1. CBE 417
“Unit Operations”
Lecture: 5
12 Sep 2012

2. Overview Brief thermodynamics review Binary flash with energy balance
Multicomponent flash
Separation Factor (eqn 1-4; Seader et.al.)
Relative Volatility (eqn 2-21; Seader et.al.)

3. Other Equilibrium Diagrams:
P = bar
T = various oC
Benzene - Toluene
Y vs X diagram
T vs X or Temp vs Composition

4. Other Equilibrium Diagrams:

5. Y vs X Diagram (LLE)

6. Effect of Pressure:

7. Effect of Pressure:
Seader & Henley (2006)

8. Other Equilibrium Diagrams:

9. Overview Brief thermodynamics review Binary Flash with energy balance
Sequential solution
Simultaneous solution
Multicomponent Flash

10. Binary Flash Overall mole balance mole balance on a mole balance on b
equilibrium eqn for a
mole balance on a

11. Binary Flash Flash separation: Specify: Find: a = n-pentane
b = n-hexane
Vfrac
0.471
V/F P
3.000
bar
function
-1.89E-08 Xa
0.394 Xb
0.606 Ya
0.619 Yb
0.381

12. Binary Flash Overall mole balance mole balance on a mole balance on b
equilibrium eqn for a
mole balance on a

13. Binary Flash Flash separation: Specify: Find: a = n-pentane
b = n-hexane

14. Binary Flash Graphical Solution: mole balance on a solve for ya
“Operating Line”

15. Binary Flash Graphical: Solution!
Equilibrium curve
y = x
Solution!
What if f is unknown, but T is known? Za
Limits:
f = 0
f = 1

16. Binary Flash Energy Balance
EB on CV:

17. Other Equilibrium Diagrams:

18. Alternative Thermodynamics
Older (hand methods):
Raoult’s law
Relative Volatility (VLE):
Aside (couple with MB)

19. Separation Factor or Relative Volatility

20. Effect of Pressure:
Seader & Henley (2006)

21. Constant Relative Volatility?

22. Alternative Thermodynamics
Ki with multicomponent flash:
Into MB:
Sequential solution: suggestions p (Rachford-Rice Eqn)
Simultaneous solution technique: suggestions p 40-43

23. Sizing Flash Drums

24. Simulators
Flash input:
Sensitivity Analysis:
Design Spec:

25. Questions?