Method for calculating water addition amount in CO2 conveying environment corrosion simulation experiment

Abstract

The invention provides a method for calculating the water addition amount in a CO2 conveying environment corrosion simulation experiment, and relates to the technical field of corrosion and protection of materials. The method comprises the following steps: step 1, setting a target volume fraction # imgabs 0 # of H2O in CO2 in a corrosion simulation experiment system; step 2, obtaining a saturated volume fraction # imgabs 2 # of H2O in CO2 and a saturated mass mH2O of H2O in CO2 based on the target volume fraction # imgabs 1 # in the corrosion simulation experiment system under set temperature and pressure conditions, determining the water addition amount mi in the corrosion simulation experiment system; according to the method provided by the invention, the calculation conversion of the corresponding water content and mass in the corrosion simulation experiment of the CO2 conveying environment under different temperature and pressure conditions can be realized. In addition, the method provided by the invention can be used as a theoretical basis of water content calculation software, and is beneficial to development of the water content calculation software.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion and protection of materials, and particularly relates to a method for calculating the water addition amount in a corrosion simulation experiment for a CO2 transportation environment. Background Art

[0002] For a relatively long time in the future, fossil fuels such as oil and natural gas will still be one of the main energy sources for the development of human society. However, during the combustion and use of these fossil fuels, a large amount of greenhouse gases such as CO2 will be generated, leading to environmental problems such as climate warming. Carbon Capture, Utilization and Storage (CCUS) refers to the process of separating CO2 from industrial or related emission sources, transporting it through pipelines to the storage site, and isolating it from the atmosphere for a long time. In the CCUS process, pipeline transportation is a key link to ensure the safe and efficient transportation of CO2 from the capture site to the destination.

[0003] During the CO2 transportation process, the change in the water content in CO2 will significantly affect the corrosion degree of the transportation pipeline. Therefore, in the actual CO2 transportation process, in order to reduce the corrosion of pipeline steel, the water content in the CO2 fluid is usually controlled at a relatively low level. However, currently, during the research on the corrosion problem of CO2 transportation pipelines, the water content in the corrosion simulation system is mostly in a supersaturated state, that is, there is no accurate limit on the water addition amount, so as to ensure that the corrosion system always maintains a saturated water content state within the experimental period. In recent years, in order to ensure the accuracy of corrosion simulation experiments, more and more researchers have begun to turn their attention to the CO2 transportation corrosion simulation system with low water content. However, compared with the saturated water content system, there is currently no set of standardized and reasonable water content calculation methods applicable to the corrosion simulation experiment of the CO2 transportation environment in the low water content system, resulting in difficulty in determining the accurate water addition amount corresponding to the low water content during the corrosion simulation experiment.

[0004] Therefore, in the technical field of corrosion and protection of materials, how to establish a calculation method for the water addition amount applicable to the corrosion simulation experiment of the CO2 transportation environment has become an urgent technical problem to be solved currently. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for calculating the water addition amount in a corrosion simulation experiment for a CO2 transportation environment, and the method includes:

[0006] Step 1: Set the target volume fraction of H2O in CO2 in the corrosion simulation experiment system

[0007] Step 2: Based on the target volume fraction The saturated volume fraction of H2O in CO2 obtained under the set temperature and pressure conditions in the corrosion simulation experiment system and the saturated mass of H2O in CO2 Determine the water addition amount m in the corrosion simulation experiment system i ; wherein,

[0008] Preferably, the calculation method of the saturated mass of H2O in CO2 includes:

[0009] Determine the density of CO2 under the set temperature and pressure conditions

[0010] According to the density of CO2 and the reaction volume of the corrosion simulation experiment system Determine the total mass of CO2 in the corrosion simulation experiment system wherein,

[0011] Based on the total mass of CO2 Determine the total molar amount of CO2 wherein,

[0012] According to the total molar amount of CO2 and the solubility of H2O in CO2 under the set temperature and pressure conditions Calculate the saturated molar amount of H2O in CO2 wherein,

[0013] Based on the saturated molar amount of H2O in CO2 Obtain the saturated mass of H2O in CO2 wherein,

[0014] Preferably, the calculation method of the saturated volume fraction of H2O in CO2 includes:

[0015] According to the saturated mass of H2O in CO2 The total mass of CO2 Calculate the saturated mass fraction of H2O in CO2 wherein,

[0016] According to the obtained saturated mass fraction of H2O in CO2 Obtain the saturated volume fraction of H2O in CO2 wherein,

[0017] Preferably, under the set temperature and pressure conditions, the CO2 in the CO2 transportation environment corrosion simulation experiment is in a gaseous, liquid or supercritical state.

[0018] Preferably, the reaction volume of the corrosion simulation experiment system is the volume of the high-temperature and high-pressure autoclave.

[0019] Preferably, the solubility of H2O in CO2 is the solubility of H2O in CO2 under the set temperature and pressure conditions obtained based on the CO2-H2O mutual solubility model.

