Processes for Hydromethanation of a Carbonaceous Feedstock

• US 20100287836A1
• Filed: 05/12/2010
• Published: 11/18/2010
• Est. Priority Date: 05/13/2009
• Status: Active Grant

• Current Assignee: Sure Champion Investments Limited
• Original Assignee: GreatPoint Energy, Inc.
• Inventors: Robinson, Earl T., Sirdeshpande, Avinash
• Granted Patent: US 8,728,182 B2
• Time in Patent Office: Days
• US Class Current: 48/127.7
• CPC Class Codes: C01B 2203/0415 Purification by absorption in liquids
• CPC Class Codes: C01B 2203/0445 Selective methanation
• 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 2203/0485 the impurity being a sulfur compound
• CPC Class Codes: C01B 2203/86 Carbon dioxide sequestration
• CPC Class Codes: C01B 3/16 using catalysts
• CPC Class Codes: C01B 3/501 by diffusion
• CPC Class Codes: C01B 3/506 at low temperatures
• CPC Class Codes: C01B 3/52 by contacting with liquids; Regeneration of used liquids C01B3/508 takes precedence
• CPC Class Codes: C01B 3/56 by contacting with solids; Regeneration of used solids C01B3/508 takes precedence
• CPC Class Codes: C01B 3/586 the reaction being a methanation reaction
• CPC Class Codes: C01B 32/50 Carbon dioxide
• CPC Class Codes: C10J 2300/093 Coal
• CPC Class Codes: C10J 2300/0973 Water
• CPC Class Codes: C10J 2300/0986 Catalysts
• CPC Class Codes: C10J 2300/1618 Modification of synthesis gas composition, e.g. to meet some criteria
• CPC Class Codes: C10J 2300/1662 to methane (SNG) production of synthetic natural gas C10L3/08
• CPC Class Codes: C10J 2300/1687 with steam generation
• CPC Class Codes: C10J 2300/1838 : Autothermal gasification by injection of oxygen or steam
• CPC Class Codes: C10J 2300/1884 : with one stream being synthesis gas
• CPC Class Codes: C10J 2300/1892 : with one stream being water/steam
• 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 3/86 : combined with waste-heat boilers
• CPC Class Codes: C10L 3/08 : Production of synthetic natural gas
• CPC Class Codes: Y02P 30/00 : Technologies relating to oil refining and petrochemical industry

Abstract

The present invention relates to processes for preparing gaseous products, and in particular methane, via the hydromethanation of carbonaceous feedstocks in the presence of steam, carbon monoxide, hydrogen and a hydromethanation catalyst.

Claims

1. A process for generating a plurality of gaseous products from a carbonaceous feedstock, and generating a methane product stream, the process comprising the steps of:

(a) supplying to a hydromethanation reactor a carbonaceous feedstock, a hydromethanation catalyst, a steam stream, a first gas feed stream and, optionally, a first oxygen-rich gas stream;

(b) reacting the carbonaceous feedstock in the hydromethanation reactor in the presence of carbon monoxide, hydrogen, steam and hydromethanation catalyst, to produce a methane-enriched raw product stream comprising methane, carbon monoxide, hydrogen, carbon dioxide and heat energy;

(c) withdrawing the methane-enriched product stream from the hydromethanation reactor;

(d) introducing the methane-enriched raw product stream into a heat exchanger to recover heat energy and generate a cooled methane-enriched raw product stream;

(e) using the heat energy recovered in step (d) to (1) superheat the steam stream prior to introduction into the hydromethanation reactor, and (2) generate a first process steam stream;

(f) in the event that the molar ratio of hydrogen to carbon monoxide in the cooled methane-enriched raw product stream is less than about 3;

1, optionally sour shifting a portion of the carbon monoxide in the cooled methane-enriched raw product stream to generate heat energy and a hydrogen-enriched treated product stream having a molar ratio of hydrogen to carbon monoxide of at least about 3;

1;

(g) optionally recovering heat energy from step (f), if present, wherein at least a portion of the recovered heat energy is utilized to generate a second process steam stream;

(h) optionally reacting a portion of the hydrogen and at least a portion of the carbon monoxide in the cooled methane-enriched raw product stream (or the hydrogen-enriched treated product stream if present) in a catalytic methanator in the presence of a sulfur-tolerant methanation catalyst to produce a methane-enriched treated product stream;

(i) optionally recovering heat energy from step (h), if present, wherein a least a portion of the recovered heat energy is utilized to generate a third process steam stream;

(j) removing a substantial portion of the carbon dioxide and a substantial portion of the hydrogen sulfide from the cooled methane-enriched raw product stream (or the hydrogen-enriched treated product stream, if present, or the methane-enriched treated product stream, if present) to produce a sweetened gas stream comprising a substantial portion of the hydrogen, carbon monoxide and methane from the cooled methane-enriched raw product stream (or the hydrogen-enriched treated product stream, if present, or the methane-enriched treated product stream, if present);

