A walkabout gas collection system for soil gas

Abstract

The present application relates to the technical field of gas sampling, in particular to a walk-around gas sampling system for soil gas collection, comprising: a gas sampling container, comprising any one or more of a first container, a second container and a third container, the first container comprising a steel cylinder for storing a gas sample at a first pressure, the second container comprising a flexible gas bag for storing a gas sample at a second pressure, the second pressure being less than the first pressure, and the third container comprising a gas extraction pipeline forming a soil sample collection container with a soil layer to be sampled.The walk-around gas sampling system for soil gas collection can sample through three gas sampling modes of the gas cylinder, the flexible gas bag and the gas extraction pipeline, can adapt to different sampling points, and can simultaneously detect the gas samples collected from the sampling points at the same standard, so that the gas sample components of the current sampling point can be more effectively restored.

Description

Technical Field

[0001] This invention relates to the field of gas sampling technology, and more specifically to a mobile gas sampling system for soil gas collection. Background Technology

[0002] Because hydrogen and helium molecules are small, lightweight, and easily diffused, their formation conditions are demanding, significantly increasing the difficulty of exploration. However, the same easy diffusion of hydrogen and helium molecules makes soil gas detection an effective method for tracing localized enrichment of underground hydrogen and helium. Methane and carbon dioxide, as potential associated gases of hydrogen and helium, are also targets for soil gas detection; their content and isotopic characteristics help analyze the origin of hydrogen and helium.

[0003] For soil gas sampling in the field, analysis is usually performed in a laboratory using gas detectors after sampling. However, because hydrogen and helium are highly volatile, long-distance transportation of samples collected in sampling bags or cylinders to the laboratory for measurement can lead to gas loss and inaccurate results. Furthermore, to obtain large amounts of data, large-scale sampling is often conducted over large areas. This requires significant manpower (sampling, collection, transportation, and testing), material resources (sampling bags, cylinders, vehicles, etc.), and financial resources (long-term personnel costs, gas transportation costs, laboratory equipment usage costs, etc.). Therefore, it is impossible to send all samples to the laboratory. Summary of the Invention

[0004] To address the technical problems existing in existing soil gas harvesting technologies, the first aspect of this invention proposes a mobile soil gas harvesting system, comprising:

[0005] A gas sampling container includes any one or more of a first container, a second container, and a third container. The first container includes a steel cylinder for storing a gas sample at a first pressure. The second container includes a flexible gas bag for storing a gas sample at a second pressure, which is less than the first pressure. The third container includes an extraction pipe, which, together with the soil layer to be sampled, constitutes a soil sample sampling container.

[0006] The pretreatment system includes a pressure regulating component and a flow regulating component. The pretreatment system has three injection paths, which are respectively used to connect to the first container, the second container and the third container.

[0007] The gas analysis system is used to perform chromatographic, mass spectrometric, and carbon dioxide isotope analysis on the collected gas samples and obtain the concentrations of hydrogen and helium, as well as the concentration and carbon dioxide isotope ratio in the current gas sample.

[0008] The first container is connected to the first injection path, the second container is connected to the second injection path, and the third container is connected to the third injection path. The pressure regulating component includes a suction device and a pressure regulating valve. The first injection path is connected to the input end of the pressure regulating valve. The input end of the suction device is connected to the second and third injection paths. The output end of the suction device is connected to the input end of the pressure regulating valve. The output end of the pressure regulating valve is connected to the flow regulating component, so that the gas sample from the first, second, or third container enters the gas analysis system at a predetermined pressure and flow rate.

[0009] Preferably, the first container, the second container, or the third container is detachably connected to the sample introduction path of the pretreatment system.

[0010] Preferably, the input end of the gas extraction device is provided with a first gas selector. The first gas selector is provided with a first input port and a second input port. The first input port is connected to the second container through a flow regulating valve, and the second input port is connected to the third container. The flow regulating valve and the first input port of the first gas selector constitute a second injection path, and the second input port of the first gas selector constitutes a third injection path.

[0011] Preferably, the output end of the gas extraction device is provided with a second gas selector, the second selector is provided with a third input port and a fourth input port, the third input port of the second selector is connected to the output end of the gas extraction device, and the fourth input port of the second selector constitutes a first sample injection path.

