Vacuum Dryer Powdering While Drying

Author / Editor: Paolo Santi* / Dr. Jörg Kempf

Rotary vacuum dryer/pulverizer fitted with electric lump–breakers–Italvacuum’s Criox system is a multi–product rotary vacuum dryer/pulverizer that completely removes solvents from wet products leaving a filter or centrifuge. It is a versatile technology that is equally suitable for intermediates, fine chemicals, active pharmaceutical ingredients, sterile materials and injectable products. It safely handles materials that are temperature–sensitive, delicate, with varying degrees of fineness, unstable, photosensitive, or chemically reactive.

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The Criox system is manufactured in capacities from 55 l to 12,000 l. While the maximum load level depends on the product to be processed, there are no constraints on minimum batch size.
The Criox system is manufactured in capacities from 55 l to 12,000 l. While the maximum load level depends on the product to be processed, there are no constraints on minimum batch size.
(Picture: Italvacuum)

Italvacuum, with its 75 years of experience and deep know–how in vacuum process applications, is one of the world’s leading manufacturers of vacuum pumps and vacuum dryers for the chemical, pharmaceutical and cosmetic industries. The company’s Criox system is a multi–purpose dryer that can also be used as an effective fast blender or homogenizer, and also as a granulator, reducing the need for subsequent milling of the product. The system is versatile and cost–effective, since on product changeover it minimizes the times required to re–establish the line, wash, clean and inspect the plant. On many plants this allows production to be shifted rapidly from one campaign to another. Furthermore, the Criox System is safe for workers, the environment and the product. It has been designed and built in compliance with increasingly stringent safety regulations as well as cGMP and Atex standards.

The biconical rotating drying chamber ensures extremely homogeneous mixing and uniform drying. The rotation speed is adjustable, allowing agitation to be controlled from very gentle to moderate. This means that even weakly bound products can be dried without physical or chemical damage.

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A Unique Way to Crush Lumps

As well as drying and mixing, the system breaks up any lumps of product. The result is a dry powders with a controlled final particle size distribution, ready to be screened and packed.

To achieve this the system has a unique feature: two powerful sets of lump–breaking blades driven by electric motors. As well as removing lumps in preparation for packaging, the blades increase the surface area of the product available for evaporation and mixing. This results in short drying times, yet with extremely low final moisture levels that other dryers cannot achieve. It also allows heat–sensitive products to be handled at low temperatures without compromising drying performance.

The electric lump–breakers feature easy control of blade speed, with high torque even at low speeds, and programmable operating cycles.

Construction Details

All parts in contact with the product are made of AISI 316L (1.4404) stainless steel as standard, with other weldable materials such as Hastelloy C-22 (2.4602) and AISI 904L (1.4539) on request. The gentle curves of the drying chamber, with no sharp edges or corners, allow surfaces to be coated with fluoropolymers if required, for maximum resistance to corrosion. Italvacuum has also produced enameled versions in which the steel is protected by a layer of alkaline borosilicate.

The same smooth internal surfaces, combined with the rotation of the drying chamber and the action of the lump–breaker, makes the Criox system easy to clean. Only a few rinses with small quantities of fluid are needed to meet FDA standards for cleanliness, and only a small amount of wastewater needs to be disposed of. The internal CIP spray make product changeover even quicker.

The filter on any vacuum dryer must be able to keep all the powder in the chamber, letting only the solvent vapors pass through, yet with the lowest possible pressure drop, so as to allow the maximum final vacuum. Italvacuum offers several filter systems to meet these requirements, with sintered metal cartridge filters or PTFE filters mounted inside the drying chamber. A nitrogen backflush system stops the filter from blinding.

The lump–breaker blades can easily be disassembled thanks to their small size, and the filter system can be removed from the outside. Internal inspection and swab testing is easily done via an access port or the loading hopper. External cleaning is also easy and effective. Sealed external cladding is available to cover all insulation and electrical, hydraulic and pneumatic lines. This feature also allows partitioning solution for the complete separation of clean room from machine room. Partitioning permits to isolate the drying chamber, leaving all the auxiliary groups in the technical room: in this way powders handling for loading and unloading the product is confined in the clean room, thus eliminating any risk of contamination.

Turnkey Plants

Italvacuum asserts to be the only manufacturer in the world capable of producing all the components needed for the Criox System and other vacuum dryers entirely in-house. These include the Saurus 939 range of vacuum pumps, an external filter for added safety, a condenser unit for solvent recovery, heating and cooling equipment, and a PLC–based control panel. The software, which complies with CFR 21 Part 11, ensures reproducible drying and interfaces with centralized control systems.

For drying trials on customers’ products, Italvacuum has a wide range of pilot installations for semi–industrial and laboratory tests. The pilot plants are designed so that product samples can be taken without breaking the vacuum, and the process parameters can be varied at any time. Each trial concludes with a detailed illustrated report containing all the data needed to ensure successful scale–up to production scale.

* * The author is Marketing Manager at Italvacuum, Borgaro (Turin), Italy.

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