Chapter 12

# Chapter 12 - CHAPTER12 GasLiquidEquilibria Liquids Given a...

This preview shows pages 1–9. Sign up to view the full content.

CHAPTER 12  Gas-Liquid Equilibria Gas-Liquid Equilibria Simulation of Flash Vaporization for Nonideal  Liquids: Given: a. Total composition of mixture (z) b.Total moles of mixture (n) c. Pressure (P) d.Temperature (T) Calculate: 1. How many phases are present. 2. Amount of gas present if P and T are such  that the mixture exists in  the 2-phase  region (n g m g ). 3. Amount of liauid present if P and T are such  that the mixture exists in the 2-phase region  (n L m L ). 4. Liquid composition (x) 12 - 1

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
5. Gas composition (y) 6. Bubble point pressure of mixture at T (P b ) 7. Dew point pressure of mixture at T (P d ) 12 - 2
12 - 3

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Flash Calculation Equations If two phases are present, the liquid and gas  compostions must sum to one: = = = N i i i x 1 1 (1) = = = N i i i y 1 1 (2) where N is the total number of components in the  mixture.  A material balance on the total mixture gives n n n L g = + (3) A material balance on the ith component in the  mixture gives                                                        i i L i g nz x n y n = + (4)   12 - 4
Flash Calculation Equations  Continued For gas-liquid equilibrium, i i i x y k = (5) where   k i   is   an   experimentally   determined  equilibrium ratio for component i in the mixture.   The   equilibrium   ratio,   which   is   a   function   of  pressure,   temperature   and   composition   of   the  mixture, may be obtained from correlations such  as those shown in Figures A-1 to A-14 of McCain. Substituting   for   y i   In   Eq.(4),   using   Eq.(5),   and  solving for x one obtains i g L i i k n n n n z x + = (6) 12 - 5

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Flash Calculation Equations  Continued Let n n n g g = (7) and n n n L L = (8) Substituting Eqs. (3), (7) and (8) into (6) gives                                           ) 1 ( 1 - + = i g i i k n z x (9) Substituting Eq. (9) into (1) gives the condition for  equilibrium as        1 ) 1 ( 1 1 1 = - + = = = = = N i i i g i N i i i k n z x (10) 12 - 6
Flash Calculation Equations  Continued It can be shown that elimination of x i  from Eqs. (4)  and   (5)   would   have   resulted   in   the   following  equations for y i  and the condition for equilibrium:                                           - + = 1 1 1 i L i i k n z y (11)        1 1 1 1 1 1 = - + = = = = = N i i i L i N i i i k n z y (12) 12 - 7

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Flash Calculation Equations  Continued At the bubble point pressure,  n L  = 1, and Eq. (12)  becomes 1 1 = = = N i i i i k z (13) At the dew point pressure,   n g   = 1, and Eq. (10)  becomes 1 1 = = = N i i i i k z (14) 12 - 8
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 12/14/2011 for the course PGE 312 taught by Professor Peters during the Spring '08 term at University of Texas.

### Page1 / 67

Chapter 12 - CHAPTER12 GasLiquidEquilibria Liquids Given a...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online