Distillation in a Counterflow Concentric-Ring Rotating Bed

Abstract

Developed from rotating zigzag bed (RZB), the counterflow concentric-ring rotating bed uses a rotor composed of stationary–rotating discs, a set of concentric circular rotating rings with perforations, and a liquid distribution at the eye of the rotor, preserving the outstanding characteristics of RZBs consisting of intermediate feeding and multirotors coaxially installed in series in a casing. A mass-transfer model was proposed from which the local gas- and liquid-side mass-transfer coefficients, gas–liquid effective interfacial area, and height equivalent to theoretical plate (HETP) can be calculated. Total reflux distillation experiments were conducted in a counterflow concentric-ring rotating bed at atmospheric pressure using an ethanol–water system, and the mass-transfer end effects were also investigated. The experimental values of overall volumetric gas-side mass-transfer coefficient and HETP agree with the calculated values very well. Obvious end effects exist in the distillation process, and a correlation which takes inner and outer end effects into consideration is given. Compared with RZB, the counterflow concentric-ring rotating bed has lower mass-transfer efficiency, but it has gas–liquid throughput at least 5.576 times greater than that of RZB. Compared with rotating packed bed, the concentric-ring rotating bed has a much higher local gas-side mass-transfer coefficient.

Towards the Development of Advanced Packing Design for Distillation in Rotating Packed Beds

“…The number of theoretical stages is calculated based on an analytical description of the vapor-liquid equilibrium curve. Since ethanol-water is a non-ideal system, the change of relative volatilities (a) with the change of liquid composition is estimated by using the empirical approach proposed by Li et al [30]. Details of the method are described in the Appendix.…”

Studies of CO2 absorption and effective interfacial area in a two-stage rotating packed bed with nickel foam packing

“…Guo et al [15] proposed an innovative approach to isolate the packing zone from the whole RPB and obtained the results of 70% and 30% of the total mass transfer area taking up by the packing and cavity zone, respectively. Developed from rotating zigzag bed (RZB), Li et al [16] presented a new counterflow concentric-ring rotating bed without packing and a model for calculating and experimental measurement of a e of this rotating bed were reported. These above work of a e of Higee equipment were focused on one-stage Higee and little work related to multi-stage Higee.…”

A new crossflow rotating bed, Part 3: Stage efficiency model

“…al. (1997) has proposed an equation to determine the size of the liquid droplets in the rotating packed bed and Li et. al.…”