A pressure method for preparing carbon dioxide and its carbon stable isotope standard gas, and a system

Abstract

The application relates to the technical field of standard gas preparation, and discloses a pressure method for preparing carbon dioxide and carbon stable isotope standard gas, and a system thereof. The method comprises the following steps: obtaining basic parameters for gas preparation, calculating core pressure control parameters of gas preparation operation based on the mass conservation of carbon dioxide and the mass conservation of carbon stable isotopes, and sequentially completing the steps of filling decarburization atmosphere through an adsorption tube, filling high-concentration raw material gas through a quantitative ring, and supplementing the final pressure with ambient atmosphere, so as to complete the preparation of standard gas. The method can accurately control the carbon dioxide concentration and the carbon stable isotope value simultaneously, is suitable for a conventional pressure method gas preparation device, has high preparation precision and strong repeatability, and meets the high-precision standard gas use requirements of atmospheric observation, equipment calibration and the like.

Description

Technical Field

[0001] This application relates to the field of standard gas preparation technology, specifically to a pressure method and system for preparing carbon dioxide and its carbon stable isotope standard gases. Background Technology

[0002] Carbon dioxide is a core greenhouse gas, and its concentration and stable carbon isotope observations are crucial for global carbon cycle research and greenhouse gas emission control. High-precision carbon dioxide and its stable carbon isotope standard gases are essential for ensuring accurate and reliable observation data and enabling comparability of data from different stations. Existing conventional pressure-based standard gas preparation techniques mostly only control the concentration of carbon dioxide, failing to simultaneously and accurately regulate both carbon dioxide concentration and stable carbon isotope values. This makes it difficult to meet the high-precision background atmospheric observation requirements for isotope standard gas preparation. Furthermore, existing preparation methods lack adaptability to changes in environmental conditions, easily leading to unstable preparation accuracy and complex operational procedures, thus hindering the independent preparation and widespread application of standard gases at grassroots observation stations. Summary of the Invention

[0003] To solve or at least partially solve the above-mentioned technical problems, this application provides a pressure method and system for preparing carbon dioxide and its carbon stable isotope standard gases.

[0004] In a first aspect, this application provides a pressure method for preparing carbon dioxide and its carbon stable isotope standard gases, comprising the following steps: S1. Obtain basic gas mixing parameters, including the carbon dioxide concentration in the ambient atmosphere. Carbon stable isotope values Carbon dioxide concentration in high-concentration feed gas Carbon stable isotope values Target carbon dioxide concentration of the target standard gas Target carbon stable isotope value Total pressure of the target Target gas cylinder volume Quantitative ring volume ; S2. Based on the conservation of carbon dioxide mass and the conservation of carbon stable isotope mass, the target pressure for introducing carbon dioxide-free atmosphere through the carbon dioxide adsorption tube is calculated according to the aforementioned gas distribution parameters. The target partial pressure of the high-concentration raw material gas in the target gas cylinder The target pressure for introducing high-concentration feed gas into the metering ring. ; S3, based on the target pressure The target gas cylinder is filled with ambient air (with carbon dioxide removed) through a carbon dioxide adsorption tube until the pressure inside the target gas cylinder reaches the target pressure. ; S4. Based on the target pressure The high-concentration raw material gas is introduced into the metering loop, and then the high-concentration raw material gas in the metering loop is completely transferred to the target gas cylinder. S5. Fill the target gas cylinder with unadsorbed ambient air until the total pressure inside the target gas cylinder reaches the target total pressure. The standard gas preparation was completed.

[0005] Optionally, S2 specifically includes: Calculate the target carbon dioxide concentration in the ambient atmosphere after adsorption treatment. ; Based on the target carbon dioxide concentration Calculate the target pressure respectively The target voltage divider The target pressure ; Among them, the The calculation method is as follows: .

[0006] Optionally, in step S2, based on the target carbon dioxide concentration Calculate the target pressure respectively The target voltage divider The target pressure The method is as follows: ; ; .

[0007] Optionally, when the target carbon dioxide concentration With the carbon dioxide concentration Equal, and the target carbon stable isotope value Less than the carbon stable isotope value At that time, the target voltage divider The calculation method is replaced with: .

[0008] Optionally, when the target carbon dioxide concentration Greater than the carbon dioxide concentration And the target carbon stable isotope value Less than the carbon stable isotope value At that time, the target pressure The target voltage divider The target pressure The calculation method is as follows: ; ; .

[0009] Optionally, the carbon dioxide concentration Greater than the target carbon dioxide concentration The carbon stable isotope value Greater than the target carbon stable isotope value The target carbon stable isotope value Greater than the carbon stable isotope value .

[0010] Optionally, during the process of filling ambient atmosphere in S3 and S5, the method further includes: Real-time monitoring of ambient atmospheric carbon dioxide concentration and real-time carbon stable isotope value; when the real-time carbon dioxide concentration and the real-time carbon stable isotope value are compared with the carbon dioxide concentration obtained in step S1... The carbon stable isotope value When the corresponding deviation exceeds the deviation threshold, the target pressure is updated based on the real-time carbon dioxide concentration and the real-time carbon stable isotope value. The target voltage divider The target pressure .

[0011] Optionally, in step S4, after transferring the high-concentration raw material gas from the metering loop to the target gas cylinder, the method further includes: The metering ring is flushed at least once with unadsorbed ambient air, and after flushing, all the flushing gas is filled into the target gas cylinder.

[0012] Optionally, after S5, the method further includes: Perform at least one cycle of pumping and mixing operation on the gas in the target gas cylinder.

