A fast and sensitive hydrogen detector

Abstract

In various embodiments, rapid and sensitive detection of molecular hydrogen is achieved by receiving a sample gas containing ambient water vapor and hydrogen, passing the sample gas through a gas dryer, chemically converting hydrogen in the sample gas to water vapor to produce a converted sample gas, measuring the water vapor in the converted sample gas to produce a water vapor signal, and separating the water vapor signal in the time domain into an ambient water vapor signal and a hydrogen-derived water vapor signal, where the gas dryer attenuates fluctuations in the ambient water vapor signal, and outputting a hydrogen signal that is descriptive of the molecular hydrogen in the sample gas based on the hydrogen-derived water vapor signal.

Description

[Technical field]

[0001] This disclosure relates generally to gas detection, and more particularly to rapid and sensitive detection of molecular hydrogen. [Background technology]

[0002] There is an increasing need for rapid and sensitive detection of molecular hydrogen. As the world transitions away from fossil fuels as the primary energy source, a hydrogen-based energy infrastructure is likely to emerge. For both economic and safety reasons, it is imperative to have an effective method of measuring hydrogen concentration. For example, it is essential to have an effective method of measuring hydrogen concentration in a sample gas (e.g., air) in order to detect hydrogen gas leaks. Hydrogen detectors are likely to play a key role in a hydrogen-based energy infrastructure, just as methane detectors play a key role in the existing natural gas-based energy infrastructure.

[0003] Many currently deployed methane detectors utilize optical detection to measure methane concentrations and detect methane gas leaks. Optical detection can be fast, sensitive, portable, and specific, and at first glance appears to be an attractive option for use in hydrogen detection. However, unlike methane, hydrogen does not have strong absorption characteristics in the near ultraviolet (UV), visible, infrared (IR), or microwave regions of the electromagnetic spectrum. Thus, it is very difficult to optically detect molecular hydrogen by conventional techniques, and direct optical detectors of hydrogen have not proven viable. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, there is a need for improved techniques for detecting molecular hydrogen that can enable rapid and sensitive hydrogen detection. [Means for solving the problem]

[0005] In various embodiments, rapid and sensitive detection of molecular hydrogen is achieved by chemically converting hydrogen to water vapor (i.e., oxidizing the hydrogen) and then optically detecting the water vapor (e.g., using optical detection techniques such as laser spectroscopy, non-dispersive infrared (NDIR) absorption spectroscopy, etc.). The water vapor serves as a surrogate for hydrogen such that the hydrogen is indirectly detected. Indirect detection avoids the difficulties of optically detecting molecular hydrogen itself and can provide other advantages. However, indirect detection can also introduce other challenges. In various embodiments described herein, these other challenges can be addressed.

[0006] One challenge is that sample gases (e.g., air) often contain a lot of ambient water vapor (e.g., 1%-4%). ​​The additional water vapor generated by chemically converting hydrogen is typically very small compared to the ambient water vapor. Even when detecting in the vicinity of a hydrogen leak, it can be a few hundred parts in, and remote from the hydrogen leak, it can be tens of thousands of parts in. In addition, the amount of ambient water vapor can change with time and can be correlated with air movement, creating further problems in specific detection.

[0007] In various embodiments described herein, this challenge can be addressed by separating the water vapor signal describing the detected water vapor concentration into two components in the time domain, referred to as the "ambient water vapor signal" and the "hydrogen-derived water vapor signal." Separation can be facilitated by damping fluctuations in the ambient water vapor signal to distinguish the ambient water vapor signal from the more rapidly fluctuating hydrogen-derived water vapor signal. Damping can be achieved in a variety of ways. In one embodiment, a gas dryer (e.g., a Nafion™ sulfonated tetrafluoroethylene-based fluoropolymer copolymer membrane gas dryer) can be employed. Various additional techniques can be employed to improve such embodiments. For example, the hydrogen-derived water vapor signal can be rapidly modulated to further facilitate separation from the ambient water vapor signal. Similarly, the sample gas can be pre-humidified to a predetermined level to eliminate the memory of the actual ambient water vapor and ensure a constant, stable ambient water vapor signal that can be easily separated.

[0008] Another challenge is that sample gases (e.g., air) often contain hydrocarbons and other hydrogen-containing molecules that can be converted to water vapor in a chemical transformation. This alternative source of water vapor can result in interference signals. Such interference signals can be significant in high sensitivity applications (e.g., applications with hydrogen concentrations below 1 part per million (ppm)) or in environments where the concentration of hydrogen-containing molecules is unusually high.

