An experimental device and measurement method for determining the fractionation coefficient of rare gas isotopes in geothermal volatiles

Abstract

The present invention relates to the technical field of chemical analysis and detection, and particularly to an experimental device and a determination method for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components. The device includes a diffusion fractionation mechanism, and a heat preservation mechanism is arranged outside the diffusion fractionation mechanism. A chamber A and a chamber B are arranged inside the diffusion fractionation mechanism. The chamber A and the chamber B are separated by a diffusion component. One side of the chamber A is connected to an intake mechanism I, and the other side of the chamber A is connected to a sampling mechanism I. One side of the chamber B is connected to an intake mechanism II, and the other side of the chamber B is connected to a sampling mechanism II. A thermometer and a pressure gauge are respectively connected to the chamber A and the chamber B. By adopting the above experimental device and determination method for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components, the device has a simple and reasonable structure and can quickly and accurately measure the fractionation coefficient of rare gas isotopes.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical analysis and detection, and particularly to an experimental device and a determination method for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles. Background Technique

[0002] Rare gases (helium, neon, argon, krypton, xenon) are important volatiles emitted during volcanic eruptions / releases. Due to their chemical inertness, strong volatility, and significant isotope differences, they have become important means for tracing the geochemical characteristics of various reservoirs within the Earth and revealing the origin of magmas. Cross-layer migration generally couples multi-component fluids rich in CO2 or N2, and thus plays a key role in tracing the sources and evolution of other volcanic volatiles (carbon, nitrogen, sulfur, etc.). The concentration and isotopes of rare gases provide crucial geochemical information for the sources and evolution of volcanic volatiles. For example, the difference in helium isotope ratio ( 3 He / 4 He) can be used to study the contributions of different mantle reservoirs to volcanic eruptions and the nature of mantle-crust interactions. In addition, heavy rare gases (argon, krypton, xenon) are also used to explore the material cycle within the Earth and plate tectonic activities. By measuring the isotope compositions of argon and xenon emitted by volcanoes, researchers can trace the recycling process of crustal materials and the dynamic changes in plate subduction zones, and constrain the time and extent of mantle degassing to the atmosphere during geological periods. Geological decarbonization processes, water-rock-gas interactions, intracrustal microbial activities, etc. all affect the release of deep-source carbon to the atmosphere, and rare gas isotopes can provide unique insights into characterizing these processes.

[0003] However, there has been no report on the experimental device for measuring the fractionation coefficient of rare gas isotopes in the prior art. Therefore, in order to facilitate the measurement of the fractionation coefficient of rare gas isotopes, the present invention provides a simulation experimental device and a determination method for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles. Summary of the Invention

[0004] The purpose of the present invention is to provide an experimental device and a determination method for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles. The device has a simple and reasonable structure and can quickly and accurately measure the fractionation coefficient of rare gas isotopes.

[0005] To achieve the above purpose, the present invention provides an experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles, including a diffusion fractionation mechanism. A heat preservation mechanism is arranged outside the diffusion fractionation mechanism. The diffusion fractionation mechanism is provided with a chamber A and a chamber B. The chamber A and the chamber B are separated by a diffusion component. One side of the chamber A is connected to an intake mechanism I, the other side of the chamber A is connected to a sampling mechanism I, one side of the chamber B is connected to an intake mechanism II, the other side of the chamber B is connected to a sampling mechanism II. Thermometers and pressure gauges are respectively connected to the chamber A and the chamber B.

[0006] Preferably, the heat preservation mechanism includes a heat preservation sleeve and an electric heater. The heat preservation sleeve is sleeved outside the diffusion fractionation mechanism, and the electric heater is arranged inside the heat preservation sleeve and is electrically connected to the numerical control system.

[0007] Preferably, the diffusion component includes a water layer with a thickness of 2 - 3 cm. Hydrophobic porous hollow fiber membranes are symmetrically arranged on both sides of the water layer. A porous support layer is arranged on the side of the fiber membrane away from the water layer, and the porous support layer is a porous platinum sheet with a thickness of 2 mm.

