Assessment of sensors for the real-time detection of catalytic methane pyrolysis

Methane pyrolysis has been a topic of research in both energy technology and aerospace propulsion. Various aspects such as heat transfer, catalytic materials and chemical kinetics as well as carbon deposition behaviour have been in focus. However, the temporal behaviour of pyrolysis and carbon deposition has received relatively little attention. Considering the effect of maintenance on programme costs, it is important to have sensors with good time resolution both in the laboratory and in operational systems. Therefore, it is of interest to investigate the efficacy of real-time sensors that have the potential for integration into systems with real-world applications. Speed of Sound (SoS) transducers and Thermal Conductivity Gauges (TCG) have the potential to produce high-quality measurements at relatively low cost and in a compact form factor; however, they have not yet been demonstrated in this research area. Therefore, the current work assesses their performance compared to gas chromatography (GC), using a newly developed experimental setup. It is shown, for the conditions tested, that real-time and in-flow SoS and TCG sensors can attain measurement quality comparable to that of the GC used; however, this performance is implementation dependent. Specifically, PCB based TCG and Time-of-Flight based SoS measurements are found to be highly effective in capturing the dynamic characteristics of the methane pyrolysis process. Although the current indication is promising, further work is necessary to test the approach under representative operational conditions specific to, for example, aerospace propulsion applications. • The capability of real-time sensors, based on speed of sound and thermal conductivity, for the detection of methane pyrolysis is experimentally tested and analysed. • A new setup has been designed and tested for the characterization of catalytic methane pyrolysis on candidate materials for aerospace applications. This setup uses inductive heating to achieve heat transfer from the hot sample material to the gas in order to avoid bulk auto-pyrolysis of the methane gas, which aids in the assessment of catalytic pyrolysis. • A high level of automation is implemented in the test setup in order to facilitate consistent measurements.