[0009] In various embodiments described herein, this problem can be addressed by suppressing hydrogen-containing molecules in the sample gas by trapping (using filters, membranes, molecular sieves, cryogenic traps, and / or other techniques) or adjusting chemical conversions to selectively oxidize hydrogen while avoiding conversion of hydrogen-containing molecules to water vapor. Alternatively, this problem can be addressed by measuring the hydrogen-containing molecule concentration, calculating the amount of water vapor from hydrogen-containing molecules, and subtracting the water vapor from hydrogen-containing molecules.

[0010] It should be understood that various additional features and embodiments may be implemented beyond those discussed in this summary. This summary is intended merely as a brief introduction to the reader for the further description that follows, and does not suggest or imply that the features and embodiments described herein are inclusive of all aspects of the present disclosure or are necessary or mandatory parts of the present disclosure.

[0011] The description refers to the accompanying drawings of example embodiments. [Brief description of the drawings]

[0012] [Figure 1A] 4 is a flow diagram of an exemplary sequence of steps for detecting molecular hydrogen according to a first embodiment. [Figure 1B] FIG. 1B is a block diagram of an example hydrogen detector having components capable of implementing the sequence of steps of FIG. 1A. [Figure 1C] 1 is a set of graphs 154-158 illustrating an example water vapor signal, an ambient water vapor signal, and a hydrogen-derived water vapor signal as a function of time. [Figure 2A] 5 is a flow diagram of an exemplary sequence of steps for detecting molecular hydrogen according to a second embodiment. [Figure 2B] FIG. 2B is a block diagram of an example hydrogen detector having components capable of implementing the sequence of steps of FIG. 2A. [Figure 2C] 1 is a graph illustrating an example water vapor signal having a rapidly modulated hydrogen-derived water vapor component. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] FIG. 1A is a flow diagram of an exemplary sequence 100 of steps for detecting molecular hydrogen according to a first embodiment. FIG. 1B is a block diagram of an exemplary hydrogen detector 102 having components capable of implementing the sequence 100 of steps of FIG. 1A. In step 110, an inlet 112 of the hydrogen detector 102 receives a sample gas (e.g., air) containing ambient water vapor, molecular hydrogen, and possibly hydrogen-containing molecules (including methane and non-methane hydrocarbons (NMHCs)). Ambient water vapor in the sample gas may vary, typically falling between 10,000 ppm and 20,000 ppm for air. Hydrogen-containing molecules in the sample gas are typically present in much smaller amounts, typically about 3 ppm for air (with methane typically accounting for about 2 ppm and NMHCs accounting for the remaining 1 ppm). In the absence of a hydrogen source (e.g., a hydrogen leak), hydrogen is typically found in air at about 0.5 ppm. Simple implementations of the hydrogen detector 102 may be suitable for detecting hydrogen concentrations from about 1 ppm to about 40,000 ppm (i.e., the lower explosive limit of hydrogen). More sophisticated implementations of the hydrogen detector (e.g., taking into account the possible presence of hydrogen-containing molecules in the sample gas) may be capable of specifically detecting concentrations below 1 ppm.

[0014] In step 120, the sample gas from the inlet 112 is passed through a gas dryer 122, or more specifically, a high pressure segment thereof. In one embodiment, the gas dryer 122 is a Nafion™ sulfonated tetrafluoroethylene-based fluoropolymer copolymer membrane gas dryer. Alternatively, a wide variety of types of gas dryers can be employed. The gas dryer 122 can remove some ambient water vapor from the sample gas. However, the primary purpose of the gas dryer 122 is not to remove the ambient water vapor, but to attenuate the time response in the ambient water vapor without substantially affecting the hydrogen. As will be further described below, the gas dryer 122 plays a role similar to a low pass filter in the electronics field.

[0015] In step 130, the sample gas from the gas dryer 122 (or more specifically, the high pressure segment thereof) is received in a catalytic furnace 132 to chemically convert hydrogen in the sample gas to water vapor (i.e., oxidize the hydrogen). The catalytic furnace 132 can include a high temperature (e.g., 100 degrees Celsius (°C) to 200°C) catalytic surface (e.g., a platinum (Pt) surface) that rapidly and quantitatively converts hydrogen to water vapor.

[0016] The gas dryer 122 and the catalytic furnace 132 can be operated at near atmospheric pressure. In step 140, the converted sample gas from the catalytic furnace 132 is passed through a flow controller 142, which reduces the pressure. The flow controller 142 can create the pressure drop by restricting the flow rate in various ways. In one embodiment, the flow controller is a critical orifice that restricts the flow rate. In some cases (e.g., cases where the water vapor concentration is 40,000 ppm or more), condensation may tend to occur between the catalytic furnace 132 and the flow controller 142. To avoid condensation, this area can be maintained at an elevated temperature (e.g., 30° C. or higher). In one embodiment, this elevated temperature can be achieved by placing the flow controller 142 very close to the catalytic furnace 132, so that the by-product heat from the catalytic furnace 132 maintains a high temperature.

