Search results
Results From The WOW.Com Content Network
The liquid phase flows downward through the column via gravity, [1] while the gas phase flows upward. These two phases come in contact in correspondence of holes, valves or bubble caps that fill the area of the plates. [2] Gas moves to the higher plate through these devices, while the liquid moves to the lower plate through a downcomer. [1]
The theoretical plate concept was also adapted for chromatographic processes by Martin and Synge. [6] The IUPAC's Gold Book provides a definition of the number of theoretical plates in a chromatography column. [7] The same equation applies in chromatography processes as for the packed bed processes, namely:
Packed columns have a continuous vapor-equilibrium curve, unlike conventional tray distillation in which every tray represents a separate point of vapor-liquid equilibrium. However, when modeling packed columns, it is useful to compute a number of theoretical plates to denote the separation efficiency of the packed column with respect to more ...
Stripping is mainly conducted in trayed towers (plate columns) and packed columns, and less often in spray towers, bubble columns, and centrifugal contactors. [2] Trayed towers consist of a vertical column with liquid flowing in the top and out the bottom. The vapor phase enters in the bottom of the column and exits out of the top.
A larger surface area allows more cycles, improving separation. This is the rationale for a Vigreux column or a packed fractionating column. Spinning band distillation achieves the same outcome by using a rotating band within the column to force the rising vapors and descending condensate into close contact, achieving equilibrium more quickly.
Structured packing. The term structured packing refers to a range of specially designed materials for use in absorption and distillation columns [1].Structured packings typically consist of thin corrugated metal plates or gauzes arranged in a way that force fluids to take complicated paths through the column, thereby creating a large surface area for contact between different phases.
However, when modeling packed columns it is useful to compute a number of theoretical plates to denote the separation efficiency of the packed column with respect to more traditional trays. Differently shaped packings have different surface areas and void space between packings. Both of these factors affect packing performance.
For a packed column, the cross-sectional area of the column exit flow path is usually taken as 0.6 times the cross-sectional area of the column. Alternatively, the linear velocity can be taken as the ratio of the column length to the dead time. If the mobile phase is a gas, then the pressure correction must be applied.