Theoretical Plate

In the field of chemical engineering a theoretical plate is referred to the several separation processes where the phases like liquid and vapor institute a balance with each other. Those equilibrium stages perhaps are known as equilibrium stages or a theoretical tray. The separation processes being carried out rely on having a series of equilibrium stages and are developed by offering more such stages. Nevertheless, to make it clear, to have more theoretical plates improves the efficacy of the separation process be it a distillation, absorption or similar process.

The concept of equilibrium stages

The concept theoretical plate and trays or equilibrium stages have been employed in creating various kinds of separation. For instance, any physical device which offers healthy contact between the vapor and liquid phases present in industrial-scale distillation columns or laboratory scale glassware distillation columns form factors referred to as plate or tray. For an actual, physical plate is seldom complete efficient balance stage so the number of actual plates is more than the needed theoretical plates.

The bubble cap or valve trays are examples of the vapor and liquid contact devices employed in industrial distillation columns. The trays or theoretical plate employed in industrial distillation columns are produced of circular steel plates and commonly installed within the column at intervals of about 60 to 75cm up the elevation of the column. That particular distance is selected fundamentally for ease of installation and ease of access for future repair or maintenance.

Perforated trays and contacts

There are perforated trays which can be said for simple trays as examples. The necessary connection between vapor and liquid happens as the vapor, flowing upwards through the perforations and arrive into contact with the liquid flowing downwards via the perforations. In contemporary practice, efficient contacting is achieved by installing bubble-caps or valve caps at each perforation to support the formation of vapor bubbles flowing via a thin layer of liquid maintained by a weir on each tray.

In order to create a distillation unit or a related chemical process, the number of theoretical plate or trays needed in the process should be decided considering a similar range of feedstock composition and the wanted degree of separation of the elements in the output fractions. And in industrial continuous fractioning columns theoretical plates or trays are decided by beginning at either top or bottom of the column and calculating material balances, heat balances and equilibrium flash vaporizations for each of the succession of equilibrium stages until the necessary end product composition is obtained.

Questions:

• What is theoretical plate?
• State the significance of the theoretical plate.