[0012] Preferably, the output end of the second selector is provided with a gas-liquid separator, and the output end of the gas-liquid separator is provided with a third gas selector, which is located at the input end of the pressure regulating valve.

[0013] Preferably, the gas pressure output from the pretreatment system to the gas analysis system is 0.1 MPa.

[0014] Preferably, the gas path capacity between each injection path and the gas analysis system in the pretreatment system is A, and the smallest capacity among the first container, the second container, or the third container is B, where B ≥ 10A.

[0015] Preferably, the capacity of the flexible gas bag is 200-400ml, the flexible gas bag includes an aluminum foil gas bag, the length of the gas extraction pipe is 15-25m, the inner diameter of the gas extraction pipe is 6mm, and the gas path capacity between each sample injection path and the gas analysis system in the pretreatment system is less than 30ml.

[0016] Preferably, the data acquisition system is integrated into a mobile platform, which includes a wheeled chassis, and the air extraction device is detachably connected to the mobile platform.

[0017] Preferably, the gas analysis system includes a chromatography system, a mass spectrometry system, a spectral system, a data acquisition system, and a tail gas treatment system. The mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller. The turbomolecular pump is used to vent the gas in the pipeline of the gas analysis system, and the electronic pressure controller is used to fill the pipeline of the gas analysis system or the pretreatment system with nitrogen.

[0018] Preferably, after each gas detection, the pipelines in the pretreatment system and the gas analysis system are emptied and filled with nitrogen.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] The mobile gas sampling system for soil gas collection proposed in this invention can be sampled using three methods: gas cylinders, flexible gas bags, and extraction pipelines. Therefore, when the mobile vehicle is driven to a field testing point, if it is very close to the testing point, soil gas can be sampled directly through the pipeline, and the gas will be transported to the mass spectrometer for detection through the pipeline. In some situations with poor road conditions, such as when the field testing point is far from the navigable road, the mobile vehicle cannot drive to the vicinity of the target point, and the pipeline cannot reach the target point, soil gas can be sampled using extraction equipment and gas sampling bags, and immediately sent to the mobile vehicle to connect to the gas inlet port of the mass spectrometer for detection. In addition, for some special oil and gas plant areas, where the gas pressure in the well is high during sampling, it is necessary to first sample using a gas cylinder, and then connect the gas cylinder to the pipeline system of the mobile vehicle, and then transport the gas to the mass spectrometer for detection through the pipeline.

[0021] Therefore, the mobile gas sampling system for soil gas collection proposed in this invention can adapt to different sampling points and simultaneously detect the gas samples collected from these sampling points on-site using the same standards, which can more effectively restore the composition of the gas sample at the current sampling point. Attached Figure Description

[0022] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0023] Figure 1 This is a schematic diagram of the mobile gas collection system for soil gas collection shown in this invention.

[0024] Figure 2This is a schematic diagram of the structure of the mobile gas collection system for soil gas collection shown in this invention;

[0025] Figure 3 This is a schematic diagram of the sampling path of the first container shown in this invention;

[0026] Figure 4 This is a schematic diagram of the sampling path of the second container shown in this invention;

[0027] Figure 5 This is a schematic diagram of the sampling path of the third container shown in this invention;

[0028] Figure 6 This is a schematic diagram of the processing path for spectral analysis of gas samples as shown in this invention;

[0029] Figure 7 This is a schematic diagram of the pre-column separation process for gas samples as shown in this invention.

[0030] Figure 8 This is a schematic diagram of the processing path for mass spectrometry analysis of gas samples as shown in this invention. Detailed Implementation

[0031] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0032] For soil gas collection, there may be different sampling scenarios, such as areas where equipment can or cannot be approached, or special oil and gas plant areas. For gases such as hydrogen and helium, which are extremely easy to dissipate, distributed sampling followed by centralized laboratory analysis and detection cannot accurately reflect the gas concentration. Therefore, it is essential to achieve real-time on-site sampling and analysis.

[0033] Sampling scenarios on-site are generally divided into three categories. The first category is detection points that can be reached by mobile equipment. These detection points can be directly transported to the mass spectrometer on the mobile equipment via pipeline for detection. The second category is detection points that cannot be reached by mobile equipment. These detection points can be sampled using gas sampling bags and then detected by the mass spectrometer on the mobile equipment in a very short time. The third category is sampling wells in oil and gas plant areas. The gas pressure inside the sampling wells is high, so steel cylinders can be used as sampling containers, and then detected by the mass spectrometer on the mobile equipment in a very short time.

