CBE_417

flinkexistenceMechanics

Oct 27, 2013 (4 years and 16 days 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;
Seader

et.al.)

Relative Volatility (
eqn

2
-
21;
Seader

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


Seader

& 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


Seader

& 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