Device and method for collecting water isotope samples in gas at normal pressure

Abstract

In order to solve the technical problem that the accuracy of test results is affected by the deviation between the collected water isotope ratio and the actual water isotope ratio in the gas in the existing collection method, the present invention discloses a device and method for collecting water isotope samples in gas under normal pressure, wherein the collection device includes a rigid gas collection container, a water collection unit and a vacuum pump; the rigid gas collection container is used to collect water-containing gas; the water collection unit is used to adsorb or freeze the water isotope sample in the water-containing gas; the rigid gas collection container is provided with a monitoring unit for monitoring the internal environment of the rigid gas collection container; the inlet end of the rigid gas collection container is provided with a first valve for controlling the entry of water-containing gas, and the pipeline between the outlet end and the water collection unit is provided with a second valve; the pipeline between the rigid gas collection container and the vacuum pump is provided with a third valve; before collecting the water-containing gas, the interior of the rigid gas collection container is in a vacuum state.

Description

Technical Field

[0001] The present invention relates to a device for collecting water isotope samples in gas, and in particular to a device and method for collecting water isotope samples in gas under normal pressure. Background Art

[0002] In order to study water in the atmosphere or other gases, it is generally necessary to obtain water isotope samples in the corresponding gases, which lays the necessary foundation for humans to understand, utilize and transform nature.

[0003] Currently, there are relevant literature reports on the collection of water isotope samples. For example, the paper "Study on the Sampling Method of Tritiated Water Vapor with Silica Gel" (Zhao Yamin, Zhou Hongjie. Nuclear Electronics and Detection Technology. 1985, 5(3):148-153.) reports a method of sampling tritiated water vapor in the air using silica gel. The water is sampled by passing air through a silica gel column. However, using this method, water is not completely adsorbed. Water fractionation occurs during the collection process, affecting the test results of the water isotope ratio. At the same time, hydrogen-containing groups such as hydroxyl groups in the silica gel can also affect the test results of the water isotope ratio.

[0004] A Chinese invention patent (publication number CN113884343A) discloses an atmospheric water collection device and sampling method. This device uses low-temperature ice packs to condense water in the atmosphere. However, water fractionates during the condensation process, so the collected water isotope ratio deviates from the actual water isotope ratio in the gas.

[0005] A Chinese invention patent (publication number CN110702470A) discloses a device and method for sampling atmospheric water in equal time intervals. This method utilizes a liquid nitrogen condenser to condense water from the air. However, when using this method, water fractionation will also occur during the condensation process, causing the collected water isotope ratio to deviate from the actual value of water in the gas.

[0006] In summary, the existing methods for collecting water isotope samples will cause the final collected water isotope ratio to deviate from the actual water isotope ratio in the gas, thereby affecting the accuracy of the test results. Summary of the Invention

[0007] In order to solve the technical problem that the existing collection method affects the accuracy of the test results due to the deviation between the collected water isotope ratio and the actual water isotope ratio in the gas, the present invention provides a device and method for collecting water isotope samples in gas under normal pressure.

[0008] In order to achieve the above objectives, the technical solutions of the present invention are as follows:

[0009] A device for collecting water isotope samples in gas at normal pressure, which is special in that:

[0010] It includes a rigid gas collection container, a water collection unit and a vacuum pump respectively connected to the rigid gas collection container through pipelines;

[0011] The rigid gas collection container is used to collect water-containing gas; the water collection unit is used to collect water isotope samples in the water-containing gas by adsorption or freezing;

[0012] The rigid gas collection container is provided with a monitoring unit for monitoring the internal environment of the rigid gas collection container;

[0013] The inlet end of the rigid gas collection container is provided with a first valve for controlling the entry of water-containing gas, and a second valve is provided on the pipeline between the outlet end and the water collection unit; a third valve is provided on the pipeline between the rigid gas collection container and the vacuum pump; the interior of the rigid gas collection container is in a vacuum state before collecting water-containing gas.