[0020] Preferably, the solubility of H2O in CO2 under the set temperature and pressure conditions obtained based on the CO2-H2O mutual solubility model includes:

[0021] Substitute the set temperature into the calculation formula of the fugacity coefficient and the calculation formula of the standard equilibrium constant to obtain the fugacity coefficient and the standard equilibrium constant;

[0022] Substitute the calculated fugacity coefficient, the standard equilibrium constant, and the set pressure into the CO2-H2O mutual solubility model to calculate the solubility of H2O in CO2.

[0023] Preferably, the calculation formula of the fugacity coefficient is:

[0024]

[0025] Wherein, is the fugacity coefficient of component i or component j in the CO2-H2O mixed system; V is the molar volume of the CO2-H2O mixed fluid; b mix and a mix are the characteristic parameters of the CO2-H2O mixed fluid, b i / j is the characteristic parameter of the component i or the component j, a ij is the gravitational parameter between the component i and the component j; x i / j is the mole fraction of the component i or the component j in the CO2 phase; R is the gas constant; T is the set temperature; P is the set pressure; j is CO2, and i is H2O.

[0026] Preferably, the calculation formula of the standard equilibrium constant is:

[0027]

[0028] Wherein, is the equilibrium constant of component i or component j in the CO2-H2O mixed fluid under standard pressure (0.1 MPa); T is the set temperature; A, B, C, and D are regression coefficients; j is CO2, and i is H2O.

[0029] Preferably, the CO2-H2O mutual solubility model is:

[0030]

[0031]

[0032] where Y H2O is the mole fraction of H2O in the CO2 phase; is the fugacity coefficient of H2O; is the equilibrium constant of H2O under standard pressure; X H2O is the mole fraction of H2O in the liquid phase; P is the set pressure; P 0 is the standard pressure of 0.1 MPa; is the average partial molar volume of H2O between pressure P 0 -P; R is the gas constant; T is the set temperature;

[0033] X CO2 is the mole fraction of CO2 in the liquid phase; is the fugacity coefficient of CO2; is the equilibrium constant of CO2 under standard pressure; Y H2O is the mole fraction of H2O in the CO2 phase; P is the set pressure; P 0 is the standard pressure of 0.1 MPa; is the average partial molar volume of CO2 between pressure P 0 -P; R is the gas constant; T is the set temperature.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The present invention provides a method for calculating the water addition amount in a CO2 transportation environment corrosion simulation experiment, which relates to the technical field of corrosion and protection of materials. The method includes: Step 1: Set the target volume fraction of H2O in CO2 in the corrosion simulation experiment system Step 2: Based on the target volume fraction The saturated volume fraction of H2O in CO2 obtained under the set temperature and pressure conditions in the corrosion simulation experiment system and the saturated mass of H2O in CO2 determine the water addition amount m i in the corrosion simulation experiment system; where The method provided by the present invention can realize the calculation conversion of the corresponding water content and mass in the corrosion simulation experiment of CO2 transportation environment under different temperature and pressure conditions. In addition, the method provided by the present invention can be used as the theoretical basis for the water content calculation software, which helps to develop the water content calculation software.

[0036] The method provided by the embodiment of the present invention has a simple process and accurate calculation results, which can effectively ensure the reliability of the experimental results and avoid the experimental result errors caused by inaccurate water addition. By using the method provided by the present invention, the target volume fraction of H2O in CO2 in the corrosion simulation experiment system under different set temperatures and pressures can be accurately calculated. The corresponding accurate water addition amount can be obtained, so as to realize the calculation conversion of the corresponding water content (target volume fraction) and mass (water addition amount) in the corrosion simulation experiment of CO2 transportation environment under different temperature and pressure conditions. By using the accurate water addition amount, the water content of CO2 in the corrosion simulation experiment system can be controlled to be consistent with that of CO2 in the actual transportation pipeline, so as to ensure the accuracy of the corrosion simulation experiment. Brief Description of the Drawings

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is a method step diagram for calculating the water addition amount in the corrosion simulation experiment of CO2 transportation environment provided by the embodiment of the present invention;

[0039] Figure 2 It is a method flow chart for calculating the water addition amount in the corrosion simulation experiment of CO2 transportation environment provided by the embodiment of the present invention. Detailed Embodiments

[0040] The following embodiments are provided to better understand the present invention further. They are not limited to the best implementation mode, and do not limit the content and protection scope of the present invention. Any product obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features and being the same as or similar to the present invention falls within the protection scope of the present invention.

