“…Therefore, among powder samples with similar mean sizes, those with larger PSD ranges are likely to have stronger particle to particle cohesion and lower FFC values [51], which could explain the relatively low FFC values obtained for samples 5 and 6 under high consolidation conditions, despite their rounder and less elongated shapes. This result is in good agreement with earlier findings reported for other powdered materials [59,60]. properties under non-consolidated, free-surface conditions.…”
Section: Discussion Of the Effects Of Particle Characteristicssupporting
During the thermochemical valorization of biomass feedstock, the assessment of biomass powder flowability is essential for the design of feeding, storage, and handling systems. Biomass handling in valorization processes require powders to be characterized for both consolidated and static conditions, encountered in storage facilities, or under free-surface dynamic flow conditions, present in feeding systems. This paper evaluated the flow properties of two different sizes of raw, mildly and intensively torrefied poplar powders, using shear tests and the evaluation of avalanching behaviors, in a rotating drum. The size and shape descriptors showed that the particle size distributions and particle morphologies of the six samples were determined by the coupled effects of torrefaction intensity and the sieving stage. According to the shear test results, although flowability trends are stress-dependent, coarse powders have better flow properties than fine powders. A flowability ranking was established, based on the parameters extracted from the flow dynamics inside of a rotating drum, including the tendency to form particle clumps, upper angle of stability, irregularity of avalanches, and the fraction of revolution for avalanches. The relationships among the macroscopic flow parameters, obtained from both characterization techniques and the powder characteristics (particle mean size, shape, and polydispersity) were examined using adjusted correlations. Overall, intense torrefaction appears to improve the flow behaviors of powders, under both free and consolidated flow conditions.
“…Therefore, among powder samples with similar mean sizes, those with larger PSD ranges are likely to have stronger particle to particle cohesion and lower FFC values [51], which could explain the relatively low FFC values obtained for samples 5 and 6 under high consolidation conditions, despite their rounder and less elongated shapes. This result is in good agreement with earlier findings reported for other powdered materials [59,60]. properties under non-consolidated, free-surface conditions.…”
Section: Discussion Of the Effects Of Particle Characteristicssupporting
During the thermochemical valorization of biomass feedstock, the assessment of biomass powder flowability is essential for the design of feeding, storage, and handling systems. Biomass handling in valorization processes require powders to be characterized for both consolidated and static conditions, encountered in storage facilities, or under free-surface dynamic flow conditions, present in feeding systems. This paper evaluated the flow properties of two different sizes of raw, mildly and intensively torrefied poplar powders, using shear tests and the evaluation of avalanching behaviors, in a rotating drum. The size and shape descriptors showed that the particle size distributions and particle morphologies of the six samples were determined by the coupled effects of torrefaction intensity and the sieving stage. According to the shear test results, although flowability trends are stress-dependent, coarse powders have better flow properties than fine powders. A flowability ranking was established, based on the parameters extracted from the flow dynamics inside of a rotating drum, including the tendency to form particle clumps, upper angle of stability, irregularity of avalanches, and the fraction of revolution for avalanches. The relationships among the macroscopic flow parameters, obtained from both characterization techniques and the powder characteristics (particle mean size, shape, and polydispersity) were examined using adjusted correlations. Overall, intense torrefaction appears to improve the flow behaviors of powders, under both free and consolidated flow conditions.
“…Sun (2016) cited that the relationship between FF and cohesion is similar to that of FF and MPS in the case of microcrystalline cellulose. Mallick, Rohilla, Garg, and Setia (2018) also observed a close to perfect linear relationship between FF and cohesion of 25 fine powders. In the case of milled teff, the correlation is very strong but negative.…”
Increasing teff (Eragrostis tef) consumption has been recorded in recent years due to its gluten‐free nature and exceptional nutritional composition. Studies on the particle level that relates to processing and handling of teff flour are limited. The effect of different milling methods (roller mill, pin mill, and hammer mill) on size distribution, shape characteristics, and flowability of teff flour was evaluated. Physical properties (angle of repose, tapped and bulk densities, size distribution, and shape characteristics) and proximate composition were investigated and correlated with flow properties. Flowability was measured in terms of bulk, shear, and dynamic flow properties using the FT4 powder rheometer. Particle size distribution significantly (p < .05) influenced the angle of repose, aeration energy, and wall friction angle while shape characteristics (circularity and aspect ratio) significantly (p < .05) affected the aerated and tapped bulk densities and basic flow energy. Hammer‐milled flour had the highest aerated (548.00 kg/m3) and tapped bulk densities (804.33 kg/m3). Pin‐milled flour had the highest compressibility index (38.46%), Hausner ratio (1.62), angle of repose (71.57°), and wall friction angle (25.92° at 3 kPa) indicating poorer flowability. Stability index and specific energy did not vary significantly (p > .05) among the milled flours. Highest basic flow (1,191.03 mJ) and aerated energies (272.32 mJ) were required to induce flow in hammer‐milled flour due to greater proportion of large particles. Based on the flow function, all flours fall under the “easy flowing” category, but the pin‐milled flour exhibited the poorest flowability.
“…1) [15], indicating a possible intrinsic proportional relationship between these two parameters. A proportionality between the two parameters is also suggested by the observation of nearly perfect linear relationship between experimental f c and C for 25 fine powders [17]. Here, we derive a mathematical relationship between the two parameters to explain this phenomenon.Fig.…”
From an analysis of the geometry of the yield locus and the Mohr's circle for determining unconfined yield strength (fc) in shear cell testing, it has been shown that powder cohesion is proportional to fc, where the proportionality constant is a function of angle of linearized yield locus, (1-sinθ)/(2cosθ). While both parameters are routinely included in shear cell data, only one parameter is needed to characterize flow properties of a new powder.
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