Processes for the Separation of Methane from a Gas Stream

• US 20090259080A1
• Filed: 03/31/2009
• Published: 10/15/2009
• Est. Priority Date: 04/01/2008
• Status: Active Grant

• Current Assignee: Sure Champion Investments Limited
• Original Assignee: GreatPoint Energy, Inc.
• Inventors: Robinson, Earl T., Raman, Pattabhi K., Lau, Francis S.
• Granted Patent: US 8,999,020 B2
• Time in Patent Office: Days
• US Class Current: 585/3
• CPC Class Codes: C01B 2203/0205 containing a reforming step
• 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 2203/0435 Catalytic purification
• CPC Class Codes: C01B 2203/0465 Composition of the impurity
• CPC Class Codes: C01B 2203/047 the impurity being carbon monoxide
• 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 2203/06 Integration with other chemical processes
• CPC Class Codes: C01B 2203/1241 Natural gas or methane
• CPC Class Codes: C01B 2203/84 Energy production
• CPC Class Codes: C01B 3/34 by reaction of hydrocarbons with gasifying agents
• CPC Class Codes: C01B 3/52 by contacting with liquids; Regeneration of used liquids C01B3/508 takes precedence
• CPC Class Codes: C01B 3/58 including a catalytic reaction
• CPC Class Codes: C10J 2300/0903 Feed preparation
• CPC Class Codes: C10J 2300/0973 Water
• CPC Class Codes: C10J 2300/0986 Catalysts
• CPC Class Codes: C10J 2300/1662 to methane (SNG) production of synthetic natural gas C10L3/08
• CPC Class Codes: C10J 2300/1807 : Recycle loops, e.g. gas, solids, heating medium, water
• CPC Class Codes: C10J 2300/1823 : for synthesis gas
• CPC Class Codes: C10J 2300/1853 : Steam reforming, i.e. injection of steam 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: C10J 3/482 : Gasifiers with stationary fluidised bed
• CPC Class Codes: C10J 3/72 : Other features
• CPC Class Codes: C10J 3/82 : Gas withdrawal means
• CPC Class Codes: C10K 3/04 : reducing the carbon monoxide content , e.g. water-gas shift [WGS]
• CPC Class Codes: C10L 3/08 : Production of synthetic natural gas
• CPC Class Codes: C10L 3/10 : Working-up natural gas or synthetic natural gas
• CPC Class Codes: F25J 2205/40 : using hybrid system, i.e. combining cryogenic and non-cryogenic separation techniques
• CPC Class Codes: F25J 2205/80 : using membrane, i.e. including a permeation step
• CPC Class Codes: F25J 2215/02 : Mixing or blending of fluids to yield a certain product
• CPC Class Codes: F25J 2245/02 : Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 3/0223 : H2/CO mixtures, i.e. synthesis gas; Water gas or shifted synthesis gas production of carbon monoxide containing gas in general C01B32/40, C10J, C10K; production of hydrogen containing gas C01B3/00
• CPC Class Codes: F25J 3/0233 : separation of CnHm with 1 carbon atom 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 3/0261 : separation of carbon monoxide production of carbon monoxide containing gas in general C01B32/40, C10J, C10K
• CPC Class Codes: F25J 3/0271 : separation of H2/CO mixtures, i.e. of synthesis gas production of carbon monoxide containing gas in general C01B32/40, C10J, C10K, production of hydrogen containing gas C01B3/00

Abstract

Processes for the catalytic conversion of a carbonaceous composition into a gas stream comprising methane are provided. In addition, the processes provide for the generation of a hydrogen-enriched gas stream and, optionally, a carbon monoxide-enriched gas stream, which can be mixed or used separately as an energy source for subsequent catalytic gasification processes.

Claims

1. A process for converting a carbonaceous feedstock into a plurality of gaseous products contained in a gas stream, and for separating hydrogen and methane from the gas stream, the process comprising the steps of:

(a) supplying a carbonaceous feedstock to a gasification reactor;

(b) reacting the carbonaceous feedstock in the gasification reactor in the presence of steam and a gasification catalyst and under suitable temperature and pressure to form a first gas stream comprising methane, hydrogen, carbon monoxide, carbon dioxide, and one or more additional gaseous by-products;

(c) removing a substantial portion of the carbon dioxide and a substantial portion of the one or more additional gaseous by-products from the first gas stream to produce a second gas stream comprising methane, hydrogen, and optionally carbon monoxide;

(d) at least partially separating hydrogen from the second gas stream to form a hydrogen-enriched gas stream and a hydrogen-depleted gas stream, wherein the hydrogen-depleted gas stream comprises methane, optionally carbon monoxide and up to about 4 mol % hydrogen;

wherein, if the heating value of the hydrogen-depleted gas stream is less than 950 btu/scf (dry basis), and if the hydrogen-depleted gas stream comprises 1000 ppm or more of carbon monoxide;

(1) at least partially separating carbon monoxide from the hydrogen-depleted gas stream to form (i) a carbon monoxide-enriched gas stream and (ii) a methane-enriched gas stream having a heating value of at least 950 btu/scf (dry basis);

or (2) at least partially methanating the carbon monoxide in the hydrogen-depleted gas stream to form a methane-enriched gas stream.

