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Dual mixed refrigerant natural gas liquefaction

  • US 4,545,795 A
  • Filed: 10/25/1983
  • Issued: 10/08/1985
  • Est. Priority Date: 10/25/1983
  • Status: Expired due to Term
First Claim
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1. A process for the liquefaction of natural gas using two closed cycle, multicomponent refrigerants wherein high level refrigerant cools a low level refrigerant and the low level refrigerant cools and liquefies the natural gas, comprising the steps of:

  • a. cooling and liquefying a natural gas stream by heat exchange with a low level multicomponent refrigerant in a first closed refrigeration cycle, which refrigerant is rewarmed during said heat exchange,b. compressing said rewarmed low level refrigerant to an elevated pressure and aftercooling it against an external cooling fluid,c. further cooling said low level refrigerant by indirect multiple stage heat exchange against a high level multicomponent refrigerant in a second closed refrigeration cycle, which high level refrigerant is rewarmed during said heat exchange,d. compressing said rewarmed high level refrigerant to an elevated pressure and aftercooling it against an external cooling fluid to partially liquefy said refrigerant,e. phase separating said high level refrigerant into a vapor phase refrigerant stream and a liquid phase refrigerant stream such that lighter refrigerant components are available for lower level refrigeration duty in the cooling step of clause c,f. subcooling and expanding portions of the liquid phase refrigerant stream to lower temperature and pressure in multiple stages to provide the cooling of the low level refrigerant of step (c) and to cool and liquefy the vapor phase refrigerant stream of step (e),g. cooling and then expanding the liquefied vapor phase refrigerant stream to lower temperature and pressure to provide the lowest stage of cooling to the low level refrigerant.

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