Pyrolysis study of Huainan coal with different particle sizes using TG analysis and online Py-PI-TOF MS

The pyrolysis behaviors of Huainan coal (HN coal) with three particle sizes, i.e., <40 mu m (HN-S), 224-500 mu m (HN-M) and 1600-2000 mu m (HN-L), were investigated by thermogravimetry (TG) and online pyrolysis photoionization time-of-flight mass spectrometry (Py-PI-TOF MS) using a krypton discharge lamp (10.6 eV) and synchrotron radiation vacuum ultraviolet light (SVUV) (14.2 eV and 15.5 eV) as the ionization sources. The fragment-free mass spectra of coal pyrolysis products were obtained at 600 degrees C in real time. The released organic volatiles were characterized as alkenes, phenols and aromatics, and their evolved profiles were measured as a function of time in fixed temperature mode and as a function of temperature in programmed-temperature mode. A higher weight loss ratio of the TG curves was obtained when the particle size was increased. The intensities of the individual volatiles in the mass spectra were all enhanced following the increase in the particle size of HN coal. With regard to the time-evolved profiles, by increasing the particle size, the appearance times of volatiles were delayed. Tricyclic aromatics showed multireleasing processes in both time-evolved and temperature-programmed profiles. The release of the guest molecules lagged within the higher temperature region as the coal particle size increased. To explain the evolution trends of most organic volatiles, a mechanism combining intraparticle and interparticle mechanisms is presented. (C) 2019 Energy Institute. Published by Elsevier Ltd. All rights reserved.