Furthermore, the pipeline transportation model includes a pipeline transportation model under summer transportation conditions.

[0014] Further, the calculation of the highest pressure step of each section according to the highest pressure and the highest temperature of each section specifically includes:

[0015] Establish an adiabatic discharge model based on the maximum pressure and maximum temperature of each section;

[0016] According to the adiabatic discharge model, each section is simulated for rupture adiabatic discharge to obtain pipeline rupture discharge;

[0017] When the medium in the pipeline changes into gas-liquid two-phase, the medium pressure in the pipeline under the corresponding working condition is extracted as the highest pressure step of the separation section.

[0018] Furthermore, the transformation of the medium in the pipeline into gas-liquid two-phase is determined by monitoring the gas-liquid ratio of the medium in the pipeline.

[0019] Furthermore, the calculation of the wall thickness required for toughness crack arrest of each section of the pipeline specifically includes:

[0020] The highest pressure step in each section is used as the driving force for evaluating the crack arrest toughness and the ductile cracking trend is calculated.

[0021] The toughness crack arrest performance is calculated by CVN impact energy;

[0022] The wall thickness required for ductile crack arrest under preset ductile crack arrest conditions is calculated based on the ductile cracking trend and ductile crack arrest performance.

[0023] Furthermore, the CVN impact energy is obtained by correcting the actual CVN impact energy with a preset correction coefficient.

[0024] Furthermore, the actual CVN impact energy is determined according to the steel pipe type, outer diameter and material.

[0025] Furthermore, the calculation of the wall thickness based on the internal pressure of the entire pipeline also includes adding design coefficients of different regional grades.

[0026] Furthermore, the parameters required for establishing the model include the diameter, length, material, composition, boundary pressure, boundary temperature, maximum flow rate, burial depth conditions and environmental parameters of the pipeline.

[0027] On the other hand, the present invention also provides a device for designing the wall thickness of a long-distance supercritical CO2 pipeline by segmentation, the device comprising:

[0028] A maximum pressure and temperature calculation module, wherein the maximum pressure and temperature acquisition module establishes a pipeline transportation model according to the parameters required for model establishment, calculates the pressure drop and temperature drop along the pipeline, and divides the pipeline into sections according to a preset length to determine the maximum pressure and maximum temperature of each section;

[0029] A maximum pressure step calculation module, wherein the maximum pressure step calculation module calculates the maximum pressure step of each section according to the maximum pressure and maximum temperature of each section;

[0030] A module for calculating the wall thickness required for tough crack arrest, wherein the module calculates the wall thickness required for tough crack arrest of each section of the pipeline according to the highest pressure step;

[0031] The final wall thickness calculation module calculates the wall thickness according to the internal pressure of the entire pipeline. For the pipeline section where the pipeline medium temperature is higher than the preset threshold, the wall thickness required for ductile crack arrest is selected as the final wall thickness; for the remaining pipeline sections, the wall thickness required by the internal pressure is selected as the final wall thickness.

[0032] The beneficial effects of the present invention are:

[0033] (1) Based on the basic physical properties of supercritical CO2, the law of phase change, the changes in transportation conditions and the characteristics of toughness arrest of pipelines, the present invention aims to solve the problem that the wall thickness selection of supercritical CO2 long-distance transportation pipelines is affected by toughness arrest. Starting from the perspective of the wall thickness of the segmented pipeline, the present invention proposes ideas such as process operation parameter analysis, rupture pressure step calculation, crack arrest toughness evaluation, and internal pressure wall thickness comparison to form a design method.

