Powders, Agglomerates, Granules & Pellets

Combining Science and Engineering in Particulates Processing

Particulates technology is a science of growing importance. The functional properties of dried products are being more precisely specified by industry to meet the quality and environmental demands of a competitive world.

Plants for producing particulate materials like powders, agglomerates, granules and pellets have to be designed individually and engineered accordingly. Only in this way can particulates of desired properties, i.e. particle shapes and structure, moisture content, bulk density etc. be produced successfully in batch and continuous processing.

This involves Particulates Engineering, and here the Niro Group has special expertise.

With the availability of a range of processing possibilities, Niro selects the plant type, its layout and operation best able to meet a given specification irrespective of the type of particulate involved.

Powders

Powders consist of primary particles, existing individually or with some loose agglomeration through adhesive forces.
Agglomerates
Agglomerates consist of large particles formed by the joining or binding together of primary particles whose original identity can still be visible in the final agglomerate form.
Granules
Granules consist of particles formed by the progressive enlargement of primary particles until their original identity is no longer visible.
Pellets
Pellets consist of spherical particulates produced during a precise forming and mechanical handling operation.

Mechanisms

Pendular

Funicular

Capillary

Monosized

Agglomeration, granulation and pelletizing processes involve the wetting and mechanical handling of particulates. An open and porous agglomerate structure changes to a more closed and grain-like granule structure as the degree of wetting and mixing is increased. Particulates engineering involves the control of moisture and energy input to achieve a desired change in structural and other properties.

By improving:

• free floability
• ease of handling
• visual appearance
• ease of compaction

Energy Input KW/kg Liquid addition kg/kg. Model- Granulation Growth Regime

By adjusting:

• bulk density
• solubility rate
• shape and size distribution

By reducing:

• fines (dust) content

Liquid bridges between the contact points of primary particles feature as the most important binding mechanism in agglomeration and granulation.

In order to carefully control the granule growth, the solids have to be kept in constant motion. This can be obtained either by mechanical fluidization where the process chamber is rotating or equipped with stirring devices, or by fluidization in air.

Granule growth takes place above a certain minimum binder/solution addition rate as fixed by the fluidizing conditions, particle size and distribution. Rapid coalescence between particles and wetting droplets forms nuclei which grow by pendular bridging, forming agglomerates. The above sequence of bridging mechanisms continues until all particles are bound on the surface of the resulting grain or granulate.

		Powders Spray drying Vortex fluidizer drying Flash drying Fluid bed drying Microwave vacuum drying Spray Cooling (congealing)				Agglomerates Fluid bed agglomeration Spray dryer agglomeration Rewet Agglomeration
		Granules Spray dryer granulation High shear granulation (Continuous) Fluid bed granulation High shear granulation (Batch)				Pellets Layering Wet granulation pelletizing Melt granulation pelletizing Extrusion and spheronizing
		Other Processes Particulates - Coating Fibrous Materials - Steam drying