Inhibition evaluation of modified-fly ash inhibitors in methane/coal dust deflagrations

•Developed modified-fly ash powdered inhibitors PMFAC and MFAC.•Explosion-inhibition experiments on methane/coal powder hybrids showed that PMFAC presents a higher inhibitory efficiency than MFAC.•Revealed the microcosmic mechanism of methane/coal powder explosions inhibited by PMFAC and MFAC using reaction kinetics simulation. The inhibitory efficiency of modified-fly ash inhibitors MFAC and PMFAC on methane/coal dust deflagration was experimentally evaluated. Results suggested that PMFAC was superior to MFAC because of the phosphorus-containing substances and abundant reactive radicals. The composite inhibitor first inhibited the gas-phase reactions of the homogeneous combustion in the hybrid explosion field to decrease the maximum rate of explosion pressure rise (dP/dt)max in the period 0–t1, while reducing the maximum explosion pressure (Pmax) by inhibiting the chain combustion reactions in the period t1–t2. Additionally, the impacts of MFAC and PMFAC on the microscopic reactions of hybrid methane/coal dust deflagration were numerically investigated. Results indicated that the inhibitors significantly prolonged the explosion process and decreased the peak rate of productivity (ROP) for each key reactive radical. Subsequently, the inhibition mechanism by which the PMFAC molecules interacted with the deflagration reactions of methane/coal dust was elucidated in detail. Results revealed that the elementary reactions concerning the key free radicals O, H, and OH were considerably inhibited in the gas-phase reactions. The competition for key radicals in the explosion reactions by the inhibitors indirectly inhibited the surface-phase reactions, and the synergistic effect of the radicals significantly decreased the sensitivities of the key reactions.