[0013] Secondly, this application also provides a pressure-based preparation system for carbon dioxide and its carbon stable isotope standard gases, comprising: The acquisition module is used to acquire basic gas distribution parameters, including the carbon dioxide concentration in the ambient atmosphere. Carbon stable isotope values Carbon dioxide concentration in high-concentration feed gas Carbon stable isotope values Target carbon dioxide concentration of the target standard gas Target carbon stable isotope value Total pressure of the target Target gas cylinder volume Quantitative ring volume ; The calculation module is used to calculate the target pressure for introducing carbon dioxide-free atmosphere through the carbon dioxide adsorption tube, based on the conservation of carbon dioxide mass and the conservation of carbon stable isotope mass, and according to the gas distribution parameters. The target partial pressure of the high-concentration raw material gas in the target gas cylinder The target pressure for introducing high-concentration feed gas into the metering ring. ; The first charging module is used to charge according to the target pressure. The target gas cylinder is filled with ambient air (with carbon dioxide removed) through a carbon dioxide adsorption tube until the pressure inside the target gas cylinder reaches the target pressure. ; The second filling module is used to fill according to the target pressure. The high-concentration raw material gas is introduced into the metering loop, and then the high-concentration raw material gas in the metering loop is completely transferred to the target gas cylinder. The third filling module is used to fill the target gas cylinder with unadsorbed ambient air until the total pressure inside the target gas cylinder reaches the target total pressure. The standard gas preparation was completed.

[0014] The method provided in this application has the following beneficial effects: The method provided in this application, by first obtaining the basic gas mixing parameters, then calculating the core pressure control parameters based on conservation laws, and then sequentially completing the step-by-step gas filling operation, can simultaneously achieve accurate dual control of carbon dioxide concentration and carbon stable isotope values, solving the problem that existing technologies can only control a single concentration index. The entire method is compatible with conventional pressure-based standard gas preparation devices, requiring no additional hardware modifications, and possesses strong operability and versatility, adapting to the standard gas preparation needs of different application scenarios. By introducing the target carbon dioxide concentration of the ambient atmosphere after adsorption treatment as an intermediate calculation variable, a general calculation formula is derived by simultaneously applying the dual conservation laws, which can match the calculation requirements of different target parameters. Furthermore, corresponding calculation optimization schemes are provided for common gas mixing scenarios such as constant concentration with negative isotope bias and increased concentration with negative isotope bias, ensuring calculation accuracy and feasibility under different scenarios. All calculation formulas are derived based on fundamental physicochemical laws, without empirical correction coefficients, and the calculation results have good repeatability and traceability. By monitoring and updating environmental parameters in real time during the gas filling process, systematic errors caused by atmospheric fluctuations can be effectively eliminated, improving the environmental adaptability of the preparation process. By performing quantitative loop flushing, metering deviations caused by dead volume residue can be eliminated, further improving the control accuracy of the raw material gas filling amount. By performing cyclic filling and mixing, the gas components in the gas cylinder can be completely homogeneous, ensuring that the parameters of the final prepared standard gas are stable and consistent. Attached Figure Description

[0015] Figure 1 A schematic flowchart of a pressure method for preparing carbon dioxide and its carbon stable isotope standard gases provided in this application embodiment; Figure 2 This is a schematic diagram of a standard gas preparation system provided in an embodiment of this application. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, specific embodiments of this application will be described in further detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely for explaining this application and not for limiting it. It should also be noted that, for ease of description, only the parts relevant to this application are shown in the drawings, not all of them. Before discussing exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe operations (or steps) as sequential processes, many of these operations can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but may also have additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0017] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0018] See Figures 1 to 2 This application provides a pressure method for preparing carbon dioxide and its carbon stable isotope standard gases, comprising the following steps: S1. Obtain basic gas mixing parameters, including the ambient atmospheric carbon dioxide concentration. Carbon stable isotope values Carbon dioxide concentration in high-concentration feed gas Carbon stable isotope values Target carbon dioxide concentration of the target standard gas Target carbon stable isotope value Total pressure of the target Target gas cylinder volume Quantitative ring volume .

[0019] In some implementations, carbon dioxide concentration Greater than the target carbon dioxide concentration Carbon stable isotope value Greater than the target carbon stable isotope value Target carbon stable isotope value Greater than the stable isotope value of carbon .

[0020] Specifically, this method is used to prepare carbon dioxide and its carbon stable isotope standard gases, and is compatible with conventional pressure-based standard gas preparation apparatus. The apparatus structure can be referenced as follows: Figure 2 The diagram shown illustrates the structure of the standard gas preparation system. The system mainly includes basic components such as an atmospheric pressure injection unit, a high-concentration gas filling unit, a target gas cylinder, a metering loop, a pressure detection component, and a carbon dioxide adsorption tube. It can complete the preparation of high-precision standard gas that meets the requirements of atmospheric background observation without the need for additional dedicated hardware.

[0021] The entire process of standard gas preparation is carried out in a constant temperature environment. During the operation, the fluctuation of ambient temperature is negligible. For a fixed amount of gas, the product of pressure and volume remains constant. Based on this principle, the amount of gas introduced can be accurately controlled by controlling the pressure value during the gas introduction process.

[0022] During the preparation of the standard gas, both the amount of carbon dioxide and the total amount of stable carbon isotopes follow the law of conservation; they are not created or destroyed during the gas mixing process. In the final standard gas, all carbon dioxide originates from two sources: one part is carbon dioxide contained in the ambient atmosphere, and the other part is carbon dioxide contained in the high-concentration feed gas. The sum of the amounts of these two sources equals the total amount of carbon dioxide in the final standard gas. Simultaneously, the total amount of stable carbon isotopes in the final standard gas is equal to the sum of the total amount of stable carbon isotopes introduced from the ambient atmosphere and the high-concentration feed gas. This principle is the core logic for achieving simultaneous and accurate control of carbon dioxide concentration and stable carbon isotope values.

[0023] This method first obtains the basic parameters of gas mixing, then calculates the core pressure control parameters required for gas mixing operation based on the basic parameters, and then completes the gas filling operation step by step according to the calculation results, finally completing the preparation of standard gas that meets the target requirements.

[0024] After obtaining the basic gas mixing parameters, each parameter needs to be accurately measured and verified to ensure that the error of all parameters is controlled within the allowable range. The basic gas mixing parameters include the ambient atmospheric carbon dioxide concentration. Carbon stable isotope values Carbon dioxide concentration in high-concentration feed gas Carbon stable isotope values Target carbon dioxide concentration of the target standard gas Target carbon stable isotope value Total pressure of the target Target gas cylinder volume Quantitative ring volume .

