Torrefaction effects on the pyrolysis of pineapple crown (Ananas comosus)—kinetic triplet and model validation

Abstract The aim of this study is to suggest pyrolysis as a possible route for pineapple crown, by estimating the kinetic triplet that efficiently represents the slow pyrolysis of raw and previously torrefied pineapple crown. Thermogravimetric analyses were performed at heating rates of 2.5, 5, and 10 K min −1 , and global methods were applied (isoconversional methods and compensation effect). The raw material was characterized by proximate analysis and chemical composition, and these values were consistent with other biomasses. The stages verified for the decomposition of the raw and torrefied biomass were dehydration, volatilization and carbonization. The torrefaction process mainly decomposed the hemicellulose. Furthermore, an increase in the activation energy of the pyrolysis of the torrefied material was observed, which occurs due to the degradation of the most reactive portion of the material. The slow pyrolysis of the raw pineapple crown presented an activation energy of 154.56 kJ mol −1 , a global pre-exponential factor of 1.75 × 10 12 s −1 , and a global conversion function N3 (third-order reaction). The pyrolysis of torrefied biomass presented an activation energy of 176.33 kJ mol −1 , a global pre-exponential factor of 1.34 × 10 13 s −1 , and a global conversion function N2 (second-order reaction). This work proposed a methodology based on the reconstruction of experimental kinetic curves using all conversion functions, and the results indicate that the methodology effectively determined the parameters that represent the decomposition of the heterogeneous material. Graphical Abstract