A method for predicting crack arrest toughness of supercritical carbon dioxide pipelines

Abstract

The present invention relates to a method for predicting the crack arrest toughness of a supercritical carbon dioxide pipeline, which belongs to the field of carbon dioxide capture, utilization and storage, and specifically includes calculating the supercritical carbon dioxide saturation pressure using supercritical carbon dioxide decompression wave velocity prediction software, and calculating the initial value of the pipeline crack arrest toughness Charpy impact energy based on pipeline size parameters, pipe strength parameters and calculated supercritical carbon dioxide saturation pressure with the help of a supercritical carbon dioxide crack arrest toughness prediction model. Afterwards, the calculated Charpy impact energy is corrected using the CO2 pipeline crack arrest design acceptance standard in DNVGL-RP-F104 (2021). Finally, whether the determined Charpy impact energy correction value can achieve pipe self-crack arrest is verified and further corrected by finite element simulation, and the supercritical carbon dioxide pipeline crack arrest toughness final value is obtained, so that the prediction result is accurate and reliable. The present invention provides favorable guidance for the construction design of supercritical carbon dioxide pipeline engineering, which can effectively reduce construction costs and ensure safe operation of pipelines.

Description

Technical Field

[0001] The present invention belongs to the field of carbon dioxide capture, utilization and storage, and specifically relates to a method for predicting the crack arrest toughness of a supercritical carbon dioxide pipeline. Background Art

[0002] Carbon capture, utilization and storage (CCUS) is one of the most important ways to address global climate change and reduce atmospheric carbon dioxide concentration.

[0003] Research has shown that transporting carbon dioxide through pipelines in a supercritical state is the most economical and efficient method. However, in a supercritical state, pipelines maintain high pressure throughout their entire operation, making the pipe material extremely sensitive to defects and prone to long-range crack propagation, which can cause serious damage to the pipeline and endanger people's lives and property. For example, in the February 2020 carbon dioxide pipeline rupture in Mississippi, the United States, the carbon dioxide plume spread over a range of 30 to 40 kilometers, resulting in the hospitalization of 45 people and the evacuation of over 200. Therefore, research on crack arrest control in supercritical carbon dioxide pipelines has important scientific and theoretical significance and urgent practical engineering needs.

[0004] The core of pipeline crack arrest control lies in predicting the crack arrest toughness of the pipe material. The Battelle Hyperbola (BTC) model, which uses Charpy impact energy as an indicator of crack arrest toughness, is currently the most industrialized and widely used method for predicting crack arrest toughness in natural gas pipelines. To validate this method for supercritical CO2 pipelines, a total of 11 full-scale explosion tests were conducted in the United States, Europe, and other locations. The results showed that this model significantly underestimated the toughness required for crack arrest in supercritical CO2 pipelines. Despite extensive research on crack arrest control in supercritical CO2 pipelines by research institutions and scholars both domestically and internationally, a systematic and reliable method for predicting crack arrest toughness has yet to be established, becoming a bottleneck limiting the construction of supercritical CO2 pipelines. Summary of the Invention

[0005] In order to overcome the defects of the prior art, the present invention provides a method for predicting the crack arrest toughness of a supercritical carbon dioxide pipeline.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for predicting crack arrest toughness of a supercritical carbon dioxide pipeline comprises the following steps:

[0008] 1) According to the supercritical carbon dioxide transportation requirements, determine the specifications of the supercritical carbon dioxide pipeline, basic mechanical properties of the pipe, design temperature and design pressure P0; the specifications of the supercritical carbon dioxide pipeline include: supercritical carbon dioxide pipeline outer diameter D and supercritical carbon dioxide pipeline wall thickness t; the basic mechanical properties of the pipe include: pipe yield strength σ y and elastic modulus E of the pipe;

[0009] 2) Calculate the supercritical carbon dioxide saturation pressure P using supercritical carbon dioxide decompression wave velocity prediction software d The input parameters include temperature, pressure, and molar percentage of each supercritical carbon dioxide component, and the output is the supercritical carbon dioxide saturation pressure P d ;

[0010] 3) The crack arrest toughness prediction model of supercritical carbon dioxide pipeline is used to calculate the Charpy impact energy C of the crack arrest toughness of supercritical carbon dioxide pipeline. V The initial value is calculated, and the input is the supercritical carbon dioxide pipeline outer diameter D, supercritical carbon dioxide pipeline wall thickness t, pipe yield strength σ y , the elastic modulus E of the pipe and the supercritical carbon dioxide saturation pressure P determined in step 2) d The output is the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C V Initial value;

