Combustion Reaction Mechanisms and Radical Kinetics in Coking-Coal Dust Explosions: ReaxFF-MD and Experimental Validation

Coking-coal dust explosions are rapid combustion processes governed by coupled molecular decomposition, radical-chain reactions, oxidation, and energy release, yet the molecular origin of their staged reactivity remains unclear. Here, ReaxFF molecular dynamics simulations were combined with 20-L explosion experiments and time-resolved optical emission spectroscopy to elucidate molecular structural evolution and radical kinetics. The reaction proceeds through three stages: initial pyrolysis and peripheral bond cleavage, skeletal deconstruction and oxidation, and deep fragmentation and oxidation. The corresponding stage-averaged temperature-change rates are 0.162, 2.25, and 24.32 K ps−1, respectively, indicating a progressive increase in the magnitude of net temperature change per unit time across the three stages. Reaction-network analysis identifies the reversible O2 + H ⇌ HO2 cycle as a dominant regulator of H-radical availability, while HO2 branching promotes O/OH formation and subsequent oxidation. Increasing ignition energy from 8 to 10 kJ raises the maximum explosion pressure from 0.4294 to 0.5594 MPa and the maximum pressure-rise rate from 4.416 to 12.9094 MPa s−1. These results establish a multiscale link between molecular structural evolution, radical-chain chemistry, and macroscopic coal-dust explosion intensity.