Portable device and method for collecting water isotope samples in gas

Abstract

The present invention discloses a portable device and method for collecting water isotope samples in gas, which are used to solve technical problems such as the limited use range of existing collection devices due to their complex structure and inconvenient mobility, as well as the poor representativeness of the collected water isotope samples. The collection device includes a flexible gas collection container and a water collection unit connected to the flexible gas collection container via a pipeline; the flexible gas collection container is used to collect water-containing gas and is initially in a curled or folded form; the water collection unit is used to collect water isotope samples in the water-containing gas; a diaphragm pump and a detection unit are provided at the inlet end of the flexible gas collection container, wherein the detection unit is close to the inlet end of the flexible gas collection container; the diaphragm pump is used to provide driving force for the water-containing gas to enter the flexible gas collection container; a first valve is provided on the pipeline between the diaphragm pump and the detection unit; and a second valve is provided on the pipeline between the flexible gas collection container and the water collection unit.

Description

Technical Field

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

[0002] Water is almost everywhere in the natural environment. By testing and studying the isotope ratios of water in the atmosphere or other gases, we can deepen our understanding of meteorology, environment, energy and other fields, thereby laying the necessary foundation for humans to understand, utilize and transform nature.

[0003] To study water in the atmosphere or other gases, it is generally necessary to obtain water isotope samples from the corresponding gases. Currently, there are two main methods for sampling water in the atmosphere or other gases: one method is to place a desiccant or cold trap in an open space to directly adsorb, condense, or freeze the water in the gas. However, since this method cannot completely collect the water in the gas, there is a significant fractionation during the water adsorption, condensation, or freezing process, and the collected water isotope ratio deviates from the actual water isotope ratio in the gas. At the same time, the desiccant contains hydrogen groups, which affect the collected water isotope ratio, further causing deviations in the results and resulting in poor representativeness of the collected water isotope sample.

[0004] Another method is to add a power system to the water collection device to make the water-containing gas flow through a water absorbent or cold trap. However, since this method cannot achieve complete adsorption or freezing of water, the water in the gas will also undergo fractionation during the collection process. Therefore, the test results will also deviate from the actual water isotope ratio in the gas, resulting in poor representativeness of the collected water isotope samples.

[0005] In addition, the existing collection devices are relatively complex in structure and inconvenient to move, which limits their scope of application and makes them incapable of being used to collect water isotope samples in gases under some complex environments. Summary of the Invention

[0006] In order to solve the technical problems that the existing collection devices are limited in scope of use due to their complex structure and inconvenient mobility, and the collected water isotope samples are poorly representative, the present invention provides a portable collection device and method for water isotope samples in gas with high water collection efficiency, strong sample representativeness, wide applicability, good flexibility, simplicity, reliability, greenness and environmental protection, and easy portability.

[0007] In order to achieve the above objectives, the technical solutions of the present invention are as follows:

[0008] A portable collection device for water isotope samples in gas, which is special in that it includes a flexible gas collection container and a water collection unit connected to the flexible gas collection container through a pipeline;

[0009] The flexible gas collection container is used to collect water-containing gas, and its initial state is a curled or folded form; the water collection unit is used to collect water isotope samples in the water-containing gas;

[0010] A diaphragm pump and a detection unit are sequentially provided on the pipeline at the inlet end of the flexible gas collection container, wherein the detection unit is close to the inlet end of the flexible gas collection container; the diaphragm pump is used to provide a driving force for the water-containing gas to enter the flexible gas collection container;

[0011] A first valve is provided on the pipeline between the diaphragm pump and the detection unit; a second valve is provided on the pipeline between the flexible gas collection container and the water collection unit.

[0012] Furthermore, the flexible gas collection container is made of an elastic material or a non-elastic material or a combination of elastic and non-elastic materials, and its internal bearing pressure is 1.0 to 1.2 times the pressure of the water-containing gas.

[0013] Furthermore, the outlet pressure of the diaphragm pump does not exceed 1.2 times the pressure of the water-containing gas.

[0014] Furthermore, a flow controller is provided on the pipeline at the front end of the diaphragm pump for testing the air intake volume.

[0015] Furthermore, the water collecting unit includes a sealed 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 flexible gas collecting container through a pipeline.

[0016] Furthermore, the storage device 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 flexible 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 detection unit includes a pressure sensor and a humidity sensor.

