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Salinity Effect on the Equilibria and Kinetics of the Formation of CO2 and R-134a Gas Hydrates in Seawater

  • Johanna, Lianna (Department of Chemical Engineering, Pukyong National University) ;
  • Kim, A Ram (Department of Chemical Engineering, Pukyong National University) ;
  • Jeong, Guk (Department of Chemical Engineering, Pukyong National University) ;
  • Lee, Jea-Keun (Department of Environmental Engineering, Pukyong National University) ;
  • Lee, Tae Yun (Department of Environmental Engineering, Pukyong National University) ;
  • Lim, Jun-Heok (Department of Chemical Engineering, Pukyong National University) ;
  • Won, Yong Sun (Department of Chemical Engineering, Pukyong National University)
  • Received : 2016.01.27
  • Accepted : 2016.06.16
  • Published : 2016.07.27

Abstract

Gas hydrates are crystalline solids in which gas molecules (guests) are trapped in water cavities (hosts) that are composed of hydrogen-bonded water molecules. During the formation of gas hydrates in seawater, the equilibria and kinetics are then affected by salinity. In this study, the effects of salinity on the equilibria of $CO_2$ and R134-a gas hydrates has been investigated by tracing the changes of operating temperature and pressure. Increasing the salinity by 1.75% led to a drop in the equilibrium temperature of about $2^{\circ}C$ for $CO_2$ gas hydrate and $0.38^{\circ}C$ for R-134a gas hydrate at constant equilibrium pressure; in other words, there were rises in the equilibrium pressure of about 1 bar and 0.25 bar at constant equilibrium temperature, respectively. The kinetics of gas hydrate formation have also been investigated by time-resolved in-situ Raman spectroscopy; the results demonstrate that the increase of salinity delayed the formation of both $CO_2$ and R134-a gas hydrates. Therefore, various ions in seawater can play roles of inhibitors for gas hydrate formation in terms of both equilibrium and kinetics.

Keywords

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