[0014] Furthermore, the internal pressure of the rigid gas collecting container does not exceed 1 kPa after being evacuated.

[0015] Furthermore, the monitoring unit includes a pressure sensor and a humidity sensor respectively arranged on the rigid gas collection container; the pressure sensor is used to measure the pressure of the water-containing gas collected in the rigid gas collection container; the humidity sensor is used to measure the water vapor partial pressure in the water-containing gas collected in the rigid gas collection container.

[0016] Furthermore, the water collection unit includes a cold trap and a water collecting container arranged in the cold trap, the inlet end of the water collecting container is connected to the rigid gas collection container through a pipeline, and the temperature of the cold trap is between -273°C and -30°C.

[0017] Furthermore, the refrigeration method of the cold trap adopts a combination of one or more methods of electric refrigeration, semiconductor refrigeration, liquid nitrogen refrigeration, liquid helium refrigeration, and dry ice refrigeration; the temperature of the cold trap is between -200°C and -70°C.

[0018] Furthermore, the water collecting unit includes a water collecting container and calcium chloride particles arranged in the water collecting container, and the inlet end of the water collecting container is connected to the rigid gas collecting container through a pipeline.

[0019] In addition, the present invention also provides a method for collecting water isotope samples in gas at normal pressure. The method is special in that the method comprises the following steps:

[0020] 1] Fully desorb the water in the rigid gas collection container and the water collection unit respectively;

[0021] 2] Close the first valve and the second valve, open the third valve, and use a vacuum pump to evacuate the interior of the rigid gas collection container. When the internal pressure of the rigid gas collection container drops below 1 kPa, close the third valve;

[0022] 3] Open the first valve, and the water-containing gas enters the rigid gas collection container and is collected. When the pressure in the rigid gas collection container approaches normal pressure, close the first valve;

[0023] 4] Open the second valve, and the water in the water-containing gas in the rigid gas collection container diffuses into the water collection unit and is adsorbed or frozen by the water collection unit, thereby completing the collection of water isotope samples in the gas under normal pressure.

[0024] Furthermore, in step 1], the desorption is performed by heating, dry gas purging, vacuuming or a combination of several methods.

[0025] Furthermore, in step 4], when the humidity sensor shows that the water vapor partial pressure in the water-containing gas is lower than 1 Pa, the second valve is closed, and the water in the water-containing gas is adsorbed and collected in the water collecting container loaded with calcium chloride.

[0026] Furthermore, in step 4], when the humidity sensor shows that the water vapor partial pressure in the water-containing gas is close to the saturated vapor pressure of water at the cold trap temperature, the second valve is closed, and the water in the water-containing gas is frozen and collected in the water collecting container.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The collection device of the present invention uses a rigid gas collection container combined with a vacuum pump to collect water isotope samples in water-containing gas under normal pressure. The rigid gas collection container itself is not easily deformed, and the entire device is connected by pipes and controlled by valves, with high overall sealing. The collection efficiency of water isotope samples in water-containing gas is high, almost all water is collected, and the influence of fractionation can be ignored. As a result, the isotope ratio of the collected water isotope sample is slightly different from the actual value, the sample is highly representative, and the detection results based on the sample are more accurate.

[0029] 2. The water collection unit of the present invention can collect water isotope samples by low-temperature freezing, which will not introduce other impurities, and the water isotope samples finally collected are highly representative.

[0030] 3. The water collection unit of the present invention can also adopt an adsorption collection method. Since calcium chloride itself does not contain hydrogen-containing groups, this method will not contaminate the collected water isotope sample, and the water isotope sample finally collected is highly representative.

[0031] 4. The collecting device of the present invention has a simple structure, low cost, no easily consumable components, convenient equipment maintenance, high reliability, easy operation, and is convenient for storage, transportation and use.

[0032] 5. The collection method of the present invention does not require external power during the collection of water isotope samples, making it more environmentally friendly. Furthermore, if calcium chloride is used as a water absorbent, the water collection process does not require cooling or heating, thus saving energy and costs, making it more environmentally friendly.