[0008] Preferably, the first air intake mechanism includes a first air intake pipe and a first compressor. The first air intake pipe is used to introduce the test gas, and the first compressor is arranged on the first air intake pipe.

[0009] Preferably, the second air intake mechanism includes a second air intake pipe and a second compressor. The second air intake pipe is used to introduce the carrier gas, and the second compressor is arranged on the second air intake pipe.

[0010] Preferably, the first sampling mechanism includes a copper pipe sampling tube 1. One end of the copper pipe sampling tube 1 is communicated with chamber A through a first valve, and a second valve is arranged at the other end of the copper pipe sampling tube 1. Two sampling clips 1 arranged in parallel are arranged between the first valve and the second valve.

[0011] Preferably, the second sampling mechanism includes a copper pipe sampling tube 2. One end of the copper pipe sampling tube 2 is communicated with chamber B through a third valve, and a fourth valve is arranged at the other end of the copper pipe sampling tube 2. Two sampling clips 2 arranged in parallel are arranged between the third valve and the fourth valve.

[0012] The method for measuring the fractionation coefficient of rare gas isotopes of geothermal volatiles by the above experimental device includes the following steps:

[0013] S1 In the initial stage of the experiment, the carrier gas is introduced into the diffusion fractionation mechanism through the second air intake mechanism, and chambers A and B are flushed with the carrier gas. Samples of chambers A and B are collected through the first sampling mechanism and the second sampling mechanism respectively to measure the background value.

[0014] S2 When the experiment starts, the test gas is introduced into chamber A through the first air intake mechanism, and the carrier gas is introduced into chamber B through the second air intake mechanism. Under the condition that the pressure in chamber A is 0.3 Bar higher than that in chamber B, the test gas in chamber A is fractionated into chamber B through the diffusion component.

[0015] S3 The sample in chamber B is introduced into the quadrupole mass spectrometer through the second sampling mechanism to measure the flux of the test gas in the diffusion component and the concentration of the test gas isotope in chamber B. The sample in chamber A is introduced into the quadrupole mass spectrometer through the first sampling mechanism to measure the concentration of the test gas isotope in chamber A.

[0016] The isotope concentration measured by the quadrupole mass spectrometer in S4 is used to obtain the isotope variation curve. The dynamic change of gas diffusion is determined by the isotope variation curve, the diffusion coefficient of the test gas is determined by the dynamic change of gas diffusion, and the fractionation coefficient of the test gas isotope is determined by the diffusion coefficient of the test gas or the flux of the test gas in the diffusion component.

[0017] Preferably, before the test gas and the carrier gas are introduced in S2, they are first saturated with water vapor. The temperatures of both chamber A and chamber B are 100°C - 300°C, and the pressures are both 0 - 30 Mpa.

[0018] Preferably, in S4, when the gas flowing out of chamber B is in a steady state, the fractionation coefficient of the test gas isotope is represented by the ratio of the diffusion coefficients of the isotopes, and the calculation formula is as follows.

[0019]

[0020] Among them, is the concentration ratio of isotope i and isotope j of the test gas in chamber A, C i (0) is the concentration of isotope i of the test gas in chamber A, C j (0) is the concentration of isotope j of the test gas in chamber A;

[0021] is the flux of the test gas entering chamber B through the diffusion component, C i (L) is the concentration of isotope i of the test gas in chamber B, C j (L) is the concentration of isotope j of the test gas in chamber B;

[0022] D i is the diffusion coefficient of isotope i, D j is the diffusion coefficient of isotope j;

[0023] When the gas flowing out of chamber B is in a non-steady state, the fractionation coefficient of the test gas isotope is calculated from the non-steady gas flux of the test gas in the diffusion component. The calculation formula for the non-steady gas flux of the test gas is as follows.

