Effect of compression pressure on lignocellulosic biomass pellet to improve fuel properties: Higher heating value

• Higher heating value does not show consistent relationship with moisture and ash content.
• Pellet density increases radically at first and then gradually with increasing pressure.
• Weight loss during pelletization is principally related with the moisture content of biomass.
• Higher heating values of biomass pellets show no definite trend with increasing pressure.
• Pattern of bonding between biomass particles is suggested for the anomaly in heating value.

Compaction of biomass through pelletization leads to the formation of a carbon neutral fuel with higher density. The aim of this present work was to determine the extent of influence of pelletizing pressure on pellet density and alteration of higher heating value (gross heat of combustion) of pellets. Eight species of wood sawdust and different compression pressures were used in pellet preparation. The sizes and mass of compressed samples were measured to calculate the pellet density and oxygen bomb calorimeter were used to determine higher heating value. Pellet density was seen to increase radically at first and then gradually with the increase of pelletizing pressure. In case of heating value, with increase in pelletizing pressure no definite trend was observed among the compressed biomass species. The pattern of bonding between biomass particles is the main factor influencing heat of combustion. The alteration of chemical composition, quantity of moisture and extractives, prevalence of favourable condition for lignin flow, migration of extractives to the surface and the presence of inter-particle gaps and voids affect the bonding quality. These factors differ from one biomass species to another which eventually leads to variation in higher heating value pattern.