Abstract
Thermogravimetry analysis was carried out for thermally decomposed woods. The carbonizations of a wood were performed by using superheated water vapor, air, nitrogen gas, and CO2 gas and the effects of the gases on the carbonization were examined in detail. The furnace temperature was 623 K and the pyrolysis time was 100 min with a heating time at about 30 min. Japanese Hinoki was used as a wood sample. The yield of the wood carbonized by using superheated water vapor was about 33.9 wt%, which was smaller than those of nitrogen gas carbonization; 40.2 wt% and CO2 gas carbonization; 38.5 wt%. The decompositon rate of the wood with the superheated water vapor treatment was faster than that with the nitrogen gas or CO2 gas treatment. Oxidation and combustion reactions took place in the air condition. The kinetic parameters of the thermal decomposition were determined from experimental thermogravimetric curves using a first-order reaction equation and the calculated activated energies of the decomposition were 62.6, 72.6, and 69.1 kJ mol-1 for the superheated water vapor, nitrogen gas, and CO2 gas treatments, respectively. The rate constant of the superheated water treatment was found to be larger than that by nitrogen gas or CO2 gas treatment at low temperatures below 550 K. These results suggest that hydrolysis decomposition occurred in the superheated water vapor treatment. A mathematical model of the decomposition reaction of the wood was presented using a first-order reaction equation and a nonlinear thermal conduction equation. The model showed good agreements with the experimental results of thermal decomposition of the hinoki woods.
