Fig. VN mixer

Fig. VN mixer


The Vrieco Nauta Mixer is a widely used powder mixer with over twenty thousand units delivered worldwide. It consists of a conical body with a mixing screw attached to a rotating arm. The Vrieco Nauta Mixer has several favorable attributes such as mixing swiftly with low energy consumption, minimal damage to the powder particles, ease of discharge with low amount of residue, and ease of cleaning making use for multiple products easier. Because of these characteristics, the Vrieco Nauta Mixer is used for the mixing of powders, mixing of powders with liquids, and also as heater, dryer, reactor and cooler. With a wide range of models and options, the Vrieco Nauta Mixer can meet a wide variety of requirements and applications.
(NAUTA & "NAUTA MIXER" is a registered trademark of HOSOKAWA MICRON CORPORATION in Japan)

VN Type summary

The new standard model developed with ease of use and cleaning as a primary requirement, with cost reduction using standardized parts.

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The Vrieco Nauta Mixer consists of a conical vessel with drive(s) at the top. The drive rotates a swing arm that rotates around the centerline of the mixer. At the tip of the swing arm is a mixing screw that rotates. The rotation of the swing arm moves the rotating mixing screw along the inner surface of the conical vessel.

Fig.1 Vrieco Nauta mixer

Fig.2 Schematic structure of Vrieco Nauta mixer

Fig.3 Basic principal of mixing by Vrieco Nauta mixer.

Fig.2 shows the mixing model of a Vrieco Nauta Mixer. The rotating mixing screw lifts the material around the screw up while material away from the screw moves down due to gravity. The slow movement of swing arm moves the rotating screw along the inner wall of the vessel eventually moving all of the powder in the mixer. The movement of the powder is very gentle but almost no segregation occurs allowing for efficient and swift mixing to occur. Since all of the powder in the mixer is not moved at the same time, the power requirements are very small.

After 1'50", you can show that how two powders are quickly mixed.


. Swift mixing with minimal energy consumption
Due to the efficient mixing principle, swift mixing is achieved with low energy consumption. For simple mixing of powders, 300 liters can be mixed in 3 to 10 minutes. For 3000 liters, mixing is completed in 15 to 45 minutes.
. Mixing deviation converges quickly with little variation
Generally mixers have a large convergence and divergence of mixing levels depending upon the mixing time with material separating after mixing. In the Vrieco Nauta Mixer, this separation does not occur.
. Minimal damage to particles
The shear force on the particles is very small resulting in minimal damage to the particles.
. Low heat generation
The low energy consumption results in low heat generation. Mixing of materials with a low softening point of 50°C is possible.
. Easy to discharge material with little residue
The conical shape with the discharge port at the bottom makes discharge of material easy with a minimum of residue.
. Large machines possible
With the vessel fixed and with a small screw diameter, the required power consumption is small allowing for design of large machines.
. Low vibration
When operating, the Vrieco Nauta Mixer has almost no vibration allowing for high accuracy weight measurements. Also there is no need to consider vibration for the supporting structure.
. Easy to clean
The Vrieco Nauta Mixer is a simple machine with one or two screws inside a vessel allowing for easy cleaning. This makes changing products easier and maintenance is also simplified.
. No seals within the material bed
By having the drives at the top of the machine, there is no need for seals to be inside the material bed. This prevents seal damage due to wear from powder contact.
. Simplifying processes
A single machine can be used for mixing, drying, reaction, cooling.

Table1 Comparison with other types of mixer

<The Mixing Process>

Mixing is a process where two or more materials are mixed together. There are many methods to express the level of mixing and there are also many evaluation methods. The amount of effort required to measure samples in a statistically relevant way is unrealistic.

The required level of mixing differs between if the mixed material is a raw material, intermediate material or a final product. Another important factor is the unit volume of mixed material used in the product. It is better if the analysis method is based upon the quality control method in use.

For scale-up, the mixing time and energy consumption becomes an issue. The power consumption increases proportional to the weight of the material to be mixed. For materials with a high bulk density or for materials with a big difference between the bulk and tapped densities, care must be taken. Mixing time depends upon the material average circulation time, but factors such as past performance and experience must be taken into account.

Care must be taken handling the mixed product to prevent the mixed particles from segregating. When designing a mixing system, all of these factors must be taken into account.

VN Type features

• Newly designed shaft seals prevent lubricant from leaking into the product.
• Minimized the number of fasteners in the machine interior. Bridge cover is also a box construction greatly increasing clean ability.
• Compact design gearbox and swing arm reducing height
• Sanitary design with safe seals on the drive assembly
• Reduction of gear losses reducing energy consumption
• Many options available

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NAUTA MIXER Vacuum/Pressure type


Other information


There are two basic types of Vrieco Nauta Mixer, one with a cantilevered mixing screw and another with a bottom supportedscrew. There are 2 types of bottom support, a radial locator type and a pin joint type.

Fig.4 Bottom supporting mechanisms

The standard Vrieco Nauta Mixer has one mixing screw, but a variant with 2 mixing screws (D2SX type) or with twin vessels (CX type) is available.



The Intensifier is a high speed-mixing rotor installed in the center shaft. It prevents agglomeration and prevents light materials from segregating on the top of the material bed when mixing materials with large differences in density. It can also be used to increase dispersion effects when adding liquids. The rotating mixing screw continuously brings material to the Intensifier allowing for efficient mixing to occur.

Fig.5 Intensifier

Vacuum sanitary dome cover

Used when the mixer is used in a negative or positive pressure. The drive and arm are also designed for negative or positive pressure. The domed cover is also used when ease of cleaning is a requirement.

Fig.6 Sanitary dome cover


A device used to inject liquid into powder bed. A pipe is installed in the center shaft through the drive section to a single or multiple nozzles installed on the arm.

At the inlet of the Microjet device, a rotary joint is installed where liquid is supplied by a pump or with pressurized air of around 1 to 5 MPa. The liquid is sprayed on to the powder bed from the nozzles as a mist. The spray is aimed at the top of the powder bed where the mixing screw rotates around the vessel leading to a very good mixing of liquid and powder. Using dual fluid nozzles gives better dispersion of the liquid.

Fig.7 Microjet

Lump Breaker

When material has agglomerates during mixing or when agglomerates are generated due to adding of liquids, using a Lump Breaker breaks up the agglomerates to enable good mixing results. The Lump Breaker is not suited to reducing the particle sizes of the mixed materials, breaking up of hard agglomerates or for use with heat sensitive materials.

Fig.8 Lump breaker

Level Control

Since the Vrieco Nauta Mixer has almost no vibration during operation, it is possible to install loadcells on the support brackets. Measuring the weight of the material fed into the machine or discharged from the machine can easily be done. The deviation of the measured weight due to vibration or balance deviations is ±1 kgs. If measured with the Vrieco Nauta Mixer stopped, the accuracy is the same as a simple weighing hopper. Level control using standard level sensor is also available.

Heating, Cooling and Drying

Fitting a jacket on the conical section allows the Vrieco Nauta Mixer to be used for heating, cooling, drying, or reaction of powders. For use as a vacuum dryer or reactor, vacuum/reactor type models are available.

Temperature Measurement

Installing a temperature probe through the gearbox like the Microjet piping is possible allowing the measurement of material temperature during operation.
Installation of temperature probes in the vessel is also possible.


The standard discharge types are flap valve or slide gate. Both manual and automatic pneumatically actuated types are available. Discharge through a ball valve at the bottom of the Vrieco Nauta Mixer or options such as adjustable positioners for the damper are available.

Fig.9 Level control

Fig.10 Operating situation

Fig.11 Small Vrieco Nauta mixers

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