What Is Distillation and What Are Its Methods
In industry, chemistry, and engineering, among the most fundamental and effective methods used to separate mixtures is distillation. Separating the components of liquids from one another by making use of their different boiling points is called distillation. So which distillation method is used when? In this article we examine distillation systems and explore the working principles, applications, and advantages of each.
There are four main types of distillation method.
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Simple distillation
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Fractional distillation
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Steam distillation
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Vacuum (reduced pressure) distillation
1. Simple Distillation:
Simple distillation, the simplest and most basic distillation method, is used to separate two liquids whose boiling points are sufficiently different from one another. In this method the mixture is heated with a heat source, and the liquid that evaporates is condensed by a condenser and collected.
Applications:
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Production of alcoholic drinks such as ethanol and water
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Purification operations at laboratory scale
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Home-made perfume and essential oils
Advantages:
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Easy to set up and to apply
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Low cost
Disadvantages:
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Inadequate for separating liquids whose boiling points are close
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The yield can be low
2. Fractional Distillation:
Fractional distillation is used to separate liquid mixtures whose boiling points are close to one another. In this method the mixture is placed in a distillation column and heated in stages at different temperatures. At each temperature the liquid with the matching boiling point evaporates and is collected in a separate vessel.
Applications:
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Separation of petroleum fractions (gasoline, diesel, kerosene, and so on)
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Purification of organic chemicals
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Production of perfumes and essential oils
Advantages:
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Effective at separating complex mixtures
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High yield
Disadvantages:
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A more complex setup than simple distillation
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Calls for more time and energy
3. Steam Distillation:
Steam distillation is used to separate liquids that are heat-sensitive or have a high boiling point. In this method steam is introduced at the lower part of the mixture, and the liquid that evaporates is condensed by a condenser and collected.
Applications:
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Purification of heat-sensitive vitamins and medicines
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Production of glycerol and fatty acids
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Obtaining aromas and flavorings in the food industry
Advantages:
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Does no damage to heat-sensitive liquids
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Effective at separating liquids with a high boiling point
Disadvantages:
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Calls for additional equipment such as a steam generator
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A more complex setup than simple distillation
4. Vacuum (Reduced Pressure) Distillation:
Vacuum distillation is a distillation method carried out under low pressure. In this method the pressure above the mixture is lowered, so that the boiling point is reached at lower temperatures. Heat-sensitive liquids therefore take less damage and can evaporate even under vacuum.
Applications:
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Purification of polymers with a high molecular weight
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Production of heat-sensitive medicines and chemicals
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Separation of petroleum fractions (vacuum gas oil and so on)
Advantages:
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Does no damage to heat-sensitive liquids
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Allows distillation at low temperatures
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Effective at separating liquids that can evaporate even under vacuum
Disadvantages:
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Calls for additional equipment such as a vacuum pump
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A more complex setup than simple distillation
Author:
Industrial Design Engineer