The reduction of greenhouse gas emissions - including CO2 and methane - is envisaged through the use of hydrogen instead of natural gas or even liquid fossil fuels. The production, storage and use of hydrogen from renewable energy sources is currently one of the challenges facing the mastery of green energies:
- During its production and storage phases, hydrogen, due to its very low collision cross-section, is quick to diffuse through materials, and so a rise in hydrogen levels in the atmosphere is expected if its use as a green energy carrier becomes widespread. This effect poses a problem for air quality, by modifying the reaction processes of atmospheric compounds. This may even run counter to the benefits of reducing greenhouse gases by replacing fossil fuels with hydrogen, by modifying the formation/consumption pathways of these greenhouse gases.
- In addition, hydrogen is known for its low-energy ignition hazard and its potential to transition from a deflagration to a detonation highly damaging to both infrastructure and people. Hydrogen's flammability limits are difficult to measure in any location or situation.
- Hydrogen combustion is well known for high temperatures, in excess of 600°C. However, for very low intermediate combustion temperatures, between 150 and 600°C, experimental data are almost non-existent. An excellent understanding of combustion phenomena in this temperature range is essential for accurate risk assessment, as well as for the efficient design of combustion systems.
These issues overlap: atmospheric chemistry and combustion are based on the same scientific foundations, with shared chemical reactions, thermodynamic equilibria and transport properties. However, temperature and pressure conditions differ. The challenge is to know precisely the rate constants, thermodynamic data and transport data of the chemical species involved over very wide temperature and pressure ranges, so as to be able to predict the reactivity and influence of hydrogen through detailed kinetic models.
The Physical Chemistry of Combustion Processes and the Atmosphere Laboratory has been a center of expertise for 40 years on atmospheric reactions and combustion conditions. In 2023, the laboratory's combustion teams are involved in the PEPR hydrogène "Understanding and MOdeling NOx formation in Turbulent HYdrogen flames" (MONTHY) and are collaborating with members of the PEPR hydrogène "Améliorer les connaissances en matière de sécurité pour les mesures/modélisations de l'hydrogène en phase cryogénique" (ESKYMO) through a detailed kinetic model transfer. In addition, a partnership with General Electric has been set up to measure auto-ignition times of pure hydrogen or hydrogen mixed with natural gas over intermediate combustion temperature ranges. Finally, a thesis is in progress, with a defense scheduled for 2024, on the influence of hydrogen on the reactivity of molecules representative of the chemical natures present in fuels/biofuels.
On the basis of these experiments, the laboratory would like to initiate a thesis on the understanding of hydrogen reactivity under combustion conditions and atmospheric chemistry, to encompass the conditions of use of green hydrogen as an energy carrier. This approach is unprecedented in terms of the temperature range studied.
During this thesis, measurements of auto-ignition times will be carried out in a fast-compression machine. Hydrogen will be mixed with dimethyl ether, a highly reactive species, in order to achieve temperature conditions below 300°C. In addition, the laboratory is equipped with a cold-flame burner capable of operating between 30 and 600°C, thanks to enrichment of the reactive mixture with ozone (O3) and dimethyl ether (DME), which will enable hydrogen reactivity to be studied at temperatures as low as 150°C.
A detailed kinetic model validated under the conditions of this burner for a DME/O2/O3 mixture has also been developed as part of a thesis at the laboratory, and will enable an in-depth examination of the reactions specific to hydrogen under these conditions, free from the reactions specific to ozone and DME.
The experimental data collected will be used to refine our knowledge of hydrogen reactions, and to validate and advance the performance of a detailed kinetic model over a novel temperature range from ambient to adiabatic hydrogen flame temperature (approx. 2100°C). The modelling results obtained with a robust model will be used to estimate the hydrogen risk in its storage and use, the impact of hydrogen on air quality and, of course, the design of equipment for converting the chemical energy of hydrogen into useful energy.
The thesis will be directed by G. Vanhove and co-supervised by Y. Fenard.
Keywords : hydrogène, oxidation, réactivité homogène, combustion et atmosphère, modélisation cinétique
Contacts : yann.fenard()univ-lille.fr / guillaume.vanhove()univ-lille.fr
Financement envisagé : Région Hauts-de-France, ADEME, Université de Lille