Insight into the synergistic effect on thermal behavior in co-pyrolysis of coal slime and sewage sludge: Kinetics, thermodynamics, dendrite neural network modelling, and evolved char structure.

Co-pyrolysis of coal slime (CS) and sewage sludge (SS) is a promising technology to achieve waste reduction and recovery of value-added products. For the first time, pyrolysis behavior, kinetics, thermodynamics, dendrite neural network modelling, and evolved char structure were examined in the co-pyrolysis of CS and SS. The results showed that blending CS and SS at a weight ratio of 6:4 yielded a higher synergy in relation to the obtained kinetic and thermodynamic parameters. At lower temperatures, the active hydroxyl radicals released from SS pyrolyzed volatiles accelerate the dehydrogenation reactions of CS. The interaction between oxygen radicals, such as ether bonds in SS volatiles, and aromatics or hydrocarbon compounds in CS char increases the content of oxygenated compounds in the pyrolytic char by significantly enhancing its reactivity. As the temperature rises, the demethylation reaction of aliphatic hydrocarbons in SS volatiles generates a considerable amount of hydrogen radicals. This intensifies the formation of small-ring aromatic compounds during co-pyrolysis, further facilitating the condensation of small-ring aromatics into larger-ring aromatics at higher temperatures. In addition, a novel dendrite neural network model was successfully applied to predict the co-pyrolysis behavior of CS and SS, whereby the transfer function of interaction was obtained. [Display omitted] • The addition of SS enhances the pyrolytic reactivity of CS. • CS and SS blend at 6:4 yielded the highest synergetic effect than other ratios. • Interaction increased small aromatic rings and O-containing functional groups in co-pyrolysis char. • The interaction raised the formation of ethers and π-type oxygenated radicals in co-pyrolysis char. • Dendrite Net is, for the first time, applied for the co-pyrolysis process. [ABSTRACT FROM AUTHOR]