[0024]

[0025] Among them, F i is the flux of the test gas diffusion in chamber B, t is the experimental time, and t = 0 represents the start of the experiment, that is, when chamber A is completely filled with the test gas;

[0026] t = L 2 / 6D i When it means that the flux F i of chamber B no longer increases, that is, the stable time point;

[0027] x = 0 or x = L. When x = 0, C i (x) represents the concentration of isotope i in chamber A. When x = L, C i (x) represents the concentration of isotope i in chamber B, and D i is the diffusion coefficient of isotope i, and L is the thickness of the diffusion component;

[0028] The derivative at the steady-state time point of the unsteady gas flow flux is the fractionation coefficient of isotope i and isotope j.

[0029] Advantages of the present invention:

[0030] Therefore, the present invention adopts the above experimental device and measurement method for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles. The device has a simple and reasonable structure and can quickly and accurately measure the fractionation coefficient of rare gas isotopes under different temperatures

[0031] (100 - 300 °C) and pressures (0 - 30 MPa) to simulate the migration process of volatiles from deep to the surface.

[0032] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0033] Figure 1 is a schematic diagram of an experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles according to the present invention;

[0034] Figure 2 is a partial schematic diagram of the diffusion component of the present invention.

[0035] Reference Signs:

[0036] 1. Diffusion fractionation mechanism; 11. Chamber A; 12. Chamber B; 2. Heat insulation mechanism; 21. Heat insulation sleeve; 22. Electric heater; 3. Diffusion component; 31. Water layer; 32. Fiber membrane; 33. Porous support layer; 4. Intake mechanism one; 41. Intake pipeline one; 42. Compressor one; 5. Sampling mechanism one; 51. Copper tube sampling tube one; 52. Valve one; 53. Valve two; 54. Sampling clamp one; 6. Intake mechanism two; 61. Intake pipeline two; 62. Compressor two; 7. Sampling mechanism two; 71. Copper tube sampling tube two; 72. Valve three; 73. Valve four; 74. Sampling clamp two; 8. Thermometer; 9. Pressure gauge. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains. The above-mentioned features mentioned in the present invention or the features mentioned in the specific examples can be combined arbitrarily. These specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0038] Embodiment 1

[0039] Please refer to Figure 1-2 , as shown in the figure, the present invention provides an experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles, including a diffusion fractionation mechanism 1. A heat preservation mechanism 2 is arranged outside the diffusion fractionation mechanism 1. The heat preservation mechanism 2 includes a heat preservation sleeve 21 and an electric heater 22. The heat preservation sleeve 21 is sleeved outside the diffusion fractionation mechanism 1. The material of the heat preservation sleeve 21 is heat preservation cotton to reduce the heat diffusion of the diffusion fractionation mechanism 1. The electric heater 22 is arranged inside the heat preservation sleeve 21, and the electric heater 22 is electrically connected to the numerical control system. The numerical control system is a temperature monitoring and control system in the prior art. The numerical control system controls the electric heater 22 to heat through the prior art to achieve the heat preservation effect of the heat preservation mechanism 2 and ensure that the temperature difference of the diffusion fractionation mechanism 1 during the whole experimental process is within ±0.5°C.

[0040] A chamber A11 and a chamber B12 are arranged inside the diffusion fractionation mechanism 1. The chamber A11 and the chamber B12 are separated by a diffusion component 3. The diffusion component 3 includes a water layer 31 with a thickness of 2 - 3 cm. Hydrophobic porous hollow fiber membranes 32 with high temperature resistance (>300°C) are symmetrically arranged on both sides of the water layer 31. A porous support layer 33 is arranged on the side of the fiber membrane 32 away from the water layer 31. The porous support layer 33 is a porous platinum sheet with a thickness of 2 mm. The porous support layer 33 is used to fix the water layer 31 to avoid the water layer 31 from having turbulence at high temperatures and ensure that the migration of rare gases is mainly transmitted in the form of diffusion.

[0041] One side of the chamber A11 is communicated with an intake mechanism 4. The intake mechanism 4 includes an intake pipeline 41 and a compressor 42. The intake pipeline 41 is used to introduce the test gas, and the compressor 42 is arranged on the intake pipeline 41. The setting of the compressor 42 ensures that the test gas entering from the intake pipeline 41 can reach the set pressure and maintain a stable pressure. The test gas is a mixture of gas CO2 and a rare gas, and the rare gas is one of He, Ne, Ar, Kr, Xe.

