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Hollow sphere mixer for bulk materials: SpherHelics®

amixon® process equipment is known for its vertical spiral mixing tools. The manufacturing programme of amixon GmbH is broadly diversified. amixon® can offer a specific solution for almost any mixing task. The name amixon® is, in a way, synonymous with vertical precision mixers.

Less well known is that amixon® cylinder mixers also carry out the mixing process in an inclined position. Although this rarely occurs, there are occasional process engineering reasons for inclining the rotational axis of the mixer shaft by 20°, 25° or 30°. This can be the case, for example, if the mixing unit helix has to rotate particularly slowly, if a cutting rotor has to operate with low filling degrees or if a static mixing tool should not be used.

The mixing chamber does not have to be cylindrical or conical. Other rotationally symmetrical shapes are also possible. For example, a spiral-shaped mixing tool can rotate around a vertical or inclined axis in the hollow sphere. A spherical mixing room even seems to have an advantage.

The sphere requires the smallest specific surface area for its volume. Taking into account that the gross volume of a hollow sphere mixer has to be dimensioned larger than the gross volume of a cylindrical mixer, the surface area reduction compared to a cylindrical mixing chamber is about 13%. In this respect, the spherical mixing chamber has a marginal advantage over the cylindrical mixing chamber. On the other hand, the production of a sphere is demanding and somewhat more expensive. In addition, there is a risk of slipping when entering a spherical mixing chamber.

amixon® wants to expand its pioneering role in the field of vertical mixers!

The aim of amixon® is to advise customers on all aspects of vertical mixers. A hollow sphere mixer was not part of the amixon GmbH portfolio until now.

Therefore, we have newly developed this universally applicable powder mixer. It serves as an experimental mixer in the pilot plant or can be borrowed for trials.

Whether a hollow sphere mixer can establish itself on the market will be shown in practical trials. The typical criteria are:

  • complete dischargeability
  • Flexibility with regard to different degrees of filling
  • Cleanability
  • ergonomic aspects
  • short set-up times
  • resource-efficient operation
  • Acquisition costs
  • ......

 

When a new development is launched, it has to be free of teething problems.

In view of the potential success of this mixing system, amixon® has already registered the brand name SpherHelics®. It is made up of the English words for sphere and spiral - albeit spelt in a different way. As the name suggests, the typical amixon® mixing helix is located inside the spherical mixing chamber.

[Translate to English:] amixon® Pulvermischer

[Translate to English:] amixon® Pulvermischer: KS: KoneSlid®-Mischer haben im Inneren einen gegenläufig geformten Konus, der als Austragsorgan dient. VM: Vertikale Einwellenmischer haben zylindrische Mischräume. SH: Hohlkugelmischer haben vertikale oder geneigte Mischwellen. HM: Doppelwellenmischer haben zwei Zylinder, die sich gegenseitig durchdringen. AM: Konusmischer haben zylindrisch-konische Mischräume.

Questions addressed to the Managing Director Sales and Process Engineering Matthias Böning:

amixon® offers a wide range of vertical precision mixers already.  What was the specific reason for amixon® to add such a hollow sphere mixer to its existing product portfolio?

 

Answer by M. Böning:

I can only answer your question indirectly: Our company celebrates its 40th anniversary this year. We are underlining this event with the commissioning of our newly built Technical Centre 2,

where we can carry out particularly demanding mixing and thermal processes for our customers.

  • We can build up pressure of up to 25 bar in the mixing chamber during mixing, for example to force gas-solid diffusion processes at high temperatures. The main focus is on material transformations on the surfaces of nanofine powders.
  • One of our new reactors has a ceramic lining. It can be operated at process temperatures of up to 350 °C and different system pressures:  Mixing and reaction processes under vacuum (2 mbar absolute pressure) or overpressure up to (8 bar) for mixing and refining powdery active ingredients. We are able to process bulk materials completely metal-free/iron-free.

 

It would be far too costly to exhibit these heavy and expensive mixers/synthesis reactors at a trade fair. On the other hand, amixon® has almost unique prerequisites for future-oriented developments in the field of engineering and functional ceramics.

On a trade fair stand, you usually have more success if you exhibit a highly visible highlight.

We believe that our new hollow sphere mixer can be a good crystallisation point for first contacts at trade fairs. This is how we want to try to get into conversation with interested visitors.  By the way, the hollow sphere mixer is very interesting as an experimental mixer and study object.

