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 degrees C; (ii) pyrolytic cracking, from 125 to 450 degrees 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 degrees C. The volatile compounds evolved from 50 to 600 degrees C were mainly: H2O, CO2 and CO, besides of a mixture organic product composed by: carboxylic acids, aldehydes or ketones (C=O), alkanes (C-C), ethers (C-O-C), alcohols (C-O-H), phenolic compounds (C-O) and aliphatic and/or unsaturated aromatic compounds (C=C). 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 degrees C min(-1)). The results in terms of activation energy show the complex E-a(alpha) on alpha dependence, which evidences an multi-step kinetic processes during the pyrolytic cracking of the orange waste. (c) 2012 Elsevier B.V. All rights reserved.