Equilibrium Separation Stages Reference Page
The Shocking Truth About Equilibrium Stages—Are You Doing It Wrong?

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Intro to The Shocking Truth About Equilibrium Stages—Are You Doing It Wrong?

Many industrial separation processes are modeled as a series of equilibrium stages. In each stage the entering streams mix, reach thermodynamic equilibrium, and then separate into outgoing phases.

This model forms the basis for analyzing processes such as distillation columns, flash separators, and liquid–liquid extraction units. The videos on this page introduce the equilibrium-stage concept and demonstrate how it is used in separation calculations.

Part 1

This video introduces the equilibrium-stage model and explains the assumptions used when modeling separation processes such as distillation columns.

Visuals

Part 2

This video demonstrates equilibrium-stage calculations for multicomponent mixtures using Raoult’s Law.

Visuals

Part 3

This video applies the equilibrium-stage concept to liquid–liquid extraction, demonstrating how partially miscible liquids can be separated using stagewise contact.

Visuals

Examples and Definitions

Definitions

Equilibrium Separation Stage
A theoretical stage in which incoming streams are assumed to mix completely and then separate into outgoing phases that are in thermodynamic equilibrium with each other.
Phase Fraction
The fraction of the total mixture that exists as a given phase. Phase fractions can be expressed on either a mole basis or a mass basis, which generally give different numerical values.
Liquid Fraction
The fraction of the total mixture present as liquid. It may be defined using either mass fractions or mole fractions.
Vapor Fraction
The fraction of the total mixture present as vapor. It may be defined using either mass fractions or mole fractions.
Distillation
A separation process that uses repeated vaporization and condensation to separate components based on differences in volatility.
Liquid–Liquid Extraction
A separation process in which a solute is transferred from one liquid phase to another by contacting partially miscible liquids and allowing them to separate.