Simulation and thermodynamic evaluation of woody biomass waste torrefaction

Abstract

Torrefaction is a thermochemical pretreatment that enhances biomass properties, improving energy density, decomposition resistance, and hydrophobicity, making it a viable alternative as biofuel. This study performed a thermodynamic assessment of the torrefaction process for urban forest waste, integrating experimental data with two-step reaction kinetic modeling to evaluate the torrefaction product yields and properties using Aspen Plus software. The process was modeled with a yield reactor, employing the Peng−Robinson equation to describe vapor-phase behavior and empirical correlations to predict solid-phase properties. Simulations were validated against experimental data for temperatures between 225 and 275 °C, achieving an absolute deviation of less than 5%. Energy consumption ranged from 368 kJ·h−1 for light torrefaction to 1853 kJ·h−1 for severe torrefaction. Process irreversibility varied from 326 kJ·h−1 (3% exergy destruction) in light torrefaction to 3993 kJ·h−1 (16% exergy destruction) in severe torrefaction. The research provides a robust model for torrefaction scale-up that is adaptable to diverse biomass feedstocks and process conditions, highlighting its potential for optimizing energy use and improving sustainability in biomass utilization.