[0034] Therefore, the field acquisition system proposed in this application can perform real-time field sampling and detection of sampling points in the above three types of sampling areas, and ensure that each method is performed with the same detection standard to avoid result deviations caused by interference factors.

[0035] like Figure 1 and Figure 2As shown, the first aspect of the present invention provides a mobile gas collection system for soil gas collection, including a gas collection container 10, a pretreatment system 20 and a gas analysis system 30, wherein the gas collection container 10 includes any one or more of a first container 11, a second container 12 and a third container 13.

[0036] Understandably, appropriate sampling containers are selected based on the distribution of sampling points in the sampling area. In order to ensure the timeliness of sampling and monitoring, the next sampling is carried out after one monitoring is completed. During sampling and testing, it is preferable to sample and test the detection points in the adjacent area in sequence.

[0037] In a preferred embodiment, the data acquisition system is integrated into a mobile platform, which includes a wheeled chassis, such as a manned or unmanned wheeled chassis, capable of traveling on flat roads to facilitate transfer to the target sampling point or a location close to the sampling point.

[0038] Optionally, if the sampling area is rectangular and several sampling points within the rectangular area are distributed in a matrix, sampling and detection of each sampling point should be carried out sequentially according to a serpentine trajectory.

[0039] Optionally, if roads are distributed in the sampling area, sampling and testing should be prioritized for sampling points near the roads.

[0040] In an optional embodiment, the first container 11 includes a steel cylinder for storing a gas sample at a first pressure. The second container 12 includes a flexible gas bag for storing a gas sample at a second pressure, which is lower than the first pressure. The third container 13 includes an extraction pipe, which, together with the soil layer to be sampled, constitutes a soil sample collection container.

[0041] The first container 11 is used to collect gas samples from sampling wells in the oil and gas plant area. After sampling, the pressure inside the cylinder is usually 1 MPa to 4 MPa. The second container 12 is used to sample and collect samples from sampling points far from the road. The third container 13 is used to collect and detect samples from sampling points close to the road in real time.

[0042] It should be understood that the distance between the sampling point and the equipment, as well as the length of the extraction pipeline, determines whether to use an extraction pipeline or a flexible gas bag for sampling. Typically, the length of the extraction pipeline is 15–25 m. Therefore, for sampling points more than 25 m from the equipment, a flexible gas bag should be used for sampling, and the collected sample should be promptly transferred to the equipment's sampling interface for on-site analysis. For sampling points within 25 m of the equipment, an extraction pipeline should be used for real-time sampling, and the collected gas sample should be directly connected to the equipment's sampling interface for on-site analysis. When the sampling point is a high-pressure gas sample from a sampling well, a gas cylinder should be used for sampling, and the sample should be promptly transferred to the equipment's sampling interface for on-site analysis.

[0043] Furthermore, the pretreatment system 20 is designed to provide appropriate pressure and flow rate for each gas sample before it enters the gas analysis system 30. Therefore, the pretreatment system 20 includes a pressure regulating component and a flow regulating component 23, and the pretreatment system is provided with three sample inlet paths for connecting to the first container 11, the second container 12 and the third container 13, respectively.

[0044] Because the gas content, pressure, and uniformity of the first container 11, the second container 12, and the third container 13 are different, the gas samples of each container need to be processed differently.

[0045] The first container 11 is connected to the first injection path, the second container 12 is connected to the second injection path, and the third container 13 is connected to the third injection path.

[0046] Optionally, the pressure regulating component includes a suction device 21 and a pressure regulating valve 22. The first injection path is connected to the input end of the pressure regulating valve 22, the input end of the suction device 21 is connected to the second injection path and the third injection path, the output end of the suction device 21 is connected to the input end of the pressure regulating valve 22, and the output end of the pressure regulating valve 22 is connected to the flow regulating component 23.

[0047] Thus, the gas samples entering through the second and third injection paths are pressurized by the pumping device 21 to reach a preset pressure. Before entering the gas analysis system 30, the input flow rate is controlled by the flow regulating component 23, so that the gas samples from the first container 11, the second container 12, or the third container 13 enter the gas analysis system 30 at a predetermined pressure and flow rate.

