Particle pyrolysis modeling and thermal characterization of pecan nutshell

A mathematical model for the pyrolysis process of pecan nutshells in a thermogravimetric balance was developed. The model included the application of mass and energy conservation equations that assumed that the milled nutshell had a spherical shape. A kinetic progressive conversion model (PCM) for the main biomass components was proposed in this work. The pecan nutshell was characterized through elemental and ultimate analyses. Additionally, thermogravimetry (TG) and differential scanning calorimetry (DSC) studies were conducted under pyrolytic conditions. The kinetic parameters and mass transport properties were obtained as a function of the particle size by adjusting the proposed model to fit the TG and DSC experimental data through a simplex optimization method. The best fitting of the proposed model was for particle diameters of 3 and 4 mm. The calculated activation energy values for hemicellulose were found to be very high when compared with values from other works, while the values for the cellulose and lignin were more similar. These results can be helpful in scaling up a pyrolytic pecan nut process, as well as improving the understanding of the phenomena involved during the pyrolysis.