[0017] In step 150, the converted sample gas from the flow controller 142 is received in a water vapor monitoring cell 152, which measures the water vapor therein to generate a water vapor signal. The water vapor monitoring cell 152 may employ optical detection, such as laser spectroscopy or non-dispersive infrared (NDIR) absorption spectroscopy. However, it should be understood that other types of detection may be employed, including other types of optical detection, and the water vapor monitoring cell 152 may include various types of devices, including other types of spectroscopy.

[0018] The water vapor signal generated by the water vapor monitoring cell 152 includes two components in the time domain: a component derived from ambient water vapor, referred to herein as the "ambient water vapor signal," and a component derived from converted hydrogen, referred to herein as the "hydrogen-derived water vapor signal." FIG. 1C is a set of graphs 154-158 showing an example water vapor signal, an ambient water vapor signal, and a hydrogen-derived water vapor signal as a function of time. The ambient water vapor signal often has a significant offset (e.g., 100 ppm to 1000 ppm) even after reduction by the gas dryer 122 due to the typically high concentration of ambient water vapor in the atmosphere (e.g., 10,000 ppm, 20,000 ppm, etc.), and typically fluctuates only over long periods (e.g., periods longer than 1 minute). The ambient water vapor signal is typically relatively constant over short periods (e.g., periods less than 1 second (s)) due to the damping effect of the gas dryer 122. The hydrogen-derived water vapor signal typically does not have a significant offset due to the typically small concentration of hydrogen in the atmosphere (e.g., 0.5 ppm) (in the absence of a hydrogen source such as a hydrogen leak) and may fluctuate over short periods (e.g., periods less than 1 s) because the hydrogen-derived water vapor signal is not affected by the gas dryer 122.

[0019] It should be noted that leaks in the system between the gas dryer 122 (or more specifically, the high pressure segment thereof) and the water vapor monitoring cell 152 can introduce water vapor variations that are not attenuated. Therefore, special measures can be taken to minimize and / or eliminate leaks that may exist in this area (e.g., using high quality vacuum piping elements in this area).

[0020] The converted sample gas leaves the water vapor monitoring cell 152 and passes again through the gas dryer 122, or more specifically, through its low pressure segment, in step 160. An optional bypass 162 may also be provided to avoid the low pressure segment.

[0021] In step 170 , the converted sample gas passes through a vacuum pump 172 which draws the sample gas through the hydrogen detector 102 and out an outlet 174 .

[0022] In parallel, in step 180, the water vapor signal from the water vapor monitoring cell 152 is received by a processor 182, which separates the water vapor signal into an ambient water vapor signal and a hydrogen-derived water vapor signal in the time domain, for example using digital signal processing (DSP) techniques. The processor 182 determines a hydrogen signal that describes the molecular hydrogen in the sample gas based on the hydrogen-derived water vapor signal. In some embodiments, the hydrogen-derived water vapor signal can simply be used as the hydrogen signal. In more complex embodiments, a conversion process can be employed to account for source or error or other factors.

[0023] Finally, in step 190, the processor 182 outputs the hydrogen signal, for example to be stored in memory, passed to another device, used to generate a display on a user interface of the hydrogen detector 102, etc.

[0024] The performance of the exemplary hydrogen detector 102 discussed with respect to Figures 1A and 1B can be improved by actively modulating the hydrogen-derived water vapor signal. Figure 2A is a flow diagram of an exemplary sequence 200 of steps for detecting molecular hydrogen according to a second embodiment. Figure 2B is a block diagram of an exemplary hydrogen detector 202 having components capable of implementing the sequence 200 of steps of Figure 2A. Where steps and components of Figures 2A and 2B are similar to those of Figures 1A and 1B, they will again be discussed only briefly and references are made to the above discussion for further details.

[0025] In step 210, the inlet 212 of the hydrogen detector 202 receives a sample gas (eg, air) that includes ambient water vapor, molecular hydrogen, and possibly hydrogen-containing molecules (including methane and NMHCs).

[0026] In step 220, the sample gas from inlet 212 is passed through a gas dryer 222, or more specifically, a high pressure segment thereof. Again, gas dryer 222 may be a Nafion™ sulfonated tetrafluoroethylene-based fluoropolymer copolymer membrane gas dryer or another type of dryer, whose primary purpose may be to dampen the time response in ambient water vapor while having little effect on the hydrogen.

