Hydrogen leakage detector and method for detecting hydrogen leakage

Abstract

A hydrogen leak detector (10) for detecting a leak of a hydrogen conducting component, comprising a hydrogen detector (20) adapted to measure a hydrogen concentration in a gas within a gas conducting path (18), the hydrogen detector (20) comprising: a first gas sensor (24) selective for hydrogen, and adapted to react to a first range of relatively low hydrogen concentrations below a first threshold; and a second gas sensor (26) sensitive and non-selective to hydrogen, and sensitive to at least one other secondary gas different from hydrogen, and adapted to react to a relatively high hydrogen concentration of a second range above the first threshold. Wherein the hydrogen leak detector (10) is adapted to calibrate the second gas sensor (26) for low concentration hydrogen present in the surroundings of the hydrogen detector (20), regardless of whether a leak arises from the measured hydrogen conducting component, by: measuring the hydrogen concentration in the measured gas collected from the surroundings using the first gas sensor (24) and the second gas sensor (26); and by specifying a measurement signal of a second gas sensor (26) of the measured gas as corresponding to a concentration not caused by leakage of the measured hydrogen conducting component if the measurement signal of the first sensor (24) of the measured gas indicates that the hydrogen concentration is below a predetermined value; if the measurement signal of the second gas sensor (26) indicates that the hydrogen concentration is higher than the second threshold value, it is considered that hydrogen leakage exists in the detected hydrogen conduction component.

Description

[0001] The present invention relates to a hydrogen leak detector and a method for detecting leakage of a hydrogen conducting component (such as a pipeline or a storage tank).

[0002] One target application of the present invention is leak detection in natural gas supply and distribution infrastructure. Hydrogen is widely considered an alternative to fossil fuels, particularly natural gas. Within the energy supply sector, there is a demand to transition from natural gas to hydrogen. In addition to developing infrastructure for pure hydrogen production and distribution, the focus is on gradually replacing natural gas with hydrogen. Therefore, there is a need for a detector that can accurately detect and measure hydrogen across the entire concentration range, from ppm (or even lower) to 100% by volume, even in the presence of other gases such as methane in mixed natural gas and hydrogen systems.

[0003] Therefore, the demand for detecting hydrogen in gas samples containing natural gas is growing. For example, hydrogen is transported in natural gas pipelines, where natural gas is mixed with up to 20 vol.% (volume percentage) of hydrogen, because up to 20 vol.% (volume percentage) of hydrogen content does not require any changes to the natural gas combustion equipment. Common traditional natural gas pipelines transport natural gas from the source over long distances to the final consumer. Natural gas is usually composed of methane, or mainly composed of methane and other gaseous components. A common alternative to the natural gas mainly composed of methane is liquefied petroleum gas (LPG), which is composed of propane or butane or a mixture of the two. Any mention of "natural gas" (NG) in this disclosure refers to methane, a gas mixture mainly comprising methane, liquefied petroleum gas (LPG) or a gas mixture comprising a combination of methane, ethane, propane and / or butane.

[0004] Natural gas and hydrogen are highly flammable. For safety reasons, it's crucial to be able to detect even small leaks in hydrogen transport components, such as natural gas pipelines that carry both natural gas and hydrogen. Leak detection should be performed during regular leak surveys and commissioning tests. Furthermore, it's desirable to be able to measure the actual proportion of hydrogen in a gas, such as natural gas.

[0005] The most common gas infrastructure detectors are sniffing detectors, meaning that a gas sample is collected by a sniffer probe or inlet and passed to a detector unit for analysis. However, there are also detectors that transport the gas to the detector by diffusion. Another type of detector that does not use sniffing is the so-called open path optical detection, which does not move the gas sample. Instead, it passes light through the sample and analyzes the loss of optical power at wavelengths that interacted with the gas being measured after the light has passed through the sample. The open path can be between the light source and the sensor, or it can be "semi-open", such as a container with a narrow slot along its axis, where gas can enter and leave the light path by diffusion or convection. The slot is preferably covered with a filter material, such as a breathable membrane, to prevent dust and water from entering the channel.

[0006] Sniffing leak testing is used to detect leaks in large, immovable components. A vacuum pump draws gas through the suction port of a sniffer probe. The sniffer probe is then moved to the area to be tested, such as the exterior surface of the component under test. For buried natural gas pipelines, the sniffer probe is moved above ground above the pipeline. The basic principle is to analyze the gas drawn in by the sniffer probe with a gas detector to determine whether the gas contains gas components originating from within the component under test.

[0007] Sniffer probes used to detect leaks in buried natural gas pipelines typically employ gas detectors capable of detecting natural gas components such as methane, ethane, or propane. As infrared absorption technology becomes increasingly affordable, it is gaining popularity for detecting natural gas components. Polar molecules, such as methane, absorb energy at specific wavelengths of infrared radiation associated with their various vibrational modes. By measuring the intensity of light passing through a gas sample, one or more characteristic wavelengths of the gas under test can be measured. This technique is known as non-dispersive infrared absorption spectroscopy (NDIR). Another effective infrared absorption technique is tunable diode laser absorption spectroscopy (TDLAS), which can detect methane leaks from a distance. This technique is currently relatively expensive but is growing in popularity. However, because hydrogen is a non-polar molecule and does not interact with infrared radiation in this way, neither NDIR nor TDLAS can detect hydrogen. Therefore, these hydrogen-insensitive sensors are referred to as "hydrogen-insensitive."

