A portable helium analyzer and detection method thereof

Abstract

The present invention relates to a portable helium analyzer and a detection method thereof. The portable helium analyzer comprises a shell, on which a display unit, a key unit, an air inlet and an air outlet are arranged, and a battery and a main control circuit and a three-way solenoid valve, a chromatographic module, a thermal conductivity detector, a gas sampling pump, and a flow stabilization module respectively connected to the main control circuit are arranged in the shell. The air inlet, the three-way solenoid valve, the chromatographic module, the measuring cell of the thermal conductivity detector, the gas sampling pump, the flow stabilization module and the air outlet are connected to form an air path, and the air inlet, the three-way solenoid valve, the reference cell of the thermal conductivity detector, the gas sampling pump, the flow stabilization module and the air outlet are connected to form another air path. During measurement, the resistance change signal of the reference electrode is first captured, and then the resistance change signal of the first T seconds of the measuring electrode is captured, and the differential pressure signal is processed, and then the helium concentration is obtained by calculation, and displayed and stored. The present invention does not require carrier gas, has a wide detection range, high sensitivity, small size, light weight, and is easy to carry.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection and analysis, in particular to a portable helium analyzer and a detection method thereof, which are used in the fields of environmental protection, geological exploration, earthquake prediction, precision manufacturing, etc. Background Art

[0002] Helium is a rare gas that is abundant in the universe because it is a product of hydrogen nuclear fusion reactions on the sun or planets, but it is very rare on Earth and mainly exists in the atmosphere, rocks and natural gas. Helium is a byproduct of oil and gas and has no direct connection with the formation of oil and gas, but its unique physical and chemical properties cause it to be enriched in oil and gas reservoirs or to form independent reservoirs. Currently, 94% of the world's helium production is extracted from natural gas. The diffusion coefficient of helium is generally less than (3-5)×10cm 2 / s, is an inert gas with strong diffusion in most substances, so it participates in long-distance migration and accumulation together with water, oil, natural gas and atmosphere. Therefore, the abnormal helium content on the surface has a certain oil and gas indication significance. At the same time, since helium is not a gas released by organisms, but a gas deep in the crust, the abnormal helium content caused by the migration and movement of helium in the fracture indicates the occurrence of crustal activity and has the possibility of earthquake prediction.

[0003] The common helium concentration analysis is carried out by gas chromatography or mass spectrometer. Mass spectrometers are mostly used for industrial leak detection, with a narrow detection range and low resolution. At the same time, mass spectrometer modules are mostly imported, and most research and development focuses on the integration and functional optimization of equipment. Gas chromatography requires high-purity argon to accurately analyze the concentration of helium, so it is more limited in scope and application, especially for portable or mobile helium analyzers used for field flow observation. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a portable helium analyzer for flow observation and analysis and a detection method thereof, which has a wide detection range and high sensitivity, does not require the use of high-purity gas as a carrier gas, has a small size and low power consumption, is particularly suitable for field flow observation, is easy to carry, and is light in weight, and can be used for fault, fracture zone, and geological gas reservoir survey.

[0005] The above technical problems of the present invention are mainly solved by the following technical solutions: a portable helium analyzer of the present invention comprises a portable shell, a display unit, a key unit, an air inlet and an air outlet are arranged on the shell, a three-way solenoid valve, a chromatographic module, a thermal conductivity detector, a gas sampling pump, a main control circuit and a battery for powering the entire portable helium analyzer are arranged in the shell; the air inlet is connected to the common port of the three-way solenoid valve, the first air outlet of the three-way solenoid valve is connected to the air inlet of the measuring cell of the thermal conductivity detector through the chromatographic module, the second air outlet of the three-way solenoid valve is connected to the air inlet of the reference cell of the thermal conductivity detector, the air outlet of the thermal conductivity detector is connected to the air outlet through the gas sampling pump, and the display unit, the key unit, the three-way solenoid valve, the chromatographic module, the thermal conductivity detector, and the gas sampling pump are electrically connected to the main control circuit respectively. The technical solution does not need to use high-purity gas as a carrier gas, can not only effectively detect and analyze the content of helium, but also has a small size, light weight, and is easy to carry, and is particularly suitable for field detection and analysis.

