Introduction

GRANULATION is a term used to describe two different types of processes. In one definition, granulation is the intentional agglomeration of fine particles into larger clusters to improve certain powder properties. For example, bulk powders typically have a low bulk density, do not readily flow, are dusty, and have low thermal conductivity. When properly granulated, the same powder pours easily, exhibits a high and uniform bulk density, does not experience dusting losses, and more efficiently transfers thermal energy. For example, in the case of a powder used as a feed material for high speed presses, the granules should typically be greater than 50 /,!m (2 mils), but less than 1000 /'m (40 mils) in diameter, have a spherical shape, and should not be strong enough to retain their identity in the compacted part.

Granulation is also defined as the production of metal particles by agitating molten metal. The most commonly used techniques are spray drying and spray granulation. Another method is water granulation. These three methods are discussed in this article. Other granulation methods include agitation and pressure technique for ceramics (Ref 1).

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