On the characteristic heating and pyrolysis time of thermally small biomass particles in a bubbling fluidized bed reactor

• Published in: Renewable energy 2020-11, Vol.160, p.312-322
• Main Authors: Soria-Verdugo, Antonio, Rubio-Rubio, Mariano, Goos, Elke, Riedel, Uwe
• Format: Article
• Language: English
• Subjects: Bubbling fluidized bed (BFB); Characteristic heating time; Characteristic pyrolysis time; Distributed activation energy model (DAEM); Lumped capacitance method (LCM); Olive stones pyrolysis
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2020.07.008

Pyrolysis of crushed olive stone particles in a lab scale Bubbling Fluidized Bed (BFB) reactor was investigated. The time evolution of the pyrolysis conversion degree of the olive stone particles, while moving freely in the BFB, was determined from the evolution of the mass of olive stones remaining in the bed, measured by a precision scale holding the whole reactor installation. The experimental measurements of the pyrolysis conversion degree were employed to validate a simple model combining heat transfer and chemical kinetics, which is valid for thermally small particles. The model combines the Lumped Capacitance Method (LCM) and the simplified Distributed Activation Energy Model (DAEM) to account for heat transfer and pyrolysis chemical kinetics, respectively. The estimations of the combined LCM-DAEM model for the pyrolysis conversion degree were found to be in good agreement with the experimental measurements for the pyrolysis of olive kernels in a BFB operated at various bed temperatures, fluidizing gas velocities, and biomass particle size ranges. From the combined LCM-DAEM model, the characteristic heating time and the pyrolysis time of the olive stone particles were derived, obtaining a direct relation between these two parameters for constant values of the bed temperature. •Pyrolysis of olive stones is analyzed in a macro-TGA bubbling fluidized bed (BFB).•A combined heat transfer and kinetic model is proposed to describe pyrolysis.•The combined model is validated with the experimental measurements in the BFB.•Heating and pyrolysis times are obtained for various operating conditions.•Inverse relation of heating to pyrolysis time ratio with bed temperature was found.