[0006] Preferably, the chromatographic module is provided with a wavy airway inside, and the wavy airway is arranged in a plurality of continuous serpentine bends. The bottom of the wavy airway is a silicon substrate, and a heating electrode and a temperature control electrode are provided on the back of the silicon substrate. The wavy airway is filled with porous carbon nanotubes to form a chromatographic column. The air inlet of the wavy airway is connected to the first air outlet of the three-way solenoid valve, and the air outlet of the wavy airway is connected to the air inlet of the measuring cell of the thermal conductivity detector. The heating electrode and the temperature control electrode are electrically connected to the main control circuit respectively. The wavy airway is bent into adjacent concave-convex structures to form a serpentine bend. By changing and extending the airflow path to reduce the length of the chromatographic column, the porous carbon nanotubes in the chromatographic column increase the internal surface area of ​​the chromatographic column, so that the chromatographic column is reduced from a traditional structure with a length of 5m to a micro chromatographic module, becoming a chromatographic chip with a chip area not exceeding 6cm 2 The internal structure of porous carbon nanotubes is extremely fine holes, which makes the gas separate into different components due to thermal power when passing through the chromatographic column, fully separating the helium from other components in the gas, increasing the separation time of helium and other components of the gas, which can reach 5 seconds, so that the helium in the sampled gas is effectively separated, and the separated helium flows into the thermal conductivity detector from the chromatographic module first. The main control circuit receives feedback from the temperature control electrode and controls the heating temperature of the heating electrode through PID control.

[0007] Preferably, the thermal conductivity detector comprises a symmetrically arranged measuring cell and a reference cell and a signal processing circuit, wherein a measuring electrode is arranged in the measuring cell, a reference electrode is arranged in the reference cell, an air inlet of the measuring cell is arranged on the measuring cell, an air inlet of the reference cell is arranged on the reference cell, the measuring cell and the reference cell are both connected to the air outlet of the thermal conductivity detector, the measuring electrode and the reference electrode are respectively connected to the signal processing circuit, and the signal processing circuit is electrically connected to the main control circuit. The helium first separated by the chromatographic module enters the measuring cell, the measuring electrode has a change signal, the sample gas enters the reference cell, the reference electrode has a change signal, the signal processing circuit uses a constant current source and a differential pressure acquisition circuit to obtain the signal of the measuring electrode and the reference electrode to form a bridge output signal, the differential pressure signal is processed, and then the signal is transmitted to the main control circuit after A / D conversion, noise reduction and other processing, the main control circuit calculates the helium concentration in the sample gas to be tested, and displays and stores it.

[0008] Preferably, the bottom of the measuring cell and the reference cell are both single crystal silicon substrates, on which comb-shaped gas channels are formed by deep etching technology, and the measuring electrode and the reference electrode are located above the comb-shaped gas channels, and are both thermosensitive comb-shaped electrodes formed by sputtering Pt-Au alloy on high borosilicate glass and photolithography, so that the gas can fully flow through the electrode surface, thereby improving the sensitivity of the thermal conductivity detector.

[0009] Preferably, the portable helium analyzer includes a flow stabilization module, and the gas sampling pump is connected to the gas outlet via the flow stabilization module, so that the flow of the collected sample gas is stable.

