Pyrolysis of pellets made with biomass and glycerol: Kinetic analysis and evolved gas analysis

Glycerol is a co-product compound of biodiesel production with an interesting heating value. In this work pyrolysis kinetic parameters for a pellet made with a mass fraction of 90% sawdust and a mass fraction of 10% glycerol are derived through thermogravimetric analysis. A new parallel reaction scheme with four components (cellulose, hemicellulose, lignin and glycerol) is adopted and the kinetic triplet for each component is derived using a model fitting approach applied to this particular kind of pellet. The isoconversional method Kissinger-Akahira-Sunose is employed both to provide initial values for model fitting simulations and to check final results. Results show that activation energies and pre-exponential factors are respectively: 149.7 kJ mol−1 and 1.98*1011 s−1 for hemicellulose, 230.1 kJ mol−1 and 1.84*1017 s−1 for cellulose, 154.3 kJ mol−1 and 5.14*109 s−1 for lignin, 74.5 kJ mol−1 and 2.17*105 s−1 for glycerol with a first reaction order for all components, except for lignin (n = 2.6). Through evolved gas analysis it was demonstrated that the thermal degradation of glycerol contained in the pellet can increase hydrogen content in pyrolysis gases.