[0008] Sensors that react to hydrogen, that is, sensors that react to the presence of hydrogen in or on the sensor and generate a measurement signal, are called "hydrogen-sensitive" sensors. Hydrogen-sensitive sensors can generally be divided into two categories: "hydrogen-selective" sensors and "hydrogen-non-selective" sensors.

[0009] A non-hydrogen-selective sensor responds to several different types of gases (one of which is hydrogen), and it is impossible to tell from the measurement signal whether the signal was triggered by hydrogen or the other gas. A hydrogen-selective sensor, on the other hand, produces a measurement signal that clearly identifies the signal as being triggered by hydrogen and not by other gases. For the purposes of this article, a sensor is called a hydrogen-selective sensor if its sensitivity to hydrogen is more than 100 times higher than its sensitivity to other gases typically present around hydrogen-conducting components used to detect hydrogen leaks.

[0010] Common hydrogen detection technologies used in portable hydrogen detectors are:

[0011]

[0012]

[0013] Acoustic and thermal conductivity technologies share several key advantages. They are both insensitive to induction by other gases, have high exposure tolerance, and, because they do not involve chemical reactions, exhibit very low drift over time. The challenge facing these two sensor technologies lies in selectivity. Several other common gases exhibit a fairly strong response to both technologies. Therefore, in this disclosure, these sensors are referred to as hydrogen-sensitive, but not hydrogen-selective.

[0014] While hydrogen has the strongest response of all common gases on both sensors, the effects of other gases still need to be compensated for to obtain the correct hydrogen value. This is especially true for low-hydrogen content natural gas and hydrogen blend systems currently under development.

[0015] Speed ​​of sound (SoS) sensors excite the gas within a measurement space with an acoustic signal and then measure the time it takes for the acoustic signal to travel a certain distance before being detected by a microphone, or determine the acoustic resonant frequency within the measurement space. Such SoS sensors are described in, for example, WO 2013 / 078308 A1 and US Pat. No. 5,768,937 A.

[0016] When designing a gas detector capable of measuring high concentrations of hydrogen, certain drawbacks of the sensor type must be considered. Sensors that are sensitive but not selective for hydrogen (such as acoustic velocity sensors or thermal conductivity sensors) can detect high concentrations of hydrogen, but they are not selective for hydrogen because they are typically reactive to other gases as well, which can affect signal quality, especially at low concentrations. For example, carbon dioxide (CO2) produces a negative acoustic velocity signal, while hydrogen (H2) produces a positive acoustic velocity signal, which can reduce the measurement signal of hydrogen or CO2 in air. Methane (CH4) and water vapor (H2O) produce positive acoustic velocity signals, which can increase the measurement signal of hydrogen mixed with methane or water vapor.

[0017] Therefore, due to the advantages and limitations of various current hydrogen sensor technologies, no single technology is suitable for the entire hydrogen concentration range from a few parts per million (ppm) to 100 Vol. % hydrogen in non-laboratory applications.

[0018] EP3933403A1 discloses a natural gas and hydrogen detector for detecting hydrogen in a mixture of hydrogen and natural gas. The detector utilizes non-dispersive infrared (NDIR) sensor technology to detect natural gas and a second sensor to detect common combustible gases. If the common sensor detects combustible gas, but the NDIR sensor does not detect significantly lower hydrocarbon levels, this can be considered evidence of the presence of hydrogen. Both technologies have selectivity limitations. "Selectivity" here refers to the sensitivity to hydrogen being over 100 times higher than to other common gases in the typical application of detecting leaks in hydrogen-conducting components.

[0019] Combustible gas sensors (such as TC or SoS sensors) react to other gases, which can positively and / or negatively affect the measurement signal. In natural gas pipelines, the most disturbing gases include methane, water, and carbon dioxide, which are present in widely varying concentrations both in the ground and above the surface.

[0020] The table below illustrates the complexity of compensating for the effects of interfering gases on the hydrogen signal in underground hydrogen conductive component leak detection applications.

[0021]

[0022] *Concentrations in liquefied petroleum gas (LPG) are higher. Concentrations in natural gas (NG) are typically less than 1%.

[0023] The zero-hydrogen signal of SoS and TC sensors shifts due to variations in temperature, CO2, and methane levels, further limiting the application of these technologies at low concentrations. This selectivity issue is compounded by the fact that the hydrogen-to-natural gas mixture ratio in the pipeline or system being measured is poorly known. Compensation becomes increasingly difficult as the hydrogen-to-natural gas ratio decreases.

[0024] Perhaps the most challenging application is sampling gas escaping from the ground during a leak survey. As the detector moves across the ground, concentrations of humidity, carbon dioxide, and even methane can fluctuate dramatically. Consequently, the detector must be continuously or intermittently zeroed to ensure stable and accurate measurements across all ranges of the sound velocity or thermal conductivity sensors used at higher ranges. In this context, "zeroing" refers to calibrating the sensor for extremely low or near-zero hydrogen concentrations, with only the natural hydrogen content present in the surrounding air.

[0025] In addition to zeroing, the effects of the aforementioned interfering gases also need to be compensated when calculating the non-zero hydrogen offset in the higher ranges measured by hydrogen-sensitive but non-selective sensors (e.g., TC or SoS sensors).

