Advanced kinetic-based approach of multistep processes: The case of the pyrolysis of biomass-derived humins
2022
Gariboti, Julio César de Jesus | Macedo, Marina Gontijo Souza | Gomes, Eliezer Ladeia | Rueda-Ordóñez, Yesid Javier | Felisbino, Romilda Fernandez | Tovar, Laura Plazas
The pyrolysis of sugarcane bagasse derived-humins (H-SCB) was evaluated in this work by considering independent, overlapping, or competing multistep reactions. An eight-stage parallel reaction model was used in the thermokinetic analysis. The most appropriate kinetic mechanism determined by the master-plot method showed that the second sub-stage proceeds via a 4th-order chemical reaction and the other steps are controlled by nucleation. Based on mathematical calculations, six consecutive-competitive reactions were studied and the modified Kilzer-Broido model was the most relevant to represent the pyrolysis of H-SCB. The kinetics is influenced by the reactivity of H-SCB in two parallel n-order reactions (n = 6.28 to volatile compounds and n = 1.35 to intermediate product). Diffusion-controlled reaction governed the secondary stage in the conversion to biochar. Competitively, nuclei growth occurs and the intermediate product decomposes into volatile products. By using multistep reactions to account for pyrolysis products, the predicted kinetic profiles agreed well with the experimental data.
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