Theoretical plate

A theoretical plate in many separation processes is a hypothetical zone or stage in which two phases, such as the liquid and vapor phases of a substance, establish an equilibrium with each other. Such equilibrium stages may also be referred to as an equilibrium stage or a theoretical tray. The performance of many separation processes depends on having a series of equilibrium stages and is enhanced by providing more such stages. In other words, having more theoretical plates increases the efficacy of the separation process be it either a distillation, absorption, chromatographic, adsorption or similar process.

Applications

The concept of theoretical plates and trays or equilibrium stages is used in the design of many different types of separation.

Distillation columns

The concept of theoretical plates in designing distillation processes has been discussed in many reference texts. [cite book|author=B.S. Furnis et al|title=Vogel's Textbook of Practical Organic Chemistry|edition=5th Edition|publisher=Longman Scientific|year=1989|id=ISBN 0-582-46236-3] cite book|author=Kister, H.Z.|title= Distillation Design|edition=1st Edition |publisher=McGraw-Hill|year=1992|id=ISBN 0-07-034909-6] cite book|author=Perry, Robert H. and Green, Don W.|title=Perry's Chemical Engineers' Handbook|edition=6th Edition| publisher=McGraw-Hill|year=1984|id=ISBN 0-07-049479-7] Any physical device that provides good contact between the vapor and liquid phases present in industrial-scale distillation columns or laboratory-scale glassware distillation columns constitutes a "plate" or "tray". Since an actual, physical plate is rarely a 100% efficient equilibrium stage, the number of actual plates is more than the required theoretical plates.

: $N\_a\; =\; frac\{N\_t\}\{E\}$

In chromatography, the HETP may also be calculated with Van Deemter's equation.

Other applications

The concept of theoretical plates or trays applies to other processes as well, such as capillary electrophoresis and some types of adsorption.

ee also

*Batch distillation
*Continuous distillation
*Extractive distillation
*Fenske equation
*Fractional distillation
*McCabe-Thiele Method

References

External links

* [http://lorien.ncl.ac.uk/ming/distil/distil0.htm Distillation, An Introduction] by Ming Tham, Newcastle University, UK
* [http://www.nt.ntnu.no/users/skoge/publications/1999/DistillationTheory/original/distillationtheory.pdf Distillation Theory] by Ivar J. Halvorsen and Sigurd Skogestad, Norwegian University of Science and Technology, Norway