Process and apparatus for separation of hydrocarbons

• US 7,357,003 B2
• Filed: 06/28/2004
• Issued: 04/15/2008
• Est. Priority Date: 07/24/2003
• Status: Active Grant

• Current Assignee: TOYO Engineering Corporation
• Original Assignee: TOYO Engineering Corporation
• Inventors: Yamamori, Yasuyuki, Evelyne, Jahja, Yamaguchi, Shoichi, Ohara, Susumu
• Primary Examiner(s): Doerrler; William C
• Application Number:
  US10/506,241
• Publication Number:
  US 20050155382A1
• Time in Patent Office: 1,387 Days
• Field of Search: 626/20, 626/21
• US Class Current: 62/620
• CPC Class Codes: B01D 2257/702 Hydrocarbons
• CPC Class Codes: B01D 53/002 by condensation
• CPC Class Codes: C10G 5/06 by cooling or compressing
• CPC Class Codes: C10L 3/10 Working-up natural gas or synthetic natural gas
• 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 2205/04 in the feed line, i.e. upstream of the fractionation step
• 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 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 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

Abstract

There are provided a process for separation of hydrocarbons including the steps of: (a) a feed gas is cooled and partly condensed, and separated into a gas and a liquid; (b) the liquid obtained in step (a) is supplied to a distillation column; (c) the gas obtained in step (a) is expanded by an expander and partly condensed, and separated into a gas and a liquid; (d) the liquid obtained in step (c) is supplied to the distillation column; (e) the gas obtained in step (c) is divided into a first portion and a second portion; (f) the first portion is supplied to the distillation column; (g) the second portion is condensed by being compressed and cooled, and then depressurized and supplied as a reflux to the distillation column; and (h) a residue gas is obtained from the top part of the distillation column and a heavier fraction is obtained from the bottom part of the distillation column; and an apparatus therefor. The process and apparatus enable efficient separation of hydrocarbons.

Claims

1. A process for separation of hydrocarbons to separate a feed gas comprising at least methane and a hydrocarbon less volatile than methane, in a distillation column, into a residue gas enriched with methane and lean in the hydrocarbon less volatile than methane and a heavier fraction lean in methane and enriched with the hydrocarbon less volatile than methane, comprising the steps of:

(a) said feed gas is cooled and partly condensed, and separated into a gas and a liquid;

(b) the liquid obtained in step (a) is supplied to a distillation column;

(c) the gas obtained in step (a) is expanded by an expander and partly condensed, and separated into a gas and a liquid;

(d) the liquid obtained in step (c) is supplied to the distillation column;

(e) the gas obtained in step (c) is divided into a first gas portion and a second gas portion;

(f) said first gas portion is supplied to the distillation column;

(g) said second gas portion is condensed by being compressed and cooled, and then depressurized and supplied as a reflux to the distillation column; and

(h) said residue gas enriched with methane and lean in the hydrocarbon less volatile than methane is obtained from the top part of the distillation column and said heavier fraction lean in methane and enriched with the hydrocarbon less volatile than methane is obtained from the bottom part of the distillation column.

3. A process according to claim 1, wherein said residue gas enriched with methane and lean in the hydrocarbon less volatile than methane is used as a cooling medium in cooling in step (g).

2. A process for separation of hydrocarbons to separate a feed gas comprising at least ethane and a hydrocarbon less volatile than ethane, in a distillation column, into a residue gas enriched with ethane and lean in the hydrocarbon less volatile than ethane and a heavier fraction lean in ethane and enriched with the hydrocarbon less volatile than ethane, comprising the steps of:

(a) said feed gas is cooled and partly condensed, and separated into a gas and a liquid;

(b) the liquid obtained in step (a) is supplied to a distillation column;

(c) the gas obtained in step (a) is expanded by an expander and partly condensed, and separated into a gas and a liquid;

(d) the liquid obtained in step (c) is supplied to the distillation column;

(e) the gas obtained in step (c) is divided into a first gas portion and a second gas portion;

(f) said first gas portion is supplied to the distillation column;

(g) said second gas portion is condensed by being compressed and cooled, and then depressurized and supplied as a reflux to the distillation column;

(h) said residue gas enriched with ethane and lean in the hydrocarbon less volatile than ethane is obtained from the top part of the distillation column and said heavier fraction lean in ethane and enriched with the hydrocarbon less volatile than ethane is obtained from the bottom part of the distillation column.

