The different agglomeration processes

The usual classification of agglomeration processes generally specifies 2 types of processes :

And two types of techniques :

A. Processes using agitation or particle growth

In these processes, adhesion between particles is caused by the addition of liquid binders or water and the probability of collision between these particles at variable concentrations in an agitating device.

Such operating conditions can be obtained in the following equipment :

B. Processes using pressure

Low and medium pressure :

High pressure :

Densification and process limits in pressure agglomeration :

The mechanism of densification taking place during these processes using pressure includes the following steps :

• A rearrangement of particles between them (low pressure phase)
• A quick pressure increase during which the weak particles are broken and the plastic particles are deformed.

Two phenomena can limit the agglomeration process :

• The " spring effect " of compressed particles
• The air volume compressed between the particles.

These two phenomena can cause breakages, weaken the agglomerates or even destroy them.

In most cases, entrapment of air can be avoided if the densification occurs slowly to enable the air contained in the decreasing porosity to escape from the raw material and the agglomeration equipment.
This problem is particularly acute and increased with the smaller sizes of the particles. The problem of "spring effect" can only be solved maintaining the maximum pressure during some time. This is only feasible in hydraulic/piston presses in which briquettes are formed in a pressure chamber.

Roller-press do not offer this solution due to a short compression time, generally lower than 0.5 second. However, they can be built for larger capacities (up to 100 T/h in some applications against a few tonnes per hour for hydraulic presses).