Cryogenic process for increased recovery of hydrogen

• US 6,931,889 B1
• Filed: 04/21/2003
• Issued: 08/23/2005
• Est. Priority Date: 04/19/2002
• Status: Active Grant

• Current Assignee: ABB LUMUS GLOBAL, RANDALL GAS TECHNOLOGIES
• Original Assignee: ABB Lummus Global-Randall Gas Technologies
• Inventors: Yamin, Fereidoun, Milios, Paul, Foglietta, Jorge H.
• Primary Examiner(s): DOERRLER, WILLIAM CHARLES
• Application Number:
  US10/419,579
• Time in Patent Office: 855 Days
• Field of Search: 626/18, 626/19, 626/20, 626/22
• 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 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2270/04 Internal refrigeration with work-producing gas expansion 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 2270/90 External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
• 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 3/0242 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: F25J 3/062 Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
• CPC Class Codes: F25J 3/0635 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0655 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

Abstract

A cryogenic process and apparatus to recover hydrogen from a fuel gas stream. The process can be stand alone or can be combined with existing processes, such as recovery of LPG from a fuel gas stream. In the stand-alone process, the fuel gas is cooled in one or more stages and sent to a cold separator that is used to separate the feed into a liquid and vapor stream. The liquid stream, is then warmed, compressed and then cooled and sent for further processing. The vapor stream, which contains hydrogen, is compressed, cooled when needed, and then returned for use in the existing facility or exported. The stand-alone process can be integrated within an LPG recovery process. The result of this cryogenic process is recovery of hydrogen from a fuel gas stream with only a slight decrease in hydrogen purity.

Claims

1. A process for recovering hydrogen from a fuel gas stream by means of a stand-alone cryogenic process comprising the steps of:

supplying and cooling and at least partially condensing a feed gas stream;

separating the feed gas stream into a first vapor stream and a first liquid stream;

expanding and thereby decreasing a pressure of the first vapor stream to produce an expanded stream;

heating the expanded stream thereby producing a warmed vapor stream;

compressing the warmed vapor stream to produce a product hydrogen stream;

heating the first liquid stream and at least partially vaporizing the first liquid stream to produce a second vapor stream; and

compressing and cooling the second vapor stream to produce a fuel gas stream substantially free of hydrogen,

whereby the cryogenic process is a stand-alone process.

2. The process according to claim 1, wherein the step of cooling the feed gas stream includes cooling the feed gas stream by heat exchange contact with a process stream selected from the group consisting of the first liquid stream, the product hydrogen stream, an external refrigerant stream, and combinations thereof.

3. A process for recovering hydrogen from a fuel gas stream by means of a stand-alone cryogenic process comprising the steps of:

supplying and cooling and at least partially condensing a feed gas stream;

separating the feed gas stream into a first vapor stream and a first liquid stream;

cooling and at least partially condensing the first vapor stream and separating the first vapor stream into a second vapor stream and a second liquid stream;

expanding and thereby decreasing a pressure of the second vapor stream to produce an expanded stream;

heating the expanded stream thereby producing a warmed vapor stream;

compressing the warmed vapor stream to produce a product hydrogen stream;

heating the first liquid stream and the second liquid stream and at least partially vaporizing the first liquid stream and the second liquid stream to produce a third vapor stream; and

compressing and cooling the third vapor stream to produce a fuel gas stream substantially free of hydrogen,

whereby the cryogenic process is a stand-alone process.

4. The process according to claim 3, wherein the step of cooling the feed gas stream includes cooling the feed gas stream by heat exchange contact with a process stream selected from the group consisting of the first liquid stream, the product hydrogen stream, an external refrigerant stream, and combinations thereof.

5. The process according to claim 3, wherein the step of cooling the first vapor stream includes cooling the feed gas stream by heat exchange contact with a process stream selected from the group consisting of the second liquid stream, the product hydrogen stream, an external refrigerant stream, and combinations thereof.

