Overhead
Vapor
Boilup
Feed
Distillate
Vent
Reflux
Steam
L
L
T
T
Bottoms
Figure 2.1 Distillation column control.
8 ◾  Distillation Control, Optimization, and Tuning
volatile components in a distillate stream at the top of a distillation column and the less volatile components in a bottoms
stream (Figure 2.1). The inlet and outlet stream flow rates
are the manipulated variables in distillation column control.
A manipulated variable is usually the flow rate of a stream
that has an automatic valve connected to a controller output
signal.
2.1 Distillation Column Inlet Streams
For a continuous binary (two-component) distillation column,
there are three streams entering the column: