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Pelletskvalitet - påverkan av råvaruegenskaper och tillverkningsprocess

Jirjis, Raida; Öhman, Marcus; Vinterbäck, Johan


The aim of this project was to study the effect of variations in raw material (sawdust) properties on pellets quality. The project included three parts. Part one dealt with a small-scale pelleting trial to study the effects of tree species, tree age (represented by stem diameter) and storage of raw material on pellets quality. In part two, data concerning characteristics of raw material and pellets quality were collected from two pellet manufacturers using sawdust from spruce and pine respectively. The objective of part two was to analyse the relationship between raw material properties, process parameters and fuel quality using multivariate data analysis. Part three involved a questionnaire dealing with seasonal variations in raw material properties, process parameters and pellet quality during one year of commercial production of pellets. Sawdust from Pinus sylvestris and Picea abies was used in part one of the project. A number of physical and chemical properties of various raw materials including sawdust produced from small and large diameter stocks of pine and spruce, fresh as well as stored for four and eight months, were analysed. The study included a storage trial during which temperature development and dry matter loss were determined. The results showed that changes in heating value and ash content of various materials during storage and after pelletisation were minimal. Average dry matter loss after eight months of storing sawdust varied between 3.3-4.6 % (dry weight basis). The relative concentration of lignin in raw material was clearly increased during storage but remained unchanged after pressing the material into pellets. The content of total extractives differed clearly between the two species especially after storage. Sawdust from fresh and 4-months stored pine was pelletised using a small-scale press. Due to technical problems we were unable to pelletise 8-months stored sawdust from both pine and spruce. The large variations within the raw material properties and the inability to produce and compare pellets from both species limited the possibility to draw conclusions concerning the correlation between raw material characteristics and pellets durability. However, with the help of the detailed information collected through the other parts of the project, it could be concluded that both raw material properties and process parameters have an influence on pellets quality


Storage; pellets quality; pellets durability; wood fuel pellets; lignin; extractives; heating value

Published in

Rapport - Institutionen för bioenergi
2006, number: 14Publisher: Institutionen för bioenergi

    UKÄ Subject classification

    Renewable Bioenergy Research

    Permanent link to this page (URI)