Recent Advances in Experimental Measurements of Mixed-Gas Three-Phase Hydrate Equilibria for Gas Mixture Separation and Energy-Related Applications

Clathrate hydrates are currently studied extensively due to their involvement in important industrial processes. For certain industrial applications (e.g., flow assurance in oil/gas industry), they are considered a nuisance and their presence needs to be either suspended completely or adequately controlled. On the other hand, for other industrial applications (e.g., gas mixture separation, water desalination, and purification), hydrate formation is sought after, since it can facilitate the desired outcome. In either case, it is essential to have reliable values for the hydrate equilibrium conditions, in order to design appropriately the corresponding industrial applications. In the current study, we review the experimental studies that have reported three-phase hydrate equilibrium measurements. We focus primarily on studies that were published after the year 2008. Furthermore, we report only studies that examine the gas mixtures of two or more components. Of primary interest are gas mixtures that have significant industrial applications and include components such as carbon dioxide, nitrogen, hydrogen, methane, ethane, propane, hydrogen sulfide, and oxygen. The examined mixtures include at least one of the aforementioned gases. Of particular interest in this review are applications such as gas mixture separation (where hydrate promotion is desirable) and energy-related application such as flow assurance during oil/gas production and transportation (where hydrate inhibition is desirable). The mixtures that are included in the review are grouped under 15 gas mixture types. For most of the gas mixtures that are examined, the related industrial applications are identified and briefly discussed. In the current review, the different gas mixtures are also critically discussed and suggestions for possible future directions are presented regarding the examination of tentative additives to be used for promotion or inhibition.