[0027] In step 230, the sample gas from the gas dryer 222 (or more specifically, the high pressure segment thereof) is passed through a flow divider 224, which splits the sample gas in half, resulting in a first flow that is passed through the catalytic furnace 232 and is referred to herein as the "chemically converted flow," and a second flow that bypasses the catalytic furnace 232 and is referred to herein as the "bypass flow."

[0028] In step 240, the catalytic furnace 232 chemically converts the hydrogen in the chemical conversion stream to water vapor. Again, the catalytic furnace 232 may include a high temperature (e.g., 200° C.) catalytic surface (e.g., a Pt surface) that rapidly and quantitatively converts the hydrogen to water vapor. The gas dryer 222 and the catalytic furnace 232 may operate at near atmospheric pressure.

[0029] In step 250, the chemically converted stream from the catalytic furnace 232 is passed through a first flow controller 242 which reduces its pressure, and the bypass stream is passed through a second flow controller 244 which reduces its pressure. Again, these areas may be maintained at elevated temperatures (e.g., above 30° C.) to avoid condensation of water.

[0030] In step 260, the water vapor monitoring cell 252 alternates between measuring water vapor only in the chemically converted flow and only in the bypass flow to generate a water vapor signal. Again, the water vapor monitoring cell 252 may employ optical detection, such as laser spectroscopy or NDIR absorption spectroscopy. To alternate between measurements, a first valve 254 and a second valve 256 (e.g., an electronically controlled three-way valve) may be employed. In one embodiment, the first valve 254 accepts the chemically converted flow from the first flow controller 242 and directs it either to the water vapor monitoring cell 252 (in a dormant state) or to a bypass 258 surrounding the water vapor monitoring cell 252 (in an activated state). The second valve 256 accepts the bypass flow from the second flow controller 244 and directs it either around the water vapor monitoring cell 252 (in a dormant state) or to the water vapor monitoring cell 252 (in an activated state).

[0031] In a parallel step, in step 290, the processor 282 is configured to issue switching signals (e.g., square waves) to the first valve 254 and the second valve 256 to activate and deactivate them. This configuration allows the steam monitoring cell 252 to alternate between measuring water vapor in the chemically converted stream and measuring water vapor in the bypass stream while always maintaining flow through the water vapor monitoring cell 252 and the bypass 258 surrounding the water vapor monitoring cell 252. When the first valve 254 and the second valve 256 are switched simultaneously, the pressure in the steam monitoring cell 252 does not change significantly, avoiding transient signals from the switching process itself. Furthermore, the flow rates through the water vapor monitoring cell 252 and the bypass 258 surrounding the water vapor monitoring cell 252 do not need to be perfectly matched because their sum is constant, ensuring that the pressure in the water vapor monitoring cell 252 is approximately constant.

[0032] To reiterate, the water vapor signal generated by the water vapor monitoring cell 252 includes two components in the time domain: an ambient water vapor signal and a hydrogen-derived water vapor signal. However, due to the flow switching discussed above, the hydrogen-derived water vapor signal is modulated, making it easier to separate. The faster the switching signal to the valves 254, 256, the faster the modulation and the easier the separation (provided that the switching signal is still smaller (e.g., one tenth) than the measurement rate of the water vapor monitoring cell 252 to ensure resolution). In one embodiment, the switching signal is greater than 1 Hertz (Hz) (e.g., a 2 Hz square wave).

[0033] 2C is a graph 258 showing an example water vapor signal with a rapidly modulated hydrogen-derived water vapor component. In this example, the rapidly modulated hydrogen-derived water vapor component corresponds to about 50 ppm hydrogen and is dependent on the ambient water vapor component, which starts at about 500 ppm and slowly decreases to about 400 ppm. The hydrogen-derived water vapor signal component is well separated from the ambient water vapor component in the time domain. In an ideal system, a 50 ppm square wave would be expected to be dependent on the ambient water vapor component. However, due to mixing and surface effects in real-world implementations, a damped square wave is more typical.

[0034] In step 270, the streams are recombined and both pass through the gas dryer 222 (or more specifically, the low pressure segment thereof) again. An optional bypass 262 may also be provided to avoid the low pressure segment.

[0035] In step 280 , the recombined stream passes through a vacuum pump 272 which draws everything through the hydrogen detector 202 and out an outlet 274 .

