Effective reduction on flame soot via plasma coupled with carbon dioxide

This study explored the impact of non-thermal plasma and CO2 on the flame soot characteristics within the diffusion flames. We analyzed on flame structures that were diluted with either CO2 or N2, temperature distributions, and soot characteristics, both in the presence and absence of plasma. Due to the higher specific heat capacity of CO2 compared to N2, the optical observations consistently showed lower temperatures in flames diluted with CO2 as compared to those diluted with N2. The inclusion of plasma and carbon dioxide resulted in the lowest soot concentration, indicating that plasma coupled with CO2 has a synergistic inhibitory effect on soot emissions. The findings revealed that when CO2 was used to dilute the flames and the oxygen concentration was low, the soot nanostructure appeared amorphous. Raman results showed that the level of graphitization observed in soot particles from CO2 dilution flames was lower than that from N2 dilution flames. In the presence of plasma and CO2, the soot obtained exhibited the shortest fringe length and the highest fringe tortuosity. Significant correlations were observed between the nanostructure of soot and its reactivity. The combined application of plasma and CO2 proved to be effective in reducing the soot carbonization degree. [Display omitted] •Effects of plasma and CO2 addition on flame characteristics were investigated.•Coupled plasma and CO2 effects on soot concentration were explored.•Soot graphitization degree decreased with plasma and CO2 addition.•Soot produced by the coupled plasma with CO2 exhibited the highest reactivity.