NEWS

Nauta mixer back in feed industry

The Nauta mixer as many people probably still picture it is at least 80 years old. Since acquiring the Nautamix company, Hosokawa Micron has completely modernised the mixer over the years.

The Nauta mixer used to be a familiar sight in animal feed plants, and some factories had a whole row of them side by side so that the molasses meal could ripen before being transported to the pellet machines or cake presses. In those days, the mixers were straightforward conical machines with a single motor at the bottom driving both directions of movement: up and round. The Nauta mixer required high ceilings and entailed a longer mixing time. As a result the machine initially lost out to the horizontal ribbon mixer, which offered a smaller footprint and a shorter mixing time. More and more producers subsequently switched to the paddle mixer, especially as the liquid percentages of formulations continued to increase.

And yet the Nauta never entirely vanished from the scene. In fact, it has become a mixer with a number of clear advantages when used for specific purposes. 'Wants' sometimes turn into 'needs' over time – plus food safety and quality have generally become more important than they used to be. So we thought it was high time to reacquaint ourselves with the Nauta mixer of today.

Mixing screw

The Nauta mixer is a spiral screw that turns in parallel with the conical inner vessel wall, conveying the product upwards as it does so. The product drops back down again under the effect of gravity, effectively churning the product in the vessel. Additionally, the orbital arm of the screw rotates in a circle. Some applications have two screws in order to reduce the mixing time. The actual mixing action is based on the exchange of particles between the mixing screw and the rest of the vessel contents.

Nauta mixer working principle

Nauta mixers are available for volumes ranging from just 2.5 litres to up to 100,000 litres. On top of the domed lid is a single motor driving both movements. This consumes much less power than horizontal mixers because, unlike horizontal mixers, a Nauta mixer does not keep the entire contents in motion. For example, depending on the application, a 60 m³ Nauta mixer requires an installed power capacity of just 55 kW, which is a fraction of what other mixers need.

Changes

Today's Nauta mixer has retained the familiar conical shape, but both the top and the bottom of the machine have been adapted to modern-day (hygiene) demands. The top has become more rounded and the motor is positioned on top of the domed lid, driving the screw in both the vertical and the radial direction. Notably, the screw is no longer mounted on a support at the bottom. Instead, it is now suspended at an angle – just free of the inner wall – without being attached to the base of the cone.

The opening this creates at the bottom of the vessel is sealed by a so-called ISEM ball segment valve. This is a convex seal on an axis that can swing through 90 degrees to open and close: not only a hygienic solution, but also one that takes up less space than the traditional electro-pneumatic valve. The new version of the mixer is topped off by large doors and connections for compressed air used in spray cleaning.

Energy-efficient

So why is the Nauta mixer now starting to attract more attention again? The Nauta mixer is energy-efficient, very gentle on the product, stays nice and clean and if necessary it's much easier to clean than other mixers. This is due to its shape and easy accessibility; the machine mixes logically and very thoroughly. Notably, even when it's only partially filled to less than 15 percent, its mixing performance is still excellent. In view of the current wishes of farmers and other customers, that's a big plus.

After mixing, the premix manufacturers in particular tend to fill the product directly into big bags or sacks. It is commonly accepted that large differences in particle sizes (e.g. in the case of chicken meal) and bulk densities (e.g. 150 kg of minerals versus 50 kg of average material) can cause extensive and rapid separation in mixed products.

Replacing the ribbon mixer and the bunker beneath it with a Nauta mixer will enable you to make a big improvement in terms of separation, especially if you also manage to limit the discharge transport beyond. In other words. it is efficient, clean and ideal for minimising separation.

Vitomix mixer

The Vitomix mixer has arrived on the scene in the food and feed premix sector as a smaller-format mixer with two rapidly rotating screws. At Hosokawa, they know from experience that the feed sector tends to follow close behind food. Examples are one-minute mixing times, possibilities to add up to 30 percent liquids, low energy consumption and easy cleaning. Vitomix is currently available for volumes of up to 10,000 litres, depending on the product. Multiple screws in one machine, open screw blades... we think up all kinds of ideas to be able to provide any type of customer with a suitable solution. And rather than being a reactive process, this is based on the company's own development work.

