Method and system for adsorptive separation of Kr by activated carbon in TCD gas chromatography

Abstract

This application relates to the technical field of chromatographic analysis, specifically to a method and system for adsorptive separation of Kr by activated carbon for TCD gas chromatography. The method includes: comparing the difference between the first eigenvalue of the current gas at each temperature and the maximum value among the first eigenvalues of the current gas at all temperatures, and the difference between the peak area of the current gas chromatogram at each temperature and the maximum peak area, to determine the second eigenvalue; by analyzing the similarity of the chromatograms between the current gas and various gas samples at each temperature and the difference in the second eigenvalue, determining the likelihood function when the krypton ratio in the current gas is equal to the krypton ratio in various gas samples, so as to obtain the relevant krypton content for evaluating the adsorptive separation effect of activated carbon in the current gas. This application solves the interference of xenon on the separation and detection of krypton, and improves the accuracy of krypton separation and detection for TCD gas chromatography.

Description

Technical Field

[0001] This application relates to the technical field of chromatographic analysis, and specifically to a method and system for separating and adsorbing Kr with activated carbon for TCD gas chromatography. Background Art

[0002] During the normal operation of nuclear power plants, detecting the concentrations of inert gases (such as krypton, xenon, etc.) in gaseous effluents is an important part of determining their annual emissions. Although these inert gases have stable chemical properties, due to their radioactive characteristics, they may pose potential threats to human health and the environment. Long-term accumulation of radioactive substances may even contaminate the surrounding environment and disrupt the ecological balance. Therefore, detecting the concentration of inert gases is a necessary task to ensure that the emissions of nuclear power plants comply with international and national safety standards.

[0003] Among the inert gas nuclides emitted by nuclear power plants, the half-life of 85Kr is as long as 10.756 years, which is significantly higher than that of other nuclides. Accurately detecting the concentration of 85Kr and counting its emissions is crucial for dose estimation during the operation of nuclear power plants. Currently, the TCD gas chromatography method is a commonly used means for detecting inert gases in nuclear power plants, which realizes the separation and quantitative analysis of target gases through the difference in the thermal conductivity of different gases. However, this method has limitations. Among the inert gases emitted by nuclear power plants, krypton (Kr) and xenon (Xe) have similar properties and often appear in mixtures, making it difficult to effectively separate them, thereby reducing the accuracy of krypton separation and detection. Summary of the Invention

[0004] To solve the above technical problems, the purpose of this application is to provide a method and system for separating and adsorbing Kr with activated carbon for TCD gas chromatography. The specific technical solutions adopted are as follows:

[0005] In the first aspect, an embodiment of this application provides a method for separating and adsorbing Kr with activated carbon for TCD gas chromatography. The method includes the following steps:

[0006] Obtain the TCD gas chromatography and its peak areas after chromatographic separation of the current gas at preset different temperatures, and denote the TCD gas chromatography as chromatography;

[0007] By analyzing the deviation between each chromatographic data in the chromatography of the current gas at each temperature and the average level of all chromatographic data in its neighborhood, determine the first characteristic value of the current gas at each temperature; compare the difference between the first characteristic value of the current gas at each temperature and the maximum value among the first characteristic values of the current gas at all temperatures, and the difference between the peak area of the chromatography of the current gas at each temperature and the maximum value among the peak areas at all temperatures, and determine the second characteristic value of the current gas at each temperature;

[0008] Prepare a preset number of gas samples containing different proportions of krypton at each temperature. By analyzing the similarity of the chromatograms between the current gas and various gas samples at each temperature, determine the first similarity index between the current gas and various gas samples at each temperature; based on the differences in the second characteristic values between the current gas and various gas samples at each temperature, determine the second similarity index between the current gas and various gas samples at each temperature, and combine the first similarity index to determine the likelihood probability when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples at each temperature, so as to determine the likelihood function when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples.

[0009] Based on the likelihood function, obtain the relevant krypton content for evaluating the activated carbon adsorption and separation effect in the current gas.

