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Measurement and Calculation of Surface Tension of Oil, Gas and Glycol
Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, Department of Electrical Power Engineering.
Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, Department of Electrical Power Engineering.
2014 (English)MasteroppgaveStudent thesis
Abstract [en]

The importance of surface tension in separation design was evaluated in this report. Surface tension was found to have importance when calculating essential design parameters, like droplet size, which is is fundamental in several vessel design operations. Other impacts of surface tension in separation are the ability to sustain a liquid film and avoid droplet re-entrainment into the gas flow, both being discussed in the report. Miscalculation of surface tension could lead to incorrect sizing of separation equipment, subsequently causing expensive fault in operation and decreased separation effect. The main objective of this thesis was to experimentally measure surface tension with the pendant drop technique. Although surface tension was the main task, density and solubility data were also collected and evaluated, as they too are important parameters in separator design. The measurements were carried out on MEG/water systems because of low availability of such data in the literature. The deviation of the surface tension measurements was calculated on the basis of recommendations from ISO, and the total average deviation for all mixtures was stated to be 2.00%. The second objective was to evaluate models for the calculation of surface tension in process simulation software. The simulation tools PRO/II, HYSYS, PVTSim and NeqSim were used for calculation. PRO/II and HYSYS use simple models that are based on pure component values. PVTsim utilizes the well-known parachor method when simulating hydrocarbon systems, while for MEG/water systems it uses a model based on the corresponding state theory. NeqSim uses the most complicated and computational demanding model, the gradient theory, which is based on thermodynamics. Some of the software have additional models implemented, but in this thesis the default models have been used. The MEG/water and hydrocarbon systems were simulated in the software, and thereafter compared against the experimental data. The results of the comparison regarding hydrocarbon systems showed two distinct tendencies. Firstly, the performance of PRO/II and HYSYS was not adequate. They both were, with a few exceptions, overestimating the surface tension for all mixtures. Second, even though the performance of both PVTsim and NeqSim could be termed satisfactory, NeqSim was superior to the estimations of PVTsim throughout most of the experimental data. The only exception was for the ternary systems, on which the base of surface tension data was rather insufficient. The results of the comparison regarding glycol systems showed that all software overestimate the surface tension. NeqSim was once again the software with the best accuracy, and the CPA equation of state was the overall preferred choice. In contrast to hydrocarbon mixtures PVTsim now has a large discrepancy throughout. However, the accuracy improved drastically for the 50 wt% MEG/50 wt% water mixture. PRO/II and HYSYS performed better than they did on hydrocarbon mixtures, especially for the 100wt%MEG mixture. However, as water was added to the composition, PRO/II’s deviation increased substantially.

Place, publisher, year, edition, pages
Institutt for energi- og prosessteknikk , 2014. , 152 p.
URN: urn:nbn:no:ntnu:diva-26343Local ID: ntnudaim:11052OAI: diva2:746608
Available from: 2014-09-13 Created: 2014-09-13 Last updated: 2014-09-13Bibliographically approved

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