|1. What is a
compaction roller press
|2. How does the
powder stick together when going through a press ?
Roller presses working principle ?
|4. Compaction Roller presses applications|
|5. Compaction Roller presses manufacturers|
Roller presses are used to process bulk solids (powder, granules) in order to perform a dry granulation by compaction. They can typically produce a compacted sheet of material that is later milled but some models have specific rollers whose shape allows to produce some briquettes. This page is focusing on the design of roller presses, the mechanisms behind the agglomeration of the material which goes through a roller compactor, and the different applications of this technology.
Roller presses used for compaction of powders are all using counter-rotating rolls maintained in position by a mechanical or hydraulic system that is typically applying a force to one of the cylinders, called the floating roll.
The material is introduced in between the 2 rollers to be compacted. The compaction can be done in between 2 smooth rollers in which case a film or band / sheet of compacted material is produced, however the rollers can also be made of a specific shape that allows to produce pieces of compacted powder.
Figure 1 : Roller press working principle
If a band of compressed material is produced, it is often milled afterwards in order to recover a granulated product that can be sold or processed further (for example to produce tablets in a tablet press), thus the machine is often called roller press granulator.
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When the powder is going in between the 2 rollers, it is submitted to the pressure of the rolls which leads to a dry agglomeration of the material. This dry granulation is allowed thanks to different mechanisms that, at the particle level, allow to keep the material together :
As for similar compaction processes (like tablet presses), the powder is 1st rearranged, densified, then is broken down and deformed by the pressure. The intimate contact resulting from this compression allows bonding in between particles to be created. After compression, the material usually re-expand a little bit. The graph below is illustrating those differences changes in the powder structure according to the pressure it is exposed during the compression process.
Graph 1 : the mechanisms of
pressure agglomeration with the different stages reached and
impact on the material [Pietsch]
The compression of powder is performed according to the following steps [Pietsch] :
Figure 2 : Force feeding of powder to nip area with a screw feeder
Roller presses range from small machineries for pharmaceuticals
to very heavy systems for chemicals, fertilizers and mining
industries. It is thus important to select the products of a
company having a strong and proven experience that will allow to
deliver reliable, performant and easy to maintain machines. Among
those companies, the company Sahut-Conreur (sahutconreur.com) can