Gas-liquid equilibria calculations

We will discuss equilibrium-ratio correlations in some detail later. First, however, we will look at their use in gas-liquid equilibria calculations. 

Chapter 12 gives the equations for nonideal gas-liquid equilibria calculations. The quantities of gas and liquid leaving the separator on a basis of lb moles per lb mole of separator feed will be designated as ngl and nu. See Figure 13-2. 

Volatile oils and retrograde gases are produced routinely through at least three stages of separation. Thus, the calculation procedure requires three gas-liquid equilibria calculations. The equations for producing gasoil ratios are... 

Gas-liquid equilibria calculations have been made for a two-stage separator system as shown in Figure 13-2,... 

The gas-liquid equilibria calculations for a two-stage separation of a black oil have been completed. Results are given below. 

The equations for gas-liquid equilibria calculations and the definition of equilibrium ratio (K-factor) were discussed in Chapter 12. This chapter will examine K-factor coirelations. 

Gas liquid equilibria calculations at 1500 psia and 160°F have been completed for a black oil. Resulting compositions are given below. A convergence pressure of 5000 psia was used to obtain K-factors. What convergence pressure should have been used for this mixture at 160°F ... 

Gas-Liquid Equilibria Calculations With Equations of State... 

This chapter is an introduction to utilizing equations of state in gas-liquid equilibria calculations. It conveys a general understanding of the subject and is as simple and short as possible. Many of the complexities of this subject are not discussed. Thus, the study of this chapter will not result in the ability to apply equations of state to complex petroleum mixtures. 

The application here of the Peng-Robinson equation of state does not mean that it is the best equation of state. This equation was merely selected to illustrate the application of a typical three-constant, cubic equation of state to gas-liquid equilibria calculations. 

A first trial set of K-factors is obtained. For instance, the K-factor equation given in Appendix B can be applied to get the first trial set of K-factors. These are used in a gas-liquid equilibria calculation, as described in Chapter 12, to determine the compositions of the gas and liquid. The remaining equations are solved twice, once for the liquid and once for the gas. 

Chapter 4 does not address all available equations of state. It merely shows the history of the art of developing equations of state. Chapter 14 is a very simple introduction into K-factor correlations. Chapter 15 only introduces the topic of equation-of-state gas-liquid equilibria calculations. The underlying theory of the calculations is illustrated however, none of the difficulties of application to petroleums nor any of the sophisticated techniques of solving the equations is addressed. 

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