Fluoride Action Network

Thermal behaviors, combustion mechanisms, evolved gasses, and ash analysis of spent potlining for a hazardous waste management

Source: Journal of Environmental Sciences 107:124-137. | August 15th, 2021 | Sun G, Zhang G, Liu J, Evrendilek DE, Buyukada M.
Location: International
Industry type: Aluminum Industry


  • Thermal degradation behaviors of spent potlining (SPL) were quantified.
  • An exothermic reaction dominated the overall reaction process.
  • Fluoride volatilization rate in the flue gasses was 2.24%.
  • Kinetic triplets pointed to the best-fit reaction model as the n-th order mechanism.
  • The mineral deposition mechanisms and ash slagging tendency were predicted.


An unavoidable but reusable waste so as to enhance a more circular waste utilization has been spent potlining (SPL) generated by the aluminum industry. The combustion mechanisms, evolved gasses, and ash properties of SPL were characterized dynamically in response to the elevated temperature and heating rates. Differential scanning calorimetric (DSC) results indicated an exothermic reaction behavior probably able to meet the energy needs of various industrial applications. The reaction mechanisms for the SPL combustion were best described using the 1.5-, 3- and 2.5-order reaction models. Fluoride volatilization rate of the flue gas was estimated at 2.24%. The SPL combustion emitted CO2, HNCO, NO, and NO2 but SOx. The joint optimization of remaining mass, derivative thermogravimetry, and derivative DSC was achieved with the optimal temperature and heating rate combination of 783.5°C, and 5 °C/min, respectively. Interaction between temperature and heating rate exerted the strongest and weakest impact on DSC and remaining mass, respectively. The fluorine mainly as the formation of substantial NaF and CaF2 in the residual ash. Besides, the composition and effect of environment of residual solid were evaluated. The ash slagging tendency and its mineral deposition mechanisms were elucidated in terms of turning SPL waste into a benign input to a circular waste utilization.

Graphical abstract