[0034] (2) The present invention realizes safe and efficient control over the wall thickness design of long-distance supercritical CO2 pipelines, taking into account both the wall thickness required for internal pressure and the wall thickness required for toughness crack arrest. Through the segmented design method, the factor "medium temperature" which has a greater contribution to the toughness crack arrest ability is selected in segments (the medium temperature directly affects the driving force of toughness cracking), so that the wall thickness selection result is mainly based on the wall thickness required for toughness crack arrest in the front section of the pipeline (where the medium temperature is higher), and the wall thickness selection result is mainly based on the wall thickness required for internal pressure in the rear section of the pipeline (where the medium temperature is lower). Under the condition of fully ensuring the safety of operation, the pipeline investment can be effectively reduced for most supercritical CO2 pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flowchart of a method for segmented design of wall thickness of a long-distance supercritical CO2 pipeline provided by an embodiment of the present invention;

[0036] Figure 2 It is a structural block diagram of a long-distance supercritical CO2 pipeline wall thickness segmentation design device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0038] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0039] According to the characteristics of the medium and the leakage (rupture) characteristics, the industry has carried out experiments and simulations on toughness arrest along the supercritical CO2 pipeline. In actual projects at home and abroad, the main measures taken are to increase the wall thickness of the pipeline (in the case of internal pressure design wall thickness, additional wall thickness is added to meet the toughness arrest requirements) to ensure the toughness of the CO2 pipeline. This has increased the investment in the project to a certain extent.

[0040] However, the industry has only studied the small-scale supercritical CO2 crack arrest toughness in rupture experiments, and has not yet studied the wall thickness design method of long-distance supercritical CO2 pipelines.

[0041] In order to solve the above technical problems, the following embodiments of the method and device for segmented design of wall thickness of long-distance supercritical CO2 pipeline of the present invention are proposed.

[0042] Example 1

[0043] The principle of the long-distance supercritical CO2 pipeline wall thickness segmentation design method provided in this embodiment is as follows:

[0044] Supercritical CO2 is in a supercritical state or dense state with high density during pipeline transportation. After leakage occurs, the medium leaking out of the pipe will form a gaseous state due to a significant reduction in pressure; the medium accumulated in the pipe will undergo a supercritical state-gas-liquid two-phase state-gas state during the continuous depressurization process, and a relatively obvious pressure step will appear in the gas-liquid two-phase state. The emergence of this pressure step produces a relatively stable and continuous cracking pressure, which poses a challenge to the tough crack arrest along the broken CO2 pipeline. Appropriate measures need to be taken to ensure the tough crack arrest performance of the steel pipeline along the way. In response to this problem, the tough crack arrest ability of the pipeline is generally enhanced by increasing the wall thickness of the pipeline. For long-distance transmission pipelines, this method will lead to a significant increase in investment; and as the medium in the pipeline is transported, its medium temperature will gradually approach the buried ambient temperature. Therefore, it is possible to consider starting from the method of extracting the pipeline operating temperature in sections, dividing the pipeline into several partitions, and calculating the tough crack driving force in each partition, and thus proposing the tough crack arrest performance, forming the wall thickness required for tough crack arrest in each partition.

[0045] In the calculation of the wall thickness required for tough crack arrest of the separation section, the balance between the tough cracking tendency and the tough crack arrest performance was considered, and it was believed that tough crack arrest was achieved when the tough crack arrest performance was greater than the tough cracking tendency. Furthermore, the existing calculation method was revised, and through a large amount of data comparison, it was proposed to use the actual impact energy that the steel pipe can meet as the standard (to increase the CVN value as much as possible to ensure the toughness performance of the pipeline), and after assigning the correction coefficient, it was used as the CVN impact energy value involved in the tough crack arrest evaluation, thereby further improving the accuracy and reliability of the wall thickness required for tough crack arrest.

