Simulated lunar soil preparation system with low water content and known H isotope

Abstract

The invention discloses a low water content and H isotope known simulated lunar soil preparation system, which comprises a standard water source sample pipe, a vaporization pipeline, a sample chamber, a vacuum pipeline and a dry nitrogen pipeline, the standard water source sample pipe is connected with the gas inlet side of the sample chamber through the vaporization pipeline, the gas outlet side of the sample chamber is connected with the vacuum pipeline, and the dry nitrogen pipeline is connected with the sample chamber through the vaporization pipeline. The vaporization pipeline is used for vacuumizing to a set vacuum degree, comprises a temperature-controlled buffer chamber, a first pipeline, a mixing chamber and a second pipeline, and is used for inhibiting low vacuum and H isotope fractionation; a first pressure gauge is arranged on the gas inlet side of the sample chamber, a second pressure gauge is arranged on the gas outlet side of the sample chamber, and when the pipeline pressure of the gas inlet side and the gas outlet side of the sample chamber is monitored to be stable, it is judged that the steam and soil combination process is finished. The method can be used for preparing the simulated lunar soil with low water content and known H isotope.

Description

Technical Field

[0001] The present invention relates to a system for preparing simulated lunar soil with low water content and known H isotope. Background Art

[0002] Real lunar soil is scarce and hard to come by, and cannot meet engineering needs. In actual engineering projects, simulated lunar soil is generally used instead of real lunar soil for related research.

[0003] The study of water ice in the lunar soil in the permanent shadows near the lunar poles is an important exploration topic. Detecting the D / H isotope ratio of lunar water ice can reveal the main source and evolution of lunar water ice. Whether the water ice in the permanent shadows of the moon is mainly primary or injected later; whether it is injected by solar wind protons or brought by comets or meteorite impacts; this information has important academic value.

[0004] Some experiments have been conducted at home and abroad to simulate the properties of ice regolith simulants, such as preparing the thermal properties of frozen water-containing Mars regolith simulants through water vapor diffusion; using a manual pump sprayer and a cement mixer to prepare water-containing lunar soil, and preparing water-containing simulated lunar soil with a water content of 1.78% to 11.9%; using a peristaltic pump to pump a premix similar to "mud" into a cryogenic container to prepare water-containing lunar soil; using a steel skeleton cage, semi-permeable flannel and a water droplet disperser to prepare simulated lunar soil with a water content of 1% to 14%. The samples prepared by these methods have a high water content and are not suitable for simulated lunar soil containing large particles.

[0005] Chinese patent document CN116223142A discloses a composite device for preparing and transferring simulated lunar soil by vacuum drying water molecules and vapor deposition, which solves the problem that the traditional lunar soil preparation process cannot eliminate the interference of impurity gas factors and improves the accuracy of the prepared water content, but fails to provide an isotope abundance standard. Currently, there is no method for preparing simulated lunar soil with low water content in a vapor-soil combined state with known H isotopes. Summary of the invention

[0006] The purpose of the present invention is to provide a system for preparing simulated lunar soil with low water content and known H isotope, so as to prepare simulated lunar soil with low water content in a vapor-soil combined state with known H isotope.

[0007] To this end, the present invention provides a system for preparing simulated lunar soil with low water content and known H isotopes, comprising: a standard water source sample tube, a vaporization pipeline, a sample chamber, a vacuum pipeline, and a dry nitrogen pipeline. The standard water source sample tube is connected to the air inlet side of the sample chamber through the vaporization pipeline, and the air outlet side of the sample chamber is connected to the vacuum pipeline for evacuating to a set vacuum degree. The vaporization pipeline comprises a temperature-controlled buffer chamber, a first pipeline, a mixing chamber, and a second pipeline to inhibit the adsorption of water vapor on the tube wall and H isotope fractionation; the dry nitrogen pipeline comprises a nitrogen bottle, a mass flowmeter, a third pipeline, and a fourth pipeline, the nitrogen bottle is connected to the mixing chamber through the third pipeline, and the nitrogen bottle is connected to the sample chamber through the fourth pipeline; a pressure gauge 1 is provided on the air inlet side of the sample chamber and a pressure gauge 2 is provided on the air outlet side of the sample chamber. During the steam-soil preparation process, when the readings of the pressure gauge 1 and the pressure gauge 2 are stable, it is determined that the steam-soil combination process is completed.

