Soot emission reduction via magnetic field coupling with carbon dioxide in diffusion flames

Considering that soot particles emitted from industrial combustion equipment were substantial contributors to global warming and human health issue, the reduction of soot emission via magnetic field coupled with carbon dioxide (CO₂) was explored in this study. As high as an 85 % reduction in soot mass emissions from exhaust gas of inverse diffusion flames could be achieved by introducing a 2T magnetic field and substituting nitrogen (N₂) with CO₂ as the dilution gas, indicating that magnetic fields could effectively synergize with CO₂ to reduce soot emission. Furthermore, to gain insight into the principles of soot reduction, the soot nanostructure and graphitization degree was investigated using the high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It was discovered that the nanostructure of soot particles became more disordered and exhibited a lower graphitic degree in the presence of magnetic field and CO₂, leading to higher oxidation activity. This finding suggested that magnetic fields and CO₂ addition inhibited soot formation primarily through suppressing the polycyclic aromatic hydrocarbon (PAHs) nucleation and soot surface growth. Given its excellent performance in reducing soot emissions, magnetic field synergistic CO₂ was a promising strategy for developing cleaner combustion devices.