Kinetic study of the combustion of pyrolysis biochar from walnut and almond shell bio-wastes

ANABEL FERNANDEZ; RODRIGO TORRES SCIANCALEPORE; ERICK TORRES; DANIELA ZALAZAR; ROSA RODRÍGUEZ; GERMÁN MAZZA

Sanya

Conferencia; 2023 International Conference on Chemical, Energy Science and Environmental Engineering (CESEE 2023); 2023

2023 International Conference on Chemical, Energy Science and Environmental Engineering

This work aims to study the combustion kinetics of biochar obtained from slow pyrolysis of walnut and almond shells at 873 K. Combustion experiments were conducted in a macro-TG reactor at three different heating rates (10, 15, and 20 K/min) and temperatures in the range of 298–1173 K under an oxidative atmosphere. The experimental results were modeled using a multi-step mechanism considering two different parallel reactions, corresponding to the thermal decomposition of two pseudo-components. The results indicated that the Kissinger-Akahira-Sunose (KAS) method provided the best R2, MSE, and AAD values.According to bioenergy indices, nut shells-based biochar (NSB) presented better characteristics as a biofuel feedstock due to its high energy density and low ash content.Based on the characteristic parameters of combustion performance obtained from TGA, the most favorable values of ignition, combustion, and burnout indices were obtained at the heating rate of 15 K/min, being the almond shells-based biochar (ASB) the one that obtained the greatest overall combustion performance.The activation energy for the first pseudo-component combustion ranged between 141.99 and 448.75 kJ/mol for the ASB and between 37 and 107.52 kJ/mol for NSB. In the case of the second pseudo-component combustion, the activation energy was between 11.97 and 44.55 kJ/mol for the ASB and between 12.33 and 33.25 kJ/mol for the NSB at 873 K, respectively. This research purpose was to analyze the fuel characteristics of biochar, the determination of the kinetic parameters of its combustion, and the assessment of the biochar potential as a clean solid fuel.