Process for recovering ethane and heavier hydrocarbons from methane-rich pressurized liquid mixture

• US 6,564,580 B2
• Filed: 06/20/2002
• Issued: 05/20/2003
• Est. Priority Date: 06/29/2001
• Status: Expired due to Fees

• Current Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Original Assignee: Exxonmobil Upstream Research Company (Exxon Mobil Corporation)
• Inventors: Minta, Moses, Bowen, Ronald R., Kimble, E. Lawrence
• Primary Examiner(s): CAPOSSELA, RONALD C
• Application Number:
  US10/175,768
• Publication Number:
  US 20030014995A1
• Time in Patent Office: 334 Days
• Field of Search: 626/20, 626/23, 626/32, 626/35
• US Class Current: 62/623
• CPC Class Codes: F25J 2200/08 in a triple pressure main column system
• CPC Class Codes: F25J 2200/70 Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
• CPC Class Codes: F25J 2205/02 using simple phase separation in a vessel or drum
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2205/50 using absorption, i.e. with selective solvents or lean oil, heavier CnHm and including generally a regeneration step for the solvent or lean oil
• CPC Class Codes: F25J 2235/60 the fluid being (a mixture of) hydrocarbons
• CPC Class Codes: F25J 2240/30 Dynamic liquid or hydraulic expansion with extraction of work, e.g. single phase or two-phase turbine
• CPC Class Codes: F25J 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2250/02 Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger
• CPC Class Codes: F25J 2270/66 Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
• CPC Class Codes: F25J 2290/62 Details of storing a fluid in a tank
• CPC Class Codes: F25J 3/0214 Liquefied natural gas
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0238 separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/0242 separation of CnHm with 3 carbon atoms or more

Abstract

The invention is an absorption process for recovering C₂₊ components from a pressurized liquid mixture comprising C₁ and C₂₊. The pressurized liquid mixture is at least partially vaporized by heating the liquid mixture in a heat transfer means. The heat transfer means provides refrigeration to an absorption medium that is used in treating the vaporized mixture in an absorption zone. The vaporized mixture is passed to an absorption zone that produces a first stream enriched in C₁ and a second stream enriched in C₂₊ components. The pressurized liquid mixture is preferably pressurized liquid natural gas (PLNG) having an initial pressure above about 1,724 kPa (250 psia) and an initial temperature above −112° C. (−170° F.). Before being vaporized, the pressurized liquid mixture is preferably boosted in pressure to approximately the desired operating pressure of the absorption zone.

Claims

1. An absorption method for recovery of C₂₊ components from a pressurized liquid mixture containing C₁ and C₂₊, comprising:

(a) vaporizing at least part of the pressurized liquid mixture by heating the pressurized liquid mixture in a heat transfer means, said heat transfer means cooling an absorption medium; and

(b) treating the vaporized stream in an absorption zone with the absorption medium to produce a first stream enriched in C₁ and a second stream enriched in C₂₊ components.

2. The method of claim 1 wherein the pressurized liquid mixture is pressurized liquid natural gas (PLNG).

3. The method of claim 1 wherein the pressurized liquid mixture has an initial pressure above about 1,724 kPa (250 psia) and an initial temperature between about −

80°

C. (−

112°

F.) and −

112°

C. (−

170°

F.).

4. The method of claim 1 wherein the absorption medium is lean oil.

5. The method of claim 1 wherein the absorption medium is pre-saturated with methane prior to treatment step (b).

6. The method of claim 1 wherein the heat exchange relationship uses a heat-transfer medium being in heat exchange relationship with the liquid mixture in a first heat exchanger and the heat transfer medium being in heat exchange relationship with the absorption stream in a second heat exchanger.

7. The method of claim 1 wherein the heat exchange relationship uses at least one heat exchanger in which the liquid mixture is in indirect contact with the absorption medium.

8. The method of claim 1 further comprises, before passing the pressurized liquid mixture in heat exchange relationship with a heat-transfer stream, heating the liquid mixture by heat exchange relationship with at least one of air, fresh water, and sea water.

9. The method of claim 1 further comprises, after passing the pressurized liquid mixture in heat exchange relationship with a heat-transfer stream, further heating the liquid mixture by heat exchange relationship with at least one of air, fresh water, and sea water.

10. A method for separating C₂₊ components from a pressurized liquid mixture comprising C₁ and C₂₊, the method comprising:

(a) heating the pressurized liquid mixture to at least partially vaporize the liquid mixture, thereby producing a vapor stream;

(b) contacting the vapor stream with an absorbent medium that preferentially absorbs C₂₊ components from the vapor stream;

(c) recovering a C₁-rich stream substantially depleted of C₂₊;

(d) separating the extracted C₂₊ components from the absorption medium containing the same;

(e) cooling at least part of the absorption medium by heat exchange relationship against the pressurized liquid mixture, thereby providing heat for at least partially vaporizing the liquid mixture; and

(f) recycling the cooled absorption medium to absorb additional amounts of C₂₊ components.