[0036] In parallel, in step 295, the water vapor signal from the water vapor monitoring cell 252 is received by the processor 282, which separates the water vapor signal in the time domain into an ambient water vapor signal and a modulated hydrogen-derived water vapor signal. The processor 282 determines a hydrogen signal describing molecular hydrogen in the sample gas based on the modulated hydrogen-derived water vapor signal. In a simple embodiment, ignoring the decay of the modulation, the hydrogen signal can be determined as follows: [H2]=[H2O] cc -[H2O] bp Wherein, [HO] cc is the water vapor concentration measured when monitoring a chemical conversion stream, [H2O] bp is the water vapor concentration measured when monitoring the bypass flow. In more complex implementations, DSP techniques can be used. For example, the processor 282 can implement a digital lock-in amplifier to account for distortions caused by damping effects. Ambient water vapor fluctuations that are not completely suppressed by the gas dryer 222 are not phase coherent with the modulation frequency and thus can be easily suppressed.

[0037] Finally, in step 297, the processor 282 outputs the hydrogen signal, for example to be stored in memory, passed to another device, used to generate a display on a user interface of the hydrogen detector 202, etc.

[0038] The operation of the various embodiments can be improved with various refinements. In some refinements, ambient water vapor fluctuations can be further suppressed by humidifying the sample gas to a predetermined relative humidity (e.g., 99%) using a humidifier (not shown in FIG. 1B or FIG. 2B) before passing the sample gas through the gas dryer 122, 222. Humidifying the sample gas to a predetermined relative humidity eliminates the memory of the actual ambient water vapor concentration. The gas dryer 122, 222 reduces the water vapor to a constant, stable level so that the ambient water vapor signal does not fluctuate significantly, even when the actual ambient water vapor fluctuates.

[0039] Further refinements address hydrogen-containing molecules (including methane and NMHCs) in the sample gas that may generate interference signals by being converted to water vapor. In some refinements, hydrogen-containing molecules are suppressed by trapping using filters, membranes, molecular sieves, cryogenic traps, and / or other trapping elements. The trapping elements may include pre-filters that reduce water vapor and carbon dioxide concentrations (e.g., to less than 1 ppm) to avoid saturation of components intended to capture hydrogen-containing molecules. In some embodiments, the trapping elements may be placed between the gas dryer 122, 222 and the water vapor monitoring cell 152, 252. Although traps can be used with methane, traps may be particularly suitable for suppressing hydrogen NMHCs, since hydrogen NMHCs are much more sticky and usually less concentrated than hydrogen.

[0040] In a further refinement, the catalytic furnace 132, 232 can be adjusted to selectively oxidize hydrogen while avoiding conversion of hydrogen-containing molecules to water vapor. Selective oxidation can be particularly well suited to suppressing methane, as methane is relatively more difficult to oxidize than hydrogen, allowing parameters to be selected for the catalytic furnace 132, 232 that substantially oxidize one but not the other.

[0041] In yet a further refinement, the hydrogen-containing molecules in the sample gas can be compensated for by measuring the concentration of the hydrogen-containing molecules in the sample gas, calculating the amount of water vapor from the hydrogen-containing molecules based on the measured concentration of the hydrogen-containing molecules, and subtracting the water vapor from the hydrogen-containing molecules from the water vapor signal. Compensation-based techniques can be particularly suitable for dealing with methane.

[0042] Such measurements used in the compensation-based technique can be collected, for example, by adapting the techniques of Figures 2A and 2B. The total methane concentration can be measured in the bypass stream (e.g., using a methane gas detector (not shown in Figure 2B)). In the chemically converted stream, the methane concentration that has passed through the catalytic furnace 232 and survived is also measured (e.g., also using a methane concentration detector (not shown in Figure 2B)). The difference between the total methane concentration and the remaining methane concentration indicates the amount of methane oxidized in the catalytic furnace 232. The processor 282 can determine a hydrogen signal that describes the molecular hydrogen in the sample gas by subtracting the water vapor that originates from the oxidation of methane. Each oxidized methane molecule produces two water molecules, while an oxidized hydrogen molecule produces one water molecule. Thus, in a simple implementation, the hydrogen signal can be determined as follows: [H2] = ([H2O] cc -[H2O] bp )-s2 * ([CH4] bp -[CH4] cc ) In the formula, [HO] cc is the water vapor concentration measured when monitoring a chemical conversion stream, [H2O] bp is the water vapor concentration measured when monitoring the bypass flow, [CH4] cc is the methane concentration in the chemically converted stream, [CH4] bp is the methane concentration in the bypass stream. In more complex implementations, the hydrogen signal can be determined using DSP techniques (e.g., a digital lock-in amplifier) ​​to account for distortions caused by damping effects.

