CONFIGURATIONS AND METHODS OF INTEGRATED NGL RECOVERY AND LNG LIQUEFACTION

• US 20130061633A1
• Filed: 11/08/2012
• Published: 03/14/2013
• Est. Priority Date: 07/07/2005
• Status: Abandoned Application

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John, Graham, Curt
• Application Number:
  US13/672,602
• Publication Number:
  US 20130061633A1
• Time in Patent Office: Days
• US Class Current: 62/613
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/0035 by gas expansion with extraction of work
• CPC Class Codes: F25J 1/0045 by vaporising a liquid return stream
• CPC Class Codes: F25J 1/0052 by vaporising a liquid refrigerant stream
• CPC Class Codes: F25J 1/0207 as at least a three level SCR refrigeration cascade
• CPC Class Codes: F25J 1/0218 with one or more SCR cycles, e.g. with a C3 pre-cooling cycle
• CPC Class Codes: F25J 1/0231 for the working-up of the hydrocarbon feed, e.g. reinjection of heavier hydrocarbons into the liquefied gas
• CPC Class Codes: F25J 1/0239 Purification or treatment step being integrated between two refrigeration cycles of a refrigeration cascade, i.e. first cycle providing feed gas cooling and second cycle providing overhead gas cooling
• CPC Class Codes: F25J 1/0291 Refrigerant compression by combined gas compression and liquid pumping
• CPC Class Codes: F25J 1/0292 Refrigerant compression by cold or cryogenic suction of the refrigerant gas
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/04 in a dual 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 2200/72 Refluxing the column with at least a part of the totally condensed overhead gas
• CPC Class Codes: F25J 2200/78 Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2215/02 Mixing or blending of fluids to yield a certain product
• CPC Class Codes: F25J 2215/62 Ethane or ethylene
• CPC Class Codes: F25J 2220/62 Separating low boiling components, e.g. He, H2, N2, Air
• CPC Class Codes: F25J 2230/08 Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
• CPC Class Codes: F25J 2230/60 : the fluid being hydrocarbons or a mixture of hydrocarbons
• CPC Class Codes: F25J 2240/02 : Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• CPC Class Codes: F25J 2245/02 : Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2270/02 : Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/12 : External refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/60 : Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons
• CPC Class Codes: F25J 2270/66 : Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
• CPC Class Codes: F25J 3/0209 : Natural gas or substitute 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

Contemplated plants include a NGL recovery portion and a LNG liquefaction portion, wherein the NGL recovery portion provides a low-temperature and high-pressure overhead product directly to the LNG liquefaction portion. Feed gas cooling and condensation are most preferably performed using refrigeration cycles that employ refrigerants other than the demethanizer/absorber overhead product. Thus, cold demethanizer/absorber overhead product is compressed with the turbo-expansion and delivered to a liquefaction portion at significantly lower temperature and higher pressure without net compression energy expenditure.

Claims

1. A method of producing a liquefied natural gas (LNG) from a natural gas feed stream, comprising:

providing the natural gas stream at a pressure of between 800 and 1600 psig, and cooling the natural gas stream using a feed gas pre-cooling circuit to form a vapor portion and a liquid portion of the cooled natural gas stream;

expanding the vapor portion of the natural gas stream in an expander to form an expanded natural gas vapor, and feeding the expanded natural gas vapor to a separator;

producing a cold overhead product stream in the separator, wherein the separator receives a reflux stream that is cooled in a reflux refrigeration circuit;

compressing the cold overhead product stream in a compressor without prior substantial heating of the cold product stream, wherein the compressor is driven by the expander, and wherein the compressed cold product stream has a pressure of at least 700 psig and a temperature of less than −

50°

F.;

liquefying the cold compressed product stream in a liquefaction unit using refrigeration content from a liquefaction refrigeration circuit; and

wherein the feed gas pre-cooling circuit, the reflux refrigeration circuit, and the liquefaction refrigeration circuit are distinct circuits.

2. The method of claim 1 further comprising a step of feeding the liquid portion of the cooled natural gas stream to the separator and operating the separator as a demethanizer.

3. The method of claim 1 further comprising a step of feeding a bottom product of the separator to a deethanizer, wherein the deethanizer optionally provides a C2 product to the cold overhead product stream of the separator.

4. The method of claim 1 wherein the separator is operated as a refluxed absorber.

5. The method of claim 1 further comprising a step of providing a reflux stream from a demethanizer to the absorber, and providing a bottom product of the absorber to the demethanizer, and operating the demethanizer at a lower pressure than the absorber.

6. The method of claim 5 further comprising a step of heating the absorber bottom product for C2 rejection prior to entering the demethanizer.

7. The method of claim 5 further comprising a step of cooling the absorber bottom product for C2 recovery prior to entering the demethanizer.

8. The method of claim 5 further comprising a step of feeding a bottom product of the demethanizer to a deethanizer for C2 and C3+ recovery.

9. The method of claim 1 wherein the feed gas pre-cooling circuit is operated at a temperature range of 10°

F. to −

35°

F., wherein the reflux refrigeration circuit is operated at a temperature range of −

60°

F. to −

160°

F., and wherein the liquefaction refrigeration circuit is operated at a temperature range of −

180°

F. to −

270°

F.

10. A method of producing LNG comprising:

separating in a separator a cold overhead product from a natural gas containing feed gas;

compressing the cold overhead product using expansion energy from the feed gas to form a cold compressed overhead product at a pressure of at least 700 psig and a temperature of less than −

50°

F.;

feeding the cold compressed overhead product to a liquefaction unit; and

wherein the cold compressed overhead product is formed at neutral or negative net compression energy requirement.

11. The method of claim 10 wherein the step of separating is performed in an absorber or a demethanizer.

12. The method of claim 10 wherein the feed gas has a pressure of between 800 and 1600 psig.

13. The method of claim 10 wherein the separator is a refluxed demethanizer or refluxed absorber.

14. The method of claim 10 wherein the feed gas is cooled in a feed gas pre-cooling circuit, wherein the reflux for the refluxed demethanizer or refluxed absorber is cooled in a reflux refrigeration circuit, wherein the liquefaction unit uses refrigeration content from a liquefaction refrigeration circuit, and wherein the feed gas pre-cooling circuit, the reflux refrigeration circuit, and the liquefaction refrigeration circuit are distinct circuits.