[0041] In the embodiments, if the specific experimental procedures or conditions are not specified, the operations or conditions of the conventional experimental procedures described in the existing technologies in the art can be followed. For the reagents and other instruments whose manufacturers are not specified, they are all conventional reagent products that can be obtained through commercial purchases. In addition, the attached drawings are only schematic diagrams of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus the repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0042] For a relatively long time in the future, fossil fuels such as petroleum and natural gas will still be one of the main energy sources for the development of human society. However, a large amount of greenhouse gases such as CO2 will be generated during the combustion and use of these fossil fuels, leading to environmental problems such as climate warming. Carbon Capture, Utilization and Storage (CCUS) refers to the process of separating CO2 from industrial or related emission sources, transporting it through pipelines to the storage site, and isolating it from the atmosphere for a long time. The pipeline transportation of CO2 has the advantages of strong continuity, sustainable utilization, low cost, high efficiency, etc., and is currently the best way to transport CO2 overall. Transporting CO2 from the gas source to a suitable place for storage or utilization has high economic benefits, and at the same time, it can also protect the environment and reduce air pollution. Among them, supercritical transportation is the main way for future CO2 pipeline transportation. In the CCUS process, using pipeline transportation is the key link to ensure the safe and efficient transportation of CO2 from the capture site to the destination. During the actual transportation of CO2, the change in the water content in CO2 will significantly affect the corrosion degree of the transportation pipeline. Therefore, during the actual transportation of CO2, in order to reduce the corrosion of pipeline steel, it is usually necessary to control the water content in the CO2 fluid at a relatively low level, so as to avoid the carbonic acid formed by the reaction of water and CO2 from corroding the pipeline steel and equipment. At the same time, it can also prevent the formation of hydrates by water from blocking the pipeline and even damaging the equipment; this low water content should ensure that free water does not form within the entire pipeline transportation pressure and temperature range.

[0043] During the actual CO2 transportation process, the water in CO2 is not artificially added, but inherently exists in the CO2 gas. Moreover, the actual transportation conditions are complex, and it is impossible to control the water content in CO2. Therefore, the water content (in ppmv, i.e., the volume fraction of H2O in CO2) during the actual CO2 transportation process is usually directly measured by equipment. For example, the water content in the CO2 transportation pipeline is actually measured to be 600 ppmv. In the corrosion simulation experiment system for the CO2 transportation environment, by artificially adding a certain mass of water (in g) to the CO2 gas, CO2 with a specific water content (in ppmv, i.e., the volume fraction of H2O in CO2) is obtained to control the water content in CO2, and then the corrosion simulation experiment of pipeline steel is carried out using this CO2 system.

[0044] In the prior art, the water content of CO2 in the corrosion simulation experiment system for the CO2 transportation environment is mostly in a supersaturated state. Usually, when introducing water into the CO2 gas, there is no accurate limit on the added amount of water, that is, the solubility of H2O in CO2 reaches the upper limit. At this time, the water introduced into CO2 undergoes phase separation and cannot continue to dissolve, indicating that the water content in CO2 at this time remains in a saturated state, and there is no need to consider the problem of excessive water addition. In order to reduce the corrosion of pipeline steel, it is usually necessary to control the water content of CO2 in the actual transportation pipeline at a relatively low level. Therefore, in order to ensure the accuracy of the corrosion simulation experiment, when conducting the corrosion simulation experiment for the CO2 transportation environment, it is necessary to control the water content in CO2 to be the same as the low water content in the actual transportation pipeline. However, at this time, it is not clear how much mass of water needs to be artificially introduced into the CO2 gas before the start of the corrosion simulation experiment to obtain the same low water content value as in the actual transportation pipeline. If the added water amount is excessive, it will cause changes in the water concentration in CO2.

[0045] In view of this, the present invention provides a method for calculating the water addition amount in the corrosion simulation experiment for the CO2 transportation environment. By setting the target water content and the saturated volume fraction of H2O in CO2 in the corrosion simulation experiment system under the set temperature and pressure conditions the saturated mass of H2O in CO2 the water addition amount m in the corrosion simulation experiment system is calculated i , thereby determining the water addition amount m corresponding to the target water content i ​, the calculation conversion from the corresponding target volume fraction to mass in the corrosion simulation experiment of the CO2 transportation environment is realized. By using the accurate mass, the water content of CO2 in the corrosion simulation experiment system can be controlled to be the same as that of CO2 in the actual transportation pipeline, so as to ensure the accuracy of the corrosion simulation experiment. In addition, the method provided by the present invention has a simple process and accurate calculation results, can effectively ensure the reliability of the experimental results, avoid the experimental result errors caused by inaccurate water addition amount, and can also be used as the theoretical basis for the water content calculation software, which is helpful for the development of the water content calculation software.

[0046] The present invention provides a method for calculating the water addition amount in the corrosion simulation experiment of the CO2 transportation environment, referring to Figure 1 , Figure 1 is the flowchart of the method for calculating the water addition amount in the corrosion simulation experiment of the CO2 transportation environment provided by the embodiment of the present invention. The method includes:

[0047] S1, setting the target volume fraction of H2O in CO2 in the corrosion simulation experiment system

[0048] The target volume fraction of H2O in CO2 is the required target water content in CO2. This target water content is the known water content obtained according to the on-site working conditions when actually transporting CO2 through the pipeline, and the water content in the corrosion simulation system is set to this target water content obtained under the on-site working conditions to conduct the corrosion simulation experiment of the CO2 transportation environment. It should be noted that there is no specific limit on the size of the target volume fraction , and this target water content is only related to the on-site working conditions; when this target water content is a low water content value, such as the target volume fraction of H2O in CO2 is 100 ppm v , research experiments on the corrosion mechanism, corrosion rate, and new pipeline materials of pipeline steel can be carried out at this low water content to ensure the safe and stable operation of the actual CO2 transportation pipeline, storage equipment, etc.; when this target water content is a high water content value, relevant corrosion research can also be carried out at this high water content to ensure the safe and stable operation of the actual CO2 transportation pipeline, storage equipment, etc.

