Hygroscopic properties of densified softwood pellets

Hygroscopic properties of densified softwood pellets were examined, namely, equilibrium moisture content and swelling response to different humidities at room temperature. The pellets consisted of sawdust particles of spruce (Picea spp.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)) and lodgepole pine (Pinus contorta Dougl. ex Loud.). They were placed into desiccators of known humidities at room temperature. Moisture content, oven-dry basis, was determined and a linear relationship (R2=0.972) between equilibrium moisture content and humidity was found between 11% and 80% humidity. At 93% and near-100% humidity, the pellets disintegrated. The swelled diameters of the pellets, based on oven-dry diameter, were found to be non-linear with respect to humidity, and, despite the large statistical variation, the diameters at higher humidities were statistically greater.