[0019] In addition, the present invention also provides a portable method for collecting water isotope samples in gas, which is special in that the portable device for collecting water isotope samples in gas of the present invention is used, and specifically comprises the following steps:

[0020] 1] Fully absorb the water in the flexible gas collection container and water collection unit and close all valves;

[0021] 2] Expand the flexible gas collection container from its initial state and open the first valve;

[0022] 3] Start the diaphragm pump to collect the water-containing gas into the flexible gas collection container. When the pressure in the flexible gas collection container reaches 1.0 to 1.2 times the pressure of the water-containing gas, close the first valve and open the second valve. The water in the water-containing gas in the flexible gas collection container diffuses into the water collection unit and is collected.

[0023] 4] When the detection unit shows that the water vapor partial pressure in the water-containing gas in the flexible gas collection container is lower than 1 Pa, close the second valve to complete the collection of the water isotope sample.

[0024] Furthermore, in step 1], the water is fully desorbed by desorbing the water adsorbed on the inner wall of the water collecting container and the flexible gas collection container, and the desorption adopts a combination of one or more methods of heating, dry gas purging, and vacuuming; when the water collection unit adopts calcium chloride adsorption collection, the water adsorbed by the calcium chloride needs to be desorbed, and then the water collecting container is cooled to room temperature.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The collection device proposed in the present invention includes a flexible gas collection container and a water collection unit. The flexible gas collection container is used to collect water-containing gas, and the water collection unit is used to collect water isotope samples in the water-containing gas. The overall device has a simple structure, and the flexible gas collection container can be rolled or folded, so that the overall volume of the device is small, and the weight is light and the portability is good, and thus it can be applied to different testing sites. At the same time, the overall sealing of the device is high, which is conducive to the collection of water isotope samples in water-containing gas, and the collection efficiency is high. Almost all of the water is collected, and the influence of distillation can be ignored. The isotope ratio of the collected water isotope sample is slightly different from the actual value, and the sample representativeness is strong.

[0027] 2. The collection device proposed in the present invention is easy to operate, highly reliable, convenient to store, transport and use, has no easily consumable components, has low cost, is easy to maintain, and is more conducive to popularization and use.

[0028] 3. In the collection method proposed by the present invention, the partial pressure of water in the water-containing gas can be reduced to a level close to the saturated vapor pressure of water at the cold trap temperature, and the collection efficiency of water isotope samples in the gas is high.

[0029] 4. The collection method proposed in the present invention can adjust the gas collection amount in the flexible gas collection container according to the demand for water isotope samples and the humidity of the water-containing gas, and has good flexibility and a wide range of applications.

[0030] 5. The collection method proposed in the present invention does not use a water absorbent containing hydrogen groups, so it will not contaminate the collected water isotope samples, and the samples are highly representative.

[0031] 6. The collection method proposed by the present invention uses freezing to collect water isotope samples. The water isotope samples are directly collected in a water collection container, and the samples can be directly tested without secondary processing, which is convenient and quick.

[0032] 7. The collection method proposed in the present invention uses calcium chloride as a water absorbent to collect water isotope samples. Compared with other water absorbents without hydrogen groups such as CaSO4, it has a large low partial pressure water adsorption capacity. When other conditions are the same, less water absorbent can be used, and the volume of the water collector can be reduced. It has low cost, good economy and good portability.

[0033] 8. The collection method proposed in the present invention can replace the water collection unit after completing the collection of one water isotope sample, and then collect the next water isotope sample, thereby saving on-site operation time.

[0034] 9. The collection method proposed by the present invention is simple and easy to carry out. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the collecting device in Example 1 of the present invention.

[0036] Figure 2 It is a schematic structural diagram of the collecting device in the second embodiment of the present invention.

[0037] The reference numerals are as follows:

[0038] 1- Flexible gas collection container, 2- Water collection unit, 3- Diaphragm pump, 4- Detection unit, 5- First valve, 6- Second valve, 7- Pressure sensor, 8- Humidity sensor. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but these embodiments do not limit the scope of protection of the present invention in any way.

[0040] Example 1

[0041] like Figure 1 As shown, the present invention provides a portable collection device for water isotope samples in gas, comprising a flexible gas collection container 1 and a water collection unit 2 connected to the flexible gas collection container 1 through a pipeline.

