Heterogeneous chemical structures of single pulverized coal particles and their evolution during pyrolysis: Insight from micro-Raman mapping technique.

In this study, Raman mapping technique was developed to realize surface chemical imaging of single pulverized coal particles on a micron scale. Heterogeneity and its evolution during pyrolysis of the Zhundong pulverized coal particles were investigated. The results show that single pulverized coal particles have significantly different heterogeneity. There is a nonmonotonic relation between the heterogeneity degree and average chemical structures of the single pulverized coal particle. During pyrolysis, the structural evolution of various regions in a single pulverized particle differs from each other, especially at the early stage. The regions with more fluorescence-rich structures or small aromatic rings react earlier, and then the whole particle almost experiences a translational reaction. Besides, the heterogeneity of the single pulverized particles evolves differently for specific chemical structures, and the pyrolysis process can change but not eliminate the heterogeneity for various structures. [Display omitted] • Chemical imaging of single pulverized coal particle surface was realized by Raman mapping. • Pyrolysis process of single pulverized coal particle was traced and investigated. • Quantitative indexes for the heterogeneity of single coal particles were proposed. • Differentiation evolution paths of coal particles during pyrolysis were revealed. [ABSTRACT FROM AUTHOR]