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Hydrocarbon gas processing

  • US 4,157,904 A
  • Filed: 10/18/1977
  • Issued: 06/12/1979
  • Est. Priority Date: 08/09/1976
  • Status: Expired due to Term
First Claim
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1. In a process for separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed gas containing hydrocarbons, methane and ethane together comprising a major portion of said feed gas, wherein(a) said feed gas under pressure is cooled sufficiently to partially condense said gas forming thereby a liquid portion of said feed gas and a vapor feed gas;

  • (b) at least some of the liquid portion is expanded in an expansion means to a lower pressure whereby a part of said liquid portion vaporizes to cool the expanded liquid portion to a refrigerated temperature; and

    (c) at least some of the expanded liquid portion is subsequently treated in a fractionation column to separate said relatively less volatile fraction;

    the improvement comprising(1) combining at least part of liquid portion (a) with a process stream having a bubble point below the bubble point of said liquid portion (a), to form thereby a combined stream;

    (2) supplying said combined stream to said expansion means at a temperature which is below the bubble point of said liquid portion (a);

    (3) expanding said combined stream to said lower pressure, whereby the refrigerated temperature achieved in expansion step (b) is reduced;

    (4) thereafter supplying at least some of said expanded combined stream to said fractionation column at a first feed position; and

    (5) expanding at least a portion of said vapor feed gas in a work expansion engine to said lower pressure, and supplying the expanded vapor to the fractionation column at a second feed point, said second feed point being at a lower column position than said first feed point.

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