Rührern

Rührern, plural of Rührer, are stirring devices installed in vessels to mix liquids, suspend solids, or promote heat transfer. They transmit mechanical energy from a rotating shaft to the contents, creating flow fields and turbulence that enhance homogenization and chemical reaction control.

Common types include radial-flow impellers such as Rushton turbines, which push fluid outward from the shaft, and axial-flow impellers like hydrofoils or pitched-blade turbines, which promote circulation along the shaft. Other arrangements include paddles, anchors, and propellers. The choice depends on viscosity, desired shear, gas handling, and chemical compatibility.

Rührern are used across chemical, pharmaceutical, food, cosmetics, and wastewater sectors, in reactors, mixing tanks, fermentation systems, and crystallizers. They are often combined with baffles to reduce vortexing and improve energy distribution. In sanitary processes, hygienic Rührern meet CIP/SIP standards and are made from corrosion-resistant materials to facilitate cleaning and sterilization.

Design parameters include impeller type, number, and placement, shaft speed, power input, Reynolds number, and shear rate. Scale-up from laboratory to industrial size requires careful consideration of flow patterns, mixing time, and heat transfer. Maintenance focuses on seals, bearings, and cleaning to prevent contamination and ensure reliable operation.