Increasing Gas Hydrate Formation Temperature for Desalination of High Salinity Produced Water with Secondary Guests

CATEGORY: PRODUCED WATER
ACS Sustainable Chem. Eng., 2013, 1 (10), pp 1218–1224
Increasing Gas Hydrate Formation Temperature for Desalination of High Salinity Produced Water with Secondary Guests
Jong-Ho Cha and Yongkoo Seol *
Yongkoo.Seol@netl.doe.gov
National Energy Technology Laboratory, U.S. Department of Energy, Morgantown, West Virginia 26507, United
Abstract
Describes a novel gas hydrate-based desalination process using water-immiscible hydrate formers; cyclopentane (CP) and cyclohexane (CH) as secondary hydrate guests to alleviate temperature requirements for hydrate formation. Researchers conducted the hydrate formation reactions in an isobaric condition of 3.1 MPa to find the upper temperature limit of CO2 hydrate formation. Simulated produced water mixed with the hydrate formers shows an increased upper temperature limit from −2 °C for simple CO2 hydrate to 16 and 7 °C for double (CO2 + CP) and (CO2 + CH) hydrates, respectively. The resulting conversion rate to double hydrate was similar to that with simple CO2 hydrate at the upper temperature limit.
Hydrate formation rates (Rf) for the double hydrates with cyclopentane and cyclohexane as secondary hydrate guests are shown to be 22 and 16 times higher, respectively, than that of the simple CO2 hydrate at the upper temperature limit. Such mild hydrate formation temperature and fast formation kinetics indicate increased energy efficiency of the double hydrate system for the desalination process.
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