[0010] Preferably, the method for determining the first characteristic value of the current gas at each temperature is as follows:

[0011] Calculate the square value of the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the mean value of all chromatographic data in its neighborhood, and take the mean value of all the square values of the chromatographic data in the chromatogram of the current gas as the first characteristic value of the current gas at each temperature.

[0012] Preferably, the expression of the second characteristic value of the current gas at each temperature is: ; where represents the second characteristic value of the current gas at temperature t; , respectively represent the first characteristic value of the current gas at temperature t and the peak area of the chromatogram of the current gas; , respectively represent the maximum value among the first characteristic values of the current gas at all temperatures and the maximum value among the peak areas of the chromatogram of the current gas.

[0013] Preferably, the preparation of a preset number of gas samples containing different proportions of krypton at each temperature includes:

[0014] At each temperature, prepare a gas sample with a preset value of the krypton proportion in the initial gas sample, and successively increase the krypton by a preset proportion on the basis of the preset value until a preset number of gas samples with different krypton proportions are obtained.

[0015] Preferably, the first similarity index between the current gas and various gas samples at each temperature is the normalized result of the cosine similarity of the chromatograms between the current gas and various gas samples at each temperature.

[0016] Preferably, the second similarity index between the current gas and various gas samples at each temperature is: the exponential function value with the natural constant as the base and the negative of the difference in the second eigenvalue between the current gas and various gas samples at each temperature as the independent variable.

[0017] Preferably, the likelihood probability when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples at each temperature is: the normalized value of the product of the first similarity index and the second similarity index between the current gas and various gas samples at each temperature.

[0018] Preferably, the expression of the likelihood function when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples is: ; represents the likelihood function when the krypton proportion in the current gas is equal to the krypton proportion in the th gas sample; represents the likelihood function when the krypton proportion in the current gas at temperature t is equal to the krypton proportion in the th gas sample; T represents the total number of preset different temperatures.

[0019] Preferably, the obtaining of the relevant krypton content for evaluating the activated carbon adsorption separation effect in the current gas includes:

[0020] Obtain the total volume of the current gas and the content of 85Kr in krypton. Take the proportion of krypton when the likelihood function takes the maximum value as the proportion of krypton in the current gas. Multiply the proportion of krypton by the total volume to obtain the total krypton gas volume. Divide the product of the total krypton gas volume in the current gas and the content of 85Kr in krypton by the total gas volume to obtain the concentration of 85Kr in the current gas, which is used to evaluate the activated carbon adsorption separation effect in the current gas.

[0021] In a second aspect, the embodiments of the present application further provide a system for separating Kr by activated carbon adsorption for TCD gas chromatography, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of the method for separating Kr by activated carbon adsorption for TCD gas chromatography described in any one of the above.

[0022] The present application has at least the following beneficial effects:

[0023] In this application, chromatographic analysis is carried out at different temperatures. By comparing the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the average level of all chromatographic data in its neighborhood, a first eigenvalue is constructed, which accurately reflects the fluctuation degree of chromatographic data at different temperatures, helps to identify and analyze the tiny changes of chromatographic peaks, thus reducing the detection error caused by unstable data and improving the reliability of the data. Further, by analyzing the similarity of the chromatograms between the current gas and various gas samples at each temperature and the difference of the second eigenvalue, a first similarity index and a second similarity index are respectively constructed, which improves the accuracy and reliability of the maximum likelihood estimation, and thus improves the accuracy of krypton separation detection. According to the separation characteristics of krypton and xenon at different temperatures, this application uses the maximum likelihood estimation algorithm for krypton separation detection, reduces the influence of xenon on krypton separation detection, and further improves the accuracy of krypton separation detection for TCD gas chromatography. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] To more clearly illustrate the technical solutions and advantages 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 drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is a flowchart of the steps of a method for separating and adsorbing Kr by activated carbon for TCD gas chromatography provided by an embodiment of the present application;

[0026] Figure 2 It is a framework diagram for constructing a likelihood function provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] To further elaborate on the technical means and effects adopted by the present application to achieve the intended invention purpose, the following, in combination with the drawings and preferred embodiments, details the specific implementation manners, structures, features and effects of the method and system for separating and adsorbing Kr by activated carbon for TCD gas chromatography proposed according to the present application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0029] The following specifically describes the specific solutions of the method and system for separating and adsorbing Kr by activated carbon for TCD gas chromatography provided by the present application with reference to the drawings.

