### ITK-234 Slide 3 - Modified Raoult - Dicky Dermawan

```ITK-234 Termodinamika Teknik Kimia II
VLE Calculations for
Nonideal Mixtures
Dicky Dermawan
www.dickydermawan.net78.net
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Modified Raoult’s Law
K-value Method
VLE using Equation of States
Dicky Dermawan
Incorporation of fugacity and activity
coefficient to vle criteria results:
y k   k  P  x k   k  Pk



sat  
Vk  P  Pk


where  k 
 exp 


R T
ˆ k sat


However, at low pressure (up to at least 1 bar):
ˆ k
sat
ˆ
ˆ
k  k
1
The Poynting Factor 1
Modified Raoult’s Law:
y k  P  x k   k  Pk
sat
sat
Modified Raoult’s Law:
Wilson Equation for calculating 
a.
b.
Prepare a P-x-y diagram at 80oC
Prepare a t-x-y diagram at 101,33 kPa
Modified Raoult’s Law:
Wilson Equation for calculating  (Cont’)
Use your diagram to answer there questions:
Given P = 70 kPa, T = 80oC & overall composition,
z1=30%
Find the fraction of system which is liquid (L) & vapor
(V) and their respective compositions xi & yi
Modified Raoult’s Law:
Wilson Equation for calculating 
a.
b.
Prepare a P-x-y diagram at 80oC
Prepare a t-x-y diagram at 101,33 kPa
Modified Raoult’s Law:
Wilson Equation for calculating  (Cont’)
Use your diagram to answer there questions:
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
Wilson Equation for calculating 
Modified Raoult’s Law:
NRTL Equation for calculating 
a.
b.
Prepare a P-x-y diagram at 80oC
Prepare a t-x-y diagram at 101,33 kPa
Modified Raoult’s Law:
NRTL Equation for calculating 
VLE Calculation Using No Diagram
Answer the questions (a) through (e)
from
12.6 to 12.13 but don’t use the phase
diagram to obtain the answers
Estimating Azeotrophic Condition,
Use No Diagram
K-Value Method:
Using De Priester Charts for light hidrocarbons
yk  k  P  x k   k  Pk

sat

sat
V

P

P
k
k 
 exp  k

R T
ˆ k sat

ˆ k


y k  k  Pk sat
Kk 

 f ( T, P )
xk
k  P


yi  K i  x i
The nomographs K = f(T,P) prepared by De Priester provide
easy application of this approach to practical problem
K-Value Method:
Using De Priester
Charts for light
hidrocarbons
High
Temperature
Range
K-Value Method:
Using De Priester
Charts for light
hidrocarbons
Low
Temperature
Range
Type of Phase Equilibria
Calculations
BUBL P calculation:
Given T & liquid composition xi,
Find the bubble point Pb & vapor
composition
Assume P, find Ki satisfying:
DEW P calculation:
Given T & vapor composition yi,
Find the bubble point Pb & vapor
composition
 Ki  x i  0
Assume P, find Ki satisfying:

yi
0
Ki
Type of Phase Equilibria
Calculations
BUBL t calculation:
Given P & liquid composition xi,
Find the bubble point Pb & vapor
composition
Assume t, find Ki satisfying:
DEW t calculation:
Given P & vapor composition yi,
Find the bubble point Pb & vapor
composition
 Ki  x i  0
Assume t, find Ki satisfying:

yi
0
Ki
K-Value Method:
Using De Priester Charts for light hidrocarbons
K-Value Method:
Using De Priester Charts for light hidrocarbons
Type of Phase Equilibria Calculations
FLASH calculation:
Given P, T & overall composition,
Find the fraction of system which is liquid (L) & vapor (V)
and their respective compositions xi & yi
Make sure P located between Pb dan Pd, i.e.
Perform BUBL P for zi =xi and
Perform DEW P for zi = yi
Find Ki ; assume V satisfying:

zi
xi 
1
1  K i  1  V
or:

yi 
or: The General Solution Procedure
zi  K i
1
1  K i  1  V

z i  (K i  1)
0
1  K i  1  V
K-Value Method:
Using De Priester Charts for light hidrocarbons
K-Value Method:
Using De Priester Charts for light hidrocarbons
K-Value Method:
Using De Priester Charts for light hidrocarbons
```