[0008] According to the simulated lunar soil preparation system of the present invention, it is possible to prepare simulated lunar soil with low water content and known H isotope.

[0009] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a structural diagram of the system for preparing simulated lunar soil with low water content and known H isotope of the present invention; Figure 2 This is an operation flow chart of the system for preparing simulated lunar soil with low water content and known H isotope according to the present invention; Figure 3 is a schematic structural diagram of a sample chamber of the present invention; Figure 4 is a schematic diagram of the combination of steam and soil in the sample chamber of the present invention; Figure 5 The results of the moisture content test of the simulated lunar soil in a vapor-soil combination state prepared according to the method of the present invention are shown; Figure 6 The standard deviation results of moisture content of samples in the same layer of four groups of tests of the present invention are shown; Figure 7 and Figure 8 The H isotope measurement results of two groups of samples of the present invention are shown. DETAILED DESCRIPTION

[0011] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0012] In order to achieve the preparation of low water content and H isotope simulated lunar soil and verify the feasibility of the method, the present invention includes three parts.

[0013] 1. Preparation of standard hydrogen isotope water samples In the present invention, four sample waters were prepared using standard substances, and then tested and calibrated using a water vapor isotope analyzer. The results are shown in the following table.

[0014] Table 1. Standard values ​​and expanded uncertainty of δD of reference elements and measurement results of deuterium values ​​of configured water samples 2. Preparation system of simulated lunar soil with low water content and known H isotope Combined with reference Figure 2 ,This preparation system mainly includes a standard water source, a buffer chamber, a mixing chamber, a cold trap collection system, a sample chamber, a dry nitrogen system, a temperature control system, a pressure monitoring system, a vacuum system and related ,pipeline components and valves.

[0015] The standard water source used in the experiment was the calibrated nominal value isotope sample in Table 1.

[0016] Due to the adsorption characteristics of water molecules, even in ultra-low pressure, the inner surface of stainless steel will still adsorb a large amount of water molecules, and even accumulate in the pipeline. Adsorption or condensation will cause phase change of water, so a buffer chamber is added between the standard water source and the lunar soil sample, and the temperature of the entire system chamber and pipeline is controlled, and the nitrogen and water vapor outlets are used for molecular collision and mixing. Both nitrogen and water vapor outlets use 1 / 4-inch tubes.

[0017] The temperature control system consists of a glass fiber heating belt, a K-type patch thermocouple and a transmitter.

[0018] The sample chamber is composed of several sections of 5 cm long KF40 stainless steel pipes connected directly by clamps, which facilitates free length adjustment and segmented sampling.

[0019] Pressure monitoring is carried out through two Pufa pressure gauges above and below the sample filling barrel, the upper one is a full-scale pressure gauge and the lower one is a low-pressure (1330 Pa) pressure gauge.

[0020] Combined with reference Figure 3 The preparation process of this preparation method is as follows.

[0021] Before the formal experiment begins, the pipeline temperature control system is turned on to preheat the vaporization pipeline and stabilize the temperature at 60°C to ensure the vaporization of the standard water source without producing isotope fractionation between the liquid phase and the gas phase, and to produce water vapor with a known isotopic composition within a certain concentration range.

[0022] Use helium leak detector to confirm the system, the leakage rate is better than 1*10-9Pa.m 3 / s, the system vacuum is considered to be good, open the nitrogen flow control valve and vacuum system, open all valves, and use dry nitrogen to purge the system for degassing for 1 hour.

[0023] Close the nitrogen flow control valve and the vacuum system, close valve 2, valve 5 and valve 6, close the baffle valve and remove the sealed lunar soil sample chamber; close valve 1, open the KF25 clamp and remove the standard water source sample tube.

[0024] Transfer the removed lunar soil sample chamber and standard water source sample tube to the anhydrous nitrogen atmosphere glove box for sampling.

[0025] The particle size parameters of the simulated lunar soil dry soil samples are the particle size distribution parameters of typical working conditions. When loading dry soil samples, since the samples are dry and most of them are dust particles of tens of microns, it is necessary to control static electricity and dust to ensure the sealing of phenyl silicone rubber seals and valves.

