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Thermodynamic Modeling of Wax Precipitation in Crude Oils using PC-SAFT EOS

Esmaeili, Ebrahim | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46039 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghotbi, Cyrus; Jafari Behbahani, Taraneh
  7. Abstract:
  8. Economic loss due to wax precipitation in oil exploitation and transportation has reached several billion dollars a year recently. Development of amodel for better understanding of the process of wax precipitation is therefore veryimportant to reduce the loss.Currently, there are two types of soild models. One is the solid-solution model, and the other is the multisolid-phase model.In this work, a new thermodynamic model that combines the two methods mentioned above, has been presented. The PC-SAFT EOS is used to describe the vapor, liquid and wax phase.SAFT equations describe the phase behavior of large molecules accurately. Intermolecular forces in wax phase are caused by London and Van- der walls forces. Therefore, wax phase behavior can be qualitatively explained in terms of London dispersion interactions (contribution to the van der Waals forces). The PC-SAFT equation of state estimates also properties crude oil systems using a minimum number of real components and “realistic”pseudocomponents.Characterization of crude oil has been provided by SARA test and composition of wax phase from experimental data. The three pure-component parameters required for nonassociating molecules of the wax phase for nine different oils are optimized separately. Results obtained from the PC-SAFT model have been compared with experimental observations and those results obtained using solid-solution and multisolid-phase models. From the obtained results, it can be concluded that the crude oil modeled using the PC-SAFT equation of statewith the minimum adjustable parameters properly predicts the wax phase behavior. The mean absolute average deviation percentage of WAT prediction is 0.28 and this number for the prediction of the amount of precipitated wax is12.60. In both cases, the PC-SAFT model has a much better prediction compared to other models
  9. Keywords:
  10. Wax Percipitation ; State Equation ; Statistical Assosiating Fluids Theory (SAFT) ; Oil Characterization

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