[0030] Please refer to Figure 1 , which shows the step flowchart of the method for separating Kr by activated carbon adsorption in a TCD gas chromatograph provided by an embodiment of the present application. The method includes the following steps:

[0031] Step S1: Obtain the thermal conductivity detector gas chromatograph and its peak area after current gas chromatographic separation at preset different temperatures, and record the thermal conductivity detector gas chromatograph as the chromatograph.

[0032] (1) Adsorption separation process

[0033] During the normal operation of the nuclear power plant, the gaseous effluent discharged from the nuclear power plant is collected in a sampling tank, and the sampling volume of the gas in the sampling tank is obtained through a high-precision gas flowmeter.

[0034] Pre-impurity removal is an important link in the process of separating krypton. Water and carbon dioxide will freeze at low temperatures, affecting the subsequent enrichment and separation effects of krypton. In addition, carbon dioxide will also interfere with the adsorption of krypton by activated carbon, reducing the enrichment efficiency.

[0035] The pre-impurity removal unit of this embodiment uses an impurity removal tank composed of silica gel and alumina to remove moisture and carbon dioxide in the sampling tank gas, preventing blockage of pipelines due to freezing at ultra-low temperatures.

[0036] In this embodiment, the gas is sent from the pre-impurity removal unit to the enrichment unit by means of vacuum injection sampling. Compared with positive pressure injection sampling, vacuum injection sampling saves more time and does not introduce additional helium, reducing the interference of impurity gases.

[0037] When detecting the β rays emitted during the decay of 85Kr in the air through a liquid scintillation spectrometer, because its radioactive activity concentration is too low, it is necessary to enrich and separate 85Kr in the air before measurement. At the same time, the detection limit of the TCD detector is relatively high, and it is also necessary to enrich krypton in the gas.

[0038] In this embodiment, the krypton enrichment unit is composed of a primary enrichment unit and a secondary enrichment unit. Considering the advantages of simple operation, high safety, and small volume of cryogenic activated carbon adsorption, both the primary enrichment unit and the secondary enrichment unit of this embodiment use the method of cryogenic activated carbon adsorption to enrich krypton in the gas.

[0039] The adsorption temperature of the primary enrichment unit is -196 °C. The primary adsorption column adsorbs the gas sent from the pre - impurity removal unit by activated carbon. Activated carbon has a strong adsorption capacity for krypton, but also has a certain adsorption capacity for oxygen and nitrogen at low temperatures. Therefore, a low - temperature separation step is required to remove these impurities. The separation temperature of the primary enrichment unit is -100 °C. The primary adsorption column is heated to -100 °C to remove the adsorbed oxygen and nitrogen. The desorption temperature of the primary enrichment unit is 0 °C. The primary adsorption column is heated to 0 °C to desorb the adsorbed krypton, and the desorbed gas is purged to the secondary enrichment unit. The activation temperature of the primary enrichment unit is 300 °C. The primary adsorption column is heated to 300 °C under a protective atmosphere of helium to improve the adsorption performance of the activated carbon and ensure the subsequent enrichment efficiency of krypton in the gas.

