An improved predictive model to determine the thermal degradation of lignocellulosic materials at low temperature (Torrefaction) ranges.

This study introduces an improved computational procedure to determine the thermal degradation of biomasses when submitted to a torrefaction process. The novelty consists in integrating a summative kinetic model approach with an enhanced finite difference scheme. This is achieved by defining timing updated parameters to account for both the extent of conversion and the evolution of the fibers composition. As main result, the proposed method enhances the exploitation of the summative assumption considering that the predictive accuracy of the model sets within 5% as maximum error. Furthermore, the adopted discrete approach contributes to generalize the TGA set up going beyond the conventional heating programs usually limited to isothermal and constant heating rate constrains. Due to these constitutive improvements, the proposed computational approach looks promising for investigations involving both kinetic analysis and thermal processes design including torrefaction.

Biomass as an energy source: thermodynamic constraints on the performance of the conversion process.

In the present work an equilibrium model (gas-solid), based on the minimization of the Gibbs energy, has been used in order to estimate the theoretical yield and the equilibrium composition of the reaction products (syngas and char) of biomass thermochemical conversion processes (pyrolysis and gasification). The data obtained from this model have also been used to calculate the heating value of the fuel gas, in order to evaluate the overall energy efficiency of the thermal conversion stage. The proposed model has been applied both to partial oxidation and steam gasification processes with varying air to biomass (ER) and steam to carbon (SC) ratio values and using different feedstocks; the obtained results have been compared with experimental data and with other model predictions obtaining a satisfactory agreement.