New tableting tool

18th December 2018

The QbCon 1 system combines three processes in one machine
Fig 1 Measured residence time distributions of the granules in the continous dryer at different conveying speeds.
Fig 2 Measured residence time distributions of the granules in the continous dryer at times t=0 min (red), t=75 min (black) and t=150 min (blue)
The QbCon 1 from L.B.Bohle is a fully continuous and integrated system for the production of granules

Tobias Borgers explains how a new tableting tool combines three continuous processes in one system

With its QbCon 1 product, L.B. Bohle presents a means for solids production in the pharmaceutical industry that combines the three processes of continuous raw material dosing (mixing of excipients and active ingredients), With a throughput of 0.5kg/h to 4.0kg/h, the system can be used, for example, for the research and development of new drugs where only very small quantities of unique active ingredients are available.

In comparison to some existing plants on the market QbCon 1 meets the main quality requirements of continuous manufacturing in the pharmaceutical industry with regard to:
•  short residence times of the granules in the dryer with simultaneous narrow residence time distribution (‘plug flow’, with extremely low back-mixing of particles)
•  traceability of the materials used (excipients and active ingredients) in a continuous process
•  uniform, reproducible drying of all granule particles of different sizes
•  long service life of the exhaust air filters, without interruption of the drying process or filter change

Currently, quasi-continuous dryers operating in batches are the main offerings on the market for the pharmaceutical industry. These systems are prone to filter blocking, which leads to frequent process interruptions, cleaning or replacement of the filters.

With the introduction of QbCon 1, a real-continuous dryer with a long uninterrupted process time (>8h, 24/7) is now available.

The USP of the innovative machine lies in the real-continuous dryer. Although there are several semi-continuous or quasi-continuous dryers (with several drying chambers operating in parallel) for granules on the market at the moment, L.B. Bohle believes that none of them meet the high-quality requirements of the industry.

In addition, semi-continuous dryers cannot deliver the promised benefit of reducing waste products that do not meet specifications to the extent of the fully continuous dryer of the QbCon 1. Due to the high volume of material, which stays in different chambers during semi-continuous drying, it is not possible to remove small partial quantities from a continuous stream. In fact, the opposite is true with current dryers on the market. Due to the high degree of mixing, whole or partial batches must be discarded when there is doubt.

With QbCon 1, the moist granules leave the twin-screw granulator and are conveyed directly to the distributor bottom of the continuous dryer where they are dried with hot air and conveyed towards the outlet by mechanical excitation. During this conveying process, the granule particles no longer mix, as they remain very close together.

The conveying of the granules and the air flow are independently adjustable. Drying of the granules can therefore be controlled via the supply air temperature, the supply air volume and the conveying speed.

A new principle of filter cleaning keeps the filter surface for the exhaust air permanently clear. Continuous drying can now be carried out permanently and without interrupting the process.

In all tests conducted, the QbCon 1 solution works without process interruption or disturbance. All critical process parameters of dosing, granulation and drying are always constant throughout the entire test period. A noteworthy benefit is the small amount of granules in the exhaust air filters. This is due to the extremely low fluidisation of the granules in the dryer. During cleaning, the filters are completely free of product residue.

With regard to the moisture content of the dried granules, the new system achieves a constant and reproducible result, which is particularly important for a continuous process. The drying is so effective and efficient that some of the granules showed moisture content that was below that of the raw material. This is particularly relevant for moisture-sensitive products. If the residual moisture is considered too low, it is possible to adapt the process to shorter drying times (= residence times), lower temperatures and air flow rates to achieve higher residual moisture contents.

In addition to residual moisture, a consistent granule size distribution is important for further processing of the granules. The continuous granulation and drying process in the new solution leads to constant granule sizes, which are not changed by the gentle drying process.

The residence time of the granules in the dryer is the time during which the moist granules are exposed to the drying air flow. A constant residence time distribution is therefore decisive for consistent drying results. All results reveal an ideal, very narrow residence time distribution of the measured distributions for a continuous dryer. All granules are conveyed through the dryer at the same speed to achieve uniform drying. Back-mixing of the granules in the dryer is also low.

Tobias Borgers is with LB Bohle



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