7. A process according to claim 2, wherein said residue gas enriched with ethane and lean in the hydrocarbon less volatile than ethane is used as a cooling medium in cooling in step (g).

4. An apparatus for separation of hydrocarbons to separate a feed gas containing at least methane and a hydrocarbon less volatile than methane into a residue gas enriched with methane and lean in the hydrocarbon less volatile than methane and a heavier fraction lean in methane and enriched with the hydrocarbon less volatile than methane, comprising:

a distillation column for discharging said residue gas enriched with methane and lean in the hydrocarbon less volatile than methane from the top part and discharging said heavier fraction lean in methane and enriched with the hydrocarbon less volatile than methane from the bottom part;

a cooling and separating means for cooling said feed gas to condense a part thereof, and for separating the partly condensed feed gas into a gas and a liquid;

a line for supplying the liquid obtained by the cooling and separating means to the distillation column;

an expander for expanding the gas obtained by the cooling and separating means to condense a part thereof;

a gas-liquid separator connected to the outlet of the expander;

a line for supplying the condensate obtained by the gas-liquid separator to the distillation column;

a dividing means for dividing the gas obtained by the gas-liquid separator into a first gas portion and a second gas portion;

a line for supplying said first gas portion to the distillation column;

a compressing means for compressing said second gas portion;

a cooling means for cooling and condensing the gas compressed by the compressing means;

a pressure-reducing means for depressurizing the condensate obtained by the cooling means; and

a line for supplying the condensate depressurized by the pressure-reducing means to the distillation column as a reflux.

6. An apparatus according to claim 4, wherein said cooling means includes a heat exchanger of which cooling medium is the residue gas enriched with methane and lean in the hydrocarbon less volatile than methane withdrawn from the top part of said distillation column.

5. An apparatus for separation of hydrocarbons to separate a feed gas containing at least ethane and a hydrocarbon less volatile than ethane into a residue gas enriched with ethane and lean in the hydrocarbon less volatile than ethane and a heavier fraction lean in ethane and enriched with the hydrocarbon less volatile than ethane, comprising:

a distillation column for discharging said residue gas enriched with ethane and lean in the hydrocarbon less volatile than ethane from the top part and discharging said heavier fraction lean in ethane and enriched with the hydrocarbon less volatile than ethane from the bottom part;

a cooling and separating means for cooling said feed gas to condense a part thereof, and for separating the partly condensed feed gas into a gas and a liquid;

a line for supplying the liquid obtained by the cooling and separating means to the distillation column;

an expander for expanding the gas obtained by the cooling and separating means to condense a part thereof;

a gas-liquid separator connected to the outlet of the expander;

a line for supplying the condensate obtained by the gas-liquid separator to the distillation column;

a dividing means for dividing the gas obtained by the gas-liquid separator into a first portion and a second portion;

a line for supplying said first portion to the distillation column;

a compressing means for compressing said second portion;

a cooling means for cooling and condensing the gas compressed by the compressing means;

a pressure-reducing means for depressurizing the condensate obtained by the cooling means; and

a line for supplying the condensate depressurized by the pressure-reducing means to the distillation column as a reflux.

8. An apparatus according to claim 5, wherein said cooling means includes a heat exchanger of which cooling medium is the residue gas enriched with ethane and lean in the hydrocarbon less volatile than ethane withdrawn from the top part of said distillation column.