[0025] Carbon dioxide concentration in ambient air With carbon stable isotope value This is a fundamental parameter of the base gas used in gas mixing and needs to be measured in real time at the standard gas preparation site. The measurement process must be conducted during periods of stable wind direction, free from local emission sources, and in clear weather, avoiding adverse weather conditions such as precipitation, dust storms, and haze that could affect the stability of atmospheric composition. The measurement process must be continuous, with at least three repeated measurements. After discarding outlier data, the average of the multiple valid measurements is taken as the final ambient atmospheric carbon dioxide concentration used for gas mixing calculations. With carbon stable isotope value .

[0026] Carbon dioxide concentration in high-concentration feed gas With carbon stable isotope value This is the core gas source used to adjust the concentration and isotopic value of the target standard gas, employing pre-calibrated bottled high-pressure gas. Before the standard gas preparation begins, analytical equipment with the same precision as the ambient air being measured is required to determine the carbon dioxide concentration of the high-concentration raw material gas. With carbon stable isotope value Perform verification measurements to confirm that the deviation between the actual and nominal parameters of the feed gas is within the allowable range, thus preventing the deviation from the feed gas parameters from being carried over into the final gas mixing results. Verification measurements also require multiple repetitions, with the average value used as the final calculation parameter.

[0027] Target carbon dioxide concentration of target standard gas Target carbon stable isotope value Total pressure of the target It is preset based on the actual usage requirements of the standard gas. Target carbon dioxide concentration Target carbon stable isotope value It needs to cover the concentration and isotope variation range in actual observation applications and meet the usage requirements for observation equipment calibration. Target total pressure It needs to be compatible with the rated pressure range of the target gas cylinder, and the target total pressure is usually set. The pressure should not exceed 80% of the rated working pressure of the target gas cylinder, ensuring that the final prepared standard gas has sufficient usage and avoiding overpressure safety risks during the gas mixing process.

[0028] Target cylinder volume With quantitative loop volume These are the fixed hardware parameters of the gas distribution device. The target gas cylinder is the container that ultimately holds the standard gas, and the metering loop is a component used to accurately control the amount of high-concentration raw material gas charged. Its volume needs to be calibrated with high precision. The calibration process needs to take into account the temperature effect of the operating environment to ensure that the calibrated volume parameters are consistent with the actual operating conditions, thereby reducing the impact of volume parameter deviations on the control of the amount of high-concentration raw material gas charged.

[0029] To ensure smooth gas mixing and accurate control of target parameters, all fundamental parameters must meet fixed magnitude relationships. The carbon dioxide concentration of the high-concentration feed gas is a key factor. The target carbon dioxide concentration needs to be higher than that of the target standard gas. Only by meeting this requirement can the target carbon dioxide concentration be accurately increased by introducing a small amount of high-concentration feed gas, avoiding significant changes in the basic composition of the base gas caused by the need for large amounts of feed gas. This also allows for finer concentration gradient adjustments to suit different target concentration requirements. (The text then abruptly shifts to discussing the stable carbon isotope values ​​in the ambient atmosphere.) The target carbon stable isotope value needs to be greater than that of the target standard gas. Meanwhile, the target carbon stable isotope value of the target standard gas The carbon stable isotope value needs to be greater than that of the high-concentration feed gas. This size relationship allows the target carbon stable isotope value to fall between the isotope values ​​of the two gas sources. By adjusting the ratio of the two gas sources, the preset target isotope value can be accurately achieved, avoiding situations where the target isotope value cannot be achieved by adjusting the ratio of the two gas sources.

[0030] By accurately acquiring and confirming each basic gas mixing parameter, and ensuring that these parameters meet the corresponding boundary requirements, an accurate and reliable input basis can be provided for subsequent pressure parameter calculations. This reduces systematic errors in the gas mixing process. The final prepared standard gas has carbon dioxide concentration and carbon stable isotope values ​​that are consistent with the preset target values, and the deviation can be controlled within the range required for atmospheric background observation. This meets the standard gas usage requirements for high-precision observation equipment calibration. At the same time, the entire process is compatible with existing conventional standard gas preparation devices, requiring no hardware modification, and possesses strong operability and versatility.

[0031] S2. Based on the conservation of carbon dioxide mass and the conservation of carbon stable isotope mass, the target pressure for filling the carbon dioxide-free atmosphere through the carbon dioxide adsorption tube is calculated according to the basic gas distribution parameters. The target partial pressure of high-concentration raw material gas in the target gas cylinder The target pressure for introducing high-concentration feed gas into the metering loop. .

[0032] In some implementations, S2 specifically includes: Calculate the target carbon dioxide concentration in the ambient atmosphere after adsorption treatment. ; Based on target carbon dioxide concentration Calculate the target pressure separately Target partial pressure Target pressure ; in, The calculation method is as follows: .

[0033] In some implementations, in S2, based on the target carbon dioxide concentration Calculate the target pressure separately Target partial pressure Target pressure The method is as follows: ; ; .

[0034] In some implementations, when the target carbon dioxide concentration With carbon dioxide concentration Equal, and the target carbon stable isotope value Less than the stable isotope value of carbon At that time, the target partial pressure The calculation method is replaced with: .

[0035] In some implementations, when the target carbon dioxide concentration Greater than carbon dioxide concentration And the target carbon stable isotope value Less than the stable isotope value of carbon At that time, target pressure Target partial pressure Target pressure The calculation method is as follows: ; ; .

[0036] After obtaining and validating the basic gas mixing parameters, the next step is to calculate the core pressure parameters. This step involves setting the preset target carbon dioxide concentration. Target carbon stable isotope value The calculation results are converted into pressure values ​​that can be directly measured and accurately controlled during the gas mixing process. The accuracy of the calculation results determines whether the final prepared standard gas meets the target requirements. The entire calculation process is based on three fundamental laws: the ideal gas law under isothermal conditions, the conservation of the amount of carbon dioxide, and the conservation of the mass of stable carbon isotopes.

[0037] Before starting the calculation process, it is necessary to clarify the composition logic of the final standard gas source. In the final prepared standard gas, all carbon dioxide comes from two independent gas sources: one part is carbon dioxide contained in the ambient atmosphere, and the other part is carbon dioxide contained in the high-concentration feed gas. When it is necessary to adjust the carbon stable isotope value, a portion of the carbon dioxide in the ambient atmosphere must first be removed through a carbon dioxide adsorption tube, and then a corresponding amount of carbon dioxide must be replenished by introducing a high-concentration feed gas. By adjusting the ratio of removal to replenishment, the carbon stable isotope value can be accurately adjusted while controlling the final total carbon dioxide concentration. It is important to clarify that the carbon dioxide adsorption tube only removes carbon dioxide from the ambient atmosphere and does not change the carbon stable isotope value of the remaining ambient atmosphere. The adsorption process does not produce carbon isotope fractionation. This is the premise for the entire calculation process and the basis for ensuring the accuracy of the isotope calculation.

