Determination of Combustion Kinetic Data of Some Agricultural Wastes from the Galicia-Northern Portugal Euroregion
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ORIGINAL PAPER
Determination of Combustion Kinetic Data of Some Agricultural Wastes from the Galicia‑Northern Portugal Euroregion Simão Mateus1 · Victor Ferreira1 · Aida Sanches1 · Pedro Resende2 · Carlos Pinho3 Received: 21 April 2020 / Accepted: 3 September 2020 © Springer Nature B.V. 2020
Abstract This work concerns the study of the combustion kinetic characteristics of chars made from three different biomass species, vine and kiwi pruning wastes, and gorse from forest cleaning process in a fluidized bed combustor, operating in the bubbling bed regime, at four bed temperatures, 750, 820, 850 and 920 °C. Batches of the original biomass pellets were carbonized in a nitrogen fluidized bed, either at 900 °C, for the kiwi and vine pellets, or at 800 °C for the gorse pellets. To acquire complete information on the combustion behaviour, different sizes of the char particles were subsequently burned in a bubbling fluidized bed. The evolution of the overall combustion resistance, and information on the combustion control were obtained. It was observed that for the kiwi and vine chars, the combustion was controlled through a combination of diffusion and kinetics, while for the gorse char the combustion was diffusionally controlled. In addition, the pre-exponential factors and activation energies were obtained for the kiwi and vine chars, by applying the Arrhenius law to the kinetic data for each char. Activation energy values of 246.16 kJ/mol for the kiwi char and of 155.02 kJ/mol for the vine char were obtained.
* Carlos Pinho [email protected] Simão Mateus [email protected] Victor Ferreira [email protected] Aida Sanches [email protected] Pedro Resende [email protected] 1
INEGI, Campus da FEUP, Rua Dr. Roberto Frias, 400, Porto 4200‑465, Portugal
2
ProMetheus, ESTG, Instituto Politécnico de Viana do Castelo, Viana do Castelo 4900‑347, Portugal
3
CEFT‑DEMEC, Universidade do Porto, Rua Dr. Roberto Frias, s/n, Porto 4200‑465, Portugal
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Waste and Biomass Valorization
Graphic Abstract
Keywords Biochar · Bubbling fluidized bed · Combustion · Diffusion · Kinetics List of symbols Greek Symbols � Δh Enthalpy of combustion for the carbon to CO oxidation [kJ/kg] 𝜙p Sphericity of a char particle [–] 𝜎 Stefan–Boltzman constant [W/(m2 K4)] 𝜀p Emissivity of a char particle [–]
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Roman Symbols A Pre-exponential factor [m/s] Ap Surface area of a char particle [m2] As Surface area of a sphere with the same volume [m2] cpg Constant pressure specific heat of gas [J/(kg K)] Cp Molar concentration of oxygen in the particulate phase [kmol/m3]
Waste and Biomass Valorization
Cs Molar concentration of oxygen at the particle surface [kmol/m3] d Corrected spherical diameter of the particle [m] ds Diameter of a sphere with the same volume [m] D Diameter of a cylindrical particle [m] DG Oxygen diffusivity in the air [m2/s] Ea Activation energy [J/mol] fc Mass fraction of carbon [–] fcf Mass fraction of the fixed carbon [–] fcv Carbon mass fraction in the volatiles
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