[0011] 4) According to the outer diameter D of the supercritical carbon dioxide pipeline, the wall thickness t of the supercritical carbon dioxide pipeline, and the yield strength σ of the pipe y , elastic modulus E of the pipe, supercritical carbon dioxide saturation pressure P determined in step 2) d and the Charpy impact energy C determined in step 3) V Initial value calculation: X-axis and Y-axis in the ductile fracture arrest assessment diagram for CO2 pipelines in DNVGL-RP-F104 (2021);

[0012] 5) Determine the Charpy impact energy C determined in step 3) based on the values ​​of the abscissa X and ordinate Y obtained in step 4) V Does the initial value meet the crack arrest acceptance requirements of DNVGL-RP-F104(2021)? If not, use the Charpy impact energy C determined in step 3) V Based on the initial value, the Charpy impact energy C is gradually increased with a gradient of 1J. V The horizontal and vertical coordinates X and Y are recalculated at the same time until the crack arrest acceptance requirements of DNVGL-RP-F104 (2021) are met; the Charpy impact energy C is specified at this time. V The Charpy impact energy C is the crack arrest toughness of supercritical carbon dioxide pipeline V Correction value;

[0013] 6) Use finite element software to establish a standard Charpy impact test finite element model, and use a trial algorithm to determine a set of material damage parameters based on the Charpy impact test finite element simulation, so that the Charpy impact energy C V The simulated value and the Charpy impact energy C of the supercritical carbon dioxide pipeline crack arrest toughness determined in step 5) V The difference in the correction value is within 1J;

[0014] 7) Using finite element software to establish a finite element model of the supercritical carbon dioxide pipeline with cracks, assign the material damage parameters determined in step 6) to the finite element model of the supercritical carbon dioxide pipeline, and calculate the saturation pressure P0 based on the design pressure P0 and the saturation pressure P0 determined in step 2). d Apply loads to the pipeline to simulate crack growth in supercritical carbon dioxide pipelines;

[0015] 8) Based on the simulation results of step 7), determine whether the pipeline crack can stop by itself. If the crack stops by itself, it proves that the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C determined in step 5) is V The correction value meets the requirements for pipeline crack arrest; if crack arrest is not possible, the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C determined in step 5) is used. V The correction value is based on the 1J gradient, and the Charpy impact energy C is gradually increased. V Repeat steps 6) and 7) until the cracks in the simulated supercritical carbon dioxide pipeline stop by themselves. The Charpy impact energy C at this time is specified as V The Charpy impact energy C is the crack arrest toughness of supercritical carbon dioxide pipeline V Final value.

[0016] The supercritical carbon dioxide pipeline crack arrest toughness prediction model described in step 3) is as shown in formula (1):

[0017]

[0018] Among them, C V is the Charpy impact energy, J; A is the ligament area of ​​the Charpy impact specimen, A = 80 mm 2 ; σ f is the flow stress, MPa, σ f =σ y +68.9MPa;σ y is the yield strength, MPa; D is the outer diameter of the pipe, mm; t is the wall thickness of the pipe, mm; E is the elastic modulus, MPa; σ d is the crack tip annular stress of supercritical carbon dioxide pipeline, MPa, σ d =P d D / 2t;P d is the supercritical carbon dioxide saturation pressure.

[0019] The horizontal coordinate X and the vertical coordinate Y in the CO2 pipeline ductile fracture arrest assessment diagram in DNVGL-RP-F104 (2021) described in step 4) are calculated according to the following formula:

[0020]

[0021] The DNVGL-RP-F104 (2021) crack arrest acceptance requirements described in step 5) are: when 25≤X<40, Y≤0.23+0.00267(X-25); when X≥40, Y≤0.27; all other situations are considered to not meet the DNVGL-RP-F104 (2021) crack arrest acceptance requirements.

[0022] Step 6) The material damage parameters specifically include the initial pore volume fraction f0, the volume fraction of nucleable two-phase particles f N , critical polymer void volume fraction f c , fracture void volume fraction f F , material damage parameters q1, q2, q3, average equivalent plastic strain ε N and its standard deviation S N .

