Sequencing for Azeotropic Distillation

Kubierschky sequence -for azeotropic distillation piSTILLATION, AZEOTROPIC AND EXTRACTIVE] (Vol 8)... 

Figure 11-9. Sequences for the distillation of temaiy mixtures no azeotropes. Conqionent A is most...

Figure 8.28. Phase equilibria map and sequence for extractive distillation of a binary azeotropic mixture (1,3) with a high boiling entrainer (2) split 1 2,3 in the first column.

Historically azeotropic distillation processes were developed on an individual basis using experimentation to guide the design. The use of residue curve maps as a vehicle to explain the behavior of entire sequences of heterogeneous azeotropic distillation columns as weU as the individual columns that make up the sequence provides a unifying framework for design. This process can be appHed rapidly, and produces an exceUent starting point for detailed simulations and experiments. 

Exploitation of Homogeneous Azeotropes Homogeneous azeotropic distillation refers to a flowsheet structure in which azeotrope formation is exploited or avoided in order to accomplish the desired separation in one or more distillation columns. The azeotropes in the system either do not exhibit two-hquid-phase behavior or the hquid-phase behavior is not or cannot be exploited in the separation sequence. The structure of a particular sequence will depend on the geometry of the residue curve map or distillation region diagram for the feed mixture-entrainer system. Two approaches are possible ... 

FIG. 13-66 Conceptual sequence for separating maxinuTm-hoiling binary azeotrope with pressure swing distillation. 

The separation problem is defined as finding at least one feasible separation sequence for breaking a binary azeotrope AB by means of an entrainer C using only homogeneous distillation. The solution of this problem depends greatly on the existence of distillation boundaries. There are two possibilities ... 

A second example of the use of liquid-liquid immiscibilities in an azeotropic distillation sequence is the separation of the ethanol-water minimum-boiling homogeneous azeotrope. For this separation, a number of entrainers have been proposed, which are usually chosen to be immiscible with water and form a ternary minimum-boiling... 

---