Abstract:

Objective: The relationships were explored between caloric values of bamboo charcoal and different species, ages and parts of bamboos under the same carbonization process, calorific values of bamboo charcoal were correlatively analyzed with their ashes, volatiles and fixed carbon contents, and the deduced empirical formula was also applied for calorific values calculation in order to provide guidance and reference for the industrialization and energy utilization of bamboo wood. Method: The calorific values of bamboo charcoals carbonized from various bamboo species were taken as the objects of this study. 24 bamboo species grown in Lin'an, Zhejiang Province, and 2-to 13-year-old moso bamboo grown in Anji, Zhejiang Province, were collected and carbonized under the same process. Applying the single-factor-control method, the calorific values and proximate analysis of bamboo charcoals which were carbonized by middle parts of 24 bamboo species and moso bamboos(2-13 years), and top, middle and base parts of 4-, 5-, 6-year-old moso bamboos were tested, respectively. The effects of species, ages and parts of bamboo on the calorific value and fixed carbon, volatile, ash content were studied. Test data were summarized to find whether the calorific value was significantly correlated with fixed carbon, volatile and ash content by SPSS software. The empirical formula was deduced based on the relationships between the carbonization temperature(T), calorific value(Q) and fixed carbon(C). Result: The calorific values of 24 kinds of bamboo charcoal were distributed in the range of 27.94-32.98 kJ·g^-1, the mean value was 31.10 kJ·g^-1, the standard deviation was 1.11; the fixed carbon content was 75.35%-92.59%, the mean value was 85.87%, and the standard deviation was 3.65; the ash content was 3.34%-15.98%, the mean value was 7.21%, and the average volatile content was 6.91%. The calorific value of the charcoal produced from 2-to 13-year-old bamboo was distributed in the range of 30.93-33.81 kJ·g^-1, and the standard deviation of the fixed carbon content, ash content and volatile content were all less than 5, respectively. For 4-, 5- and 6-year-old bamboo carbonized materials, the absolute difference of calorific value of each part was below 1.38 kJ·g^-1, and the relative difference was under 3%. The high calorific value of bamboo charcoal was positively correlated with fixed carbon content, but negatively correlated with ash content. According to the relationships between the carbonization temperature, calorific value and fixed carbon of bamboo charcoal, the deduced empirical formulas were as follows: Q=0.001 8C²-0.111C+28.099(R²=0.72), C=26.934lnT-93.122(R²=0.88). Conclusion: 1) The diversity exists between calorific value and proximate analysis of bamboo charcoals carbonized from different bamboo species, which depends on the structural characteristics of bamboo species. The calorific value of carbonized materials of the same bamboo species at the base is higher than that at the middle and top parts, which is attributed to the higher lignin content at the base. In addition, bamboo ages and growth parts have no significant influences on calorific value and proximate analysis. 2) There is a linear relationship between the calorific value of bamboo charcoal and the fixed carbon and ash content, of which the calorific value is positively correlated with fixed carbon content and negatively correlated with ash content. The deduced empirical formulas Q=0.001 8C²-0.111C+28.099(R²=0.72) and C=26.934lnT-93.122(R²=0.88).

Key words: bamboo species, bamboo age, bamboo part, calorific values, proximate analysis, empirical formula