Accurate Prediction of Compressibility Factors by the GERG Virial Equation

Abstract

Summary The European Gas Research Group (GERG, Groupe Européen de Recherches Gazières) performed an extensive research project involving the measurement of compressibility factors of pure gases and binary mixtures and of natural gases in the temperature range of 265 to 335 K and at pressures up to 12 MPa. These pure gas and binary mixture data, together with high-quality data from the literature, were used to develop the GERG virial equation for the accurate prediction of the compressibility factor of natural gas (multicomponent) mixtures. Pressure, temperature, and a 13-component composition are used as input data. Eighty-four sets of experimental natural gas data made up of more than 4, 000 data points were used to validate the GERG virial equation of state (EOS). The target accuracy of the GERG virial equation is ±0.1 %. A comparison of experimental and predicted compressibility factors shows that this target was achieved. The average root-mean-square (RMS) error for the differences between the experimental and the predicted compressibility factors is 0.06% for pressures up to 12 MPa. Even in the high-pressure range between 8 and 12 MPa, the RMS error is only 0.07%.