Vapor-liquid equilibria calculations for components of natural gas using Huron-Vidal mixing rules

Fossil fuels, such as oil or natural gas are composed of a complex mixture of hydrocarbons and impurities such as water, carbon dioxide, or nitrogen. The oil and gas companies have great interest in removing these impurities since they impact negatively natural gas production. In this regard, natural gas is commonly dehydrated with an absorbent agent, such as triethylene glycol (TEG). Due to its low volatility, there is little research concerning its partition throughout vaporization. Therefore, simulations of the natural gas industry processes need accurate calculations of thermodynamic properties and phase equilibria for the optimization of operations and design of new installations. For that, the Peng-Robinson equation of state is the most frequent model used in gas applications, refineries, and petrochemistry in a wide range of simulators. In this work, three modeling approaches are proposed to improve thermodynamics calculations: The models are based on the Peng-Robinson equation of state associated with non-random two-liquid model through the original Huron-Vidal (HV), first order modified Huron-Vidal (PR-MHV1-NRTL) and Van der Waals (PR-VdW) mixing rules. Moreover, the Peng-Robinson was coupled with the Almeida-Aznar-Telles modification in the attractive term. Parameters for the binary systems composed of components of natural gas as well as triethylene glycol were estimated. The most important results are that vapor-liquid equilibria data from 15 binary systems were correlated with the proposed modeling approaches, and a phase diagram for the ternary system methane/CO 2 /TEG was predicted. The main conclusions are that the PR-VdW and PR-MHV1-NRTL models are adequate to represent the available binary VLE data for natural gas components and mixtures of TEG with methane and CO 2 , but more experimental data regarding the molar fraction of TEG in the vapor phase are important; and that the TEG loss through vaporization in a flash vent could be around 204g per day. Graphic abstract