CN-122029425-A - Optical detector employing controlled water vapor concentration over catalyst

Abstract

In various embodiments, very high speed and very high sensitivity hydrogen detection is achieved by controlling the concentration of water vapor over a catalyst for converting hydrogen in a sample gas (e.g., ambient air) to water vapor to provide a substantially stable water vapor mixing level at a target mixing ratio. Naturally occurring water vapor in the sample gas will typically vary over a wide range over time without further steps (e.g., due to varying atmospheric conditions). By controlling the level of water vapor over the catalyst to be substantially equal to the target mixing ratio, which is not too low to compromise response time and not too high to compromise sensitivity, very high speeds and very high sensitivity can be provided.

Inventors

• D. D. Little Nielsen
• S. C. Herndon
• SCHOTT JOHN H.
• J. R. Rossioli
• E. M. Lenny
• WARE ROBERT A

Assignees

• 重航空器研究公司

Dates

Publication Date

20260512

Application Date

20241106

Priority Date

20231201

Claims (20)

1. 1. A method for detecting molecular hydrogen, comprising: Receiving a sample gas comprising naturally occurring water vapor and sample molecular hydrogen; Controlling the level of water vapor in the sample gas to be substantially equal to a target mixing ratio, wherein the target mixing ratio is selected to be a value between parts per million (ppm) and 60 ppm; Converting hydrogen in the sample gas to additional water vapor to produce a converted sample gas; Measuring the water vapor in the converted sample gas to generate a water vapor signal; Separating the water vapor signal into a controlled water vapor signal describing the controlled water vapor and a sample hydrogen-derived water vapor signal describing the sample hydrogen-derived water vapor, and Outputting a hydrogen signal describing sample molecular hydrogen in the sample gas, the hydrogen signal being based on the sample hydrogen-derived water vapor signal.
2. 2. The method of claim 1, wherein the target blend ratio is selected to be a value between 3 ppm and 30 ppm.
3. 3. The method of claim 1, wherein the controlling the level of water vapor in the sample gas is performed by water reduction, and the water reduction comprises: Drying the sample gas; Comparing the measured water vapor mixture ratio with the target mixture ratio, and The amount of drying applied to the sample gas is adjusted based on the comparison until the target mixing ratio is achieved.
4. 4. The method of claim 1, wherein the controlling the level of water vapor in the sample gas is performed by water addition, and the water addition comprises: drying the sample gas to produce a dried sample gas; Comparing the measured water vapor mixture ratio with the target mixture ratio, and The amount of moisture mixed into the dry sample gas is adjusted based on the comparison until the target mixing ratio is achieved.
5. 5. The method of claim 1, wherein the controlling the level of water vapor in the sample gas is performed by hydrogen addition, and the hydrogen addition comprises: drying the sample gas to produce a dried sample gas, and Adding to said dry sample gas a quantity of a mixture of hydrogen-containing or hydrogen-containing water-convertible substances, Wherein the converting also converts the hydrogen or hydrogen-containing water-convertible substance in the mixture to a controlled water vapor to achieve the target mixing ratio.
6. 6. The method of claim 5, wherein the drying the sample gas to produce a dried sample gas is performed prior to the converting.
7. 7. The method of claim 6, wherein the drying is performed after the amount of the mixture is added to the sample gas.
8. 8. The method of claim 5, wherein the mixing ratio of hydrogen or hydrogen-containing water-convertible substances in the mixture is substantially 2000 parts per million (ppm), the flow rate of the sample gas is substantially 1 standard liter per minute (slpm), and the flow rate of the mixture is substantially 0.01 slpm.
9. 9. The method of claim 1, wherein the damping time response is performed by a gas dryer, the converted hydrogen is performed by a catalyst in a catalytic furnace, and the measuring of water vapor in the converted sample gas is performed by an optical detection cell using optical absorption spectroscopy.
