Experimental Study of the Influence of Nitrogen and Oxygen on the Solubility of Solid Carbon Dioxide in Liquid and Vapor Methane at Low Temperature

Undesired solid CO₂ formation is a main issue for the liquefied natural gas (LNG) industry and, more recently, for the bioLNG production. The abundance of CO₂ solubility data in liquid methane may not be sufficient to fully understand the problem when important amounts of air gases (O₂ and N₂) are present in the natural gas or biomethane. Scarcity and incompleteness of available solubility data involving nitrogen and oxygen motivated the production of original solid–liquid–vapor equilibrium (SLVE) data for the N₂–CH₄–CO₂ and N₂–O₂–CH₄–CO₂ systems. The solubility limit of CO₂ in both liquid and vapor phases is measured in this work to allow the definition of solid formation conditions. A static analytic methodology is used for obtaining (<i>p</i>, <i>T</i>, <i>x</i>, <i>y</i>) data at SLVE in the temperature range from 125 to 146 K. Experimental results obtained in this work show that the addition of nitrogen and oxygen in methane decreases the solubility of CO₂ in the liquid phase. A thermodynamic model for the calculation of solid–liquid–vapor equilibrium of the N₂–O₂–CH₄–CO₂ system is also presented in this work and compared with experimental data, providing good agreement