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Columns
A Fractionating column or fractionation column: is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities.
Fractionating columns are used in small-scale laboratory distillations as well as for large-scale industrial distillations. Fractional distillation is one of the unit operations of chemical engineering. Fractionating columns are widely used in the chemical process industries where large quantities of liquids have to be distilled. Such industries are the petroleum processing, petrochemical production, natural gas processing, coal tar processing, brewing, liquefied air separation, and hydrocarbon solvents production and similar industries but it finds its widest application in petroleum refineries. In such refineries, the crude oil feedstock is a very complex multicomponent mixture that must be separated and yields of pure chemical compounds are not expected, only groups of compounds within a relatively small range of boiling points, also called fractions and that is the origin of the name fractional distillation or fractionation. It is often not worthwhile separating the components in these fractions any further based on product requirements and economics.
Industrial distillation is typically performed in large, vertical cylindrical columns known as “distillation towers” or “distillation columns” with diameters ranging from about 65 centimeters to 6 meters and heights ranging from about 6 meters to 60 meters or more. Industrial distillation towers are usually operated at a continuous steady state. Unless disturbed by changes in feed, heat, ambient temperature, or condensing, the amount of feed being added normally equals the amount of product being removed.
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