Method and system for treating Fishcher-Tropsch reactor tail gas

• US 8,419,829 B2
• Filed: 10/27/2010
• Issued: 04/16/2013
• Est. Priority Date: 10/27/2010
• Status: Active Grant

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: General Electric Company
• Inventors: Wallace, Paul Steven
• Primary Examiner(s): Greene, Jason M
• Application Number:
  US12/913,000
• Publication Number:
  US 20120103190A1
• Time in Patent Office: 902 Days
• Field of Search: 95/45, 95/55, 95/56, 951/39, 951/43, 951/48, 951/87, 952/36, 952/37, 96/4, 96/9, 961/08, 961/34, 962/43, 423/418.2, 423/648.1, 423/655, 423/437.1, 422/187
• US Class Current: 95/55
• CPC Class Codes: B01D 2252/20 Organic absorbents
• CPC Class Codes: B01D 2256/16 Hydrogen
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/308 Carbonoxysulfide COS
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2257/80 Water
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: B01D 53/1487 Removing organic compounds
• CPC Class Codes: B01D 53/229 Integrated processes (Diffusion and at least one other process, e.g. adsorption, absorption)
• CPC Class Codes: B01D 53/75 Multi-step processes
• CPC Class Codes: C01B 2203/0283 containing a CO-shift step, i.e. a water gas shift step
• CPC Class Codes: C01B 2203/0405 Purification by membrane separation
• CPC Class Codes: C01B 2203/0415 Purification by absorption in liquids
• CPC Class Codes: C01B 2203/043 Regenerative adsorption process in two or more beds, one for adsorption, the other for regeneration
• CPC Class Codes: C01B 2203/0465 Composition of the impurity
• CPC Class Codes: C01B 2203/0475 the impurity being carbon dioxide
• CPC Class Codes: C01B 2203/048 the impurity being an organic compound
• CPC Class Codes: C01B 2203/0485 the impurity being a sulfur compound
• CPC Class Codes: C01B 2203/062 Hydrocarbon production, e.g. Fischer-Tropsch process
• CPC Class Codes: C01B 3/12 : by reaction of water vapour with carbon monoxide
• CPC Class Codes: C01B 3/501 : by diffusion
• CPC Class Codes: C01B 3/52 : by contacting with liquids; Regeneration of used liquids C01B3/508 takes precedence
• CPC Class Codes: C10G 2/32 : with the use of catalysts
• CPC Class Codes: C10G 2300/1022 : Fischer-Tropsch products
• CPC Class Codes: C10J 2300/093 : Coal
• CPC Class Codes: C10J 2300/1659 : to liquid hydrocarbons Fischer-Tropsch process C10G2/00
• CPC Class Codes: C10J 2300/1815 : for carbon dioxide
• CPC Class Codes: C10J 2300/1846 : Partial oxidation, i.e. injection of air or oxygen only
• CPC Class Codes: C10J 3/00 : Production of combustible gases containing carbon monoxide from solid carbonaceous fuels destructive distillation processes C10B
• CPC Class Codes: C10K 1/005 : Carbon dioxide
• CPC Class Codes: C10K 1/024 : by filtration
• CPC Class Codes: C10K 1/08 : by washing with liquids; Reviving the used wash liquors gas washers B01D
• CPC Class Codes: C10K 3/04 : reducing the carbon monoxide content , e.g. water-gas shift [WGS]
• CPC Class Codes: Y02E 20/16 : Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
• CPC Class Codes: Y02E 20/18 : Integrated gasification combined cycle [IGCC], e.g. combined with carbon capture and storage [CCS]
• CPC Class Codes: Y02E 60/32 : Hydrogen storage
• CPC Class Codes: Y02P 20/129 : Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• CPC Class Codes: Y02P 20/151 : Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

A method and system for coal-to-liquids (CTL) conversion is provided. The system includes a coal gasifier configured to partially oxidize a coal fuel stream to generate a flow of synthesis gas (syngas), a Fischer-Tropsch (FT) reactor configured to receive the flow of syngas and to generate a stream of tail gas, and an absorber coupled in flow communication downstream of the FT reactor and configured to receive the stream of tail gas. The absorber is further configured to generate a first flow including carbon dioxide, C2 hydrocarbons, and higher boiling gas components (C3+) and a second flow including C1, carbon monoxide, hydrogen, and nitrogen. The system also includes a first membrane separator including a selective membrane configured to separate the second flow from the absorber generating a permeate flow of hydrogen and a non-permeate flow of combustion turbine fuel gas including methane and hydrogen.

Claims

1. A coal-to-liquids (CTL) conversion system comprising:

a coal gasifier configured to partially oxidize a coal fuel stream to generate a flow of synthesis gas (syngas);

a Fischer-Tropsch (FT) reactor configured to receive the flow of syngas and to generate a stream of tail gas;

an FT product refining subsystem coupled to said FT reactor and configured to discharge a flow of off-gas and a flow of hydrogen;

an absorber coupled in flow communication downstream of said FT reactor and configured to receive the stream of tail gas, said absorber further configured to generate a first flow comprising carbon dioxide, C2 hydrocarbons, and higher boiling gas components (C3+) and a second flow comprising C1, carbon monoxide, hydrogen, and nitrogen, said absorber coupled to said FT product refining subsystem to receive said discharged off-gas flow; and

a first membrane separator comprising a selective membrane configured to separate the second flow from the absorber generating a permeate flow of hydrogen and a non-permeate flow of combustion turbine fuel gas including methane and hydrogen, said first membrane separator coupled to said FT product refining subsystem to receive hydrogen flow discharged from said FT product refining subsystem.