[0042] The other side of chamber A11 is connected to sampling mechanism 1 - 5. Sampling mechanism 1 - 5 includes a copper - tube sampling tube 1 - 51. One end of the copper - tube sampling tube 1 - 51 is connected to chamber A11 through valve 1 - 52, and the other end of the copper - tube sampling tube 1 - 51 is provided with valve 1 - 53. There are two parallel - arranged sampling clips 1 - 54 between valve 1 - 52 and valve 1 - 53. By opening valve 1 - 52, valve 1 - 53 and sampling clip 1 - 54, the sample in chamber A11 can be introduced into the quadrupole mass spectrometer through the copper - tube sampling tube 1 - 51 for measurement.

[0043] One side of chamber B12 is connected to intake mechanism 2 - 6. Intake mechanism 2 - 6 includes intake pipe 2 - 61 and compressor 2 - 62. Intake pipe 2 - 61 is used to introduce carrier gas, and compressor 2 - 62 is arranged on intake pipe 2 - 61. The setting of compressor 2 - 62 ensures that the carrier gas entering from intake pipe 2 - 61 can reach the set pressure and maintain a stable pressure. The carrier gas is pure N2 (99.999%, without rare gases).

[0044] The other side of chamber B12 is connected to sampling mechanism 2 - 7. Sampling mechanism 2 - 7 includes a copper - tube sampling tube 2 - 71. One end of the copper - tube sampling tube 2 - 71 is connected to chamber B12 through valve 2 - 72, and the other end of the copper - tube sampling tube 2 - 71 is provided with valve 2 - 73. There are two parallel - arranged sampling clips 2 - 74 between valve 2 - 72 and valve 2 - 73. By opening valve 2 - 72, valve 2 - 73 and sampling clip 2 - 74, the sample in chamber B12 can be introduced into the quadrupole mass spectrometer through the copper - tube sampling tube 2 - 71 for measurement.

[0045] When the gases in chamber A11 and chamber B12 are in a stable state, after opening valve 1 - 52, valve 1 - 53, valve 2 - 72 and valve 2 - 73, sampling clips 1 - 54 and sampling clips 2 - 74 can be used to cut off the copper - tube sampling tube 1 - 51 and the copper - tube sampling tube 2 - 71 respectively. Then the samples in chamber A11 and chamber B12 can be stored in the copper - tube sampling tube 1 - 51 and the copper - tube sampling tube 2 - 71 respectively, which can be used for subsequent isotope ratio tests. Thermometers 8 and pressure gauges 9 are also respectively connected to chamber A11 and chamber B12, facilitating the monitoring of the temperature and pressure in chamber A11 and chamber B12.

[0046] Example 2

[0047] A method for measuring the rare - gas isotope fractionation coefficient of geothermal volatiles using the experimental device provided in Example 1 includes the following steps:

[0048] S1 In the initial stage of the experiment, carrier gas is introduced into the diffusion fractionation mechanism through intake mechanism 2 - 6, and the carrier gas is used to flush chamber A and chamber B. Samples of chamber A and chamber B are collected through sampling mechanism 1 - 5 and sampling mechanism 2 - 7 respectively, and the background values are tested to show whether the chambers are pure, so as to eliminate background pollution;

[0049] At the start of Experiment S2, a test gas is introduced into Chamber A through Inlet Mechanism 1, and a carrier gas is introduced into Chamber B through Inlet Mechanism 2. Before being introduced, the test gas and the carrier gas are saturated with water vapor to avoid affecting the dryness and humidity of the fiber membrane in the diffusion module. The temperatures of both Chamber A and Chamber B are 100°C - 300°C, and the pressures are both 0 - 30 Mpa. Under the condition that the pressure in Chamber A is 0.3 Bar higher than that in Chamber B, the test gas in Chamber A is fractionated into Chamber B through the diffusion module.

