A lumped kinetic model for banana peel combustion

• TG and DTG curves of banana peels and related chars are measured in air.
• Differences with woody biomasses are significant.
• A lumped four-step combustion mechanism is developed.
• SEM analyses reveal a scarcely porous structure.
• EDX analyses reveal the presence of deposits rich in potassium and chlorine.

Thermogravimetric analysis in air of banana peel and related chars, produced at temperatures of 700–950 K, is carried out. Compared with wood, the two consecutive processes of devolatilization and combustion take place over wider temperature intervals. Two peaks are evident for both the first zone (instead of a shoulder and a peak) and the second zone (instead of a single peak). The analysis of integral and differential data, obtained for a heating rate range of 5–20 K/min, leads to a kinetic model consisting of four reaction steps. The two devolatization steps require low activation energies (82 and 86 kJ/mol), consequent to the presence of a large number of chemical components (starch, sugars, pectin, lipids and proteins, in addition to cellulose, hemicelluloses and lignin). The first and chief combustion step is also described by a low activation energy (112 kJ/mol) whereas the second one requires an activation energy (180 kJ/mol) coincident with that typically estimated for lignocellulosic chars. SEM and EDX analyses reveal a scarcely porous microstructure with a few large channels immersed into a honeycomb-type tissue scattered with deposits rich in potassium and chlorine.