Mechanical and Combustion Properties of Agglomerates of Wood of Popular Eastern European Species

Abstract

The objective of the reported project was to produce wood agglomerates from popular East European species to determine their strength and combustion properties. Closed-die pellets were produced from sawdust of six types of wood common on the East European market: pine, willow, oak, poplar, birch, and beech. The properties of pellets, determined by the type of wood, were influenced by the compaction pressure and the moisture content of the sawdust. The highest average pellet density was obtained for oak sawdust, while the lowest density was obtained for poplar pellets. Expansion of pellets after removing from the die was found to be dependent on the wood species, and as expected, on compaction pressure. The pellet expansion increased after 2 h of conditioning in the laboratory and with an increase in moisture content. The highest and the smallest strength were obtained for oak pellets and for birch sawdust, respectively. The strength of the pellets increased by more than 100% with an increase in the compaction pressure from 60 MPa to 120 MPa. The average strength decreased by 65% with increasing moisture content. For all tested materials, drop resistance remained at a high level, acceptable in industrial practice. The highest calorific value of 18.97 MJ/kg was obtained for pine pellets. The highest ash value of 1.52% was obtained for willow pellets and the lowest value of 0.32% for pine pellets.

Pellet Production from Pruning and Alternative Forest Biomass: A Review of the Most Recent Research Findings

“…In contrast, in another study, Quercus robur L. did not achieve the quality standard for the heating value, bulk density, and mechanical durability as a consequence of low lignin content when compared to coniferous oak wood [ 64 ]. Results for beech pellets are very similar to those reported for oak ones, and different studies highlighted satisfactory results [ 50 , 63 , 65 ], even if Stolarski et al highlighted excessively low heating values, bulk density, and mechanical durability [ 64 ]. Pellets produced from poplar and birch showed generally high ash content, making them suitable only for industrial applications [ 64 , 66 ].…”

“…Regarding European oak species, pellets produced from residues from urban green area management of Quercus ilex L. reached quality standard A2 for the heating value and also the minimal requirement for bulk density [ 62 ]. Quercus robur L. pellets showed satisfactory heating values and ash content when pelletizing feedstock with low initial moisture content [ 63 ]. In contrast, in another study, Quercus robur L. did not achieve the quality standard for the heating value, bulk density, and mechanical durability as a consequence of low lignin content when compared to coniferous oak wood [ 64 ].…”

DEM modeling of wood sawdust compaction and breakage strength of pellets determined in diametral compression test

“…0.5 g samples of sawdust without any additives were compacted up to a pressure of 120 MPa using a universal testing machine (Instron 7782, High Wycombe, UK). The downward speed of the piston was 0.033 mm s −1 (Molenda et al, 2021).…”

“…These materials have a low bulk density. Therefore, densification is commonly applied to reduce the costs of storage and transport (Molenda et al, 2021). Biomaterials are densified into briquettes, pellets, or cubes depending on the type of material and intended use.…”

Breakage Strength of Wood Sawdust Pellets: Measurements and Modelling

“…Samples of sawdust (0.5 g) were compacted in a steel cylindrical mould with a diameter of 10 mm and height of 25 mm up to a pressure of 60 or 120 MPa using a material testing machine (Instron 7782, High Wycombe, UK) with a piston moved at 0.033 mm s −1 . To remove the pellet, the base of the mould was removed and the pellet was pressed out [42]. Twelve combinations of pellets were prepared utilising three types of wood, two levels of moisture content, and two levels of compaction pressure.…”