[0026] It is therefore an object of the present invention to provide a hydrogen leak detector and a method for detecting leaks in hydrogen and hydrogen and natural gas mixture conducting components, in particular outdoors or in other poorly defined environments.

[0027] The leak detector of the invention is defined by independent claim 1. The method of the invention is defined by independent claim 11.

[0028] Thus, the present invention provides a hydrogen leak detector suitable for measuring the concentration of hydrogen in a gas sampled in the vicinity of a gas conducting component.

[0029] In the context of the present disclosure, the term "hydrogen" refers to a gas containing 100 volume percent (vol.%) hydrogen or close to 100 volume % hydrogen, such as at least 80 vol.% hydrogen, and may also refer to a mixture of hydrogen and other gases.

[0030] The hydrogen leak detector of the present invention comprises a hydrogen detector for measuring the concentration of hydrogen gas transmitted through a gas conduction path. The hydrogen detector comprises:

[0031] a first gas sensor selective for hydrogen gas and adapted to respond to a first range of relatively low hydrogen gas concentrations below a first threshold; and

[0032] A second gas sensor is sensitive to and non-selective for hydrogen and is sensitive to at least one other secondary gas than hydrogen and is adapted to respond to a second range of relatively higher hydrogen concentrations above the first threshold.

[0033] The hydrogen leak detector of the present invention is suitable for calibrating a second gas sensor to detect low-concentration hydrogen in the environment surrounding the hydrogen detector, where this low-concentration hydrogen does not originate from a leak in the hydrogen-conducting component being tested. The calibration process is as follows: The first and second gas sensors are used to measure the hydrogen concentration in the gas being tested, collected from the surrounding environment. If the hydrogen concentration indicated by the measurement signal of the first gas sensor is lower than a predetermined value, the measurement signal of the second gas sensor for the gas being tested is designated as corresponding to a concentration not originating from a leak in the hydrogen-conducting component being tested.

[0034] In other words, a gas sample is collected from the ambient atmosphere and measured by a first gas sensor and a second gas sensor. If the first gas sensor indicates that the hydrogen concentration in the measured sample is below a predetermined value, the corresponding measurement signal from the second gas sensor for the same measured gas is assumed to correspond to a hydrogen concentration not caused by a leak in the hydrogen-conducting component being measured. Thus, the measurement signal from the second gas sensor is designated as corresponding to a concentration not caused by a hydrogen leak. In one embodiment, the measurement signal from the second gas sensor is designated as corresponding to a hydrogen concentration of zero volume percent.

[0035] The phrase "assigning the measurement signal of the second gas sensor to a concentration corresponding to..." can be understood to mean, for example, that the computing device or microprocessor includes a memory for storing the assignment result. The computing device or microprocessor uses the measurement signal of the second gas sensor during calibration and stores the signal, or a corresponding signal value, in the memory as a signal or signal value for subsequent testing that does not originate from hydrogen leakage from the hydrogen-conducting component. Additionally or alternatively, the measurement signal or signal value of the second gas sensor can be stored as, or corresponding to, a zero volume percentage of hydrogen.

[0036] If, during a subsequent leak test of a hydrogen-conducting component using the hydrogen leak detector of the present invention, the signal or signal value measured by the second gas sensor corresponds to a signal or signal value previously measured during a calibration process and is below a predetermined value, the hydrogen leak detector of the present invention compares the leak test measurement value with the measurement value pre-stored during the calibration process. If the two values ​​correspond within a predetermined range, the hydrogen leak detector indicates that the measured signal of the hydrogen-conducting component under test is not leaking and / or that the volume percentage of hydrogen generated during the previous calibration process is zero.

[0037] On the other hand, if the first gas sensor indicates that the hydrogen concentration in the measurement sample is above a predetermined value, and the second gas sensor indicates that the hydrogen concentration is above a second threshold, the hydrogen leak detector may determine that a hydrogen leak exists in the hydrogen-conducting component under test. The second threshold may be the same as a predetermined value from the calibration process. This step of determining the presence of a hydrogen leak may also be performed by the computing device or microprocessor described above. For example, in one embodiment, the computing device or microprocessor compares the measurement signal or signal value acquired by the second gas sensor during testing of the hydrogen-conducting component with signal values ​​stored in a memory, wherein at least one signal value is a signal value from the calibration process described above, which has been designated as not corresponding to a concentration resulting from a hydrogen leak and / or corresponding to a hydrogen concentration of zero volume percent.

[0038] Furthermore, if the hydrogen concentration indicated by the first gas sensor is higher than a third threshold value, and the third threshold value is lower than the second threshold value, a hydrogen leak may be determined in the hydrogen-conducting component under test. This step of determining the presence of a hydrogen leak may also be performed by the aforementioned computing device or microprocessor. This expands the response concentration range of the hydrogen leak detector because the two sensors utilize different response hydrogen concentration ranges for leak detection.