[0049] Exemplarily, set the target volume fraction of H2O in CO2 to 100 ppm v , therefore, after introducing a certain mass of water, the water content of CO2 in the corrosion simulation experiment of the CO2 transportation environment is 100 ppm v , and research on the corrosion mechanism, corrosion rate, and new pipeline materials of pipeline steel is carried out at this low water content to safely transport CO2 to the destination.

[0050] S2, based on the target volume fraction The saturated volume fraction of H2O in CO2 obtained in the corrosion simulation experiment system under the set temperature and pressure conditions And the mass of saturated H2O in CO2 Determine the water addition amount m in the corrosion simulation experiment system i ; wherein,

[0051] Wherein, the set temperature and pressure are the temperature and pressure obtained according to the on-site working conditions when actually transporting CO2 through the pipeline. Therefore, the specific values of the set temperature and pressure are not specifically limited.

[0052] Wherein, the saturated volume fraction of H2O in CO2 And the mass of saturated H2O in CO2 Are the saturated volume fraction and saturated mass of H2O under the set temperature and pressure conditions in the corrosion simulation experiment system provided by the present invention.

[0053] Specifically, by using the saturated parameters to calculate the unsaturated parameters, the actual water addition amount m i / The mass of saturated H2O in CO2 under the set temperature and pressure conditions Is equal to the target volume fraction In the saturated volume fraction in CO2 That is, by using the known target volume fraction And through the mass of saturated H2O in CO2 under the set temperature and pressure conditions And the saturated volume fraction of H2O in CO2 Calculate the unsaturated parameter - the actual water addition amount m i , and convert the target volume fraction in the corrosion simulation experiment system provided by the present invention into mass.

[0054] The method provided by the embodiment of the present invention has a simple process and accurate calculation results, can effectively ensure the reliability of the experimental results, and avoids the experimental result errors caused by inaccurate water addition amount. By using the method provided by the present invention, the target volume fraction of H2O in CO2 in the corrosion simulation experiment system under the set temperature and pressure conditions can be accurately calculated The corresponding accurate water addition amount is obtained, thus realizing the calculation conversion between the corresponding water content (target volume fraction) and mass (water addition amount) in the CO2 transportation environmental corrosion simulation experiment under different temperature and pressure conditions. By using the accurate water addition amount, the water content of CO2 in the corrosion simulation experiment system can be controlled to be consistent with that in the actual transportation pipeline, so as to ensure the accuracy of the corrosion simulation experiment. In addition, the method provided by the present invention can be used as the theoretical basis for the water content calculation software, which helps to develop the water content calculation software.

[0055] In some embodiments, the mass of H2O saturated in CO2 is calculated as follows:

[0056] Determine the density of CO2 under the set temperature and pressure conditions

[0057] According to the density of the CO2 and the reaction volume of the corrosion simulation experiment system Determine the total mass of CO2 in the corrosion simulation experiment system Wherein,

[0058]

[0059] Based on the total mass of the CO2 Determine the total molar amount of CO2 Wherein,

[0060]

[0061] According to the total molar amount of the CO2 and the solubility of H2O in CO2 under the set temperature and pressure conditions Calculate the saturated molar amount of H2O in CO2 Wherein,

[0062] Based on the saturated molar amount of H2O in CO2 Obtain the saturated mass of H2O in CO2 Wherein,

[0063] The density of CO2 in the corrosion simulation experiment system of the present invention is related to temperature and pressure. Therefore, the density of CO2 under the set temperature and pressure conditions is obtained by looking up the table Among them, the set temperature and pressure are the temperature and pressure obtained according to the on-site working conditions during the actual pipeline transportation of CO2. For example, during the actual pipeline transportation of CO2, the on-site working condition temperature is 50 °C and the CO2 pressure is 10 MPa. Therefore, the temperature in the corrosion simulation experiment is set to 50 °C, and the CO2 pressure is set to 10 MPa. At this temperature and pressure, the density of CO2 is obtained by looking up the table. is 394 kg / m 3 .

[0064] It should also be noted that in the present invention, the density of CO2 is not calculated using the ideal gas state equation ρ = PM / RT. When the state of CO2 in the corrosion simulation experiment system of the present invention is in the supercritical state or liquid state, the density of CO2 cannot be obtained using the ideal gas state equation. When the state of CO2 in the corrosion simulation experiment system of the present invention is in the gaseous state, the density of CO2 cannot be obtained using the ideal gas state equation. Since CO2 is a gas with a high boiling point and prone to phase change, using the ideal gas state equation will result in relatively larger calculation errors.

