Fractionating column

A vertical column that separates a mixture into fractions by repeatedly vaporizing and condensing components with different boiling points. Its repeated vapor–liquid contact produces progressively different compositions along its height.

Vapor–liquid equilibrium: The condition in which vapor and liquid phases coexist without net transfer of a component between them. Each contact stage approaches this equilibrium, redistributing components between rising vapor and descending liquid.
Distillation: A separation process that vaporizes a liquid mixture and condenses vapor to exploit differences in volatility. A fractionating column is the apparatus for carrying out repeated distillation contacts.
Petroleum refining: The industrial processing of crude oil into fuels, lubricants, and chemical feedstocks. Refineries use large fractionating columns to separate crude-oil mixtures into boiling-range cuts.
Simple distillation: Distillation using a single vaporization and condensation step, without a fractionating column. It suits widely separated boiling points but provides less repeated separation.
Reflux: Liquid returned to a separation column to flow downward and contact rising vapor. Returning condensed liquid strengthens repeated separation inside the column.
Boiling point: The temperature at which a liquid's vapor pressure equals the surrounding pressure. Boiling points help predict the order in which mixture components enter the vapor.
Crude oil distillation: The separation of crude oil into fractions by heating and condensing it at different temperatures. Atmospheric and vacuum columns recover major refinery streams from crude oil.
Flash distillation: A process in which a liquid mixture is partly vaporized in one pressure or temperature change, separating into vapor and liquid. Unlike a fractionating column, it relies on one equilibrium split rather than repeated contacts.
Theoretical plate: An idealized stage in which vapor and liquid leaving each other are in equilibrium. Plate efficiency estimates how many effective equilibrium contacts the column provides.
Vapor pressure: The pressure exerted by a vapor in equilibrium with its liquid or solid phase. Differences in vapor pressure drive preferential vaporization within the column.

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