Binary Component Distillation

Table of Contents

What is Binary Component Distillation?

Binary component distillation is the separation of a liquid mixture containing two different components with differing volatilities. By heating a liquid mixture of two components, the more volatile component will vaporize and can be collected and condensed. Binary component distillation units often operate as a continuous process and with a multi-stage distillation column. This multi-stage distillation column will have a certain amount of trays or stages which could be calculated using the McCabe-Thiele graphical method [1]. Binary component distillation differs from a simple flash distillation unit as binary component distillation is a multi-stage process due to the trayed distillation column while flash distillation is a single stage process with a flash drum. The trays in these distillation columns would also typically contain packing to improve liquid-vapour contact which gives more opportunity for the more volatile component to vaporize [4].

How to Build a Binary Component Distillation Unit

The key unit in a binary component distillation unit is the multi-trayed distillation column. This is where the separation between the two components will take place which are aided by the trays and packing that enables more liquid-vapour contact. Below the distillation column, a boiler or kettle is required to first heat the mixture and vaporize the more volatile component. The heavier and less volatile component stays in the liquid phase and exits the distillation column through a bottoms exit stream while the lighter and more volatile vapour phase component rises to the top of the distillation column. At the top of the column, the vapour product is cooled by a condenser and re-enters the liquid phase where it is collected by a top product stream receiver [2]. A binary component distillation unit can operate as a continuous process but can also periodically shut off the feed stream and run on reflux in which remaining unseparated feed liquid is cycled back into the distillation column to be heated again. To enable this reflux process, a reflux drum would be added to the binary component distillation unit which holds the condensed vapour coming from the top product stream before it is either put back into the column as reflux, or go to a receiver as a final separated liquid product. The final separated liquid product can be passed to a receiver if it has gone through the distillation column enough times to achieve a specific level of purity. The higher the desired purity level of products, the more times the feed would likely have to pass through the distillation column [4].

Advantages and Disadvantages of Binary Component Distillation

Industry Applications

Binary component distillation is a very effective method to separate a liquid mixture of two components. An industry that frequently uses this process to a high degree of success is the petroleum and oil refinery industry. A common crude oil of mixture of benzene and toluene can easily be separated with a high degree of purity by binary distillation. Benzene being the more volatile component vaporizes and condenses to be collected in the top stream while toluene exits the column through a bottoms stream. The desalination of ocean water also uses binary distillation as salts and minerals can be extracted from salt water to create fresh water. Figure 3 below shows a sample multi-stage binary distillation unit for the desalination of water.

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