[0040] In this embodiment, to improve the purity and enrichment efficiency of krypton, a secondary enrichment unit is set up to perform low - temperature adsorption on the gas. Compared with single - stage enrichment, multi - stage enrichment can more effectively remove impurity gases, reduce the total volume of gas entering the chromatographic column, and avoid the decline in the separation ability of the subsequent chromatographic column for krypton due to the too large gas treatment volume. The adsorption temperature of the secondary enrichment unit is -196 °C. The secondary adsorption column adsorbs the gas desorbed from the primary enrichment unit by activated carbon. The separation temperature of the secondary enrichment unit is -100 °C. The secondary adsorption column is heated to -100 °C to further remove the adsorbed oxygen and nitrogen. The desorption temperature of the secondary enrichment unit is 0 °C. The secondary adsorption column is heated to 0 °C to desorb the adsorbed krypton, and the desorbed gas is purged to the separation unit. The activation temperature of the secondary enrichment unit is 300 °C.

[0041] In this embodiment, both the primary adsorption column and the secondary adsorption column use activated carbon with a mesh size of 80 - 100, and the purging gas is 99.99% helium.

[0042] (2)Data acquisition

[0043] Since the properties of Kr and Xe are similar, it is difficult to effectively separate the two by activated carbon adsorption. The gas treated by the enrichment unit is still mixed with xenon. Therefore, in this embodiment, chromatographic separation is used to separate krypton and xenon.

[0044] On the one hand, the specific activity of 133Xe in the inert gas discharged from the nuclear power plant accounts for a relatively high proportion, which cannot be ignored when measuring 85Kr by a liquid scintillation spectrometer. On the other hand, there is a difference in the thermal conductivity between xenon and krypton mixed in the gas, which will introduce additional errors when separating and detecting krypton by a TCD detector, thus affecting the accuracy of calculating the content of 85Kr in the sampled gas.

[0045] Considering the difference in the boiling points of krypton and xenon, the separation of krypton and xenon is carried out at different column temperatures, and the TCD gas chromatography and its peak areas after the current gas chromatographic separation at preset different temperatures are obtained. For the sake of simplified representation, the TCD gas chromatography is denoted as chromatography. By analyzing the chromatographic information separated at different temperatures, the reliability of subsequent krypton separation detection is improved.

[0046] In this embodiment, the chromatographic separation column temperature, that is, the preset different temperatures are set as: -90°C, -100°C, -110°C, -120°C, -130°C. The implementer can also set them by combining specific situations, and this embodiment does not make special restrictions.

[0047] Step S2: By comparing the similarities and differences of the current gas chromatograms at different temperatures, the maximum likelihood estimation is used to detect the krypton content in the current gas.

[0048] The difference in the thermal conductivities of residual xenon and krypton leads to errors in the process of krypton separation detection by comparing with the standard krypton chromatogram through the TCD detector, reducing the accuracy of krypton separation detection. According to the separation characteristics of krypton and xenon at different column temperatures in this embodiment, the chromatographic data separated at 5 column temperatures are used as the comparison information for krypton separation detection, and the maximum likelihood estimation algorithm is used to separate and detect krypton in the gas sent to the separation unit, reducing the influence of mixed xenon on the krypton separation detection by the TCD detector. The specific process is as follows:

[0049] S201: By analyzing the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the average level of all chromatographic data in its neighborhood, the first eigenvalue of the current gas at each temperature is determined; the difference between the first eigenvalue of the current gas at each temperature and the maximum value among the first eigenvalues of the current gas at all temperatures, as well as the difference between the peak area of the current gas chromatogram at each temperature and the maximum value among the peak areas at all temperatures, are compared to determine the second eigenvalue of the current gas at each temperature.

[0050] In chromatographic analysis, due to the presence of xenon, the fluctuations of chromatographic data will increase. The density difference between krypton and xenon is significant, and at the same time, due to the influence of the difference in thermal conductivity, the interference of xenon will cause changes in the shape and area of chromatographic peaks, thus affecting the accuracy of krypton separation detection. Therefore, in this embodiment, by analyzing the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the average level of all chromatographic data in its neighborhood, the first eigenvalue of the current gas at each temperature is determined; the difference between the first eigenvalue of the current gas at each temperature and the maximum value among the first eigenvalues of the current gas at all temperatures, as well as the difference between the peak area of the current gas chromatogram at each temperature and the maximum value among the peak areas at all temperatures, are compared to determine the second eigenvalue of the current gas at each temperature to quantify the fluctuation degree of chromatographic data. The specific process is as follows:

