Measurement and Calculation of CO₂ Frost Points in CH₄ + CO₂/CH₄ + CO₂ + N₂/CH₄ + CO₂ + C₂H₆ Mixtures at Low Temperatures

Abstract

In published literature, only very limited data for CO2 frost point in natural gas mixture can be found. Measurements and calculations for CH4 + CO2/CH4 + CO2 + N2/CH4 + CO2 + C2H6 mixtures over a wide range of temperature, pressure, and compositions were performed in this work. The measurements were conducted through a simple equilibrium cell by static analytic method utilizing sampling technique. The calculations were carried out by fugacity balance model based on Peng–Robinson (PR) equation of state (EoS) with van der Waals mixing rule. The calculated results agree well with the experimental results, demonstrating the reliability of PR EoS based model. By comparing data obtained from gas mixtures with different nitrogen contents and ethane contents, it is found that both nitrogen and ethane have little effect on CO2 frost point. However, the maximum pressure for CO2 frosting in CH4 + CO2 + N2 ternary mixture increases with nitrogen content; oppositely, it decreases with ethane content in CH4 + CO2 + C2H6 ternary mixture.