Pelletering av tallspån : grundläggande studier

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Wood pellets are an upgraded product of residuals from several wood processing industries, for example saw mills and pulp industries. The pellets are produced by pressing the milled and dried sawdust to cylindrical units with a higher density than the initial raw material. Pellets have great benefits compared to the raw material: high energy per volume, good transport and storage properties and homogeneity. Several parameters collaborate in the whole process, which makes it complex. Wood is a heterogeneous material, chemically and structurally dependent on wood parts, habitat and storage procedures. The industrial production of pellets is restricted by accurate control of certain parameters that lead to difficulties when optimising the process. The purpose of this study was to produce pellets from a selected raw material (pine sawdust) using well known and documented conditions. The characteristics of the pellets were then evaluated from the chosen parameters; type of sawdust, moisture content, compaction pressure and temperature. During a limited variation of process and raw material parameters pellets were produced in a laboratory scaled press. Density, compression strength and absorption of moisture were evaluated. Absorption of moisture was shown to be the most important parameter in the process, and many of the results are in agreement with earlier studies on densification of biomass. During the stu...