[0043] In summary, the above description provides an exemplary technique for rapid and sensitive detection of molecular hydrogen. It should be understood that various adaptations, modifications and extensions can be made to accommodate various design requirements and parameters. For example, the technique can be extended to determine hydrogen eddy covariance flux. An anemometer can be added to the hydrogen detector 102, 202 to measure air movement. The processor 182, 282 can be adapted to determine hydrogen eddy covariance flux based on a correlation between the air movement measurements and the water vapor signal.

[0044] In particular, it should be understood that the above description is intended to be illustrative only, and that the invention is not limited to the specific details of the exemplary embodiments disclosed. [Section 1] receiving a sample gas comprising ambient water vapor and hydrogen; passing the sample gas through a gas dryer; chemically converting hydrogen in the sample gas into water vapor to produce a converted sample gas; measuring water vapor in the converted sample gas to generate a water vapor signal; separating the water vapor signal in the time domain into an ambient water vapor signal and a hydrogen-derived water vapor signal, the gas dryer attenuating fluctuations in the ambient water vapor signal; outputting a hydrogen signal describing molecular hydrogen in the sample gas based on the hydrogen-derived water vapor signal; 16. A method for detecting molecular hydrogen, comprising: [Section 2] Item 3. The method according to item 1, wherein the gas dryer is a sulfonated tetrafluoroethylene-based fluoropolymer copolymer membrane gas dryer. [Section 3] Item 3. The method of item 1, wherein the chemically converting is performed by heating the sample gas in a catalytic furnace. [Section 4] Measuring the water vapor includes: optically detecting water vapor in the converted gas sample to generate the water vapor signal; The method according to item 1, comprising: [Section 5] Item 5. The method according to item 4, wherein the optical detection is performed using laser spectroscopy or non-dispersive infrared (NDIR) absorption spectroscopy. [Section 6] modulating the hydrogen derived water vapor signal; Further comprising: 2. The method of claim 1, wherein separating the ambient water vapor signal and the hydrogen-derived water vapor signal in the time domain is facilitated by the modulation of the hydrogen-derived water vapor signal. [Section 7] The modulating step comprises: splitting the sample gas after passing the sample gas through the gas dryer into a chemically converted stream and a bypass stream; alternating between measuring water vapor only in the chemically converted stream and measuring water vapor only in the bypass stream to generate the water vapor signal; Item 7. The method of item 6, further comprising: [Section 8] humidifying the sample gas to a predetermined relative humidity before passing the sample gas through the gas dryer; The method of claim 1, further comprising: [Section 9] suppressing hydrogen-containing molecules in the sample gas by trapping the hydrogen-containing molecules using at least one of a filter, a membrane, a molecular sieve, or a cryogenic trap; The method of claim 1, further comprising: [Section 10] suppressing hydrogen-containing molecules in the sample gas by adjusting the chemical conversion to selectively oxidize hydrogen while avoiding conversion of hydrogen-containing molecules to water vapor; The method of claim 1, further comprising: [Section 11] measuring a concentration of hydrogen-containing molecules in the sample gas, calculating an amount of water vapor derived from hydrogen-containing molecules based on the measured concentration of hydrogen-containing molecules, and compensating for hydrogen-containing molecules in the sample gas by subtracting the water vapor derived from hydrogen-containing molecules from the water vapor signal; The method of claim 1, further comprising: [Section 12] Measuring air movement; determining a hydrogen eddy covariance flux based on a correlation between the air movement measurements and the water vapor signal; and The method of claim 1, further comprising: [Section 13] receiving a sample gas comprising hydrogen; heating the sample gas in a catalytic furnace to chemically convert the hydrogen in the sample gas into water vapor; measuring water vapor in the converted sample gas to generate a water vapor signal; converting the water vapor signal into a hydrogen signal describing molecular hydrogen in the sample gas; 16. A method for detecting molecular hydrogen, comprising: [Section 14] Measuring the water vapor includes: optically detecting water vapor in the converted gas sample to generate the water vapor signal; Item 14. The method according to item 13, comprising: [Section 15] suppressing hydrogen-containing molecules in the sample gas using at least one of a filter medium, a membrane, a molecular sieve, or a cryogenic trap, or by adjusting the catalytic reactor to selectively oxidize hydrogen while avoiding conversion of hydrogen-containing molecules to water vapor; Item 14. The method of item 13, further comprising: [Section 16] measuring a concentration of hydrogen-containing molecules in the sample gas, calculating an amount of water vapor derived from hydrogen-containing molecules based on the measured concentration of hydrogen-containing molecules, and compensating for hydrogen-containing molecules in the sample gas by subtracting the water vapor derived from hydrogen-containing molecules from the water vapor signal; Item 14. The method of item 13, further comprising: [Section 17] an inlet configured to receive a sample gas comprising ambient water vapor and hydrogen; a gas dryer having a segment configured to receive a sample gas from the inlet; a catalytic furnace configured to receive the sample gas from the gas dryer and chemically convert hydrogen in the sample gas to water vapor to produce a converted sample gas; a water vapor monitoring cell configured to measure water vapor in the converted sample gas to generate a water vapor signal; a processor configured to separate the water vapor signal in the time domain into an ambient water vapor signal and a hydrogen-derived water vapor signal, and to output a hydrogen signal describing molecular hydrogen in the sample gas based on the hydrogen-derived water vapor signal; A molecular hydrogen detector comprising: [Section 18] Item 18. The molecular hydrogen detector according to item 17, wherein the gas dryer is a sulfonated tetrafluoroethylene-based fluoropolymer copolymer membrane gas dryer. [Section 19] 20. The method of claim 17, wherein the water vapor monitoring cell comprises a laser spectrometer or a non-dispersive infrared (NDIR) absorption spectrometer. [Section 20] a flow controller disposed between the catalytic furnace and the water vapor monitoring cell and configured to reduce a pressure of the converted sample gas; a vacuum pump configured to draw a sample gas through the gas dryer, the catalytic furnace, and the water vapor monitoring cell; Item 18. The molecular hydrogen detector according to item 17, further comprising: [Section 21] a flow splitter disposed after the gas dryer and the catalytic furnace and configured to split the sample gas into a chemically converted stream that is passed through the catalytic furnace and a bypass stream that bypasses the catalytic furnace; a first valve configured to selectively direct the chemically converted stream after passing through the catalytic reactor to or by-pass the water vapor monitoring cell; a second flow valve configured to selectively direct the bypass flow to or around the water vapor monitoring cell; Further comprising: the processor is configured to activate and deactivate the first valve and the second valve to cause the water vapor monitoring cell to alternately measure water vapor in only the chemically converted stream and measure water vapor in only the bypass stream to generate the water vapor signal. Item 18. A molecular hydrogen detector according to item 17. [Section 22] Item 18. The molecular hydrogen detector of item 17, further comprising a humidifier configured to bring the sample gas to a predetermined relative humidity. [Section 23] a filter medium, membrane, molecular sieve, or cryogenic trap configured to suppress hydrogen-containing molecules in the sample gas; Item 18. The molecular hydrogen detector according to item 17, further comprising: [Section 24] 20. The molecular hydrogen detector of claim 17, wherein the catalytic reactor is configured to selectively oxidize hydrogen while avoiding conversion of hydrogen-containing molecules to water vapor. [Section 25] a monitor configured to measure a concentration of hydrogen-containing molecules in the sample gas, and the processor is configured to calculate an amount of water vapor derived from hydrogen-containing molecules based on the measured concentration of hydrogen-containing molecules and compensate for hydrogen-containing molecules in the sample gas by subtracting the water vapor derived from hydrogen-containing molecules from the water vapor signal. Item 18. A molecular hydrogen detector according to item 17.