[0039] According to the present invention, if the hydrogen concentration indicated by the selective hydrogen sensor exceeds a predetermined threshold, a hydrogen leak is considered to exist in the hydrogen-conducting component being tested. For example, the measurement is initiated by a measurement with a hydrogen-selective gas sensor. If the hydrogen-selective gas sensor indicates a significant hydrogen concentration (possibly caused by a leak in the component being tested), or if the measurement result of the hydrogen-selective gas sensor indicates that the hydrogen-selective sensor is saturated, a hydrogen leak is considered to exist in the component being tested. Therefore, if the hydrogen concentration exceeds the usable range of the hydrogen-selective gas sensor, a second gas sensor is used for further gas analysis to quantify the hydrogen concentration. In this regard, the second gas sensor can be used to measure the speed of sound of an acoustic signal propagating through the gas drawn in through the air inlet. The speed of sound in a gas mixture is affected by various factors, including the types of gas components present in the gas mixture. For example, the speed of sound in air is lower than the speed of sound in a mixture of air and a specific amount of hydrogen at the same temperature.

[0040] In an embodiment applicable to a non-mixed hydrogen conductive element, the hydrogen detector includes a hydrogen-selective gas sensor for measuring a lower hydrogen concentration range and a speed-of-sound (SoS) gas sensor for measuring a higher hydrogen concentration range. The SoS gas sensor measures the speed of sound in the gas being measured, thereby determining the hydrogen concentration in the higher concentration range based on the measured speed of sound. Herein, "lower" refers to a hydrogen concentration lower than that measured by the SoS gas sensor, while "higher" refers to a hydrogen concentration measured by the SoS gas sensor higher than that measured by the hydrogen-selective gas sensor.

[0041] Therefore, while measurement using a hydrogen-selective gas sensor can cover a relatively low hydrogen concentration range, measurement of sound velocity using an SoS gas sensor can cover a relatively high hydrogen concentration range.

[0042] It's known that changes in humidity and carbon dioxide levels can be addressed using filters that capture water and carbon dioxide. However, due to the limited capacity of these filters and their small, lightweight size, they are not suitable for portable devices used continuously or daily. Small, selective filters are insufficient to remove all interfering gases, so they can be used in gas modulation mode, where the signal is analyzed at a modulated frequency or multiples thereof. Small filters can slow down changes in interfering gas concentrations, and algorithms can filter the signal to eliminate variations caused by these changes. This is particularly useful for detecting hydrogen and methane, as these small molecules pass through most surface-active filters with minimal delay. This principle is described in EP3163299A. Therefore, this type of selective filtering cannot address the effects of methane in SoS or TC signals.

[0043] According to the present invention, a first hydrogen-selective gas sensor is used to zero-calibrate or calibrate a second, non-selective gas sensor by measuring the hydrogen concentration in the atmosphere surrounding the hydrogen-conducting component, preferably in the absence of a leak or in the presence of relatively low hydrogen concentrations that are not likely to originate from a leak in the hydrogen-conducting component being measured. Zero-calibration is used to adapt the baseline of the measurement signal of the second non-selective gas sensor to the current level of interfering gas in the surrounding atmosphere. The measurement signal acquired by the hydrogen-selective gas sensor during zero-calibration is used as a reference signal for measuring gases with insignificant hydrogen concentrations that are not likely to originate from a leak in the component being measured.

[0044] To achieve this, the hydrogen leak detector of the present invention may include a computing device, such as a microprocessor, having a memory for storing measurement signal values. During zero-point compensation (also referred to as a "calibration process" in this disclosure), when there is no leak in the hydrogen-conducting component being measured, both the first gas sensor and the second gas sensor acquire measurement signals from gas taken from the surrounding atmosphere. The computing device evaluates the measurement signal from the first gas sensor and compares the signal value with a predetermined value. If the signal value from the first gas sensor is lower than the predetermined value, the corresponding signal value simultaneously acquired by the second gas sensor is stored in the memory, the signal value corresponding to the hydrogen concentration not caused by a possible leak in the component being measured. This is also currently referred to as designating the measurement signal of the second gas sensor of the gas being measured as corresponding to a concentration not caused by a leak in the hydrogen-conducting component being measured.

[0045] If, during a subsequent hydrogen component leak test, the measurement signal value measured by the second gas sensor corresponds to the stored signal value within a predetermined deviation range, the measurement value is deemed not to be derived from a leak in the component under test. The computing device of the hydrogen leak detector of the present invention compares the measurement value measured by the second sensor during the leak test with the measurement value stored in memory during a previous calibration process. If the measurement value during the leak test is equal to or lower than a stored value that does not correspond to a leak concentration in the component under test, the computing device issues a signal to inform the operator that the value is not derived from a leak, or that no leak exists. On the other hand, if the signal value measured during the leak test is above a second threshold (e.g., above the predetermined value during the calibration process), the computing device issues a signal to inform the operator that a leak exists in the component under test, or that the measurement signal corresponds to a concentration that is derived from a leak in the component under test.

[0046] Therefore, the first gas sensor is used to calibrate or zero-point compensate the second gas sensor, while the second gas sensor is used to perform actual leak testing on hydrogen-conducting components, so that the second gas sensor can be used within a wider hydrogen concentration range. This wider hydrogen concentration range is particularly larger than the concentration range in which a hydrogen-sensitive gas sensor that is not selective for hydrogen is typically sensitive to hydrogen gas leaking from the component being tested.

[0047] Therefore, the present invention provides a hydrogen leak detector, which uses a hydrogen-sensitive gas sensor that is not selective for hydrogen in a wider concentration range for hydrogen leak detection.

