Highly efficient contact vacuum drying for high product quality in the pharmaceutical industry

The manufacturing of active pharmaceutical ingredients and intermediates require reliable and gentle treatment during solid-liquid separation with succeeding drying of the wet cake. Highly efficient contact vacuum dryers ensure effective drying performance and high operational reliability with low product degradation due to thermal and mechanical influences.

Gentle drying of active pharmaceutical ingredients is of particular importance. Because fast rotating agitators or agitators causing high shear forces lead to unwanted particle distribution as well as product compression with the result of granulation in the worst case. These granules require the use of mills, sieves or even choppers which additionally are further mechanical impact to the usually crystalline active ingredient. This should be avoided.

To prevent possible changes or damage of the crystal structure of the product or damage due to overheating (burning or melting), high shear forces, local compaction or agitator-related overheating of the product should be avoided. Therefore, slow rotating, shear force reducing agitators are the first choice for homogeneous batches. Both horizontal and vertical dryers are used in the industry.

Horizontal dryers can process large volume batches and require smaller room heights. Vertical dryers can be very well integrated into processes using gravitation in manufacturing stream. In example, on the top floor are the reactors, followed by agitated nutsche filter or centrifuges floor, followed by the dryer floor, followed by further dry product handling.

Gentle product processing

In order to comply with highest requirements, especially of pharmaceutical industry, COMBER developed its dryer Pharmadry, Turbodry and Condry series, which all process with relatively slow rotating agitators.

At the same time, they ensure a sufficient product movement in order to avoid any moisture nests. Furthermore, teethed agitators reduce shear force and product compression to a minimum. Another advantage of slow rotating agitators is the low dust generation during the drying process. Comparative small dust filter sizes can be used.

Sophisticated functionality

Within the dryer portfolio the COMBER Turbodry is the most effective due to two design details; on the one hand the vertical, cylindric vessel of Turbodry has a pan-like and flat dryer bottom on which the wet cake rests with a uniform layer thickness. Exact this product wetted area is fully heated. On the other hand, the heated agitator moves vertically within this to-be-dried wet cake. The shear force of the agitator always affects only the height of the agitator in the wet cake, and the slow rotation allows the heat transfer from the heated surfaces to the product very effectively.

In combination with the most sufficient vacuum a highest efficient contact vacuum drying takes place. The dry product discharge of the Turbodry runs similar to filter dryer. The product is discharged through a hydraulically operated side discharge valve. The solid’s discharge valve is a metal to metal seal design with sealing surfaces arranged outside the product flow path. This assures proper sealing even after multiple operations during a batched discharge.

Unlike the discharge of COMBER Condry with conical bottom. Here an almost complete discharge of free-flowing product can be ensured due to central discharge valve. The Condry contact vacuum dryer has a heated, teethed and slow rotating double-helical agitator and guarantees, like the Turbodry an effective and gentle product handling. The inclination of the agitator is dependent of the diameter. Higher inclination at the discharge compares to lower inclination at largest diameter. This measure of adapted inclination does reduce remaining heel after discharge. The installation height of Condry is relatively low since Comber balanced the angle of conical bottom (45°) with a good compromise between excellent discharge, decent mixing and machine height.

Reliable and easy cleaning

In the processing of API und their intermediates a cGMP compliant design matters. A proven cleanability and guarantee of no cross-contamination of process equipment is important. Especially with respect to product quality of multi-purpose units and fast batch changes. For that reason, all COMBER dryers are outstanding in cleanability. CIP nozzles are positioned in vessel, dust filter and discharge device for cleaning. The CIP nozzles allow to cover and reach all product wetted surfaces of the inner of the dryer.

The prove of efficiency of build-in CIP-system is shown usually during Riboflavin testing. Often dryers are flooded with solvents before CIP procedure; in which the solvent is heated and the vessel “boiled out”. Alternatively, the reflow method comes to use wherein condensing vapor remaining impurities dissolve. If necessary, all dryers can be steam sterilisable. Additional temperature sensors enable the monitoring of sterilization of the vessel. Consequently, COMBER dryers are particularly suitable for manufacturing active pharmaceutical ingredients where always a high operational reliability, fulfilment of cGMP-compliant production, effective drying time and a high product quality are required.