Measurement and Modeling the Properties and Equilibrium of Fluid Systems Involving Carbon Dioxide and Hydrocarbons
Keywords:binary fluid systems, carbon dioxide and n-alkanes, pVT properties, thermodynamic parameters, MD modeling, diffusion coefficient, equilibrium
On the basis of molecular dynamics modeling (MD modeling) and experimental data pVTx, a study was made of the dynamic and thermodynamic properties of a binary system based on light gases containing heavy oil (A-B). The solvent (A) used was carbon dioxide and n-alkanes (methane, ethane, and propane) in the supercritical fluid (SCF) state. Measurements of the pVTx properties were carried out in the temperature, density, and pressure ranges near the critical parameters of the light gas-heavy oil systems. Based on pVTx data and MD modeling in the A-B system, the diffusion coefficient (D) was determined near the critical parameters of the solvent. The values of D in the binary system SCF carbon dioxide or alkanes containing (methane, ethane and propane) heavy oil from the Siyazan field of Azerbaijan are calculated. The D SCF value of methane and ethane in the A-B system is higher than in a system containing SCF propane at given concentrations (c or x) of heavy oil and temperature. The value of D SCF of light gases in the A-B system increases with an increase in the concentration of heavy oil up to x = 2.5 wt. %. Diffusing molecules of SCF gases reduce the viscosity of heavy oil in the A-B system. Dependence D = f(c) tends to have an asymptotic value with increasing oil concentration. In the A-B system, the dependence of D SCF gases on pressure has a non-monotonic form. To calculate mixtures of light gases, the modified Peng-Robinson equation of state (PR EOS) was used. The isothermal dependence P-x of the carbon dioxide-methane binary system is approximated. The calculated P-x curves are consistent with the experimental ones in the temperature range 277-345 K.