[0048] The second gas sensor can be a sonic velocity sensor (such as the sensor described in US 2013 / 0125622 A1) or a thermal conductivity sensor. These types of sensors are less susceptible to damage or poisoning by overexposure. Therefore, the second gas sensor can be used to measure the hydrogen concentration that causes the first gas sensor to saturate.

[0049] As mentioned above, the interfering gases carbon dioxide (CO2) and methane (CH4) are usually present in high concentrations and seriously interfere with the measurement signal of the second gas sensor, especially in the case of SoS or TC gas sensors.

[0050] Therefore, in the present invention, it is necessary to measure the concentrations of these gases to compensate for the measurement signal of the second gas sensor, thereby achieving accurate quantification of the hydrogen concentration.

[0051] The effect of water vapor (humidity) is expected to be less significant, as its variations are expected to be small and the concentration rarely exceeds 10 vol.%. Ideally, the water concentration would also be measured to further improve the accuracy of the hydrogen estimate.

[0052] In an embodiment where the second gas sensor is a non-absorptive infrared (NDIR) sensor, methane, carbon dioxide, and water can all be measured by the NDIR sensor to provide data used to compensate the signal of the first gas sensor (which can be a SoS or TC sensor). In this embodiment, methane, carbon dioxide, and water are the secondary gases to which the second gas sensor is sensitive.

[0053] The measured sound velocity can be used to determine the amount of hydrogen in the measured gas mixture. In embodiments where the second gas sensor is a sound velocity sensor, a first approximation of the hydrogen concentration can be calculated by assuming that the sound velocity measured at the most recent zeroing is representative of the velocity in the ambient gas and that changes in velocity are due solely to the addition of hydrogen.

[0054] A second, more accurate approximation is to assume that the ambient atmosphere consists of air, methane, and carbon dioxide, and to measure the concentrations of the latter two gases simultaneously with the hydrogen content to be calculated. This leaves only one unknown quantity, the hydrogen concentration, since the air concentration is the remainder after subtracting the unknown hydrogen concentration and the measured methane and carbon dioxide concentrations.

[0055] A more accurate approximation can be obtained by measuring the water concentration or water vapor concentration. Water vapor is currently considered as a secondary gas to which the second gas sensor is sensitive. In all cases, the speed of sound in air is estimated based on the last zero point measurement and compensated for the concentration of the interfering gas at that time.

[0056] It is also best to consider the gas temperature in all calculations.

[0057] Additionally, or as an alternative, the measured sound velocity can be compared with reference values ​​taken from reference measurements of gas mixtures of a specific hydrogen concentration, which may be at different temperatures.

[0058] First, the hydrogen-selective gas sensor can be a metal hydride (MH-) semiconductor sensor implemented using a field effect transistor (FET) or a Schottky diode, or any other type of hydrogen sensor that is at least 100 times more sensitive to hydrogen than to CO2, CH4, and water vapor.

[0059] The second gas sensor may be a SoS sensor comprising: a measuring container that can be filled with a gas to be measured; a sound source adapted to emit a sound signal into the gas in the container; and at least one microphone adapted to receive the sound signal transmitted from the sound source through the container.

[0060] The hydrogen concentration can be calculated from the measured sound velocity, especially when the concentrations of all gas components except one are known, as well as the overall concentration. For example, in a mixture of hydrogen, air, and methane (CH4), the concentrations of air and CH4 are needed to calculate the hydrogen (H2) concentration.

[0061] Other types of sensors may also be used to determine the presence and / or concentration of other gas components in the measured gas mixture.

[0062] The sound speed measurement can be improved by using at least two microphones at known distances, where the sound speed is calculated based on the time difference between the sound signals received by the two microphones and the distance between the two microphones.

[0063] Alternatively, the speed of sound can be calculated using the resonant frequency f, which is the speed of sound c divided by the wavelength λ at which resonance occurs. Thus, if the resonant wavelength λ and the resonant frequency f are known, the speed of sound can be calculated.

[0064] When using two microphones to measure sound speed, the two microphones are located at different locations within a tubular arrangement (also called a measurement vessel). A sound signal generated by a loudspeaker (the sound source or emitter) travels within the tube to the first microphone and then to the second microphone, which is located farther from the loudspeaker. The microphone signals are then used to calculate the time required for the sound signal to travel between the two microphones. The sound speed is then calculated by dividing the distance between the two microphone locations by the time it takes for the sound signal to travel that distance.

[0065] In a preferred embodiment of the present invention, the hydrogen gas detector is combined with a third gas sensor for measuring the concentration of natural gas or a natural gas component in a mixed gas channeled through a gas conduction path. For example, the third gas sensor can include a radiation absorption container that can be filled with the gas to be measured. A radiation source is provided for emitting radiation of a known frequency band into the gas within the container, and a radiation detector is provided for detecting the radiation transmitted through the container to determine the absorption band of the detected radiation. For example, the radiation absorption detector can be an infrared absorption detector, such as a non-dispersive infrared radiation (NDIR) analyzer. This concept is particularly advantageous for detecting hydrocarbons in mixed gases.

[0066] The third gas sensor may be a non-dispersive infrared (NDIR) sensor, in particular a wide-range methane non-dispersive infrared (NDIR) sensor such as described in WO 2017 / 121688 A1.

