Abstract: By techniques of one-step and two-step carbonization, capped and uncapped carbonization, with carbon dioxide, nitrogen, oxygen, air and their mixture as atmosphere gas, respectively, pyrolysis experiments on the thinning wood of Chinese fir, one of the fastest growing tree species in Southern China, are carried out. With special focuses on basic pyrolysis process of its sawdust and the affecting patterns on carbonized materials under different carbonization conditions, comprehensive analyses on yield of carbonized material and variation patterns are conducted. Furthermore, in combination with element analysis, variation patterns of carbon, hydrogen, oxygen contents are also analyzed. The results reveal that the yield of the charcoal falls distinctly between 400-600℃, hereafter, the yield gets to constant. The charcoal yield of capped carbonization method is higher than that of the uncapped. Fixed carbon content of the charcoal in air atmosphere is higher than that in N₂ atmosphere, no matter whether the carbonized method is one-step or two-step. The reduction degree of charcoal in air atmosphere is higher than that in N₂ atmosphere. Moreover, the reductivity is increased with the rise of carbonization temperature.

Key words: wood charcoals, thinning wood of Chinese fir, carbonization mechanism