Co-pyrolysis Behavior of Coal and Biomass: Synergistic Effect and Kinetic Analysis.

Co-pyrolysis of coal and biomass is an efficient way to utilize resources. This study investigates the co-pyrolysis behavior and kinetics of coal and biomass using thermogravimetric analysis (TGA) and TG-FTIR. Co-pyrolysis of coal and biomass exhibits a synergistic effect. When the biomass is 25%, the weight loss increases, showing a positive synergistic effect. When the biomass is 50%, it exhibits a negative synergistic effect. Increasing the heating rate can promote the generation of a synergistic effect. Co-pyrolysis involves two central pyrolysis stages: stage III (250-380 °C) and stage IV (380-550 °C). Friedman, FWO, KAS, and STA methods are used to calculate the activation energy for stages III and IV. The activation energy ( ) for co-pyrolysis is higher than that for coal or biomass pyrolysis alone. A positive synergistic effect is observed in stage III, while a negative synergistic effect is noted in stage IV. The master curve method determines an accurate reaction order () and pre-exponential factor () value of Coal75-Bio25. In stage III, = 238.81 kJ/mol, = 2.4, = 1.30 × 10 s. In stage IV, = 37 8.01 kJ/mol, = 4.0, = 1.10 × 10 s. The kinetic parameters in stage IV are significantly higher than those in stage III. TG-FTIR is used to analyze the synergistic effect of co-pyrolysis. Compared with coal and biomass pyrolysis separately, the Coal75-Bio25 pyrolysis process releases less CO and more CH. These findings support the synergistic effect of coal and biomass during co-pyrolysis.