[0046] For pipelines with different separation sections, the pipe section close to the high-temperature carbon source side is generally at a higher temperature (the medium temperature in the pipeline gradually decreases with the transportation distance). Therefore, after comparing the wall thickness required for toughness-based crack arrest and the wall thickness required for internal pressure design, it can be found that the wall thickness required for toughness-based crack arrest will generally be adopted (this wall thickness is generally greater than the wall thickness required for internal pressure design); and as the pipeline transportation distance increases, in the middle and rear sections of the pipeline, the medium temperature gradually decreases. Therefore, after comparing the wall thickness required for toughness-based crack arrest and the wall thickness required for internal pressure design, it can be found that the wall thickness required for internal pressure design will be greater than the wall thickness required for toughness-based crack arrest. Through comparison, the required wall thickness of each separation section can be screened out more scientifically. Furthermore, by designing the wall thickness in sections, on the one hand, it can avoid the problem of selecting a larger wall thickness required for toughness-based crack arrest after using the inlet temperature for toughness evaluation in the middle and rear sections of the pipeline, thereby improving the economy of the pipeline. On the other hand, it can also further promote the development of technology in this field and improve the level of refinement.

[0047] Reference Figure 1 ,like Figure 1The figure is a flowchart of a method for designing the wall thickness of a long-distance supercritical CO2 pipeline provided in this embodiment. The method specifically includes the following steps:

[0048] Step S100: Establish a pipeline transportation model according to the parameters required for model establishment, calculate the pressure drop and temperature drop along the pipeline, and divide the pipeline into sections according to the preset length to determine the maximum pressure and maximum temperature of each section. This embodiment establishes a pipeline transportation hydraulic and thermal model based on the pipeline diameter, length, material, component, boundary pressure, boundary temperature, maximum flow rate, burial depth conditions, environmental parameters and other information, calculates the pressure drop and temperature drop along the pipeline, and divides and determines the maximum pressure and maximum temperature of each section of the pipeline according to each section of 10 km.

[0049] Specifically:

[0050] 1) Obtain specific parameters such as pipeline outer diameter D, estimated wall thickness t0, minimum yield strength SMYS, end point boundary pressure PB, starting point boundary temperature TB, summer buried temperature TS, components, etc.;

[0051] 2) Using commercial pipeline simulation software, a pipeline transportation model under summer transportation conditions was established to calculate parameters such as along-the-line pressure and along-the-line temperature. The main purpose was to obtain the pressure and temperature data along the pipeline and to construct along-the-line pressure drop and along-the-line temperature drop curves. The purpose of selecting summer transportation conditions is that the underground ambient temperature is higher in summer, which is conducive to obtaining higher along-the-line temperature data of the pipeline. Higher temperatures can cause higher post-rupture pressure steps, which is conducive to identifying more extreme ductile cracking conditions.

[0052] 3) It is preferred that 10 km is a partition, and the pipeline is divided into several partitions, and the maximum operating pressure and maximum operating temperature of each partition along the pipeline are obtained, expressed as Pi and Ti, where i represents the i-th partition; the purpose is to obtain the maximum operating pressure and maximum operating temperature of each section, and provide basic process parameters for verifying the toughness crack arrest capability of each section; further, before the pipeline ruptures, the medium is in a flowing state near the rupture point, and the pressure and temperature are relatively stable. After the rupture, the medium in the pipe near the rupture port is first discharged, and its pressure and temperature show a nearly adiabatic discharge. Although the pressure and temperature conditions of the medium in the pipe at the far end of the rupture port are different from those of the rupture port, it cannot generate energy for the continued cracking of the rupture port, and the driving force for the tearing along the rupture port is still the medium near the rupture port. Therefore, it is appropriate to divide the step intervals to select the maximum pressure and maximum temperature of each interval as the initial conditions for leakage rupture in the step.

[0053] Step S200: Calculate the highest pressure step of each section according to the highest pressure and the highest temperature of each section. According to the highest operating pressure and the highest operating temperature of each partition section, carry out the rupture adiabatic discharge simulation of the corresponding partition section, and obtain the medium pressure in the pipe under the initial condition that the medium in the pipeline is converted into gas-liquid two-phase after the pipeline ruptures and discharges, which is used as the highest pressure step of the partition section.

