Avoiding the use of critical constants in cubic equations of state

✍ Scribed by Giorgio S. Soave; Alberto Bertucco; Michele Sponchiado

• Publisher: American Institute of Chemical Engineers
• Year: 1995
• Tongue: English
• Weight: 604 KB
• Volume: 41
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690410813

✦ Synopsis

A new way to define the two parameters a, b of the Redlich-Kwong equation of state without using the critical constants is introduced. First, the "shifed"covo1ume (bc) of the Peneloux modification of the equation of state is estimated by group contributions (for a wide range of compounds); from it and one vapor pressure-liquid density pair, the covolume b is then determined. The attractive parameter a is derived, at any temperature, from the covolume and the compound vapor pressure. The proposed method makes it possible to treat substances whose critical constants are not known (hea y or thermally unstable compounds) by using one density value and the vapor pressure curve. Examples are given of vapor-liquid equilibrium calculations.