Page 116 - Petroleum and Gas Field Processing

Solution
(i) The average molecular weight of the well stream, M av , is 39.92.
M is determined next:

M ¼ Molecular weight of air M av
¼ 28:96=39:92
Because M is greater than 1.0, Eq. (27a) is applied.
To find the value of A, go to Figure 24. Using Z ¼ 0.7 and
M ¼ 1.38, A is found to be ¼ 0.421. Substituting the values of
A and P 1 in Eq. (27a), the most favorable operating pressure
(P 2 ) o is calculated and found to be 50 psia.
(ii) Direct substitution of the values of P 1 ¼ 500 psia and P 3 ¼ 14.7
psia in Eq. (28) yields (P 2 ) o ¼ 85.5 psia

Equilibrium Flash Vaporization Calculation
Equations describing flash vaporization, as given in Section 3.8, can be
applied to calculate the value of optimum operating pressure for the
second-stage separator for a three-stage GOSP. An outline of a trial-and-
error calculation procedure is presented in Figure 25.

Figure 25 An outline of a proposed procedure for computing (P 2 ) o for a three-
stage GOSP where P 1 and P 3 are fixed.

Copyright 2003 by Marcel Dekker, Inc. All Rights Reserved.