Evaluation of thermodynamic and kinetic properties of carbide slag for fluidized thermochemical heat storage

Although the output of industrial solid waste carbide slag is high, its utilization rate is low. Furthermore, carbide slag has a tendency to cause serious environmental problems. In this study, thermochemical heat storage through dehydration and rehydration is presented for resource utilization of carbide slag. The thermodynamic and kinetic properties of carbide slag in fluidized thermochemical heat storage were studied both experimentally and theoretically. The thermochemical heat storage capacities of three carbide slags were evaluated. In a temperature range of 50–300 °C, the specific heat capacity of carbide slags and their decomposition products was 1.0–1.5 J/(g·°C) and 0.72–0.96 J/(g·°C), respectively. The ratio of the sensible heat storage capacity of carbide slag to the total heat storage capacity increased with storage temperature. Furthermore, the rapid decomposition reaction of carbide slag conformed to the contracting cylinder model with an apparent activation energy of 96.94 kJ/mol and pre-exponential factor of 8.09 × 104 s−1. The reaction time of the carbide slag predicted by the kinetic control equation was close to the experimental result of the fluidized bed reactor, providing reliable kinetic information for the design of the fluidized bed reactor. This study demonstrates that carbide slag is a low-cost heat-storage material with promising large-scale industrial applications.