The transformative role of tunable diode laser spectroscopy

Produced through electrolysis using renewable energy sources, green hydrogen holds immense potential to revolutionise multiple sectors, including transportation, energy storage, and industrial processes. However, reliable and efficient production of green hydrogen requires precise monitoring and control of the entire process. In this regard, gas analysers play a pivotal role, ensuring the quality, safety, and efficiency of hydrogen production in green hydrogen plants. This article explores the applications and significance of gas analysers in facilitating the transition to a greener and more sustainable future. There are two major fields of application for online gas analysers in green hydrogen production plants, both of which will be discussed.

Monitoring the electrolysis process

Gas analysers prove indispensable in monitoring the electrolysis process. They help in analysing the composition and purity of the hydrogen and oxygen streams, ensuring optimal electrolysis reaction and supporting plant safety monitoring. These analysers continuously measure the levels of hydrogen, oxygen, and water vapour, providing real-time data to operators. By monitoring and controlling these parameters, the analysers assist in maintaining the desired efficiency, preventing system failures, and optimising energy consumption.

Controlling impurity levels

One of the critical aspects of green hydrogen production is maintaining high purity levels throughout the process. Gas analysers allow for the accurate measurement and detection of impurities in line with the ISO 14687:2019 (hydrogen fuel quality – product specification) and 19880-8 (hydrogen fuel quality control). In fuel cells, contaminants can temporarily or permanently disable sites for catalytic separation of hydrogen, impede proton transport, or dilute hydrogen fuel and reduce efficiency. Key components that require continuous monitoring online include trace oxygen and moisture in pure hydrogen. Nitrogen measurement can also be required as the gas can be used to inert the electrolyser in the shut-down phase, and can potentially remain present during the restart of the electrolyser.

Conventional (legacy) approach

The aforementioned gases are traditionally measured using extractive methods, which extract the gas from the process to carry out an adhoc sample preparation. When the sample is under conditions within the analyser specifications, the sampling line will convey this sample to the analyser measurement chamber, where the relevant technology is applied.

For the percentage of oxygen, the most commonly used method is paramagnetic. It is carried out using the magnetic property of the di-oxygen molecule. There are devices which measure a differential pressure, ensuring the process gas is never in contact with the sensors, avoiding potential contamination. Other techniques include the dumbbell effect principle, which is more subject to vibrations, and electrochemical-based sensors with a limited lifetime, which is subject to drift and interference.

Written by Frederic Thielland, David Janssens and Sebastian Fischer, Siemens, Germany.

This article was originally published in the Winter 2023 issue of Global Hydrogen Review magazine. To read the full article, simply follow this link.

Read the article online at: https://www.globalhydrogenreview.com/special-reports/27122023/the-transformative-role-of-tunable-diode-laser-spectroscopy/