[0050] In S3, the sample in Chamber B is introduced into a quadrupole mass spectrometer through Sampling Mechanism 2 to measure the flux of the test gas in the diffusion module and the concentration of the test gas isotope in Chamber B. The sample in Chamber A is introduced into the quadrupole mass spectrometer through Sampling Mechanism 1 to measure the concentration of the test gas isotope in Chamber A.

[0051] In S4, an isotope change curve is obtained from the isotope concentration measured by the quadrupole mass spectrometer. The dynamic change of gas diffusion is determined from the isotope change curve. The diffusion coefficient of the test gas is determined from the dynamic change of gas diffusion. The fractionation coefficient of the test gas isotope is determined from the diffusion coefficient of the test gas or the flux of the test gas in the diffusion module.

[0052] When the gas flowing out of Chamber B is in a steady state, the fractionation coefficient of the test gas isotope is expressed by the ratio of the diffusion coefficients of the isotopes. The calculation formula is as follows.

[0053]

[0054] Among them, is the concentration ratio of test gas isotopes i and j in Chamber A, C i (0) is the concentration of test gas isotope i in Chamber A, C j (0) is the concentration of test gas isotope j in Chamber A;

[0055] is the flux of the test gas entering Chamber B through the diffusion module, C i (L) is the concentration of test gas isotope i in Chamber B, C j (L) is the concentration of test gas isotope j in Chamber B;

[0056] D i is the diffusion coefficient of isotope i, D j is the diffusion coefficient of isotope j;

[0057] When the gas flowing out of Chamber B is in a non-steady state, the fractionation coefficient of the test gas isotope is calculated from the non-steady gas flux of the test gas in the diffusion module. The calculation formula for the non-steady gas flux of the test gas is as follows.

[0058]

[0059] Among them, F i is the flux of the test gas diffusion in chamber B, t is the experimental time, and t = 0 represents the start of the experiment, that is, when chamber A is completely filled with the test gas;

[0060] t = L 2 / 6D i When it represents that the flux F of chamber B i no longer increases, that is, the stable time point;

[0061] x = 0 or x = L. When x = 0, C i (x) represents the concentration of isotope i in chamber A. When x = L, C i (x) represents the concentration of isotope i in chamber B, and D i is the diffusion coefficient of isotope i, and L is the thickness of the diffusion component;

[0062] The derivative of the stable time point of the unsteady gas flow flux is the fractionation coefficient of isotope i and isotope j.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components, characterized in that: It includes a diffusion fractionation mechanism. There is a heat insulation mechanism outside the diffusion fractionation mechanism. Inside the diffusion fractionation mechanism, there are chamber A and chamber B. Chamber A and chamber B are separated by a diffusion component. One side of chamber A is connected to intake mechanism one, and the other side of chamber A is connected to sampling mechanism one. One side of chamber B is connected to intake mechanism two, and the other side of chamber B is connected to sampling mechanism two. A thermometer and a pressure gauge are respectively connected to chamber A and chamber B; The diffusion component includes a water layer with a thickness of 2 - 3 cm. Hydrophobic porous hollow fiber membranes are symmetrically arranged on both sides of the water layer. A porous support layer is arranged on the side of the fiber membrane away from the water layer, and the porous support layer is a porous platinum sheet with a thickness of 2 mm; The method for measuring the fractionation coefficient of rare gas isotopes of geothermal volatiles using the above experimental device includes the following steps: S1 In the initial stage of the experiment, carrier gas is introduced into the diffusion fractionation mechanism through intake mechanism two. Chamber A and chamber B are flushed with the carrier gas. Samples of chamber A and chamber B are respectively collected through sampling mechanism one and sampling mechanism two, and the background values are tested; S2 When the experiment starts, test gas is introduced into chamber A through intake mechanism one, and carrier gas is introduced into chamber B through intake mechanism two. Under the condition that the pressure in chamber A is 0.3 Bar higher than that in chamber B, the test gas in chamber A is fractionated into chamber B through the diffusion component; S3 The sample in chamber B is introduced into a quadrupole mass spectrometer through sampling mechanism two to measure the flux of the test gas in the diffusion component and the concentration of the test gas isotope in chamber B. The sample in chamber A is introduced into a quadrupole mass spectrometer through sampling mechanism one to measure the concentration of the test gas isotope in chamber A; S4 Through the isotope concentration measured by the quadrupole mass spectrometer, an isotope change curve is obtained. The dynamic change of gas diffusion is determined through the isotope change curve. The diffusion coefficient of the test gas is determined through the dynamic change of gas diffusion. The fractionation coefficient of the test gas isotope is determined through the diffusion coefficient of the test gas or the flux of the test gas in the diffusion component.