[0042] The flexible gas collection container 1 is used to collect water-containing gas, which can be atmospheric gas or other gases, wherein the partial pressure of water vapor is above 1 Pa, the relative humidity does not exceed 80%, and the preferred relative humidity is not more than 60%. The initial state of the flexible gas collection container 1 is a curled or folded form, that is, it is stored in a curled or folded form. Before storage, the water adsorbed on the inner surface of the flexible gas collection container 1 has been fully desorbed, and the interior does not contain gas when stored. When it is to be used, the flexible gas collection container 1 is first unfolded from the curled or folded state. The flexible gas collection container 1 is made of elastic material or non-elastic material or a combination of elastic and non-elastic materials, and after inflation, its internal bearing pressure is 1.0 to 1.2 times the pressure of the water-containing gas, so as to prevent the water in the water-containing gas from condensing during the inflation process, affecting the collection of water, and further affecting the isotope ratio test results. There is no limitation on the shape of the flexible gas collection container 1. The volume of the flexible gas collection container 1 can be adjusted according to the requirements of the water isotope sample and the humidity of the gas, which helps to reduce costs and improve portability and economy. The flexible gas collection container 1 can also be designed as a single-port or multi-port form according to needs, thereby improving collection efficiency.

[0043] A diaphragm pump 3 and a detection unit 4 are sequentially provided on the pipeline at the inlet end of the flexible gas collection container 1, with the detection unit 4 being located near the inlet end of the flexible gas collection container 1. The diaphragm pump 3 is used to provide a driving force for the water-containing gas to enter the flexible gas collection container 1. In this embodiment, the diaphragm pump 3 is a small diaphragm pump. During the inflation process, its outlet pressure does not exceed 1.2 times the pressure of the water-containing gas. In addition, the small diaphragm pump has good sealing performance and is relatively small in size and weight, thereby simplifying the collection device and improving its portability.

[0044] Detection unit 4 includes a pressure sensor 7 and a humidity sensor 8. Pressure sensor 7 is used to measure the internal pressure of the pipeline and can be a mechanical pressure gauge, electronic pressure gauge, vacuum gauge, or other pressure measuring devices. Humidity sensor 8 is used to detect the water vapor partial pressure in the water-containing gas and can be a hygrometer, dew point meter, or other measuring devices.

[0045] A first valve 5 is provided on the pipeline between the diaphragm pump 3 and the detection unit 4 to control the continuous and cessation of the entry of the water-containing gas. A flow controller can also be provided on the pipeline in front of the diaphragm pump 3 to measure the intake volume of the water-containing gas, thereby providing theoretical data for the test experiment.

[0046] The water collection unit 2 is used to collect water isotope samples in the water-containing gas. A second valve 6 is provided on the pipeline between the flexible gas collection container 1 and the water collection unit 2, which is used to control the water in the water-containing gas in the flexible gas collection container 1 to enter the water collection unit 2 and stop entering.

[0047] The water collection unit 2 includes a sealed water collection container and calcium chloride particles disposed within the container. The inlet of the water collection container is connected to the flexible gas collection container 1 via a pipeline (the pipeline is as short as possible). The water collection container of this method can be set to any shape, and the specific volume can be set according to actual needs. Before use, the water collection container must fully desorb water adsorbed on the inner surface, thereby improving the purity of the collected sample. At the same time, 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, which provides good flexibility and improves the applicability of the entire device.

[0048] This embodiment also provides a portable method for collecting water isotope samples in gas, comprising the following steps:

[0049] 1] Fully desorb the water in the flexible gas collection container 1 and the water collection unit 2, and close all valves.

[0050] Place about 20g of calcium chloride into the water collecting container. Before use, fully desorb the water adsorbed on the inner surface of the flexible gas collection container 1 and the water collecting container. At the same time, the water adsorbed in the calcium chloride must also be fully desorbed. The desorption process generally adopts a combination of one or more methods including heating, dry gas purging, and vacuuming. After the water is fully desorbed, the water collecting container is cooled to room temperature and weighed, and the relevant data is recorded for subsequent analysis.

[0051] 2] Expand the flexible gas collection container 1 from its initial state and open the first valve 5.

[0052] Unfold the stored flexible gas collection container 1, which uses an aluminum foil gas sampling bag. A DMT340 dew point meter is used as the humidity sensor, and a pressure transmitter with a range of 200 kPa is used as the pressure sensor. The entire collection device must be leak-tested before use to ensure its tightness.

[0053] 3] Start the diaphragm pump 3 and collect the water-containing gas into the flexible gas collection container 1 through the pipeline. When the pressure in the flexible gas collection container 1 reaches 1.01 times the pressure of the water-containing gas, close the first valve 5 and open the second valve 6. The water-containing gas in the flexible gas collection container 1 enters the water collecting container and is adsorbed by calcium chloride. After standing for about 50 minutes, the dew point meter shows that the water vapor partial pressure in the water-containing gas reaches 0.5 Pa. At this time, close the second valve 6 to complete the collection of water isotope samples in the water-containing gas.

[0054] 4] Remove the water collecting container containing calcium chloride and weigh it. Then, remove and collect all the water isotope samples in the calcium chloride water collector, and then test the hydrogen and oxygen isotope ratios in the water isotope samples.

