Split feed compression process for high recovery of ethane and heavier components

• US 6,354,105 B1
• Filed: 06/16/2000
• Issued: 03/12/2002
• Est. Priority Date: 12/03/1999
• Status: Expired due to Term

• Current Assignee: IPSI, LLC (Bechtel Group Incorporated)
• Original Assignee: IPSI, LLC (Bechtel Group Incorporated)
• Inventors: Elliot, Douglas G., Chen, Jong Juh, Jain, Pallav, Yao, Jame, Lee, Rong-Jwyn
• Primary Examiner(s): DOERRLER, WILLIAM CHARLES
• Application Number:
  US09/596,398
• Time in Patent Office: 634 Days
• Field of Search: 626/19, 626/20, 626/47
• US Class Current: 62/619
• CPC Class Codes: F25J 2200/02 in a single 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 2210/06 Splitting of the feed stream, e.g. for treating or cooling in different ways
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• 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 2235/60 the fluid being (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 2270/60 Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons
• CPC Class Codes: F25J 2270/88 Quasi-closed internal refrigeration or heat pump cycle, if not otherwise provided
• CPC Class Codes: F25J 2270/90 External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
• CPC Class Codes: F25J 2290/40 Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.
• CPC Class Codes: F25J 2290/80 Retrofitting, revamping or debottlenecking of existing plant
• CPC Class Codes: F25J 3/0209 Natural gas or substitute natural gas
• CPC Class Codes: F25J 3/0219 Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
• 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

Abstract

A process for enhancing recovery of ethylene, ethane and heavier components using a cryogenic distillation column which involves dividing the feed gas into a first gaseous stream and a main gaseous stream. The first gaseous stream is compressed and cooled, and then expanded and introduced into the cryogenic distillation column as main reflux stream, or is further processed to generate at least one reflux stream to the cryogenic distillation column.

Claims

1. A process for recovering relatively less volatile components from a gas mixture while rejecting relatively more volatile components as residue gas via a cryogenic distillation column wherein its reflux stream is generated by the steps comprising:

a) dividing a vapor portion of said gas mixture into a first gaseous stream and a main gaseous stream;

b) compressing said first gaseous stream and cooling it to produce a cooled, compressed first gaseous stream;

c) further handling cooled, compressed first gaseous stream as selected from the group consisting of

i) feeding cooled, compressed first gaseous stream as a reflux stream directly to said cryogenic distillation column, and

ii) further processing cooled, compressed first gaseous stream to generate at least one reflux stream for said cryogenic distillation column; and

d) cooling said main gaseous stream and separating it into a first liquid phase comprising condensed components, if any, and into a first vapor phase; and

thereafter introducing said first liquid phase and said first vapor phase into said cryogenic distillation column at one or more feed trays.

2. The process of claim 1 wherein at least a portion of the refrigeration for cooling said main gaseous stream or compressed first gaseous stream is provided by an external refrigeration system.

3. The process of claim 1 wherein at least part of said cooling is accomplished by a refrigeration stream withdrawn from said cryogenic distillation column;

the cooling resulting in partial vaporization of said refrigerant stream.

4. The process of claim 3 further comprising separating said partially vaporized refrigerant stream into a second gas phase which is introduced into said cryogenic distillation column, and a second liquid phase.

5. A process for recovering relatively less volatile components from a gas mixture while rejecting relatively more volatile components as residue gas via a cryogenic distillation column wherein its reflux stream is generated by the steps comprising:

a) cooling said gas mixture and thereafter separating said cooled gas mixture into a first vapor stream and a condensed gas mixture stream, if any;

b) dividing said first vapor stream into a first gaseous stream and a main gaseous stream;

c) compressing said first gaseous stream and then cooling it to produce a cooled, compressed first gaseous stream; and

d) further handling cooled, compressed first gaseous stream as selected from the group consisting of

i) feeding cooled, compressed first gaseous stream as a reflux stream directly to said cryogenic distillation column, and

ii) further processing cooled, compressed first gaseous stream to generate at least one reflux stream for said cryogenic distillation column.

6. The process of claim 5 wherein at least a portion of the refrigeration for cooling said gas mixture or compressed first gaseous stream is provided by an external refrigeration system.

7. The process of claim 5 wherein at least part of said cooling is accomplished by a refrigeration stream withdrawn from said cryogenic distillation column;

the cooling resulting in partial vaporization of said refrigerant stream.

8. The process of claim 7 further comprising separating said partially vaporized refrigerant stream into a second gas phase which is introduced into said cryogenic distillation column, and a second liquid phase.

9. The process of claim 5 wherein no condensed gas mixture stream is obtained during said cooling step a) and no separation of said cooled gas mixture occurs.

10. The process of claim 9 wherein at least a portion of the refrigeration for cooling said gas mixture or compressed first gaseous stream is provided by an external refrigeration system.

11. The process of claim 9 wherein at least part of said cooling is accomplished by a refrigeration stream withdrawn from said cryogenic distillation column;

the cooling resulting in partial vaporization of said refrigerant stream.

12. The process of claim 11 further comprising separating said partially vaporized refrigerant stream into a second gas phase which is introduced into said cryogenic distillation column, and a second liquid phase.

13. The process of claim 5 further comprising introducing said main gaseous stream and condensed feed gas stream into said cryogenic distillation column at one or more feed trays.

14. In an apparatus for recovering relatively less volatile components from a gas mixture while rejecting relatively more volatile components as residue gas via a cryogenic distillation column, the apparatus comprising:

a) means for dividing a vapor portion of said gas mixture into a first gaseous stream and a main gaseous stream;

b) a compressor for increasing the pressure of said first gaseous stream;

c) means for cooling and at least partially condensing said compressed first gaseous stream;

d) a cryogenic distillation column having a plurality of feed trays and recovery stages, which receives said cooled, compressed, at least partially condensed first gaseous stream as reflux stream to enhance recovery of relatively less volatile components;

e) means for cooling said main gaseous stream;

f) a separator for separating said cooled main gaseous stream into a first liquid phase comprising condensed components, if any, and into a first vapor phase; and

g) means for introducing said first liquid phase and said first vapor phase into said cryogenic distillation column at one or more feed trays;

where the c) means for cooling and condensing said compressed first gaseous stream may be the same or different as e).

15. The apparatus of claim 14 further comprising a device to further process said cooled, compressed first gaseous stream to generate at least one reflux stream for said cryogenic distillation column.

16. The apparatus of claim 14 further comprising means for cooling said gas mixture prior to a) means for dividing said vapor portion of said gas mixture.

17. In an apparatus for recovering relatively less volatile components from a gas mixture while rejecting relatively more volatile components as residue gas via a cryogenic distillation column, the apparatus comprising:

a) means for cooling said gas mixture;

b) a separator for separating said cooled gas mixture into a first vapor stream and a condensed gas mixture stream, if any;

c) means for dividing said first vapor stream into a first gaseous stream and a main gaseous stream;

d) a compressor for increasing the pressure of said first gaseous stream;

e) means for cooling and at least partially condensing said compressed first gaseous stream; and

f) a cryogenic distillation column having a plurality of feed trays and recovery stages, which receives said cooled, compressed, partially condensed first gaseous stream as reflux stream to enhance recovery of relatively less volatile components.

18. The apparatus of claim 17 further comprising a device to further process said cooled, compressed first gaseous stream to generate at least one reflux stream for said cryogenic distillation column.