Inhibition effect and reaction mechanism of NaHCO3 and NH4H2PO4 on the deflagration of methane/coal dust mixtures

To enrich the explosion suppression theory of methane/coal dust hybrid deflagration with different traditional powder inhibitors, this study investigates the inhibitory effects and mechanisms of NaHCO₃ and NH₄H₂PO₄ powder inhibitors on the deflagration of methane/coal dust hybrids. Visual deflagration tests were performed on long-flame, coking, and anthracite coals mixed with 9.5 vol% methane, focusing on flame propagation, pressure evolution, and residue characteristics. Macro and micro experiments demonstrate that NaHCO₃ effectively inhibits low-volatile coal dust/methane deflagration by reducing the kinetic growth rate (K_G) of the anthracite coal/methane mixture (AMM) by 90 %, through the formation of stable particles on coal surfaces that hinder pyrolysis. NH₄H₂PO₄, which exhibits greater efficacy with other coal types, decreases the kinetic growth rate (K_G) of the long-flame coal/methane mixture (LMM) by 73.9 % by producing small molecules that inhibit the formation of intermediate products. Reaction kinetic simulations demonstrated NaHCO₃ inhibits •O radicals via the reaction •NaO+•O=•Na + O₂, while NH₄H₂PO₄ suppresses •H radicals through the reaction •PO₂+•H +•M =•HOPO+•M.