InterPore2026

Experimental investigation of non-premixed ammonia combustion in porous inert media

21 May 2026, 15:35

1h 30m

Poster Presentation (MS18) High-temperature heat and mass transfer within porous materials for energy and space (T > 800 °C) Poster

Speaker

Daniel Kretzler (Karlsruhe Institute of Technology)

Description

Ammonia is a promising fuel for zero-carbon energy storage, transport, and conversion. However, its application in combustion systems is challenging due to high NO$_x$ emissions and low flame stability. Both challenges are addressed here by utilizing combustion within porous inert media (PIM) to stabilize the flame and by employing a distributed, non-premixed combustion mode to reduce NO$_x$ formation. The work is conducted in close collaboration between experimental and numerical combustion science as well as additive manufacturing.
Non-premixed NH$_3$/air combustion is systematically investigated using three complementary burner configurations. A counterflow burner (1D model burner) provides fundamental validation of reaction mechanisms, showing good agreement between measured extinction strain rates, chemiluminescence signals, and predictions using the Konnov chemical kinetic mechanism. An optically accessible, heated slot burner (2D model burner) [1] is used to study the influence of boundary conditions, demonstrating that sufficient residence time and elevated wall temperatures can yield negligible NH$_3$ slip under globally stoichiometric non-premixed conditions. Additively manufactured materials are evaluated for their suitability in ammonia combustion environments. Finally, a porous inert media burner is employed to analyze distributed, non-premixed NH$_3$ combustion, revealing stable operation with pure NH$_3$/air across a wide operating range ($0.25–0.76$ $\text{MW m$^{-2}$}$, $\Phi = 0.7-1.3$) and porous-media temperatures up to $1722~ \text{K}$.
Across all operating points, non-premixed operation is found to reduce NOx emissions by about one order of magnitude compared to premixed operation. Although unburned NH$_3$ levels increase, the lowest combined NO$_x$ + NH$_3$ emissions remain substantially lower in the non-premixed case ($143~\text{ppmv}$ vs. $415~\text{ppmv}$), while N$_2$O stays below $40~\text{ppmv}$. Noteably, the minimum emissions in non-premixed operation are achieved under practically relevant lean conditions, whereas the lowest emissions in premixed operation occur only under rich conditions. Complementary simulations capture these trends and indicate that H$_2$ formed via NH$_3$ dehydrogenation in the non-premixed configuration contributes to the observed NO$_x$ reduction.
These findings demonstrate that distributed, non-premixed combustion in PIM enables stable, low-emission ammonia combustion and provides a promising strategy for future burner development. Numerical tools such as the volume-averaged simulation (VAS) framework [3] support the selection of operating regimes and tailored burner configurations, while additive manufacturing offers robust Al$_2$O$_3$-based structures and future potential for optimized 3D-printed gyroid geometries tailored for improved gas distribution, heat recirculation, and material resistance.

Acknowledgements:
The authors acknowledge the financial support by DFG, Germany (project number: 523876164, within PP2419 HyCAM). The authors also gratefully acknowledge the financial support by the Helmholtz Association of German Research Centers (HGF), within the research field Energy, program Materials and Technologies for the Energy Transition (MTET), topic Resource and Energy Efficiency, Anthropogenic Carbon Cycle (38.05.01).