[0048] Because the flexible gas bag has a small gas volume, in order to ensure that the gas volume entering the second injection path after being pressurized by the gas extraction device 21 is uniform, in an optional embodiment, the input end of the gas extraction device 21 is provided with a first gas selector 24. The first gas selector 24 is provided with a first input port and a second input port. The first input port is connected to the second container 12 through the flow regulating valve 121, and the second input port is connected to the third container 13. The second injection path is formed by the flow regulating valve 121 and the first input port of the first gas selector 24, and the third injection path is formed by the second input port of the first gas selector 24.

[0049] Thus, a flow regulating valve 121 is installed at the first input port of the first gas selector 24 to control the amount of gas entering the suction device 21 from the flexible gas bag. When the output pressure is at a preset value, the input and output flow rates are also at preset values. Since the inner diameter and length of the suction pipe are fixed, which constrains the maximum amount of air intake, it is not necessary to install a flow regulating valve in the suction pipe.

[0050] In an optional embodiment, the output end of the pumping device 21 is provided with a second gas selector 25. The second selector has a third input port and a fourth input port. The third input port of the second selector is connected to the output end of the pumping device 21, and the fourth input port of the second selector forms a first sample injection path. The output end of the second selector is provided with a gas-liquid separator 27, and the output end of the gas-liquid separator 27 is provided with a third gas selector 26, which is located at the input end of the pressure regulating valve 22.

[0051] Thus, since water is easily liquefied after the gas sample is pressurized by the gas extraction device 21, by setting up the gas-liquid separation tank 27, the gas sample can be separated into gas and liquid after passing through the gas-liquid separation tank 27. The gas sample after gas-liquid separation is conducive to obtaining better test results.

[0052] In specific embodiments, such as Figure 3 As shown, taking the injection of a gas cylinder as an example, the gas cylinder is connected to the fourth input port of the second gas selector 25. The gas in the gas cylinder enters the second gas selector 25 through the first injection path, and then enters the gas-liquid separator 27. After passing through the gas-liquid separator 27, gas-liquid separation is achieved, and then the gas enters the third gas selector 26. After passing through the pressure regulating valve 22 and the flow regulating component 23, the gas flow entering the ten-way injection valve 31 is a constant pressure and constant flow gas sample.

[0053] In specific embodiments, such as Figure 4 As shown, taking a flexible gas bag as an example, the flexible gas bag is connected to the flow regulating valve 121. Through the pressurization action of the suction device 21, the gas sample in the flexible gas bag passes through the flow regulating valve 121, the first gas selector 24 and the suction device 21 in sequence. After being pressurized by the suction device 21, it enters the second gas selector 25 and the gas-liquid separator 27. After passing through the gas-liquid separator 27, gas-liquid separation is achieved, and then it enters the third gas selector 26. Finally, through the pressure regulating valve 22 and the flow regulating component 23, the gas flow entering the ten-way sample inlet valve 31 is a constant pressure and constant flow gas sample.

[0054] In an optional embodiment, the gas pressure output by the pretreatment system 20 to the gas analysis system 30 is 0.1 MPa.

[0055] Optionally, the suction device 21 is detachably connected to the movable platform. When sampling with a flexible air bag, the suction device 21 can be detached and transferred to the sampling point by the sampling personnel. At the sampling point, a drilling tool (probing metal tube) is used to drill an air channel of a predetermined size, the probing tool is placed in the air channel, and the suction device 21 is connected between the air channel and the flexible air bag to draw the air sample from the air channel into the flexible air bag.

[0056] In specific embodiments, such as Figure 5As shown, taking the gas extraction pipeline as an example, the two ends of the gas extraction pipeline are connected to the gas channel and the first gas selector 24, respectively. Through the gas extraction action of the gas extraction device 21, the gas sample in the gas channel enters the first gas selector 24 and the gas extraction device 21 through the gas extraction pipeline. After being pressurized by the gas extraction device 21, it enters the second gas selector 25 and the gas-liquid separator 27. After passing through the gas-liquid separator 27, gas-liquid separation is achieved, and then it enters the third gas selector 26. Finally, through the pressure stabilizing valve 22 and the flow regulating component 23, the gas flow entering the ten-way injection valve 31 is made into a constant pressure and constant flow gas sample.

