Pyrolysis kinetics, thermodynamics, and interaction analysis of co-pyrolysis of bituminous coal and electrolytic aluminum solid waste

The thermal degradation behavior, kinetics and thermodynamic characteristics were investigated during the co -pyrolysis of Tangkou bituminous coal (TK) and spent cathode carbon block (SCCB) derived from electrolytic aluminum solid waste. In the N2 atmosphere, thermogravimetric analysis was carried out at four heating rates (5, 10, 20 and 40 K/min). The novelty was that the deconvolution technology with bi-Gaussian function was used to separate the complex thermogravimetric curves. The devolatilization of organic matter, the secondary depoly-merization of macromolecules, the secondary repolymerization of macromolecules in coal and the thermal decomposition of fluoride in SCCB were found as different components of the whole co-pyrolysis process of TK and SCCB. Kinetic parameters were estimated by the model-free method and model-fitting method. The results showed that the average activation energy for four stages was 211.30, 222.10, 253.31 and 268.12 kJ/mol, and four stages of co-pyrolysis process fit well with chemical reaction model with reaction order n = 2.5, 3.0, 3.0 and 1.5, respectively. The thermodynamic parameters, including enthalpy (Delta H), Gibbs free energy (Delta G) and entropy (Delta S) were calculated to determine the feasibility and reactivity of the co-pyrolysis process. Eventually, the interaction effect was found in the fourth stage of co-pyrolysis of TK/SCCB.

Automated summary

The study investigates the thermal degradation behavior, kinetics, and thermodynamic characteristics during the co-pyrolysis of coal and aluminum electrolytic solid waste. The results show that the co-pyrolysis process involves the devolatilization of organic matter, secondary depolymerization and repolymerization of macromolecules in coal, and thermal decomposition of fluoride in the solid waste.