Question: Can customers test the new hollow sphere mixer?

Answer by M. Böning:

Yes, of course. Our exhibit is an experimental mixer with approx. 570 litres gross capacity and 400 litres useful capacity. This allows both our clients and us to gain many new insights. Based on the findings, we will later decide how to further develop this mixing system.

Incidentally, it was no great effort for amixon® to develop this hollow spherical mixer from scratch for all sizes.  As a so-called make-to-order manufacturer, we have to design every mixing unit individually anyway.  We use our tried and tested variant configurator for this.  In addition, we know very well how vertical mixers with mixer spirals mix,  no matter whether vertical or inclined.

 

amixon® only uses tried and tested components in the manufacture of hollow sphere mixers. This applies in particular to:

  • the storage of the mixing device
  • the spiral mixing tool
  • the drive
  • the type and function of the dead space-free closure fitting
  • the design of the Clever-Cut® inspection door with the OmgaSeal® seal
  • the design of cutting rotors and
  • lances for liquid addition
  • Sanitary flanges

In this respect, questions of service life and reliability are answered in the best possible way from the outset.

Question: Is amixon® already able to offer and manufacture different sizes of the hollow sphere mixer today?

Answer by M. Böning:

Yes, we have largely completed the constructive design. Each individual hollow sphere mixer must, after all, be adapted for the respective application, especially with regard to the flow properties and bulk densities. The latter can, for example, range from 0.2 kg/dm³ for fumed silica to 6 kg/dm³ for metal powder.

All sizes frequently used in practice are already available. The graduation of the useful contents in litres is initially: 400, 600, 800, 1000, 1250, 1500, 2000, 2500, 3000, 4000, 5000. Larger hollow sphere mixers can only be transported on the road if they are disassembled.  Therefore, our table of dimensions initially ends at 5 m³ usable capacity.

For approximate dimensions, please refer to our data sheet "SpherHelics® Hollow Sphere Mixer Type SH".

Question: Which topics do you think will be important in the future when customers want to purchase new powder mixers for their mixing plants?

Answer by M. Böning:

First of all, it is vital to identify the importance of the mixing system in the value-added process of the respective company. On this basis, the mixer type, the features of the mixer and the approximate price can be quickly determined.

If the end products should have special unique characteristics (dust-free, flow behaviour, colouring, solubility in water, granulometry, bulk density, etc. ...), it is all the more important to take a closer look at the most suitable mixing system and process. In such cases, amixon® recommends the best possible solution with maximum flexibility.

In my experience, this approach has quickly led to a high utilisation of the new mixing plant. This is not least due to the fact that the new mixing plant releases new impulses for creative product developments. "The self-motivation of employees cannot be overestimated!" For us mixer manufacturers, there is hardly anything better than being told such success stories by the investor.

The Gyraton® mixer is suitable for large bulk material volumes.

The Gyraton® mixer is suitable for large bulk material volumes.

Question: Are there any other new developments by amixon® that will be exhibited at the Powtech show?

Answer by M. Böning:

Yes, for companies that want to homogenize large bulk material volumes (10 to up to 70 m³) at a reasonable price. This is possible with a Gyraton® mixer. The mixer has a cylindrical shape in which a conical helical mixer rotates. This can be operated at very low speeds with the aim of keeping the drive power to a minimum. Although this increases the mixing time, it still produces a technically ideal mixing quality that cannot be further improved in practice. Even sensitive powders maintain their original particle size.

 

Thank you very much, Mr. Böning, for your comments. We wish you lots of success at the next Powtech exhibition.

With this sophisticated product range, amixon GmbH underlines its process and quality leadership in vertical precision mixers.

The proof of the pudding is in the eating

 

Tests should be carried out before making a purchase decision. Trials in the amixon® technical centre are always informative. You can test several test mixers in parallel. This allows you to assess mixing efficiency, variety of applications, residual emptying and cleanability. In view of the long service life of powder mixers (20-30 years), this effort makes sense.

Typical questions could be How often does the mixer need to be completely emptied (cleaning or product change)? Will this be necessary more frequently in the future? Can the mixer empty itself completely? Can the remaining product be sold? Or do the residues have to be disposed of? How long does the emptying process take?  How large are the residues?  How long does dry cleaning take? How long does wet cleaning take? How well can it be automated?

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