[0057] It should be understood that, since the first container 11, the second container 12, or the third container 13 needs to be frequently disassembled from the pipeline during sampling and testing, it is preferable that the first container 11, the second container 12, or the third container 13 be detachably connected to the sample inlet path of the pretreatment system. For example, quick-release connectors can be used.

[0058] In the above embodiments, in order to avoid the residual gas in the fixed pipes of the device from affecting the gas sample, the gas path capacity between each sample inlet path in the pretreatment system 20 and the gas analysis system 30 is A, and the smallest capacity among the first container 11, the second container 12 or the third container 13 is B, wherein B≥10A.

[0059] Optionally, the capacity of the flexible gas bag is 200-400ml, the flexible gas bag includes an aluminum foil gas bag, the length of the gas extraction pipe is 15-25m, the inner diameter of the gas extraction pipe is 6mm, and the gas path capacity between each sample injection path in the pretreatment system 20 and the gas analysis system 30 is less than 30ml.

[0060] Thus, during detection, the upstream gas is discarded and not detected, that is, the gas path between each sample introduction path in the pretreatment system 20 and the gas analysis system 30 is emptied.

[0061] In the above embodiments, the gas analysis system 30 is used to perform chromatographic, mass spectrometric and carbon dioxide isotope analysis on the collected gas sample, and to obtain the concentrations of hydrogen and helium, as well as the concentration and carbon dioxide isotope ratio in the current gas sample.

[0062] Specifically, the gas analysis system 30 includes a chromatography system, a mass spectrometry system, a spectral system, a data acquisition system, and a tail gas treatment system. It effectively separates different components in the mixture, determines the sample composition and purity, and identifies the target substances. The chromatography system determines the concentration of specific components in the sample by measuring parameters such as peak area or peak height, and compares this concentration with known standards or databases to sensitively detect trace amounts of the target substances in the sample. The mass spectrometry system includes a quadrupole system, ion source, detector, vacuum system, circuit control system, and hydrogen-helium detection software. The spectral system features a precisely temperature-controlled spectral measurement chamber, maintaining a gas-sealed environment throughout the entire analysis system. Internally, it contains components such as a quantum cascade laser, laser temperature controller, infrared laser detector, and hollow absorption chamber. The absorption chamber, approximately 1 meter long, flows into a hollow waveguide through a 1 / 16-inch outer diameter capillary tube, where infrared laser spectroscopy is used to detect the gas components flowing through it. The data acquisition system includes a computer (pre-installed with Windows), a high-speed data acquisition card, and power supplies for each instrument. The data acquisition card has three SMA signal lines at its fixed rear end: a trigger connector for the data acquisition card, a connection line for the sample gas detector, and a connection line for the reference gas detector. These lines are used to connect the spectrometer and the laser driver. The laser driver in the instrument drives the spectrometer's laser, generating the modulation waveform and illuminating the laser.

[0063] The mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller. The turbomolecular pump is used to purge the gas in the pipeline of the gas analysis system 30, and the electronic pressure controller is used to fill the pipeline of the gas analysis system 30 or the pretreatment system 20 with nitrogen.

[0064] The electronic pressure controller includes a nitrogen gas source with multiple outputs, one of which can be connected to the inlet of the pretreatment system 20 for flushing the pipes in the pretreatment system 20 and the gas analysis system 30. The turbomolecular pump can simultaneously pump out the residual exhaust gas in the pipes.

[0065] Preferably, after each gas detection, the pipes in the pretreatment system 20 and the gas analysis system 30 are purged and filled with nitrogen. This ensures that the results of the gas detected each time are relatively accurate.

