Experimental analysis and rate-based stage modeling of multicomponent distillation in a Rotating Packed Bed

Abstract

Rotating Packed Beds (RPBs) offer increased flexibility and the potential of significant size-reductions for distillation processes through mass transfer intensification. This may be of interest for example for retrofits or off-shore applications. However, validated models for process design of multicomponent distillation in RPBs are not available up to now. To bridge this gap, distillation of binary and ternary mixtures at total reflux was experimentally investigated in an RPB test rig. Depending on the flowrate and rotational speed, up to 10 theoretical stages were achieved in the investigated RPB, corresponding to an HETP (height equivalent of a theoretical plate) of as low as 17mm at the best operating point. With increasing centrifugal acceleration, separation efficiency increased at first, but decreased again at high centrifugal accelerations. Using the rate-based stage approach, a correlation for gas-side volumetric mass transfer coefficient in the RPB is developed. It is capable of reproducing the observed maximum of separation efficiency. Coefficients are fitted for this correlation, based on results obtained from distillation of ethanol/n-propanol. The model is validated using data obtained from distillation of ethanol/water and ethanol/n-propanol/water. Overall volumetric mass transfer coefficients and numbers of theoretical stages are described for most of the data within ±30%.