Distillation refers to the process of selective boiling and condensation to isolate components in liquid mixtures into their (nearly) purest forms. While distillation can be highly effective as an industrial separation technique, like any industrial separation process it can also present operational challenges that must be managed properly for success.
Many of these issues stem from non-ideal conditions in a column, leading to the formation of an azeotropic mixture with either an increased or decreased boiling point, depending on its concentration and its equilibrium with feed materials.
As such, distillation requires careful monitoring: its target boiling point must be accurately maintained in order to prevent impurities with lower boiling points from infiltrating into the product stream along with desired components.
Fouling is an ever-present problem that requires tailored solutions for every plant, as evidenced by two Dow plants having experienced fouling issues despite following general guidelines and employing specific solutions such as special techniques.
One of the more frequent problems encountered when operating distillation columns is excessive entrainment, which can result in flooding of the column. This problem arises from high vapour flow rates: liquid from less volatile material may be carried up from lower-volatility trays into higher-volatility ones and thus polluting high purity distillates. To remedy this situation, identify its source and reduce flow rates accordingly; testing methods like vapor/liquid sensitivity testing, hydraulic analysis or even gamma scanning can be extremely helpful in diagnosing these issues.