[0066] like Figure 1As shown, in an optional embodiment, taking the use of gas cylinders for collection and testing as an example: the gas cylinder gas obtained directly from the wellhead of the gas production plant typically has an internal pressure of 1 MPa to 4 MPa. The gas cylinder is connected to the fourth input port of the second gas selector 25. After purification and pressure / flow regulation by the pretreatment system 20, the gas passes through a chromatographic separation system to separate the required hydrogen, helium, methane, carbon dioxide, etc., and transmits them to the mass spectrometry system. The remaining unwanted gases are discharged through a tail gas treatment system, which can be selected from activated carbon adsorption, catalytic oxidation, etc., to effectively... To remove harmful substances from exhaust gases and improve emission quality, the mass spectrometry system uses a vacuum gauge to monitor the pressure of hydrogen, helium, methane, and carbon dioxide to prevent the mass spectrometer from operating at excessively high pressures, ensuring optimal gas analysis sensitivity. Other gases are partially measured using multipliers to measure extremely small ion currents or extremely high measurement speeds, increasing instrument sensitivity and reducing partial pressure. The data analyzed by the mass spectrometry system is then transmitted to a computer terminal for processing. The remaining gases are processed using turbomolecular pumps to optimize residual gas spectra and background pressure conditions. Before exhaust gas treatment, a separate pump is typically needed to evacuate the measurement system. Small units with turbomolecular pumps and diaphragm pumps can be used for this purpose. Finally, the tested gases undergo exhaust gas treatment to prevent environmental pollution. The mass spectrometry system also includes an electronic pressure controller that can charge the pipeline with an appropriate amount of nitrogen. After each detection, the pipeline is flushed and exhaust gas is treated to prevent the introduction of impurities and improve the accuracy of the detection results.

[0067] One method of using the aforementioned mobile gas collection system for soil gas harvesting is as follows:

[0068] Based on sampling requirements, select suitable sampling points in the field and move the mobile gas collection system used for soil gas collection to a location close to the sampling point;

[0069] The selected sampling points include a first sampling point, a second sampling point, and a third sampling point. The sampling area is defined as containing roads. The sampling wells contained in the sampling area are the first sampling points. The sampling points in the area far from the road (more than 25m away from the sampling point) are the second sampling points. The sampling points in the area near the road (less than 25m away from the sampling point) are the third sampling points.

[0070] Next, gas sampling is performed on the sampling points using the first container 11, the second container 12 and / or the third container 13. The first sampling point is sampled using the first container 11, the second sampling point is sampled using the second container 12, and the third sampling point is sampled using the third container 13. The first container 11 and the second container 12 are connected to the pre-processing system 20 after sampling, and the third container 13 is connected to the pre-processing system 20 before sampling.

[0071] Specifically, for sampling at the first sampling point, the first container 11 is connected to the sampling well, and the gas sample is forced into the first container 11 by the pressure of the sampling well. For sampling at the second sampling point, a gas channel of a predetermined size is drilled at the sampling point using a drilling tool, and a probe is placed inside the gas channel. An air extraction device 21 is connected between the gas channel and the second container 12 to extract the gas sample from the gas channel into the second container 12. For sampling at the third sampling point, a gas channel of a predetermined size (approximately 2 cm in diameter and approximately 1 m in length) is drilled at the sampling point using a drilling tool, and a probe is placed inside the gas channel. The two ends of the third container 13 are connected to the gas channel and the pretreatment system 20, respectively.

[0072] Furthermore, the gas sample from the first container 11, the second container 12, or the third container 13 is introduced into the gas analysis system 30 at a predetermined pressure and flow rate through the pretreatment system 20 for gas sample analysis.

[0073] It should be understood that during the sampling process of the third container, due to the long length of the pipeline, the gas sample enters the mass spectrometry system unevenly when it is drawn in. Therefore, the concentration of the gas sample at different detection times should be taken into account during detection.

[0074] Specifically, let V be the volume of the pipe and V be the volume of the underground borehole. 管 (V 管 V can be calculated using the pipe diameter R and the drilling depth h, i.e. 管 =1 / 4πR 2 *h), the pumping rate of the pumping device is Q, in ml / min. The delay time T from the sample gas to the detector is calculated based on the pumping rate Q and the volume V of the pipeline, in seconds. After unit alignment, the calculation is performed: T = V / Q, that is, from the start of pumping, after a delay of T seconds, detection begins. For any time tx after the start of detection, the concentration C of hydrogen or helium is... h2 x or C He x can be expressed by the following formula:

[0075]

[0076] Where t0 is the time of the first peak, t N For the time of the last peak, C t Let C be the concentration of hydrogen or helium at time t. h2 x or C He x, with a test interval of 1 minute per test.

[0077] Therefore, the above formula can be used to obtain the concentration corresponding to each detection data, that is, the correspondence between the concentration and quantity of hydrogen or helium.