[0038] To simultaneously meet the dual control targets of carbon dioxide concentration and carbon stable isotope value, it is necessary to first calculate the target carbon dioxide concentration that the ambient atmosphere needs to achieve after adsorption treatment. This value is the intermediate variable connecting the two conservation laws and is the basis for all subsequent pressure parameter calculations. The calculation process requires first establishing the mathematical relationships between the two conservation laws, and then deriving the formula for calculating the intermediate concentration by solving simultaneous equations. First, the conservation relationship of carbon dioxide is established. The total amount of carbon dioxide in the final standard gas is equal to the sum of the amount of carbon dioxide brought in by the ambient atmosphere after adsorption treatment and the amount of carbon dioxide brought in by the high-concentration raw material gas. Under isothermal conditions, in a container of the same volume, the amount of gas is directly proportional to the product of pressure and concentration. Therefore, the conservation relationship of amount of gas can be transformed into a relationship between pressure, volume, and concentration. The volume of the target gas cylinder remains constant throughout the gas mixing process, so the volume term can be canceled in the relationship to simplify the calculation process.

[0039] Subsequently, a formula for the conservation of carbon stable isotope mass was established. The total amount of carbon stable isotopes in the final standard gas is equal to the sum of the total amount of carbon stable isotopes brought into the ambient atmosphere after adsorption treatment and the total amount of carbon stable isotopes brought into the high-concentration feed gas. Within the carbon dioxide concentration range covered by atmospheric background observations, the mixing process of carbon stable isotope values ​​can be directly calculated using a linear weighted method. The resulting calculation error is far below the accuracy requirements of the observation equipment and will not have a noticeable impact on the final gas mixing results. Based on this premise, the carbon stable isotope mass conservation relationship can be transformed into a correspondence between pressure, concentration, and isotope values. All parameters in the relationship are previously obtained basic parameters, retaining only the target carbon dioxide concentration in the ambient atmosphere after adsorption treatment as the only unknown variable.

[0040] By simultaneously solving the two conservation laws and eliminating other intermediate variables, the target carbon dioxide concentration in the ambient atmosphere after adsorption treatment can be derived. The calculation formula is as follows: .

[0041] This formula satisfies the requirement of dual control over concentration and isotopes. Each parameter in the formula has a clear physical meaning, and there are no meaningless correction terms. During the calculation of this parameter, it is necessary to ensure that all parameters use consistent units. Carbon stable isotope values ​​should be uniformly expressed in parts per thousand (ppm), and carbon dioxide concentrations should be uniformly expressed in units of the same order of magnitude to avoid calculation errors caused by inconsistent units. Furthermore, at least four significant figures should be retained during the calculation to reduce truncation errors.

[0042] The target carbon dioxide concentration in the ambient atmosphere after adsorption treatment was obtained. Then, the three core pressure control parameters can be calculated sequentially, namely the target pressure of filling the carbon dioxide-free atmosphere through the carbon dioxide adsorption tube. The target partial pressure of high-concentration raw gas in the target gas cylinder The target pressure for injecting high-concentration feed gas into the metering ring. The calculation of the three parameters follows the ideal gas law of state and the law of conservation of substance. The calculation process corresponds to the timing of the gas mixing operation, and the calculation results can be used to guide subsequent gas filling operations.

[0043] First, determine the target pressure. The calculation of target pressure The physical meaning of "pressure" refers to the pressure value that the target gas cylinder needs to reach after being filled with ambient air (after removing carbon dioxide) through the carbon dioxide adsorption tube. This initial filling gas does not contain carbon dioxide; its core function is to reduce the background concentration of carbon dioxide in the final ambient air by dilution, thus reserving space for concentration and isotope adjustments for subsequent filling with higher-concentration raw materials. Based on the law of conservation of carbon dioxide, it can be deduced that the amount of carbon dioxide from the ambient atmosphere in the final standard gas is equal to the sum of the target total pressure and the target pressure. The difference is multiplied by the target gas cylinder volume, and then multiplied by the original ambient atmospheric carbon dioxide concentration. The concentration of this portion of carbon dioxide needs to reach the target carbon dioxide concentration after adsorption treatment. From this, the target pressure can be derived. The calculation formula is as follows: .

[0044] In actual calculations, the validity of the calculation results needs to be verified, and the calculated target pressure... The result must be greater than or equal to 0. When the calculation result is 0, it means that it is not necessary to fill the carbon dioxide-free atmosphere through the carbon dioxide adsorption tube. In other words, it is not necessary to remove carbon dioxide from the ambient atmosphere. The preset target concentration and isotope value can be achieved directly by the ratio of ambient atmosphere to high-concentration raw material gas.

[0045] Next, we will perform the target voltage division. The calculation of the target partial pressure The physical meaning of the partial pressure is the partial pressure of the high-concentration raw material gas after it has completely diffused into the target gas cylinder, within the target total pressure. This value determines the total amount of substance in the high-concentration raw material gas and is a core parameter for simultaneously controlling the final concentration and isotope value. Based on the law of conservation of carbon dioxide, it can be deduced that the total amount of carbon dioxide in the final standard gas is equal to the sum of the amount of carbon dioxide introduced by the high-concentration raw material gas and the amount of carbon dioxide introduced by the ambient atmosphere after adsorption treatment. From this, the target partial pressure can be derived. The calculation formula is as follows: .

[0046] In actual calculations, it is necessary to ensure that the calculated target partial voltage is accurate. Greater than or equal to 0, and less than the target total pressure This avoids invalid results where the total amount of high-concentration feed gas required for charging exceeds the target total pressure. When the calculated target partial pressure... When the value is 0, it means that there is no need to introduce high-concentration raw material gas. The preset target concentration and isotope value can be achieved simply through adsorption and dilution by the ambient atmosphere.

