A Systematic Study of Cubic Equations of State with van der Waals Mixing Rules and Different Combining Rules in Predicting the Densities of LNG and Natural Gas Model Systems

Abstract

Cubic equations (EoSs) of state are successfully used in petroleum and natural gas industry. In order to extend these equations to mixtures, van der Waals mixing rules with Lorentz-Berthelot (LB) combining rules are often employed; however, the accuracies of these EoSs in predicting the liquid densities of hydrocarbon mixtures are not adequate. The main objective of this study was comparing 13 EoSs coupled with 10 combining rules in predicting the densities of hydrocarbon mixtures. Binary and ternary liquid mixtures, LNG mixtures and synthetic natural gas mixtures comprising 752 data points were collected and used in this study. Results revealed that for predicting the liquid densities of binary and ternary mixtures, the Schmidt and Wenzel (SW) EoS coupled with Hudson-McCoubrey (HMC) or LB combining rules are the best among the others. The SW EoS coupled with the LB combining rules were also the best in predicting the densities of the LNG mixtures. Additionally, the LB combining rules are the best in predicting natural gas mixtures densities using the Patel and Teja (PT), SW and Patel-Teja-Valderrama (PTV) EoSs. In general, it was found that the Redlich-Kwong (RK) family EoSs, SW and Trebble-Bishnoi-Salim (TBS) EoSs are best coupled with the LB combining rules. However, the Peng and Robinson (PR) family EoSs with Halgren (HHG) combining rules were in better agreement with experimental data. The Waldman-Hagler (WH) combining rules lacked predictability when coupled with the most EoSs.

Molecular dynamics simulation of corrosion and its inhibition: comparison of structural stability of Fe/FeNi/FeNiCr/FeNiCrTi steels under high-temperature liquid lead

“…Depending on the research goal, the specific potential is used to describe the phenomena accurately. For our corrosion study of the metal system (FeNiCrTi-PbO), for easy calculation, let's use the Lennard-Jones (LJ 12-6), which is the very popular one that is also used by other researchers [15]. This LJ potential may not be so accurate for the metal system.…”

“…Then there is the Pb_123x124x125.xyz file. As mentioned above, specification data of material and the potential parameters of different elements were computed by using the Lorentz-Bertholet mixing formula [15]. Then, all simulations of the corrosion and inhibition investigation will be done by controlling the Moldy simulation as the control file below.…”

Comparative analysis of the performance of mixing rules for density prediction of simple chemical mixtures

“…Researchers have used various mixing rules to employ EOS in predicting various thermodynamic properties of chemical mixtures (Al-Manthari et al, 2019). The prediction accuracy of EOS varies with the properties being predicted and the system conditions.…”

“…(Nasrifar and Bolland, 2006). Still, in pursuit of higher accuracy, coupling of two or more EOS using coupling rules has come into focus in recent times (Al-Manthari et al, 2019). For all these applications of EOS, the performance of the mixing rule (MR) used is crucial.…”

Perspective: Non-conventional Force Fields for Applications in Spectroscopy and Chemical Reaction Dynamics

“…For the van der Waals terms, the potential energy is expressed as a Lennard-Jones potential with well depth ij = √ i j and range R min,ij = (R min,i + R min,j )/2 at the Lennard-Jones minimum, according to standard mixing rules. 13 This interaction captures long-range dispersion (∝ −R −6 ) and exchange repulsion (∝ R −12 ) where the power of the latter is chosen for convenience. The combination of Eqs.…”