Two different waste derived by-products were examined and compared. Based on the thermogravimetric tests performed, it was proved that their decomposition occurs in two weight loss steps represented by two shoulders in the derivative thermogravimetric curves. The first shoulder is attributed to the devolatilisation of hemicellulose, cellulose and lignin and the second one to the plastic fraction of the waste. Similarities in the degradation behaviour were observed for both wastes, despite of their different origin. Increased plastic fractions resulted in slightly higher conversions and lower pyrolysis rates. Enhanced lignocellulosic fractions led to higher rates during combustion. The lignocellulosic fraction was increased proportionally to the inorganic residue remained after combustion. A wide variation of weight losses was attained even in Refuse Derived Fuel (RDF) samples of the same origin, while stronger deviations were observed in the decomposition of the plastic fraction. The independent parallel, first order, reactions model was elaborated for the kinetic analysis of the pyrolysis results. The thermal degradation of the refuse derived fuel samples was modeled assuming four parallel reactions corresponding to the devolatilisation of cellulose, hemicellulose, lignin and plastics. Increased activation energies were calculated for the plastics fraction, while lignin presented the lowest contribution in the pyrolysis of the samples. Generally, both RDF samples presented similar kinetic constants despite their heterogeneity.
Keywords: combustion, pyrolysis, RDF, thermogravimetry, waste