Effect of mechanical energy input during mechanical crushing on the macrokinetics of the coal–oxygen reaction: A laboratory–scale study

Abstract

Underground mining is usually simplified as a process of coal crushing and pulverization. However, this process is not purely physical. The mechanical energy input to this process also induces a mechanochemical effect. The specific impact of this effect on the macrokinetics of the coal–oxygen reaction (COR) has not been independently investigated, which motivates this work. Thermal analysis tests showed that mechanical energy input contributed to the strength of the COR and exhibited regularities in its impact on COR's kinetic parameters. Explanations for this were given based on mechanochemistry, free radicals chain reaction and quantum chemistry theories. A coal macromolecule model, influenced by mechanical energy input, was developed based on the typical Wiser model, and subsequent quantum mechanical calculations were conducted. It was found that mechanical energy input facilitated the breaking of specific chemical bonds in coal, redistributing the electrostatic potential and increasing the number of active sites within the coal molecule. Moreover, both the free radicals from bonds breaking and the remaining active structural sites exhibited an increasing trend in their electrified capacities. Different from the traditional physical pathway, this work refined the mechanism by which mechanical forces affect COR through the mechanochemical pathway.