Roller Compactor: "In dry cloths" - Publication in the P&A 1-19

Wet vs. Dry Granulation

In granulation, a distinction is made between wet and dry granulation. In Wet Granulation, primary dry powder particles are mixed with an aqueous or alcoholic granulation liquid and compacted. In Dry Granulation, on the other hand, the agglomerates are produced solely by mechanical pressure. In contrast to Wet Granulation, this is a continuous process that does not require any energy-intensive drying processes.

This saves high investments in equipment and production facilities. In addition, there is no need to extract, store and dispose of solvents. All of these factors are reflected in lower costs per batch.
High material throughput

Dry Granulators guarantee a compaction process with a high material throughput of up to 400 kg/h. Different products and batch sizes can be produced with a single system. In addition to their size and the surface finish of their press rollers, Dry Granulators differ primarily in their roller arrangement: there are systems with horizontal, vertical and inclined rollers.

The plant manufacturer L.B. Bohle uses horizontally arranged rollers for compacting. This arrangement has the advantage that the screws are better vented and the flakes are discharged over a short distance. The space between the rollers is divided into three zones. The particles are pre-compacted in the sliding zone. In the compaction zone, the main compaction of the particles is brought about by deformation or particle breakage (depending on the material). The material discharge is the third zone.

Another distinguishing feature is whether the gap is variably adjustable or not. In Dry Granulators with variable gap spacing, continuous measurements ensure that there is always a parallel gap between the rollers. In addition, the screw conveyor speed and the gap adjustment are linked so that when the gap opens, less material is transported into the gap by the screw conveyor and the gap closes again as a result. Thanks to this automatic control, flakes of a defined thickness and porosity are produced across the entire width of the roller.

Electromechanical drive

In its BRC series of Dry Granulators, L.B. Bohle combines high product capacity with minimal material loss. In contrast to comparable systems on the market, the force is generated purely electromechanically, which ensures consistent flake properties. The typical disadvantages of hydraulic controls - such as ageing of the oil and control valves, temperature fluctuations or contamination of the oil - are also avoided.

In addition, the BRC systems use force measurement sensors that are located within the force adjustment and therefore measure the pressing force directly. The measurement results are therefore more accurate than in hydraulic systems, where the values are usually calculated.

Thanks to an innovative method of controlling the compacting force and the flake thickness, the pelletising systems in the BRC series produce uniform compaction of the material over a production range of less than one to 400 kg/h. The sophisticated system design contributes to improved handling and shortens assembly times.

The hygienic design and the washing nozzles already integrated as standard in the standard version guarantee an effective WIP process (Washing in Place), in which the processed product is removed without leaving any residue. With their GMP-compliant design and the option of PAT tool implementation, the BRC systems also fulfil all the requirements of the quality-by-design concept.

Gentle shredding

In addition to the compacting force, the size reduction step is another criterion for the final Particle Size of the granulate. Thanks to a conical BTS turbo screen mill from L.B. Bohle and various screen inserts, the flakes are crushed into pellets very gently in the BRC pelletising systems - even with high material throughputs. The systems can be converted to an alternative Rotation Sieve within a few minutes and thus flexibly adapted to the respective process and flake requirements.

L.B. Bohle has already installed numerous BRC compactors in various batch and continuous production scenarios - as stand-alone systems, as wall-mounted installations, as applications on platforms or across several floors and as customised containment applications. For containment applications in the pharmaceutical and food industries, L.B. Bohle has a containment version of the BRC 100 in its programme.

This system is designed for OEB level 5 (Occupational Exposure Banding), which means that even highly toxic substances can be processed safely. The isolator unit with negative pressure monitoring has been integrated into the compacting unit and is easily accessible for the user at all times. The negative pressure monitoring system forms a second barrier in case the seals fail or the glove ports tear.

Customised containment applications

In the fully integrated containment solution of the BRC 100, L.B. Bohle offers numerous realisation options for interfaces. For example, the system includes a Lifting Columns and containment flaps for filling the product or transferring the granulate to a receiving container. The removal of flakes is carried out in a user-friendly and safe manner via a glove access with safety query. Product samples can be taken at any time via two containment ports: One containment port below the compacting chamber is used to remove flake samples, the second port below the sieve unit is intended for checking granulates.

Further information on Dry Granulation