Effects of Compressing Pressure on Briquettes Made from Woody Biomass

Abstract

Biomass, in particular wood, has become a fundamental renewable energy source that can replace fossil fuels in many applications, from eating to electricity production. Wood chips are one of the most popular biomass fuel in latest cogenerating plants and in small heating systems. This fuel has low bulk density and needs large volumes in handling and transport operations. These obstacles, common to many biological residues, can be overcome by densification. This study reports the effects of the compressing pressure on the demand of energy required in briquetting, final bulk density and durability of briquettes manufactured from wood chips. An hydraulic press was used to produce briquettes in controlled conditions. Five pressure levels (20, 30, 50, 80 and 110 MPa) and three different types of wood chips (PC - hybrid poplar, CC - chestnut, and MC - mixture of spruce white pine) were investigated. The study shows that the different pressures adopted significantly affect the specific compression energy, the final density and the durability of the compacted samples. Equations were developed to predict compact density and the specific compression energy required by the densification process. The specific compression energy values obtained in this study (18-58 kJ kg-1) were significantly lower than the specific energy required to manufacture pellets made from biomass feedstock (typically 19-90 kJ kg-1). Furthermore, chestnut wood chips with pressure at 110 MPa resulted in the maximum briquettes bulk density and durability.