[0026] In order to ensure the uniformity and density of the particle size distribution, the samples are allowed to fall naturally during loading without vibration or compaction.

[0027] After loading the samples in the glove box, close the flap valve of the lunar soil sample chamber; close valve 1 of the standard water source sample tube, transfer them from the glove box, and then connect them to the original system through the flap valve and KF25 clamp. Close valves 4 and 5, open the vacuum system, open other valves, and evacuate the residual air in the pipeline, the nitrogen in the lunar soil sample chamber and the internal pores of the standard water source sample tube.

[0028] Turn off the vacuum system, close valve 1, use a liquid nitrogen barrel to bathe the standard water source sample in liquid nitrogen for 15 minutes to freeze the standard water source to prevent sublimation, keep valves 4 and 5 closed, open other valves, and turn on the vacuum system to degas and evacuate the system.

[0029] After the value displayed on pressure gauge 2 is less than 10 Pa, turn off the vacuum system, close valve 3, open valve 1, and use the hollow heating tube to continue heating for about 10 minutes to completely vaporize the standard water source sample in the buffer chamber.

[0030] Open the vacuum system, open valve 3, and allow the vaporized standard water source to enter the mixing chamber. Control the pumping speed of the vacuum system's vacuum pump end, mix for about 15 minutes, and then observe the readings of the two pressure gauges. When the two readings are almost stable, the vapor-soil combination reaches adsorption equilibrium and the preparation is complete.

[0031] The reading on the upper pressure gauge is used to determine whether the water source is exhausted and terminate the test to prevent continuous vacuuming from causing the water vapor in the sample to be sucked away.

[0032] During the preparation process, the standard water source isotope sample used was GBW04458, the temperature was controlled at 58~62℃, and the pumping time was controlled at about 15 minutes to 20 minutes.

[0033] After the preparation is completed, the sample chamber is unsealed and transferred to a water-free glove box for rapid layered sampling and shaking. The samples are then divided into moisture content sample tubes and isotope sample tubes for subsequent testing of the moisture content and δD value of the steam soil.

[0034] 3. Water content and H isotope test results and analysis Moisture content test results Four sets of tests were conducted on the moisture content using a Karl Fischer moisture meter. The size of the lunar soil sample chamber was controlled to be five straight-through tubes in each test. Figure 3 The schematic diagram of the combination of gas and soil is shown in Figure 4 As shown, in Figure 3 and Figure 4 In the figure, sealing gaskets 2 are arranged between adjacent straight tubes 1, lunar soil 3 is contained in the straight tubes 1, and the water vapor path 4 passes through the lunar soil 3 to realize the combination of vapor and soil.

[0035] The amount of water sample used in each test is 30 ml. When sampling for moisture content testing, samples are taken from top to bottom in order of depth number 1, 2, 3, 4, 5, with the top being number 1 and the bottom being number 5. The moisture content test results are as follows: Figure 5 shown.

[0036] For the four groups of tests, the moisture content values ​​of the same layer of samples obtained in each test were analyzed for deviation. The results are as follows: Figure 6 shown.

[0037] Depend on Figure 6 It can be seen that the standard deviation of the moisture content results of the same layer samples obtained in the four groups of tests is less than 0.1%, with good consistency, and the moisture content of the samples obtained is less than 1wt%. It can be seen that by controlling the time of each test, the amount of water sample, the pressure difference, the pumping speed and other influencing factors unchanged, a very low moisture content steam-soil combined water-containing simulated lunar soil with good consistency can be obtained. And from the perspective of depth, the overall moisture content distribution in the sample chamber has a trend of decreasing first and then increasing from top to bottom.

[0038] Hydrogen isotope relative abundance δD measurement results The relative abundance of hydrogen isotopes δD was measured using a liquid water isotope analyzer (model GLA431-TLWIA). Two groups of isotope tests were conducted on a total of 10 samples. The test results are as follows: Figure 7 and Figure 8 As shown in the figure. The horizontal axis is δD (unit: ‰), and the vertical axis represents the number of layers. Figure 7 and Figure 8 It can be seen that the trends of the two groups of test results are basically consistent, with δD ranging from -58.44‰ to -1.90‰, both of which are less than the original water sample value of 8.3‰.