2. The experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile matter according to claim 1, characterized in that: The heat insulation mechanism includes a heat insulation sleeve and an electric heater. The heat insulation sleeve is sleeved outside the diffusion fractionation mechanism, and the electric heater is arranged inside the heat insulation sleeve. The electric heater is electrically connected to the numerical control system.

3. An experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components according to claim 1, characterized in that: Intake mechanism one includes intake pipeline one and compressor one. Intake pipeline one is used to introduce test gas, and compressor one is arranged on intake pipeline one.

4. An experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components according to claim 1, characterized in that: Intake mechanism two includes intake pipeline two and compressor two. Intake pipeline two is used to introduce carrier gas, and compressor two is arranged on intake pipeline two.

5. An experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatiles according to claim 1, characterized in that: Sampling mechanism one includes copper pipe sampling tube one. One end of copper pipe sampling tube one is connected to chamber A through valve one, and the other end of copper pipe sampling tube one is provided with valve two. Two sampling clips one are arranged in parallel between valve one and valve two.

6. An experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components according to claim 1, characterized in that: Sampling mechanism two includes copper pipe sampling tube two. One end of copper pipe sampling tube two is connected to chamber B through valve three, and the other end of copper pipe sampling tube two is provided with valve four. Two sampling clips two are arranged in parallel between valve three and valve four.

7. An experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components according to claim 1, characterized in that: In S2, the test gas and the carrier gas are saturated with water vapor before being introduced. The temperatures of chamber A and chamber B are both 100°C - 300°C, and the pressures are both 0 - 30 Mpa.

8. An experimental device for measuring the fractionation coefficient of rare gas isotopes in geothermal volatile components according to claim 1, characterized in that: In S4, when the gas flowing out of chamber B is in a steady state, the fractionation coefficient of the test gas isotope is represented by the ratio of the diffusion coefficients of the isotopes, and the calculation formula is as follows. Among them, is the concentration ratio of the test gas isotopes i and j in chamber A, C i (0) is the concentration of the test gas isotope i in chamber A, C j (0) is the concentration of the test gas isotope j in chamber A; is the flux of the test gas entering chamber B through the diffusion component, C i (L) is the concentration of test gas isotope i in chamber B, C j (L) is the concentration of test gas isotope j in chamber B; D i is the diffusion coefficient of isotope i, D j is the diffusion coefficient of isotope j; When the gas flowing out of chamber B is in an unsteady state, the fractionation coefficient of the test gas isotope is calculated from the unsteady gas flux of the test gas in the diffusion module. The calculation formula for the unsteady gas flux of the test gas is as follows. Among them, F i is the flux of the test gas diffusion in chamber B, t is the experimental time, t = 0 represents the start of the experiment, that is, when chamber A is completely filled with the test gas; t = L 2 / 6D i When it represents the flux F of chamber B i no longer increases, that is, the stable time point; x = 0 or x = L. When x = 0, C i (x) represents the concentration of isotope i in chamber A. When x = L, C i (x) represents the concentration of isotope i in chamber B. D i is the diffusion coefficient of isotope i, and L is the thickness of the diffusion component; The derivative at the steady time point of the unsteady gas flux is the fractionation coefficient of isotope i and isotope j.

Images