# CBE_417

Mechanics

Oct 27, 2013 (4 years and 6 months ago)

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CBE 417

“Unit Operations”

1

Lecture: 5

12 Sep 2012

Overview

2

Brief thermodynamics review

Binary flash with energy balance

Multicomponent flash

Separation Factor (
eqn

1
-
4;

et.al.)

Relative Volatility (
eqn

2
-
21;

et.al.)

Other Equilibrium Diagrams:

3

P = 1.013 bar

T = various
o
C

Benzene
-

Toluene

T
vs

X or Temp
vs

Composition

Y
vs

X diagram

Other Equilibrium Diagrams:

4

Y
vs

X
Diagram
(LLE)

5

Effect of Pressure:

6

Effect of Pressure:

7

& Henley (2006)

Other Equilibrium Diagrams:

8

CBE 417

“Chemical Engineering Equilibrium
Separations”

9

Lecture: 6

14 Sep 2012

Overview

10

Brief thermodynamics review

Binary Flash with material balance and energy balance

Sequential solution

Simultaneous solution

Multicomponent

Flash

Binary Flash

11

Overall mole balance

mole balance on
a

mole balance on
b

equilibrium
eqn

for
a

mole balance on
a

Binary Flash

12

Flash separation:

Specify:

Find:

a

= n
-
pentane

b

= n
-
hexane

Vfrac

0.471

V/F

P

3.000

bar

functi
on

-
1.89E
-
08

Xa

0.394

Xb

0.606

Ya

0.619

Yb

0.381

Binary Flash

13

Overall mole balance

mole balance on
a

mole balance on
b

equilibrium
eqn

for
a

mole balance on
a

Binary Flash

14

Flash separation:

Specify:

Find:

a

= n
-
pentane

b

= n
-
hexane

Binary Flash

15

Graphical Solution:

mole balance on
a

solve for
y
a

“Operating Line”

Binary Flash

16

Graphical:

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Y a

X a

y = x

Equilibrium curve

Za

Solution!

What if
f

is unknown, but T
is known?

Limits:

f

= 0

f

= 1

Binary Flash Energy Balance

17

EB on CV:

Other Equilibrium Diagrams:

18

Alternative Thermodynamics

19

Older (hand methods):

Relative Volatility (VLE):

Raoult’s

law

Aside (couple with MB)

Separation Factor or Relative Volatility

20

Effect of Pressure:

21

& Henley (2006)

Constant Relative Volatility?

22

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
0.2
0.4
0.6
0.8
1
Y MeOH

X MeOH

Alternative Thermodynamics

23

K
i

with
multicomponent

flash:

Sequential solution: suggestions p 35
-
37 (
Rachford
-
Rice
Eqn
)

Simultaneous solution technique: suggestions p 40
-
43

Into MB:

Sizing Flash Drums

24

Simulators

25

Flash input:

Sensitivity Analysis:

Design Spec:

Questions?

26