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 (O-2 and N-2) 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 N-2-CH4-CO2 and N-2-O-2-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 (p, T, x, y) 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 N-2-O-2 CH4-CO2 system is also presented in this work and compared with experimental data, providing good agreement.