[0055] In this example, the atmospheric water vapor partial pressure measured using an HMP-7 hygrometer was 2462 Pa, the temperature was approximately 25°C, and the gas volume of the flexible gas collection container 1 was 110.64 L. Based on the ideal gas equation, the mass of water in the water-containing gas was calculated to be approximately 1.9797 g. The mass of calcium chloride increased by 1.9820 g after absorbing water. Taking into account the measurement errors of the water vapor partial pressure and the gas volume (the uncertainty of the humidity measurement is approximately 1%, and the uncertainty of the gas volume is 2%), the collection rate of the water isotope sample is 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 -110.6 and -16.15 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 -110.7 and -16.14 respectively.

[0057] It can be seen from this that the relative deviation between the hydrogen and oxygen isotope ratios of the water isotope samples collected in this embodiment and the hydrogen and oxygen isotope ratios directly measured in the gas is very small, both are within the measurement uncertainty range (the measurement uncertainty of the δ value is approximately 1), and the measurement accuracy is high.

[0058] Example 2

[0059] like Figure 2 As shown, the difference between this embodiment and the first embodiment is that the water collection unit 2 of this embodiment includes a cold trap and a water collection container disposed within the cold trap. The inlet end of the water collection container is connected to the flexible gas collection container 1 via a pipeline (the pipeline is as short as possible). The cold trap temperature is between -273°C and -30°C. The cold trap temperature can also be adjusted as needed to balance the demand for water isotope samples with the cost, avoid waste of cost and energy, and save costs. In this embodiment, the cold trap temperature is set between -200°C and -70°C. At this temperature, the water collection efficiency of the water sample is high and the cost is low. At this temperature, the cold trap can reduce the water vapor partial pressure in the water-containing gas to below 1Pa. When the corresponding water vapor partial pressure in the water-containing gas is greater than 100Pa and 1kPa, respectively, the theoretical collection efficiency of the water isotope sample is greater than 99% and 99.9%, respectively, which is a high collection efficiency.

[0060] Cold traps can be created through a combination of one or more of the following methods: electric refrigeration, semiconductor refrigeration, liquid nitrogen refrigeration, liquid helium refrigeration, and dry ice refrigeration. The water collection container for this method can be configured in any shape, with a volume ranging from a few milliliters to several hundred milliliters, and can also be specifically set according to actual needs. Before use, the water collection container must fully desorb water adsorbed on its inner surface to improve the purity of the collected sample. At the start of water collection, the temperature of the water collection container must reach the cold trap temperature. Furthermore, this method can collect water isotope samples from gases with low water vapor partial pressures (>1Pa), and has a wide range of applications.

[0061] The collection method of this embodiment includes the following steps:

[0062] 1] Fully desorb the water in the flexible gas collection container 1 and the water collection unit 2, and close all valves.

[0063] In this embodiment, the volume of the water collecting container of the water collection unit 2 is approximately 10 mL. Before use, the water adsorbed on the inner surface of the flexible gas collection container 1 and the water collecting container is fully desorbed. Generally, desorption adopts a combination of one or more methods including heating, dry gas purging, and vacuuming. After the water is fully desorbed, the water collecting container is cooled to room temperature and then weighed for the first time and recorded for subsequent analysis.

[0064] 2] Expand the flexible gas collection container 1 from its initial state and open the first valve 5.

[0065] Unfold the flexible gas collection container 1 from its storage state. Before use, the entire collection device must be leak-tested to ensure its tightness. In this embodiment, the flexible container utilizes an aluminum foil gas sampling bag. After unfolding, the first valve 5 is opened, the second valve 6 is closed, and the pressure and humidity of the water-containing gas within the pipeline are recorded using a pressure sensor 7 and a humidity sensor 8, respectively.

[0066] 3] Start the diaphragm pump 3 and collect the water-containing gas into the flexible gas collection container 1 through the pipeline. When the pressure in the flexible gas collection container 1 reaches 1.01 times the pressure of the water-containing gas, close the first valve 5 and open the second valve 6. The water-containing gas in the flexible gas collection container 1 enters the water collecting container in the cold trap, and the water in the water-containing gas enters the water collecting container and is frozen. When the water vapor partial pressure in the water-containing gas measured by the humidity sensor 8 reaches 0.6 Pa, close the second valve 6, and the water in the water-containing gas is collected in the water collecting container, thereby completing the collection of the water isotope sample in the water-containing gas.