10. 10. A molecular hydrogen detector comprising: An inlet configured to receive a sample gas comprising naturally occurring water vapor and sample molecular hydrogen; a gas dryer configured to dry the sample gas; A flow controller configured to add an amount of moisture to the sample gas or to add an amount of hydrogen-containing or hydrogen-containing water-convertible substance mixture to the sample gas to produce a controlled water vapor such that a level of controlled water vapor in the sample gas is substantially equal to a target mixing ratio; A catalytic furnace comprising a catalyst configured to convert hydrogen in the sample gas to water vapor to produce a converted sample gas; An optical detection cell configured to measure water vapor in the converted sample gas using optical absorption spectroscopy to generate a water vapor signal, and A processor configured to separate the water vapor signal into a controlled water vapor signal describing the controlled water vapor and a sample hydrogen-derived water vapor signal describing sample hydrogen-derived water vapor, and to output a hydrogen signal describing sample molecular hydrogen in the sample gas, the hydrogen signal being based on the sample hydrogen-derived water vapor signal.
11. 11. The molecular hydrogen detector of claim 10, wherein the target mixing ratio is selected to be a value between 3 ppm and 30 ppm.
12. 12. The molecular hydrogen detector of claim 10, further comprising: one or more molecular sieves configured to also dry the sample gas.
13. 13. The molecular hydrogen detector of claim 10, wherein the flow controller is configured to add the amount of the mixture of hydrogen-containing or hydrogen-containing water-convertible substance to the sample gas such that a level of controlled water vapor in the sample gas is substantially equal to the target mixing ratio, and the catalyst is further configured to convert the hydrogen or the hydrogen-containing water-convertible substance in the mixture to controlled water vapor in the converted sample gas.
14. 14. A method for detecting molecular hydrogen, comprising: Receiving a sample gas comprising naturally occurring water vapor and sample molecular hydrogen; Drying the sample gas; Adding to the sample gas an amount of a mixture of hydrogen-containing or hydrogen-containing water-convertible substances; Converting hydrogen in the sample gas to water vapor to produce a converted sample gas having a level of controlled water vapor substantially equal to a target mixing ratio, wherein the converting converts the sample molecular hydrogen and hydrogen or hydrogen-containing water-convertible substance contained in the added mixture to water vapor and the hydrogen or hydrogen-containing water-convertible substance in the added mixture to controlled water vapor; Measuring the water vapor in the converted sample gas to generate a water vapor signal; separating the water vapor signal into a controlled water vapor signal describing the controlled water vapor and a sample hydrogen-derived water vapor signal describing a sample hydrogen-derived water vapor, and Outputting a hydrogen signal describing sample molecular hydrogen in the sample gas, the hydrogen signal being based on the sample hydrogen-derived water vapor signal.
15. 15. The method of claim 14, wherein the target blend ratio is selected to be a value between 3 ppm and 30 ppm.
16. 16. The method of claim 14, wherein the drying the sample gas is performed prior to the converting.
17. 17. The method of claim 16, wherein the drying the sample gas is performed after adding the amount of the mixture to the sample gas.
18. 18. The method of claim 14, wherein the mixing ratio of hydrogen or hydrogen-containing water-convertible substances in the mixture is substantially 2000 parts per million (ppm), the flow rate of the sample gas is substantially 1 standard liter per minute (slpm), and the flow rate of the mixture is substantially 0.01 slpm.
19. 19. The method of claim 14, wherein the drying is performed by a gas dryer, the converting hydrogen is performed by a catalyst in a catalytic furnace, and the measuring the water vapor in the converted sample gas is performed by an optical detection cell using optical absorption spectroscopy.
20. 20. A molecular hydrogen detector comprising: Means for receiving a sample gas comprising naturally occurring water vapor and sample molecular hydrogen; means for drying the sample gas; Means for adding an amount of a hydrogen-containing or hydrogen-containing water-convertible substance mixture to the sample gas; Means for converting hydrogen in the sample gas to water vapor to produce a converted sample gas having a level of controlled water vapor substantially equal to a target mixing ratio, wherein the means for converting is configured to convert the sample molecular hydrogen and hydrogen or hydrogen-containing water-convertible substance contained in an added mixture to water vapor, and the hydrogen or hydrogen-containing water-convertible substance in the added mixture to controlled water vapor; means for measuring water vapor in the converted sample gas to generate a water vapor signal, and Means for separating the water vapor signal into a controlled water vapor signal describing the controlled water vapor and a sample hydrogen-derived water vapor signal describing sample hydrogen-derived water vapor, and for outputting a hydrogen signal describing sample molecular hydrogen in the sample gas, the hydrogen signal being based on the sample hydrogen-derived water vapor signal.

