Fluid displacement efficiency continued

Distillation is a unit operation that has been around for a long time and continues to be the primary method of separation in processing plants, in spite of its inherently low thermodynamic efficiency, The preeminence of distillation for the separation of fluid mixtures is not accidental, but fundamental, and therefore unlikely to be displaced. The reasons are both kinetic and thermodynamic. 

Which extraction mode is the better remains a controversial issue. While the static mode provides longer contact between the sample and solvent, swells the matrix and facilitates penetration of the extractant in its interstices — thereby increasing its efficiency — the dynamic mode allows the analyte to be continuously exposed to the pure (clean) solvent, thus favouring displacement of the analyte s partitioning equilibrium to the mobile phase. Most SFE methods use both modes a static step is employed to ensure close contact between the sample and supercritical fluid without consuming much extractant that is followed by a dynamic step where the extracted analytes are driven to the restrictor and equilibrium is allowed to complete. 

As free water separates from the incoming fluids in the front section, the water level rises. If the water is not removed, it will continue to rise until it displaces all emulsion and begins to spill over the weir into the surge section. On the other hand, if the water level becomes too low, the front section will not be able to water-wash the incoming oil and emulsion, which would reduce the efficiency of the treater. Therefore, it is important to accurately control the oil-water interface... 

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