Compaction & Granulation
Transformation of a powdery raw material with poor flowability into low-dust granulate with good flowability.
Compaction
The primary goal of compaction is to increase the density of bulk materials.
In particular, small, fine particles are joined by compression to larger particles. The process may also serve to extract high air fractions should be removed from the bulk materials, so eventually achieve lower volumes.
Compaction using roller compactors is a highly efficient method for compacting bulk materials. In roller compaction, the starting material is compacted via two counter-rotating rollers.
Depending on the plastic deformability of the starting material, endless slugs, but also fine needle agglomerates, are produced by pressing, for example, during the compaction of silicates. The slugs are comminuted into granules of the desired shape in subsequent comminution. This results in bulk materials with higher densities (lower volume) and better flow properties.
Examples for the use of Alexanderwerk roller compactors for compacting (and granulating) are:
Show examples
Compaction and granulation of
battery earth
Compaction and granulation of
catalysts
Compaction and granulation of
Color pigments
Compaction and granulation of
Color pigments
Compaction and granulation of
Color pigments
Compaction and granulation of
Color pigments
Compaction and granulation of
Color pigments
Compaction and granulation of
minerals
Compaction and granulation of
ore
Compaction and granulation of
cellulose
Compaction and granulation of
lignite
Compaction and granulation of
various salts
Compaction and granulation of
fertilizers
Compaction and granulation of
spent nuclear fuel elements (U3O8)
Compaction and granulation for the
enrichment of nuclear fuel elements (UF2)
Compaction and granulation of
airbag powders
etc.
Granulation
Granulation is mainly used in pharmaceutical or similar applications.
During granulation, fine, poorly flowing powders are transformed into larger particles called granulates through the agglomeration of particles. The main aim of granulation in the pharmaceutical industry is to achieve good meterability of bulk material, since the active ingredients (APIs) in their non-granulated state are difficult to compress into tablets in the subsequent process step (tableting).
In principle, two different methods are suitable for the production of granules.
Wet granulation
Wet granulation
Wet granulation refers to the process by which binders in liquid form are added to the powders. The binder, usually on water or alcohol basis, acts as an adhesive binding individual particles to each other via the liquid bridges. Wet granulation also requires a drying process to reduce the moisture in the granules. Both the addition of binders and the drying process can have a negative impact on the quality of the granules.
Dry granulation
Dry granulation
In dry granulation, granules of the desired quality are produced by targeted compacting and subsequent comminuting. In this case, it is not necessary to add binders with subsequent drying.
In principle, there are two basic methods:
Slugging
In slugging, large tablets are pressed from the starting material,
which are then subsequently comminuted using mills. The disadvantage is above all the non-continuous process as well as the uneven pressing of the poorly flowing starting material. This is also reflected in the final granules, as slugged granules are often of an unstable and difficult-to-control quality.
Slugging is no longer regarded as “state-of-the-art” and therefore rarely used.
Roller compaction
Roller compaction generates stable granules by continuously compressing powders between two counter-rotating rollers and has therefore become very important in recent years.
The agglomerates are then comminuted via a downstream comminution unit into granules. All Alexanderwerk fine granulators are hallmarked by particularly conservative comminution.
Furthermore, the compacting process is unique, as the vertically arranged rollers, in conjunction with a special control logic, continuously produce slugs of consistent thickness and density.
This is in particular due to the fact that Alexanderwerk has optimized the process as a whole. The quality of the process already starts at the point where the material is fed in at the hopper. An optimized design ensures a good supply of materials. The integrated stirrer ensures that the material can flow properly towards the worm drives. The patented Combi-Vent-Feeder© increases the throughput capacity and substantially contributes to an even mixing of raw and return material. Thanks to the vertical arrangement of rollers, we are completely independent of gravity. The roller gap control in combination with an ever constant pressure force ensures that slugs are produced at a consistently well compacted quality and in line with the defined dimensions.
The unique control design of Alexanderwerk roller compactors permit the operation of the roller gap with a precision of +/- 0.1 mm. As a result, the slugs have an even thickness and density. In addition, the supply of material is controlled continuously to ensure that no fluctuations can occur in the density or hardness of the slugs while constant pressure force is maintained. Multi-stage comminution guarantees, among other things, that we can offer the most conservative comminution compared to all other competitors.
