Effect of torrefaction on combustion kinetic parameters of groundnut shell and maize stalk

Abstract

Torrefaction involves devolatilisation, depolymerisation and carbonisation of lignocellulosic biomass, which enhance its fuel properties and combustion efficiency. This study aimed at determining the effect of torrefaction on combustion kinetic parameters of groundnut shell and maize stalk. Kissinger–Akahira–Sunose (KAS) method was used to determine the combustion kinetic parameters (the activation energy and pre-exponential factor) of torrefied and non-torrefied groundnut shell and maize stalk. Torrefaction decreased activation energies and pre-exponential factors of both maize stalk and groundnut shell due to change in structure and chemical composition of the biomass materials. Torrefaction decreased the activation energy from 149.91 to 123.85 kJ/mol for groundnut shell and from 135.14 to 103.70 kJ/mol for maize stalk and the decrease in the activation energy signifies an increase in the reactivity. Also, torrefaction reduced the pre-exponential factor of groundnut shell and maize stalk from 7.43 to 2.78 min−1 and 1.65 to 2.42 min−1, respectively and this reduction in the pre-exponential factor signifies a change in the reaction pathways. The modeled and experimental data for the degree of conversion were in good agreement.