[0023] The present invention has the following beneficial effects:

[0024] The present invention provides a supercritical carbon dioxide crack arrest toughness prediction method, which uses a supercritical carbon dioxide pipeline crack arrest toughness prediction model to determine its crack arrest toughness Charpy impact energy initial value, uses DNVGL-RP-F104 (2021) crack arrest acceptance requirements to verify whether the initial value meets the crack arrest requirements, and corrects it to obtain the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy correction value. On this basis, the correction value is verified again with the help of finite element simulation to verify whether it can meet the pipeline crack arrest requirements, and the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy final value is obtained, which provides effective guidance for the supercritical carbon dioxide pipeline crack arrest design. The above method includes multiple verifications and corrections, which ensures the accuracy of the final crack arrest toughness prediction results, improves the reliability of the supercritical carbon dioxide pipeline crack arrest design, reduces the possibility of long-range crack propagation accidents, and has high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flowchart of the method for predicting supercritical carbon dioxide crack arrest toughness of the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in further detail below with reference to the accompanying drawings:

[0027] like Figure 1 As shown, the present invention provides a method for predicting supercritical carbon dioxide crack arrest toughness, which is characterized by comprising the following steps:

[0028] 1) According to the supercritical carbon dioxide transportation requirements, determine the specifications of the supercritical carbon dioxide pipeline, including the outer diameter D and wall thickness t, and the basic mechanical properties of the pipe, such as the yield strength σ y and elastic modulus E, design temperature, and design pressure P0.

[0029] 2) Calculate the supercritical carbon dioxide saturation pressure P using supercritical carbon dioxide decompression wave velocity prediction software d The input parameters include temperature, pressure, and molar percentage of each supercritical carbon dioxide component, and the output is the supercritical carbon dioxide saturation pressure P d .

[0030] 3) The crack arrest toughness prediction model of supercritical carbon dioxide pipeline is used to calculate the Charpy impact energy C of the crack arrest toughness of supercritical carbon dioxide pipeline. V The initial value is calculated, and the input is the supercritical carbon dioxide pipeline outer diameter D, supercritical carbon dioxide pipeline wall thickness t, pipe yield strength σ y , pipe elastic modulus E and supercritical carbon dioxide saturation pressure P d The output is the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C V Initial value;

[0031]

[0032] Among them, C V is the Charpy impact energy, J; A is the ligament area of ​​the Charpy impact specimen, A = 80 mm 2 ; σ f is the flow stress, MPa, σ f =σ y +68.9MPa;σ y is the yield strength, MPa; D is the outer diameter of the pipe, mm; t is the wall thickness of the pipe, mm; E is the elastic modulus, MPa; σ d is the crack tip annular stress of supercritical carbon dioxide pipeline, MPa, σ d =P d D / 2t;P d is the supercritical carbon dioxide saturation pressure.

[0033] 4) According to the outer diameter D of the supercritical carbon dioxide pipeline, the wall thickness t of the supercritical carbon dioxide pipeline, and the yield strength σ of the pipe y , elastic modulus E of the pipe, supercritical carbon dioxide saturation pressure P determined in step 2) d and the Charpy impact energy C determined in step 3) V The initial values ​​are substituted into the following formulas (2) and (3) to calculate the horizontal coordinate X and the vertical coordinate Y in the ductile fracture arrest assessment diagram of CO2 pipelines in DNVGL-RP-F104 (2021);

[0034]

[0035] 5) Determine the Charpy impact energy C determined in step 3) based on the values ​​of the abscissa X and ordinate Y obtained in step 4) VDoes the initial value meet the crack arrest acceptance requirements of DNVGL-RP-F104(2021)? If not, use the Charpy impact energy C determined in step 3) V Based on the initial value, the Charpy impact energy C is gradually increased with a gradient of 1J. V The horizontal and vertical coordinates X and Y are recalculated at the same time until the crack arrest acceptance requirements of DNVGL-RP-F104 (2021) are met; the Charpy impact energy C is specified at this time. V The Charpy impact energy C is the crack arrest toughness of supercritical carbon dioxide pipeline V Correction value;

[0036] The DNVGL-RP-F104 (2021) crack arrest acceptance requirements are: when 25≤X<40, Y≤0.23+0.00267(X-25); when X≥40, Y≤0.27; all other situations are considered to not meet the DNVGL-RP-F104 (2021) crack arrest acceptance requirements.

[0037] 6) Use finite element software to establish a standard Charpy impact test finite element model, and use a trial algorithm to determine a set of material damage parameters based on the Charpy impact test finite element simulation, so that the Charpy impact energy C V The simulated value and the Charpy impact energy C of the supercritical carbon dioxide pipeline crack arrest toughness determined in step 5) V The difference in the correction value is within 1J;

[0038] The material damage parameters specifically include the initial pore volume fraction f0, the volume fraction of nucleable two-phase particles f N , critical polymer void volume fraction f c , fracture void volume fraction f F , material damage parameters q1, q2, q3, average equivalent plastic strain ε N and its standard deviation S N .

