Two constant equation of state

Two-constant equation of state phase behavior calculations for aqueous mixtures often require the use of temperature dependent binary interaction parameters. The methods used for evaluating these parameters for some of the typical aqueous binary pairs found in coal gasification and related process streams are described. Experimental and predicted phase compositions based on these methods are illustrated for aqueous pairs containing CO2. H2S, NH3, and other gases. 

Equations like the van der Waals equation often are called two-constant equations of state, although there are actually three constants a, b, and R. These equations also are called cubic equations of state. The van der Waals equation in cubic form is... 

Fig. 15-1. Vatues of molar volume calculated with a two-constant equation of state.

Fig. 15-2. Values of molar volume and chemical potential at a temperature below critical temperature calculated with a two-constant equation of state showing the "van der Waafs loop. ...

Dixon DJ, Johnston KP, Bodmeier RA. Polymeric materials formed by precipitation with a compressed fluid antisolvent. AIChE J 1993 39(1) 127-139. Peng DY, Robinson DB. A new two-constant equation of state. Ind Eng Chem Fundam 1976 15 59. 

Peng DY, Robinson DB. A new two-constants equation of state. Ind Eng Chem Fundam 1976 15 59-63. 

Peng, D. Y. and D. B. Robinson. 1976. A new two-constant equation of state. Industrial and Engineering Chemistry Fundamentals. 15, 59. 

Reservoir-fluids phase behavior and volumetric properties. Reservoir fluids are a complex mixture of thousands of components that exhibit very complex phase behavior. It is, however, surprising that a simple two-constant equation of state such as the PR-EOS can do an excellent job for vapor-liquid equilibria calculations away from the critical region. A discussion of the manner in which the calculations are performed is presented. 

Michelsen, M.L, and R.A. Heidemann Calculation of Critical Points from Cubic Two-Constant Equations of State, AIChEJ., vol. 27, p. 621,1981. 

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