Browsing by Author "Atilhan, Mert"
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Item A new cubic equation of state(Texas A&M University, 2004-09-30) Atilhan, MertThermodynamic properties are essential for the design of chemical processes, and they are most useful in the form of an equation of state (EOS). The motivating force of this work is the need for accurate prediction of the phase behavior and thermophysical properties of natural gas for practical engineering applications. This thesis presents a new cubic EOS for pure argon. In this work, a theoretically based EOS represents the PVT behavior of pure fluids. The new equation has its basis in the improved Most General Cubic Equation of State theory and forecasts the behavior of pure molecules over a broad range of fluid densities at both high and low pressures in both single and multiphase regions. With the new EOS, it is possible to make accurate estimations for saturated densities and vapor pressures. The density dependence of the equation results from fitting isotherms of test substances while reproducing the critical point, and enforcing the critical point criteria. The EOS includes analytical functions to fit the calculated temperature dependence of the new EOS parameters.Item Gas Hydrate Equilibrium Measurements for Multi-Component Gas Mixtures and Effect of Ionic Liquid Inhibitors(2014-04-07) Othman, Enas AzharQatar holds the world's third-largest proven reserves of natural gas at 885 trillion cubic feet according to a recent report. Because of its desert climate, gas hydrate formation may seem an unlikely event in Qatar. However, its natural gas reservoirs are located 80 km offshore, in the North Field, and the production of liquefied natural gas (LNG) depends on reliable flow from offshore wellheads to onshore processing facilities. Classical methods for inhibiting hydrate formation are used in order to prevent pipeline plugging but changing gas concentrations and operating conditions make flow assurance quite challenging in the North Field. Between 2008 and 2011, sudden temperature drops near gas pipelines caused various incidents of gas pipeline blockage by hydrates, with a loss of US$ 10 million per day due to lost production for almost 4 weeks. Such unplanned shut downs jeopardize the reliable export of LNG to end users. This work presents the recent investigation on synthetic multi-component gas mixtures whose compositions are typical of Qatari natural gases with initiatives aimed at helping producers minimize costs, optimize operations, and prevent interruption of gas flow in offshore drilling and production. In addition, it presents hydrate inhibition data from a newly commissioned micro bench top reactor, a high-pressure autoclave and a rocking cell. The conditions for hydrate formation for pure methane and carbon dioxide were also measured, for validation purposes. The measured data were compared with literature results and those of a commercial simulator, HydraFLASH?. Upon validation of the calibration data and determination of the apparatus uncertainty, results for hydrate formation equilibrium points for Qatari natural gas sample were collected and compared to HydraFLASH? predictions. Different percentages of 2-hydroxy-N,N,N-trimethylethanaminium chloride, also known as choline chloride ionic liquid, were used as hydrate inhibitor for the same gas mixture. The ionic liquid?s inhibition performance was compared to that of classical thermodynamic inhibitors (e.g. methanol). Ionic liquid inhibition showed (0.7 ? 1.8) oC and (2 - 2.6) oC shift in the hydrate equilibrium curve with 1 wt. % and 5 wt. % of choline chloride respectively. While the inhibition performance of 1 wt. % and 5 wt. % of methanol, obtained using HydraFLASH? software, were 2.8 oC and 4.4 oC respectively.Item High accuracy p-rho-t measurements up to 200 MPa between 200 K and 500 K using a compact single sinker magnetic suspension densimeter for pure and natural gas like mixtures(2009-06-02) Atilhan, MertHighly accurate density data is required for engineering calculations to make property estimations in natural gas custody transfer through pipelines. It is also essential to have accurate pressure-volume-temperature (PVT) data for developing equations of state (EOS). A highly accurate, high pressure and temperature, compact single sinker magnetic suspension densimeter has been used for density measurements. First, the densimeter is calibrated against pure component densities for which very reliable data are available. After validating its performance, the densities of four light natural gas mixtures that do not contain components heavier than hexane and two heavy gas mixtures containing hexane and heavier components having fractions more than 0.2 mole percent were measured. The light mixtures were measured in the temperature range of 250 to 450 K and in the pressure range of 10 to 150 MPa (1450 to 21,750 psi); the heavy mixtures were measured in the range of 270 to 340 K and in the pressure range of 3 to 35 MPa (500 to 5,000 psi). Out of those, the data for only four light natural gas mixtures have been presented in the dissertation due to confidentiality agreements that are still in force. A force transmission error and uncertainty analysis was carried out. The total uncertainty was calculated to be 0.11%. Data calculated in this work is compared with the current industry standard EOS for natural gas systems (AGA8-DC92 EOS) and GERG EOS, which is the most recently developed EOS for natural gas systems. The data measured as a part of this research should be used as reference quality data, either to modify the parameters of AGA8-DC92 EOS and GERG EOS or to develop a more reliable equation of state with wider ranges of pressure and temperature.