Gibbs ensemble Monte Carlo simulations of multicomponent natural gas mixtures

Abstract

Vapour-liquid equilibrium (VLE) and volumetric data of multicomponent mixtures are extremely important for natural gas production and processing, but it is time consuming and challenging to experimentally obtain these properties. An alternative tool is provided by means of molecular simulation. Here, Monte Carlo (MC) simulations in the Gibbs ensemble are used to compute the VLE of multicomponent natural gas mixtures. Two multicomponent systems, one containing a mixture of six components (N 2 , CH 4 , CO 2 , H 2 S, C 2 H 6 and C 3 H 8), and the other containing a mixture of nine components (N 2 , CH 4 , CO 2 , H 2 S, C 2 H 6 , C 3 H 8 , C 5 H 12 , C 7 H 16 and C 10 H 22) are simulated. The computed VLE from the MC simulations is in good agreement with available experimental data and the GERG-2008 equation of state modelling. The results show that molecular simulation can be used to predict properties of multicomponent systems relevant for the natural gas industry. Guidelines are provided to setup Gibbs ensemble simulations for multicomponent systems, which is a challenging task due to the increased number of degrees of freedom.

Vapor–Liquid Equilibrium Simulations of Hydrocarbons Using Molecular Dynamics with Long-Range Lennard-Jones Interactions

“…It has been used to simulate the VLE of linear, branched, cyclic, , and aromatic hydrocarbons. Recently, Ramdin et al used GEMC to model multicomponent natural gas mixtures, obtaining good agreement with available experimental data . However, the lack of an explicit vapor–liquid interface means interfacial properties such as surface tension cannot be examined using GEMC.…”

“…Recently, Ramdin et al used GEMC to model multicomponent natural gas mixtures, obtaining good agreement with available experimental data. 23 However, the lack of an explicit vapor−liquid interface means interfacial properties such as surface tension cannot be examined using GEMC. MD simulations of a liquid slab in contact with vapor can be used to model VLE, as well as examine interfacial behavior.…”

Molecular simulation of the vapor-liquid equilibria of xylene mixtures: Force field performance, and Wolf vs. Ewald for electrostatic interactions

“…For pure components, the number of molecules and box sizes can be found in the Supporting Information. For binary mixtures, the initial composition can be obtained with the procedure described by Ramdin et al [27] when experiments are not available. The pX-oX binary mixtures at 6.66 kPa and 81.3 kPa are simulated.…”

“…Fluid phase properties of pure components and mixtures can be computed for large ranges of conditions, even when experiments can be challenging, expensive or dangerous [25]. The Monte Carlo (MC) method in the Gibbs ensemble [26] has been widely used to compute VLE [27,28,29,30,31,32,33]. The choice of a force field that accurately describes the interaction potential between atoms and molecules is a crucial factor.…”

“…The choice of a force field that accurately describes the interaction potential between atoms and molecules is a crucial factor. The Gibbs ensemble considers two simulation boxes to simulate the properties of coexisting phases avoiding the vapor-liquid interface [27]. Fig.…”