[0067] When the third gas sensor is used in combination with a hydrogen detector of the type described above, the concentration of hydrogen in natural gas can be detected, and / or the third gas sensor can be used to determine whether a measured speed of sound (which deviates from the speed of sound in air) is caused by hydrogen or a natural gas component.

[0068] The third gas sensor is configured to measure the gas guided through the gas conduction path. The third gas sensor is insensitive to hydrogen but is sensitive to the at least one secondary gas to which the second gas sensor is sensitive. The third gas sensor can be configured to analyze the measurement signal (e.g., for a non-dispersive infrared sensor, analyze absorbance in other wavelength ranges) to measure the concentration of other gases (secondary gases) that affect the measurement signal of the second gas sensor (e.g., for a sound velocity sensor, analyze the speed of sound in the sample). Such gases may include, for example, carbon dioxide and water. This information can be used to further improve the accuracy and selectivity of the detector within the range covered by the second gas sensor.

[0069] The third gas sensor may also be used to interpret the measurement signal of the first gas sensor by evaluating whether the measurement signal of the first gas sensor is generated by hydrogen or by one or more secondary gases to which the first gas sensor is also sensitive.

[0070] Hydrogen leak detectors may be portable and / or sniffer-type leak detectors that can be used to detect leaks in natural gas pipelines that carry quantities of hydrogen.

[0071] Embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0072] Figure 1 This is the overall layout of the first embodiment;

[0073] Figure 2 This is the overall layout of the second embodiment;

[0074] Figure 3 for Figure 2 Detailed view of the illustrated embodiment;

[0075] Figure 4 A detailed view of another embodiment;

[0076] Figure 5 This is a general layout diagram of another embodiment.

[0077] Figure 1 A hydrogen gas leak detector 10 is shown in the form of a sniffing leak detector having a sniffing probe 12 with a sniffing inlet 14. The sniffing probe 12 is connected via a gas conducting path 18 to a vacuum pump 16, which includes a hydrogen gas detector 20. The hydrogen gas detector 20 includes a first gas sensor 24, a second gas sensor 26, and a third gas sensor 22.

[0078] The hydrogen gas detector 20 includes a first hydrogen-selective gas sensor 24 in the form of a metal hydride (MH) semi-field effect (FET) gas sensor and a second gas sensor 26 in the form of a speed-of-sound (SoS) gas sensor. Gas passing through the gas conductive path 18 flows through both the first hydrogen-selective gas sensor 24 and the second SoS gas sensor 26. The gas conductive path 18 also includes a third natural gas sensor 22 in the form of a non-dispersive infrared (NDIR) analyzer.

[0079] Figure 1 Not shown, second gas sensor 26 includes a measurement container having a gas inlet connected to gas conduction path 18 for filling with gas guided through gas conduction path 18. Furthermore, a sound transmitter in the form of a loudspeaker and two microphones are positioned along the measurement container such that the sound signal emitted by the sound transmitter passes through the gas-filled measurement container before reaching the first microphone and then continuing to propagate to the second microphone. Consequently, the two microphones capture the sound signals at two different times. The speed of sound in the container is calculated based on the distance between the two microphones and the time difference between when the sound signal is captured by the first microphone and when it is captured by the second microphone.

[0080] The third gas sensor 22 comprises an absorption container. Figure 1 The absorption container of the third gas sensor 22 (natural gas sensor) and the measuring container of the second gas sensor 26 (sonic velocity gas sensor) can advantageously be identical. Figure 2-Figure 4 For simplicity, Figure 1 The third gas sensor 22 and the second gas sensor 26 are shown as two separate components.

[0081] Therefore, the absorption vessel of the third gas sensor 22 also includes a gas inlet connected to an infrared (IR) sensor, as well as an IR emitter 26a and an IR detector 26b located on either side of the vessel. Infrared light emitted by the IR emitter passes through the vessel and the gas therein, and is then analyzed by the IR detector 26b. This analysis is based on the absorption principle and is performed in a generally known manner. The loss of light intensity due to absorption is analyzed within one or more wavelength ranges known to be absorbed by natural gas.

[0082] Measuring natural gas concentration and methane concentration is particularly necessary in order to correctly measure hydrogen concentration in samples with significant methane concentration, where "significant" means greater than 5 vol% of the actual hydrogen concentration in the sample.

[0083] A third infrared sensor 26 can be configured to analyze absorption at other wavelengths to measure the concentrations of other gases that affect the speed of sound in the sample, such as carbon dioxide and water. This information can be used to further improve the accuracy and selectivity of the detector within the range covered by the second SoS sensor 26.

[0084] Figure 2 、 3 4 and 5 respectively show embodiments in which the second gas sensor 26 and the third gas sensor 22 share the same measurement container 40 .

