Trace Water Vapor Analysis in Specialty Gases: Sensor and Spectroscopic Approaches

Geiger, W. M.; Raynor, Mark W.; Bertness, Kristine A.; Cossel, Kevin C.; Adler, Florian; Ye, J.

doi:10.1002/9781118642771.ch7

Cited by 9 publications

(15 citation statements)

References 105 publications

(140 reference statements)

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“…Phosphorus pentoxide cells are used in the electrolysis of water vapor. This method is often considered to be a primary measurement method [23]. Electrodes are coated with a thin film of phosphorus pentoxide (P 2 O 5 ).…”

Section: Phosphorus Pentoxide Moisture Sensormentioning

confidence: 99%

“…The gold layer is permeable to moisture and conductive. Water vapor in the gas stream is transported rapidly through the gold layer and equilibrates in the aluminum oxide pore walls, affecting the dielectric constant of the material and as a result, the capacitance of the unit [23]. The sensor is capable of both µmol/mol and dew point measurements in most industrial gas streams, including hydrogen.…”

Section: Aluminium Oxide Moisture Sensormentioning

confidence: 99%

“…Chilled-mirror hygrometers operate by directly measuring the dew-point temperature (the temperature to which a volume of gas must be cooled at constant pressure to become saturated with water vapor) of a gas stream [23]. Consequently, any cooling below the dew-point temperature causes the excess water to condense, and this can then be detected optically on a mirror surface.…”

Section: Chilled-mirror Hygrometermentioning

confidence: 99%

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Detection of Contaminants in Hydrogen Fuel for Fuel Cell Electrical Vehicles with Sensors—Available Technology, Testing Protocols and Implementation Challenges

et al. 2021

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Europe’s low-carbon energy policy favors a greater use of fuel cells and technologies based on hydrogen used as a fuel. Hydrogen delivered at the hydrogen refueling station must be compliant with requirements stated in different standards. Currently, the quality control process is performed by offline analysis of the hydrogen fuel. It is, however, beneficial to continuously monitor at least some of the contaminants onsite using chemical sensors. For hydrogen quality control with regard to contaminants, high sensitivity, integration parameters, and low cost are the most important requirements. In this study, we have reviewed the existing sensor technologies to detect contaminants in hydrogen, then discussed the implementation of sensors at a hydrogen refueling stations, described the state-of-art in protocols to perform assessment of these sensor technologies, and, finally, identified the gaps and needs in these areas. It was clear that sensors are not yet commercially available for all gaseous contaminants mentioned in ISO14687:2019. The development of standardized testing protocols is required to go hand in hand with the development of chemical sensors for this application following a similar approach to the one undertaken for air sensors.

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Section: Phosphorus Pentoxide Moisture Sensormentioning

confidence: 99%

Section: Aluminium Oxide Moisture Sensormentioning

confidence: 99%

Section: Chilled-mirror Hygrometermentioning

confidence: 99%

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Detection of Contaminants in Hydrogen Fuel for Fuel Cell Electrical Vehicles with Sensors—Available Technology, Testing Protocols and Implementation Challenges

et al. 2021

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“…Hardly any sensor except humidity, touches human life so much to meet its increasing demand in day to day life. Highly accurate and reliable moisture detection, in different environments, has become more and more important for environmental protection, technological processes, scientific R&D work, natural gas processing, healthcare, pharmaceutical industries, semiconductors, and food processing industries. − Trace level detection is notoriously challenging due to the adsorption affinity of water on metal and other surfaces, along with potential interference from different gas moieties in the measurement process.…”

Section: Introductionmentioning

confidence: 99%

“…These sensors are robust and fairly inexpensive and are extensively used in inert or nonreactive gas matrices . The technology currently being used for measuring moisture at the trace level mostly includes spectroscopic methods: viz., tunable diode laser absorption spectroscopy, Fourier transform infrared spectroscopy, and chilled mirror technology. , However, a sensor-based technology that has appeared successfully in this regime is the capacitive metal oxide sensor; it has the potential to revolutionize the sensing domain, if exploited using new ideas and upcoming trends in technologies.…”

Section: Introductionmentioning

confidence: 99%

New Concept in Humidity Sensing: Role of Molecular Brownian Energy and Probabilistic Mean Free Path to differentiate RH- and Trace Level Detection

