Valorization of <i>Prosopis juliflora</i> Woody Biomass in Northeast Brazilian through Dry Torrefaction

Abstract

Torrefaction has been investigated to improve the desirable properties of biomass as solid biofuel, usually used in natura as firewood in several countries. This paper has the main objective to present a broad characterization of the biomass Prosopis juliflora (P. juliflora), investigating its potential as a solid biofuel after its torrefaction process. The methodology was based on different procedures. The experimental runs were carried out at 230, 270, and 310 °C for 30 min, using a bench-scale torrefaction apparatus, with an inert atmosphere. In order to investigate the effect of temperature in constant time, torrefaction parameters were calculated, such as mass yield, energy yield, calorific value, base-to-acid ratio (B/A), and the alkaline index (AI). The physicochemical properties of the torrefied samples were determined and thermogravimetric analysis was used to determine the kinetic parameters at four different heating rates of 5, 10, 20, and 30 °C/min. Pyrolysis kinetics was investigated using the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) isoconversional methods. Highly thermally stable biofuels were obtained due to the great degradation of hemicellulose and cellulose during torrefaction at higher temperatures. The highest heating value (HHV) of the samples varied between 18.3 and 23.1 MJ/kg, and the energy yield between 81.1 and 96.2%. The results indicate that P. juliflora torrefied becomes a more attractive and competitive solid biofuel alternative in the generation of heat and energy in northeast Brazil.

Keywords

• biomass
• thermal treatment
• pyrolysis
• torrefaction
• kinetics
• biofuel