Pressure control in the tower.
CV, Pressure in the overhead accumulator
MV, valve controlling the heat duty to the overhead condenser

Heavy key control
CV, Composition analyzer, X_D
MV, Reflux valve

N/A (direct releases to flare)

Pressure and product analyzers

Pressure control in the overhead accumulator
CV, Pressure in the accumulator
MV, valve controlling the heat duty to the overhead condenser

Tray temperatures in the stripping and enriching sections

Pressure drop across trays

Level control in the bottoms accumulator.
CV, Liquid level in the accumulator
MV, Valve controlling the bottoms flow