Report Example on the Distillation Process

The distillation process is a method that separates two or more liquid components in a mixture. This is achieved by using the relative volatility principle or the boiling points of the components. How easy or hard the distillation process depend on the difference in relative volatility of the liquid components in the mixture. Nonlinearity increases with the relative volatility of the liquids hence it is easier to separate the liquids (Halvoren & Skugestad, 2000). The process is all about boiling the mixture and collecting the vapor through condensation. The liquids have different boiling points that allow some liquids to vaporize faster than others. The vapor is condensed, and the remaining liquid is collected. The vapor is composed of the light components, and the remaining liquid consists of the heavy element.

The condensed component is then put back into the still, and the process is repeated. The process allows more separation as the vapor becomes richer with the lighter component. This separation and collection of vapor are made easier by the collecting plate (trays) that enhance the transfer. The trays are placed one over the other in a cylindrical forming a column. The distillation process can be done in different modes; continuous, batch or semi-continuous mode.

Different components facilitate the distillation process. There are the distillation columns that are designed differently to perform the separation tasks. Based on how they are operated, the column distillers can be classified into the batch and continuous columns (Gorak & Sorensen, 2014).

Batch columns; distillation is done in batches. The feed is put in the column, and once the distillation process is complete, another batch is introduced.

Continuous column; here, the process is continuous with a continuous feed stream. They are the most common and most preferred. Unless there is a problem with the column, the process does not encounter any interruptions. They can be classified further according to the nature of the feed they process;

the binary column that contains two columns and the multi-component with more than two components.

Some product streams they have; the multi-product column that has more than two product streams.

Where the extra feed exits; extractive distillation where the extra feed appears at the bottom and the azeotropic where it appears at the top product stream.

Type of column internals; tray and packed columns.

There is a reboiler that provide the necessary vaporization for the process. They act as the

Heat exchangers are transferring the required amount of energy to boil the liquid at the bottom of the column. There is the jacketed kettle, kettle-type, thermos-syphon and internal reboilers. Recent technology has introduced the self-cleaning heat exchangers, where particles are added to the stream to score the surface, eliminating the foul smell from the mixture. Another equipment is the condenser that cool and condense the vapor leaving the top of the column (RWTUV, 2005). It is condensed for easier collection.

The columns have certain features and design to as to separate the mixture into the components. Hence there are the internal and external components of the columns. The column internals is mainly the plates and trays which have different designs. The bubble cap tray has riser or chimney that fit each hole and a cap covering the riser. The cap is such in a way that it allows vapor to escape from the chimney. The vapor is then discharged through the slots in the cap and bubbles through the liquid on the tray. The sieve trays are necessarily metals with drilled holes that vapor passes through. The holes are designed in specific ways; their number, arrangement, and size, to make the process effective. The valve trays have perforations covered by liftable caps. The vapor lifts the caps to pave its way out. The caps are lifted in a way that direct the vapor in a horizontal manner into the liquid enabling easier mixing compared to other tray designs (RWTUV, 2005).

The liquid and vapor then flow in a tray column that each has two conduits, downcomers, and one each side. The liquid then flows from one tray to the next naturally. There are were air in every tray that ensure some liquid, holdup. As the liquid drop, the vapor is forced up through the holdup and the space left, active tray area, in the tray above.

The trays are designed to maximize vapour-liquid contact. The contact ensures better separation of the liquid components thus better column performance. The many the number of trays the better but if their design is appropriate, then less will be needed. However, structured packing could be used. Specifically designed materials are incorporated together for the distillation and absorption process. There are corrugated metal plates that maximize contact between the distillation phases.

References

Gorak, A., & Sorensen, E. (2014). Distillation: Fundamentals and principles.

Halvoren, I. J., & Skugestad, S. (2000). Distillation Theory. 7491 Trondheim Norway: Norwegian University of science and technology.

RWTUV. (2005). Distillation Principles. -Dubai. http://chemichal-engineering.blogspot.in/2011/11/distillation.html