PVT Measurements of the H₂–CO₂–CH₄–CO–H₂O System at 740–939 K and 18.1–34.7 MPa with an Isochoric Apparatus and the Development of a Virial Equation of State

Abstract

Modeling the pVT properties of hydrogen mixtures at high temperatures is significant for the development of relevant production and utility systems. In this work, pVT measurements are reported for the H2–CO2–CH4–CO–H2O system at 740–939 K and 18.1–34.7 MPa with an isochoric apparatus. The expanded relative uncertainty (k = 2) of density is less than 0.015. Based on the present and previous pVT data, a virial equation of state (EOS) has been developed at 720–939 K and up to 35 MPa for the quinary system with relative uncertainty (k = 2) at density less than 0.015. The thermal pressure coefficient of the quinary system was calculated from the virial EOS and the comparison with the experimental values indicated that changes in the specific volume and composition of the quinary system existed in each set of measurements. Isochoric heat capacity of the quinary system was also calculated and was compared with the GERG-2008 EOS. The calculated isochoric heat capacities agree with the GERG-2008 EOS within 1.75% above 873 K and up to 35 MPa, while at lower temperatures, the deviations become larger (up to 3.66%).

A Review of Experimental Researches on the Thermophysical Properties of Hydrogen-Containing Mixtures at High Temperatures and High Pressures

“…The ARD of the experimental density value of the H 2 −CO 2 −CH 4 −CO−H 2 O system from that calculated using the virial EOS 25 does not exceed 1.39%. The uncertainty (k = 2) of the virial EOS 25 The comparison between the thermal pressure coefficient for the H 2 −CO 2 −CH 4 −CO−H 2 O system calculated using the virial EOS 25 and the GERG-2008 EOS 19 and the experimental value is shown in Figure 7. For the H 2 −CO 2 mixture measured using the isochoric method, the difference between the calculated thermal pressure coefficients using any p−T state as the characteristic pressure and temperature is smaller than 0.2%.…”

“…The densities of the H 2 −CO 2 −CH 4 −CO−H 2 O system calculated using the virial EOS developed by Cheng et al 25 and the GERG-2008 EOS 19 are compared with the experimental data in Figure 6. The ARD of the experimental density value of the H 2 −CO 2 −CH 4 −CO−H 2 O system from that calculated using the virial EOS 25 does not exceed 1.39%. The uncertainty (k = 2) of the virial EOS 25 The comparison between the thermal pressure coefficient for the H 2 −CO 2 −CH 4 −CO−H 2 O system calculated using the virial EOS 25 and the GERG-2008 EOS 19 and the experimental value is shown in Figure 7.…”

“…The trend of the thermal pressure coefficients for the quinary hydrogen-containing system calculated using the GERG-2008 EOS 19 is in accordance with those calculated using the virial EOS. 25 There is much difficulty in directly measuring the derived properties such as the heat capacity and speed of sound at high temperatures and high pressures, and they are often calculated from the EOSs. 49 The isobaric heat capacity and speed of sound could be calculated based on the isochoric heat capacity, so the calculation of the isochoric heat capacity is significant for checking the reliability of the EOS.…”

“…19 The second term on the right side of eq 55 is the contribution of the deviation from the ideal-gas property and is calculated using the virial EOS. 25 The isochoric heat capacity of the H 2 −CO 2 −CH 4 −CO− H 2 O mixtures of three compositions [the mole fraction of hydrogen x(H 2 ) = 0.239, 0.162, and 0.050, respectively] at 720−960 K and 15−35 MPa are calculated. The isochoric heat capacities calculated using the virial EOS 25 and the GERG-2008 EOS 19 which also has the potential of calculating the thermophysical properties of the hydrogen-containing mixtures at high temperatures and high pressures are compared in Figure 8.…”

“…25 The isochoric heat capacity of the H 2 −CO 2 −CH 4 −CO− H 2 O mixtures of three compositions [the mole fraction of hydrogen x(H 2 ) = 0.239, 0.162, and 0.050, respectively] at 720−960 K and 15−35 MPa are calculated. The isochoric heat capacities calculated using the virial EOS 25 and the GERG-2008 EOS 19 which also has the potential of calculating the thermophysical properties of the hydrogen-containing mixtures at high temperatures and high pressures are compared in Figure 8. The deviation of the value of the isochoric heat capacity calculated using the GERG-2008 EOS 19 from that calculated using the virial EOS 25 is less than 3.66% in the temperature, pressure, and composition ranges of the calculations.…”