Henry’s Law Constants and Vapor–Liquid Distribution Coefficients of Noncondensable Gases Dissolved in Carbon Dioxide

Abstract

The accurate determination of the solubilities of the typical impurity gases present in captured CO2 in the carbon capture, utilization, and storage chain is an essential prerequisite for the successful modeling of the CO2 stream thermodynamic properties. In this paper, Henry’s law constants and the vapor–liquid distribution coefficients of six noncondensable gases, namely, N2, O2, H2, CH4, Ar, and CO, at infinite dilution in liquid CO2 are derived based on published vapor–liquid equilibrium data at temperatures ranging from the triple point (216.59 K) to the critical point (304.13 K) of CO2. The temperature dependence of Henry’s law constants of the six gases is correlated using approximating functions previously proposed for aqueous solutions. A correlation that provides the best fit for the Henry constants data for all the six gases, with the accuracy (absolute average deviation %) of 4.2%, is recommended. For N2, O2, H2, Ar, and CO, the combined standard uncertainty in the derived Henry constants is less than 6%, whereas for CH4, due to a larger deviation between the utilized data, the uncertainty is less than 18%. Analysis of the temperature variation of the vapor–liquid distribution coefficient at infinite dilution shows that when all the six gases are present in the CO2 stream, separation of N2, O2, Ar, and CO from CO2 can be problematic due to their similar volatilities, while the distinct volatilities of H2 and CH4 at lower temperatures make their separation from CO2 easier.

Application of the Henry's law model for prediction of the vapour-liquid equilibria in impure CO2 streams

“…Henry's law, which is widely used in environmental engineering, can provide a convenient basis for calculation of physical properties of dilute CO2 mixtures with volatile gases. Recently, we have determined the Henry's law constants for several gases dissolved in CO2 [2]. Given that Henry's law is a limiting law that only applies for "sufficiently dilute" solutions, it needs to be implemented in a suitable modelling framework to enable accurate VLE calculations at finite dilutions.…”

“…For dilute binary mixtures of CO2 with non-condensable gases, including N2, H2, O2, Ar, CH4 and CO the Henry constants can be calculated using the correlation recommended in our recent study [2]:…”