[0047] Finally, target pressure is assessed. The calculation of target pressure The physical meaning of the pressure is the pressure value that needs to be reached within the metering loop when a high-concentration feed gas is introduced. In the standard gas preparation process, the amount of high-concentration feed gas required is extremely small. Directly introducing it into the target gas cylinder cannot achieve accurate control. Therefore, a metering loop with a fixed volume is used to accurately measure this trace amount of gas. The high-concentration feed gas introduced into the metering loop diffuses completely from the small volume space of the metering loop into the total volume space formed by the metering loop and the target gas cylinder. The final partial pressure formed within the target gas cylinder is the target partial pressure. This process follows the law of pressure-volume conservation under isothermal conditions, from which the target pressure can be derived. The calculation formula is as follows: .

[0048] In actual calculations, it is necessary to maintain consistency in the units of the metering loop volume and the target gas cylinder volume. Simultaneously, the dead volume of the metering loop and connecting pipelines must be included in the calibration value of the metering loop volume to avoid errors in the high-concentration raw material gas charging volume caused by volume parameter deviations. After the calculation is completed, the target pressure needs to be... Verification was performed to confirm that the value did not exceed the output pressure of the high-concentration raw material gas cylinder, and also did not exceed the range of the pressure gauge.

[0049] When the preset target carbon dioxide concentration With carbon dioxide concentration Equal, and the target carbon stable isotope value Less than the stable isotope value of carbon At that time, it is necessary to divide the target voltage. The calculation formula needs to be adjusted accordingly. This gas mixing scenario has corresponding usage requirements in practical applications. During atmospheric background observation, it is often necessary to prepare standard gases with the same concentration as the ambient atmosphere but different carbon stable isotope values ​​for zero-point and span calibration of isotope analysis equipment. This is to eliminate the interference of concentration changes on isotope measurement results and improve the accuracy of observation data. The core requirement of this scenario is that the total carbon dioxide concentration of the final standard gas is consistent with that of the original ambient atmosphere. Therefore, the amount of carbon dioxide removed by the carbon dioxide adsorption tube needs to be equal to the amount of carbon dioxide carried in the high-concentration raw material gas, so that the total concentration does not change and only the carbon stable isotope value is adjusted.

[0050] Based on this core requirement, the target pressure divider The calculation formula needs to be replaced accordingly. The specific form of the replaced formula is as follows: .

[0051] The calculation process remains unchanged in this scenario. First, the target carbon dioxide concentration in the ambient atmosphere after adsorption treatment is calculated using the general formula. Then calculate the target pressure. The target partial pressure is then calculated using the replaced formula. Finally, the target pressure is calculated. In the actual calculation process, it is necessary to adjust the calculated target pressure. pressure division with target A corresponding verification is performed to ensure that the two meet a specific ratio, thereby making the amount of carbon dioxide removed equal to the amount of carbon dioxide replenished, and avoiding deviations in the final standard gas concentration. After all parameters are calculated, the calculation results can be substituted into two conservation formulas for reverse verification to confirm that the deviation of the calculated final concentration from the isotope value and the preset target value is within the allowable range.

[0052] When the preset target carbon dioxide concentration Greater than carbon dioxide concentration And the target carbon stable isotope value Less than the stable isotope value of carbon In this scenario, parameter calculations can be completed using a general calculation process and formula. This is the most common and routine scenario in standard gas preparation, covering the full range of calibration needs from background atmospheric concentrations to higher emission source concentrations. It is applicable to most standard gas preparation scenarios in atmospheric observation, emission source monitoring, and laboratory analysis. The calculation formulas for the three core pressure parameters in this scenario are consistent with the general calculation formulas, and are as follows: ; ; .

[0053] In this scenario, the calculation process requires a focus on validating the parameters to ensure the calculated target pressure. Target partial pressure Target pressure All are non-negative numbers, and the target voltage is... No more than the target total pressure When the calculated target pressure When the value is 0, it means that it is not necessary to remove carbon dioxide from the ambient atmosphere. The target concentration and isotope value can be achieved directly by adjusting the ratio of ambient atmosphere to high-concentration feed gas. In this case, the adsorption tube filling step can be skipped, and the operation of filling with high-concentration feed gas can be directly initiated. After all parameters are calculated, a reverse verification is performed. All calculated parameters are substituted into the formulas for the conservation of carbon dioxide and the conservation of carbon stable isotope mass to calculate the final concentration and isotope value. After confirming that the deviation from the preset target value meets the accuracy requirements, the subsequent filling operation can proceed.

[0054] The above calculation method covers different gas mixing scenarios and can adapt to different standard gas usage needs. The calculation process can be automated through programming, reducing human error caused by manual calculation, further improving gas mixing efficiency and the reliability of results. It can also reduce the professional ability requirements of operators, making it easier to promote and use at grassroots observation stations.

[0055] S3, based on target pressure The target gas cylinder is filled with ambient air that has been de-carbonized through the carbon dioxide adsorption tube until the pressure inside the target gas cylinder reaches the target pressure. .

[0056] In some embodiments, the method further includes, during the process of filling ambient atmosphere in S3: Real-time monitoring of ambient atmospheric carbon dioxide concentration and real-time carbon stable isotope values; when the real-time carbon dioxide concentration and real-time carbon stable isotope values ​​are compared with the carbon dioxide concentration obtained from S1... Carbon stable isotope values When the corresponding deviation exceeds the deviation threshold, the target pressure is updated based on the real-time carbon dioxide concentration and the real-time carbon stable isotope value. Target partial pressure Target pressure .

[0057] After completing the calculation and reverse verification of the core pressure parameters, the next step is to fill the target gas cylinder with ambient atmosphere to remove carbon dioxide through the carbon dioxide adsorption tube. The purpose of this step is to accurately control the background amount of carbon dioxide in the target gas cylinder.

[0058] Before starting the operation, a leak test of the entire filling pipeline must be performed, all unnecessary valves closed, and the pipeline path switched so that ambient air passes through the carbon dioxide adsorption tube before entering the target gas cylinder. This ensures that all gas entering the target cylinder is treated by the carbon dioxide adsorption tube, preventing unadsorbed ambient air from directly entering the target cylinder and causing background concentration deviations. Simultaneously, it must be confirmed that the carbon dioxide adsorption tube is in effective working condition, that the adsorbent inside has undergone proper activation treatment, and that it can completely adsorb carbon dioxide from the ambient air without affecting other basic components of the ambient air. This ensures that the basic composition of the treated background gas remains consistent with the original ambient air, without introducing additional interfering impurities.