[0051] (1) To reduce the influence of random noise and retain the information of neighboring chromatographic data to reflect the interference of xenon on the separation and detection of krypton, the first eigenvalue of the current gas at each temperature is determined by analyzing the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the average level of all chromatographic data within its neighborhood, specifically as follows:

[0052] A neighborhood W is divided with each chromatographic data in the chromatogram as the center, and the square value of the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the mean value of all chromatographic data within its neighborhood is calculated. The mean value of the square values of all chromatographic data in the chromatogram of the current gas is taken as the first eigenvalue of the current gas at each temperature, which is used to characterize the fluctuation degree of chromatographic data. The larger the first eigenvalue, the greater the deviation between the chromatographic data and the mean value of the chromatographic data within its neighborhood, indicating that the fluctuation degree of the chromatographic data within the local range is greater, and the greater the possibility that the chromatographic data is interfered by noise.

[0053] It should be noted that the value of the radius of the neighborhood W is set artificially. In this embodiment, the value of the radius of the neighborhood W is 1. In the actual application process, the implementer can also set it according to the specific situation, and this embodiment does not make special restrictions.

[0054] In addition, it should be understood that there are many methods to measure the deviation between data. In this embodiment, the difference between each chromatographic data in the chromatogram of the current gas at each temperature and the mean value of all chromatographic data within its neighborhood is used as the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the mean value of all chromatographic data within its neighborhood. In the actual application process, the implementer can also adopt other methods to measure the deviation between data, such as ratio, according to the specific situation. Regarding the selection of the method to measure the deviation between data, this embodiment does not make special restrictions.

[0055] (2) Further, the difference between the first eigenvalue of the current gas at each temperature and the maximum value of the first eigenvalues of the current gas at all temperatures, as well as the difference between the peak area of the chromatogram of the current gas at each temperature and the maximum peak area at all temperatures, are compared to determine the second eigenvalue of the current gas at each temperature, specifically as follows:

[0056] The presence of residual xenon will increase the interference of the TCD detector in detecting the krypton content. The greater the content of residual xenon, the greater the interference, and the greater the fluctuation characteristics of the corresponding chromatogram. Moreover, due to the additional heat conduction effect of xenon, the presence of residual xenon will not only increase the interference but also affect the peak area of the chromatogram. The larger the peak area, the greater the content of residual xenon. Therefore, by analyzing the difference between the first eigenvalue at each temperature and the maximum first eigenvalue, as well as the difference between the peak area and the maximum peak area, the second eigenvalue is determined, specifically as follows:

[0057] The second eigenvalue of the current gas at temperature t The expression is: ; In the formula, , respectively represent the first eigenvalue of the current gas at temperature t and the peak area of the chromatogram of the current gas; , respectively represent the maximum value among the first eigenvalues of the current gas at all temperatures and the maximum value among the peak areas of the chromatogram of the current gas.

[0058] It can be understood from the second eigenvalue of the current gas at each temperature that the second eigenvalue is used to characterize the fluctuation degree of the chromatogram. The greater the content of residual xenon, the greater the interference on the chromatographic data, and the greater the corresponding fluctuation degree of the chromatogram. If the ratio between the first eigenvalue of the current gas at temperature t and the maximum value among the first eigenvalues of the current gas at all temperatures is greater, it indicates that the chromatogram fluctuation is more severe and the interference received is greater. And if the ratio between the peak area of the chromatogram of the current gas at temperature t and the maximum value among the peak areas of the chromatogram of the current gas is greater, it indicates that the content of residual xenon is greater and the chromatogram is more interfered by residual xenon, and the finally obtained second eigenvalue is greater;

[0059] On the contrary, if the ratio between the first eigenvalue of the current gas at temperature t and the maximum value among the first eigenvalues of the current gas at all temperatures is smaller, it indicates that the chromatogram has no fluctuation or the fluctuation is relatively slight and the interference received is smaller. And if the ratio between the peak area of the chromatogram of the current gas at temperature t and the maximum value among the peak areas of the chromatogram of the current gas is smaller, it indicates that the content of residual xenon is smaller and the chromatogram is less interfered by residual xenon, and the finally obtained second eigenvalue is smaller, indicating that the chromatogram fluctuation degree is smaller. At this time, it shows that the purity of the separated krypton is relatively high.

