2018 年 3 巻 p. 65-71
Commercial wood pellets are upgraded by the pyrolysis treatment in a wide temperature range of 378-773 K that includes both the torrefaction and carbonization temperature conditions. The trade-off relationship between apparent density and higher heating value of pyrolyzed wood pellets (PWP) is confirmed, which implies the existence of an optimum pyrolysis condition to produce PWP. The progression of pyrolysis is found to be identified by the mass yield of PWP. Noticing the color variation of PWP with the progression of pyrolysis, the relationship between the mass yield and CIELAB color parameters is examined. Two experimental correlations to estimate the mass yield are presented using the color coordinate, b* and the hue angle, h. From the comparison between predicted mass yields and experimental data, it is found that the experimental correlation using the hue angle can evaluate the mass yield with an accuracy of around ±10% in a wide range of mass yield between 0.2 and 1. Therefore, it is concluded that the hue angle can be one of the useful indicators for a nondestructive inspection method of PWP.