[0054] Specifically:

[0055] 1) Taking the first partition as the research object, an adiabatic discharge model was established using commercial software according to the obtained maximum operating pressure P1 and maximum operating temperature T1; its purpose is to simulate the adiabatic discharge scenario of the medium when the partition is ruptured during normal operation. During adiabatic discharge, heat exchange between the medium in the pipeline and the external environment is not considered. The temperature of the medium in the pipeline decreases due to the decrease in pressure, and a phase change between gas and liquid will occur.

[0056] 2) Taking the first partition as the research object, the phase state (gas-liquid ratio) of the medium in the pipeline is monitored during the continuous development of the adiabatic discharge. When the gas-liquid ratio is greater than 0, the medium pressure in the pipeline under the corresponding working condition is extracted as the cracking driving force along the first partition, that is, the pressure step, recorded as P1R; its purpose is to provide the rupture driving force parameters for the next step of calculating the wall thickness required for ductile crack arrest of the partition.

[0057] 3) According to the above method, the i-th partition section is taken as the research object. According to the obtained maximum operating pressure Pi and maximum operating temperature Ti, the phase state (gas-liquid ratio) of the medium in the pipeline is monitored during the continuous development of the adiabatic discharge. When the gas-liquid ratio is greater than 0, the medium pressure in the pipeline under the corresponding working condition is extracted as the driving force for the cracking along the i-th partition section, that is, the pressure step, recorded as PiR.

[0058] Step S300: Calculate the wall thickness required for tough crack arrest of each section of the pipeline according to the highest pressure step. According to the basic principle of the modified hyperbola method, the evaluation and analysis of crack arrest toughness based on the modified CVN impact work is performed; according to the CVN impact work requirements of steel pipe manufacturing, combined with empirical correction parameters, the CVN impact work of the calculation model is corrected, and based on the pressure step of step 2 and the aforementioned basic information of the pipeline, the wall thickness required for tough crack arrest of the pipeline is calculated.

[0059] Specifically:

[0060] 1) According to the steel pipe type, outer diameter and material, determine the stable and acceptable CVN impact energy index of the steel pipe product. This index is preferably determined by the steel pipe manufacturer through production experience, past product records, production capacity, etc. This index is defined as the actual CVN impact energy of the steel pipe, recorded as C VR; This data is a key indicator of the crack arrest toughness along the steel pipe and is of great significance for inhibiting cracking along the pipe.

[0061] 2) Taking the first partition as the research object, based on the cracking driving force along the first partition, that is, the pressure step P 1R , as the driving force for the crack arrest toughness evaluation, specifically,

[0062] Ductile cracking trend E N Expressed as

[0063]

[0064] In the formula,

[0065] σ f ——Flow stress of steel pipe, MPa, considered as minimum yield strength + 69MPa

[0066] σ f ——Steel pipe cracking stress, MPa

[0067] E N ——Ductile cracking trend

[0068]

[0069] In the formula,

[0070] D——nominal outer diameter of the pipe, mm

[0071] t i ——The wall thickness of the i-th section of the pipeline (preset), mm. When the first partition is taken as the research object, it is taken as t1

[0072] P iR ——Platform pressure of the i-th segment. When the first partition is taken as the research object, it is taken as P 1R

[0073] 3) Calculate the toughness arrest performance E of the first partition C , the purpose of which is to obtain the toughness crack arrest capacity of the pipeline in this pipe section, expressed as:

[0074]

[0075] In the formula,

[0076] A——Charpy notch area, m2

[0077] C V ——Nominal CVN impact energy, J

[0078] By comparing a large amount of data, it is found that if the nominal CVN impact energy calculated by the hyperbola method is directly used in the ordering standard of steel pipes, it may not meet the requirements of toughness arrest of supercritical CO2 pipelines. Therefore, the nominal CVN impact energy (C V ) should be measured by the actual CVN impact energy (C VR ) is corrected and expressed as:

[0079]

[0080] In the formula,

[0081] C VR ——Actual CVN impact energy, J

[0082] m——Correction coefficient, recommended to be 2 to 2.5

[0083] The ductile crack arrest condition is defined as:

[0084] E C ≥E N (5)

[0085] 4) Calculation of wall thickness required for tough crack arrest: Through the combined equations (1) to (5), after iterative calculation, the required wall thickness t of the pipeline that satisfies the tough crack arrest of the first partition is obtained. 1R .

