Silicon dust flames: A pathway to using silicon as a carbon-free energy carrier

Silicon is a promising energy carrier due to its abundance and energy density, which is comparable to aluminum and higher than that of iron. To date, research on silicon flames has primarily focused on addressing industrial safety concerns, often utilizing laboratory equipment unsuitable for fundamental combustion research. This work presents experiments with laminar silicon Bunsen dust flames, successfully stabilized for the first time using a newly redesigned McGill metal dust burner. The experiments are performed in 30%O 2 –70%N 2 and 40%O 2 –60%N 2 gas mixtures. The burning velocity of silicon flames, determined using the truncated cone method and particle image velocimetry (PIV), appears to be lower than that of aluminum flames but potentially comparable to that of iron flames of similar particle sizes. The flame temperature, estimated from the continuous flame spectra, is found to be a weak function of both fuel and oxygen concentrations due to the fact that a large fraction of the energy in the combustion zone is chemically stored in the SiO intermediate products. The formation of gaseous SiO during combustion is observed experimentally via the UV molecular spectra. Analysis of the combustion products reveals that they consist entirely of amorphous and spherical SiO 2 nanoparticles. The present study suggests that silicon particles primarily burn heterogeneously, during which most of the oxidation products form as intermediate gaseous SiO. This SiO further oxidizes into condensed SiO 2 upon cooling, ultimately forming nano-sized silica particles. Our work provides new data on silicon combustion, advancing the understanding of its feasibility as an alternative carbon-free energy carrier.