Dependence of the characteristics of wood charcoal on the carbonization conditions

We examined the characteristics of wood charcoal generated from ubame oak (Quercus phillyraeoides) and sugi (Cryptomeria japonica) at different carbonization temperatures up to 1200 °C with different heating rates of 0.1, 1 and 10 °C/min. In general, pyrolysis was achieved at a lower temperature when a lower heating rate was applied for both of the wood species. At temperatures greater than or equal to 400 °C, Sugi showed a relatively smaller weight loss at a heating rate of 1 °C/min compared to the other hearing rates while the amount of the weight loss changed little regardless of the heating rate for ubame oak. At 600 °C, a lower heating rate resulted in a greater char yield for sugi while a heating rate of 1 °C/min produced the greatest char yield for ubame oak. At this temperature condition, the largest specific surface areas obtained were 827 m²/g at 10 °C/min and 447.9 m²/g at 1 °C/min for sugi and ubame oak, respectively. At 1200 °C, the greatest char yield was obtained at a heating rate of 1 °C/min for both wood species, and a lower heating rate produced a greater specific surface area for sugi while a porous structure was rarely observed in ubame oak. The X-ray diffractograms of the charcoals of the two wood species showed the noncrystalline structure of graphite carbon for all the tested hearing rates. The bending strength of the charcoal was the greatest at heating rates of 1 °C/min and 0.1 °C/min for sugi and ubame oak, respectively. Furthermore, a higher temperature provided a greater compressive strength of the charcoals. The modulus of elasticity changed little with changing carbonization temperature or changing heating rate.