Sharma

Alam

Islam

2020

ACS Appl. Mater. Interfaces

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A break in the traditional pore morphology approach in anodic alumina is presented here to see its niche merit over the conventional sensors for water vapor detection. The cylindrical pore structure was replaced with a normal cone for trace-level and inverse cone for RH-level detection. The normal conical pore was fabricated by sheer manipulation of the reaction rates of electrolytes, anodic polarization, rate and time; the procedure was reversed in the case of the inverse cone structure. A sensor with a normal cone geometry exhibits excellent response at the ppm level and slightly extended to low RH level with a detection range of 120 ppm–30% RH, having response and recovery times of 6 and 255 s, measured at 120 ppm. Lowering of the minimum detection limit further requires alteration of the conical geometric parameters, in tandem with the molecular dynamics of water vapor molecules within the pore. In contrast, a sensor developed from an inverse conical structure shows response only at the RH level, from 20% RH to 90% RH with response and recovery times of less than 60 s over the entire range. Limitations such as nonlinear response, large response-recovery time, and high hysteresis as observed in conventional anodic alumina-based humidity sensors have been removed. The sensor response in conical and inverse conical pore morphologies is compared with that of standard sensors having a cylindrical pore morphology, with a top pore diameter identical with that of the reported sensors. The standard sensors were found to detect in the RH range only, with response and recovery times below 20s. The sensing mechanisms in both structures have been suitably demonstrated and ratified with experimental data. Trace level detection is interpreted with the statistical probabilistic approach in the light of the kinetic theory of gases and Brownian energy. A correlation between top surface pore diameter (through which water molecules enter) and the optimized mean free path of vapor molecule is established, and its effectiveness has been demonstrated for humidity detection at a trace level. The results are encouraging, and the same concept may be tried for the detection of other gaseous stimuli, including organic vapors.

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Direct Absorption and Photoacoustic Spectroscopy for Gas Sensing and Analysis: A Critical Review

Fathy

Sabry

Hunter

et al. 2022

Laser & Photonics Reviews

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Optical spectroscopy has a broad scientific basis in chemistry, physics, and material science, with diverse applications in medicine, pharmaceuticals, agriculture, and environmental monitoring. Fourier transform infrared (FTIR) spectrometers and tunable laser spectrometers (TLS) are key devices for measuring optical spectra. Superior performance in terms of sensitivity, selectivity, accuracy, and resolution is required for applications in gas sensing. This review deals with gas measurement based on either direct optical absorption spectroscopy or photoacoustic spectroscopy. Both approaches are applicable to FTIR spectroscopy or TLS. In photoacoustic spectroscopy, cantilever-based photoacoustic spectroscopy is focused due its high performance. A literature survey is conducted revealing the recent technological advances. Theoretical fundamental detection limits are derived for TLS and FTIR, considering both direct absorption and photoacoustic spectroscopies. A theoretical comparison reveals which technology performs better. The minimum normalized absorption coefficient and normalized noise equivalent absorption coefficient appear as key parameters for this comparison. For TLS-based systems, direct absorption spectroscopy is found to be the best for lower laser power and longer path length. For FTIR-based systems, direct absorption is found to be the best for low temperature sources, higher spectrometer throughput, faster mirror velocity, and longer gas cells.

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Trace Water Vapor Analysis in Specialty Gases: Sensor and Spectroscopic Approaches

Abstract: Manufacturers and product names are given solely for completeness. These specific citations neither constitute an endorsement of the product nor imply that similar products from other companies would be less suitable.

Cited by 9 publications

References 105 publications

Detection of Contaminants in Hydrogen Fuel for Fuel Cell Electrical Vehicles with Sensors—Available Technology, Testing Protocols and Implementation Challenges

Detection of Contaminants in Hydrogen Fuel for Fuel Cell Electrical Vehicles with Sensors—Available Technology, Testing Protocols and Implementation Challenges

New Concept in Humidity Sensing: Role of Molecular Brownian Energy and Probabilistic Mean Free Path to differentiate RH- and Trace Level Detection

Direct Absorption and Photoacoustic Spectroscopy for Gas Sensing and Analysis: A Critical Review

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