[0010] Preferably, the main control circuit includes a central processing unit and a driving unit and a data storage unit respectively connected to the central processing unit, the driving unit is respectively connected to the three-way solenoid valve, the chromatographic module, and the gas sampling pump, and the thermal conductivity detector is connected to the central processing unit. The key unit is used to issue an operation instruction to the helium analyzer so that the three-way solenoid valve and the gas sampling pump are effectively controlled, thereby effectively controlling the amount of sample gas collected; the driving unit controls the heating temperature of the chromatographic module to ensure that the chromatographic module effectively separates the helium component in the sample gas and allows the helium to enter the measuring cell of the thermal conductivity detector first; the electrical quantity signal of the measuring electrode and the reference electrode of the thermal conductivity detector is output as a differential pressure signal by adopting a constant current source and a differential pressure acquisition circuit, and the signal is transmitted to the central processing unit for calculation and processing after A / D conversion and noise reduction, and is stored in the data storage unit and displayed in the display unit, forming a good human-computer interaction.

[0011] The detection method of the portable helium analyzer of the present invention comprises the following steps:

[0012] ① The main control circuit receives the operation command of the staff, starts the gas sampling pump, controls the three-way solenoid valve to switch to the common port and the second gas outlet, and the gas flows in from the gas inlet, flows into the reference cell gas inlet of the thermal conductivity detector through the three-way solenoid valve, and then flows out from the gas outlet of the thermal conductivity detector, and finally flows out from the gas outlet through the gas sampling pump, and the signal processing circuit in the thermal conductivity detector captures the resistance change signal of the reference electrode;

[0013] ② The main control circuit controls the chromatographic module to heat up quickly, controls the three-way solenoid valve to switch to connect the common port and the first gas outlet, and the gas flows in from the gas inlet, flows into the chromatographic module through the three-way solenoid valve, and then the various components of the gas are discharged from the chromatographic module at different time sequences, and then flows into the measuring cell gas inlet of the thermal conductivity detector, and then flows out from the thermal conductivity detector gas outlet, and finally flows out from the gas outlet through the gas sampling pump, and the signal processing circuit in the thermal conductivity detector captures the resistance change signal of the measuring electrode in the first T seconds;

[0014] ③ The signal processing circuit processes the resistance change signal of the reference electrode and the resistance change signal of the measuring electrode into a differential pressure signal and transmits it to the main control circuit. The main control circuit calculates the helium concentration, displays it on the LCD screen, and stores it.

[0015] The beneficial effects of the present invention are as follows: the chromatographic module and the thermal conductivity detector are both microchip-level structures, the components in the shell are compactly structured, the gas path connections between the devices are short, so that the overall volume is small, and the volume of the instrument is greatly reduced. The chromatographic column is reduced to the size of a chip by using a serpentine-shaped curved chromatographic column and filling with porous carbon nanotubes, so that the peaks between helium and other component gases are fully separated, and the thermistor change of the mixed gas is measured by the reference electrode of the thermal conductivity detector, which not only eliminates the influence of ambient temperature, air pressure and humidity on the thermistor, but also eliminates the need for high-purity gas as a carrier gas. The present invention has a wide detection range, high detection sensitivity, small size, low power consumption, light weight, is easy to carry and transport, and is suitable for various field flow observations. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the portable helium analyzer of the present invention.

[0017] Figure 2 The present invention is a schematic diagram of a gas path connection structure of a portable helium analyzer.

[0018] Figure 3 It is a main structural schematic diagram of the chromatography module in the present invention.

[0019] Figure 4 It is a partial enlarged view of the chromatographic column of the chromatographic module in the present invention.

[0020] Figure 5 It is a rear view structural schematic diagram of the chromatography module in the present invention.

[0021] Figure 6 It is a structural schematic diagram of the thermal conductivity detector in the present invention.

