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NGL recovery from natural gas using a mixed refrigerant

  • US 10,139,157 B2
  • Filed: 02/22/2012
  • Issued: 11/27/2018
  • Est. Priority Date: 02/22/2012
  • Status: Active Grant
First Claim
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1. A process for recovering natural gas liquids (NGL) from a hydrocarbon-containing feed gas stream, said process comprising:

  • (a) cooling and at least partially condensing a hydrocarbon-containing feed gas stream to thereby provide a cooled feed gas stream, wherein at least a portion of said cooling is carried out via indirect heat exchange with a mixed refrigerant stream in a first heat exchanger of a closed-loop mixed refrigerant refrigeration cycle;

    (b) separating said cooled feed gas stream into a first vapor stream and a first liquid stream in a vapor-liquid separator;

    (c) splitting said first vapor stream into a first vapor portion and a second vapor portion;

    (d) cooling at least a portion of said first vapor portion in said first heat exchanger to thereby provide a cooled first vapor stream, wherein at least a portion of said cooling is carried out via indirect heat exchange with said mixed refrigerant stream used to perform said cooling of step (a);

    (e) flashing said cooled first vapor stream to thereby provide a first flashed stream;

    (f) flashing said second vapor portion to thereby provide a second flashed stream;

    (g) flashing the entire first liquid stream to provide a two-phase fluid stream having a vapor fraction of at least 0.10;

    (h) introducing said first flashed stream, the entire two-phase fluid stream, and said second flashed stream into a distillation column via respective first, second, and third fluid inlets of said distillation column, wherein said first fluid inlet is located at a higher separation stage than said second and said third fluid inlets, and wherein said third fluid inlet is located at the same separation stage or at a lower separation stage than said second fluid inlet; and

    (i) recovering an overhead residue gas stream and a liquid bottoms product stream from said distillation column, wherein said recovering step includes operating said distillation column in a C2 recovery mode or a C2 rejection mode,wherein, when said distillation column is operated in said C2 recovery mode, said liquid bottoms product stream comprises at least 90 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises less than 10 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger, andwherein, when said distillation column is operated in a C2 rejection mode, said liquid bottoms product stream comprises less than 30 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises at least 70 percent of the total moles of C2 components in said hydrocarbon containing feed gas stream introduced into said first heat exchanger,wherein prior to step (a), said mixed refrigerant stream is compressed, cooled, and expanded to thereby generate refrigeration, wherein at least a portion of said refrigeration is used to accomplish at least a portion of said cooling of step (a) and at least a portion of said cooling of step (d).

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