Selection and Sizing of A Distillation Column


To design a distillation column and its selection as well as sizing need ideas of vapour and liquid phase thermodynamics because it helps to calculate minimum number of equilibrium stages on which the needed separation take place. In addition, a continuous columns minimum reflux ratio factor depends on the VLE data. As a part of introduction, a brief requirements and tools used for sizing of this separation equipment discussed.

For the learner Fenske-Underwood equation is enough to understand about minimum reflux ratio and minimum number of stages. At last, safety and economical factors shapes up the drawing and mechanical parts of the column.

Distillation word refers to the separation operation in chemical and petroleum industries. Only the concept of boiling point variation draws attention towards the idea of distillation. Fractional distillation or fractionation word is awarded for this purpose only. 50% of a plant’s energy consumption falls under the distillation account. Also due to its promising separation makes it still be alive in latest chemical industries also.

New adaptable technologies of solvent extraction, adsorption, membrane and reactive distillation turn the old methods into hybrid system. Distillation processes types like extractive distillation and reactive distillation are now in demand.

Batch distillation and continuous distillation operation mode depend on the factor of time only and works similar in theory.

Column internals:

Any column equipped with internal set up that has only purpose of providing mass and heat transfer. The internal structures directly affect the vapour and liquid phase mass and heat transfer simultaneously. Parts like trays, re-distributors, packings, distributors and baffles are some of them. Each part ultimately should provide the purpose of enough contact of the phases. Column height and diameter are calculated finally by inclusion of these internal parts. In immediate need of design, two internal parts are enough in design calculations that would be trays and packing. Either of these two parts are main internal structures that determine the separation, efficiency and capacity of the column.

During the selection of the tray, sieve, bubble cap and valve trays are common in use. Packing is of random and structured by packing materials like saddles and rings.
Comparison of Distillation Column Trays