Robust control of homogeneous azeotropic distillation columns

The entrainer feed used in homogeneous azeotropic distillation provides an extra degree of freedom in the steady‐state design compared to simple distillation. In this article, we discuss the control of azeotropic distillation columns in the region close to minimum entrainer feed. Both industrial experience and previous research indicate that this is a difficult task. However, by considering the high‐frequency behavior (initial response) of the column, we show that tight and robust control can be obtained with simple single‐loop PI controllers. The results depend on the presence of high‐frequency phenomena such as flow dynamics.