A modified Zudkevitch and Joffe method of determining parameters of an equation of state (EOS) is described and applied to the Patel and Teja (PT) equation. All the parameters of the PT equation are considered temperature dependent and evaluated from the vapour pressure, liquid molar volume and critical compressibility factor of pure compounds. The attraction term in the PT equation is modified by a temperature dependent parameter for super critical components. Conventional random mixing rules are applied to obtain the EOS parameters for mixtures, with no binary interaction coefficients for hydrocarbon mixtures.

The modified equation was validated against experimental data of gas condensate systems and compared with other leading EOS. A large number of data, including the dew point pressure, condensate drop-out, and the density of gas and condensate phases at equilibrium conditions over a wide temperature range was generated and used in this validation. The proposed method predicted the experimental data, particularly the retrograde condensate volume, more accurately than others. The method can be applied to any equation of state.

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