[0033] 6. When the collection method of the present invention collects water through a low-temperature cold trap, the water isotope sample is directly collected in a water collection container. This sample can be used directly for corresponding testing later without the need for secondary processing of the sample, which is more convenient.

[0034] 7. The collection method of the present invention allows the water collection container to be replaced after completing one water isotope sample collection, and then the next collection work can be carried out, thus saving on-site operation time.

[0035] 8. The collection method of the present invention can adjust the temperature of the cold trap as needed, balance the relationship between the demand and cost of water isotope samples, avoid waste of cost and energy, save costs, and has a wide range of applications; at the same time, it can also adjust the volume of the rigid gas collection container and the water collection container according to the demand of the water isotope sample and the humidity of the gas, with good flexibility and a wide range of applications.

[0036] 9. The collection method of the present invention uses calcium chloride as a water absorbent when collecting water isotope samples by adsorption. Compared with other water absorbents such as CaSO4 that do not contain hydrogen-containing groups, calcium chloride has a large water adsorption capacity at low partial pressure. When other conditions are the same, less water absorbent can be used, while the volume of the water collection container can be reduced, which is low in cost and good in economy. At the same time, the volume of the water collection container and the filling amount of calcium chloride can be adjusted according to the needs of the water isotope sample, which is flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of embodiment 1 of the device for collecting water isotope samples in gas under normal pressure of the present invention.

[0038] Figure 2 It is a structural schematic diagram of a second embodiment of a device for collecting water isotope samples in gas at normal pressure according to the present invention.

[0039] The reference numerals are as follows:

[0040] 1- Rigid gas collection container, 2- Water collection unit, 3- Vacuum pump, 4- First valve, 5- Second valve, 6- Third valve, 7- Pressure sensor, 8- Humidity sensor. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments do not limit the scope of protection of the present invention in any way.

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment provides a device for collecting water isotope samples in gas at normal pressure, including a rigid gas collecting container 1, a water collecting unit 2 and a vacuum pump 3 respectively connected to the rigid gas collecting container 1 through pipelines.

[0044] The rigid gas collection container 1 is used to collect water-containing gas, which can be atmospheric air or other gases, wherein the partial pressure of water vapor is above 1 Pa. A first valve 4 for controlling the entry of water-containing gas is provided at the inlet end of the rigid gas collection container 1, and a second valve 5 is provided on the pipeline between the outlet end and the water collection unit 2; a third valve 6 is provided on the pipeline between the rigid gas collection container 1 and the vacuum pump 3; before collecting water-containing gas, the interior of the rigid gas collection container 1 is in a vacuum state, and the vacuum pressure does not exceed 1 kPa. The shape and volume of the rigid gas collection container 1 can be specifically designed according to actual needs, and the volume can generally be between tens of milliliters and tens of cubic meters. The rigid gas collection container 1 can be set to a single inlet or multiple inlets to improve the collection efficiency. The rigid gas collection container 1 in this embodiment is a stainless steel gas cylinder.

[0045] Rigid gas collection container 1 is also equipped with a monitoring unit for monitoring the internal environment of rigid gas collection container 1. The monitoring unit includes a pressure sensor 7 and a humidity sensor 8, respectively, which are provided on the rigid gas collection container. Corresponding monitoring modules can also be provided based on actual measurement requirements. Pressure sensor 7 measures the pressure of the water-containing gas collected within rigid gas collection container 1 and can be a mechanical pressure gauge, electronic pressure gauge, or vacuum gauge. Humidity sensor 8 measures the water vapor partial pressure of the water-containing gas collected within rigid gas collection container 1 and can be a hygrometer or dew point meter.

[0046] The water collection unit 2 is used to freeze and store water in the water-containing gas. The water collection unit 2 includes a cold trap and a water collecting container arranged in the cold trap. The inlet end of the water collecting container is connected to the rigid gas collection container 1 through a pipeline. The cold trap temperature is between -273°C and -30°C. In this embodiment, the cold trap temperature is preferably between -200°C and -70°C. At this temperature, the freezing adsorption method will not introduce other impurities. The water isotope sample finally collected is highly representative and has a low cost.

