Torrefaction of pelletized corn residues with wet flue gas

Corn residue pellets were torrefied with wet flue gas, simulated by steam (0-21% v/v), CO₂ (12% v/v), and O₂ (4% v/v), balanced with N₂ as reactive gas, in a fixed bed reactor at 260 °C of temperature and at 10-40 min of residence time. The distribution and yields of torrefied pellets, liquid, and gas products were examined. The microstructural changes of torrefied pellets were evaluated by Raman spectroscopy and scanning electron microscopy, while the components of gas products were analyzed by mass spectrometry. Residence time and steam concentration in the reactive gas were found to have significant effects on the products yield distribution, the porosity of the torrefied pellets, and the concentrations of CO, CH₄, H₂, and CO₂ in the gas products. At high steam concentrations, the decomposition reaction of hemicellulose and lignin in the raw pellets, and the formation of the graphene structures in torrefied pellets occurred faster.