[0078] Thus, the detection results at different times correspond to the detection results at different concentrations. Among them, the concentration peak is closer to the original concentration of hydrogen and helium in the gas sample.

[0079] Since gases are compressible, the pressure and flow rate of the sample gas must be maintained to ensure a stable amount of sample gas entering the system each time. Therefore, the gas samples in the first container 11, the second container 12, or the third container 13 are all subject to pressure and flow stabilization control to ensure the flow rate of the sample gas.

[0080] like Figure 6 As shown, after the gas has undergone pressure and flow stabilization, it enters the ten-way injection valve 31 for the detection of hydrogen and helium concentrations and carbon dioxide concentrations and their isotopes. The gas path for detecting hydrogen and helium concentrations is shown by the red line in the figure, and the gas path for detecting carbon dioxide concentrations and their isotopes is shown by the blue line.

[0081] Specifically, the gases used for hydrogen and helium concentration detection enter the chromatographic system through the ten-way injection valve 31 via the cut valve for pre-separation. First, air and the sample that will elute later are directly discharged from the system in the pre-column 33. Then, the sample processed by the pre-column 33 mainly contains hydrogen, helium and a small amount of air. At this point, it enters the first separation column 36 for further separation. After the hydrogen and helium enter the second separation column 37, the remaining air is discharged from the system.

[0082] After hydrogen and helium are separated from the second separation column 37, they enter the mass spectrometry system and are separated using a quadrupole. The mass number data with M / Z=2 and M / Z=4 are output respectively, thereby obtaining the concentrations of hydrogen and helium.

[0083] Specifically, the device used to measure carbon dioxide concentration and isotopes has a measurement range of only 300ppm to 2000ppm. On the one hand, its measurement range is relatively small. Therefore, a dilution module is added to the system. By fixing the flow rate of the sample gas, such as 50sccm, zero-level air 38 is added at the end for dilution, thereby widening the measurement range and ensuring that the instrument can measure 300ppm to 20000ppm.

[0084] Specifically, such as Figure 6 As shown, taking a gas sample from a steel cylinder as an example, the gas sample enters the gas-liquid separator 27 through the second gas selector 25 and then enters the inlet. After exiting the inlet, it enters the third gas selector 26 and then enters the pressure regulating valve 22 → flow regulating component 23 → port 9 of the ten-way injection valve 31 → quantitative loop 32 → port 1 → port 0 and exits into the dilution and mixing chamber 35 of the carbon dioxide concentration and isotope detector → spectral analysis (shown by the blue line).

[0085] like Figure 7As shown, the ten-way injection valve 31 is opened, and the nitrogen gas in the electronic pressure controller 39 enters the ten-way injection valve 31 through port 7 → port 8 → quantitative loop 32 (carrying the gas in the quantitative loop of the previous step) → port 1 → port 2 → pre-column 33 → port 6 → port 5 → first separation column 36 → port 5 of the six-way switching valve 34 → port 4 → second separation column 37 → mass spectrometry analysis (shown by the red line).

[0086] The main function of this step is to carry the sample in the quantitative loop 32 into the mass spectrometer separation system for separation in the pre-column 33. Since the velocity of helium and hydrogen is greater than that of other components such as air, the ten-way injection valve 31 is immediately closed after all the helium and hydrogen have come out of the pre-column 33 and entered the first separation column 36.

[0087] like Figure 8 As shown, after the separation in pre-column 33 is completed, hydrogen, helium, and a small amount of oxygen and nitrogen enter the first separation column 36. Nitrogen gas, output from the electronic pressure controller 39, flows from port 4 → port 5 → first separation column 36 → port 5 of the six-way switching valve 34 → port 4 → second separation column 37 → mass spectrometer. When hydrogen and helium have completely entered separation column 2 from separation column 1, oxygen and nitrogen remain in separation column 1. At this point, the six-way switching valve 34 opens, creating the following gas path.

[0088] In this state, the nitrogen gas from the electronic pressure controller 39 enters port 3 → port 4 of the six-way switching valve 34 → the second separation column 37 → mass spectrometer, completing the mass spectrometry detection of hydrogen and helium gas. Simultaneously, the oxygen and nitrogen gases in the first separation column 36 are carried by the nitrogen gas from the middle path of the electronic pressure controller 39 and continue to be vented through port 5 → port 6 of the six-way switching valve 34.

