Aviation fuels derived from the gas-to-liquid (GTL) technology may be used as drop-in alternatives to conventional oil-derived fuels. Reliable composition-property relations must be developed based on experimental data to correlate the hydrocarbon compositions of formulated synthetic fuels with their properties to be certified for aviation commercial use. An experimental and property-integration framework for the design of synthetic jet fuels from GTL-based kerosene derived by evaluating the role of aromatics on resultant fuel properties is presented. The experimental results were used to develop property-mixing rules and linear programming for the design of optimum fuel compositions that meet the ASTM specifications. The role of aromatics on critical physical properties for jet fuel certification is revealed. A practical solution for jet fuels blending through optimization of jet fuel formulation based on cost and technically effective manners is provided.
Gas-to-liquid (GTL) products have increasingly become a promising energy resources over the past two decades. Qatar possesses the third largest proven reserve of natural gas in the world, with a net capacity approaching 900 tcf (trillion cubic foot). This has motivated Qatar to develop a long term vision, involving the investment of huge expenditures into world-class commercial plants that convert natural gas into value-added liquid hydrocarbon products. This vision was translated into the Oryx GTL plant in late 2006 and the Shell Pearl GTL plant reported to be the largest in the world, which began operations officially at the end of 2011, leading Qatar to be described as the world capital of GTL. The substantial usage of energy in Fischer-Tropsch (FT) GTL processes and the complexity of energy distribution throughout the process offer opportunities for heat integration and waste heat recovery. The objective of this paper is to carry out an energy integration analysis for a typical GTL process. The approach was started with process simulation to develop the base-case data for the process. Next, energy integration tools were used to optimize energy distribution, heat exchange, and waste heat recovery. Finally, simulation and techno-economic analysis were utilized to assess the performance of the proposed design changes and their economic viability. The resultant pinch diagram showed that a single pinch case was faced with a fixed driving force of 10 oC, in which both external cooling and heating utilities were required to satisfy energy needs. Meanwhile, the Grand Composite Curve (GCC) showed that flue gases cover most of the heating utility while cooling water covers all the required cooling utility. Moreover, the waste heat recovery study supported by HYSYS software illustrated considerable recoveries in steam qualities from discharged flue gases within the FT reactor section. In conclusion, energy integration on a GTL process was realized to be a promising one as the targets for net energy savings were found to be close to 40%. Additionally, generation of various qualities of steam can be obtained in a cost-effective manner. At the top of it, most of the recommended projects have attractive payback periods, below six years.
Abstract-In this paper, the energy performance of a selected UHDE Ammonia plant is optimized by conducting heat integration through waste heat recovery and the synthesis of a heat exchange network (HEN). Minimum hot and cold utility requirements were estimated through IChemE spreadsheet. Supporting simulation was carried out using HYSYS software. The results showed that there is no need for heating utility while the required cold utility was found to be around 268,714 kW. Hence a threshold pinch case was faced. Then, the hot and cold streams were matched appropriately. Also, waste heat recovered resulted with savings in HP and LP steams of approximately 51.0% and 99.6%, respectively. An economic analysis on proposed HEN showed very attractive overall payback period not exceeding 3 years. In general, a net saving approaching 35% was achieved in implementing heat optimization of current studied UHDE Ammonia process.
With sponsorship from Qatar Science and Technology Park to support Qatar Airways' vision as a world leader in alternative fuels, our research team started work in this field in 2009 as part of a unique academia-industry collaboration model. The undergraduate student researchers are funded by Qatar National Research Fund and play a major role in this project, participating in all its experimental, computational, and theoretical phases. Phase I of this work covers the development of correlations between the Gas-to-Liquid (GTL) synthetic jet fuels' building blocks (paraffinic hydrocarbons) and their physical properties (i.e. density, viscosity, flash point, freezing point, heat content, etc.). The objective of this phase was to identify optimum fuel characteristics and to meet aviation industry standards (e.g. ASTM D1655 & D7566). In Phase II, the experimental data were analyzed using sophisticated statistical techniques (i.e. Artificial Neural Network) to accurately describe the (non-)linear trends for all properties. In Phase III, we investigated the role of aromatics in improving certain properties of GTL jet fuels, such as density and elastomer compatibility (which is essential for fuel tank sealing). Analogous to the investigations conducted in Phase I, visualization models were developed to identify the optimum GTL jet fuel composition formulated by normal-, iso-, cyclic-paraffins and mono-aromatics. Currently, we are working on Phase IV which involves expanding our model to include new additives and component families in order to optimize the blending strategy for Qatar's GTL products and to increase their market value. The success in this direction could provide cheaper and more environmentally friendly synthetic jet fuels derived from natural gas, compared to the current oil-derived Jet A-1 fuels. In addition to the technical results, our fuel characterization lab acts as a training ground for young and talented scientists in order to develop their technical and soft skills. Students get the opportunity to work in a professional environment with strict safety and quality regulations on par with industrial standards, to report scientific data and to draw conclusions from this information in order to make decisions on the next course of research activities.
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