Experiments integrated with molecular dynamics simulations for revealing the soot formation mechanism during coal gasification under different atmospheres based on drop tube reactor

Soot is an important part of the entrained flow coal gasification fine slag, and it is significant to understand its formation for the efficient utilization of residual carbon in fine slag. In this study, coal rapid pyrolysis experiments were conducted, and soot was captured using drop tube reactor. Soot formation mechanism was explained at microscopic level in combination with ReaxFF molecular dynamics. An increase in residence time induces the soot to gradually change from flocculent structure to regular spherical structure, with increased graphitization and reduced oxidizing activity. CO produced by high-temperature cracking of CO₂ and OH produced by the decomposition of H₂O is easy to combine with the precursor of soot to inhibit its nucleation process, resulting in lower maturity of the formed soot compared with that in inert atmosphere. This study provides important insights into the types and formation mechanisms of residual carbon in entrained flow coal gasification.