[0085] exist Figure 2 In the embodiment of the present invention, the hydrogen leak detector 10 is also a Figure 1 The same sniffing leak detector comprises a sniffer probe 12 with a gas inlet 14 and a gas conducting path 18 connecting the gas inlet 14 to a vacuum pump 16 that exhausts the gas to, for example, the atmosphere. Figure 2 Examples and Figure 1 The difference between the embodiments of FIG. 1 and FIG. 2 lies in the arrangement of the first gas sensor 24, the second gas sensor 26 and the third gas sensor 22. Figure 2 In the figure, the second gas sensor 26 is a sound velocity sensor that uses the same measurement container 40 as the third gas sensor 22, namely a non-dispersive infrared (NDIR) sensor. The third sensor 26 includes a sound source, such as a directional speaker 26a located at one end of the container 40, and a microphone 26b located at the other end of the container 40. Therefore, the sound signal emitted by the sound source 26a will pass through the container 40 and the gas therein, and then be received by the microphone 26b. Similarly, the third gas sensor 22 includes an infrared source 22a located at one end of the container 40, and an infrared sensor 22b located at the other end of the container 40. Therefore, the infrared signal emitted by the infrared source 22a will pass through the container 40 and the gas therein, and then be received by the infrared sensor 22b. Signal analysis of the measurement signals generated by the three gas sensors 22, 24, and 26 (particularly the infrared sensor 22b and the microphone 26b) is performed by a computing device (such as a microprocessor or computer), which is not shown in the figure for simplicity. The computer or computing device is electrically connected to at least all of the gas sensors 22 , 24 , 26 of the hydrogen gas detector 20 .

[0086] exist Figure 2 In the exemplary embodiment, the first gas sensor 24 is arranged in the gas conducting path 18 between the measuring container 40 and the vacuum pump 16 .

[0087] As an alternative, the first gas sensor 24 can also be arranged in the gas-conducting path 18 between the sniffer probe 12 and the container 40 .

[0088] Alternatively, in additional embodiments, the gas sensors 24 , 26 , 22 may be arranged in parallel within the gas conducting path 18 rather than in series.

[0089] This is Figure 3 As shown in the figure, the Figure 2 Details of the hydrogen detector in Figure 3 The remaining arrangement of the hydrogen leak detector 10 (regarding the gas conducting path 18, the sniffer probe 12, the gas inlet 14 and / or the vacuum pump 16) can be the same as Figure 1 and Figure 2 As an alternative, according to Figure 3 and Figure 4 The hydrogen gas detector 20 may be a non-sniffer type hydrogen gas detector, such as an open-circuit detector including a measurement volume 50 in which the gas to be analyzed is collected. On opposite sides of the measurement volume 50, a sound source 26a and a microphone 26b, as well as an infrared source 22a and an infrared sensor 22b are arranged, so that the sound signal emitted by the sound source 26a and the infrared signal emitted by the infrared source 22a pass through the measurement volume 50 and the gas contained therein, and are then received by the microphone 26b and the infrared sensor 22b, respectively, similar to Figure 2 Regarding the situation of the measuring container 40.

[0090] exist Figure 3 In the embodiment, the first gas sensor 24 is in the form of a metal hydride sensor, for example, which is arranged near the measurement volume 50 so that the gas in the measurement volume 50 contacts the first gas sensor 24. Therefore, since the first gas sensor 24 is hydrogen selective, the contact between the gas in the measurement volume 50 and the first gas sensor 24 causes the measurement signal of the first gas sensor 24 to indicate hydrogen.

[0091] Figure 4 The embodiment shown is Figure 3 The embodiment shown differs in that the infrared source 22a and infrared sensor 22b of the third gas sensor 22 and the sound source 26a and microphone 26b of the second gas sensor 26 are arranged in a manner similar to that of the infrared source 22a and infrared sensor 22b of the third gas sensor 22 and the sound source 26a and microphone 26b of the second gas sensor 26. Figure 1 The embodiment shown is arranged in a similar manner on opposite sides of the measuring container 40. The measuring container 40 comprises a longitudinal opening 60 covered by a gas permeable membrane or filter, through which the measuring gas can be directly taken from the environment near the hydrogen conducting component or from the gas conducting path 18 ( Figure 4 The first gas sensor 24 is attached to the measurement container 40 in such a manner that the gas within the container contacts the first gas sensor 24, thereby generating a measurement signal of the first gas sensor 24. If the gas within the container 40 contains hydrogen below a first threshold value, the measurement signal of the first gas sensor 24 indicates hydrogen.

[0092] Figure 5 An embodiment is shown in which a first gas sensor 24, a second gas sensor 26, and a third gas sensor 22 are arranged in parallel. The gas inlet 14 leads to a gas conduction path 18 containing a vacuum pump 16. The gas conduction path 18 is divided into three independent conduction paths, each conduction path containing one of the three gas sensors 22, 24, 26. Figure 5 The upper gas conduction path in FIG. 1 includes the second gas sensor and a sampling vacuum pump 32 located upstream of the sensor 26. The second gas sensor 26 is a sound velocity sensor with a sound source 26a and two independent microphones 26b. The middle gas conduction path includes the first gas sensor 24 and an independent sampling vacuum pump 34 located upstream of the first gas sensor 24. Figure 5 In an embodiment of the present invention, the first gas sensor 24 may be a gas field effect transistor (FET) sensor.

[0093] The lower gas conduction path includes the third gas sensor 22 and another sampling vacuum pump 36 located downstream of the sensor 22 . Figure 5 The third gas sensor 22 in the illustrated embodiment is an NDIR sensor that is insensitive to hydrogen but sensitive to methane and carbon dioxide, which are the secondary gases of the second gas sensor 26 , ie, the gases to which the second gas sensor 26 is sensitive.

