Thermogravimetric and mass-spectrometric analyses of combustion of spent potlining under N2/O2 and CO2/O2 atmospheres

Thermal decomposition and gaseous evolution of the spent potlining (SPL) combustion were quantified using thermogravimetric and mass-spectrometric analyses in CO2/O-2 and N-2/O-2 atmospheres using three heating rates (15, 20 and 25 degrees C/min). The thermal decomposition of SPL occurred mainly between 450 and 800 degrees C. Based on the four kinetic methods of Friedman, Starink, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa under the various conversion degrees (alpha) from 0.1 to 0.7, the lowest apparent activation energy was estimated at 149.81 kJ/mol in the 70% CO2 /30% O-2 atmosphere. The pre-exponential factor, and changes in entropy, enthalpy and free Gibbs energy were also estimated. The reaction model did not suggest a single reaction of the SPL combustion. With the alpha value of 0.25-0.7, the following function best described the reaction based on the Malek method: f(alpha) = 1/2 alpha and G(alpha) = ln alpha(2). The gases released during the combustion process included CO2, CO, NOx, HCN, and HF. (C) 2019 Elsevier Ltd. All rights reserved.