Determination of thermodynamic properties of natural gas mixtures by direct and indirect methods

Abstract

Experimental temperatures and pressures were obtained using a Burnett-isochoric apparatus, and corresponding densitites derived for two mistures of carbon dioxide (1) and hydrogen sulfide (2); x1 = 0.7067, x2 = 0.2933 and x1 = 0.9045, x2 = 0.0955. The measurements spanned the supercritical, vapor, liquid and two-phase regions from 200 to 450 K and up to 23 MPa. Thermodynamic properties, UHAGS, also were derived from the PT data along with second and third virial coefficients. Phase boundary conditions were determined for each isochore that entered the two-phase region. At 10.34 MPa, enthalpy increments for pure n-heptane, pure methylcyclohexane, two n-heptane +methane mixtures, two methylcyclohexane +methane mixtures, one n-heptane +methane +methanol mixture and one methylcyclohexane + methane +methanol mixture were measured with a thermoelectric flow calorimeter from 180 K to 320 K. For each mixture, these measured enthalpy increments were combined with additional enthalpy information to calculate total enthalpy values relative to the pure fluids as edeal gases at 0 K.