[0060] S202: Prepare a preset number of gas samples containing different proportions of krypton at each temperature. By analyzing the similarity of the chromatograms between the current gas and various gas samples at each temperature, determine the first similarity index between the current gas and various gas samples at each temperature; Based on the difference in the second eigenvalue between the current gas and various gas samples at each temperature, determine the second similarity index between the current gas and various gas samples at each temperature, and combine the first similarity index to determine the likelihood probability when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples, so as to determine the likelihood function when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples.

[0061] (1) Prepare a preset number of gas samples containing different proportions of krypton at each temperature. Specifically: at each temperature, prepare the initial gas sample with the krypton proportion being a preset value, and successively increase the krypton by a preset proportion on the basis of the preset value until reaching a preset number of gas samples with different krypton proportions.

[0062] It should be noted that the values of the preset numerical value, preset ratio, and preset quantity are all artificially set. In this embodiment, the value of the preset numerical value is 70%, the value of the preset ratio is 1%, and the value of the preset numerical value is 30. The implementer can also set them according to specific circumstances by himself / herself, and this embodiment does not make special restrictions.

[0063] (2) Further, by analyzing the similarity of the chromatograms between the current gas and various gas samples at each temperature, the first similarity index between the current gas and various gas samples at each temperature is determined, specifically as follows:

[0064] The normalized result of the cosine similarity of the chromatograms between the current gas and various gas samples at each temperature is used as the first similarity index between the current gas and various gas samples at each temperature, which is used to characterize the similarity degree of the krypton concentration between the current gas and the gas sample. The larger the first similarity index, the greater the possibility that the krypton concentration values between the current gas and the gas sample are the same.

[0065] Among them, the calculation method of the cosine similarity is a well-known technology, and its specific calculation process will not be elaborated here.

[0066] (3) Further, based on the differences in the second eigenvalue between the current gas and various gas samples at each temperature, the second similarity index between the current gas and various gas samples at each temperature is determined, specifically as follows:

[0067] The exponential function value with the natural constant as the base and the opposite number of the difference in the second eigenvalue between the current gas and various gas samples at each temperature as the independent variable is used as the second similarity index between the current gas and various gas samples at each temperature, which is used to characterize the similarity degree of the krypton concentration between the current gas and the gas sample. The larger the second similarity index, the smaller the difference in the second eigenvalue between the current gas and various gas samples, that is, the greater the possibility that the krypton concentration values between the current gas and the gas sample are the same.

[0068] It should be noted that there are many methods to measure the differences between data. In this embodiment, the absolute value of the difference between the differences in the second eigenvalue between the current gas and various gas samples at each temperature is used as the difference in the second eigenvalue between the current gas and various gas samples at each temperature. In the actual application process, as other implementation manners, the implementer can also use other methods to measure the differences between data, such as the square or ratio of the differences. Regarding the selection of the method to measure the differences between data, this embodiment does not make special restrictions.

[0069] Supplementary note: The method for obtaining the second similarity index of the gas sample is the same as that for obtaining the second similarity index of the current gas, and the specific process will not be elaborated here.

[0070] (4)The second similarity index between the current gas and various gas samples at each temperature, and in combination with the first similarity index, determine the likelihood probability when the krypton ratio in the current gas is equal to the krypton ratio in various gas samples at each temperature, so as to determine the likelihood function when the krypton ratio in the current gas is equal to the krypton ratio in various gas samples, specifically:

[0071] In this embodiment, the normalized value of the product of the first similarity index and the second similarity index between the current gas and various gas samples at each temperature is used as the likelihood probability when the krypton ratio in the current gas is equal to the krypton ratio in various gas samples at each temperature.