[0089] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A mobile gas collection system for soil gas harvesting, characterized in that, include: The gas collection container (10) includes a first container (11), a second container (12) and a third container (13). The first container (11) includes a steel cylinder for storing a gas sample at a first pressure. The second container (12) includes a flexible gas bag for storing a gas sample at a second pressure, which is less than the first pressure. The third container (13) includes an extraction pipe, which together with the soil layer to be sampled constitutes a soil sample collection container. The pretreatment system (20) includes a pressure regulating component and a flow regulating component (23). The pretreatment system has three injection paths, which are respectively used to connect to the first container (11), the second container (12) and the third container (13). The gas analysis system (30) is used to perform chromatographic, mass spectrometric and carbon dioxide isotope analysis on the collected gas sample and to obtain the concentration of hydrogen and helium, as well as the concentration of carbon dioxide and the carbon dioxide isotope ratio in the current gas sample. Wherein, the first container (11) is connected to the first injection path, the second container (12) is connected to the second injection path, the third container (13) is connected to the third injection path, the pressure regulating component includes a pumping device (21) and a pressure regulating valve (22), the first injection path is connected to the input end of the pressure regulating valve (22), the input end of the pumping device (21) is connected to the second and third injection paths, the output end of the pumping device (21) is connected to the input end of the pressure regulating valve (22), and the output end of the pressure regulating valve (22) is connected to the flow regulating component (23), so that the gas sample from the first container (11), the second container (12), or the third container (13) enters the gas analysis system (30) at a predetermined pressure and flow rate; The input end of the gas extraction device (21) is provided with a first gas selector (24). The first gas selector (24) is provided with a first input port and a second input port. The first input port is connected to the second container (12) through a flow regulating valve (121), and the second input port is connected to the third container (13). The flow regulating valve (121) and the first input port of the first gas selector (24) constitute a second injection path, and the second input port of the first gas selector (24) constitutes a third injection path. The output end of the gas extraction device (21) is provided with a second gas selector (25). The second gas selector is provided with a third input port and a fourth input port. The third input port of the second gas selector is connected to the output end of the gas extraction device (21), and the fourth input port of the second gas selector constitutes the first sample injection path.

2. The mobile gas collection system for soil gas harvesting according to claim 1, characterized in that, The first container (11), the second container (12), or the third container (13) is detachably connected to the sample injection path of the pretreatment system.

3. The mobile gas collection system for soil gas harvesting according to claim 1, characterized in that, The output end of the second gas selector is provided with a gas-liquid separator (27), and the output end of the gas-liquid separator (27) is provided with a third gas selector (26), which is located at the input end of the pressure regulating valve (22).

4. The mobile gas collection system for soil gas harvesting according to claim 1, characterized in that, The gas path capacity between each injection path in the pretreatment system (20) and the gas analysis system (30) is A, and the smallest capacity among the first container (11), the second container (12) or the third container (13) is B, where B ≥ 10A.

5. The mobile gas collection system for soil gas harvesting according to claim 1, characterized in that, The capacity of the flexible gas bag is 200~400ml, the flexible gas bag includes an aluminum foil gas bag, the length of the gas extraction pipe is 15~25m, the inner diameter of the gas extraction pipe is 6mm, and the gas path capacity between each sample injection path in the pretreatment system (20) and the gas analysis system (30) is less than 30ml.

6. The mobile gas collection system for soil gas harvesting according to claim 1, characterized in that, The data acquisition system is integrated into a mobile platform, which includes a wheeled chassis, and the air extraction device (21) is detachably connected to the mobile platform.

7. The mobile gas collection system for soil gas harvesting according to any one of claims 1-6, characterized in that, The gas analysis system (30) includes a chromatography system, a mass spectrometry system, a spectral system, a data acquisition system, and a tail gas treatment system. The mass spectrometry system is equipped with an independent turbomolecular pump and an electronic pressure controller. The turbomolecular pump is used to vent the gas in the pipeline of the gas analysis system (30), and the electronic pressure controller is used to fill the pipeline of the gas analysis system (30) or the pretreatment system (20) with nitrogen.

8. The mobile gas collection system for soil gas harvesting according to claim 7, characterized in that, After each gas detection, the pipes in the pretreatment system (20) and the gas analysis system (30) are emptied and filled with nitrogen.

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