Grass biomass for energy use: experimental study and analytical model on the characterization of torrefaction and pyrolysis
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The aim of the present work is the characterization of torrefaction and pyrolysis carried out on common reeds (Phragmites australis), using advanced analytical techniques and kinetic modeling. Simultaneous thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis have been carried out on reeds from China and Italy. The evolved gases during the decomposition process have been analyzed by a coupled infrared gas analyzer (IR) and gaschromatography/mass spectrometer (GC/MS). Additional tests have been carried out setting an intermediate temperature plateau in order to assess the effect of a possible torrefaction stage. Different reed origins (China and Italy) and plant parts (stem and leaves) have been compared. The feedstock has been also characterized through elemental and thermal analysis. The results obtained have been used to calibrate a torrefaction kinetic model to predict the feedstock mass loss and the liquid/gas products yields. The kinetic model has also been tested simulating a reed torrefaction run occurring in a bench-scale apparatus, supplementing the chemical analysis with a thermal simulation of the reactor carried out through a finite elements approach. The results show that the proposed modeling approach allows the prediction of the reaction products with a satisfying degree of accuracy.