Changing on the fly
The new Pink rotary dryer is a masterpiece of engineering and attention to detail

The new Pink rotary dryer is a masterpiece of engineering and attention to detail. Pink, which is based in Wertheim (Germany), specializes in vacuum drying technology. The patent-pending rotary drying system gives Pink a clear competitive edge. The dryer can be wall mounted or free-standing, and it is designed for contamination-free handling of highly active substances.

Drying is one of the technologies in the pharmaceutical and food industry which appear to be relatively mature. That, at any rate, is the general consensus. The German manufacturer Pink, which specializes in vacuum drying technology, has shown that this standard technology offers further potential for improvement. The family-managed company has amassed a wealth of drying and process technology expertise over the past 20 years. Vacuum tray dryers made in Wertheim have a proven track record in the chemical, pharmaceutical, cosmetics, process, electrical and food industries. Besides the patented VSD vacuum tray dryer, Pink is also manufacturing isolators in combination with the patented vacuum tray dryer to address a high-growth market segment, namely solutions for handling highly-active pharmaceutical ingredients in containment systems.

Expanding the portfolio
Up until now, the Pink product line has not included dynamic drying systems, but this will change with the introduction of the new RTSD rotary dryer. “Dynamic drying is the only realistic solution for drying large product volumes without contamination, and that is the reason why we are actively developing these systems,” explained Andrea Pink. The popular vacuum dual-cone and tumbler dryers are based on proven, mature technology, and they offer quick, dependable drying of granulate and powder. However, they also have significant disadvantages. The drum has two rotating shafts which are seated in a box-type stand. This makes handling more complex, and it precludes the possibility of wall mounting. The heating shaft supplies heating medium to the drum. The drive journal contains a fixed, removable vent pipe with temperature and/or pressure sensors. The pipe is used to extract vaporized solvent. Media supply pipes have to be routed through the vent pipe. This reduces the cross-sectional area of the pipe and increases the risk of blockage. Vent pipes are susceptible to corrosion, and they have to be well sealed at both the product and atmosphere ends. There is a “dirt trap” between the drive journal and the vent pipe, which creates a cross-contamination hazard and introduces an element of risk into the production process. After carefully analyzing the dirt trap problem on dual-cone and tumbler dryers, Pink developed the RTSD which retains the advantages of dynamic drying but eliminates the problems that are associated with that technology.
Only a 3D CAD model of the rotary dryer was available at last year’s TechnoPharm. Bernd Dreisbach, who is the man behind the system, was only able to present sketches at the time. However, RTSD has now taken shape, and was presented to a wider group of professionals for the first time at Achema. The first system was developed in collaboration with a fine chemicals producer, and installation at the customer site is currently underway.
Floating drum
On the patent-pending drying system, the overhung drum (dual-cone or tumbler) rotates around a fixed axis, and there is no need for a second support pedestal. The bearing and drive assemblies and the supply lines to the product and heating chambers are enclosed in a stainless steel housing. The drum, which has rounded edges and polished surfaces, is GMP and EHEDG compliant. It is completely insulated and enclosed in a sealed jacket. All seams and internal fixtures have been completely eliminated, and you get the impression that the whole thing has been made from a monolithic block. A built-in CIP feature is included for GMP-compliant cleaning. What really sets these systems apart is the availability of optional dry-running mechanical seals on the seal, bearing and drive unit to insulate the product and vacuum/overpressure in the drum from the atmosphere. It may not look like much on paper, but the self-supporting assembly which houses a number of subassemblies in the pedestal is truly a high-tech solution. All of the main dryer functions pass through this main assembly. Through holes in the stationary axle hold temperature and pressure sensors and supply lines for additives and CIP media. There are a number of deep bores which acts as supply lines for the mechanical seal, hermetically separate the different media and transfer the heating media to the chambers in the rotary distributor. Users will look in vane for a vent pipe. On the RTSD, the exhaust vapor is extracted through a smooth bore in the center of the axle. Flexibility was another design goal. Filling and discharging can be configured to suit the mounting position and product type. Vertical mounting, container docking systems and screw conveyors are only a few examples which illustrate the wide range of possibilities.
Drum sizes range from 125 liters to 1,000 liters, and the user can choose the shape they want (e.g. the cone geometry). An agitator or lump crusher can even be installed. An outstanding feature of the system is the elimination of the second pedestal support which makes the RTSD suitable for wall mounting and thus separation between the auxiliary machinery room and sterile room or between explosion hazard zones and non-hazardous zones. The RTSD is ideal for closed systems which use inert gas or vacuum during filling and discharging to avoid contact with ambient air. There is also a mobile version for filling, discharging or docking to an external power supply unit at different locations.