Countercurrent exchange

About: Countercurrent exchange is a research topic. Over the lifetime, 2255 publications have been published within this topic receiving 28687 citations. The topic is also known as: Countercurrent exchange.

Low-speed rotary countercurrent chromatography using a convoluted multilayer helical tube for industrial separation

Abstract: An industrial-scale countercurrent chromatographic system was developed using a slowly rotating helical device which can be automated and left unattended during the operation It uses a multilayer coiled column consisting of long convoluted Teflon tubing of 085 cm id, which provides sufficient retention of the stationary phase under a relatively high flow rate The column is mounted on a seal-less continuous-flow rotary device which eliminates various complications such as leakage and clogging as often caused by the use of a conventional rotary seal Using a multilayer coiled column with a 10-L capacity, 150 g of crude tea extract was successfully purified, yielding 40 g of epigallocatechin gallate of over 927% purity at a recovery rate of 826% The present system can be scaled up for a kilogram-scale separation

Mass transport in a novel two-fluid taylor vortex extractor

Abstract: Flow instabilities occurring in rotating flows can be exploited as a new approach to liquid-liquid extraction. Two immiscible liquids are radially stratified by centrifugal force in the annulus between corotating coaxial cylinders. When the inner cylinder is rotated above a critical speed, Taylor vortices form in one or both of the fluids. Although the flow pattern yields a relatively small amount of interfacial surface area, the surface is highly active for interphase mass transfer due to the local vortex motion. By adding countercurrent axial flow, efficient continuous processing is also possible. This flow yields a viable extraction process, particularly for fluid pairs that are easily emulsifiable and therefore have limited processing options with the current equipment commercially available. This article demonstrates that two-fluid Taylor-Couette flow with countercurrent axial flow is achievable in practice and explores, experimentally and computationally, the mass-transfer characteristics of the flow. Experimentally, when the vortices first appear, axial dispersion decreases and the interphase mass transfer starts to increase. Upon further increase in differential rotation rate, the extraction performance continues to improve, with the mass-transfer coefficient proportional to the strength of Taylor vortices. This suggests that very high extraction efficiencies can be obtained with even larger relative rotation rates. Furthermore, mass-transfer boundary-layer theory, in combination with computational fluid dynamics, provides a reliable method for predicting the extraction performance.