Optimum Torrefaction Range for Macaw Husks Aiming Its Use as a Solid Biofuel

摘要

Biomass feedstock is broadly available in many countries, and a significant amount of residual biomass comes from agriculture and forest crops. This study aims to identify a consistent criteria for optimize Macaw husks torrefaction process maximizing the energy content and minimizing the mass loss. The optimization criteria is based on the severity factor (SF), HHVTorrefied, and eta(Solid-Yield). The energy density (rho(Energy)) does not provide consistent and indisputable evidence as an optimization criteria; the same applies to energy-mass co-benefit index (EMCI) and eta(Energy-Yield). This investigation combined few temperatures (180 degrees C, 220 degrees C, and 260 degrees C) with different residence times (20, 40, and 60 min) and found that the optimum torrefaction range for Macaw husk is 220 < T (degrees C) < 240 and 10 < t (min) < 40. The best experimental result was 220-40 (dry torrefaction at T = 220 degrees C and t = 40 min) corresponding to SF similar to 5.14 and HHVTorrefied similar to 21.71 MJ/kg (eta(Solid-Yield) similar to 0.86 and HHVRatio similar to 1.14). As the raw material has small rho(Bulk) or rho(Energy), the authors suggest the use of a densification process previously to torrefaction. The obtained solid final product had high-quality biofuel following properties: FCdb, H/C, and O/C ratios, high heating value (HHV). The gain and loss optimization method seems promising to identify the optimum torrefaction parameters for any biomass species and the obtained optimum temperature is not far from the ones available as waste heat in industrial processes.