Thermogravimetric analysis for characterization of the pellets produced with different forest and agricultural residues

Abstract

The pelleting of forest and agricultural materials, mainly because many residues from both industries can be used in this process, has been an alternative in obtaining added value products to energy generation. Thus, the aim of this study was to evaluate the energy quality of the pellets produced from forest and agricultural residues as raw materials and to verify the utility of the thermogravimetric analysis (TGA) and the differential thermogravimetric analysis (DTG) in characterizing the behavior of the pellets during the combustion process. Four residues were used: (1) Pinus spp woodchips, (2) apple pruning residues, (3) aciculated dry branches of Araucaria angustifolia and (4) A. angustifolia empty-seeds. Chemical composition of the raw materials was determined and the physical and energetic properties of the pellets were analysed. Plus, the proximate analysis of the pellets was carried out. The samples were submitted to TGA with a heating rate of 20ºC min-1 from room temperature to 1000ºC, in a N2 atmosphere. The variation of chemical composition of each residue was determinant in the characterization of each stage of the thermal degradation. Stages and events of the degradation were closely linked to the chemical and energetic nature of the samples. Use of TGA to characterize the thermal degradation of the pellets produced with different forest and agricultural residues was demonstrated as an efficient technique to quantify and qualify the events that occurred in each stage of the combustion of these biofuels.