[0059] Next, open the corresponding air inlet valve and start the ambient atmosphere filling equipment to fill the target gas cylinder with gas treated by the carbon dioxide adsorption tube at a stable, low flow rate. During the filling process, continuously monitor the real-time pressure inside the target gas cylinder. The pressure monitoring equipment must be calibrated by a legally recognized metrology institution. The gas flow rate needs to be controlled during filling to avoid significant temperature fluctuations inside the target gas cylinder due to excessive flow, which could affect the accuracy of the pressure reading and cause systematic deviations in the gas filling volume. When the pressure inside the target gas cylinder approaches the calculated target pressure... At this point, it is necessary to further reduce the filling gas flow rate and use fine-tuning to control the filling volume to avoid the pressure exceeding the target value, so that the final pressure inside the gas cylinder accurately reaches the target pressure. Once the target pressure is reached, immediately close the intake valve.

[0060] During the inflation process, continuous real-time monitoring of the ambient atmosphere entering the system is required. This includes uninterrupted measurement of real-time carbon dioxide concentration and real-time carbon stable isotope values. The analytical equipment used for monitoring must be consistent with the equipment used in the initial parameter acquisition phase to ensure the comparability and accuracy of the measurement data. Monitoring is conducted concurrently with the inflation operation. A reasonable deviation threshold is pre-set, matching the target accuracy requirements of the final standard gas. If the deviation between the real-time carbon dioxide concentration and real-time carbon stable isotope values ​​obtained from the real-time monitoring and the corresponding baseline parameters acquired earlier exceeds the preset deviation threshold, the inflation operation is immediately paused. Based on the latest parameters obtained from the real-time monitoring, the core pressure parameters are recalculated, and the target pressure is updated. Target partial pressure Target pressure After updating the parameters and performing reverse verification, the target pressure is then determined according to the updated values. Continue with the inflation process.

[0061] This real-time monitoring and dynamic parameter updating method effectively eliminates systematic errors caused by fluctuations in ambient atmospheric composition during the inflation process. It also prevents deviations in the base gas parameters caused by sudden events such as local emission interference and wind direction changes from being transmitted to the final gas mixing result. This further improves the accuracy and stability of standard gas preparation. Even when there are slight fluctuations in ambient atmospheric conditions, the final prepared standard gas can still meet the preset target requirements, significantly reducing the interference of environmental factors on the gas mixing result and improving the success rate of gas mixing operations.

[0062] S4. Based on target pressure High-concentration feed gas is introduced into the metering loop, and then the high-concentration feed gas in the metering loop is completely transferred to the target gas cylinder.

[0063] In some embodiments, after transferring the high-concentration feed gas in the metering loop to the target gas cylinder in step S4, the method further includes: The metering ring is flushed at least once with unadsorbed ambient air. After flushing, all the flushing gas is filled into the target gas cylinder.

[0064] After completing the adsorption tube filling operation and confirming that the pressure inside the target gas cylinder is stable, the quantitative filling step of high-concentration raw material gas can be carried out. The purpose of this step is to achieve accurate measurement and transfer of trace amounts of high-concentration raw material gas through a fixed-volume quantitative loop.

[0065] Before starting the operation, the pipeline path must be switched and the airtightness checked. The inlet valve of the target gas cylinder must be closed, and the connection between the target gas cylinder and the atmospheric pressure unit must be disconnected. The target gas cylinder must then be reliably connected to the high-concentration gas filling unit and the metering loop, ensuring no leaks at any connection point. Next, the vacuum pump should be turned on to evacuate the metering loop and its corresponding connecting pipeline. The evacuation process should continue until the pressure inside the pipeline is below the preset vacuum threshold, ensuring no residual gas remains in the metering loop and pipeline. This prevents residual ambient air or other impurities from diluting the high-concentration raw material gas, which could lead to deviations in the effective gas volume being filled. After evacuation is complete, the valve corresponding to the vacuum pump should be closed, confirming that the metering loop is in a sealed vacuum state.

[0066] Then, the pressure reducing valve and corresponding inlet valve of the high-concentration raw material gas cylinder are slowly opened, and the high-concentration raw material gas is introduced into the metering loop at an extremely low flow rate. During the filling process, the real-time pressure within the metering loop is continuously monitored. The pressure monitoring equipment uses a high-precision pressure gauge matched to the previous calculation stage to ensure the accuracy of the pressure readings. When the pressure within the metering loop approaches the calculated target pressure... At this point, the inflation gas flow rate is further reduced, and the intake air volume is controlled by a series of fine adjustments to prevent the pressure from exceeding the target value, until the pressure in the metering loop stabilizes at the target pressure. Then immediately close the inlet valve of the high-concentration raw material gas, keep the metering ring sealed and stand still for a period of time, so that the gas pressure and temperature inside the ring can stabilize and eliminate the pressure fluctuation caused by the charging gas flow rate.

[0067] After settling, slowly open the valve of the target gas cylinder to allow the high-concentration feed gas in the metering loop to completely diffuse into the target gas cylinder. Allow sufficient settling time during the diffusion process to ensure complete pressure equilibrium between the metering loop and the target gas cylinder, maximizing the transfer of the high-concentration feed gas from the loop into the target gas cylinder. Once pressure equilibrium is achieved, close the valve of the target gas cylinder before proceeding with subsequent pipeline operations to prevent backflow of gas from the target gas cylinder.

[0068] To completely eliminate metering errors caused by the high concentration of raw material gas remaining in the dead volume of the metering loop and connecting pipeline, a flushing operation can be performed on the metering loop after the main gas transfer operation. The flushing operation uses unadsorbed ambient air as the flushing gas. The pipeline path is switched, and a certain amount of unadsorbed ambient air is introduced into the metering loop. After flushing, the metering loop is sealed and left to stand, allowing the flushing gas to fully mix with the high concentration of raw material gas remaining in the loop. Then, the valve of the target gas cylinder is reopened, completely filling the target gas cylinder with the entire flushing mixture from the metering loop. Depending on the gas mixing accuracy requirements, the flushing operation can be repeated at least once, with the same procedure for each flush, and all gas after each flush must be completely filled into the target gas cylinder.

