Carbonization of waste wood from demolished wooden house and development of charcoal utilization: The effect of carbonizing conditions on the fundamental properties and moisture adsorption characteristics of charcoal

In order to utilize charcoal made from waste wood of low-quality involved plywood and wooden board mainly as humidity control material for under floor, studies were conducted on (a) the effect of carbonizing conditions (atmosphere, and temperature) and wood quality on fundamental properties and moisture adsorption characteristics of the charcoals and (b) improvement of the moisture adsorption characteristics by fixing salts into the charcoal. The results are summarized as follows: 1) Of the fundamental properties, the yield of the charcoals decreased as carbonization temperature increased from 300degC to 900degC. On this occasion, the yield of charcoals carbonized in a very low oxygen atmosphere declined almost rectilinearly, whereas there was little difference in the yield of the charcoals prepared in a nitrogen atmosphere between 600degC and 900degC. As regards the fluctuations of proximate analysis value of the charcoals with the rise in carbonization temperature, the volatile content greatly decreased, the fixed carbon content drastically increased, and the ash content increased slightly. The specific area of charcoals prepared in a very low oxygen atmosphere was enlarged almost rectilinearly as carbonization temperature increased, while the specific area of the charcoals prepared in a nitrogen atmosphere showed the maximum value at 600degC. The fundamental properties of the charcoals were not greatly different based on wood quality. 2) Concerning the effect of carbonizing conditions on moisture adsorption characteristics of the charcoals, the moisture content of the charcoals put in environments with both high humidity and low humidity tended to be higher, as carbonization temperature was higher. In an environment with high humidity, the moisture content was observed to be higher in the charcoals prepared in a very low oxygen atmosphere compared to those prepared in nitrogen atmosphere, and the difference of the moisture content was larger as carbonization temperature was higher. The moisture adsorption characteristics of the charcoals were not greatly different based on wood quality. However, the humidity-control capacity (difference in the equilibrium moisture content between high-humidity conditions and low-humidity conditions) of the charcoals of carbonized waste wood of low-quality was about 5% at its highest, and the value was lower than about half of that of usual coniferous wood. 3) The effect of salts fixed into the charcoal of carbonized waste wood of low-quality on moisture adsorption characteristics was remarkable. The humidity-control capacity of the treated charcoal increased the value by about 10 times in the case of fixed calcium chloride, and about 8.5 times in the case of fixed sodium carbonate compared with untreated charcoal.