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AssigneesLinde Aktiengesellschaft, Den Norske Stats Oljeselskap A.S.
InventorsRudolf Stockmann, Wolfgang Forg, Manfred Bolt, Manfred Steinbauer, Christian Pfeiffer, Pentti Paurola, Arne Olav Fredheim, Oystein Sorensen
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The invention relates to a method for liquefying a stream rich in hydrocarbons, especially a stream of natural gas, by the indirect exchange of heat with the refrigerants in a closed-circuit cascade of mixed refrigerants. According to the invention, said closed-circuit cascade of mixed refrigerants consists of at least 3 circuits of mixed refrigerants, with each circuit comprising different refrigerants. The first of the three mixed refrigerant circuits is used for pre-cooling (E1), the second for liquefying E2), and the third for super-cooling (E3) the hydrocarbon-rich stream (1) to be liquefied. The method provided for in the invention reduces specific energy consumption and investment costs since the three circuits of mixed refrigerants are or can be optimally adjusted to the enthalpy temperature curves of the hydrocarbon-rich stream to be liquefied and the refrigerant mixtures.
A process for liquefying a hydrocarbon-rich stream by indirect heat exchange with the refrigerants of a mixed-refrigerant cascade cycle, wherein the mixed-refrigerant cascade cycle comprises at least 3 mixed-refrigerant cycles having different refrigerant compositions, the first of the 3 mixed-refrigerant cycles serves for precooling (E1), the second mixed-refrigerant cycles serves for liquefying (E2) and the third mixed-refrigerant cycles serves for subcooling (E1) the hydrocarbon-rich stream(1) to be liquefied, characterized in that the mixed-refrigerants are subcooled and either work expanded or subjected to Joule-Thomson expansion, and the resultant cooled gas is heated in indirect heat exchange with said hydrocarbon-rich stream, and the resultant vaporized mixed refrigerants are compressed at temperatures less than ambient temperature by at least two of the three cold-intake compressors (P3, L3, S3) each compressor compressing a different mixed refrigerant.
Process for liquefying a hydrocarbon-rich stream according to 2, characterized in that the mixed refrigerant of the second of the 3 mixed-refrigerant cycles (L5, L6, . . . ) essentially comprises 5 to 15 mol % methane, 0 to 80 mol % ethylene or ethane and 10 to 20 mol % propane.
In a process for liquefying a hydrocarbon-rich stream, by indirect heat exchange with the refrigerants of a mixed-refrigerant cascade cycle, wherein the mixed-refrigerant cascade cycle comprises at least 3 mixed-refrigerant cycles having different refrigerant compositions, the improvement wherein the compressors (P3, L3, S3) used for compressing the mixed refrigerant are driven by only one drive apparatus.
Dependencies are inferred from the claim text.