Torrefaction coupled oxy-fuel co-combustion of Chinese medicine residue and pharmaceutical sludge: Combustion characteristics and synergistic effects.

Oxy-fuel combustion, a promising technology for CO2 capture, can significantly enhance combustion performance. This study investigates the synergistic co-disposal of Chinese medicine residue (CMR) and its associated pharmaceutical sludge (PS) via a coupled torrefaction and oxy-fuel combustion process. The properties of the torrefied feedstock, the co-combustion characteristics under oxy-fuel conditions, and the underlying synergistic mechanisms were investigated. The findings indicate that the co-combustion of raw CMR and PS demonstrated significant synergy, with a lower ignition temperature and a combustion index (CCI) more than seven times the theoretical value. Torrefaction pretreatment further upgraded the fuel, increasing its higher heating value (HHV) by 7.6 %, boosting its BET surface area by 111 %, and lowering its ignition temperature in air by 47.5 %. Increasing the O2 concentration from 21 % to 31 % intensified combustion, reducing the CO peak from 19.30 % to 3.80 %, halving the burnout time, and lowering the activation energy. The integrated strategy of torrefaction coupled with 31 % O2 oxy-fuel combustion was found to be optimal, compressing the incomplete combustion window and enhancing CO2 enrichment in the flue gas. This combined process provides a robust pathway for the clean valorization of these wastes, establishing a solid foundation for integration with Carbon Capture, Utilization, and Storage (CCUS) technologies.