Claims

1. receiving a sample gas comprising ambient water vapor and hydrogen; passing the sample gas through a gas dryer configured to attenuate a time response of ambient water vapor in the sample gas; chemically converting hydrogen in the sample gas into water vapor to produce a converted sample gas; measuring water vapor in the converted sample gas to generate a water vapor signal; separating the water vapor signal in the time domain into an ambient water vapor signal and a hydrogen-derived water vapor signal, the dampened time response of the gas dryer facilitating separation by distinguishing the ambient water vapor signal from the more rapidly varying hydrogen-derived water vapor signal; outputting a hydrogen signal describing molecular hydrogen in the sample gas based on the hydrogen-derived water vapor signal; 16. A method for detecting molecular hydrogen, comprising:

2. The method of claim 1 , wherein the gas dryer is a sulfonated tetrafluoroethylene based fluoropolymer copolymer membrane gas dryer.

3. The method of claim 1 , wherein the chemically converting is performed by heating the sample gas in a catalytic furnace.

4. Measuring the water vapor includes: optically detecting water vapor in the converted gas sample to generate the water vapor signal; The method of claim 1 , comprising:

5. The method of claim 4 , wherein the optically detecting is performed using laser spectroscopy or non-dispersive infrared (NDIR) absorption spectroscopy.

6. modulating the hydrogen derived water vapor signal; Further comprising: The method of claim 1 , wherein separating the ambient water vapor signal and the hydrogen-derived water vapor signal in the time domain is facilitated by the modulation of the hydrogen-derived water vapor signal.

