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

ANABEL FERNANDEZ BRIZUELA; RODRIGO TORRES SCIANCALEPORE; ERICK TORRES; DANIELA ZALAZAR GARCÌA; ROSA RODRIGUEZ; GERMÁN MAZZA

Sanya

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

Society of Advanced Science and Engineering (SASE)

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