[0086] 5) Repeat sub-steps 1) to 4) in this step to calculate the wall thickness t required for toughness crack arrest of the remaining partitions iR .

[0087] Thus, the wall thickness required for tough crack arrest of the pipeline in each partition section is obtained.

[0088] Step S400: Calculate the wall thickness according to the internal pressure of the entire pipeline. For the pipeline section where the pipeline medium temperature is higher than the preset threshold, select the wall thickness required for toughness crack arrest as the final wall thickness; for the remaining pipeline sections, select the wall thickness required by the internal pressure as the final wall thickness.

[0089] The pipe wall thickness is determined by the effects of crack arrest and internal pressure, so strength is used as the requirement for wall thickness calculation, and the larger one is preferred.

[0090] Specifically:

[0091] 1) The wall thickness required for the internal pressure of the entire pipeline can be calculated based on strength according to the unified design internal pressure. The design coefficients of different regional grades are taken into account in the calculation, and the calculation method recommended by the industry is adopted.

[0092] 2) Based on the value of the wall thickness required for toughness crack arrest of each partition obtained in step 3, compare it with the value of the wall thickness required for internal pressure in sub-step 1), and select the larger wall thickness value as the recommended wall thickness of each partition of the pipeline.

[0093] Thus, the recommended wall thickness of the pipe in each partition section is obtained.

[0094] This embodiment is based on the basic physical properties of supercritical CO2, the law of phase change, the change of transportation conditions and the characteristics of tough crack arrest of pipelines. Aiming at the problem that the wall thickness selection of long-distance supercritical CO2 transportation pipelines is affected by tough crack arrest, from the perspective of the wall thickness of segmented pipelines, it proposes ideas such as process operation parameter analysis, rupture pressure step calculation, crack arrest toughness evaluation, and internal pressure wall thickness comparison, and forms a design method. The wall thickness design of long-distance supercritical CO2 pipelines achieves safe and efficient control, taking into account the wall thickness required for internal pressure and the wall thickness required for tough crack arrest. Through the segmented design method, the factor "medium temperature" that contributes most to the tough crack arrest ability is segmented (the medium temperature directly affects the driving force of tough cracking), and the wall thickness selection results are achieved that the wall thickness required for tough crack arrest is mainly selected for the front section of the pipeline (higher medium temperature) and the wall thickness required for internal pressure is mainly selected for the rear section of the pipeline (lower medium temperature). Under the condition of fully ensuring the safety of operation, the pipeline investment can be effectively reduced for most supercritical CO2 pipelines.

[0095] Example 2

[0096] Reference Figure 2 ,like Figure 2 The figure shows a structural block diagram of a long-distance supercritical CO2 pipeline wall thickness segmentation design device provided in this embodiment, which specifically includes:

[0097] The maximum pressure and temperature calculation module and the maximum pressure and temperature acquisition module establish a pipeline transportation model according to the parameters required for model establishment, calculate the pressure drop and temperature drop along the pipeline, and divide the pipeline into sections according to the preset length to determine the maximum pressure and maximum temperature of each section;

[0098] A maximum pressure step calculation module, which calculates the maximum pressure step of each section according to the maximum pressure and maximum temperature of each section;

[0099] The module for calculating the wall thickness required for tough crack arrest calculates the wall thickness required for tough crack arrest of each section of the pipeline according to the highest pressure step;

