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, CO ₂ 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 E_a(α) on α dependence, which evidences an multi-step kinetic processes during the pyrolytic cracking of the orange waste.