Textural and fuel characteristics of the chars produced by the pyrolysis of waste wood, and the properties of activated carbons prepared from them

• Silver fir, holm oak, stone pine and Pyrenean oak waste woods were pyrolyzed in a pilot scale plant.
• The textural properties of the chars produced are described.
• The fuel and combustion properties of the char were similar to those of commercials coals.
• The activated carbons produced from these chars (CO2 activation at 800 ̊C) had BET surface areas of 543–815 m2 g−1.

Chars were obtained by the pyrolysis of waste wood samples of different origin – silver fir (Abies alba), holm oak (Quercus ilex), stone pine (Pinus pinea) and Pyrenean oak (Quercus pyrenaica) – at 600 ̊C in a pilot scale installation. The thermo-chemical characteristics of the resulting materials were fully investigated using a combination of standard techniques. The char yield ranged from 23 wt% to 29 wt%, depending on the precursor wood. The recovery of C achieved was 42–51 wt%, increasing with the hemicellulose content of the wood. In addition, the chars had low volatile matter (8–12 wt%) and ash (2.0–8.5 wt%) contents. The higher heating values of the chars were relatively high (31–35 MJ kg−1) and comparable to that of a semi-anthracite (silver fir and stone pine chars) or medium-volatile bituminous coal (holm and Pyrenean oak chars). Their combustion intervals, and ignition, volatilization and burnout temperatures, were similar to those of commercial coals. The chars had a microporous structure (pore size < 2 nm) with BET surface areas in the range 314–405 m2 g−1. Their treatment by CO2 at 800 ̊C resulted in activated carbons with pore sizes below 0.89 nm and BET surface areas of 543–815 m2 g−1.

Different types of waste wood were pyrolysed in a pilot scale plant to obtain: (1) non-condensable gases; these were used to produce electricity via a gas turbine, (2) bio-oils of different potential uses, and (3) chars. These chars can be used as fuels that might substitute coal, or converted into activated carbon.Figure optionsDownload as PowerPoint slide