Thermal Degradation and Kinetic Characterizations of Jatropha Waste under Isothermal and Dynamic Experiments

Abstract:

Thermal decomposition characteristic of waste material from oil extraction of Jatropha (physic nut), including shell and kernel, was investigated using thermogravimetric analysis (TGA) and pyrolysis experiments. Effects of heating rate (5-90°C/min), reaction temperature (500-900°C) and hold time at final temperature (3-15 min) on the feature of thermogram, kinetic parameters as well as product distribution were evaluated. Thermal conversion of this residue composed of cellulose, hemicellulose, and lignin degradation steps with maximum weight losses around 250 to 450°C. The order of reaction increased with temperature from 0.28 at 250°C to 0.81 at 450°C. The activation energies ranging from 105-184 kJ/mol depend on the stage of devolatilization. The amount of gas product increased with temperature with the expense of reducing char and liquid from secondary heterogeneous cracking reactions. More than 14% of hydrogen in residue was converted to H2 during pyrolysis at 900°C. Major hydrocarbon gases are those of C4+ species with measurable amount of CH4 and C2 derivatives. Increase in reaction temperature can lead to a noticeable increase of hydrogen and hydrocarbon gas yields. Addition of catalyst and steam would promote the formation of fuel gas from this waste material.