Claims

1. A hydrogen leak detector (10) for detecting leakage of a hydrogen conducting component, comprising: A hydrogen gas detector (20) for measuring the hydrogen concentration of gas in a gas conducting path (18), the hydrogen gas detector (20) comprising: a first gas sensor (24) selective for hydrogen and adapted to respond to a first range of relatively low hydrogen concentrations below a first threshold; and a second gas sensor (26) sensitive to and non-selective for hydrogen and sensitive to at least one other secondary gas than hydrogen, and adapted to respond to a second range of relatively high hydrogen concentrations above the first threshold; The hydrogen leak detector (10) is adapted to measure the hydrogen concentration in the gas to be measured collected from the ambient atmosphere by using a first gas sensor (24) and a second gas sensor (26), and if the measurement signal of the first gas sensor (24) for the gas to be measured indicates that the hydrogen concentration is lower than a predetermined value, calibrate the second gas sensor (26) by designating the measurement signal of the second gas sensor (26) for the gas to be measured as corresponding to a concentration that does not originate from a leak in the hydrogen-conducting component to be measured, so as to detect low-concentration hydrogen gas present in the ambient atmosphere of the hydrogen detector (20), and whether the low-concentration hydrogen gas originates from a leak in the hydrogen-conducting component to be measured; and If the second gas sensor (26) indicates that the hydrogen concentration is higher than a second threshold, it is considered that there is a hydrogen leak in the hydrogen conducting component being tested.

2. The hydrogen leak detector (10) according to claim 1, wherein The second gas sensor (26) is used to measure the hydrogen concentration that causes the first gas sensor (24) to be saturated.

3. The hydrogen leak detector (10) according to claim 1 or 2, wherein: The first gas sensor (24) is a metal hydride gate field effect transistor (FET) gas sensor, a metal hydride Schottky diode gas sensor, or a selective metal oxide (MOS) gas sensor.

4. The hydrogen leak detector (10) according to any one of the preceding claims, wherein If the first gas sensor (24) indicates that the hydrogen concentration is higher than a third threshold, it is considered that there is a hydrogen leak in the hydrogen conducting component being tested, and the third threshold is lower than the second threshold.

5. The hydrogen leak detector (10) according to one of the preceding claims, wherein The second gas sensor (26) is a speed of sound (SoS) gas sensor or a thermal conductivity (TC) gas sensor.

6. The hydrogen leak detector (10) according to one of the preceding claims, wherein The second gas sensor (26) comprises: a measuring container that can be filled with a gas to be measured, a sound source adapted to transmit a sound signal through the gas in the container, and at least one microphone adapted to receive the sound signal emitted by the sound source and transmitted through the container.

7. A hydrogen leak detector (10) according to the preceding claim, wherein The second gas sensor (26) includes at least two microphones adapted to receive the sound signal transmitted from the sound source through the container, wherein the speed of the sound signal is calculated based on a time difference between when the two microphones receive the sound signal and based on a distance between the two microphones.

8. The hydrogen leak detector (10) according to any one of the preceding claims, comprising: A third gas sensor (22) is adapted to measure the gas guided through the gas conducting path (18), the third gas sensor (22) being insensitive to hydrogen but sensitive to the at least one secondary gas to which the second gas sensor (26) is sensitive.

9. A hydrogen leak detector (10) according to the preceding claim, wherein The third gas sensor (22) comprises: a radiation absorbing container that can be filled with a gas to be measured, a radiation source adapted to emit radiation of a known frequency band to the gas in the container, and a radiation detector adapted to detect radiation passing through the container and determine an absorption band of the detected radiation.

10. A hydrogen leak detector (10) according to the preceding claim, wherein The absorption container of the third gas sensor (22) is used as a measurement container for the second gas sensor (26) to measure the speed of sound.

11. The hydrogen leak detector (10) according to one of the preceding claims, wherein The hydrogen leak detector is a handheld detector.

12. A method for detecting leakage of a hydrogen conducting component, wherein: Measure the hydrogen concentration in the area to be tested by the following steps: using a first gas sensor (24) that is selective for hydrogen and adapted to respond to a first range of relatively low hydrogen concentrations below a first threshold value for measuring the first range in the measured gas; and using a second gas sensor (26) that is sensitive to and non-selective for hydrogen and sensitive to at least one other secondary gas than hydrogen and adapted to respond to a second range of relatively high hydrogen concentrations above the first threshold value for measuring the second range in the measured gas; The following steps are involved: The second gas sensor (26) is calibrated to detect a low hydrogen concentration in the environment surrounding the hydrogen detector (20), wherein the low hydrogen concentration is not caused by leakage of the hydrogen conducting component being measured, and the calibration method is: Using the first gas sensor (24) and the second gas sensor (26) to measure the hydrogen concentration in the measured gas collected from the surrounding environment, and If the measurement signal of the first gas sensor (24) for the measured gas indicates that the hydrogen concentration is lower than a predetermined value, designating the measurement signal of the second gas sensor (26) for the measured gas as corresponding to a concentration not originating from a leak in the measured hydrogen-conducting component; If the hydrogen concentration measured by the second gas sensor (26) exceeds a second threshold, it is considered that there is a hydrogen leak in the hydrogen conducting component.

13. Method according to the preceding claim, using a hydrogen leak detector (10) according to one of the preceding claims.

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