Accurate Wet-type Centrifugal Classification Using an Almost Rigidly Rotating Flow [Translated]†

Abstract

The authors propose a new system for accurate wet-type centrifugal classification that employs an almost rigidly rotating through-flow. This flow can be produced within a rapidly rotating double-walled container, without producing any turbulent fluctuation. We have conducted both batch and continuous classification using a double-walled cylinder-sphere container in classification experiments and in theoretical and numerical flow analyses. The batch type exhibited decreasing cut size and increasing classification accuracy when the Ekman number decreased (i.e., rotation rate increased) while the Rossby number remained constant, or when the Rossby number decreased (i.e., through-flow rate decreased) and the Ekman number remained constant. With the continuous type, achieved by extracting the coarse product continuously, the cut size decreased as the extraction rate increased, but the sharpness index was almost as high as that for the batch type when the extraction rate was below the threshold value, which was reduced when the Ekman and Rossby numbers decreased.† This report was originally printed in J. Soc. Powder Technology, Japan. 36(12), 891-896 (1999) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Powder Technology, Japan.

Keywords

• wet-type centrifugal classification
• almost rigid rotation
• continuous-type classification
• ekman layer
• partial fractional efficiency