Experimental density and an improved Helmholtz-energy-explicit mixture model for (CO2 + CO)

Abstract

This study reports new density measurements of the (CO2 + CO) system at temperatures from (283 to 373) K and pressures up to 48 MPa for four different mixtures, with compositions ranging from (5 to 50) mol% CO. A commercial vibrating-tube densimeter was used to measure the density of each mixture as a function of pressure and temperature. Temperature and pressure were measured with expanded uncertainties (k = 2) of 0.05 K and 0.035 MPa, respectively. The relative combined expanded uncertainty (k = 2) of the density was estimated to be between (0.2 and 1.8) %, with values ≤ 1 % for most state points. The new data significantly expand the pressure and composition ranges of the available density data for the (CO2 + CO) system. Together with recently published vapourliquid-equilibrium data, the new data enabled the development of an improved Helmholtz-energyexplicit mixture model. The new model is based on the mathematical approach of the GERG-2008 and EOS-CG models with new adjustable parameters. As a result, the new mixture model allows for a significantly more accurate description of the thermodynamic properties of the (CO2 + CO) system than GERG-2008 and EOS-CG. A detailed comparison among our density data, experimental data from the literature and the different mixture models is presented.

Vapour-liquid equilibrium data for the carbon dioxide (CO2) + carbon monoxide (CO) system

“…To improve the calculation of the vapour pressure of carbon dioxide, the Mathias-Copeman (MC) alpha function [28] with three adjustable parameters was also used for this compound : Approximation equations of state. In the work, the original GERG-EoS [13], EoS-CG [14] and EoS-CG with the departure function proposed by Souza et al [29] were also used.…”

Accurate experimental (p, ρ, T) data of the (CO2 + O2) binary system for the development of models for CCS processes

“…The range of validity of this model is for pressures up to 16 MPa and temperatures between 273 K and the critical temperature of CO2. A recent research work [5] has proposed a specific model for the binary mixture (CO2 + CO). Gernert and Span proposed an equation of state for the calculation of thermodynamic properties of humid gases, combustion gases, and CO2-rich mixtures typical in CCS processes, the so-called EOS-CG (Equation of State for Combustion Gases and Combustion Gas-like Mixtures) [6].…”

Density and Phase Behavior of the CO2 + Methylbenzene System in Wide Ranges of Temperatures and Pressures

“…In contrast, multifluid Helmholtz Equations of State (MFHEOS), especially the GERG-2008 EOS of Kunz and Wagner, are able to represent accurately phase-equilibria, density and derivative properties provided that the model is fully parameterised against extensive experimental data. 13,14 The GERG-2008 model was developed for natural gas and similar mixtures containing up to 21 components, including CO2, normal alkanes up to C10 and several other components.…”

“…Although, in many cases, CEOS can describe phase equilibria quite accurately, they are often quite inaccurate for density and derivative properties, such as heat capacity and sound speed. In contrast, multifluid Helmholtz equations of state (MFHEOS), especially the GERG-2008 EOS of Kunz and Wagner, are able to represent phase-equilibria, density, and derivative properties accurately, provided that the model is fully parametrized against extensive experimental data. , The GERG-2008 model was developed for natural gas and similar mixtures containing up to 21 components, including CO 2 , normal alkanes up to C 10 , and several other components. Therefore, the capabilities of this model to describe the properties for CO 2 –hydrocarbon systems are of interest. − Recently, we have measured phase behavior, compressed-fluid densities, and saturated-phase densities for the binary system (CO 2 + n -heptane) at temperatures from 283 K to 473 K, with pressures up to 68 MPa.…”