### 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
[email protected]
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’)
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’)
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
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
```