7. The modulating step comprises: splitting the sample gas after passing the sample gas through the gas dryer into a chemically converted stream and a bypass stream; alternating between measuring water vapor only in the chemically converted stream and measuring water vapor only in the bypass stream to generate the water vapor signal; The method of claim 6 further comprising:

8. humidifying the sample gas to a predetermined relative humidity before passing the sample gas through the gas dryer; The method of claim 1 further comprising:

9. suppressing hydrogen-containing molecules in the sample gas by trapping the hydrogen-containing molecules using at least one of a filter, a membrane, a molecular sieve, or a cryogenic trap; The method of claim 1 further comprising:

10. suppressing hydrogen-containing molecules in the sample gas by adjusting chemical conversions to selectively oxidize hydrogen while avoiding conversion of hydrogen-containing molecules to water vapor; The method of claim 1 further comprising:

11. measuring a concentration of hydrogen-containing molecules in the sample gas, calculating an amount of water vapor derived from hydrogen-containing molecules based on the measured concentration of hydrogen-containing molecules, and compensating for hydrogen-containing molecules in the sample gas by subtracting the water vapor derived from hydrogen-containing molecules from the water vapor signal; The method of claim 1 further comprising:

12. Measuring air movement; determining a hydrogen eddy covariance flux based on a correlation between the air movement measurements and the water vapor signal; and The method of claim 1 further comprising:

13. an inlet configured to receive a sample gas comprising ambient water vapor and hydrogen; a gas dryer having a segment configured to receive a sample gas from the inlet and to dampen a time response of ambient water vapor in the sample gas; a catalytic furnace configured to receive the sample gas from the gas dryer and chemically convert hydrogen in the sample gas to water vapor to produce a converted sample gas; a water vapor monitoring cell configured to measure water vapor in the converted sample gas to generate a water vapor signal; a processor configured to separate the water vapor signal into an ambient water vapor signal and a hydrogen-derived water vapor signal in the time domain, the separation being facilitated by distinguishing the ambient water vapor signal from the more rapidly varying hydrogen-derived water vapor signal based on a damped time response by the gas dryer, and to output a hydrogen signal describing molecular hydrogen in the sample gas based on the hydrogen-derived water vapor signal.

14. The molecular hydrogen detector of claim 13 , wherein the gas dryer is a sulfonated tetrafluoroethylene-based fluoropolymer copolymer membrane gas dryer.

15. The molecular hydrogen detector of claim 13 , wherein the water vapor monitoring cell comprises a laser spectrometer or a non-dispersive infrared (NDIR) absorption spectrometer.

16. a flow controller disposed between the catalytic furnace and the water vapor monitoring cell and configured to reduce a pressure of the converted sample gas; a vacuum pump configured to draw a sample gas through the gas dryer, the catalytic furnace, and the water vapor monitoring cell; The molecular hydrogen detector of claim 13 further comprising:

17. a flow splitter disposed after the gas dryer and the catalytic furnace and configured to split the sample gas into a chemically converted stream that is passed through the catalytic furnace and a bypass stream that bypasses the catalytic furnace; a first valve configured to selectively direct the chemically converted stream after passing through the catalytic reactor to or by-pass the water vapor monitoring cell; a second valve configured to selectively direct the bypass flow to or around the water vapor monitoring cell; Further comprising: the processor is configured to activate and deactivate the first valve and the second valve to cause the water vapor monitoring cell to alternately measure water vapor in only the chemically converted stream and measure water vapor in only the bypass stream to generate the water vapor signal.

14. A molecular hydrogen detector according to claim 13.

18. 14. The molecular hydrogen detector of claim 13, further comprising a humidifier configured to bring the sample gas to a predetermined relative humidity.

19. a filter medium, membrane, molecular sieve, or cryogenic trap configured to suppress hydrogen-containing molecules in the sample gas; The molecular hydrogen detector of claim 13 further comprising:

20. The molecular hydrogen detector of claim 13 , wherein the catalytic reactor is configured to selectively oxidize hydrogen while avoiding conversion of hydrogen-containing molecules to water vapor.

21. a monitor configured to measure a concentration of hydrogen-containing molecules in the sample gas; the processor is configured to calculate an amount of water vapor derived from hydrogen-containing molecules based on the measured hydrogen-containing molecule concentration, and to compensate for hydrogen-containing molecules in the sample gas by subtracting the water vapor derived from hydrogen-containing molecules from the water vapor signal.

14. A molecular hydrogen detector according to claim 13.

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