Roller Compactor: “Out of the Rain” - Publication in P&A 1-19

Wet vs. dry granulation

Granulation distinguishes between wet and dry granulation. In wet granulation, primary dry powder particles are blended and compacted with an aqueous or alcoholic granulation fluid. In dry granulation, the agglomerates are, in contrast, produced by mechanical pressure only. In contrast to wet granulation, this is a continuous process that requires no energy-intense drying processes.

This saves high investments in equipment and production space. There also 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 ensure 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. Apart from their size and the surface properties of their pressing rollers, dry granulators are distinguished mostly by the roller arrangement: There are systems with horizontal, vertical, and inclined rollers

System manufacturer L.B. Bohle focuses on horizontally arranged rollers for compaction. This arrangement has the advantage that the screws are better vented, and the scabs are removed quickly. The space between the rollers is divided into three zones. The particles are pre-compressed in the sliding zone. The main compression of the particles is achieved by deformation or particle breakage (depending on the material) in the compression zone. The material discharge represents the third zone.

Another distinguishing feature is whether the gap is variably adjustable or not. In dry granulators with a variable gap, continuous measurements ensure that a parallel gap between the rollers is preserved at all times. Additionally, the screw conveyor speed and the gap adjustment are coupled with each other. When the gap opens, the screw conveyor feeds less material into the gap, and the gap subsequently closes again. These automatic controls produce scabs of defined thickness and porosity across the entire roller width.

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 strictly electromechanically, to guarantee consistent scab properties. This also avoids the typical disadvantages of hydraulic controls, such as aging of the oil and control valves, temperature fluctuations or contamination of the oil.

Force measuring sensors are also used in the BRC systems. They are located within the force adjustment to measure the compression force directly. The measurement results are, therefore, more accurate than those in hydraulic systems where the values are typically calculated.

With an innovative compaction force and scab thickness control method, the BRC series granulation systems compact the material uniformly in a production range from less than one up to 400 kg/h. The sophisticated system design helps improve handling and shorten assembly times.

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

Careful crushing

In addition to the compacting force, the crushing step also is a criterion for the final particle size of the granules. Thanks to a conical BTS Turbo Sieve Mill by L.B. Bohle and various screen inserts, the scabs are crushed very carefully in the BRC granulation systems, even at high material throughputs. The systems can be converted into an alternative rotation sieve and thus flexibly adapted to process and scab requirements within just a few minutes.

L.B. Bohle has already installed many BRC compactors in different manufacturing scenarios of batch and continuous manufacture – as stand-alone systems, as wall installations, as applications on stages or across multiple levels, and as individual containment applications. For containment applications in the pharmaceutical and food industries, L.B. Bohle offers a containment version of the BRC 100.

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

Individual containment applications

In the fully integrated containment solution of the BRC 100, L.B. Bohle offers numerous implementation options for interfaces. The system includes a lifting column and containment flaps for product filling or transferring the granules into a receiving container. Removal of scabs is rendered user-friendly and safe via a glove access with safety prompt. Product samples can be taken at any time via two containment ports: One containment port below the compaction chamber is used for sampling scabs. The second port below the sieve unit is intended for checking granules.