Page 402 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

368 Production

(text continued from page 365)
Compressibility factors of many components are available as a function of
pressure in most handbooks [1,2]. In application of CSP to a mixture of gases,
pseudocritical temperature (TPJ and pressure (P,) are defined for use in place
of the true Tc and Pc to determine the compressibility factor for a mixture.

where subscript i = component in the gas mixture
yi = mole fraction of component "in in the gas mixture

For given values of Ppr and Tpr' compressibility factor Z can be determined
from Figure 6-1. If a gas mixture contains significant concentrations of carbon
dioxide and hydrogen sulfide, then corrected pseudocritical constants (T iC, P ic)
are defined as follows:

Tic = T, -e (6-6)

where

where ycq,yHps = mole fraction of CO, and H,S in mixture

Direct Calculation of 2 Factors

The Hall-Yarborough equation is one of the best:

0.06125Pprt e~p[-1.2(1- t)']
Z= (6-9)
Y

where: Ppr = the pseudoreduced pressure
t = the reciprocal, pseudoreduced temperature TpJT
y = the reduced density which can be obtained as the solution of the
equation

-0.06125P,texp[-1.2(1- t)'] + y + y2 + y3 - y4
(1 - YI3

-(14.76t -9.76t' +4.58t3)y'
+(90.7t -24.2tP+ 42.4tS)y(P.'8+2.82') (6-10)
= 0