An investigation on the kinetic behavior and thermodynamic parameters of the oxy-fuel combustion of Brazilian agroindustrial residues

摘要

The global agroindustrial sector has generated a large amount of waste and received special attention in several studies, since it is a promising source of clean and renewable energy production. The present study evaluated three important Brazilian agroindustrial residues, namely sugarcane bagasse, rice husks, and coffee husks through thermogravimetric analysis (TG/DTG curves) during oxy-fuel combustion processes with 20 and 40 oxygen concentrations. A kinetic analysis involving isoconversional methods, i.e., Friedman (FRI), Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose determined the activation energies for the main thermal degradation steps of hemicellulose (HE), cellulose (CE), and lignin (LI), showing good agreement of the methods. Kinetic data were also used for the determination of thermodynamic parameters ( UDelta;H, UDelta;G, and UDelta;S). The positive values for UDelta;H and UDelta;G for both atmospheres revealed the occurrence of non-spontaneous and endothermic conversion, respectively, whereas the negative ones for UDelta;S showed a more complex conversion. The activation energy (E-a) values from agroindustrial residues were lower under 60CO2-40O-2 atmosphere, ranging from 38.7 to 166.6 kJ mol(-1) for all thermal degradation steps analyzed; when compared to the 80CO2-20O-2 atmosphere, such values varied from 61.6 to 218.7 kJ mol(-1). The kinetic behavior and thermodynamic parameters of agroindustrial residues have proven promising for the bioenergy production with different biomasses in oxy-fuel combustion processes.