4. Powder Processing

Glossary of Terms in Powder & Bulk Technology

Written by Lyn Bates – edited by mhd on 18. Sep. 2022

blending	The placing together of different materials in a prescribed ratio at a scale of scrutiny that is significant to the application by way of low energy mechanisms, such as by intermingling gravity flow streams or layering onto a moving belt. (See mixing and homogenising).
‘boiling’ fluid bed	A fluid bed where the quantity of the fluidising media agitates the mass by passing through the bed in large bubbles.
calcining	A process of modifying the properties of a powder by subjecting it to a high temperature.
capture zone	The converging region between the rollers of a roll press where the surface friction on the product causes the material to move towards the nip point without slipping on the roller surfaces.
cementation	The binding together of particles by precipitation at their points of contact.
cold pressing	The compaction of a powder carried out at room temperature.
comminution	The reduction of particles size by intensive fracture.
compact	A form prepared by compressing powder in a mould or die.
compact, green	(See green compact).
compact, sintered	A green compact after sintering.
cut	The division point for separating a flow stream in which particles are preferentially directed to each side of the ‘cut’ according to some physical attribute.
dilated bed	A bed of powder that is expanded to a dilate condition by a gas pressure in the voids in excess of ambient. (See settling bed, expanded bed).
dry inertial collectors	A type of dust collector that disengages particles from a gas by virtue of exploiting their physical dynamics.
electrostatic precipitators	A dust collecting system that imparts an electric charge to particles in a dust laden stream and subsequently collects them on plates maintained at a high voltage.
expanded bed	A bed of particulate solids held in a state of dilatation by the upwards passage of a second phase media such that the particle-to-particle contact pressure is reduced from that of a settled bed. (See dilated bed).
fabric filters	A dust collecting system that uses porous fabric as a barrier to collect dust particles.
fluid bed	A suspension of particles suspended in an upward flow of fluid (or downward flow if the particles are less dense than the fluid).The bed may be quiescent or boiling, according to the quantity of the fluidising fluid.
fluidising	The process of injecting a gas underneath a bed of particulate solids , to dilate the material in a rising gas stream such that it behaves like a liquid. See fluid bed.
granulation	The process of combining particles into larger agglomerates (granules).
green compact	A formed compact intended for sintering, or which hardens with time or other treatment.

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