Influence of inertinite on coal physicochemical thermal transformation properties and liquefaction behaviors

Abstract

Coal is heterogeneous, but the inertinite in coal is not conducive to liquefaction, resulting in a lower yield of coal-liquefied oil. Herein, to investigate the liquefaction performance of inertinite, two coal samples with different inertinite contents were obtained by the floating and sinking of coal: low-density inertinite (LDI) and high-density inertinite (HDI). Respectively, the pyrolysis characteristics and liquefaction properties of inertinite in raw coal, LDI and HDI were investigated using molecular structural models combined with quantum chemical calculations, thermogravimetric analysis (TGA), X-ray diffraction (XRD) and liquefaction tests. Quantum chemical calculations revealed that raw coal and LDI comprised more bonds with longer bond lengths and smaller bond orders than HDI. Form Bond-breaking analysis, various cyclic fragments of free radicals were obtained from the pyrolysis of raw coal were primarily monocyclic and bicyclic free radicals, the LDI were primarily binary and ternary annular fragments, and the HDI were mainly composed of quaternary ring fragments. The TGA results revealed that the thermal decomposition reactivity of LDI was comparable to raw coal and superior to HDI. XRD results revealed that the size and content of the aromatics in raw coal residue (RCR) and LDI and LDI residue (LDIR) increased in comparison with raw coal and LDI after liquefaction. The comparison of the liquefaction results of raw coal LDI and HDI revealed that coals with LDI instead of HDI exhibit better liquefaction performance.