Method for cold supply to the low-temperature separation stage of an olefin plant

• US 7,554,002 B2
• Filed: 02/07/2007
• Issued: 06/30/2009
• Est. Priority Date: 02/08/2006
• Status: Active Grant

• Current Assignee: Linde AG (Linde Plc)
• Original Assignee: Linde AG (Linde Plc)
• Inventors: Pham Duc, Tuat
• Primary Examiner(s): PARSA, JAFAR F
• Application Number:
  US11/703,213
• Publication Number:
  US 20070199865A1
• Time in Patent Office: 874 Days
• Field of Search: 585/800, 585/802, 585/809
• US Class Current: 585/802
• CPC Class Codes: C07C 11/04 Ethylene
• CPC Class Codes: C07C 11/06 Propene
• CPC Class Codes: C07C 7/09 by fractional condensation
• CPC Class Codes: C10G 2400/20 C2-C4 olefins
• CPC Class Codes: C10G 70/043 by fractional condensation
• CPC Class Codes: F25J 2200/94 Details relating to the withdrawal point
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2205/82 using a reactor with combustion or catalytic reaction
• CPC Class Codes: F25J 2210/04 Mixing or blending of fluids with the feed stream
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2215/62 Ethane or ethylene
• 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 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
• CPC Class Codes: F25J 3/0242 separation of CnHm with 3 carbon atoms or more
• CPC Class Codes: F25J 3/0252 separation of hydrogen production of hydrogen containing gas in general C01B3/00, e.g. separation of hydrogen or hydrogen containing gases form gaseous mixtures at low temperatures C01B3/506
• CPC Class Codes: Y02P 30/40 Ethylene production

Abstract

A method is described for refrigerant supply of a low-temperature separation stage in a plant for producing olefins from hydrocarbon-containing feed (olefin plant). During the separation sequence beginning with a front end deethanizer (3) downstream of raw gas compressor (1), precooler and dryer (2), first separation is performed into an olefin fraction having at most two carbon atoms and an olefin fraction having at least three carbon atoms. The fraction having at least three carbon atoms is conducted to the further separation sequence for longer-chain olefins (4). The fraction having at most two carbon atoms is conducted via a catalytic hydrogenation stage (5) connected in between to the low-temperature separation stage (6) which comprises three condensation stages in the temperature range from −50° C. to −100° C. From the low-temperature separation stage, gaseous hydrogen (9) and methane (10) are drawn off, while the olefins having at most two carbon atoms are conducted to a further fractionation stage (7). The refrigeration power for the low-temperature separation stage is provided by the vaporization via heat exchangers of a portion of the liquid ethylene fraction (8) resulting in the front end deethanizer. The vaporized ethylene fraction is recirculated to the raw gas compressor (11).

Claims

1. A method for producing olefins from hydrocarbon-containing feed using a refrigerant and a low-temperature separation stage, said method comprising:

introducing a hydrocarbon feed containing olefins into a fractionation stage which is a front end deethanizer which separates the hydrocarbon feed into a first olefin stream containing olefins having at most two carbon atoms, and a second olefin stream containing olefins having at least three carbon atoms; and

introducing at least a portion of said first olefin stream into a low-temperature separation stage comprising three condensation stages, operating at temperatures of −

50°

C. to −

100°

C., said low-temperature separation stage being connected downstream of said front end deethanizer, wherein the refrigerant used in said three condensation stages consists essentially of a liquid olefin fraction having two carbon atoms removed from said front end deethanizer, and wherein said method omits a compressor cycle for ethylene refrigerant for said condensation stages.

2. A method according to claim 1, wherein said liquid olefin fraction having two carbon atoms is vaporized via countercurrent flow heat exchangers in said condensation stages.

3. A method according to claim 2, wherein said olefin fraction having two carbon atoms which is vaporized in the countercurrent flow heat exchangers is recirculated to a compressor stage upstream of said front end deethanizer.

4. A method according to claim 1, further comprising a catalytic hydrogenation stage connected between said front end deethanizer and said low-temperature separation stage.

5. A method according to claim 2, further comprising a catalytic hydrogenation stage connected between said front end deethanizer and said low-temperature separation stage.

6. A method according to claim 3, further comprising a catalytic hydrogenation stage connected between said front end deethanizer and said low-temperature separation stage.

7. A method for producing olefins from hydrocarbon-containing feed using a refrigerant and a low-temperature separation stage, said method comprising:

compressing a hydrocarbon feed containing olefins a gas compressor (1), introducing resultant compressed hydrocarbon feed in a precooler and dryer (2), and introducing the pre-cooled, compressed hydrocarbon feed into a front end deethanizer (3) which separates the hydrocarbon feed into a first olefin stream containing olefins having at most two carbon atoms, and a second olefin stream containing olefins having at least three carbon atoms;

introducing a portion of said first olefin stream containing olefins having at most two carbon atoms into a catalytic hydrogenation stage (5);

introducing resultant effluent from said catalytic hydrogenation stage (5) to a low-temperature separation stage (6) comprising three condensation stages operating at temperatures of −

50°

C. to −

100°

C., wherein the refrigerant used in said low-temperature separation stage consists essentially of a liquid olefin fraction (8) obtained from said front end deethanizer (3);

recycling vaporized liquid olefin fraction (11) from said low-temperature separation stage (6) to said gas compressor (1);

removing a hydrogen stream and a methane stream from said low-temperature separation stage (6), and introducing effluent from said low-temperature separation stage (6) to a fractionation stage (7) which separates methane from olefins having two carbon atoms, and removing a methane stream and an olefin stream from said fractionation stage (7) and wherein said method omits a compressor cycle for ethylene refrigerant for said condensation stages.

8. A method according to claim 7, wherein said liquid olefin fraction having two carbon atoms is vaporized via countercurrent flow heat exchangers in said condensation stages.

9. A method according to claim 8, wherein said liquid olefin fraction having two carbon atoms which is vaporized in the countercurrent flow heat exchangers is recirculated to a compressor stage upstream of said front end deethanizer.