Nauta® Conical Screw Mixer

The Nauta® Conical Screw Mixer is a batch mixer specially designed for segregative, free-flowing powders and pastes. The Nauta® Conical Screw Mixers is famous for its low-intensity mixing and is a pioneer in mixing technology. It especially suited to delicate products and processes where very accurate results are required and is synonymous with gentle mixing of large volumes of up to 100,000 liters.

These versatile batch mixers are unique in many ways. Their design provides for a very gentle mixing action with low horsepower consumption. The special mixing action ensures a very homogenous mixture and short mixing times. The conical vessel design allows a wide range of filling capacities and the mass flow characteristic design minimizes segregation upon discharge. Because there are no horizontal internal surfaces, products are completely discharged, minimizing product loss and providing for easy cleaning.

Design

Vessels can be designed for overpressure and under pressure operating conditions and units can be supplied with a variety of accessories including liquid injection, product samplers, high intensity lump breakers, level and temperature probes, load cells for batch weighing and jackets for heating and cooling are some examples.

The basic design consists of a cylindrical screw located at the vessel wall that conveys product from the bottom of the conical vessel to the product surface. The screw is attached to an arm which rotates around the perimeter of the vessel causing convective mixing and shear. The particles at the surface opposite the screw accelerate downward in a mass flow by gravity as the diameter of the vessel decreases. The three actions result in a unique three dimensional mixing action.

How it Works

The Nauta mixer is a convective, low-shear batch mixer that combines axial, radial and tangential flow to achieve thorough, precise homogenization. A rotating, cantilevered (free-hanging) mixing screw conveys the product upward along the wall of the conical vessel, while an orbiting arm moves the screw around the cone. Gravity-driven recirculation delivers uniform, energy-efficient, low-shear mixing while preserving particle integrity.

Product is loaded from the top—manually, by big bag, or via pneumatic/mechanical transfer. Typical speeds are ~70 rpm for the screw and 1–2 rpm for the orbiting arm; screw tip speed can range from 0.5–2 m/s, depending on the product characteristics.

A bottom discharge valve enables complete emptying, reduces manual intervention/cleaning and minimizes cross-contamination between batches (standard on most executions; ball segment valve options available). After discharge, product proceeds to packaging or the next step (e.g. tableting, extrusion, sieving).

Beyond mixing, the system can be configured for heating/cooling, drying (including vacuum), and humidification, and can operate as a live (agitated) hopper to feed downstream equipment such as fluid bed dryers—with or without back-mixing.