Countercurrent methods disadvantages

B3. You want to use both co-current and countercurrent absorbers in a process. Sketch as many ways of doing this as you can think of. What are the advantages and disadvantages of each method ... 

Scaled-up elution chromatography and simulated countercurrent systems both have advantages and disadvantages. It makes sense to try to combine these two methods and develop hybrid systems that have some of the characteristics of both the other types. 

Multi-stage extraction is used to achieve a higher efficiency of separation, in which the product is almost completely removed from the raffinate. The solvent is split up into several portions and fed to a series of mixers and settlers. The disadvantage of this method is the need to use large volumes of solvent. A more complicated system, called countercurrent, multi-stage extraction, uses a series of mixers and settlers arranged as before, but the feed liquid and pure solvent are passed through the system in opposite directions, that is counter-currently. Continuous countercurrent operation may be carried out by means of spray columns, packed columns (similar to those used in distillation), plate columns, or, sometimes, bubble cap columns. 

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