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

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.