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Pelletized Composite Wood Fiber Mixed with Plastic as Advanced Solid Biofuels: Physico-Chemo-Mechanical Analysis

E. Madadian, A. H. Akbarzadeh, V. Orsat, M. Lefsrud
Waste and biomass valorization 2019 v.10 no.3 pp. 721-732
angle of repose, biofuels, bulk density, chemical analysis, composite wood products, feedstocks, gasification, image analysis, mechanical properties, modulus of elasticity, pellets, plastics, wastes, water content, wood fibers, wood residues
The purpose of this study was to evaluate the physico-chemo-mechanical performance of composite wood residue pellets blended with plastic wastes as potential feedstocks for producing advanced biofuels through gasification technology. The composite pellets of wood fiber and plastics were compressed longitudinally and laterally using a universal testing machine to evaluate their mechanical properties. The compression test results showed that pellets with larger diameters have higher elastic limits. With respect to the transverse direction, there was no certain relationship between stress–strain values and pellet sizes. The incompatibility in the relation between the increase of yield stress and diameter was attributed to the unknown type of plastics used in the composite plastic wood pellets. As a consequence, we predicted the type of plastics used in the composites using the rule of mixture considering the Young’s modulus of composites and the wood fiber as well as the volume fractions of the constituents. We also measured the angle of repose of the composite wood pellets, which ranged between 25° for the largest samples to 41° for the smallest pellets implying that the pellets with smaller diameters have lower chance of slumping in the feeding drum during gasification. It was also shown that the angle of repose would increase with the moisture content in all the composite pellets. Larger pellet size with higher bulk density demonstrated smaller angle of repose. The chemical analysis was presented in conjunction with microscopic imaging to understand the microstructural interaction between plastic and wood fibers in the composite pellets.