Effects of volatile contents on the deflagration characteristics and soot formation of methane/coal volatiles hybrid explosion using reaction kinetics simulation

Abstract

The volatile content of coal dust has a great influence on the explosion features and reaction process for methane/coal dust mixtures. The present work aims at exploring the specific influence and underlying mechanisms of coal volatiles on explosions of the mixture. For this purpose, the reaction kinetics model of coal volatiles deflagration in methane-air atmospheres was established based on Wang-Frenklach (WF) mechanism and Appel-Bockhorn-Frenklach (ABF) mechanism, with the numerical modeling presenting excellent consistency with previous reports. In addition, with the aid of the CHEMKIN-PRO program, the explosion characteristics of coal volatiles with different contents in various methane-air atmospheres were numerically investigated. The primary chain-reaction paths and significant features of key radicals for the mixtures were firstly explored, the variation laws in temperature, pressure, and ROP (Rate-of-Production) for the mixtures were then quantitatively analyzed, and finally, we discussed the formation rules and reaction mechanisms of the soot particles generated in the explosions. Results showed that for a given methane-air atmosphere, as the volume fraction of volatile content increased from 0.1% to 1.6%, the explosion reactions of the mixtures occurred prematurely, indicating the coal volatile content has a positive influence on the hybrid explosion of the mixtures. Meanwhile, methane concentration is dominant in provocating the explosion severity and the maximal temperature of the mixtures. For the methane concentrations of 7%, 9.5%, and 11%, as the volume fraction of coal volatile increased from 0.1% to 1.6%, the maximal explosion pressure decreased by 0.34%, 0.26%, and 0.23%, whereas the maximal explosion temperature increased by 0.25%, 0.19%, and 0.17%, respectively. In addition, the ROP of the free radicals exhibited an increasing tendency as the volume fraction of coal volatile increased from 0.1% to 1.6%, particularly, the two most active free radicals H and O obtained different increases in content. Furthermore, as the volume fraction of coal volatile increased from 0.1% to 1.6%, the time for the growth rate of soot particles reaching its maximum reduced by 71.06% and the growth rate decreased by 37.51%. This study can provide theoretical references and effective strategies for accident prevention and disaster control of methane-coal dust explosions.