執行成果摘要
In this study, the trees of Mechelia formosana thinned from an area of the Plain Afforestation Program at Ping Tung were cut into segments 1 m in length for charcoal making. The specific gravity and moisture content were measured. The carbonization and chimney temperatures were separately measured with K-type thermocouples during the wood charcoal making and wood vinegar collecting in an earthen kiln. After discharging the charcoals, the yields were calculated by weighing. In order to investigate the properties of the wood charcoal affected by the differences in carbonization temperature in the earthen kiln, electric resistivity, pH, carbon content and true density tests were performed for the specimens sampled at different height positions. Quantities of the collected wood vinegar were measured periodically. The specific gravity, pH, acidity, tar content and component analysis of the wood vinegar were tested for the samples collected at different chimney temperatures.
The specific gravity and moisture content of Mechelia formosana was 0.49 and 61.02%,respectively. From the measured carbonization temperature at each measurement point in the kiln, a curve of different temperatures was obtained. Carbonization temperatures at the upper part of the kiln rose faster and earlier than those at the lower part did. Highest temperature at the upper part of the kiln reached ＞ 740℃ at the end of carbonization, whereas the temperature at the lower part was only 570℃. Yield of the wood charcoal was 27.10%. The refine degree of the wood charcoals ranged 1.9-6.2, and decreased significantly with increasing carbonization temperatures. The pH of wood charcoal was 8.57-9.42 and increased a little with an increase of carbonization temperature. The true density of wood charcoal increased with an increase of carbonization temperature. Yield of the wood vinegar was 10.49% in the charcoaling process. The quantity of wood vinegar collected at chimney temperatures below 100℃ made up 85.03% of the total, while the amount decreased notably at temperatures above 101℃. The specific gravity and pH of the wood vinegar increased with the increasing chimney temperatures. The acidity and tar content of the wood vinegar was not appreciably affected by the chimney temperatures. The compounds concentrations of acids, phenols, alcohols, neutral compounds ranged 51.2-59.5%, 19.8-22.6%, 15.7-20.6%, 5.3-6.4%, respectively, for wood vinegar collected at different chimney temperatures.