Breakage behavior of biomass pellets: an experimental and numerical study

Abstract

The presence and generation of fines and dust in the bulk of biomass pellets have inflicted several problems in the supply chain during transportation and storage, and the breakage behavior of pellets has been scarcely studied so far. Fines and dust are the consequences of impact and abrasive forces through the whole supply chain; however, the breakage happens at the particle level. Therefore, to study the fines generation, first, the breakage behavior of individual pellets should be understood, and then, the behavior of the bulk materials in operational conditions can be investigated. This paper aims to investigate the breakage behavior of individual pellets under experimental compression tests and to introduce a calibrated numerical model using discrete element method (DEM) in order to pave the way for further studies on pellet breakage. For that purpose, seven different types of biomass pellets were studied experimentally, and then, a calibrated model was introduced via the Timoshenko-Ehrenfest beam theory using DEM. Results show that the model could reasonably predict the breakage behavior of pellets under uniaxial and diametrical compressions. The findings could help to develop a new design of the equipment for transportation and handling of biomass pellets with the aim to reduce the amount of generating fines and dust.

Breakage Strength of Wood Sawdust Pellets: Measurements and Modelling

“…The range of the determined values of σ f is consistent with the findings of other researchers for pellets produced from untreated wood materials [4,6,22]. The range of the deformation at failure, ∆L f /D, found in the present study (0.56-0.82) is very similar to that obtained by Gilvari et al [40] in the diametral compression tests of biomass pellets (0.05-0.07).…”

“…We set the coefficients of particle-particle friction, µ p-p , and particle-wall friction, µ p-w , to 0.5 and 0.15, respectively, in accordance with similar studies on biomass pellets [40] and pinewood chips [38]. The effect of the rolling friction coefficient m r on the behaviour of pellets was not considered because, in reality, the rolling of elongated dust particles seems to be absent.…”

“…The tensile strength σf increased slightly faster than linearly as the coordination number increased (Figure 11b). However, Gilvari et al [40] found that the tensile strength of pellets increased linearly The diametral compression tests were simulated for the three selected values of the coordination number of the pellets (Figure 11a). The shapes of the stress-deformation relationships changed slightly with the change in CN.…”

“…The DEM extended with the bonded particle model (BPM) considerably broadened the range of applicability of the DEM to model the internal structure and breakage of agglomerates composed of numerous particles [35,36]. The method has been applied to model the bulk behaviour of deformable biomass fibres [34], packing of flexible fibres [37], compaction of wood chips [38], durability [39], and the strength of pellets [40]. Xia et al [41] provided a comprehensive discussion of the challenges of modelling the behaviour of the bulk of complex-shaped particles of wood biomass by using the DEM.…”

Determination of mechanical properties for wood pellets used in DEM simulations

“…Hlosta et al (2020b) developed a DEM model to study the mixing processes in rotary drums in order to improve the homogenization of particles and to avoid segregation problems. Gilvari et al (2020) simulated the breakage of individual pellets subjected to uniaxial and diametrical compression tests in order to study pellet breakage for seven different types of biomass pellets. Schott et al (2016) developed a DEM model to simulate a durability test for pellets, thereby emphasizing that durability tests do not adequately reproduce realistic handling conditions at the industrial scale.…”