INTRODUCTION TO BULK SOLID

INTRODUCTION TO BULK SOLIDCHAPTER 1Properties of Bulk Solid

1.1.3

1.2.1 Aerated bulk density, abdThe particles are separated from each other by a film of air and are not in direct contact with each other. Bulk density after the powder has been aerated.Some of the methods in obtaining the aerated density:

1.2.1.1 Poured bulk density, pbdPowder is pored into a containerHeight of fall is fixedThe powder in the container must not be disturbedMass of powder is determinedVolume of powder is the volume inside the cup.

1.2.1.2 Tap bulk density, tbdBulk density of a powder, which has been compacted by tapping or vibration following a specific procedure.

1.3 Voidage, or porosityThe volume of the voids within the bed. i.e. the volume occupied by air divided by the total (overall) volume of the bed.Void volumes includes the pores within the particles if they are porous.

1.4 Powder Flowability Determination

No flowability test is universally applicable. Thus series of powder flow behaviour must be tested experimentally according to the need of industrial application such as powder streams in industrial storage, transport and processing, in terms of their range of applicability, cost and difficulty of measurement.Since the state of the powder varies for different types of applications, the test chosen has to reflect the state of powder in the actual process.Below are some of the tests commonly required in determining flow behaviour in selected process plant

1.5 Compressibility (from bulk density)Compression tests are mainly used for quality control, product evaluation and to measure the tendency for caking.One of the way to express differences between tap density and aerated density:

1.6 Angle of ReposeDefinition: the angle of the free surface of a pile of powder to the horizontal plane.Whenever a heap of powder is being formed, the angle of inclination of the free surface to the horizontal can take any value up to a maximum.Any attempt to build up a heap with steeper sides results in its collapse.

Depending on the condition under which the pile has been poured and how the angle is measured, different values of angle can be obtained for the same powder.When a mixture of uniformly sized granular particles consisting of components with different angle of repose is poured on a heap, the particles having steeper angle of repose tend to concentrate in the center of the heap.

1.7 Hausner Ratio, HR

The ratio of tbd/ abd is called the Hausner ratio, HR (Grey and Beddow 1968/1979).If the ratio:HR >1.4 : Group C1.25 < HR < 1.4 : Transition ACHR < 1.25 : Group A, B or D

Other available types of test such as:Funnel/discharge estFluidization index, deaeration, permeabilityFloodibility testDispersibilityPick up velocityPseudoviscosity and suspension-flow behaviour index etc.Thank you