Countercurrent Extraction Cascades

For a high degree of extraction efficiency, it is usual to connect several continuous flow stages to form a countercurrent flow extraction cascade, as indicated in Fig. 3.31. 

For any given stage, n, the component material balance equations for each phase are thus defined by 

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Countercurrent Extraction Cascade with Slow Chemical Reaction... 

A countercurrent extraction cascade with reaction A + B C was considered by Ingham and Dunn (1974), as shown in Fig. 3.40. The reaction takes place between a solute A in the L-phase, which is transferred to the G-phase by the process of mass transfer, where it then reacts with a second component, B, also in the G-phase, to form an inert product, C. 

FIVE STAGE COUNTERCURRENT EXTRACTION CASCADE EQUILIBRIUM STAGE MODEL... 

Five stage countercurrent extraction cascade with backmixing Equilibrium stage model... 

Dynantics of Heat Exchangers, Simple Batch Extraction, Multi-Solute Batch Extraction, Multistage Countercurrent Ctiscade, Extraction Cascade with Backmixing, Countercurrent Extraction Cascade with Reaction, Absorption with Chemical Reaction, Membrane Transfer Processes... 

Analyze countercurrent extraction cascades without reflux. 

A countercurrent cascade allows for more complete removal of the solute, and the solvent is reused so less is needed. Figure 7.10 is a schematic diagram of a countercurrent extraction cascade. Extract and raffinate streams flow from stage to stage in countercurrent fashion and yield two final products, raffinate RN and extract Ey For... 

We wish to remove acetic acid from water using pure isopropyl ether as solvent. The operation is at 293 K and 1 atm (see Table 7.2). The feed is 45 wt% acetic acid and 55 wt% water. The feed flow rate is 2000 kg/h. A multistage countercurrent extraction cascade is used to produce a final extract that is 20 wt% acetic acid and a final raffinate that is also 20 wt% acetic acid. Calculate how much solvent and how many equilibrium stages are required. 

Example 10.3. As shown in Fig. 10.22, a countercurrent extraction cascade equipped with a solvent separator to provide extract reflux is used to separate methylcyclopentane A and n-hexane C into a final extract and raffinate containing 95wt% and 5wt% A, respectively. The feed rate is 1000 kg/hr with 55 wt% A, and the mass ratio of aniline, the solvent S, to feed is 4.0. The feed contains no aniline and the fresh solvent is pure. Recycle solvent is also assumed pure. Determine the reflux ratio and number of stages. Equilibrium data at column temperature and pressure are shown in Fig. 10.23. Feed is to enter at the optimum stage. 

A schematic representation of a countercurrent extraction cascade is shown in Fig. 12.21, with stages numbered from the top down and solvent V +i entering at the bottom. The group method of calculation can be applied with the equations written by analogy to absorbers. In place of the IC-value, the distribution coefficient is used... 

Countercurrent Extraction Cascades for Partially Miscible Systems... 

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