Density Characteristics of the CO₂–CH₄ Binary System: Experimental Data at 313–353 K and 3–18 MPa and Modeling from the PC-SAFT EoS

Abstract

Accurate density data and a predictive equation of state (EoS) for the CO2–CH4 system are significantly important for the application of natural gas purification and carbon capture, utilization, and storage (CCUS). In this work, densities of the CO2–CH4 binary system with CO2 mole fractions ranging from 0.0998 to 0.8988 were measured at temperatures of 313–353 K and pressures of 3–18 MPa using a magnetic suspension balance, and the compressibility factors and the relative combined standard uncertainties were also calculated correspondingly. The PC-SAFT EoS was employed for the density modeling, and the PR EoS was used for comparison. The measured density data in this work and experimental density data from the literature were used to optimize the binary interaction parameter k ij in the PC-SAFT EoS and PR EoS. The predicting abilities of PC-SAFT and PR EoS with the optimized k ij were compared to the case without binary interaction (k ij = 0). The PC-SAFT EoS with the optimized k ij had better performance than the PR EoS with optimized k ij , and it could predict the density properties of the CO2–CH4 system accurately, with an average absolute deviation (AAD) of 1.16%. Modelings from PC-SAFT with and without the optimized k ij were then compared with the measured densities obtained in this work. The relative deviations for the calculation from PC-SAFT with the optimized k ij were within the range from −3.93 to 2.94%. Moreover, the CO2–CH4 binary systems with CO2 mole fractions of 0.7985 and 0.8988 in this work can be regarded as CO2-rich fluids, and their density reductions compared with pure CO2 were evaluated for the measured density data and the values calculated from the modified PC-SAFT.

Competitive sorption in CO2/CH4 separations: the case of HAB-6FDA polyimide and its TR derivative and a general analysis of its impact on the selectivity of glassy polymers at multicomponent conditions

“…Moreover, mixed-gas sorption calculations require the use of a binary interaction parameter for the gas pair. The value of the CO 2 /CH 4 binary interaction parameter was optimized by fitting the CO 2 /CH 4 pressure-volume-temperature-composition curves reported by Liu et al [108] to the Sanchez-Lacombe EoS. The details of the calculation are reported in the SI file.…”

Adaptive intermolecular interaction parameters for accurate Mixture Density Functional Theory calculations

“…Calculations of the isothermal properties of methane and carbon dioxide mixture in the gas phase [63] were made to check the mixing rules.…”

Density Characteristics of a Multicomponent CO2/N2/CH4 Ternary Mixture at Temperature of 293.15–353.15 K and Pressure of 0.5–18 MPa

“…In addition, the CO 2 /N 2 /CH 4 ternary system also plays an important role in many industrial processes, such as oil, natural gas, and coal-bed methane extraction. In recent years, scholars have conducted in-depth research on CO 2 injection to improve natural gas recovery, , and the use of CO 2 + N 2 mixture to displace shale gas and coal-bed methane has gradually emerged. , The variation of thermal physical properties such as density of mixed system plays an important role in describing displacement behavior and enhancing gas recovery . The density can be used to calculate some characteristics of fluids and develop certain equations of state .…”

“…The density can be used to calculate some characteristics of fluids and develop certain equations of state . There are many density data for CO 2 + N 2 , − CO 2 + CH 4 , ,,,− and N 2 + CH 4 , but the density data for CO 2 /N 2 /CH 4 are scarce. As shown in Figure , the density data of CO 2 /CH 4 , CO 2 /N 2 , and N 2 /CH 4 binary mixtures are relatively more but those of CO 2 /CH 4 /N 2 ternary mixture are scarce in the range of 250–450 K and 0–20 MPa.…”