[0065] The solubility in the corrosion simulation experiment system of the present invention is related to temperature and pressure. Therefore, the solubility of H2O in CO2 under the set temperature and pressure conditions is obtained. Among them, the solubility of H2O in CO2 under the set temperature and pressure conditions is the percentage of the single saturated molar amount (the molar amount of H2O saturated in CO2 ) in the total molar amount (the total molar amount of H2O saturated in CO2 is the total molar amount ); among them, in ×10 6 is for unit conversion, converting the unit from mol to mol ppm (ppm is one part per million in unit conversion, that is, 10 6 ).

[0066] In this embodiment, the volume fraction (water content) in the corrosion simulation experiment system provided by the present invention is related to temperature and pressure. For the same added amount (mass) of water, its volume fraction (water content) is different at different temperatures and pressures. Therefore, in order to achieve the conversion of volume fraction - mass, based on the set temperature and pressure, the present invention can calculate the water addition amount of CO2 at different temperatures and pressures: first, based on the set temperature and pressure, calculate the mass of water saturated in CO2 at the set temperature and pressure so as to use the above to obtain the saturated volume fraction of H2O in CO2 and then use the above And the above The water addition amount is obtained to convert the volume fraction of water in the corrosion simulation experimental system provided by the present invention into mass.

[0067] In some embodiments, the saturated volume fraction of H2O in CO2 is calculated as follows:

[0068] Based on the saturated mass of H2O in CO2 The total mass of CO2 The saturated mass fraction of H2O in CO2 is calculated. Wherein,

[0069] Based on the obtained saturated mass fraction of H2O in CO2 The saturated volume fraction of H2O in CO2 is obtained. Wherein,

[0070] In this embodiment, the saturated mass of H2O in CO2 is based on the above-mentioned saturated molar amount of H2O in CO2 obtained; the total mass of CO2 is determined according to the above-mentioned density of CO2 and the reaction volume of the corrosion simulation experimental system. is determined.

[0071] The saturated mass fraction of H2O in CO2 is the percentage of a single saturated mass (the saturated mass of H2O in CO2 ) in the total mass (the total mass of the saturated mass of H2O in CO2 ); wherein, in ×10 in is for unit conversion to convert the mass unit to ppm 6 (ppm w (ppm w represents one millionth of mass).

[0072] In, 2.44 is a conversion coefficient only applicable to the conversion between the volume fraction and mass fraction of H2O.

[0073] In some embodiments, under the set temperature and pressure conditions, the CO2 in the CO2 transportation environment corrosion simulation experiment is in a gaseous, liquid or supercritical state.

[0074] According to the different phases of CO2 transportation, its pipeline transportation process can be divided into three types: gaseous, liquid, and supercritical state. Among them, transporting supercritical CO2 through pipelines to target locations such as oil and gas fields or underground empty layers is currently considered a more convenient and economical means of transportation. Moreover, during the process of oil drilling and production, the pressure in the well is often above dozens of megapascals, and the temperature is as high as dozens of degrees Celsius. At this time, CO2 is also in a supercritical state.

[0075] Specifically, the CO2 in the CO2 transportation environment corrosion simulation experiment of the present invention is in a gaseous, liquid, or supercritical state. Therefore, the method provided by the present invention for calculating the water addition amount in the CO2 transportation environment corrosion simulation experiment is applicable to the calculation of the water addition amount of CO2 in any one of the gaseous, liquid, and supercritical states.

[0076] Temperature and pressure determine the phase of CO2. For example, when CO2 is heated and pressurized to the supercritical state, that is, when the temperature of CO2 is greater than the critical temperature (31.4 °C) and the pressure is also greater than the critical pressure (7.38 MPa), supercritical CO2 is obtained. Among them, supercritical CO2 has the characteristics of high compressibility, high diffusivity, and low viscosity. Its solubility in water is much higher than that in the non-supercritical state. When there are other impurities such as water in the supercritical CO2 transportation pipeline, serious corrosion will occur to metal components such as pipelines and equipment. When the temperature of CO2 is lower than the critical temperature (31.4 °C) and the pressure is higher than the critical pressure (7.38 MPa), liquid CO2 is obtained.

[0077] Since the method provided by the present invention for calculating the water addition amount in the CO2 transportation environment corrosion simulation experiment is calculated based on the set temperature and pressure, that is, the saturated volume fraction of H2O in CO2 obtained under the set temperature and pressure conditions in step S2 and the saturated mass of H2O in CO2 to determine the water addition amount m in the corrosion simulation experiment system i , so the calculation method provided by the present invention has no limitation on the phase of CO2.

[0078] In some embodiments, the reaction volume of the corrosion simulation experiment system is the volume of the high-temperature and high-pressure reaction kettle.

[0079] Specifically, the device of the corrosion simulation experiment system can be a high-temperature and high-pressure reaction kettle. Therefore, the reaction volume of the corrosion simulation experiment system is the volume of the high-temperature and high-pressure reaction kettle. For example, the reaction volume of the corrosion simulation experiment system is 3L.

[0080] In some embodiments, the solubility of H2O in CO2 is the solubility of H2O in CO2 under the set temperature and pressure conditions obtained based on the CO2-H2O mutual solubility model.