[0047] The water collection container can be designed with a specific shape and volume based on actual needs. The volume generally ranges from a few milliliters to several hundred milliliters. When in use, the entire water collection container, except for the inlet, is placed in a cold trap. The cold trap can be a combination of electric refrigeration, semiconductor refrigeration, liquid nitrogen refrigeration, liquid helium refrigeration, or dry ice refrigeration.

[0048] A method for collecting water isotope samples in gas at normal pressure comprises the following steps:

[0049] 1] Fully desorb water from both the rigid gas collection container 1 and the 10 mL water collection container, cool to room temperature, and weigh. This embodiment utilizes heating, dry gas purging, and vacuuming, or a combination of these methods, to fully desorb water from both the rigid gas collection container 1 and the water collection container in the water collection unit 2.

[0050] The rigid gas collection container 1 uses a 10L stainless steel gas cylinder (calibrated to hold 10.127L), the humidity sensor 8 uses a dew point meter, the pressure sensor 7 uses a pressure transmitter (range 200kPa), and the cold trap uses a liquid nitrogen cold trap (temperature -196°C). Before collection, the device must be leak-tested to ensure airtightness, and all valves must be closed.

[0051] 2] Open the third valve 6 and evacuate the interior of the rigid gas collection container 1 through the vacuum pump 3. When the internal pressure of the rigid gas collection container 1 drops to 30 Pa, close the third valve 6 and use a dew point meter to test the humidity of the water-containing gas.

[0052] 3] Open the first valve 4, and the water-containing gas enters the rigid gas collection container 1 and is collected. When the pressure in the rigid gas collection container 1 is close to normal pressure, close the first valve 4.

[0053] 4] Open the second valve 5, and the water in the water-containing gas in the rigid gas collection container 1 diffuses into the water collection unit 2 through the pipeline and freezes. After standing for about 50 minutes, the dew point meter shows that the water vapor partial pressure in the rigid gas collection container 1 reaches 0.4 Pa. At this time, close the second valve 5 to complete the collection of water isotope samples in the gas at normal pressure.

[0054] After the collection is completed, the water collecting container is removed, the water on the outer surface is desorbed and cooled to room temperature, the second valve 5 is opened, and the pressure in the water collecting container is weighed after it is balanced with the atmosphere. Finally, the hydrogen and oxygen isotope ratios are tested based on the collected water isotope sample.

[0055] In this example, a dew point meter was used to measure the atmospheric water vapor partial pressure to be 2478 Pa at a temperature of approximately 25°C. Based on the ideal gas equation, the mass of water in the atmosphere was estimated to be approximately 0.1824 g. The mass of the water collection container increased by 0.1826 g after accumulating water. Considering the measurement error of the water vapor partial pressure (the uncertainty of the humidity measurement is approximately 1%), the collection rate of the water isotope sample was close to 100%.

[0056] Laser water isotope analyzer is used to directly test the hydrogen and oxygen isotope ratios of water in the atmosphere. D (δ value of deuterium content) and δ 18 O ( 18 The δ values of O content) were -110.8 and -16.17 respectively. The isotope analyzer was used to test the hydrogen and oxygen isotope ratios of the water isotope samples collected in this embodiment. The measured δ D and δ 18 O The hydrogen and oxygen isotope ratios of the water isotope samples collected in this embodiment have very small relative deviations from the hydrogen and oxygen isotope ratios directly measured in the gas, both falling within the measurement uncertainty range (the measurement uncertainty of the δ value is approximately 1), indicating high measurement accuracy.