[0039] Since the lighter H2O in the first and second layers of pores is continuously desorbed from the surface of lunar soil particles and enters the mobile phase; the flow capacity of the bottom layer pore outlet is limited, the relative abundance δD of hydrogen isotopes in the third and fourth layers is close to the original value of 8.3‰, so these two layers are taken as effective steam soil.

[0040] The simulated lunar soil of the present invention has two characteristics: low water content and standard isotope steam-soil combination. The standard low water content and water-containing simulated lunar soil is used for detection limit verification of the payload instrument to determine the measurement lower limit of the payload instrument; the sample with standard isotope value is used for ground calibration of the payload instrument to determine the measurement error of the payload instrument.

[0041] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A system for preparing simulated lunar soil with low water content and known H isotopes, characterized in that: include: Standard water source sample tube, vaporization pipeline, sample chamber, vacuum pipeline, dry nitrogen pipeline, The standard water source sample tube is connected to the air inlet side of the sample chamber through a vaporization pipeline, and the air outlet side of the sample chamber is connected to a vacuum pipeline for evacuating to a set vacuum degree. The vaporization pipeline includes a temperature-controlled buffer chamber, a first pipeline, a mixing chamber, and a second pipeline to inhibit the adsorption of water vapor on the tube wall and H isotope fractionation; The dry nitrogen pipeline includes a nitrogen bottle, a mass flow meter, a third pipeline and a fourth pipeline, the nitrogen bottle is connected to the mixing chamber through the third pipeline, and the nitrogen bottle is connected to the sample chamber through the fourth pipeline; A pressure gauge 1 is provided on the air inlet side of the sample chamber and a pressure gauge 2 is provided on the air outlet side of the sample chamber. During the steam-soil preparation process, when the readings of the pressure gauge 1 and the pressure gauge 2 are stable, it is determined that the steam-soil combination process is completed.

2. The system for preparing simulated lunar soil with low water content and known H isotope according to claim 1, characterized in that: The temperature of the vaporization pipeline is controlled to 58-62°C.

3. The system for preparing simulated lunar soil with low water content and known H isotope according to claim 1, characterized in that: The vaporization pipeline also includes a temperature control system, which includes a glass fiber heating belt, a K-type patch thermocouple and a transmitter, and is used for heating, controlling the temperature and detecting the temperature of the vaporization pipeline.

4. The system for preparing simulated lunar soil with low water content and known H isotope according to claim 1, characterized in that: The standard water source sample tube is provided with a valve, and the standard water source sample tube is connected to the system through a clamp. The system also includes a liquid nitrogen tank for subjecting the standard water source sample tube to a liquid nitrogen bath to freeze the sample liquid and a hollow heating tube for continuously heating the standard water source sample tube to vaporize the sample liquid.

5. The system for preparing simulated lunar soil with low water content and known H isotope according to claim 1, characterized in that: The vacuum pipeline is provided with a filter and a vacuum pump. When the indications of the pressure gauge 1 and the pressure gauge 2 are stable, it is determined that the steam-soil combination process is completed.

6. The system for preparing simulated lunar soil with low water content and known H isotope according to claim 1, characterized in that: The sample chamber comprises a plurality of straight-through pipes, and adjacent straight-through pipes are connected by clamps. The air inlet side and the air outlet side of the sample chamber are respectively provided with baffle valves.

7. The system for preparing simulated lunar soil with low water content and known H isotope according to claim 1, characterized in that: The preparation process of the preparation system is as follows: S1. Connect the unloaded sample chamber and the standard water source sample tube to the system, heat the vaporization pipeline, and evacuate and degas; S2. After leak detection of the system pipeline, remove the sample chamber and the standard water source sample tube from the system and move them to the glove box for sample loading; S3. Load the standard water source and dry soil separately and connect them to the system. The standard water source sample tube is first placed in a liquid nitrogen bath for 15 minutes in the vaporization pipeline to freeze the standard water source to prevent sublimation. The air in the system pipeline is emptied, and then a hollow heating tube is used to completely vaporize the standard water source sample into the buffer chamber to prevent H isotope fractionation. S4, by controlling the pumping speed of the vacuum pump end until the readings of the two pressure gauges are basically stable, the steam soil preparation is completed; S5. Disassemble the sample chamber from the system and transfer it to the glove box to package the samples.

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