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dc.contributor.authorLevik, Odd Ivarnb_NO
dc.date.accessioned2014-12-19T11:24:52Z
dc.date.available2014-12-19T11:24:52Z
dc.date.created2000-11-27nb_NO
dc.date.issued2000nb_NO
dc.identifier125413nb_NO
dc.identifier.isbn82-7984-124-5nb_NO
dc.identifier.urihttp://hdl.handle.net/11250/231248
dc.description.abstractThermophysical properties (dissociation enthalpy, heat capacity, metastability) and compositional properties (hydrate number, free water and fractionation) of natural gas hydrate were studied experimentally on samples that contained large amounts of ice. Methods for continuous hydrate production and sampling, and for quantification of the properties were developed. Hydrate was produced from a natural gas of ethane (5 %mol) and propane (3 %mol) in methane. A low temperature scanning calorimetry method was developed to measure dissociation enthalpy, heat capacity, hydrate number and free water (ice). During the analysis, the hydrate samples were pressurized to 1.7 MPa with methane and the system operated between the hydrate equilibrium curves of methane and the hydrate forming natural gas. A sample conditioning procedure eliminated thermal effects of desorption as the ice melted. Desorption occurred since the samples were produced and refrigerated to 255 K under a natural gas pressure of 6-10 MPa, but were analyzed and melted under a methane pressure of 1.7 MPa. A low temperature isothermal calorimetry method was developed to quantify the metastability properties. Metastability was confirmed for temperatures up to 268 K and quantified in terms of the low dissociation rate. Fractionation data were obtained in the range 3.0 to 7.5 MPa and for subcoolings between 2 and 16 K. High pressure and large subcooling is desirable to suppress fractionation. A fractionation model was proposed. The model coincides with the van der Waals-Platteeuw model for zero subcooling. No fractionation is assumed for hypothetical hydrate formation at infinite driving force (subcooling). Between these two extremes an exponential term was used to describe the fractionation. The model predicted fractionation with an accuracy of about 1%abs corresponding to 1-10%rel.nb_NO
dc.languageengnb_NO
dc.publisherFakultet for ingeniørvitenskap og teknologinb_NO
dc.relation.ispartofseriesDr. ingeniøravhandling, 0809-103X; 2000:97nb_NO
dc.subjectGeophysicsen_GB
dc.subjectNATURAL SCIENCES: Physics: Other physics: Geophysicsen_GB
dc.titleThermophysical and compositional properties of natural gas hydratenb_NO
dc.typeDoctoral thesisnb_NO
dc.source.pagenumber164nb_NO
dc.contributor.departmentNorges teknisk-naturvitenskapelige universitet, Fakultet for ingeniørvitenskap og teknologinb_NO
dc.description.degreedr.ing.nb_NO
dc.description.degreedr.ing.en_GB


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