Three-Dimensional Pore-Scale Numerical Study of the Impact of Operation Parameters on Ammonia–Methane Premixed Combustion in a Double-Layer Spherical Stacked Porous Medium Burner

As a renewable hydrogen carrier with a high volumetric energy density, ammonia has emerged as a potential zero-carbon alternative fuel to fossil fuels in the pursuit of carbon neutrality. However, the narrow ignition range and high pollutant emissions limit the application of ammonia in the heating furnaces. This study develops a 3D pore-scale mathematical model for ammonia-methane premixed combustion in a double-layer porous medium rather than a traditional burner. After the numerical model was validated for feasibility and accuracy, the combustion performance of methane/ammonia blends in a double-layer porous medium is examined under various operating conditions. The numerical results indicate that an equivalence ratio of 1.0 is most beneficial for the complete combustion of double-layer porous media, whereas the amount of ammonia has little effect on the peak combustion temperature, which is close to 1920 K. In addition, the ammonia concentration notably influences CO and CO2 emissions; however, NOX emissions exhibit a nonmonotonic trend, increasing initially and then decreasing, peaking at approximately 10% ammonia concentration. In fuel-rich conditions (equivalence ratio >1.0), NOX emissions are effectively suppressed due to the enhanced reduction of NO by CO, H2, and other radicals. This study aims to provide scientific guidance for enhancing the application of porous medium methane/ammonia combustion technology in industrial furnaces.