(k) splitting the sweetened gas stream into a recycle gas stream and a sweetened product gas stream;

(l) supplying the recycle gas stream and a second oxygen-rich gas stream to a partial oxidation reactor;

(m) reacting the recycle gas stream with oxygen in the partial oxidation reactor to generate heat energy and the first gas feed stream, wherein the first gas steam comprises carbon monoxide, hydrogen and steam;

(n) optionally separating a portion of the hydrogen from the sweetened product gas stream to produce a hydrogen-depleted sweetened product gas stream comprising methane, hydrogen and carbon monoxide;

(o) reacting carbon monoxide and hydrogen present in the sweetened product gas stream (or hydrogen-depleted sweetened product gas stream, if present) in a catalytic methanator in the presence of a methanation catalyst to produce heat energy and a methane-enriched sweetened product gas stream;

(p) recovering heat energy from step (o), wherein at least a portion of the recovered heat energy is utilized to generate a fourth process steam stream; and

(q) recovering at least a portion of the methane-enriched sweetened product gas stream as the methane product stream,

wherein;

the reaction in step (b) has a steam demand, a syngas demand and a heat demand,

the carbonaceous feedstock comprises a moisture content,

the first oxygen-rich gas stream, if present, optionally comprises steam,

the steam demand is substantially satisfied by the steam stream, steam contained in the feed gas stream, the moisture content of the carbonaceous feedstock and, if present, steam in the first oxygen-rich gas stream,

the steam stream is substantially made up from at least a portion of one or more of the first process steam stream, the fourth process steam stream, the second process steam stream (when present), and the third process steam stream (when present),

the amount of carbon monoxide and hydrogen in the first gas feed stream is sufficient to meet the syngas demand of the reaction in step (b), and

the steam stream and the feed gas stream comprise heat energy that, in combination, is sufficient to substantially meet the heat demand of the reaction in step (b).

2. The process of claim 1, wherein the steam demand is satisfied by the steam stream, steam contained in the feed gas stream, the moisture content of the carbonaceous feedstock and, if present, steam in the first oxygen-rich gas stream.

3. The process of claim 1, wherein the steam stream and the feed gas stream comprise heat energy that, in combination, is sufficient to meet the heat demand of the reaction in step (b).

4. The process of claim 1, wherein the methane-enriched raw product stream comprises at least about 20 mol % methane (based on the moles of methane, carbon dioxide, carbon monoxide and hydrogen in the methane-enriched raw product stream).

5. The process of claim 1, wherein the methane-enriched raw product stream comprises at least 50 mol % methane plus carbon dioxide (based on the moles of methane, carbon dioxide, carbon monoxide and hydrogen in the methane-enriched raw product stream).

6. The process of claim 1, wherein the carbonaceous feedstock is loaded with hydromethanation catalyst prior to being supplied to the hydromethanation reactor.

7. The process of claim 1, wherein the hydromethanation catalyst comprises an alkali metal.

8. The process of claim 1, wherein a char by-product is generated in step (b), which is continuously or periodically withdrawn from the hydromethanation reactor.

9. The process of claim 8, wherein the hydromethanation catalyst comprises an alkali metal, the char by-product comprises an alkali metal content from the hydromethanation catalyst, at least a portion of the char by-product is treated to recover at least a portion of the alkali metal content, and at least a portion of the recovered alkali metal content is recycled for use as hydromethanation catalyst.

10. The process of claim 9, wherein the carbonaceous feedstock is impregnated with hydromethanation catalyst prior to being supplied to the hydromethanation reactor, and the hydromethanation catalyst used to impregnate the second carbonaceous feedstock comprises recycled hydromethanation catalyst and a make-up hydromethanation catalyst.

11. The process of claim 1, which is a continuous process in which steps (a-e, j-m and o-q) are operated in a continuous manner.

12. The process of claim 1, wherein the steam stream and the first gas feed stream are combined prior to being supplied to the hydromethanation reactor.

13. The process of claim 1, wherein step (f) is present.

14. The process of claim 1, wherein step (h) is not present.

15. The process of claim 1, wherein step (n) is not present.

16. The process of claim 13, wherein step (n) is present.

17. The process of claim 1, wherein the hydromethanation reactor is operated at a temperature of at least about 700°

F. (about 371°

C.) to about 1500°

F. (about 816°

C.), and a pressure of about 250 psig (about 1825 kPa, absolute) to about 800 psig (about 5617 kPa).

18. The process of claim 1, wherein the sweetened product stream comprises at least about 40 wt % of the sweetened gas stream, and the recycle gas stream comprises from about 34 wt % up to about 60 wt % of the sweetened gas stream.

19. The process of claim 1, wherein the methane product stream is a pipeline-quality natural gas product.