[0022] In the figure, 1. shell, 2. air inlet, 3. three-way solenoid valve, 4. chromatography module, 5. thermal conductivity detector, 6. gas sampling pump, 7. flow stabilization module, 8. air outlet, 9. main control circuit, 10. battery, 11. liquid crystal touch screen, 41. wavy airway, 42. porous carbon nanotubes, 43. heating electrode, 44. temperature control electrode, 51. measuring cell, 52. reference cell, 53. measuring electrode, 54. reference electrode, 55. measuring cell air inlet, 56. reference cell air inlet, 57. thermal conductivity detector air outlet. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0024] Embodiment: A portable helium analyzer of this embodiment, such as Figure 1 As shown, it includes a portable housing 1 and an air inlet 2, a three-way solenoid valve 3, a chromatographic module 4, a thermal conductivity detector 5, a gas sampling pump 6, a flow stabilization module 7, an air outlet 8, a main control circuit 9, a battery 10, and a liquid crystal touch screen 11. The battery adopts a rechargeable lithium battery to power the entire portable helium analyzer. No alternating current is required, and the device can be directly used for detection in the field. The liquid crystal touch screen is located on the front of the housing, the air inlet and the air outlet are located on one side of the housing, and the three-way solenoid valve, the chromatographic module, the thermal conductivity detector, the gas sampling pump, the flow stabilization module, the main control circuit, and the battery are located in the housing. The liquid crystal touch screen, the three-way solenoid valve, the chromatographic module, the thermal conductivity detector, the gas sampling pump, and the flow stabilization module are respectively connected to the main control circuit through signal lines. The liquid crystal touch screen is used to input control instructions and display measurement results. A USB port is provided on the housing for connecting a mobile storage device.

[0025] like Figure 2As shown, the air inlet is connected to the common port of the three-way solenoid valve, the first air outlet of the three-way solenoid valve is connected to the measuring cell air inlet 55 of the thermal conductivity detector via the chromatographic module, the second air outlet of the three-way solenoid valve is connected to the reference cell air inlet 56 of the thermal conductivity detector, and the thermal conductivity detector air outlet 57 is connected to the air sampling pump, the flow stabilization module and the air outlet to form a complete gas path of the portable helium detector. The flow stabilization module is used to control the flow rate of the gas. When the three-way solenoid valve is connected to the chromatographic module, the flow stabilization module controls the flow rate to 10mL / min to ensure that the gas passes through the chromatographic module at a slow speed. When the three-way solenoid valve is directly connected to the thermal conductivity detector, the flow stabilization module controls the flow rate to 100ml / min.

[0026] like Figure 3 , Figure 4 , Figure 5 As shown, there is a wavy air channel 41 inside the chromatography module, the depth of the wavy air channel is 400μm, the width of the groove is 50μm, the wavy air channel is arranged in a number of continuous serpentine bends, and the overall length is 60m. The bottom of the wavy air channel is a silicon substrate, and the top is closed with high borosilicate glass by bonding to form a microchip structure, and the chip area does not exceed 6cm 2 , making the entire chromatography module a micro chromatography module. The wavy airway is filled with porous carbon nanotubes 42 to form a chromatography column. The internal structure of the porous carbon nanotubes is extremely fine holes. The pore size of the porous carbon nanotubes is no more than 50nm, so that helium and other components of gas are separated by obvious peaks due to thermal power when passing through the chromatography column, and the separation time is not less than 5 seconds. The back of the silicon substrate is connected to a heating electrode and a temperature control electrode. The heating electrode 43 and the temperature control electrode 44 are respectively connected to the main control circuit through signal lines. The main control module receives feedback from the temperature control electrode and controls the heating temperature of the heating electrode through PID control.

