Prediction Model of Internal Heat Generation During Wood Biomass Degradation

Le résumé fourni par la source

Torrefaction is a thermochemical process where the biomass is subjected to temperatures between 200and 300 °C in an inert or partially oxidative atmosphere to promote an energetic upgrade, adding value to this biofuel. Heat and mass transfer analysis is a complex transient problem that evolves an anisotropic medium with heterogeneous thermophysical properties during torrefaction. In addition, the processes advance with a complex set of degradation kinetics, developing endothermic and exothermic reactions that must be understood. Therefore, the present work aims to build a numerical model to analyze the thermodegradation kinetics and determine the heat generation within the biomass. The numerical modeling was established for Eucalyptus grandis biomass. First, a 0D kinetic model was built to predict the mass loss dynamics at one point (0D), applying a consecutive two-step reactions approximation discretized by the evolution of five pseudo-components. Second, an analysis of heat generation was established considering the solid degradation and organic groups that contemplate the released gases and their specific enthalpy. Finally, the processes were simulated considering the entire temperature range of torrefaction 200–300 °C for a 60 min treatment. The degradation prediction provided excellent goodness of fit with an R2>0.99 for all treatments. The calculated enthalpy of solid and volatile pseudo components formation presented reliable correlations (R2 > 0.99),providing the internal energy generation rate. The internal generation rates peaked between 20–40 min of treatment, the region where the biomass volatilization rate is maximum. The generation varied between approximately 25–400 W kg-1 of biomass, considering torrefaction treatment between 200–300 °C.

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