PP 2419 HyCAM

Ammonia, which can be produced using renewable hydrogen, offers a promising possibility for use as a carbon-free energy carrier, as it can easily be liquified for storage and transport over long distances using existing infrastructure. Combustion of ammonia poses considerable challenges. The three major challenges are its low burning velocity compared to hydrocarbons resulting in poor flame stability, extremely high levels of nitrogen oxide formation and high toxicity even at trace levels. Conventional approaches to tackle these challenges are the addition of highly reactive fuels like H2 or CH4 to address the issue of flame stability, conversion in staged fuel rich/lean processes to address the high NOx formation and post treatment to avoid unburnt ammonia emissions.

Motivation:

In the present project we pursue the approach of non-premixed combustion in tailor-made porous media to convert ammonia with low emissions at acceptable power densities. To achieve this objective the project consists of an interdisciplinary collaboration with joint expertise in the fields of experiments (EXP), numerical simulation (SIM) and additive manufacturing (ADM).

Objectives:

To address all challenges using pure ammonia as a fuel, we develop a novel concept for non-premixed combustion of ammonia in ceramic Porous Inert Media (PIM). Combustion in PIM can increase burning velocities by more than one order of magnitude compared with non-PIM combustion due to heat recirculation through the solid phase. Heat recirculation together with the thermal inertia of the solid phase resolves the issue of flame stability. The non-premixed approach in PIM results in high temperatures of the upstream fuel rich or pure fuel streams that decompose ammonia without significant NOx formation, while the good mixing and temperature homogenisation by the flow through the PIM lead to a complete burnout of remaining ammonia in the downstream combustion and post-combustion zones. To realise such a concept, tailored high temperature-resistant materials are required, both in terms of geometry as well as thermal properties. Additive manufacturing of PIM structures from composite ceramic materials is needed to control the process through customised properties regarding heat conduction, radiation properties and dispersion/flow field. The fundamental research and design of the non-premixed PIM burner for NH3 and NH3/H2-mixtures requires a strong interdisciplinary research team in the fields of high-fidelity experiments for combustion in PIM (EXP, KIT), detailed pore-resolved numerical simulations (SIM, KIT) and additive manufacturing methods for thermal shock- and corrosion-resistant functional ceramic components (ADM, TU BAF).

Forschergruppe:

SIM:
Engler-Bunte-Institut, Karlsruher Institute of Technology (Prof. Dr. Oliver T. Stein)
Institute for Combustion Technology, University of Stuttgart (Dr.-Ing. Thorsten Zirwes)
EXP:
Engler-Bunte-Institut, Karlsruher Institute of Technology (Prof. Dr.-Ing. Dimosthenis Trimis, Dr.-Ing. Björn Stelzner)
ADM:
Institute of Ceramics, Refractories and Composite Materials Professorship of Ceramics, Refractories and metal-ceramic Composites, Technical University Bergakademie Freiberg (Prof. Dr.-Ing. habil Christos G. Aneziris, Dr.-Ing. Nora Brachhold)
 

Subproject SIM:

The subproject on numerical modelling and simulation (SIM) will characterise non-premixed ammonia combustion both in the pure gas phase and in PIM. Our first work package will address the fundamental reaction kinetics and combustion characteristics of gaseous ammonia flames, see Fig. 1a. Subsequently NH3 combustion within regular PIM structures will be investigated, Fig. 1b. Finally detailed simulations of the tailor-made prototype PIM reactor shown in Fig. 1c will be conducted, the results of which will continuously be shared with the EXP and ADM groups, aiming to find the optimal burner design.

(a) Schematic model burner for fundamental studies of non-premixed NH3/air combustion without PIM. (b) Model burner with PIM for basic system analysis. (c) Schematic prototype reactor with upstream gyroidal structures for NH3 pyrolysis and downstream PIM for combustion and burnout. Figures not to scale

 

Project responsible/contact

Prof. Dr. Oliver T. Stein
Email: Oliver.T.Stein∂kit.edu

Dr.-Ing. Thorsten Zirwes
Email: thorsten.zirwes∂itv.uni-stuttgart.de

Rishabh Puri, M.Sc.
Email: Rishabh.Puri∂kit.edu