Study on the Synergistic Caking Mechanism of Vitrinite and Inertinite: Reconstructing Maceral Activity Based on Reflectance Thresholds

High Resolution Image Download MS PowerPoint Slide In this study, high-purity vitrinite-rich concentrate and inertinite-rich concentrate (>90%) were separated from coking coals. The structural differences, pyrolysis behaviors, and synergistic effects of the separated concentrates were analyzed using coal petrology, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric pyrolysis, and thermogravimetric gasification. The results showed that vitrinite was rich in aliphatic structures and oxygen-containing functional groups, resulting in lowered initial pyrolysis temperature, increased mass loss rate, and strong caking activity. The chemical structure and thermal properties of inertinite with reflectance below 1.7% was similar to those of vitrinite, making it participate in the formation of plastic mass as an active component. After coking, vitrinite-rich and inertinite-rich concentrates were highly consistent with microcrystalline parameters, indicating that inertinite provided effective skeletal support for coke. Vitrinite coke exhibited higher gasification reactivity overall, while some inertinite in coal exhibited high-temperature reactivity, indicating that inertinite was not completely inert. A new evaluation index for “coal caking macerals” was proposed using a reflectance threshold of 1.7%. Incorporating low-reflectance inertinite into the caking system significantly enhanced its correlation with caking index, with the coefficient of determination increased from 0.2459 to 0.5602. This study provides a theoretical basis and technical support for optimizing coal blending and improving coke quality.