[0039] 7) Using finite element software to establish a finite element model of the supercritical carbon dioxide pipeline with cracks, assign the material damage parameters determined in step 6) to the finite element model of the supercritical carbon dioxide pipeline, and calculate the saturation pressure P0 based on the design pressure P0 and the saturation pressure P0 determined in step 2). d Apply loads to the pipeline to simulate crack growth in a supercritical carbon dioxide pipeline.

[0040] 8) Based on the simulation results of step 7), determine whether the pipeline crack can stop by itself. If the crack stops by itself, it proves that the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C determined in step 5) is V The correction value meets the requirements for pipeline crack arrest; if crack arrest is not possible, the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C determined in step 5) is used. VThe correction value is based on the 1J gradient, and the Charpy impact energy C is gradually increased. V Repeat steps 6) and 7) until the cracks in the simulated supercritical carbon dioxide pipeline stop by themselves. The Charpy impact energy C at this time is specified as V The Charpy impact energy C is the crack arrest toughness of supercritical carbon dioxide pipeline V Final value.

[0041] The following is an example to illustrate:

[0042] (1) The planned annual output of a supercritical carbon dioxide pipeline demonstration project is 1.4 million tons. Based on the output requirement, the outer diameter D of the pipeline is determined to be 219 mm, the wall thickness t is 10 mm, and the pipe material is X65 steel grade. Its yield strength σ y The elastic modulus E is 206 GPa, and the design pressure P0 is 16 MPa.

[0043] (2) The components of transported supercritical carbon dioxide are shown in Table 1. The saturation pressure P is calculated using supercritical carbon dioxide decompression wave velocity prediction software. d It is 9.17MPa.

[0044] Table 1 Supercritical carbon dioxide components

[0045] Natural gas components carbon dioxide Nitrogen methane oxygen Mole percentage 95％ 2％ 2％ 0％

[0046] (3) The Charpy impact energy C of the crack arrest toughness of supercritical carbon dioxide pipeline is calculated according to formula (1). V The initial value is 48.18J.

[0047] (4) According to formula (2) and formula (3), under the above parameters, the horizontal coordinate X and the vertical coordinate Y in the CO2 pipeline ductile fracture arrest assessment diagram in DNVGL-RP-F104 (2021) are 13.92 and 0.19 respectively.

[0048] (5) According to the crack arrest acceptance requirements of DNVGL-RP-F104 (2021), X<25, so the current supercritical carbon dioxide pipeline has a Charpy impact energy C V When the impact strength is 48.18J, the crack arrest requirement cannot be met. On the basis of 48.18J, the Charpy impact energy C is gradually increased with a gradient of 1J. V It is found that when the Charpy impact energy C V When the crack arrest toughness of supercritical carbon dioxide pipeline is 87.18J, the calculated X and Y are 25.03 and 0.19 respectively, which meets the DNVGL-RP-F104 (2021) crack arrest acceptance requirements. Therefore, the Charpy impact energy C of the crack arrest toughness of supercritical carbon dioxide pipeline is determined. V The corrected value is 87.18J.

[0049] (6) The finite element software Abaqus was used to establish a standard Charpy impact test finite element model, and a set of material damage parameters was assigned to the model. The Charpy impact energy corresponding to the material damage parameters was obtained by integrating the load-displacement curve obtained by simulation. By changing the value of the material damage parameter, the simulated Charpy impact energy was made close to 87.18 J until the difference between the two was less than 1 J. A set of material damage parameters determined by this method is shown in Table 2.

[0050] Table 2 Material damage parameters

[0051] Damage parameters <![CDATA[q1]]> <![CDATA[q2]]> <![CDATA[q3]]> <![CDATA[ε N ]]> <![CDATA[S N ]]> <![CDATA[f N ]]> <![CDATA[f0]]> <![CDATA[f F ]]> <![CDATA[f c ]]> Value 1.5 1 2.25 0.3 0.1 0.0008 0.00075 0.25 0.01

[0052] 7) Use finite element software to establish a finite element model of a supercritical carbon dioxide pipeline with cracks, assign the material damage parameters in Table 2 to the model, and calculate the saturation pressure P0 based on the design pressure P0 and the saturation pressure P0 determined in step 2). d Apply loads to the pipeline to simulate crack growth in a supercritical carbon dioxide pipeline.