6. A process for recovering hydrogen and liquefied petroleum gases (LPG) from a fuel gas stream by means of a cryogenic process comprising the steps of:

supplying and cooling and at least partially condensing a feed gas stream;

separating the feed gas stream into a first vapor stream and a first liquid stream;

cooling and at least partially condensing the first vapor stream to produce a cooled stream;

separating the cooled stream into a second vapor stream and a second liquid stream;

expanding and thereby decreasing a pressure of the second vapor stream to produce an expanded stream;

separating the expanded stream into a third vapor stream and a third liquid stream;

warming the third vapor stream thereby producing a warmed vapor stream and compressing and cooling the warmed vapor stream to produce a hydrogen product stream that can be sent for further processing;

heating the third liquid stream thereby vaporizing at least a portion of the third liquid stream thereby producing a first tower feed stream and supplying the first tower feed stream to a first stage of a reboiled absorber;

heating the second liquid stream and vaporizing at least a portion of the second liquid stream thereby producing a second tower feed stream and supplying the second tower feed stream to the reboiled absorber;

heating the first liquid stream and vaporizing at least a portion of the first liquid stream thereby producing a third tower feed stream and supplying the third tower feed stream to the reboiled absorber;

separating the first, second, and third feed streams to produce a tower bottoms stream and a tower overhead stream;

cooling the tower bottoms stream thereby producing an LPG product stream that contains substantially at least 70% of propane (C3) and heavier compounds; and

heating and compressing and then cooling the tower vapor stream that contains a fuel gas stream substantially free of hydrogen, which is sent for further processing.

7. The process of claim 6, wherein the step of cooling the feed gas stream includes heat exchanging the feed gas stream with a process stream selected from the group consisting of the first liquid stream, the second liquid stream, the third liquid stream, the third vapor stream, the tower overhead stream, an external refrigerant stream, and combinations thereof.

8. A process according to claim 6, wherein the step of cooling the first vapor stream to produce a cooled stream including heat exchanging the first vapor stream with a process stream selected from the group consisting of the second liquid stream, the third liquid stream, the third vapor stream, an external refrigerant stream, and combinations thereof.

9. A process according to claim 6, wherein the second tower feed stream is fed to the reboiled absorber at a lower feed tray than the first tower feed stream.

10. A process according to claim 6, wherein the step of warming the tower overhead stream includes warming the tower overhead stream by heat exchange contact with a stream selected from the group consisting of the third vapor stream, the feed gas stream, the first liquid stream, the second liquid stream, the third liquid stream, an external cooling stream, and combinations thereof.

11. A process according to claim 6, wherein the step of supplying the reboiled absorber with the first, second, and third feed stream includes supplying the reboiled absorber with the first, second, and third feed streams independently.

12. A process according to claim 6, wherein the step of supplying the reboiled absorber with the first, second, and third feed streams includes combining one or more of the first, second, and third feed streams prior to supplying the first, second, and third streams to the reboiled absorber.

13. A process for recovering hydrogen and liquefied petroleum gases (LPG) from a fuel gas stream by means of a cryogenic process comprising the steps of:

supplying and cooling and at least partially condensing a feed gas stream;

separating the feed gas stream into a first vapor stream and a first liquid stream;

cooling and at least partially condensing the first vapor stream to produce a cooled stream;

separating the cooled stream into a second vapor stream and a second liquid stream;

expanding and thereby decreasing a pressure of the second vapor stream to produce an expanded stream;

separating the expanded stream into a third vapor stream and a third liquid stream;

warming the third vapor stream thereby producing a warmed vapor stream and compressing and cooling the warmed vapor stream to produce a hydrogen product stream that can be sent for further processing;

heating the third liquid stream thereby vaporizing at least a portion of the third liquid stream thereby producing a first feed stream and supplying the first feed stream to a fractionation tower;

heating the second liquid stream and vaporizing at least a portion of the second liquid stream thereby producing a second feed stream and supplying the second feed stream to the fractionation tower;

