MECHANISM OF ADHESION AND INTER-PARTICLE BONDING IN WOOD PELLETS RELEVANT TO THE PRODUCTION OF GOOD QUALITY PELLETS

Anthony Anukam and and Jonas Berghel

Environmental and Energy Systems, Department of Engineering and Chemical Sciences, Karlstad University, Sweden

Abstract

Wood pellets are made from compacted sawdust and are used as fuel for household or commercial heat and power generation. The combination of low fuel costs and efficient heating devices make the use of wood pellets very cost-effective. However, the generation of high amounts of ash and smoke when wood pellets are used in combustion systems limit its application in these systems. This issue is mainly attributed to poor quality as a result of lack of understanding of the mechanism of adhesion and inter-particle bonding relevant to the production of good quality pellets. Adhesion and inter-particle bonding in wood pellets is such a complex event to comprehend as the nature of the bonds formed between the combining particles have not been explicitly described with certainty from a structural chemistry perspective due to lack of adequate research in this area. The conditions under which particles are compressed at elevated pellet press temperatures create strong bonds between compressing particles, the nature of these bonds remains incomprehensible. This study therefore attempted to develop theories that will facilitate the understanding of adhesion and inter-particle bonding in wood pellets relevant to the production of good quality pellets. This was achieved through the use of specialized analytical instruments for diagnosis of powdered and pelletized wood. This diagnosis not only revealed primary wood components and their properties but also showed how molecules and each individual element are bonded, their binding sites, and the nature of the bonds that exists in these structures as well as their relevance to quality parameters. The correlation between adhesion, inter-particle bonding and wood characteristics were established according to the bonding mechanism of primary components.

Keywords: Adhesion, inter-particle bonding, wood pellets.