By Greg Mehos, Jenike & Johanson and Chris Kozicki, Feeco International |
Agglomeration is the process of converting fine powder particles into larger particles by the introduction of external forces. Agglomeration is often desirable because the process yields a product that has a higher bulk density, contains less dust, and has improved flowability. Figure 1 shows samples of fine potash powder and powder that has been agglomerated.
Figure 1. Fine potash powder is one example of an application that can benefit from particle enlargement
Fine powders often exhibit flow problems in a hopper, bin or silo, such as flow stoppages, erratic flow, flooding and limited discharge rates. Flow stoppages occur when attractive forces between particles, such as Van der Waals forces, valence forces and hydrogen bridges, cause a cohesive arch to develop at the vessel outlet. In some cases, powder may only flow in a narrow channel when a feeder or gate is operated. If the material has enough cohesive strength to become stable as the flow channel empties, flow stoppages will occur when powder along the walls remains stagnant. Erratic flow results when ratholes collapse, causing the powder to arch as it impacts the outlet. (An illustration of arching and ratholing is included in the Online Extras Tab for this…