Simplified GERG Virial Equation for Field Use

Abstract

A GERG (Groupe EurQpeen de Recherches Gazieres) equation of state (EOS) is presented to calculate the compressibility factor of natural gases. The equation, which does not require detailed gas analysis, can predict the compressibility factor when three of the four following gas properties are known: the gross calorific value, the relative density, and the mole fractions of N 2 and CO 2 , The new equation, known as the SGERG-88 vi rial equation, is based on ideas presented in an earlier study. The new equation, however, applies to wider ranges oftemperature and pressure and can be applied to gases containing hydrogen if the mole fraction of the hydrogen is known. The equation was tested on natural gases purchased, transported, and marketed by the European gas companies. Excellent agreement between computed and experimental compressibility factors was found. This difference is, in most cases (94 % of the data points), less than 0.1 % in the temperature range of 265 to 335 K and for pressures up to 12 MPa.

Excess and unlike-Interaction second virial coefficients and excess molar enthalpy of (0.500CO + 0.500CO2)

“…Jaeschke et al (7) (referred to as the GERG group) have reviewed the published measurements on carbon dioxide and concluded that the studies of Michels and Michels (8) and of Michels et al (9) represented the most reliable and extensive measurements. Brugge et al (10) compared their two more recent measurements (at 300 K and 320 K) with earlier work and demonstrated excellent agreement with Michels and Michels.…”

“…(8) Jaeschke et al (7) reviewed the reported measurements for CO 2 and generated the best-fit equation:…”

“…Jaeschke et al (7) who also briefly reviewed the reported experimental measurements, concluded that the 1952 measurements of Michels et al (9) were the best available and so they generated a fitting equation for those results. In this temperature range their equation is in excellent agreement with the Goodwin equation which has the form: (7) and so we have employed the Goodwin equation to generate the B(CO) values needed for B 12 estimation.…”

Cross second virial coefficients and dilute gas transport properties of the (CH 4 + CO 2 ), (CH 4 + H 2 S), and (H 2 S + CO 2 ) systems from accurate intermolecular potential energy surfaces

“…In figure 3, the calculated values for the cross second virial coefficient of the CH 4 -CO 2 molecule pair are compared with selected experimental data [47][48][49][50][51][52][53][54][55][56] and with the correlation of Dymond et al [57]. The data of Ng [48] were taken from reference [57].…”

“…The error bars shown in the figure correspond to those given by the authors except for the reanalyzed data of Martin et al, for which we also reanalyzed the uncertainty. We used the reanalyzed data of Martin et al [51] as well as the data of Jaeschke et al [52] and of Iglesias-Silva et al [57] for temperatures from (220 to 400) K exhibits large negative deviations at low temperatures, reaching −14.5 cm 3 · mol −1 at 220 K. Nevertheless, the correlation is consistent with the calculated values within the expanded (k = 2) uncertainty estimates of Dymond et al [57].…”