Combustion of lean ammonia-hydrogen fuel blends in a porous media burner

Ammonia offers a carbon-free fuel alternative for industrial heating, power generation and transportation. However, its low flame speed and high NO x emission represent significant challenges for combustor applications. The present study investigates the use of porous media burners (PMBs) to stabilize lean NH 3 /H 2 /air flames. By stabilizing the flame at the interface between two thermally conductive ceramic foams, internal heat recirculation preheats the reactants and increases the flame speed, which increases the combustion stability limits to very lean NH 3 /H 2 /air mixtures. Experimental studies are conducted to determine the stability limits of porous media combustion over a wide range of NH 3 /H 2 volume ratios, equivalence ratios and mass fluxes. The NH 3 /H 2 ratio is found to play a significant role with a typical dependency of the equivalence ratio at extinction in the form & phi;ext & PROP; X -0 . 3 H 2 . NO x emissions were shown to reach their minimum when the burner was operated near its extinction limit and to increase with increasing mass flux rates. Because unburnt NH 3 emissions were also quite low (1400 ppm) at these very lean conditions, this operating regime offers similar or better emissions compared to the commonly employed fuel-rich operation which has been suggested in the literature.& COPY; 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

The use of porous media burners (PMBs) to stabilize lean NH3/H2/air flames was investigated. Internal heat recirculation in PMBs preheats the reactants and increases the flame speed, leading to improved combustion stability. Experimental studies were conducted to determine the stability limits of porous media combustion, and it was found that the NH3/H2 ratio and mass flux rates have significant effects on combustion performance.