Effect of a mild torrefaction for production of eucalypt wood briquettes under different compression pressures

Published Date
July 2016, Vol.90:181–186, doi:10.1016/j.biombioe.2016.04.007

Research paper

Title 

Effect of a mild torrefaction for production of eucalypt wood briquettes under different compression pressures

• Author 

• Solange Araújo ^a,,,
• Mariana Almeida Vilas Boas ^b
• Duarte Miranda Neiva ^a
• Angélica de Cassia Carneiro ^b
• Benedito Vital ^b
• Marcelino Breguez ^b
• Helena Pereira ^a

• aCentro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal
• bUniversidade Federal de Viçosa (UFV), Avenida Peter Henry Rolfs s/n, 36571-000 Viçosa, Minas Gerais, Brazil

Received 19 October 2015. Revised 1 April 2016. Accepted 11 April 2016. Available online 26 April 2016.

Highlights

• •
  The two studied eucalypt woods showed potential for production of briquettes.
• •
  Briquetting compacting pressure had little influence on their properties.
• •
  Lowest pressure produced good quality briquettes for untreated heat treated wood.
• •
  Mild torrefaction increased particles and briquettes' energy potential.
• •
  Briquettes' density, dimensional stability and hygroscopicity improved with treatment.

Abstract

The heat treatment of wood (i.e. torrefaction) followed by densification of wood particles (e.g. by briquetting) may be used as a process to improve homogeneity and energy properties of wood for use as a solid fuel. The wood of Eucalyptus grandisand Eucalyptus spp. were treated at 180, 200 and 220 °C for 60 min under a nitrogen atmosphere. Briquettes were produced with untreated and heat-treated wood particles using 120 °C, for 7 min pressing and 6 min cooling time, under pressures of 6.9, 10.3 and 13.8 MPa. The briquetting compacting pressure showed no significant influence on the briquettes properties. Briquettes density was similar for all cases presenting 1.14 g cm⁻³ for Eucalyptus spp. and 1.06 g cm⁻³ for Eucalyptus grandiswood. A mild torrefaction of the wood at 200–220 °C increased the potential energy of the particles and briquettes, showing an improvement in their density, dimensional stability and hygroscopicity. Briquettes produced from heat-treated Eucalyptus spp. wood presented higher energy density (24.79 GJ m⁻³) at 200°C-treatment when compared with untreated wood (20.76 GJ m⁻³). Regarding E. grandis, briquettes produced with heat-treated (200 °C) particles showed only a marginal higher energy content than with untreated wood, 21.70 GJ m⁻³ and 21.38 GJ m⁻³, respectively. The two eucalypt woods showed differences regarding the heat treatment and briquetting, pointing out that the optimization of these processes should be specific for each species. However, a mild torrefaction of the wood particles decreased the differences between materials which might be useful as a process to increase feedstock homogeneity when using mixed raw-materials.

Keywords

• Heat treatment
• Wood particles
• Densification
• Eucalyptus grandis
• Torrefaction
• Briquettes properties

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• ∗ 
  Corresponding author.

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