(123a) Optimal Operation of Azeotropic Distillation Columns

Heterogeneous azotropes are common in distillation operations involving the removal of a component through the overhead. The azeotrope usually consists of water and other non water miscible organic component such as toluene. A common scheme to separate water from ethanol is to add a third component (benzene) to the column in order to form a low boiling azeotrope between benzene and water and separate the ethanol from the water.

In certain operations, however, it is critical to maintain the solvent to water ratio inside the column in order to prevent falling in the ?wrong? side of the azeotrope. This presentation explains how a relatively straight forward separation can go wrong by not watching the solvent to water ratio inside the column. In some instances, running a column ?solvent-rich? could cause the solvent to accumulate and bulge inside the column, bulging could have fatal consequences if the accumulating solvent is sensitive in high concentrations.