Pyrolysis of orange waste: A thermo-kinetic study

Thermal and kinetic decomposition of orange waste have been investigated by simultaneous TGA–DSC and TGA–FTIR analysis techniques under nitrogen atmosphere. Thermal profile degradation can be interpreted as the resultant of multiple, parallel and simultaneous reactions, related to: (i) dehydration process for temperatures ≤120 °C; (ii) pyrolytic cracking, from 125 to 450 °C, stage where the ligno-cellulosic components are degraded reaching a maximum the evolved gaseous products and delivery energy; and (iii) to latest stage of lignin degradation, at temperatures ≥450 °C. The volatile compounds evolved from 50 to 600 °C were mainly: H2O, CO2 and CO, besides of a mixture organic product composed by: carboxylic acids, aldehydes or ketones (CO), alkanes (CC), ethers (COC), alcohols (COH), phenolic compounds (CO) and aliphatic and/or unsaturated aromatic compounds (CC). Kinetic parameters were calculated by two kinds of model-free kinetics algorithms, Friedman (F) and Kissinger–Akahira–Sunose (KAS) methods at different heating rates (5, 10 and 15 °C min−1). The results in terms of activation energy show the complex Ea(α) on α dependence, which evidences an multi-step kinetic processes during the pyrolytic cracking of the orange waste.