Thermodynamics and kinetics of the thermal decomposition of carbide slag for active CaO

The recycling of calcium resources from carbide slag presents a promising approach for comprehensive utilization, offering significant economic and environmental benefits. Here, the thermal decomposition behavior, kinetics, and thermodynamics of carbide slag were explored using thermogravimetric analysis (TG-DTG) under an air atmosphere. The kinetic parameters of the thermal decomposition of carbide slag during the dehydration of Ca(OH) 2 and the loss of CO 2 from CaCO 3 were calculated by the Kissinger and the Flynn–Wall–Ozawa (FWO) (1) method The apparent activation energies (Es) corresponding to the different conversion rates were estimated using the FWO (2) and Starink methods, which yielded consistent results obtained in different thermal decomposition stages. Subsequently, a double extrapolation method combining FWO and Coats–Redfern (CR) was employed to identify the mechanism functions. The decomposition process was best described by the function G(α) = α 2 for the dehydration stage and G(α) = α for the decarbonation stage. Finally, key thermodynamic parameters, including the changes in enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), were calculated based on the E values obtained from the FWO method. These kinetic and thermodynamic findings provide a theoretical foundation for the circular economy application of producing active CaO via the high-temperature calcination of carbide slag.