Agglomeration-Granulation

In powder processing, agglomeration is defined as the process of amassing material fines into cohesive units like pellets or granules. Simply put, powder agglomeration means making fine powdery particles stick together to form larger particles that are easier to handle.

Agglomeration is also commonly referred to as particle size enlargement. While powder agglomeration results in particles that look visibly different, chemically speaking, the solid particles are the same as before they were agglomerated. The only difference is that agglomerated particles are held together by binding mechanisms that leave voids between the particles. These voids add porosity to the product, making agglomerated materials more soluble and permeable than loose powders.

Depending on the material to be agglomerated, different powder agglomerating techniques and equipment can be used. Pelletizers, granulators, briquetters, and compactors are all examples of industrial agglomerating equipment for powders.

amixon® engineers a range of industrial mixing machines capable of agglomerating dispersive goods during the mixing process. Particularly suited for powder agglomeration is the RMG continuous granulator, a pin mixer model that operates at high rotational speeds to fling materials towards the walls of the horizontal mixing chamber, thereby creating a ring layer in which powdery particles aggregate into uniform granules.

Agglomeration techniques

There are three basic categories of industrial particle agglomeration techniques: pressure agglomeration, sintering, and tumble-growth agglomeration.

Pressure agglomeration

In pressure agglomeration, powders or other dry particles are mechanically compressed into the desired solid form. The applied force can vary in its intensity, from low-pressure extrusion to high-pressure rollers or punch compacting. Pressure agglomeration is typically a dry process requiring no moisture or binding agents. Some common household products that are manufactured via pressure agglomeration include charcoal briquettes and cat litter.

Sintering

Sintering, also known as frittage, is a thermal agglomeration process during which the atoms within the materials diffuse and form bridges across distinct particles, joining them together. Sintering involves heating products without melting them, and as such is particularly well-suited for materials with very high melting points. For this reason, sintering is often used in powder metallurgy.

Tumble-growth agglomeration

Tumble-growth agglomeration, also known as agitation agglomeration, is the most versatile method of agglomeration that is typically used in creating consumer products. This method uses a high-speed rolling action that causes powdery particles to come together as larger, denser particles.

As the rotary motion of the mixing chamber forces the powders to the edges, the particles move along the same path and gradually build up like a snowball rolling down a hill. Tumble-growth agglomeration is typically a wet process involving added moisture or binding agents.

Granulation, pelletizing, micro-pelletizing, and conditioning are all examples of common tumble-growth agglomeration techniques. Each process differs from the others in terms of the size, shape, distribution, and uniformity of the agglomerated particles produced. The RMG pin mixer from amixon®, for example, can be used as a wet granulator or pelletizer and customized to produce agglomerates with a wide range of diameters.  

Learn more about the applications and benefits of powder agglomeration.