[0057] Example 2

[0058] like Figure 2 As shown, this embodiment differs from the first embodiment in that the water collection unit 2 includes a water collection container and calcium chloride particles disposed therein. The inlet of the water collection container is connected to the rigid gas collection container 1 via a pipeline. The volume of the water collection container and the amount of calcium chloride loaded can be adjusted according to the needs of the water isotope sample. Calcium chloride is used as a water absorbent, which has a high water absorption capacity at low partial pressures. The collection process requires no cooling, heating, or external power, thus saving energy and costs, and being more environmentally friendly.

[0059] In addition, calcium chloride is used as a water absorbent. Calcium chloride itself does not contain hydrogen-containing groups, so it will not contaminate the collected water isotope samples. The samples are highly pure and representative.

[0060] The collection method of this embodiment includes the following steps:

[0061] 1] Fully desorb the water from the water collection container and the rigid gas collection container 1, which contain approximately 20g of calcium chloride. Cool the temperature to room temperature and then weigh. The rigid gas collection container 1 uses a 10L stainless steel gas cylinder (calibrated to hold 10.127L), the humidity sensor 8 uses a dew point meter, and the pressure sensor 7 uses a pressure transmitter (range 200kPa). Before collection, perform a leak test on the entire device to ensure its tightness. Then, fully desorb the water adsorbed on the inner surface of the rigid gas collection container 1, close all valves, and cool to room temperature.

[0062] This embodiment adopts one or a combination of heating, dry gas purging, and vacuuming to fully adsorb the water in the rigid gas collection container 1 and the water collection container.

[0063] 2] Open third valve 6 and evacuate the interior of rigid gas collection container 1 using vacuum pump 3. Ensure that the rigid gas collection container 1 does not significantly deform during evacuation. When the pressure inside rigid gas collection container 1 drops to 30 Pa, close third valve 6 and test the humidity of the water-containing gas using a dew point meter.

[0064] 3] Open the first valve 4, and the water-containing gas enters the rigid gas collection container 1 and is collected. When the pressure in the rigid gas collection container 1 is close to normal pressure, close the first valve 4.

[0065] 4] Open the second valve 5, and the water in the hydrous gas in the rigid gas collection container 1 enters the water collecting container through the pipeline. After standing for about 30 minutes, the dew point meter shows that the water vapor partial pressure of the rigid gas collection container 1 reaches 0.5 Pa. At this time, close the second valve 5, and the water collecting container absorbs the water in the hydrous gas through calcium chloride adsorption, thereby completing the collection of water isotope samples in the gas under normal pressure.

[0066] When testing, the water collecting container is removed and weighed, and then all the water in the water collecting container is removed or partially removed as needed to obtain a water isotope sample, and then the hydrogen and oxygen isotope ratios in the sample are tested.

[0067] If you need to collect samples from multiple locations on site, you can replace the water collection container after completing one collection and then proceed to the next collection, thereby saving on-site operation time.

[0068] The dew point meter was used to measure the water vapor partial pressure in the atmosphere to be 2513 Pa, and the temperature was approximately 25°C. Based on the ideal gas equation, the mass of water in the atmosphere was approximately 0.1850 g. The actual mass of the water collection container was measured to have increased by 0.1848 g. Based on this, the water collection efficiency was calculated to be 99.9%, which is a relatively high water collection rate.

[0069] Laser water isotope analyzer is used to directly test the hydrogen and oxygen isotope ratios of water in the atmosphere.D (δ value of deuterium content) and δ 18 O ( 18 The isotope analyzer was used to test the hydrogen and oxygen isotope ratios of the water isotope samples collected in this embodiment. The measured δ D and δ 18 O The values of -110.1 and -16.12, respectively, indicate that the relative deviations between the hydrogen and oxygen isotope ratios of the water isotope sample collected in this example and the hydrogen and oxygen isotope ratios directly measured in the gas are very small, both falling within the measurement uncertainty range (the measurement uncertainty of the δ value is approximately 1), indicating a high measurement accuracy.

