Mixers, Dividers, Separators Reference Page
Gotta Keep ’Em Separated

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Intro to Mixers, Dividers, and Separators

Mixers, dividers, and separators are among the simplest and most common unit operations used in process flow diagrams. Although the equipment itself may be simple, the material balances associated with them are fundamental to analyzing and solving process flowsheets.

This video introduces the basic behavior of mixers, dividers, and separators and shows how to apply mole balances to each of them.

Gotta Keep ’Em Separated

Video explanation

Visuals

Definitions

Mixer
Combines multiple input streams into a single output stream.
For each species, the outlet flow equals the sum of that species entering in all inlet streams.

The outlet composition equals the total flow of each species divided by the total flow of all species.

Mixers can be as simple as a pipe tee or as complex as a stirred tank.

Divider
Splits a single input stream into multiple output streams.

Each outlet stream has the same composition as the inlet stream, but the flow rates differ.

Separator
Separates an input stream into multiple output streams with different compositions than the inlet stream.

If all outlet streams have the same composition as the inlet stream, the device is simply a divider, not a separator.

Split Fraction, \(t_i\)
The fraction of a given species in the inlet stream that exits through a particular outlet stream.

For separators with two outlet streams, the split fractions for a given species sum to 1.

For separators with more than two outlets, the split fractions for that species across all outlet streams must sum to 1.

Composition
The mole fraction or mass fraction of each species in a stream.

See What the Frac? for more details.