[0072] When the krypton ratio in the current gas is equal to the krypton ratio in the th gas sample, the expression of the likelihood function is: represents the likelihood function when the krypton ratio in the current gas is equal to the krypton ratio in the th gas sample at temperature t; T represents the total number of preset different temperatures.

[0073] So far, in this embodiment, through temperature chromatography analysis and maximum likelihood estimation, the likelihood function has been obtained, which is used to detect the content of krypton in the gas. By using the separation characteristics of krypton and xenon at different temperatures, the chromatographic data fluctuations are analyzed to reduce the interference of xenon on the detection of krypton content and improve the accuracy of krypton separation detection.

[0074] Preferably, the framework diagram for constructing the likelihood function provided in this embodiment is as Figure 2 shown.

[0075] Step S3: Based on the likelihood function when the krypton ratio in the current gas is equal to the krypton ratio in various gas samples, evaluate the effect of activated carbon adsorption and separation of krypton in the current gas.

[0076] Since the boiling point of xenon is relatively high, at -130 °C, krypton is more likely to remain in the gaseous state, while xenon is more likely to condense or adsorb on the stationary phase. At the same time, the molecular weight of xenon is greater than that of krypton. At the same temperature, the diffusion rate of krypton is higher than that of xenon. At -130 °C, this difference in diffusion rate is maximized, enabling krypton to flow out of the chromatographic column faster, while xenon remains in the column, so the separation effect is the best at 5 column temperatures and the residual xenon in krypton is the least.

[0077] Therefore, in this embodiment, the krypton separated at a column temperature of -130 °C is used as a sample. Specifically, the separated krypton is mixed with a scintillation fluid to prepare a liquid scintillation sample. The specific formula of the scintillation fluid is 5 g of polyphenylene oxide (PPO) and 0.3 g of 1,4-bis-(5-phenyloxazol-2-yl)benzene (POPOP) dissolved in 1 L of toluene. The prepared liquid scintillation sample is placed in a liquid scintillation spectrometer to measure its radioactivity.

[0078] Further, a standard 85Kr sample with a known concentration is used as a reference. According to the radioactivity measured by the liquid scintillation spectrometer and combined with the data of the standard sample, the content of 85Kr in krypton is calculated as the content of 85Kr in krypton in the current gas.

[0079] Among them, the processes of the above separation, preparation of the liquid scintillation sample, measurement of radioactivity, and calculation of the content of 85Kr in krypton are all well-known technologies, and their specific principles will not be elaborated here.

[0080] Thus, the content of 85Kr in krypton in the current gas is obtained. Further, the proportion of krypton when the likelihood function obtained in step S2 takes the maximum value is used as the proportion of krypton in the current gas. The total volume of the current gas is obtained by using a TCD detector. The product of the proportion of krypton and the total volume is used as the total volume of krypton gas. The result of multiplying the total volume of krypton gas in the current gas by the content of 85Kr in krypton is divided by the total volume of the gas to obtain the concentration of 85Kr in the current gas, which is used to evaluate the adsorption and separation effect of activated carbon in the current gas.

[0081] Based on the same inventive concept as the above method, the embodiment of the present application also provides a system for adsorptive separation of Kr by activated carbon for TCD gas chromatography, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above methods for adsorptive separation of Kr by activated carbon for TCD gas chromatography.

[0082] It should be noted that the above sequence of embodiments of the present application is only for description and does not represent the superiority or inferiority of the embodiments. And the above specific embodiments of this specification have been described. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0083] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments.

