On a previous occasion, the Author (of the University of Manitoba) has pointed out that it would be economically and ecologically advantageous to process and ship LNG at a higher pressure than atmospheric; the gas would then be carried at a correspondingly higher temperature, above the--260 deg F of current practice. After mentioning that a novel design of hull has been proposed for this purpose, and that a case study has been performed for a one-billion cu. ft./day plant in which the product would be handled at--140 deg F instead of the usual--260 deg F, he discusses the determination of the optimum temperature for the LNG cargo. This optimum temperature can be found by balancing the savings in refrigeration costs against the increased costs for the ship's steel when higher pressures are used. These two cost variables, and their relationships, are examined, and curves, covering the temperature range up to--120 deg F, are presented in which they are shown for the operation of both one ship and four ships and for both 3.5% and 9% nickel steel as the construction material for their tanks. This analysis shows that the savings from operating at an intermediate temperature are greatest when the transportation distance is short, since fewer ships and therefore less steel is needed. The use of a cheap steel is advantageous, and it may even be possible to use an ordinary mild steel, insulated internally with polyphenylene oxide foam; such a design would shift the break-even point towards operation at a higher temperature and increase the potential saving. However, there is a potential saving by operating at a higher temperature than that of current practice, irrespective of the number of ships and of the unit cost of materials.

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  • Corporate Authors:

    Institute of Marine Engineers

    Memorial Building, 76 Mark Lane
    London EC3R 7JN,   England 
  • Authors:
    • Bennett, C P
  • Publication Date: 1979-6

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Filing Info

  • Accession Number: 00303327
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Feb 27 1980 12:00AM