Structural features of residue carbon formed by gasification of different coal macerals

Gasification fine slag contains a high content of carbon, which causes waste of resources and environmental hazards. In essence, fine slag is a comprehensive reflection of the separate gasification of various macerals in coal. In this study, different macerals concentrates were firstly prepared from Yangchangwan (YCW) and Meihuajing coal (MHJ). The structure and pyrolysis characteristics of different macerals as well as the morphology and molecular structure of gasification residue carbon at different conversion levels were then investigated by a series of characterization techniques. The results show that the aromatic degree of inertinite concentrates of both coals is greater than that of vitrinite. During the active pyrolysis stage of 200–600 °C, the weight loss rate of vitrinite is higher than that of inertinite, and the weight loss rate reaches maximum at about 445 °C. Maximum thermal weight loss rate of YCW and MHJ vitrinite is 1.39 and 1.43 times higher than that of inertinite. The shrinkage ability of inertinite char is stronger than that of vitrinite and the surface of inertinite residue carbon is rougher and rich in porous structures during gasification, resulting in a higher final gasification carbon conversion level. The fresh vitrinite char obtained from pyrolysis has lower order degree and more active sites. As the gasification proceeds, the content of active sites in vitrinite gasification residue carbon decreases rapidly, while inertinite remains relatively stable. This research innovatively links the properties of macerals with the structure of residue carbon, which is helpful to deepen the understanding of the correlation between coal microstructure and reactivity.