Thermal decomposition characteristics and kinetic analysis of biomasses and their blends: A comparative study using various models

The pyrolysis and co-pyrolysis of Picual Olive Pomace (POP), Manzanillo Olive Pomace (MOP), Palm Fronds (PF), and their blends were studied using thermogravimetric/differential thermal gravimetric/differential thermal analyser (TGA/DTG/DTA) techniques at different heating rates (β). Six isoconversional models have been applied to predict the variation in activation energy with conversion. Independent parallel reaction scheme (IPRS) model was used to estimate the kinetics of four independent multi-parallel reactions. The reliability and validity of the IPRS model was confirmed through the master plots and integral Coats and Redfern model solutions. In addition, thermodynamic parameters have been calculated for the four parallel reactions based on their predicted kinetic values from the IPRS solution. Iso-conversional models solutions showed that there is a significant activation energy variation (ΔE> 20 % Eav) for the studied materials which confirms that the pyrolysis process is a complex multi-step reaction. The four pseudo-component reactions have well-fitting experimental and theoretical master plots for each reaction in a certain order of reactions similar to those obtained from IPRS model solution which confirm its reliability. The bed agglomeration index (BAI) and fouling index (FI) data showed that the slagging and fouling tendencies of the studied samples were classified as low and medium, in contrast to the slag viscosity index (SR). The results showed that when the heating rate increases, the mean reactivity (RMtot) increases. The sequence of increases in the reactivity of the materials during the devolatilization is as follows: Blend (1), POP, Blend (2), MOP, and PFR, in that order. The resulted high entropy values of all samples indicate higher reactivity and a shorter time to attain the activated complex and, hence, a shorter overall time of reaction.