Fluidization of cohesive powders

Mass flow and variability in screw feeding of biomass powders — Relations to particle and bulk properties

“…Excess material was carefully scraped off before weighing and determining the loose bulk density (kg/m 3 ). For tapped bulk density, a removable extension ring with the same internal diameter as the container was mounted on top of the container, increasing the volume of the cylinder to roughly 190 cm 3 , and the whole volume was filled with powder. The container was then tapped (dropped from a height of 1½ cm using a cam mechanism on a rotary drive) repeatedly until no noticeable volume change could be observed (charcoal ~450, torrefied spruce~700, spruce ~500, RCG ~500 times).…”

“…A Hausner ratio above 1.4 indicates poor flowability and a ratio below 1.25 indicates good flowability [3]. One of the major problems with using the Hausner ratio is that there is no standard saying which loose density to use, and there are several to choose between (aerated, poured, and apparent density).…”

The drying of solids in a modified fluidized bed

“…The Carr's index (I carr = 17.2) value in Table 1, in accordance with Carr (1965), indicates that this powder is classified as free-flowing powder. In respect to the Hausner ratio, in accordance with Geldart et al (1984), the solid had HR = 1.21, indicating group A characteristics and free-flow properties. Solid fluidity was analyzed because the behavior of the powder in handling and processing devices is related to the properties of the particles.…”

“…This analysis was used to determine the fluidity of the dry solid. Carr's index (Carr, 1965) was measured with the equipment, and the Hausner ratio was calculated by the ratio of tapped bulk density to aerated bulk density (Geldart et al, 1984).…”

A kinetic study of plutonium dioxide dissolution in hydrochloric acid using iron (II) as an electron transfer catalyst

“…As with bulk dry-powder mixing, interparticle forces was found to promote aggregation of fine particles (~7 0 pm), prevent their uniform dispersion, and result in channeling and 48 excessive entertainment in the off gas stream. The forces attributed to the cohesion of fine particles included van der Waals forces (Rumpf 1962, Baerns 1966, Chaouki et al 1985, Bowling 1988, Visser 1989, Lam and Newton 1992, Baeyens 1992; electrostatic attraction (Rumpf 1962, Derjaguin et al 1968, Bailey 1984, Briens et al 1992; fluid bridges (Parker andStevens 1959, Rumpf 1962); and a general crystallization or precipitation phenomena (Geldhart et al 1984, Kono 1987). …”