[0069] Throughout the process, it is necessary to maintain a stable ambient temperature and avoid direct sunlight or localized temperature changes that could affect the gas pressure in the metering loop and target gas cylinder. Simultaneously, all valve operations must be slow and smooth to prevent pressure reading deviations caused by drastic airflow fluctuations. Accurate metering through the metering loop and subsequent rinsing effectively eliminates systematic errors caused by dead volume residue, improving the consistency between the actual total amount of high-concentration raw material gas charged and the calculated value. This prevents deviations in the final concentration and isotope values ​​due to variations in the amount of raw material gas charged, further enhancing the accuracy and repeatability of standard gas preparation.

[0070] S5. Fill the target gas cylinder with unadsorbed ambient air until the total pressure inside the target gas cylinder reaches the target total pressure. The standard gas preparation was completed.

[0071] In some embodiments, the method further includes, during the process of filling ambient atmosphere in S5: Real-time monitoring of ambient atmospheric carbon dioxide concentration and real-time carbon stable isotope values; when the real-time carbon dioxide concentration and real-time carbon stable isotope values ​​are compared with the carbon dioxide concentration obtained from S1... Carbon stable isotope values When the corresponding deviation exceeds the deviation threshold, the target pressure is updated based on the real-time carbon dioxide concentration and the real-time carbon stable isotope value. Target partial pressure Target pressure .

[0072] In some implementations, after S5, the following is also included: Perform at least one cycle of pumping and mixing operation on the gas in the target gas cylinder.

[0073] After completing the filling and quantitative ring flushing of the high-concentration raw material gas, the final pressure replenishment and gas mixing steps can be carried out. The purpose of this step is to replenish the total pressure in the target gas cylinder to the preset target total pressure, and at the same time, to make the gas in the gas cylinder uniformly mixed, so that the carbon dioxide concentration and carbon stable isotope value of each part of the final prepared standard gas are consistent.

[0074] Before starting the operation, switch the pipeline route and reliably reconnect the target gas cylinder to the atmospheric pressure unit. Perform a second airtightness check on the reconnected pipeline to ensure there are no leaks at all valves and connections, preventing pressure deviations caused by gas leaks during the filling process. After confirmation, open the corresponding inlet valve and fill the target gas cylinder with unadsorbed ambient air at a stable, medium flow rate. Continuously monitor the real-time pressure inside the target gas cylinder during the filling process to ensure the real-time accuracy of the pressure readings. When the pressure inside the gas cylinder approaches the preset target total pressure... Gradually reduce the inflation flow rate, using a step-by-step fine-tuning method to control the air intake, avoiding excessive pressure exceeding the target value due to excessive flow rate, until the pressure inside the cylinder stabilizes at the target total pressure. Then immediately close the inlet valve and the target gas cylinder valve to complete the basic operation of final pressure replenishment.

[0075] During the process of filling the ambient atmosphere, the real-time carbon dioxide concentration and carbon stable isotope value of the ambient atmosphere can be monitored. When the deviation between the monitored value and the previously obtained basic parameters exceeds the preset threshold, the filling operation is immediately suspended, and the corresponding pressure parameters are updated based on the real-time monitoring value to ensure that the parameters of the filled gas are consistent with the calculation basis and to eliminate systematic errors caused by fluctuations in the ambient atmosphere.

[0076] After the final pressure replenishment operation is completed, a cyclic filling and mixing operation needs to be performed on the gas in the target gas cylinder. Different component gases introduced statically have density differences. The density of high-concentration raw material gas differs from that of the ambient atmosphere. Natural diffusion alone requires an extremely long settling time to achieve complete mixing, easily leading to gas stratification within the cylinder. This results in deviations in the sampling and testing results from different locations, failing to accurately reflect the true parameters of the standard gas. The cyclic filling and mixing operation effectively breaks up the gas stratification, significantly shortens the gas mixing time, and ensures the homogeneity of the gas components.

[0077] During the cyclic filling and mixing operation, the valve pathway is switched to form a complete circulating gas path. The cyclic filling device is then activated, smoothly extracting gas from one end of the target gas cylinder and refilling it from the other end, creating a continuous gas circulation. The flow rate during cyclic filling needs to be controlled to avoid excessively high flow rates that could cause drastic pressure fluctuations within the cylinder, ensuring thorough mixing of gas components of different densities. Depending on the volume of the target gas cylinder and the required gas mixing accuracy, the cyclic filling and mixing operation needs to be performed at least once. For large-volume target gas cylinders, the number of cyclic filling cycles can be increased appropriately.

[0078] After the cyclic filling and mixing operation is completed, close the valve of the target gas cylinder, disconnect the pipeline connection, and place the gas cylinder horizontally to further stabilize the gas inside. The cyclic filling and mixing operation effectively eliminates detection errors caused by gas stratification, ensuring that subsequent sampling and testing results accurately reflect the overall parameters of the standard gas and maintain good consistency and stability across different stages of the standard gas's lifespan.

[0079] This completes the entire preparation process for carbon dioxide and its carbon stable isotope standard gases. The prepared standard gases can accurately match the preset target parameters, meeting the needs of various application scenarios such as atmospheric background observation, analytical equipment calibration, and high-precision laboratory analysis.

[0080] This application also provides a pressure-based preparation system for carbon dioxide and its carbon stable isotope standard gases, comprising: The acquisition module is used to acquire basic gas distribution parameters, including the carbon dioxide concentration in the ambient atmosphere. Carbon stable isotope values Carbon dioxide concentration in high-concentration feed gas Carbon stable isotope values Target carbon dioxide concentration of the target standard gas Target carbon stable isotope value Total pressure of the target Target gas cylinder volume Quantitative ring volume ; The calculation module, based on the conservation of carbon dioxide mass and the conservation of carbon stable isotope mass, calculates the target pressure for introducing carbon dioxide-free atmosphere through the carbon dioxide adsorption tube, according to the basic gas distribution parameters. The target partial pressure of high-concentration raw material gas in the target gas cylinder The target pressure for introducing high-concentration feed gas into the metering loop. ; The first charging module is used to charge according to the target pressure. The target gas cylinder is filled with ambient air that has been de-carbonized through the carbon dioxide adsorption tube until the pressure inside the target gas cylinder reaches the target pressure. ; The second filling module is used to fill according to the target pressure. High-concentration raw material gas is introduced into the metering loop, and then the high-concentration raw material gas in the metering loop is completely transferred to the target gas cylinder. The third filling module is used to fill the target gas cylinder with unadsorbed ambient air until the total pressure inside the target gas cylinder reaches the target total pressure. The standard gas preparation was completed.

