Vrieco-Nauta Conical Screw Mixers

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.

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.

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.

Size Range/ Capacity: 5 liters to 60,000 liters

Materials of Construction: Steel, Stainless Steel, Hastelloy and other alloys
Available designs:

  • Cantilevered Screw design (no bottom support)
  • Radial Locator Screw design ( guide ring for very large units)
  • Single bottom discharge or Multiple side discharges
  • Gear drive systems as standard – oil and grease lubrication available
  • Belt drive systems available for sanitary applications – no lubrication inside the vessel
  • Clean in place designs


  • Mixing and homogenization of powders, pastes and slurries
  • Granulation or agglomeration of powders
  • Addition or injection of liquids into dry powders
  • Reaction under vacuum or pressure conditions
  • Processing of powders under inert conditions
  • Heating and cooling of powders
  • Storage of non free flowing powders
  • De aeration or densification of powders
  • Homogenization of particle size and color

Vrieco-Nauta conical screw mixers were first developed and manufactured by the J.E Nauta Company after the Second World War. The company resided in Haarlem, the Netherlands and started by manufacturing these mixers for the cattle feed industry. The unique design and features of new design allowed Nauta to quickly expand into other markets and soon they licensed the technology to other companies around the world. Hosokawa Micron acquired Nauta and then Vrieco in the early 1980’s.