heating the first liquid stream and vaporizing at least a portion of the first liquid stream thereby producing a third feed stream and supplying the third feed stream to the fractionation tower;

separating the first, second, and third feed streams within the fractionation tower to produce a fractionation tower bottoms stream and a fractionation tower overhead stream;

cooling the fractionation tower bottoms stream thereby producing an LPG product stream that contains substantially at least 90% of propane (C3) and heavier compounds;

cooling and at least partially condensing the fractionation tower overhead stream thereby producing a partially condensed fractionation tower stream;

separating the condensed fractionation tower stream into a fractionation tower reflux stream that is sent back to the fractionation tower and a fractionation tower vapor stream; and

warming and compressing and then cooling the fractionation tower vapor stream that contains a fuel gas stream substantially free of hydrogen, which is sent for further processing.

14. The process of claim 13, wherein the step of cooling the feed gas stream includes cooling the feed gas stream by heat exchange contact with a process stream selected from the group consisting of the first liquid stream, the second liquid stream, the third liquid stream, the third vapor stream, the tower overhead stream, an external refrigerant stream, and combinations thereof.

15. A process according to claim 13, wherein the step of cooling the first vapor stream to produce a cooled stream includes cooling the first vapor stream by heat exchange contact with a process stream selected from the group consisting of the second liquid stream, the third liquid stream, the third vapor stream, an external refrigerant stream, and combinations thereof.

16. A process according to claim 13, wherein the second feed stream is typically fed to the fractionation tower at a lower feed tray than the first feed stream.

17. A process according to claim 13, wherein the step of warming the fractionation tower vapor stream includes warming the fractionation tower vapor stream by heat exchange contact with a stream selected from the group consisting of the third vapor stream, the feed gas stream, the first liquid stream, the second liquid stream, the third liquid stream, an external cooling stream, and combinations thereof.

18. A process according to claim 13, wherein the step of supplying the fractionation tower with the first, second, and third feed streams includes supplying the fractionation tower with the first, second, and third feed streams independently.

19. A process according to claim 13, wherein the step of supplying the fractionation tower with the first, second, and third feed streams includes combining one or more of the first, second, and third feed streams prior to supplying the first, second, and third streams to the fractionation tower.

20. An apparatus for recovering hydrogen from a fuel gas stream by means of a cryogenic process comprising:

a first cooler for cooling and at least partially condensing a feed gas stream;

a separator for separating the feed gas stream into a first vapor stream and a first liquid stream;

an expander for expanding and thereby decreasing a pressure of the first vapor stream to produce an expanded stream;

a first heater for heating the expanded stream thereby producing a warmed vapor stream;

a first compressor for compressing the warmed vapor stream to produce a product hydrogen stream;

a second heater for heating the first liquid stream and at least partially vaporizing the first liquid stream to produce a second vapor stream; and

a second compressor for compressing and a second cooler for cooling the second vapor stream to produce a fuel gas stream substantially free of hydrogen,

whereby the cryogenic process is a stand-alone process.

21. The apparatus according to claim 20, wherein the first cooler, first heater, and second heater comprise a single heat exchanger for performing a heat exchanger task selected from the group consisting of cooling the feed gas stream, heating the expanded stream, heating the first liquid stream, and combinations thereof.

22. The apparatus according to claim 20, further including a third cooler for cooling and at least partially condensing the first vapor stream and a second separator for separating the first vapor stream into a second vapor stream and a second liquid stream and wherein the expander expands the second vapor stream and the second heater heats and at least partially vaporizes the second liquid stream.