[0081] Specifically, the CO2-H2O mutual solubility model is used to obtain the solubility of H2O in CO2 under the set temperature and pressure conditions. The common CO2-H2O mutual solubility model can be adopted for this model, and this CO2-H2O mutual solubility model is related to pressure and temperature. In addition, a model that can describe the phase equilibrium between CO2 and H2O can also be used to obtain the solubility of H2O in CO2 under the set temperature and pressure conditions.

[0082] In some embodiments, the solubility of H2O in CO2 under the set temperature and pressure conditions obtained based on the CO2-H2O mutual solubility model includes:

[0083] Substitute the set temperature into the calculation formula of the fugacity coefficient and the calculation formula of the standard equilibrium constant to obtain the fugacity coefficient and the standard equilibrium constant;

[0084] Substitute the calculated fugacity coefficient, the standard equilibrium constant, and the set pressure into the CO2-H2O mutual solubility model to calculate the solubility of H2O in CO2.

[0085] Specifically, substitute the set temperature and pressure, and the molar volume V of the CO2-H2O mixed fluid (obtained by solving using the RK equation of state) into the calculation formula of the fugacity coefficient to obtain the fugacity coefficient of component H2O in the CO2-H2O mixed system and the fugacity coefficient of component CO2 in the CO2-H2O mixed system Substitute the set temperature into the calculation formula of the standard equilibrium constant to obtain the standard equilibrium constant and

[0086] Substitute the obtained fugacity coefficient of component H2O in the CO2-H2O mixed system and the fugacity coefficient of component CO2 in the CO2-H2O mixed system the standard equilibrium constant and and the known average partial molar volume and the set pressure P, the set temperature T, the standard pressure P 0 (0.1 MPa), the gas constant R into the CO2-H2O mutual solubility model to obtain Y H2O and X CO2 ; where Y H2O is the solubility of H2O in CO2 under the set temperature and pressure conditions.

[0087] Among them, the average partial molar volumes of pure H2O and CO2 in different states can be obtained from relevant literature data, such as being 18.1 cm 3 ·mol -1 , being 32.6 cm 3 ·mol -1 , (l) being 32.6 cm 3 ·mol -1 .

[0088] In some embodiments, the calculation formula for the fugacity coefficient is:

[0089]

[0090] Among them, is the fugacity coefficient of component i or component j in the CO2-H2O mixed system; V is the molar volume of the CO2-H2O mixed fluid; b mix and a mix are the characteristic parameters of the CO2-H2O mixed fluid, b i / j is the characteristic parameter of the component i or the component j, a ij is the gravitational parameter between the component i and the component j; x i / j is the mole fraction of the component i or the component j in the CO2 phase; R is the gas constant; T is the set temperature; P is the set pressure; the j is CO2, and the i is H2O.

[0091] In some embodiments, the calculation formula for the standard equilibrium constant is:

[0092]

[0093] Among them, is the equilibrium constant of component i or component j in the CO2-H2O mixed fluid under the standard pressure (0.1 MPa); T is the set temperature; A, B, C, D are regression coefficients; the j is CO2, and the i is H2O.

[0094] In some embodiments, the CO2-H2O mutual solubility model is:

[0095]

[0096]

[0097] Among them, Y H2O is the mole fraction of H2O in the CO2 phase; is the fugacity coefficient of H2O; is the equilibrium constant of H2O under standard pressure; X H2O is the mole fraction of H2O in the liquid phase; P is the set pressure; P 0 is the standard pressure of 0.1 MPa; is the average partial molar volume of H2O between pressures P 0 -P; R is the gas constant; T is the set temperature;

[0098] X CO2 is the mole fraction of CO2 in the liquid phase; is the fugacity coefficient of CO2; is the equilibrium constant of CO2 under standard pressure; Y H2O is the mole fraction of H2O in the CO2 phase; P is the set pressure; P 0 is the standard pressure of 0.1 MPa; is the average partial molar volume of CO2 between pressures P 0 -P; R is the gas constant; T is the set temperature.

[0099] Among them, the RK equation of state is:

[0100]

[0101]

[0102]

[0103] The mixing rule adopted by the above RK equation of state is as follows:

[0104]

[0105]

[0106]

[0107] Among them, in the above RK equation of state, P is the set pressure; R is the gas constant; T is the set temperature; V is the molar volume of the gas under pressure P and temperature T; a and b are characteristic parameters of the substance; P c represents the critical pressure; T c represents the critical temperature;

[0108] In the above mixing rule, a ij is the gravitational parameter between component i and component j; a i represents the characteristic parameter of component i, a j represents the characteristic parameter of component j; x irepresents the mole fraction of component i in the CO2 phase; x j represents the mole fraction of component j in the CO2 phase; K ij is the binary interaction parameter between components i and j; b i represents the characteristic parameter of component i; i refers to H2O and j refers to CO2.