Claims

1. A device for collecting water isotope samples in gas at normal pressure, characterized by: It comprises a rigid gas collecting container (1), a water collecting unit (2) and a vacuum pump (3) respectively connected to the rigid gas collecting container (1) via pipelines; The rigid gas collection container (1) is used to collect water-containing gas; the water collection unit (2) is used to collect water isotope samples in the water-containing gas by adsorption or freezing methods; The rigid gas collection container (1) is provided with a monitoring unit for monitoring the internal environment of the rigid gas collection container (1); The inlet end of the rigid gas collection container (1) is provided with a first valve (4) for controlling the entry of water-containing gas, and the pipeline between the outlet end and the water collection unit (2) is provided with a second valve (5); the pipeline between the rigid gas collection container (1) and the vacuum pump (3) is provided with a third valve (6); the interior of the rigid gas collection container (1) is in a vacuum state before collecting the water-containing gas; the pressure in the rigid gas collection container (1) after evacuation does not exceed 1 kPa; The monitoring unit comprises a pressure sensor (7) and a humidity sensor (8) respectively arranged on the rigid gas collection container; the pressure sensor (7) is used to measure the pressure of the water-containing gas collected in the rigid gas collection container (1); and the humidity sensor (8) is used to measure the water vapor partial pressure in the water-containing gas collected in the rigid gas collection container (1).

2. The device for collecting water isotope samples in gas at normal pressure according to claim 1, characterized in that: The water collection unit (2) comprises a cold trap and a water collection container arranged in the cold trap, the inlet end of the water collection container is connected to the rigid gas collection container (1) via a pipeline, and the temperature of the cold trap is between -273°C and -30°C.

3. The device for collecting water isotope samples in gas at normal pressure according to claim 2, characterized in that: The refrigeration method of the cold trap adopts a combination of one or more methods of electric refrigeration, semiconductor refrigeration, liquid nitrogen refrigeration, liquid helium refrigeration, and dry ice refrigeration; the temperature of the cold trap is between -200°C and -70°C.

4. The device for collecting water isotope samples in gas at normal pressure according to claim 3, characterized in that: The water collecting unit (2) comprises a water collecting container and calcium chloride particles arranged in the water collecting container, and the inlet end of the water collecting container is connected to the rigid gas collecting container (1) via a pipeline.

5. A method for collecting water isotope samples in gas at normal pressure, characterized in that: The device for collecting water isotope samples in gas at normal pressure according to any one of claims 1 to 4 comprises the following steps: 1] Fully desorbing the water in the rigid gas collection container (1) and the water collection unit (2); 2] Close the first valve (4) and the second valve (5), open the third valve (6), and evacuate the interior of the rigid gas collection container (1) using the vacuum pump (3). When the internal pressure of the rigid gas collection container (1) drops below 1 kPa, close the third valve (6); 3] Open the first valve (4), and the water-containing gas enters the rigid gas collection container (1) and is collected. When the pressure in the rigid gas collection container (1) approaches normal pressure, close the first valve (4); 4] Open the second valve (5), and the water in the water-containing gas in the rigid gas collection container (1) diffuses into the water collection unit (2), and is adsorbed and collected or frozen and collected by the water collection unit (2), thereby completing the collection of water isotope samples in the gas under normal pressure.

6. The method for collecting water isotope samples in gas at normal pressure according to claim 5, characterized in that: In step 1], the desorption is carried out by heating, dry gas purging, vacuuming or a combination of several methods.

7. The method for collecting water isotope samples in gas at normal pressure according to claim 5 or 6, characterized in that: In step 4], when the humidity sensor (8) shows that the water vapor partial pressure in the water-containing gas is lower than 1 Pa, the second valve (5) is closed, and the water in the water-containing gas is adsorbed and collected in the water collection container loaded with calcium chloride.

8. The method for collecting water isotope samples in gas at normal pressure according to claim 5 or 6, characterized in that: In step 4], when the humidity sensor (8) shows that the water vapor partial pressure in the water-containing gas is close to the saturated vapor pressure of water at the cold trap temperature, the second valve (5) is closed, and the water in the water-containing gas is frozen and collected in the water collecting container.

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