[0067] 4] Remove the water collecting container, desorb the water on the outer surface of the water collecting container and cool it to room temperature, then open the second valve 6. After the pressure in the water collecting container is balanced with the atmospheric pressure, perform a second weighing and record it. Finally, based on the collected water isotope sample, measure the hydrogen and oxygen isotope ratio in the sample.

[0068] In this embodiment, an HMP-7 hygrometer was used to measure the atmospheric water vapor partial pressure to be 2325 Pa, the temperature to be approximately 24°C, and the gas volume of the flexible gas collection container 1 to be 108.47 L. Based on the ideal gas equation, the mass of water in the water-containing gas was calculated to be approximately 1.8390 g. The mass of the water collection container increased by 1.8369 g after collecting water, resulting in a calculated water collection efficiency of 99.9%, which is quite high.

[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 δ values ​​of O content) are -110.8 and -16.17 respectively.

[0070] 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 -110.5 and -16.17 respectively.

[0071] It can be seen from this that the relative deviation between the hydrogen and oxygen isotope ratios of the water isotope samples collected based on the collection method of the present invention and the hydrogen and oxygen isotope ratios of water in the gas directly measured is very small, both are within the measurement uncertainty range (the measurement uncertainty of the δ value is about 1), and the measurement accuracy is high.

Claims

1. A portable device for collecting water isotope samples in gas, characterized by: It comprises a flexible gas collection container (1) and a water collection unit (2) connected to the flexible gas collection container (1) via a pipeline; The flexible gas collection container (1) is used to collect water-containing gas, and its initial state is a curled or folded form; the flexible gas collection container (1) is made of elastic material or non-elastic material or a combination of elastic and non-elastic materials, and its internal bearing pressure is 1.0 to 1.2 times the pressure of the water-containing gas; the water collection unit (2) is used to collect water isotope samples in the water-containing gas; A diaphragm pump (3) and a detection unit (4) are sequentially provided on the pipeline at the inlet end of the flexible gas collection container (1), wherein the detection unit (4) is close to the inlet end of the flexible gas collection container (1); the diaphragm pump (3) is used to provide a driving force for the water-containing gas to enter the flexible gas collection container (1); A first valve (5) is provided on the pipeline between the diaphragm pump (3) and the detection unit (4); a second valve (6) is provided on the pipeline between the flexible gas collection container (1) and the water collection unit (2); The detection unit (4) includes a pressure sensor (7) and a humidity sensor (8).

2. The portable device for collecting water isotope samples in gas according to claim 1, characterized in that: The outlet pressure of the diaphragm pump (3) does not exceed 1.2 times the pressure of the water-containing gas.

3. The portable device for collecting water isotope samples in gas according to claim 2, characterized in that: A flow controller is also provided on the pipeline at the front end of the diaphragm pump (3) for testing the intake volume of the water-containing gas.

4. The portable device for collecting water isotope samples in gas according to claim 3, characterized in that: The water collecting unit (2) comprises a sealed 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 flexible gas collecting container (1) via a pipeline.

5. The portable device for collecting water isotope samples in gas according to claim 3, 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 flexible gas collection container (1) via a pipeline, and the temperature of the cold trap is between -273°C and -30°C.

6. The portable device for collecting water isotope samples in gas according to claim 5, 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.

7. A portable method for collecting water isotope samples in gas, characterized in that: The portable device for collecting water isotope samples in gas according to any one of claims 1 to 6 comprises the following steps: 1] Fully desorb the water in the flexible gas collection container (1) and the water collection unit (2), and close all valves; 2] Expand the flexible gas collection container (1) from its initial state and open the first valve (5); 3] Start the diaphragm pump (3) to collect the water-containing gas into the flexible gas collection container (1). When the pressure in the flexible gas collection container (1) reaches 1.0 to 1.2 times the pressure of the water-containing gas, close the first valve (5) and open the second valve (6). The water in the water-containing gas in the flexible gas collection container (1) diffuses into the water collection unit (2) and is collected. 4] When the detection unit (4) shows that the water vapor partial pressure in the water-containing gas in the flexible gas collection container (1) is lower than 1 Pa, the second valve (6) is closed, and the collection of the water isotope sample is completed.

8. The portable method for collecting water isotope samples in gas according to claim 7, characterized in that: In step 1], the water is fully desorbed by desorbing the water adsorbed on the inner wall of the water collecting container and the flexible gas collecting container (1), and the desorption adopts a combination of one or more methods of heating, dry gas purging, and vacuuming; when the water collecting unit (2) adopts calcium chloride adsorption and collection, the water adsorbed by the calcium chloride needs to be desorbed, and then the water collecting container is cooled to room temperature.

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