Interaction Mechanisms of Co-Pyrolysis and Co-Gasification in Coals with Different Ranks Using Deviation Function Analysis

The growing scarcity of coking coal necessitates precise coal blending in the coking process. Using thermogravimetric analysis (TGA) experiments, this study investigates the co-pyrolysis and co-gasification behavior of gas coal (GC), coking coal (CC), lean coal (LC), and their blends, and quantifies interactions via the deviation function method. Results demonstrate that increasing the proportion of low-rank coal significantly reduces the maximum pyrolysis rate temperature (Tmax) of the coal blends. Kinetic analysis reveals that apparent activation energy decreases with increasing proportion of low-rank coal at the DTG peak. During the initial pyrolysis stage of coal blends at 200–380°C, synergistic effects arise from the catalytic release of bound water by minerals and the decomposition of carboxylic acids. Conversely, steric hindrance from polycyclic aromatic hydrocarbons in high-rank coal induces antagonistic effects during the thermoplastic stage, impeding volatile release. Additionally, in gasification, the high reactivity of GC dominates the reaction process. At the same time, CaO in CC mediates CO2 gasification through the CaCO3 cycle, and LC’s elevated ash content inhibits active site release. This work elucidates pyrolysis patterns of coal blends at different temperatures and enables predictions for pyrolysis and coking processes.