Thermal conversion of defective coffee beans for energy purposes: Characterization and kinetic modeling

• Published in: Renewable energy 2020-03, Vol.147, p.1275-1291
• Main Authors: Santos, Carolina Monteiro, de Oliveira, Leandro Soares, Alves Rocha, Elém Patrícia, Franca, Adriana Silva
• Format: Article
• Language: English
• Subjects: Biomass; Kinetic parameters; Model-free kinetics; Thermal analysis
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2019.09.052

This work aimed to characterize the fuel properties and to evaluate the kinetics of thermal decomposition of defective coffee beans (DCB). Three thermogravimetric-based methods were evaluated: Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS) and Friedman. The results showed that DCB presented low activation energy and that the evaluated mathematical models, although satisfactory for describing thermal decomposition in inert atmospheres, did not provide a satisfactory description of the oxidizing process. The enthalpy values indicated that the energy differences between the reagents and the activated complex are related directly to the activation energies. Pre-exponential factors indicated first-order reactions. The immediate analysis and the lignocellulosic contents indicated a biomass with low levels of humidity and ashes, high carbon and volatile concentrations, besides thermal stability. The obtained calorific value was 19.39 MJ/kg. The overall results obtained in the present study indicate that this biomass has the potential to be used as a solid biofuel. •Fuel properties and thermal decomposition kinetics of defective coffee beans (DCB).•DCB has low levels of humidity and ashes, high carbon and volatile concentrations.•Material presents thermal stability and calorific value of 19.39 MJ/kg.•Kinetic models provided good description of thermal conversion in inert atmosphere.•Results confirm that this biomass presents potential to be used as a solid biofuel.