Mixing System Single-Shaft Conical Mixer for Gentle Mixing Processes

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Slowly rotating vertical mixing systems for powdery goods have been around for a long time. Their area of use was primarily where large quantities of bulk goods had to be blended and the proportional composition of the components was to a large extent similar.

The big advantages of mixing systems with vertically mounted mixing tools are the extremely gentle flow principle with a low input of energy, together with good discharge capabilities. However, it was perceived as a disadvantage that mixers with slowly rotating vertically mounted mixing tools generally require longer mixing times than mixers with horizontally mounted mixing tools.

Also, the attainable mixing qualities were occasionally not those of an ideal uniform distribution. New vertical precision mixers with helical mixing tools were developed from 1975 to 1980 in Paderborn. At that time they were called ‘high-performance mixers’. This thrust mixing system was capable of achieving ideal mixing qualities with a low rotational speed in a particularly short time. Initially these mixers were successfully used for the preparation of compound feed and the addition of molasses to them. Henceforth, vertical helical spiral mixers were available in virtually any size from 1 to 40,000 litres.

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Particularly large mixers of this design with usable volumes of ten and 15 m³ are manufactured in large numbers and used for the preparation of baby foods. One of the advantages of large-batch production is that analysis costs can be saved. Again, however, the principles here are:

• Ideal mixing qualities

• Short mixing times

• Minimum input of energy and retention of the agglomerates obtained from the spray tower

• High-level discharge up to 0.007 % and better

• Usability for varying filling levels from ten to 100 %

• Hygienic apparatus design with regard to dry cleaning and if necessary also wet cleaning

• Compact, space-saving design

The production of baby food in smaller batches and with a shortened mixing time is a trend that has been observed in parallel for some years now. So far, horizontal twin-shaft mixers have mainly been used here. Their paddle-like mixing tools are mounted horizontally and rotate in opposite directions to each other. The mixtures are accelerated upwards in the overlapping area of the mixing tools and flow downwards in the outlying regions. This mixing principle is known as multi-flow fluid mixing. The attainable mixing qualities are good and the mixing time is quite short.

Amixon has now taken up the idea of the extremely short dwell time and has created its own development on the basis of the vertical mixing technology, available as single- and twin-shaft versions. Despite the low rotational speeds of the helical mixing tools, the mixing qualities obtained within just 20 to 60 seconds are described as ideal. Rotationally symmetrical closing elements lower a few centimetres and allow a complete discharge within a few seconds. This makes it possible to homogenise large volumetric flows with small mixers.

What takes place here is a three-dimensional random distribution. It is independent of the filling level, the rotational speed and possibly differing component properties such as particle size, density, cohesion, adhesion or viscosity. If the goods are particularly fragile, or if explosive dust conditions can only be avoided with peripheral speeds of less than 1 m/s, the rotational speed of the mixer can be reduced. The mixing process takes place without loss of quality even with slower rotary movements of the mixing tools.

Absolute allergy-freedom in a multipurpose bulk material processing system can only be ensured with thorough wet cleaning. Amixon performs automatic wet cleaning and drying using the Water Dragon system. If the mixer should be cleaned manually, the particularly large inspection doors offer good access to the cleaning personnel.

Further advantage of the mixing machine: it offers a high standard of hygiene with low personnel engagement, since all details are manufactured joint-free. For this reason, the FDA-certified machine is used in many cases for the production of pharmaceutical goods, dietary supplements, dietetic foodstuffs and in particular for baby food.

Mixing processes and other operating parameters can be tested in the manufacturer’s test centre. Like all other Amixon mixers and dryers, these new developments are manufactured exclusively at the company’s only production facility in Paderborn. The bought-in components such as motors and gearboxes are also manufactured in Germany.

* The author is an editor at PROCESS Worldwide. Contact: ahlam.rais@vogel.com

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