High accuracy compressibility factor calculation for natural gases and similar mixtures by use of a truncated virial equation

Abstract

This monograph provides a detailed account of the concept, development, performance and use of the GERG virial equation. This equation predicts the compressibility factor Z(p, T) for natural gas-type mixtures (specified by a 13-component molar composition) within the respective pressure and temperature ranges of 0 to 12 MPa (0 to 120 bar) and 265 to 335 K (-8 to 62/sup 0/C) with an expectation accuracy of 0.1%. Coefficients used in the GERG virial equation have been correlated using a databank of over 13,00 high quality compressibility factor experimental measurements. The GERG equation describes a subset of some 4,500 data points for natural gases, which were not used in the correlation development, with a root-mean-square error of 0.055%. Evidence is given that performance is better than that of the GRI-SuperZ (AGA8) equation within the stated range of applicability. Numerical values for all coefficients needed to implement the equation are given, and computer program listings are provided. A simplified version of the GERG virial equation, requiring less comprehensive analytical input data, will be described elsewhere. The GERG virial equation was developed at the van der Waals Laboratory of the University of Amsterdam, under contract to, and with specific guidance from, the Groupe Europeen de Recherches Gazieres. (orig.) With 33 figs., 35 tabs.