[0109] The present invention provides an embodiment, as Figure 2 shows a flowchart of a method for calculating the water addition amount in a corrosion simulation experiment for a CO2 transportation environment:

[0110] Based on the temperature and pressure set in the corrosion simulation experiment for the CO2 transportation environment, determine the density of CO2 under these temperature and pressure conditions and the CO2-H2O mutual solubility model;

[0111] According to the density of CO2 and the reaction volume of the device in the corrosion simulation experiment system determine the total mass of CO2 required in the corrosion simulation experiment system wherein,

[0112] Based on the total mass of CO2 determine the total molar amount of CO2 in the corrosion simulation experiment system wherein,

[0113] According to the total molar amount of CO2 and the solubility of H2O in CO2 obtained based on the CO2-H2O mutual solubility model under the set temperature and pressure conditions calculate the molar amount of H2O saturated in CO2 in the corrosion simulation experiment system wherein,

[0114] Based on the molar amount of H2O saturated in CO2 obtain the mass of H2O saturated in CO2 wherein,

[0115] According to the mass of H2O saturated in CO2 and the total mass of the system (the total mass of H2O saturated in CO2 of the total mass ), calculate the mass fraction of H2O saturated in CO2 under the set temperature and pressure conditions wherein,

[0116] According to the obtained mass fraction of H2O saturated in CO2 Based on the conversion relationship between the mass fraction ω and the volume fraction , the saturated volume fraction of H2O in CO2 is obtained Among them, the conversion relationship is

[0117] Based on the target volume fraction set by the experiment The saturated volume fraction of H2O in CO2 And the saturated mass of H2O in CO2 Determine the water addition amount m in the corrosion simulation experiment system i ; Among them,

[0118] To enable those skilled in the art to better understand the present invention, the following specific examples are used to illustrate the preparation method provided by the present invention.

[0119] Example 1

[0120] Through on-site working condition testing of CO2 transported through the actual pipeline, the water content is obtained as The temperature is 50°C, the CO2 pressure is 10 MPa, and CO2 is in a supercritical state.

[0121] Set the conditions for the CO2 transportation environment corrosion simulation experiment as: temperature 50°C, CO2 pressure 10 MPa, and the target volume fraction set by the experiment Is 100 ppm v . The device used in the experiment is a high-temperature and high-pressure reactor, and the volume of this high-temperature and high-pressure reactor Is 3 L.

[0122] When the temperature is 50°C and the CO2 pressure is 10 MPa, by looking up the table, the density of CO2 under this temperature and pressure conditions is obtained Is 394 kg / m 3 ;

[0123] According to the density of CO2 kg / m 3 And the reaction volume of the device in the corrosion simulation experiment system L, determine the total mass of CO2 required in the corrosion simulation experiment system Is 1182 g; Among them,

[0124] Based on the total mass of CO2 g, determine the total molar amount of CO2 in the corrosion simulation experiment system Is 26.86 mol; Among them, Is 44 g / mol;

[0125] Based on the CO2-H2O solubility model, determine the solubility of H2O in CO2 at a temperature of 50°C and a CO2 pressure of 10 MPa. It is 4128 mol ppm; according to the total molar amount of CO2 mol, and the solubility of H2O in CO2 obtained under the set temperature and pressure conditions mol ppm, calculate the saturated molar amount of H2O in CO2 in the corrosion simulation experiment system It is 0.1109 mol; among them,

[0126]

[0127] Among them, the CO2-H2O solubility model used to determine the solubility of H2O in CO2 in this embodiment is:

[0128]

[0129]

[0130] Substitute the set temperature of 50°C into the calculation formula of the fugacity coefficient and the calculation formula of the standard equilibrium constant to obtain the fugacity coefficient and the standard equilibrium constant.

[0131] Substitute the calculated fugacity coefficient and standard equilibrium constant, and the set pressure of 10 MPa into the above CO2-H2O solubility model to calculate the solubility of H2O in CO2 as 4128 mol ppm.

[0132] Among them, the calculation formula of the fugacity coefficient is:

[0133]

[0134] The calculation formula of the standard equilibrium constant is:

[0135]

[0136] Based on the saturated molar amount of H2O in CO2 mol, obtain the saturated mass of H2O in CO2 It is 1.9961 g; among them, is 18 g / mol.

[0137] According to the saturated mass of H2O in CO2 g, and the total mass of the system (the saturated mass of H2O in CO2 1.9961 g + the total mass of CO2 1182g), the mass fraction of saturated H2O in CO2 under the set temperature and pressure conditions is calculated to be 1686 ppm w ; among them,

[0138] According to the obtained mass fraction of saturated H2O in CO2 ppm w , based on the conversion relationship between the mass fraction ω and the volume fraction , the saturated volume fraction of H2O in CO2 is obtained to be 4114 ppm v ; among them, the conversion relationship is

[0139] Based on the target volume fraction ppm v set by the experiment, the saturated volume fraction of H2O in CO2 ppm v and the saturated mass of H2O in CO2 g, the water addition amount m i for the corrosion simulation experiment system is determined to be 0.049 g; among them, It can be seen therefrom that 0.049 g of water needs to be added during the actual corrosion simulation experiment.