Description

Optical detector employing controlled water vapor concentration over catalyst Technical Field The present disclosure relates generally to gas detection and, more particularly, to detection of molecular hydrogen. Background As the world is gradually no longer converting fossil fuels into our primary energy, a hydrogen-based energy infrastructure will likely emerge. For economic, safety and environmental reasons, it would be of paramount importance to have an efficient method of detecting molecular hydrogen (H 2). For example, in order to detect hydrogen leaks early before they can cause significant safety issues, it would be critical to have an effective method of detecting molecular hydrogen in a sample gas (e.g., ambient air). Optical absorption spectroscopy (e.g., laser absorption spectroscopy, non-dispersive infrared (NDIR) absorption spectroscopy, etc.) is a powerful technique for quantifying many small molecules. However, molecular hydrogen is difficult to detect directly using optical absorption spectroscopy because hydrogen has no rotational spectrum, only a very weak vibrational spectrum, and has electronic transitions only at very short and unavailable wavelengths. To overcome this challenge, a technique for indirectly detecting hydrogen using optical absorption spectroscopy has been developed. Some of these techniques first use a catalyst to convert molecular hydrogen in a sample gas (e.g., ambient air) to water vapor, and then use the water vapor as a substitute for hydrogen to detect the water vapor. In this context, molecular hydrogen in the raw sample gas is referred to as "sample molecular hydrogen", and water vapor generated from molecular hydrogen in the raw sample gas is referred to as "sample hydrogen-derived water vapor". Sample gas (e.g., ambient air) typically includes some water vapor, which is a product of the natural environment or is produced by sources other than the molecular hydrogen being measured (collectively referred to herein as "naturally occurring water vapor"). Fortunately, techniques have been developed that can distinguish between naturally occurring water vapor and sample hydrogen-derived water vapor. There is an increasing desire by the environmental researchers and energy industries for higher speed and more sensitive techniques for measuring molecular hydrogen. However, unexpected challenges are encountered when attempting to achieve very high speeds and very high sensitivity with detectors that rely on the conversion of molecular hydrogen to water vapor. In this context, the term "very high velocity" refers to a response time of less than or equal to 10 seconds, while "very high sensitivity" refers to the ability to detect concentrations of less than or equal to ten parts per billion (ppb). There appears to be a tension between achieving very high speeds and very high sensitivities. It is not yet understood why this occurs and what, if any, can be done to enable very high speed and very high sensitivity detection to be achieved continuously. As a result, existing methods do not provide the type of molecular hydrogen detection required for quantification and thus minimize many types of hydrogen leakage, including leakage into the atmosphere. Thus, there is an improved technique for hydrogen detection that can continuously achieve very high speed and very high sensitivity. Disclosure of Invention In various embodiments, very high speed and very high sensitivity molecular hydrogen detection is achieved by controlling the concentration of water vapor over a catalyst for converting sample molecular hydrogen to water vapor so as to provide a substantially stable water vapor mixing level at a target mixing ratio. Naturally occurring water vapor in the sample gas (without further steps) will typically vary over a wide range over time (e.g., due to varying atmospheric conditions). By controlling the level of water vapor over the catalyst to be substantially equal to the target mixing ratio, which is not too low to compromise response time and not too high to compromise sensitivity, very high speeds and very high sensitivity can be provided. In various embodiments, the target blend ratio is selected to be a value between 1 ppm and 60 ppm, and preferably between 3 ppm and 30 ppm, for example 10 ppm. The targeted mixing ratio may be achieved in a number of different ways. In some embodiments, the target mixing ratio is achieved by water reduction. In the water reduction method, water vapor is precisely removed from a sample gas (e.g., ambient air) in order to achieve a controlled level of water vapor at a target mixing ratio. As used herein, the term "controlled water vapor" refers to the product of the natural environment or water vapor produced from sources other than the sample molecular hydrogen that is being managed or controlled. In other embodiments, the target mixing ratio is achieved by water addition. In the water addition method, substantially all of the water vapo