Biomass & Bioenergy, Vol.122, 322-330, 2019
Effects of moisture content during densification of biomass pellets, focusing on polysaccharide substances
In this study, we pelletized four different pure polysaccharides represented cellulose - Avicel, hemicelluloses-locus bean gum mannan and beech xylan and other polysaccharides - apple pectin, and three woods - pine, spruce and beech. All were pelletized at 100 degrees in a single pellet press unit with different level of moisture content from 0 to 15%. The maximal friction force and work required for compression and friction was analyzed together with the pellet density and hardness. The results showed that xylan pellets completely changed in color at 10% moisture content, and this also occurred to some extent with pectin pellets. The color of both Avicel and locus bean gum pellets were not affected at all. During compression, the results showed that water does not affect compression up to 5 kN, while above 5 kN water decreases the energy need for densification of Avicel, locus bean gum and woods. Above 5 kN the energy needs for compressing xylan and pectin increases with increased moisture content. The hardest pellets were produced from Avicel, while locus bean gum produced the weakest pellets. The study concludes that there is a significant difference in how water affects the two hemicelluloses, glucomannan and xylan, during densification.