[0081] The system provided in this application has the same technical features as the method embodiments described above, and therefore can achieve the same technical effects, which will not be repeated here.

[0082] The above description is merely a preferred embodiment and the technical principles employed in this application. This application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions that can be made by those skilled in the art will not depart from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application.

Claims

1. A pressure method for preparing carbon dioxide and its carbon stable isotope standard gases, characterized in that, Includes the following steps: S1. Obtain basic gas mixing parameters, including the carbon dioxide concentration in the ambient atmosphere. Carbon stable isotope values Carbon dioxide concentration in high-concentration feed gas Carbon stable isotope values Target carbon dioxide concentration of the target standard gas Target carbon stable isotope value Total pressure of the target Target gas cylinder volume Quantitative ring volume ; S2. Based on the conservation of carbon dioxide mass and the conservation of carbon stable isotope mass, the target pressure for introducing carbon dioxide-free atmosphere through the carbon dioxide adsorption tube is calculated according to the aforementioned gas distribution parameters. The target partial pressure of the high-concentration raw material gas in the target gas cylinder The target pressure for introducing high-concentration feed gas into the metering ring. ; S3, based on the target pressure The target gas cylinder is filled with ambient air (with carbon dioxide removed) through a carbon dioxide adsorption tube until the pressure inside the target gas cylinder reaches the target pressure. ; S4. Based on the target pressure The high-concentration raw material gas is introduced into the metering loop, and then the high-concentration raw material gas in the metering loop is completely transferred to the target gas cylinder. S5. Fill the target gas cylinder with unadsorbed ambient air until the total pressure inside the target gas cylinder reaches the target total pressure. Complete the preparation of standard gases; S2 specifically includes: Calculate the target carbon dioxide concentration in the ambient atmosphere after adsorption treatment. ; Based on the target carbon dioxide concentration Calculate the target pressure respectively The target voltage divider The target pressure ; Among them, the The calculation method is as follows: 。 2. The method according to claim 1, characterized in that, In step S2, based on the target carbon dioxide concentration Calculate the target pressure respectively The target voltage divider The target pressure The method is as follows: ； ； 。 3. The method according to claim 2, characterized in that, When the target carbon dioxide concentration With the carbon dioxide concentration Equal, and the target carbon stable isotope value Less than the carbon stable isotope value At that time, the target voltage divider The calculation method is replaced with: 。 4. The method according to claim 2, characterized in that, When the target carbon dioxide concentration Greater than the carbon dioxide concentration And the target carbon stable isotope value Less than the carbon stable isotope value At that time, the target pressure The target voltage divider The target pressure The calculation method is as follows: ； ； 。 5. The preparation method according to claim 1, characterized in that, The carbon dioxide concentration Greater than the target carbon dioxide concentration The carbon stable isotope value Greater than the target carbon stable isotope value The target carbon stable isotope value Greater than the carbon stable isotope value .

6. The method according to claim 1, characterized in that, During the process of filling ambient atmosphere in S3 and S5, the method further includes: Real-time monitoring of ambient atmospheric carbon dioxide concentration and real-time carbon stable isotope value; when the real-time carbon dioxide concentration and the real-time carbon stable isotope value are compared with the carbon dioxide concentration obtained in step S1... The carbon stable isotope value When the corresponding deviation exceeds the deviation threshold, the target pressure is updated based on the real-time carbon dioxide concentration and the real-time carbon stable isotope value. The target voltage divider The target pressure .

7. The method according to claim 1, characterized in that, In step S4, after transferring the high-concentration raw material gas from the metering loop to the target gas cylinder, the method further includes: The metering ring is flushed at least once with unadsorbed ambient air, and after flushing, all the flushing gas is filled into the target gas cylinder.

8. The method according to claim 1, characterized in that, Following S5, it also includes: Perform at least one cycle of pumping and mixing operation on the gas in the target gas cylinder.

9. A pressure-based preparation system for carbon dioxide and its carbon stable isotope standard gases, characterized in that, include: The acquisition module is used to acquire basic gas distribution parameters, including the carbon dioxide concentration in the ambient atmosphere. Carbon stable isotope values Carbon dioxide concentration in high-concentration feed gas Carbon stable isotope values Target carbon dioxide concentration of the target standard gas Target carbon stable isotope value Total pressure of the target Target gas cylinder volume Quantitative ring volume ; The calculation module is used to calculate the target pressure for introducing carbon dioxide-free atmosphere through the carbon dioxide adsorption tube, based on the conservation of carbon dioxide mass and the conservation of carbon stable isotope mass, and according to the gas distribution parameters. The target partial pressure of the high-concentration raw material gas in the target gas cylinder The target pressure for introducing high-concentration feed gas into the metering ring. ; The first charging module is used to charge according to the target pressure. The target gas cylinder is filled with ambient air (with carbon dioxide removed) through a carbon dioxide adsorption tube until the pressure inside the target gas cylinder reaches the target pressure. ; The second filling module is used to fill according to the target pressure. The high-concentration raw material gas is introduced into the metering loop, and then the high-concentration raw material gas in the metering loop is completely transferred to the target gas cylinder. The third filling module is used to fill the target gas cylinder with unadsorbed ambient air until the total pressure inside the target gas cylinder reaches the target total pressure. Complete the preparation of standard gases; The computing module is specifically configured to: Calculate the target carbon dioxide concentration in the ambient atmosphere after adsorption treatment. ; Based on the target carbon dioxide concentration Calculate the target pressure respectively The target voltage divider The target pressure ; Among them, the The calculation method is as follows: 。

Images