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Offshore LNG Unloading: New Large-Bore Cryogenic Hoses & BOG Analysis
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Offshore LNG Unloading: New Large-Bore Cryogenic Hoses & BOG Analysis


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  • 1. Offshore LNG† Unloading:New Large-Bore Cryogenic Hoses & BOG* AnalysisJose CasellaUniversity of Salford. UK+33(0)642382359casella.jose@gmail.com1† LNG : Liquefied Natural Gas.*BOG: Boil-off gas
  • 2. Outline:Objectives22ResultsMethodologyProblem DefinitionIntroductionConcluding Remarks
  • 3. 3 Financial impact of Large-bore Cryogenic hoses in Offshore LNGUnloading. Optimize the annual LNG shipping costs and energy consumption of atypical Floating Storage and Regasification Unit (FSRU).Objectives:
  • 4.  Cryogenic Hoses Weakest link of the LNG Chain Friction losses and BOG (1.275 billion USD in BOG in 2007). Diameters smaller than those required for reasonable pressure dropat the typical unloading rates.Introduction4 Liquefied Natural Gas Offshore LNG Unloading
  • 5. Problem Definition.5 BOG: Unloading at Low peak periods. Different operating conditions. Forecast Energy costs? Optimize Shipping costs?LNGVaporizersHP pumpsBOG CompRecondenserStorageLNG carrierTransmissionLOWSEND-OUT RATE!Flaring, VentingApproach:1) CFD2) Gas Processing Simulations3) Financial Assessment
  • 6. Methodology LNG Composition & Properties: P-H generated using Peng-Robinson Equation [7]. CFD RANS Sparlat-Allmaras turbulentmodel. Isothermal, Incompressible, Novaporization Fluid domain length of 5D based DNS. Periodic conditions (Velocity – EddyViscosity) Height of the First layer (y+=200) 6
  • 7. Results CFD Flow detaches at the top of the primary corrugationand recirculation vortices between consecutivecorrugations. Helical corrugations inducing swirl. High pressure zone at 45º upstream the top of thecorrugations while low pressure zones are expectedat the top of the corrugation. (flow periodicallydetaches – Risk of Bubble formation). 4 Empirical Correlations Accuracy of 9.5% with Riley’s equation.7Up to 70% of the total pressure drop! Vaporization Numerical Wall ShapeOptimization Liners
  • 8. Results Analysis Tool:8
  • 9.  Lowest heat transfer and pressure drop in a 24” hose. BOG in 20” is smaller that 2x16” at unloading rateslower than 10,500 m3/hr.Results BOG The friction losses are approximately 60%lower with a single line of 24” Optimum LNG Unloading rate forminimum BOG at the recondenser9CAPEX of BOG CompStationHigh Unloading rates atLow Peak periods
  • 10. Results Financial Impact102x16”1x20”1x24”OptimumUnloading RatesHose Unloading rateEnergy Shipping2x16” 9,000 m^3/hr 0.2 MM$ 139 MM$1x20” 8,000 m^3/hr -1.8% +0.95 %1x24” 11,000 m^3/hr -15.4% -1.38 %Annual CostsEnergy Costs Shipping Costs
  • 11. Concluding Remarks Optimistic solution looking towards cost reduction in the LNG Industry.11 Account with up to 70% of the total pressure drop. R&D of Liners The size of BOG compression station (CAPEX) can be reduced significantlyonly by deployment of large-bore cryogenic hoses. Financial impact not only in energy consumption but also is shipping costs (1.4MMUSD per year). Novelty: Integration of all components of the RT. Statistical treatment to forecast probability distribution. Coupling CFD, gas processing simulation and financial assessment.
  • 12. Thanks“Real knowledge is to know the extent of ones ignorance.”(Confucius, 551-479 BC)12
  • 13. AcknowledgementsThe author wish to acknowledge and thank to Dunlop Oil & Marine Ltd andAltair Engineering for permission to publish this work at the IGEMCompetition. (UK, 2013)13
  • 14. References1) McDonald, David, Chiu, Chen-Hwa and Adkin, Dean. Comprehensive Evaluation of LNG Transfer Technologyfor Offshore LNG Development. Qatar : ChevronTexaco, 2004.2) CFD Modelling of Corrugated Flexible Pipe. Jaiman, Rajeev K, Oakley, Owen H and Adkins, J Dean. OMAE2010-20509, 2010, Offshore Mechanics and Artic Engineering, p. 10.3) Improved explicit equations for estimation of the friction factor in rough and smooth pipes. Romeo, E., Royo, C.and Monz´on, A. 2002, Chemical Engineering Journal, pp. pp. 369-374.4) A One-Equation Turbulent Model for Aerodynamic Flows. Sparlat, P. R. and Allmaras, S. R. s.l. : AIAA, 1992. Paper92-0439.5) Minimizing Boil-Off Losses in Liquefied Natural Gas Transportation. Hasan, M.M. Faruque, zheng, AlfredMinghan and Karimi, I. A. 2009, Industrial & Engineering Chemistry Research, p. 10.6) Liu, Chaowei, et al. Thermodynamic-Analysis-Based Design and Operation for Boil-Off Gas Flare. Department ofChemical Engineering, Lamar UniVersity. Texas, US : Ind. Eng. Chem. Res, 2010. p. 9.7) Aspen Physical Property System: Physical Property Methods. Cambridge : AspenTech, 2007. Version 2006.5.8) Fully developed turbulent pipe flow: a comparison between direct numerical simulation and experiment. Eggels, J. G.M., et al. Journal of Fluid Mechanic, UK : Cambridge University Press, 1994, Vol. vol. 268.9) Pisarenco, Maxim. Friction Factor Estimation for Turbulent Flows in Corrugated Pipes with Rough Walls.Department of Mathematics and Computer Science. Eindhoven : TECHNISCHE UNIVERSITEIT EINDHOVEN,2007.10) Modelling of Boil-Off Gas in LNG Tanks: A Case. Adom, Ebenezer, Islam, Sheikh Zahidul and Ji, Xianda. RobertGordon University, 2010, International Journal of Engineering and Technology, Vol. Vol. 2, p. 5.11) Sedlaczek, Rafal. BOIL-OFF IN LARGE- AND SMALL-SCALE. Trondheim : Norwegian University of Science andTechnology, 2008.12) Tarakad, Ram R. LNG Receiving and Regasification Terminals, An Overview of Design, Operation and ProjectDevelopment Considerations. Houston, Texas : Zeus Development Corporation, 2003.13