Effects of Extractives on the Physical Characteristics of Scots Pine Sawdust Fuel Pellets

In order to evaluate the effect of extractives on particle bonding, pellets were produced from extracted and nonextracted Scots pine sawdust in a laboratory piston press pelletizer. In the experiment, the raw material and process parameters were fresh (nonextracted) and acetone-extracted sawdust, sawdust moisture content (6% and 12%), piston pressure (70 and 150 MPa), and press temperature (100 degrees C and 180 degrees C). The resulting pellets were evaluated and compared for density, compression strength, and moisture sorption. The relationship between factors and responses was evaluated by partial least squares regression. In the present study, it was found that pressure and temperature had a positive effect on both pellet density and compression strength. Extracted sawdust gave pellets with a higher density and compression strength than pellets made from nonextracted sawdust. Moisture sorption between the produced pellets showed no significant differences. Results of this study provide a plausible explanation for why pellets produced from stored sawdust with low amounts of extractives have better strength properties than pellets produced from fresh sawdust.