[0100] The final wall thickness calculation module calculates the wall thickness according to the internal pressure of the entire pipeline. For the pipeline section where the pipeline medium temperature is higher than the preset threshold, the wall thickness required for ductile crack arrest is selected as the final wall thickness; for the remaining pipeline sections, the wall thickness required by the internal pressure is selected as the final wall thickness.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A long-distance supercritical CO2 pipeline wall thickness segmentation design method, characterized in that: The method comprises: Establish a pipeline transportation model based on the parameters required for model establishment, calculate the pressure drop and temperature drop along the pipeline, and divide the pipeline into sections according to the preset length to determine the maximum pressure and maximum temperature of each section; Calculate the highest pressure step of each section according to the highest pressure and highest temperature of each section; Calculate the wall thickness required for toughness crack arrest of each section of the pipeline according to the highest pressure step; The wall thickness is calculated based on the internal pressure of the entire pipeline. For pipeline sections where the pipeline medium temperature is higher than the preset threshold, the wall thickness required for ductile crack arrest is selected as the final wall thickness; for the remaining pipeline sections, the wall thickness required by the internal pressure is selected as the final wall thickness.

2. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 1 is characterized in that: The pipeline transportation model includes a pipeline transportation model under summer transportation conditions.

3. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 1 is characterized in that: The calculation of the highest pressure step of each section according to the highest pressure and the highest temperature of each section specifically includes: Establish an adiabatic discharge model based on the maximum pressure and maximum temperature of each section; According to the adiabatic discharge model, each section is simulated for rupture adiabatic discharge to obtain pipeline rupture discharge; When the medium in the pipeline changes into gas-liquid two-phase, the medium pressure in the pipeline under the corresponding working condition is extracted as the highest pressure step of the separation section.

4. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 3 is characterized in that: The transformation of the medium in the pipeline into a gas-liquid two-phase is determined by monitoring the gas-liquid ratio of the medium in the pipeline.

5. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 1 is characterized in that: The calculation of the wall thickness required for toughness crack arrest of each section of the pipeline specifically includes: The highest pressure step in each section is used as the driving force for evaluating the crack arrest toughness and the ductile cracking trend is calculated. The toughness crack arrest performance is calculated by CVN impact energy; The wall thickness required for ductile crack arrest under preset ductile crack arrest conditions is calculated based on the ductile cracking trend and ductile crack arrest performance.

6. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 5 is characterized in that: The CVN impact energy is obtained by correcting the actual CVN impact energy in combination with a preset correction coefficient.

7. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 6 is characterized in that: The actual CVN impact energy is determined according to the steel pipe type, outer diameter and material.

8. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 1 is characterized in that: The calculation of the wall thickness based on the internal pressure of the entire pipeline also includes adding design coefficients for different regional grades.

9. The long-distance supercritical CO2 pipeline wall thickness segmentation design method according to claim 1, characterized in that: The parameters required for establishing the model include the diameter, length, material, composition, boundary pressure, boundary temperature, maximum flow rate, burial depth conditions and environmental parameters of the pipeline.

10. A device for designing the wall thickness of a long-distance supercritical CO2 pipeline by segmentation, characterized in that: The device comprises: A maximum pressure and temperature calculation module, wherein the maximum pressure and temperature acquisition module establishes a pipeline transportation model according to the parameters required for model establishment, calculates the pressure drop and temperature drop along the pipeline, and divides the pipeline into sections according to a preset length to determine the maximum pressure and maximum temperature of each section; A maximum pressure step calculation module, wherein the maximum pressure step calculation module calculates the maximum pressure step of each section according to the maximum pressure and maximum temperature of each section; A module for calculating the wall thickness required for tough crack arrest, wherein the module calculates the wall thickness required for tough crack arrest of each section of the pipeline according to the highest pressure step; The final wall thickness calculation module calculates the wall thickness according to the internal pressure of the entire pipeline. For the pipeline section where the pipeline medium temperature is higher than the preset threshold, the wall thickness required for ductile crack arrest is selected as the final wall thickness; for the remaining pipeline sections, the wall thickness required by the internal pressure is selected as the final wall thickness.

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