DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 3-4/2018 str. 44     <-- 44 -->        PDF

kreće od 7,12 % kod johe pa sve do 13,63 % kod hrasta. Ovako visok udio kore zahtjeva okoravanje, trupaca jer u proizvodnji peleta kvalitete A1 i A2 udio pepela ne smije biti veći od 1,5 %. Usporedbom sadržaja pepela čistog drva, rezultati pokazuju najviši udio pepela kod drva hrasta, dok je on niži kod johe, topole i graba. Najvišu ogrjevnu vrijednost po jedinici mase (MJ/kg) ima drvo johe, dok najnižu od promatranih vrsta ima grab. Analiza gustoće peleta nakon 15 dana stabilizacije, pokazuje da pri istim režimima prešanja peleti mješavina jasena i hrasta daju bolje rezulate od mješavine graba. Također je vidljivo da sila prešanja značajnije utječe na gustoću peleta od temperature prešanja. Analizom tlačne čvrstoće peleta najbolji rezultati dobiveni su kod peleta mješavine jasena, dok je nešto lošiji rezultat kod hrasta, a najlošiji kod graba. Iz dobivenih rezultata mjerenja razvidno je da na tlačnu čvrstoću najviše utječe temperatura i tlak prešanja. Najbolji rezultati tlačne čvrstoće postignuti kod peleta koji su prešani silom 6,0 kN i pri temperaturi 200 °C, gdje je tlačna čvrstoća iznosila od 17,99 Mpa, pa sve do 26,98 MPa.
LITERATURA
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Summary
The paper deals with some quality characteristic of wood pellets from Turopolje area. The samples of pedunculate oak (Quercus robur L.), European hornbeam (Carpinus betulus L.), narrow-leaved ash (Fraxinus angustifoliaVahl.), European alder (Alnus glutinosa L.) and black poplar (Populus nigra L.) were collected. Collected and debarked samples were crushed by a mill with knives to 2.00 mm granulation. The content of water, ash and calorific value were examined on samples. The ash content was determined separately for the bark and the wood. The ash content in the barks shows a high rate in pedunculate oak which is 13.64 % and hornbeam with 11.91 %, while in other species the ash content in a bark is between 7 and 10 %. The ash content of a debarked wood shows the following values: 0.63 % for the oak, 0.50 % for the ash, 0.46 % for the hornbeam. Values of the ash content in the alder and the poplar were 0.4 %. Results indicate the need for debarking in pellet production in order to obtain the quality of class A1 and A2 pellet. By determining the calorific value the best results were determined in the black poplar sample which is 19.63 MJ/kg, and the lower value was measured in hornbeam sample 18.94 MJ/kg. Furthermore, the mentioned samples were mixed and 3 mixture groups were formed. The share of hard broad-leaved trees of oak, hornbeam and ash in each individual mixture was 60 %,while in the remaining 40 %,alder (20 %) and poplar (20 %) equally participated. Formed material mixtures APA (ash 60 : poplar 20 : alder 20), OPA (oak 60 : poplar 20 : alder 20) and HPA (hornbeam 60 : poplar 20 : alder 20) were pressed into pellets by hydraulic laboratory press in 2 forces