[0084] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for adsorptive separation of Kr by activated carbon in TCD gas chromatography, characterized in that, The method includes the following steps: Obtain the TCD gas chromatography and its peak area after the current gas chromatographic separation at preset different temperatures, and denote the TCD gas chromatography as chromatography; Calculate the square value of the deviation between each chromatographic data in the chromatogram of the current gas at each temperature and the mean value of all chromatographic data in its neighborhood, and take the mean value of the square values of all chromatographic data in the chromatogram of the current gas as the first eigenvalue of the current gas at each temperature; compare the difference between the first eigenvalue of the current gas at each temperature and the maximum value among the first eigenvalues of the current gas at all temperatures, and the difference between the peak area of the chromatogram of the current gas at each temperature and the maximum value among the peak areas of the chromatograms at all temperatures, and determine the second eigenvalue of the current gas at each temperature. The expression of the second eigenvalue is: ; where represents the second eigenvalue of the current gas at temperature t; and represent the first eigenvalue of the current gas at temperature t and the peak area of the chromatogram of the current gas respectively; and represent the maximum value among the first eigenvalues of the current gas at all temperatures and the maximum value among the peak areas of the chromatograms of the current gas respectively; Prepare preset numbers of gas samples containing different proportions of krypton at each temperature. By analyzing the similarity of the chromatographies between the current gas and various gas samples at each temperature, determine the first similarity index between the current gas and various gas samples at each temperature; based on the differences in the second characteristic values between the current gas and various gas samples at each temperature, determine the second similarity index between the current gas and various gas samples at each temperature, and combine the first similarity index to determine the likelihood probability when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples, so as to determine the likelihood function when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples; Based on the likelihood function, obtain the relevant krypton content for evaluating the activated carbon adsorption separation effect in the current gas.

2. The method for adsorptive separation of Kr by activated carbon for TCD gas chromatography according to claim 1, wherein, The step of preparing preset numbers of gas samples containing different proportions of krypton at each temperature includes: At each temperature, prepare a gas sample with a preset value of the krypton proportion in the initial gas sample, and successively increase the krypton by a preset proportion on the basis of the preset value to obtain gas samples with different krypton proportions until reaching preset numbers of gas samples with different krypton proportions.

3. The method for adsorptive separation of Kr by activated carbon for TCD gas chromatography according to claim 1, wherein The first similarity index between the current gas and various gas samples at each temperature is the normalized result of the cosine similarity of the chromatographies between the current gas and various gas samples at each temperature.

4. The method for adsorptive separation of Kr by activated carbon for TCD gas chromatography according to claim 1, wherein The second similarity index between the current gas and various gas samples at each temperature is: the exponential function value with the natural constant as the base and the opposite of the difference in the second characteristic values between the current gas and various gas samples at each temperature as the independent variable.

5. The method for adsorptive separation of Kr by activated carbon for TCD gas chromatography according to claim 1, wherein, The likelihood probability when the krypton proportion in the current gas is equal to the krypton proportion in various gas samples at each temperature is: the normalized value of the product of the first similarity index and the second similarity index between the current gas and various gas samples at each temperature.

6. The method for separating Kr by activated carbon adsorption in a TCD gas chromatograph according to claim 1, characterized in that, The expression of the likelihood function when the krypton ratio in the current gas is equal to the krypton ratio in various gas samples is as follows: ; represents the likelihood function when the krypton ratio in the current gas is equal to the krypton ratio in the th gas sample; represents the likelihood function when the krypton ratio in the current gas at temperature t is equal to the krypton ratio in the th gas sample; T represents the total number of preset different temperatures.

7. The method for adsorptive separation of Kr by activated carbon for TCD gas chromatography according to claim 1, wherein The step of obtaining the relevant krypton content for evaluating the activated carbon adsorption separation effect in the current gas includes: Obtain the total volume of the current gas and the content of 85Kr in krypton. Take the krypton proportion when the likelihood function reaches the maximum value as the krypton proportion in the current gas, multiply the krypton proportion by the total volume as the total krypton gas volume, and divide the product of the total krypton gas volume in the current gas and the content of 85Kr in krypton by the total gas volume to obtain the concentration of 85Kr in the current gas, which is used to evaluate the activated carbon adsorption separation effect in the current gas.

8. A system for adsorptive separation of Kr by activated carbon in TCD gas chromatography, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for activated carbon adsorption separation of Kr for TCD gas chromatography according to any one of claims 1-7.

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