Steam Distillation is a special type of separation process for temperature sensitive materials like natural aromatic compounds. Some organic compounds tend to decompose at higher temperature and normal distillation does not suit their purpose. So steam/water is added to the apparatus and the temperature of the compounds are depressed, evaporating them at lower temperature. Once the distillation is accomplished the vapors are condensed and hence there is the separation of the constituents at ease.
Literally speaking it is a unit operation, more or less a physical separation process. No chemical reaction takes place. It is all about the difference in boiling point of the constituent that make up the liquids. At a certain instance of time the boiling point of the natural products in the liquid form emulate the atmospheric pressure.
The principle behind steam distillation is very simple. It is a way of separating miscible liquid based on their volatilities. The boiling point of the products are minimized, permitting the constituents to be vaporised. The vapor pressure exerted by the liquids differ in strength which is a function of temperature. The boiling of the liquids take place. At a certain instance of time the boiling point of the natural products in the liquid form emulate the atmospheric pressure. The result is that the the vapor pressure of the whole system increases.
Steam distillation is a process employed to extract essential oils from organic plants by passing steam generated through the plant material. Temperature sensitive compounds which would normally decompose through simple distillation vaporise at lower temperatures when subjected to steam in the distillation column. This allows for the separation of essential oils, which tend to be less soluble in boiling water, from chemically complex materials.
When the steam is passed through the organic material, tiny pockets holding the essential oils open to release the essential oil molecules without doing any damage to these delicate components. The distillate obtained will contain a mixture of water vapour and essential oils which finally return to their liquid form in the condensing apparatus. Then they are separated using a Florentine separator.
In case of essential oils, using steam allows the distillate to retain the more delicate flavours and aromas which would otherwise breakdown if high temperatures is applied. This is a great process to extract essential oils from aromatic plants to flavour liqueurs.
Steam Distillation is used at wide scale for the manufacturing of essential oils like perfumes. In this process, steam is passed through the plant material containing the desired oil. It is used in synthesizing of complex organic compounds too. Orange oil and Eucalyptus oil are obtained at industrial scale using this method. Apart from that, Steam Distillation processes is also used in petroleum industries & in the production of consumer food products.