Development of separation in countercurrent flow systems

In the flow configuration of a countercurrent bulk flow of two phases or regions in one device or column, with the force acting perpendicular to the directions of bulk flow of 

System type (1) The same phase flows countercurrently in two regions of the device in the presence of an external force or temperature gradient, or concentration gradient or partial pressure gradient 

System type (2) Two different pre-existing immiscible phases introduced into the device/column move countercurrent to each other and leave the device/ column. Examples include gas-Uquid absorption/ stripping solvent extraction/back extraction moving-bed adsorption supercritical extraction. 

System type (3) Two different immiscible phases flow countercurrendy in the device/column different immiscible phases are generated from one feed input stream into the column by the application/withdrawal of thermal energy. Examples include distillation (vapor-liquid system), melt crystallization (solid-liquid system). 

System type (4) Two miscible phases flow countercurrently in two regions of the device separated by a membrane. One of the phases may be generated from one feed phase by the application of pressure energy. Examples include reverse osmosis, ultrafiltration, microflltration, gas permeation, pervaporation. Examples where the other phase is introduced from outside are electrodialysis, dialysis, sweep vapor/ liquid based system. 

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