2. A conversion system in accordance with claim 1, further comprising a gas purge of the second flow, said gas purge configured to generate a flow of purge gas including methane and hydrogen and a flow of remainder gases.

3. A conversion system in accordance with claim 1, further comprising a second membrane separator coupled in flow communication with said first membrane separator, said second membrane separator configured to generate a flow of substantially contaminant free hydrogen and a flow of remainder gases.

4. A method of treating tail gas of a Fischer-Tropsch (FT) reactor, said method comprising:

generating a flow of tail gas using an FT reactor;

absorbing carbon dioxide, C2 hydrocarbons, and C3-C7 hydrocarbons from the flow of tail gas generating a flow of lean tail gas including at least C1 hydrocarbons, carbon monoxide, hydrogen, and nitrogen and a flow of absorbent;

discharging a flow of off-gas and a flow of hydrogen from an FT product refining subsystem;

channeling the flow of off-gas to an absorber;

channeling the flow of hydrogen to a membrane separator;

purging the lean tail gas to generate a flow of purge gas including methane, nitrogen, and hydrogen and a flow of remainder gases;

separating the flow of purge gas generating a permeate flow of hydrogen and a non-permeate flow of combustion turbine fuel gas including methane, hydrogen and nitrogen; and

channeling the non-permeate flow to a power generation system configured to generate a flow of electricity using the non-permeate flow.

5. A method in accordance with claim 4 further comprising drying the flow of tail gas in a glycol dryer to remove water.

6. A method in accordance with claim 4 wherein absorbing carbon dioxide, C2 hydrocarbons, and C3-C7 hydrocarbons from the flow of tail gas comprises absorbing carbon dioxide, C2 hydrocarbons, and C3-C7 hydrocarbons from the flow of tail gas using an absorbent including refrigerated liquefied petroleum gas (LPG) and naphtha.

7. A method in accordance with claim 4 wherein purging the lean tail gas comprises channeling the flow of remainder gases to the FT reactor.

8. A method in accordance with claim 4 further comprising recycling a first portion of the separated flow of purge gas to the FT reactor.

9. A method in accordance with claim 8 wherein recycling a first portion of the separated flow of purge gas to the FT reactor comprises recycling a first portion comprising substantially nitrogen-free hydrogen to the FT reactor.

10. A method in accordance with claim 4 further comprising channeling a second portion of the separated flow of purge gas to a pressure swing adsorption (PSA) unit generating a flow of substantially pure hydrogen and a flow of PSA tail gas.

11. A method in accordance with claim 10 further comprising channeling the flow of substantially pure hydrogen to a Fischer-Tropsch (FT) upgrading unit.

12. A method in accordance with claim 10 further comprising channeling the flow of PSA tail gas to a heat recovery steam generator (HRSG) for supplemental firing.

13. A method in accordance with claim 4 further comprising maintaining residual concentrations of hydrogen and carbon dioxide in the non-permeate flow of combustion turbine fuel gas to maintain a substantially constant Wobbe index of the non-permeate flow of combustion turbine fuel gas.

14. A method in accordance with claim 4 further comprising stripping carbon dioxide and C2 hydrocarbons from the absorbent.

15. A method in accordance with claim 14 further comprising channeling the stripped carbon dioxide and C2 hydrocarbons to a gasifier recycle carbon dioxide stream.

16. A method in accordance with claim 4 further comprising blending the stripped carbon dioxide and C2 hydrocarbons with the non-permeate flow of combustion turbine fuel gas to facilitate maintaining a substantially constant Wobbe index.

17. A Fischer-Tropsch tail gas treatment system comprising:

a Fischer-Tropsch (FT) reactor configured to generate a flow of tail gas;

an FT product refining subsystem coupled to said FT reactor and configured to discharge a flow of off-gas and a flow of hydrogen;

an absorber coupled in flow communication with said FT reactor and configured to receive the flow of tail gas, said absorber further configured to separate the tail gas into a flow of lean tail gas comprising at least C1 hydrocarbons, carbon monoxide, hydrogen, and nitrogen and a flow of absorbent comprising carbon dioxide, C2 hydrocarbons, and C3-C7 hydrocarbons, said absorber coupled to said FT product refining subsystem to receive said discharged off-gas flow;

a lean tail gas purge configured to generate a flow of purge gas including methane and hydrogen and a flow of remainder gases; and

a membrane separator comprising a selective membrane configured to separate the flow of purge gas generating a permeate flow of hydrogen and a non-permeate flow of combustion turbine fuel gas including methane and hydrogen, said membrane separator coupled to said FT product refining subsystem to receive hydrogen flow discharged from said FT product refining subsystem.

18. A system in accordance with claim 17 further comprising a pressure swing adsorber (PSA) unit coupled in flow communication with the generated permeate flow and configured to generate a flow of substantially contaminate free hydrogen.

19. A system in accordance with claim 17 further comprising a coal gasifier configured to partially oxidize a coal fuel stream to generate a flow of synthesis gas (syngas), said FT reactor is configured to receive the flow of syngas from a coal gasifier.

20. A system in accordance with claim 17 comprising a CO2 stripper in flow communication between said absorber and a coal gasifier, said stripper configured to generate a flow of CO2 and C2 for recycle to an inlet of the coal gasifier and to generate a flow of liquid petroleum gas (LPG).