Study On Liquefaction Performance Of Inertinite Components And Key For Upgrading Of Raw Coal With High Inertinite Content

Direct coal liquefaction has a strict adaptability to coal types.Due to different coal forming processes and environments,even if the coal types are the same,there are sometimes significant differences in macerals and organic structures.Inertinite in coal is the"inert component"of direct liquefaction,only a small part of which is transformed.In this study,raw coal with high inertinite content was selected to investigate the chemical structural characteristics of inertinite of different densities.Inertinite-rich(>1.30kg/L)in raw coal was further separated into low(LDI,1.30–1.38 kg/L)-and high(HDI,>1.38 kg/L)-density samples via density flotation.The raw coal(1665),LDI(1667)and HDI(1668)were analyzed and characterized.The structural differences of the raw coal(1665),LDI(1667)and HDI(1668)were researched,and the structural models of the raw coal(1665),LDI(1667)and HDI(1668)were established.The bond length and bond order data calculated by quantum chemistry were combined with the molecular structure model to explore the differences of chemical structure characteristics of the three samples.The experimental results show that:The structural models of raw coal,LDI(1667),and HDI(1668)are C₁₇₆H₁₇₄N₂O₂₀,C₁₅₂H₁₄₇NO₂₁,and C₁₅₄H₁₄₄N₂O₁₇,respectively.The structural parameters of bond order and bond length of the structural model are helpful to determine the active sites of chemical bond fracture and evaluate the relationship between molecular structure and pyrolysis characteristics.The bonds break at 31 points in structure of raw coal(1665)and that the bond order and bond length are 0.1561–0.8381 and1.5336–1.5019,respectively.The LDI(1667)structure breaks at 24 points and that the bond order and bond length are 0.0131–0.7982 and 2.1556–1.4997,respectively.The HDI(1668)structure breaks at 25 points and that the bond order and bond length are 0.1793–0.7924 and1.5377–1.4935,respectively.According to the activity and number of broken chemical bonds of the samples,the structure of raw coal(1665)is more prone to bond breakage than those of LDI(1667)and HDI(1668).LDI(1667)and HDI(1668)show certain similarities in number of active breaks of chemical bonds and fragment structures after bond breakage.Although some differences exist,these differences are progressive in nature and not large scale.Typical liquefaction residues of raw coal(1665)and low density inertinite(1667)were selected for XRD analysis.Through the comparison of the structural parameters of the liquefaction residue and their respective raw coal,it is found that the LA and LC values in the liquefaction residue increase,and the 2??decreases,which indicates that the degree of graphitization or carbon network regularization increases and the chemical activity decreases.Compared with the raw coal,the liquefaction residues of 1665 and 1667 have obvious changes,the?peak is smaller and the 002 peak is larger,which indicates that there are more aromatic structure and less fat structure in the liquefaction residue structure,compared with the raw coal structure.Under the optimal liquefaction conditions,the liquefaction conversion of 1 665,1667and 1668 were 85.05%,73.41%and 70.98%respectively,and the oil yield of 1 665,1667and 1668 were 61.09%,50.97%and 50.82%respectively.