[0140] According to the water addition amount m i being 0.049 g, 0.049 g of water is artificially introduced into the CO2 gas to obtain a corrosion simulation experiment system with a water content of 100 ppm v , and the corrosion situation of the actual transmission pipeline with the same water content of 100 ppm v is simulated by using this corrosion simulation experiment system.

[0141] For the embodiments of the water content and mass conversion of gaseous and liquid CO2, they are the same as those in Embodiment 1, and the only differences are the substituted set temperatures and pressures are different, and correspondingly, the solubilities of H2O in CO2 under different set temperature and pressure conditions are different, which will not be repeated here.

[0142] For the method embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0143] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0144] The above has introduced in detail a method for calculating the water addition amount in the CO2 transportation environment corrosion simulation experiment provided by the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for calculating the water addition amount in the corrosion simulation experiment of CO2 transportation environment, characterized in that, The method includes: Step 1: Set the target volume fraction of H2O in CO2 in the corrosion simulation experiment system Step 2: Based on the target volume fraction The saturated volume fraction of H2O in CO2 obtained in the corrosion simulation experiment system under set temperature and pressure conditions and the mass of H2O saturated in CO2 Determine the water addition amount m in the corrosion simulation experiment system i ; where 2. The method according to claim 1, characterized in that, The mass of saturated H2O in CO2 The calculation method includes: Determine the density of CO2 under the set temperature and pressure conditions According to the density of the CO2 and the reaction volume of the corrosion simulation experimental system to determine the total mass of CO2 in the corrosion simulation experimental system wherein Based on the total mass of said CO2 Determine the total molar amount of CO2 Wherein, Based on the total molar amount of the CO2 and the solubility of H2O in CO2 under the set temperature and pressure conditions calculate the molar amount of H2O saturated in CO2 wherein Based on the molar amount of H2O saturated in CO2 obtain the mass of H2O saturated in CO2 wherein 3. The method according to claim 1, wherein The saturated volume fraction of H2O in CO2 The calculation method includes: Based on the saturated mass of H2O in CO2 The total mass of CO2 Calculate the mass fraction of saturated H2O in CO2 Wherein, According to the obtained saturated mass fraction of H2O in CO2 obtain the saturated volume fraction of H2O in CO2 wherein 4. The method according to claim 1, characterized in that, Under the set temperature and pressure conditions, the CO2 in the CO2 transport environment corrosion simulation experiment is in a gaseous, liquid, or supercritical state.

5. The method according to claim 2, wherein The reaction volume of the corrosion simulation experiment system is the volume of the high-temperature and high-pressure reactor.

6. The method according to claim 2, wherein The solubility S of H2O in CO2 H2O is the solubility of H2O in CO2 under the set temperature and pressure conditions obtained based on the CO2-H2O miscibility model.

7. The method according to claim 6, characterized in that, The solubility of H2O in CO2 under the set temperature and pressure conditions obtained based on the CO2-H2O mutual solubility model includes: Substitute the set temperature into the calculation formula of the fugacity coefficient and the calculation formula of the standard equilibrium constant to obtain the fugacity coefficient and the standard equilibrium constant; Substitute the calculated fugacity coefficient, the standard equilibrium constant, and the set pressure into the CO2-H2O mutual solubility model to calculate the solubility of H2O in CO2.

8. The method according to claim 7, characterized in that, The calculation formula of the fugacity coefficient is: Among them, is the fugacity coefficient of component i or component j in the CO2-H2O mixed system; V is the molar volume of the CO2-H2O mixed fluid; b mix and a mix are the characteristic parameters of the CO2-H2O mixed fluid, b i / j is the characteristic parameter of the component i or the component j, a ij is the gravitational parameter between the component i and the component j; x i / j is the mole fraction of the component i or the component j in the CO2 phase; R is the gas constant; T is the set temperature; P is the set pressure; j is CO2, and i is H2O.

9. The method according to claim 7, wherein The calculation formula of the standard equilibrium constant is: wherein, is the equilibrium constant of component i or component j in the CO2-H2O mixed fluid under the standard pressure (0.1 MPa); T is the set temperature; A, B, C, and D are regression coefficients; j is CO2, and i is H2O.

10. The method according to claim 7, wherein The CO2-H2O mutual solubility model is: Among them, Y H2O is the mole fraction of H2O in the CO2 phase; is the fugacity coefficient of H2O; is the equilibrium constant of H2O under standard pressure; X H2O is the mole fraction of H2O in the liquid phase; P is the set pressure; P 0 is the standard pressure of 0.1 MPa; is the average partial molar volume of H2O between pressures P 0 -P; R is the gas constant; T is the set temperature; X CO2 is the mole fraction of CO2 in the liquid phase; is the fugacity coefficient of CO2; is the equilibrium constant of CO2 under standard pressure; Y H2O is the mole fraction of H2O in the CO2 phase; P is the set pressure; P 0 is the standard pressure of 0.1 MPa; is the average partial molar volume of CO2 between pressure P 0 -P; R is the gas constant; T is the set temperature.

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