Effects of dilute coal char particle suspensions on propagating methane detonation wave

Methane/coal dust hybrid explosion is one of the common hazards in process and mining industries. In this study, methane detonation propagation in dilute coal char particle suspensions is studied based on Eulerian-Lagrangian method. The effects of char combustion on methane detonation dynamics are fo-cused on. The results show that propagation of the methane detonation wave in coal particle suspensions is considerably affected by particle concentration and size. Detonation extinction occurs when the coal particle size is small and concentration is high. The averaged lead shock speed generally decreases with increased particle concentration and decreased particle size. Mean structure and interphase coupling of hybrid detonation are analysed, based on the gas and particle quantities. It is found that char combus-tion proceeds in the subsonic region behind the detonation wave and heat release is relatively distributed compared to that from gas phase reactions. The mass and energy transfer rates increase rapidly to the maximum near the reaction front in the induction zone. Moreover, for 1 mu m particles, if the particle concentration is beyond a threshold value, detonation re-initiation occurs after it is quenched at the be-ginning of the coal dust suspensions. This is caused by hot spots from the shock focusing along the reaction front in a decoupled detonation and these shocks are generated from char combustion behind the lead shock. A regime map of detonation propagation and extinction is predicted. It is found that the re-initiation location decreases with the particle concentration and approaches a constant value when the concentration exceeds 1,0 0 0 g/m3. Finally, the influence of coal particle surface reactions on gas chem-istry under detonation relevant conditions is studied. It is found that the ignition delay time changes non-monotonically with particle size. The results from this study are useful for prevention and suppres-sion of methane/coal dust hybrid detonation. (c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.