2017 年 4 巻 1 号 p. 16-00320
Noticing the color variation of torrefied woody biomass with pyrolysis process, a non-invasive method to estimate energy properties such as elemental contents, higher heating value and energy yield is investigated. When the torrefied biofuel is produced and utilized, the quality control concerning energy properties is indispensable. The energy properties of torrefied woody biomass are correlated with its mass yield, and the relationship between mass yields and colorimetric values defined by CIELAB is experimentally examined. The results obtained for torrefied Japanese cedar are as follows. (1) The energy properties of torrefied Japanese cedar are expressed by simple relations of mass yield. The optimum torrefaction condition to produce torrefied biofuel can be evaluated by the mass yield. (2) To estimate the mass yield of torrefied Japanese cedar, the experimental correlations with colorimetric values are proposed. In the case of the sap-wood and heart-wood samples for brightness, L* above 45, the mass yield is correlated with L*, and in the case of the sap-wood, heart-wood and bark samples for L* below 45, the mass yield is correlated with color coordinate, a*. From the comparison between predicted mass yields and experimental data, it is found that the proposed experimental correlations can estimate the mass yield within an accuracy of ±10%. Therefore, the energy properties of torrefied Japanese cedar is easy to be checked by using the present non-invasive estimation method with colorimetric values.
