Effective reduction on flame soot via plasma coupled with carbon dioxide.

This study explored the impact of non-thermal plasma and CO on the flame soot characteristics within the diffusion flames. We analyzed on flame structures that were diluted with either CO or N, temperature distributions, and soot characteristics, both in the presence and absence of plasma. Due to the higher specific heat capacity of CO compared to N, the optical observations consistently showed lower temperatures in flames diluted with CO as compared to those diluted with N. The inclusion of plasma and carbon dioxide resulted in the lowest soot concentration, indicating that plasma coupled with CO has a synergistic inhibitory effect on soot emissions. The findings revealed that when CO 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 CO dilution flames was lower than that from N dilution flames. In the presence of plasma and CO, 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 CO proved to be effective in reducing the soot carbonization degree.