1. Azeotropic Distillation CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard EdenDepartment of Chemical EngineeringAuburn University Lab Lecture No. 3 – Sequencing of Azeotropic Distillation Columns October 4, 2011 Contains Material Developed by Dr. Daniel R. Lewin, Technion, Israel

2. Introduction • When two or more components differ in boiling by less than approximately 50C and form a nonideal liquid solution, the relative volatility may be below 1.10. • Then ordinary distillation may be uneconomic, and if an azeotrope forms even impossible. • In that event, the following separation techniques, referred as enhanced distillation by Stichlmair, Fair, and Bravo, should be explored: • Extractive distillation • Salt distillation • Pressure-swing distillation • Homogeneous azeotropic distillation • Heterogeneous azeotropic distillation • Reactive distillation

3. Example 1 • Given that methyl acetate (1), which boils at 57.8C, methanol (2), which boils at 64.7C and n-hexane (3), which boils at 68.7C. • Sketch any boundaries across which the residue curves cannot traverse. • Sketch the residue curves for three feed compositions:

4. Example 1 • Note the existence of four azeotropes, where compositions are in mol %:

5. Example 1 – Solution • Plot pure components on vertices with Tb • Plot all azeotropes on diagram with Tb • Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures

6. Example 1 – Solution • Plot pure components on vertices with Tb • Plot all azeotropes on diagram with Tb • Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures • Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point Feed I

7. Example 1 – Solution • Plot pure components on vertices with Tb • Plot all azeotropes on diagram with Tb • Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures • Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point Feed III Feed I

8. Example 1 – Solution • Plot pure components on vertices with Tb • Plot all azeotropes on diagram with Tb • Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures • Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point Feed II Feed III Feed I

9. Example 1 – Solution • Plot pure components on vertices with Tb • Plot all azeotropes on diagram with Tb • Plot the residue curves connecting all azeotropes, azeotropes & vertices, and finally vertices & vertices with arrow heads pointing towards increasing boiling point temperatures • Plot additional residue curves that “arch” towards intermediate temperatures on the way to the end point

10. Example 2 • A stream consisting of a mixture of A, an organic component, and water, B, which forms an azeotrope. A separation process is to be designed to obtain pure products A and B. The plant manager suggests that you investigate the possibility of using component C as MSA.

11. Example 2 • Indicate the location of the azeotropes on a ternary diagram, as well as representative residue curves. • Suggest a process for the separation of A and B into pure products and show its operating lines on the ternary diagram. • Draw a PFD for your process. Indicate flow rates of all internal and external streams as multiples of the flow rate of F.

12. III, 330 K I, 350 K IV, 315 K C II, 360 K Example 2 – Solution 360 K 370 K 400 K

13. M1 F M2 B2 D1 M2 F S2 M1 S1 C B1 Example 2 – Solution S2 D2 D1 360 K S1 B2 B1 III, 330 K I, 350 K D2 IV, 315 K II, 360 K 370 K 400 K