ABSTRACT
For the operation and control of distillation column, there are a number of constraints that must not be violated. The most familiar mechanical constraint in the distillation system is the pressure drop and hydraulics associated with flooding. The boilup is manipulated by a controller for a temperature point in the stripping section, and the distillate or reflux is manipulated by another controller for a temperature point in the rectification section. The mass transfer in a stripping section becomes mass transfer rate limited in liquid phase. The mass transfer in a rectification section becomes mass transfer rate limited in the vapor phase. The main column constraint because of flooding is associated with the vapor traffic and pressure drop across the trays or packing in the distillation column. The mass transfer rate limit for stripping light key impurity from the bottoms stream was presented. The mass transfer rate limit for absorbing heavy key impurity from the overhead vapor stream was also presented.
