01/31/2005 • Mechanical process technology • Systems and Components

Dryer Report – Initial Pharmaceutical Products

A number of different stages of synthesis are involved in the manufacture of pharmaceutical agents. Whenever the synthesis results in flocculation or crystallisation of the desired product it is subsequently necessary to wash the products with alcohol, acetone and/or with water or with an aqueous solution. The washing process is most often followed by a mechanical drying process, which takes place, as a rule, in centrifuges or pressure suction
filters.

Because it is not possible to achieve the necessary desiccation ratio (TS greater than 99.95 %) with this step alone, a more intensive, thermal drying stage is required. Convection or contact dryers are used here. Contact dryers are most often used if the materials require handling of
a sort that will entail extremely little contamination. Contact dryers
are also preferred if the materials do not adopt unusual consistencies
in the course of the drying. The usual design of contact dryer includes
a temperature-controlled boilerin which a mixing gear rotates at
high or low speed. A distinction is made between contact dryers
whose mixing shaft is oriented horizontally, vertically or inclined.
As an example of the horizontally oriented equipment we might
mention here the classic paddlethrough or ploughshare dryers,
particular versions of which have been produced by various manufacturers.

For decades, this design has been the standard dryer used both in pharmaceutical manufacturing processes and in the chemical industry. In the meantime, new types of mixer-dryers have began to replace the classic paddlethrough dryer; these are dynamically operating vertical single-shaft
mixer-dryers, such as those already successfully introduced to the market
by amixon®-GmbH.

amixon® - Vacuum Mixer-Dryers and Reactors

within a thick-walled, round cylinder with a flat base, passing extremely
close to the walls and floor. The very height equidistance between the mixing gear and the fully heated walls guarantees ideal thermal transfer, reliably avoiding wall adhesions. The special shape of the helical spring creates mixing and flow, without compacting or pressing the materials. It is of particular significance that all the surfaces of the mixing gear are also
temperature-controlled; the shaft of the mixing gear, the shovel-like
arms and the helical spring.

So far, amixon® has replaced 18 horizontal paddle-through dryers
with vertical dryers. These are industrial dryers for pharmaceutical
agents such as penicillin, analgesics, cardiac medications and Xray
contrast media, as well as chemicals such as herbicides, fungicides, adhesive glues and ceramic pigments. The batch sizes vary from 50 litres up to 18,000 litres. In every case, the users of the mixer-dryers have judged the vertical type of construction to be good or very good. Extensive trials at the company's laboratory in Paderborn have included system comparisons through which it has been shown that the amixon® – vacuum mixer-dryers save more than 40 % of the normal drying time required by conventional paddle-through dryers.

The reason for this is that the flow of the material to be dried extends
throughout the entire chamber – thanks to the patented mixing gear there are no dead spaces. Whether the material is a powder, a paste, or is a viscoplastic phase, it can be handled reliably at any time by the amixon® mixing gear, and can beprocessed in the equipment. Crystalline materials, such as are often found as initial pharmaceutical products, represent a special case. Their crystalline structure means that they are not easily
mixed, and that it is difficult to generate a flow in the mixer. On the other hand, the mechanical or thermal input of energy involved in the drying process must not damage the crystalline structures.

The amixon® vacuum mixer-dryer rises to this task magnificently. The
process materials are screwed upwards at the periphery of the container
by the mixing gear, and flow down along the shaft again under the influence of gravity. This kind of mixer, moreover, can be operated with variable circumferential speeds from > 4ms-1 to < 1 ms-1, since this does not affect the flow without dead spaces. A further patented technique provides almost ideal support to the ability to process the materials without damage,
and sets new standards in the gentle treatment of the materials in mixing and drying systems with dynamic installations.

The ability to choose circumferential speeds, when required, of < 1 ms-1 has another crucial advantage for many companies: if dust or solvent
can give rise to a risk of explosion in the equipment as it is started up or shut down under atmospheric conditions, it is possible to lower the circumferential velocity in order to satisfy the need for safety (see here also ATEX 94/2/EG)
.
VMT 3000 for pharmaceutical sterile products used Vacuum mixer-dryer with hygienic inspection door The drive, the bearings and the seals for the mixing gear shaft are all above the mixing chamber. Thermal expansion and mechanical stress do not have any effect on the face seal. Both high excess
pressures and high-quality vacua are sealed with extremely little leakage. This reliably protects the environment of the mixer-dryer from the materials reacting within the equipment, and at the same time lowers operating costs and safeguards the purity of the materials.

Hygiene and Cleaning

amixon® equipment is designed and built in accordance with the most recent EHEDG guidelines, and conforms to GMP and FDA requirements. They can be used in all areas of the pharmaceutical industry.

For apparatus that needs to be operated under sterile conditions (e.g. penicillin manufacture) amixon® has developed techniques and special solutions particularly for this purpose. Vertical mixer with conical base
for very thorough emptying of residues If it is important to have very high
residual emptying rates, the amixon® conical mixers and mixer-dryers are particularly appropriate. Together with the patented "sliding blades", the conical base ensures residual emptying rates of almost 100%. With the
"sliding blades", the mixing gear is tilted to a horizontal position. This improves removal of the product residues. Otherwise, the same requirements related to and governing the technical aspects of the process apply as have already been described for the vertical vacuum mixer-dryers with flat bases
.
In addition to the equipment itself, amixon® offers, as a service, assistance with the qualification of the supplied equipment. All the necessary documentation is drawn up, and qualification of the installation
carried out in co-operation with those who will later operate the plant. This makes it a great deal easier for the pharmaceutical companies to integrate
one of the core items into such an installation, unloading a significant portion of the work.

Laboratory and Trials

The Alloy and Hastelloy drying equipment in the amixon® laboratory are already part of the apparatus manufacturer's standard equipment. This offers a major advantage to all manufacturers and future customers interested in experimental.trials: all products can be tested in their true form; it is not necessary to make use of a dummy product.

amixon® mixerdryers and reactors have hygienically closing openings at the sides, and these make access for inspection and cleaning purposes much
easier. The internally located filters allow valuable building height to be saved, as does the equipment's compact construction. On the basis of the large number of trials that have already been carried out, and of the extremely positive feedback and data available from dryers that are in operation, the design and upscaling of production apparatus is guaranteed, ensuring maximum customer satisfaction. The amixon® team would welcome your visit at any time.



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amixon GmbH

Halberstädter Straße 55
33106 Paderborn

Phone: +49 (0) 5251/ 688888- 0
Fax: +49 (0) 5251/ 688888- 999