[0027] like Figure 6As shown, the thermal conductivity detector includes a symmetrically arranged measuring cell 51 and a reference cell 52 and a signal processing circuit. A measuring electrode 53 is installed in the measuring cell, a reference electrode 54 is installed in the reference cell, an air inlet 55 of the measuring cell is arranged on the measuring cell, and an air inlet 56 of the reference cell is arranged on the reference cell. The measuring cell and the reference cell are both connected to the air outlet 57 of the thermal conductivity detector. The measuring electrode and the reference electrode are respectively connected to the signal processing circuit, and the signal processing circuit is connected to the main control circuit through a signal line. The measuring cell and the reference cell use single crystal silicon as a substrate and high borosilicate glass to form a cell body. The silicon substrate is etched by deep etching technology to form a comb-shaped airway. The airway depth is 100μm and the total length of the airway is 2cm, forming a micro thermal conductivity detector. The measuring electrode and the reference electrode have the same structure. A thermistor is formed by sputtering Pt-Au alloy on the high borosilicate glass at the top of the airway. A comb-shaped electrode is formed by photolithography, which is symmetrical with the airway, so that the gas fully flows on the electrode surface to improve the sensitivity of the detector. The measuring electrode and the reference electrode are connected to the signal processing circuit. The signal processing circuit uses a constant current source and a differential pressure acquisition circuit to obtain the signals of the measuring electrode and the reference electrode to form a bridge output signal. After differential pressure signal processing, the signal is transmitted to the main control circuit after A / D conversion, noise reduction and other processing.

[0028] The main control circuit includes a central processing unit and a drive unit and a data storage unit respectively connected to the central processing unit. The drive unit is respectively connected to the three-way solenoid valve, the chromatographic module, and the gas sampling pump, and the thermal conductivity detector is connected to the central processing unit. The central processing unit is a microprocessor, which forms data storage and command transmission with the liquid crystal touch screen. The drive unit controls and drives the three-way solenoid valve, the heating and temperature control modules in the chromatographic module, the gas sampling pump, and the flow control module. The main control circuit receives the signal sent by the signal processing circuit in the thermal conductivity detector, obtains the helium concentration through calculation, and stores the detection data in the internal data storage chip. The detection data is displayed on the liquid crystal touch screen at the same time to realize the human-computer interaction function.

[0029] The detection method of the above portable helium analyzer is:

[0030] ① The operator starts the portable helium analyzer through the LCD touch screen, determines the collection time of the detection gas, and issues a detection command. After receiving the command, the microprocessor drives the gas sampling pump and the flow stabilization module to enter the working state through the drive unit, controls the three-way solenoid valve to switch to the common port and the second gas outlet, and the gas flows in from the gas inlet, flows into the reference cell gas inlet of the thermal conductivity detector through the three-way solenoid valve, and then flows out from the thermal conductivity detector gas outlet, through the gas sampling pump and the flow stabilization module, and finally flows out from the gas outlet. The signal processing circuit in the thermal conductivity detector captures the resistance change signal of the reference electrode;

[0031] ② The flow stabilization module adjusts the flow of the measuring gas, the main control circuit controls the rapid temperature rise of the chromatographic module, controls the three-way solenoid valve to switch to the common port and the first gas outlet, and the gas flows in from the gas inlet, flows into the chromatographic module through the three-way solenoid valve, and then the various components of the gas are discharged from the chromatographic module at different time sequences, and then flows into the measuring cell gas inlet of the thermal conductivity detector, and then flows out from the gas outlet of the thermal conductivity detector, passes through the gas sampling pump and the flow stabilization module, and finally flows out from the gas outlet. The signal processing circuit in the thermal conductivity detector captures the resistance change signal of the measuring electrode in the first 20 seconds;

[0032] ③ The signal processing circuit processes the resistance change signal of the reference electrode and the resistance change signal of the measuring electrode into a differential pressure signal and transmits it to the main control circuit. The main control circuit calculates the helium concentration, displays it on the LCD screen, and stores it.