Vitomix feed mixer

Another benefit of the Vitomix mixer is its continuously low energy consumption. Issues like accuracy, speed, investment and quality are all factors when choosing a mixer. Key features in terms of the 'quality factor' are residue-free emptying, ease of cleaning, lack of chemical hazards, maintenance, mixing speed and good accessibility thanks to the sizeable door in the vessel wall. Potential customers can test their specific demands for this type of mixer at the company's facility in Doetinchem.

Nauta mixer

Although the Nauta mixer is no longer used in standard animal feed plants, the mixer has found a new lease of life among premix manufacturers in particular. The Nauta mixer is gentle on the product, does not generate heat through friction and can be cleaned at lightning speed. Furthermore, this mixer can handle batches of varying sizes to produce – and maintain – homogeneous mixtures. Thanks to the absence of bearings and seals in the mixing zone, there's no risk of contamination by lubricants now that the screw is free-hanging.

In animal feed plants, the machine often took up too much space in terms of its height, plus relatively speaking it had a low capacity. When comparing that height against a horizontal mixer concept, the feed bunker beneath the mixer should also be factored into the equation in many cases. The comparison should be nuanced, especially if the product goes straight from the mixer into bags or storage. We've noticed that the mixing time might be a little longer than is the norm in the animal feed industry, but it is ideal for small batches. If you're looking for a smaller and faster alternative, the Vitomix is a good option. So the Nauta mixer still has a role to play, it's just that its field of application has shifted. Nowadays, the Nauta mixer is primarily used as a mixer for premixes.

History of the Nauta mixer

The Nauta mixer is named after Johannes Ewardus Nauta (1890-1957) who started his career in the early 20th century in an animal feed factory in Leeuwarden. That was his first introduction to mill frames, which were commonly used for grinding at that time. Nauta subsequently set up his own company offering a maintenance service for mill frames, but also selling machines and eventually he even branched out into designing animal feed factories.

In 1923 Nauta opened a factory in Haarlem where he built machines for the animal feed industry. In 1939 he developed a conical mixer with a rotating transport screw that moved upwards along the internal vessel wall: the 'Nauta mixer'. The mixer gained worldwide popularity and the Nautamix company grew into a business employing 150 people, with locations in Haarlem and Assen.

Nauta mixer (1948)

In 1982 the Hosokawa Micron Group acquired a majority share in the company. In 1987 Nautamix was merged with Zelhem-based Machinefabriek Vrieco and Doetinchem-based I.S.E.M., two companies that had likewise been acquired by the Hosokawa Micron Group in the preceding years. And so it came about that the Nauta mixer is now made (and further developed) by Hosokawa Micron in Doetinchem.

Hosokawa

The Hosokawa name reflects the involvement of a large but very engaged overseas owner. The company is specialised in the powder processing industry, with as its core business the engineering, design, supply and servicing of systems, complete plants and machine parks for powder mixing, drying, granulating, milling, classifying and filling as well as combinations of the aforementioned processes. Its main industries are pharmaceuticals, (fine) chemicals, food, cosmetics, plastics, metals and minerals.

Hosokawa Micron's high-tech premises in Doetinchem house advanced test facilities. In Doetinchem, the main focus is on mixing, drying and agglomeration. Elsewhere, such as in Augsburg for example, which is home to Hosokawa Alpine, the primary activity is milling.

SUSTAINABLE PROCESSING SYSTEMS

Hosokawa Micron B.V. is certified according to ISO 14001. Our certification covers all environmental themes of ISO 14001: air, soil, energy, waste, water, noise and hazardous substances. In addition, Hosawa Micron was awarded an EcoVadis Silver Medal for its sustainability achievements. EcoVadis determined that the company was among the top 7% of companies rated by EcoVadis in the special machinery industry.

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