23. An apparatus for recovering hydrogen and liquefied petroleum gases (LPG) from a fuel gas stream by means of a cryogenic process comprising:

a first heat exchanger for performing heat exchange tasks selected from the group consisting of cooling and at least partially condensing a feed gas stream, heating and at least partially vaporizing a first liquid stream to produce a third tower feed stream, heating and at least partially vaporizing a second liquid stream to produce a second tower feed stream, heating and at least partially vaporizing a third vapor stream, heating and at least partially vaporizing a third liquid stream to produce a first tower feed stream, heating and at least partially vaporizing a tower vapor stream, and combinations thereof;

a first separator for separating the feed gas stream into the first vapor stream and the first liquid stream;

a second heat exchanger for performing heat exchange tasks selected from the group consisting of cooling and at least partially condensing the first vapor stream, heating and at least partially vaporizing the third vapor stream, heating and at least partially vaporizing the first liquid stream, heating and at least partially vaporizing the second liquid stream, heating and at least partially vaporizing the third liquid stream, and combinations thereof;

a second separator for separating the cooled stream into the second vapor stream and the second liquid stream;

an expander for expanding and thereby decreasing a pressure of the second vapor stream to produce an expanded stream;

a third separator for separating the expanded stream into the third vapor stream and the third liquid stream;

a first compressor for compressing the third vapor stream to produce a hydrogen product stream that can be sent for further processing;

a reboiled absorber for receiving and separating the first tower feed stream fed at a first stage of the reboiled absorber, a second tower feed stream, and a third tower feed stream to produce a tower bottoms stream and a tower overhead stream;

a first cooler for cooling the tower bottoms stream thereby producing an LPG product stream that contains substantially at least 70% of propane (C3) and heavier compounds;

a second compressor for compressing and a second cooler for cooling the tower vapor stream that contains a fuel gas stream substantially free of hydrogen, which is sent for further processing.

24. The apparatus according to claim 23, wherein the first heat exchanger and the second heat exchanger comprise a separate heat exchanger for performing each of the heat exchange tasks.

25. An apparatus for recovering hydrogen and liquefied petroleum gases (LPG) from a fuel gas stream by means of a cryogenic process comprising the steps of:

a first heat exchanger for performing heat exchange tasks selected from the group consisting of cooling and at least partially condensing a feed gas stream, heating and at least partially vaporizing a first liquid stream to produce a third tower feed stream, heating and at least partially vaporizing a second liquid stream to produce a second tower feed stream, heating and at least partially vaporizing a third vapor stream, heating and at least partially vaporizing a third liquid stream to produce a first tower feed stream, heating and at least partially vaporizing a tower vapor stream, and combinations thereof;

a first separator for separating the feed gas stream into a first vapor stream and a first liquid stream;

a second heat exchanger for performing heat exchange tasks selected from the group consisting of cooling and at least partially condensing the first vapor stream, heating and at least partially vaporizing the third vapor stream, heating and at least partially vaporizing the first liquid stream, heating and at least partially vaporizing the second liquid stream, heating and at least partially vaporizing the third liquid stream, and combinations thereof;

a second separator for separating the cooled stream into a second vapor stream and a second liquid stream;

an expander for expanding and thereby decreasing a pressure of the second vapor stream to produce an expanded stream;

a third separator for separating the expanded stream into a third vapor stream and a third liquid stream;

a first compressor for compressing the warmed vapor stream to produce a hydrogen product stream that can be sent for further processing;

a fractionation tower for receiving and separating the first feed stream, the second feed stream, and the third feed stream to produce a fractionation tower bottoms stream and a fractionation tower overhead stream;

a first cooler for cooling the fractionation tower bottoms stream thereby producing an LPG product stream that contains substantially at least 90% of propane (C3) and heavier compounds;

a second cooler for cooling and at least partially condensing the fractionation tower overhead stream thereby producing a partially condensed fractionation tower stream;

a fourth separator for separating the condensed fractionation tower stream into a fractionation tower reflux stream that is sent back to the fractionation tower and a fractionation tower vapor stream; and

a second compressor for compressing the fractionation tower vapor stream that contains a fuel gas stream substantially free of hydrogen, which is sent for further processing.

26. The apparatus according to claim 25, wherein the first heat exchanger and the second heat exchanger comprise a separate heat exchanger for performing each of the heat exchange tasks.