Experimental Investigation and Design of Rotating Packed Beds for Distillation

Abstract

Improved separation efficiency and flexibility are of major importance in the downstream processing of liquid mixtures in the chemical industry, in order to respond to fluctuating demand and raw material quality. The application of the high gravity (HiGee) concept in Rotating Packed Beds (RPBs) has the potential to meet these requirements for the separation of liquid mixtures. The current work provides an analysis of the potential improvements gained by RPBs. The flexibility of RPBs is analyzed based on an experimental investigation, which evaluates the effect of rotational speed, different rotor configurations and F-factors on separation efficiency. Batch distillation experiments were performed in a single-stage pilot plant RPB with the ethanol-water system under total reflux conditions at atmospheric pressure. An analysis of the number of transfer units (NTU) reveals that separation efficiency in RPBs is not necessarily proportional to the rotational speed. There is rather an optimal rotational speed for each investigated rotor configuration. A maximum of 3.7 transfer units was achieved for a rotor with outer packing diameter of 0.36 m and an axial height of 0.01 m. Special emphasize in this experimental study is placed on the analysis of the contributions to mass transfer from the packing and the casing, which can contribute significantly to the overall mass transfer in RPBs.