[0053] 8) The simulation results show that the cracks in the pipeline eventually stop by themselves, which further proves that when the Charpy impact energy of the pipe is 87.18J, the crack arrest requirement of the pipeline is met. Therefore, the Charpy impact energy of the supercritical carbon dioxide pipeline is C V The final value is 87.18J.

Claims

1. A method for predicting crack arrest toughness of supercritical carbon dioxide pipelines, characterized in that: The following steps are involved: 1) According to the supercritical carbon dioxide transportation requirements, determine the specifications of the supercritical carbon dioxide pipeline, basic mechanical properties of the pipe material, design temperature and design pressure P0; 2) Calculate the supercritical carbon dioxide saturation pressure P using supercritical carbon dioxide decompression wave velocity prediction software d ; 3) The following supercritical carbon dioxide pipeline crack arrest toughness prediction model is used to calculate the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C V Calculate the initial value; Among them, C V is the Charpy impact energy, J; A is the ligament area of ​​the Charpy impact specimen, A = 80 mm 2 ; σ f is the flow stress, MPa, σ f =σ y +68.9MPa;σ y is the yield strength, MPa; D is the outer diameter of the pipe, mm; t is the wall thickness of the pipe, mm; E is the elastic modulus, MPa; σ d is the crack tip annular stress of supercritical carbon dioxide pipeline, MPa, σ d =P d D / 2t;P d is the supercritical carbon dioxide saturation pressure; 4) Calculate the horizontal coordinate X and vertical coordinate Y in the ductile fracture arrest assessment diagram for CO2 pipelines in DNVGL-RP-F104 (2021); 5) Determine the Charpy impact energy C determined in step 3) based on the values ​​of the abscissa X and ordinate Y obtained in step 4) V Does the initial value meet the DNVGL-RP-F104 (2021) crack arrest acceptance requirements? If not, gradually increase the Charpy impact energy C by 1J. V The horizontal and vertical coordinates X and Y are recalculated at the same time until the crack arrest acceptance requirements of DNVGL-RP-F104(2021) are met; 6) Using trial and error method to determine a set of material damage parameters based on finite element simulation of Charpy impact test, the Charpy impact energy C V The simulated value and the Charpy impact energy C of the supercritical carbon dioxide pipeline crack arrest toughness determined in step 5) V The difference in the correction value is within 1J; 7) The material damage parameters determined in step 6) are assigned to the supercritical carbon dioxide pipeline finite element model, and the saturation pressure P determined in step 2) is calculated based on the design pressure P0. d Apply loads to the pipeline to simulate crack growth in supercritical carbon dioxide pipelines; 8) Based on the simulation results of step 7), determine whether the pipeline crack can stop by itself. If the crack stops by itself, it proves that the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C determined in step 5) is V The correction value meets the requirements for pipeline crack arrest; if crack arrest is not possible, the supercritical carbon dioxide pipeline crack arrest toughness Charpy impact energy C determined in step 5) is used. V The correction value is based on the 1J gradient, and the Charpy impact energy C is gradually increased. V Repeat steps 6) and 7) until the cracks in the simulated supercritical carbon dioxide pipeline stop cracking by themselves. At this time, the Charpy impact energy C V The Charpy impact energy C is the crack arrest toughness of supercritical carbon dioxide pipeline V Final value.

2. The method for predicting crack arrest toughness of supercritical carbon dioxide pipeline according to claim 1, characterized in that: The horizontal coordinate X and vertical coordinate Y in the ductile fracture arrest assessment diagram of CO2 pipelines in DNVGL-RP-F104 (2021) are calculated according to the following formula:

3. The method for predicting crack arrest toughness of supercritical carbon dioxide pipeline according to claim 1, characterized in that: The DNVGL-RP-F104(2021) crack arrest acceptance requirements are: when 25≤X<40, Y≤0.23+0.00267(X-25); when X≥40, Y≤0.27; all other situations are considered to not meet the DNVGL-RP-F104(2021) crack arrest acceptance requirements.

4. The method for predicting crack arrest toughness of supercritical carbon dioxide pipeline according to claim 1, characterized in that: The material damage parameters include the initial pore volume fraction f0, the volume fraction of nucleable two-phase particles f N , critical polymer void volume fraction f c , fracture void volume fraction f F , material damage parameters q1, q2, q3, average equivalent plastic strain ε N and its standard deviation S N .

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