Non-isothermal kinetic analysis of the devolatilization of corn cobs and sugar cane bagasse in an inert atmosphere

Abstract

Corn cobs and sugar cane bagasse are two of the most important agricultural residues in South Africa in terms of availability and potential for use as a bioenergy resource. The thermal devolatilization of samples of these two fuels in an inert atmosphere was studied by non-isothermal thermogravimetric analysis in the heating rate range of 10–50 °C min −1. Friedman's isoconversional method was applied using the AKTS Thermokinetics software to obtain the dependence of activation energy on conversion. The same method was also applied to the kinetic analysis of lignocellulosic pseudocomponents derived from the mathematical deconvolution of the original DTG curves. The results showed that apparent activation energy in the 0.1–0.8 conversion interval ranged from 170–225 kJ mol −1 to 75–130 kJ mol −1 for sugar cane bagasse and corn cobs respectively. The range of apparent activation energy obtained for the pseudocomponents representing hemicelluloses, cellulose and lignin derived from sugar cane bagasse were given as 200–300 kJ mol −1, 163–245 kJ mol −1, and 80–180 kJ mol −1, while for corn cobs the values were 85–110 kJ mol −1, 80–140 kJ mol −1, and 10–60 kJ mol −1 respectively. The derived thermokinetic parameters from both global and pseudocomponent analyses satisfactorily reproduced the experimental curves used for the analysis and could also successfully predict reaction progress at a heating rate outside what was used in the analysis. The fits obtained between simulated and experimental results were comparable to what has been reported in the literature based on conventional model-fitting techniques.