Insights into Reaction Modeling and Product Characterization of Hazelnut Shell Pyrolysis

Abstract

This study presents the first in-depth, comprehensive evaluation of the kinetic parameters, reaction mechanism, and product formation during pyrolysis of hazelnut shells, the main biowaste from the hazelnut processing industry. The pyrolysis behavior of hazelnut shells and released gaseous products were studied using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. Experiments were carried out under nitrogen flow at heating rates of 10 degrees C min(-1), 20 degrees C min(-1), and 30 degrees C min(-1). The pyrolysis of hazelnut shells was divided into three phases, with an active pyrolysis stage occurred between 200 and 565 degrees C. The distributed activation energy model and iso-conversional model-free KAS, OFW, Straink, and Vyazonkin methods were applied to calculate the activation energy. The trend of activation energy is consistent for all the implemented models, and predicted activation energy varied from 136 to 155 kJ mol(-1) for model-free methods. The values of the mean activation energy and the pre-exponential coefficient calculated by the DAEM method were 149.24 kJ mol(-1) and 2.29E + 12 min(-1), respectively. The model-fitting master plots method was used to determine the reaction mechanism. The major gaseous products released during the thermal degradation were CO2, CO, phenol, H2O, CH4, C-O that arose from various complex reactions such as cracking, re-polymerization, or condensation. Thermal analysis, kinetic study, and product characterizations indicated the multistage reaction mechanism of hazelnut shell pyrolysis. The results of this study can be applied as inputs in the design of the pyrolysis process systems using hazelnut shells as biomass feedstock.