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In order to utilize waste products such as sawdust and chips in the wood industry, pellets are made using compaction pressures in the range of 100 MPa or higher. During the compaction process, the density and the modulus of elasticity of the material rapidly increase. Wood materials generally show non-linear viscoelasticplastic behavior and, therefore, the pressure-deformation relationship is dependent on the loading velocity and on the time during which the material is subjected to constant deformation or load. The energy requirement of pellet production depends on many influencing factors and in such cases the use of dimensionless numbers in the form of similarity equation facilitates the processing of experimental results and the obtained similarity relationship has a more general validity for the users. Various fractions of different wood species were used in these experiments, and the pressure, pellet diameter, temperature were also varied. The proposed similarity equation shows a good correlation with the experimental results.U praksi se često od poljoprivrednih ili drvnih materijala prešanjem usitnjenog materijala pod visokim tlakom proizvode pelete pri čemu je tlak često jednak ili veći od 100 MPa. Tijekom prešanja gustoća peleta rzo raste, a zajedno s njom povećava se i modul elastičnosti. Drvo i od njega proizvedeni peleti ponašaju se viskoelastično, tj. njihova tlačna deformacija ovisi o vremenu odnosno brzini pterećenja. Prijašnja istraživanja prešanja usitnjenoga drvnog ostatka pokazala su da cjelovito drvo ni tijekom prilično male kompresije ne pokazuje obilježja elastičnosti prema Hookeovu zakonu. Na kraju ciklusa opterećenja uvijek se zadrži određeni stupanj deformacije, a postupkom rasterećenja velik je dio deformacije nepovratan. Osim vremenom, odnos naprezanja i deformacije određen je i veličinom naprezanja tako da se ne može govoriti o linearnoj viskoelastičnosti. Na temelju rezultata provedenih istraživanja nastala je jednadžba prema kriteriju bezdimenzionalnosti koja univerzalno (neovisno o vrsti drva) karakterizira promjenu gustoće i pritiska s obzirom na prešanje i temperaturu prešanja usitnjenoga drvnog ostatka i dobivenog peleta različitog promjera. Osim toga, istom se jednadžbom može utvrditi karakteristična energija pri izradi peleta ovisno o pritisku prešanja

Study on Energy Requirement of Wood Chip Compaction