Process and an apparatus for agglomeration of a powdery material

A process for agglomerating a powdery material to obtain spherical granules of a desired narrow granule size distribution with a low intragranular porosity in a high speed mixer having an internal coating which substantially prevents the adhesion thereto of the powdery materials to be agglomerated and the auxiliary substances required for the agglomeration comprising the following steps:

• (i) introducing into the high speed mixer a powder to be agglomerated and, in a first phase, mechanical agitating the power at such a low level that no considerable agglomeration or compaction of the powder takes place and no substantial increase in temperature of the powder occurs,
• (ii) distributing in the first phase a liquid uniformly on the powder by atomization of the liquid with an atomizer wheel axially positioned in the mixer, the liquid being a solution of a binder or a solvent for a binder present in the powder, and
• (iii) adjusting the quantity of liquid to be atomized on the powder to be larger than the quantity sufficient to saturate the powder after compaction, but smaller than the amount required to saturate the powder prior to compaction,
• (iv) effecting compacting in a subsequent phase by using a substantially stronger mechanical agitation than that practiced in the first phase and at an increased temperature, and
• (v) simultaneously ensuring an evaporation of the applied liquid or components thereof by using drying gas or vacuum in unison with the decreasing liquid binding capacity of the powder during compaction, thereby completely preventing a higher liquid content in the powder than the one corresponding to saturation.