What is Fractional Distillation?
Fractional Distillation or Distillation or Fractionation is the process of separation of components from a product or mixture (Crude Oil) by heating the mixture to a temperature at which several fractions of the compound will vaporize. Normally when the mixture is heated, the component with the lowest boiling point will vaporize first and will separate out from the mixture. With further increase in temperature other components will start to vaporize and separate.
Fractional Distillation is the most widely used form of separation technology and finds uses in petroleum refineries, petrochemical, and chemical plants, natural gas processing and cryogenic air separation plants. It is one of the most important separation processes.
What are the alternatives to the fractional distillation process?
There are a few alternatives to distillation as mentioned below but require higher investment costs. This is the main reason that distillation remains the main choice in the hydrocarbon industry, especially in large-scale applications.
- Liquid-Liquid Extraction or Solvent Extraction,
- Hydrophilic Pervaporation
- Multi-membrane Permeation Separation
- Adsorption process.
Types of Distillation Processes
There are various types of distillation processes that are popularly used in various industries for separating different products. Those are
- Fractional Distillation
- Extractive Distillation
- Reactive Distillation
- Simple distillation.
- Steam distillation.
- Vacuum distillation.
- Air-sensitive vacuum distillation.
- Short path distillation.
- Zone distillation
- Azeotropic Distillation
- Distillation under Reduced Pressure
- Destructive Distillation
- Industrial Distillation
When the physical properties (mainly boiling point) of the components in a mixture are very close to one another (Example: an azeotropic mixture), the separation method becomes difficult.
Out of the above types, Fractional, Extractive, Reactive and Industrial distillation are the most frequently used ones.
Fractional Distillation is the separation of key components from the product mixture by the difference in their relative volatility or boiling points by heating the product.
In this type of distillation, an external solvent is introduced to the system that increases the separation. The external solvent changes the relative volatility between two close components by extracting one of the components, which forms a ternary mixture with different properties. Once, the extracted component is separated, the solvent is recycled into the system.
In this method, a catalyst bed is used and the targeted component reacts when it is in contact with the catalyst. This separates the targeted component from the rest of the components in the mixture. The column where similar distillation is performed is termed as a reactive distillation column.
Industrial distillation is performed inside a large, vertical, tall cylindrical column. These columns are popularly known as “fractionation towers” or “distillation columns” or “Distillation Towers” and can be found in most of the process plants. The diameter of such Columns can range from about 65 centimeters to 6 meters and heights can range from about 6 meters to 60 meters or more.
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