Chloride leaching of eucalyptus wood particles by water for pellets production

Abstract

The impacts of climate change caused by the consumption of fossil fuels have encouraged the reduction of greenhouse gas emissions. The use of forest biomass for the pellets production is an alternative for energy generation. However, the high chloride content present in this forest biomass has caused human health and economic problems, which are factors that restrict the export of pellets. The main objective of this work was to reduce the chloride content in eucalyptus wood intended to produce pellets, by leaching the particles with water. Different parts of the eucalyptus tree (bark, branches, leaves, heartwood and sapwood) were characterized, and the biomass stock was determined. The chloride content determination was carried out using the selective chloride electrode and ion chromatography methods. Leaching was performed using a water/wood ratio of 25, 50, 75 or 100 L kg−1. The higher heating value (HHV) of the bark (18.47 MJ/kg), branches (20.01 MJ/kg) and leaves (22.04 MJ/kg) met the requirements of ISO 17225–2. However, their ash (1.91–4.32 %) and chloride content (0.120–0.627 %) were above what is allowed by the standard. The sapwood showed a higher content of volatile matter, ash and holocellulose, while higher values of HHV, fixed carbon, lignin and extractives content were observed for the heartwood. The chloride content present in heartwood was lower than that of sapwood and did not meet the requirements for ISO 17225–2 (≤0.03 % for B and ≤ 0.02 % for A pellets). In general, particle leaching did not significantly affect the energetic properties of wood. Leaching the particles with the lowest water/wood ratio (25 L/kg) was sufficient to remove chloride ions and meet the requirements of ISO 17225–2.