An effective modification of the Benedict-Webb-Rubin equation of state

A modification of the BWR equation of state is proposed, which is a simplified form of a previously proposed one. It applies to systems formed by hydrocarbons and related compounds, with particular attention to the critical conditions. The range of treatable compounds was extended to a value 0.9 of the acentric factor, corresponding to C-20 hydrocarbons. The critical compressibility factor Z(c) was made independent of the acentric factor, for a more accurate prediction of pure-component properties (the previous equation did not give the same improvement). Mixing rules require one binary interaction constant for each component pair. Zero binary constants can be used for methane-alkane and alkane-alkane pairs. Examples of applications to pure hydrocarbons and their mixtures are given. (C) 1999 Elsevier Science B.V. All rights reserved.