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.

Countercurrent de-acidification of vegetable oils using supercritical CO2: Holdup and RTD experiments

Abstract: The separation efficiency of packed columns is strongly influenced by hydrodynamics. It is therefore of importance in the design of packed columns the estimation of parameters such as liquid holdup (both dynamic and static), pressure drop and flooding point. In this field, there is a large number of experimental results published for low pressure applications. However, data for high-pressure systems is relatively scarce. In this work, hydrodynamic data was experimentally obtained in a 7.5-m tall, 40 mm i.d. column. In the experiments, the separation of free fatty acids from vegetable oils was studied. Separation efficiency, and static and dynamic holdup were determined for various packing materials (random and structured) at several operating conditions. Through experiments with a carotene tracer, the residence time distribution was measured. Several known correlations, which take into account the buoyancy effect of dense gases, were applied to the experimental data, and good agreement with the results of other authors was observed.

Countercurrent tangential chromatography methods, systems, and apparatus

Abstract: This invention relates to a breakthrough in the art of chromatography allowing 1) larger scale of operation; 2) faster processing time; 3) disposability; 4) reduction of media/resin expenses; and 5) a reduction of capital equipment investment. In this invention, the chromatography column is replaced by a module that consists of two or more interconnected tangential flow filters and static mixers. The chromatography resin flows through this module in a single pass, while similar operations to a regular chromatographic process are performed on the resin (binding, washing, elution, regeneration, and equilibration). The buffers for these operations are pumped into the module in a countercurrent direction to the flow of resin, and permeate solutions from later stages are recycled back into previous stages. This creates concentration gradients in the permeate solutions of the tangential flow filters in the countercurrent direction to resin flow, thus saving buffer volume and increasing process efficiency.

Pressure Drop in a Countercurrent Gas−Flowing Solids−Packed Bed Contactor

Abstract: The equations for prediction of pressure drop in countercurrent gas-flowing solids-packed bed contactors are proposed. The correlations are based on all available data for various constructions, packing elements, and gas and flowing solids properties. The equations give good predictions and are given separately for preloading and loading zones, together with the correlation for the determination of the loading point.

Comparison of cocurrent and countercurrent flow-related enhancement in MR imaging.

Abstract: Patterns of flow-related signal loss and enhancement have been observed in fluid moving perpendicular to the imaging plane on multi-section-acquisition magnetic resonance images. These patterns depend on whether the flow is in the same direction (cocurrent) or opposite (countercurrent) to the direction of sequential section excitation. For a given velocity, flow-related enhancement penetrates deeper into the imaging volume with countercurrent flow than with cocurrent flow. The signal intensity of inner sections is generally greater with countercurrent flow than with cocurrent flow and depends on the velocity. These effects were investigated quantitatively with phantom studies and correlated with theoretical predictions. It was found that the limited penetration of flow-related enhancement with cocurrent flow is a consequence of recently saturated upstream protons flowing into the section to be excited. The flow-related enhancement penetrates farther with countercurrent flow, because inflowing spins have h...