2. The process of claim 1, wherein the second gas stream comprises carbon monoxide, and the hydrogen-depleted gas stream comprises at least about 1000 ppm carbon monoxide.

3. The process of claim 2, wherein the carbon monoxide in the hydrogen-depleted gas stream is at least partially methanated to form a methane-enriched gas stream.

4. The process of claim 1, wherein the gasification catalyst is an alkali metal gasification catalyst.

5. The process of claim 4, wherein the alkali metal is potassium.

6. The process of claim 1, wherein the hydrogen is separated by passing the second gas stream through a hydrogen membrane separator.

7. A process for converting a carbonaceous feedstock into a plurality of gaseous products contained in a gas stream, and for separating hydrogen and methane from the gas stream, the process comprising the steps of:

(a) supplying a first carbonaceous feedstock to a reactor;

(b) at least partially combusting the first carbonaceous feedstock in the reactor in the presence of oxygen and under suitable temperature and pressure so as to generate (i) heat energy and (ii) a combustion gas stream comprising hydrogen, carbon monoxide, and carbon dioxide;

(c) using the heat energy from the combustion of the first carbonaceous feedstock to generate steam;

(d) introducing at least a portion of the steam, at least a portion of the combustion gas stream, a second carbonaceous feedstock and a gasification catalyst to a gasification reactor;

(e) reacting the second carbonaceous feedstock in the gasification reactor in the presence of steam and the gasification catalyst under suitable temperature and pressure to form a first gas stream comprising methane, hydrogen, carbon monoxide, carbon dioxide and one or more additional gaseous by-products;

(f) removing a substantial portion of the carbon dioxide and a substantial portion of the one or more gaseous by-products from the first gas stream to produce a second gas stream comprising methane, hydrogen and optionally carbon monoxide;

(g) at least partially separating hydrogen from the second gas stream to form a hydrogen-enriched gas stream and a hydrogen-depleted gas stream, wherein the hydrogen-depleted gas stream comprises methane, optionally carbon monoxide and up to about 4 mol % hydrogen;

wherein, if the heating value of the hydrogen-depleted gas stream is less than 950 btu/scf (dry basis), and if the hydrogen-depleted gas stream comprises 1000 ppm or more of carbon monoxide;

(1) at least partially separating carbon monoxide from the hydrogen-depleted gas stream to form (i) a carbon monoxide-enriched gas stream and (ii) a methane enriched gas stream having a heating value of at least 950 btu/scf (dry basis);

or (2) at least partially methanating the carbon monoxide in the hydrogen-depleted gas stream to form a methane-enriched gas stream.

8. The process of claim 7, wherein the first carbonaceous feedstock and the second carbonaceous feedstock have substantially the same composition.

9. The process of claim 7, wherein the first carbonaceous feedstock and the second carbonaceous feedstock have different compositions.

10. The process of claim 7, wherein the first carbonaceous feedstock, the second carbonaceous feedstock, or both the first carbonaceous feedstock and the second carbonaceous feedstock are in a particulate form.

11. The process of claim 7, wherein the first carbonaceous feedstock is in the form of an aqueous slurry.

12. The process of claim 7, wherein the reactor is either a gasification reactor or an oxygen combustor.

13. The process of claim 7, wherein, in step (c), the steam is generated within the reactor.

15. The process of claim 7, wherein substantially all of the steam generated in step (c) is introduced into the gasification reactor.

16. The process of claim 7, wherein the second gas stream comprises carbon monoxide, and the hydrogen-depleted gas stream comprises at least about 1000 ppm carbon monoxide.

17. The process of claim 16, wherein the carbon monoxide in the hydrogen-depleted gas stream is at least partially methanated to form a methane-enriched gas stream.

18. The process of claim 7, wherein the gasification catalyst is an alkali metal gasification catalyst.

19. The process of claim 18, wherein the alkali metal is potassium.

20. The process of claim 7, wherein the hydrogen is separated by passing the second gas stream through a hydrogen membrane separator.

14. The process of claim 14, wherein, in step (c), the heat energy is transferred to a heat exchanger which generates steam upon contact with water.