Time for new rules
New horizontal paddle vacuum dryer overcomes the peculiar limits of traditional systems

Planex System is a brand-new design of vacuum dryer aimed at wet powders from centrifuges and filter presses. Its innovative method of operation makes it especially suitable for active pharmaceutical ingredients (APIs), fine chemicals, and intermediates.
In vacuum drying of powders, thorough mixing is less important than consistently bringing the solid particles to the surface of the granular bed for optimum solvent evaporation. Ribbon or paddle agitators are used in industrial practice to ensure adequate mixing of solid product in cylindrical horizontal dryers. The ribbon impeller offers a high degree of mixing both radially and axially without undue product heating. However, the ribbon impeller is difficult to clean, and the blades can not be easily removed for servicing. On the contrary the paddle type is easier to clean and at the same time guarantees a good and efficient mixing. Continuous surface regeneration is assured by both types. However, the paddle appears to be more suitable, as pharmaceutical and chemical-pharmaceutical applications demand frequent equipment cleaning. The energy consumption of the two agitators is comparable, even though dependent on the number of blades and paddles used. In view of the above and considering the advantages of a simple construction, easy maintenance and quick cleaning, Italvacuum opted for the paddle configuration for its new vacuum dryer.

New design for a double rotation ensuring continuous surface renewal

Planex System consists of a fixed cylindrical chamber containing an eccentric agitator with two independent types of movement: It rotates on its own axis, and also tangentially to the chamber wall. These axial and planetary movements of the agitator can each be clockwise or counterclockwise, with independent speed control through inverter drives. The double rotation ensures optimal mixing of the product, continuously renewing the surface of the mass exposed to evaporation, and covering the entire volume of the vessel. This facilitates the release of sovent vapours, and significantly reduces drying times compared to conventional equipment.

The peculiar configuration of the agitator, which has a much smaller diameter than that of the drying chamber, and the double rotation not only provide excellent mixing but also limit the mechanical and thermal stress, preventing local overheating due to friction. This enables Planex System to treat delicate and temperature-sensitive products without degrading them.

In fact, an independent study by the Politecnico di Torino shows that the mechanical and thermal stress on the product is about one-third of that in a traditional dryer with a concentric agitator. Local overheating caused by friction is therefore correspondingly less. The low power input also provides significant energy savings compared to traditional dryers. Furthermore the reduced gap between the agitator profile and the wall of the drying chamber avoids deposition of the product and makes the unloading operation extremely easy and effective, being also foreseen a specific program automatically managed.

For the parts in contact with the product Planex System is built in stainless steel AISI 316L 1.4404, but on request it is available in any other weldable metal (for instance Alloy C-22 2.4602 and AISI 904L 1.4539).

The wall of the drying chamber, the back cover, the shaft of the agitator and the front door are heated through diathermic liquid circulation in order to avoid cold areas which could cause solvent condensation or product aggregation. All the internal surfaces of the drying vessel are mirror polished or electropolished in order to optimise the endurance against corrosion, reduce the adherence and the friction on the product, increasing the flow behaviour of the powders and simplifying the cleaning operations.

The shaft of the agitator is complete with a double mechanical seal system, studied to guarantee the perfect vacuum tightness and the absolute purity of the dried batch, avoiding any risk of contamination of the product. The mechanical seal may be of conventional type with wet flushing or dry running.

Easiness of cleaning and inspection

Planex System dryers are constructed to cGMP standards and are FDA approved. A built-in CIP system allows thorough cleaning of all parts in contact with the product, while the large front port makes inspection simple and practical. Swab testing is also easy, thanks to the eccentric agitator which is easy to dismantle, unlike the fixed paddles of a traditional dryer.

On the outside, sealed cladding to cGMP standards covers all insulation, wiring and hydraulic piping. External cleaning is especially easy and effective because there is no support frame within the cleanroom; instead, the drying chamber is flanged to the wall and supported from the other side.

As for the other manufactured dryers, beside the Planex System, Italvacuum provides also all the necessary fittings that complete the plant and that are suitably sized in order to satisfy every process requirement:

heating and cooling group for the system thermoregulation;

condensation vacuum group with tank for the recovery of extracted solvents;

safety external filtering unit;

high vacuum group (Italvacuum Saurus939 pump);

control panel with PLC for the management of operative parameters of the drying process, provided with software which could be certified according to title CFR 21 – Part 11, and able to ensure reproducibility of the dried batch and connectable to centralized supervision systems.

Planex System dryers are manufactured in volumes of 300–4,400 l. The loading capacity is 15–80 percent of the vessel volume, depending on the material being dried. Both small and big batches can be treated, covering all the requirements of the chemical and pharmaceutical industries. The ability to work at extremely high final vacuum (below 0.01 mbar) ensures very low final moisture values. Last not least the new vacuum dryer is absolutely safe for the personnel, the environment and the product, being designed and manufactured in compliance with the Atex rules.