Homogeneous azeotropic distillation: separability and flowsheet synthesis

When designing a homogeneous azeotropic sequence which separates a binary azeotrope into two pure products, we must first choose the entrainer. In the case of homogeneous azeotropic distillation, separability at finite reflux and at infinite reflux are not equivalent and must be examined separately. By analyzing the profiles of columns operated at infinite reflux in detail, we have shown that a binary azeotrope can be separated with only one distillation column. We present a necessary and sufficient condition which identifies such situations. We have found a necessary and sufficient condition for separability in a two-column sequence. When separation is feasible, this condition indicates the flowsheet of the corresponding separation sequence. We have also shown that separation is always feasible in a three-column separation if the azeotrope we want to separate is a saddle. Finally, we examine two situations where separation is feasible at finite reflux but not at infinite reflux