Claims

1. A portable helium analyzer, characterized in that The portable helium analyzer comprises a portable housing, on which a display unit, a key unit, an air inlet and an air outlet are arranged, and inside the housing are arranged a three-way electromagnetic valve, a chromatographic module, a thermal conductivity detector, a gas sampling pump, a main control circuit and a battery for powering the entire portable helium analyzer; the air inlet is connected to a common port of the three-way electromagnetic valve, a first air outlet of the three-way electromagnetic valve is connected to an air inlet of a measuring cell of the thermal conductivity detector via the chromatographic module, a second air outlet of the three-way electromagnetic valve is connected to an air inlet of a reference cell of the thermal conductivity detector, an air outlet of the thermal conductivity detector is connected to the air outlet via the gas sampling pump, and the display unit, the key unit, the three-way electromagnetic valve, the chromatographic module, the thermal conductivity detector and the gas sampling pump are electrically connected to the main control circuit respectively; The thermal conductivity detector comprises a symmetrically arranged measuring cell and a reference cell and a signal processing circuit, wherein a measuring electrode is arranged in the measuring cell, a reference electrode is arranged in the reference cell, an air inlet of the measuring cell is arranged on the measuring cell, an air inlet of the reference cell is arranged on the reference cell, the measuring cell and the reference cell are both connected to an air outlet of the thermal conductivity detector, the measuring electrode and the reference electrode are respectively connected to the signal processing circuit, and the signal processing circuit is electrically connected to the main control circuit; The bottoms of the measuring cell and the reference cell are both single crystal silicon substrates, on which a comb-shaped airway is formed by deep etching technology. The measuring electrode and the reference electrode are located above the comb-shaped airway. The measuring electrode and the reference electrode are both thermosensitive comb electrodes formed by sputtering Pt-Au alloy on the high borosilicate glass at the top of the airway and by photolithography. The thermosensitive comb electrode and the comb-shaped airway are symmetrical and consistent.

2. A portable helium analyzer according to claim 1, characterized in that The chromatography module is provided with a wavy airway inside, and the wavy airway is arranged in a plurality of continuous serpentine bends. The bottom of the wavy airway is a silicon substrate, and a heating electrode and a temperature control electrode are provided on the back of the silicon substrate. The wavy airway is filled with porous carbon nanotubes to form a chromatographic column. The air inlet of the wavy airway is connected to the first air outlet of the three-way solenoid valve, and the air outlet of the wavy airway is connected to the air inlet of the measuring cell of the thermal conductivity detector. The heating electrode and the temperature control electrode are electrically connected to the main control circuit respectively.

3. A portable helium analyzer according to claim 1 or 2, characterized in that It comprises a flow stabilization module, and the gas collection pump is connected with the gas outlet via the flow stabilization module.

4. A portable helium analyzer according to claim 1 or 2, characterized in that The main control circuit includes a central processing unit and a drive unit and a data storage unit respectively connected to the central processing unit. The drive unit is respectively connected to the three-way solenoid valve, the chromatography module, and the gas sampling pump. The thermal conductivity detector is connected to the central processing unit.

5. A detection method of a portable helium analyzer as claimed in claim 1 or 2, characterized in that The steps include: ① The main control circuit receives the operation command of the staff, starts the gas sampling pump, controls the three-way solenoid valve to switch to the common port and the second gas outlet, and the gas flows in from the gas inlet, flows into the reference cell gas inlet of the thermal conductivity detector through the three-way solenoid valve, and then flows out from the gas outlet of the thermal conductivity detector, and finally flows out from the gas outlet through the gas sampling pump, and the signal processing circuit in the thermal conductivity detector captures the resistance change signal of the reference electrode; ② The main control circuit controls the chromatographic module to heat up quickly, controls the three-way solenoid valve to switch to connect the common port and the first gas outlet, and the gas flows in from the gas inlet, flows into the chromatographic module through the three-way solenoid valve, and then the various components of the gas are discharged from the chromatographic module at different time sequences, and then flows into the measuring cell gas inlet of the thermal conductivity detector, and then flows out from the thermal conductivity detector gas outlet, and finally flows out from the gas outlet through the gas sampling pump, and the signal processing circuit in the thermal conductivity detector captures the resistance change signal of the measuring electrode in the first T seconds; ③ The signal processing circuit processes the resistance change signal of the reference electrode and the resistance change signal of the measuring electrode into a differential pressure signal and transmits it to the main control circuit. The main control circuit calculates the helium concentration, displays it on the LCD screen, and stores it.

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