Processes for Gasification of a Carbonaceous Feedstock

• US 20100179232A1
• Filed: 10/23/2009
• Published: 07/15/2010
• Est. Priority Date: 10/23/2008
• Status: Active Grant

• Current Assignee: Sure Champion Investments Limited
• Original Assignee: GreatPoint Energy, Inc.
• Inventors: Raman, Pattabhi K., Robinson, Earl T., Gal, Eli, Reiling, Vincent G.
• Granted Patent: US 8,202,913 B2
• Time in Patent Office: Days
• US Class Current: 518/703
• CPC Class Codes: C01B 2203/0415 Purification by absorption in liquids
• CPC Class Codes: C01B 2203/0445 Selective methanation
• 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 3/12 by reaction of water vapour with carbon monoxide
• CPC Class Codes: C01B 3/52 by contacting with liquids; Regeneration of used liquids C01B3/508 takes precedence
• CPC Class Codes: C01B 3/586 the reaction being a methanation reaction
• CPC Class Codes: C10J 2300/093 Coal
• CPC Class Codes: C10J 2300/0959 Oxygen
• 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 2300/1884 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 3/721 Multistage gasification, e.g. plural parallel or serial gasification stages
• 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 3/102 : of acid contaminants

Abstract

The present invention relates to processes and continuous processes for preparing gaseous products, and in particular, methane via the catalytic gasification of carbonaceous feedstocks in the presence of steam. In one aspect of the invention, the processes comprise at least partially combusting a first carbonaceous feedstock with an oxygen-rich gas stream, a recycle steam stream, and an aqueous make-up stream in an oxygen-blown gasifier, under suitable temperature and pressure, to generate a first gas stream comprising hydrogen, carbon monoxide and superheated steam; and reacting a second carbonaceous feedstock and the first gas stream in a catalytic gasifier in the presence of a gasification catalyst under suitable temperature and pressure to form a second gas stream comprising a plurality of gaseous products comprising methane, carbon dioxide, hydrogen, carbon monoxide and hydrogen sulfide. The processes can comprise using at least one catalytic methanator to convert carbon monoxide and hydrogen in the gaseous products to methane and in certain embodiments do not recycle carbon monoxide or hydrogen to the gasifier. Heat energy recovered from the catalytic gasification can be used to generate the recycle steam stream.

Claims

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

(a) supplying to an oxygen-blown gasifier a first carbonaceous feedstock, an oxygen-rich gas stream and at least a portion of a recycle steam stream;

(b) optionally supplying to the oxygen-blown gasifier a first aqueous make-up stream comprising one or both of water and makeup steam;

(c) at least partially combusting the first carbonaceous feedstock with the oxygen-rich gas stream in the oxygen-blown gasifier, at a first temperature and a first pressure suitable to generate a first gas stream comprising hydrogen, carbon monoxide and superheated steam at a second temperature and a second pressure;

(d) optionally combining the first gas stream with (d1) a second aqueous make-up stream comprising one or both of water and makeup steam, or (d2) a remaining portion of a recycle steam stream, or (d3) both (d1) and (d2), to generate a combined first gas stream comprising hydrogen, carbon monoxide and superheated steam at a third temperature and a third pressure;

(e) introducing a second carbonaceous feedstock, a gasification catalyst and at least a portion of the first gas stream (or at least a portion of the combined first gas stream if present) to a catalytic gasifier;

(f) reacting the second carbonaceous feedstock and the first gas stream (or the combined first gas stream if present) in the catalytic gasifier in the presence of the gasification catalyst, at a fourth temperature and a fourth pressure, suitable to produce a second gas stream comprising a plurality of gaseous products comprising methane, carbon dioxide, hydrogen, carbon monoxide and hydrogen sulfide, the second gas steam containing heat energy available for recovery;

(g) recovering a portion of the heat energy from the second gas stream, wherein at least a portion of the recovered heat energy is utilized to generate a first steam recycle stream;

(h) in the event that the molar ratio of hydrogen to carbon monoxide in the second gas stream is less than about 3;

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

1;

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

(j) removing a substantial portion of the carbon dioxide and a substantial portion of the hydrogen sulfide from the second gas stream (or the hydrogen-enriched second gas stream if present) to produce an acid gas-depleted third gas stream comprising a substantial portion of the methane from the second gas stream (or the hydrogen-enriched second gas stream if present);

(k) reacting carbon monoxide and hydrogen present in the acid gas-depleted third gas stream in a catalytic methanator in the presence of a methanation catalyst to produce heat energy and a methane-enriched third gas stream;

(l) optionally recovering a portion of the heat energy from step (k), wherein at least a portion of the recovered heat energy is utilized to generate a third steam recycle steam; and

(m) recovering the methane-enriched third gas stream,

wherein;

(1) at least one of the first and second aqueous makeup streams is present;

(2) step (f) has a total steam requirement made up from the recycle steam stream and, to the extent present, the first and second aqueous makeup streams;

(3) the first and second aqueous makeup streams supply about 15% or less of the total steam requirement for step (f);

(4) the recycle steam stream comprises the first steam recycle stream and, if present, one or both of the second and third steam recycle streams;

(5) the second temperature is higher than the fourth temperature;

(6) if the combined first gas stream is present, the third temperature is lower than the second temperature and higher than the fourth temperature; and

(7) the third gas stream (or the methane-enriched third gas stream if present) is the methane product stream, or the third gas stream (or the methane-enriched third gas stream if present) is purified to generate the methane product stream.

2. The process of claim 1, which is a continuous process in which steps (a), (c), (e), (f), (g), (j), (k) and (m) are performed in a continuous manner.

3. The process of claim 1, wherein the gasification catalyst comprises an alkali metal gasification catalyst.

4. The process of claim 1, wherein the first and second carbonaceous feedstock each independently comprise one or more of anthracite, bituminous coal, sub-bituminous coal, lignite, petroleum coke, asphaltenes, liquid petroleum residues or biomass.

5. The process of claim 1, wherein the second carbonaceous feedstock is loaded with a gasification catalyst prior to introduction into the catalytic gasifier.

6. The process of claim 5, wherein the second carbonaceous feedstock is loaded with an amount of an alkali metal gasification catalyst sufficient to provide a ratio of alkali metal atoms to carbon atoms ranging from about 0.01 to about 0.10.

7. The process of claim 1, wherein the second carbonaceous feedstock, gasification catalyst and first gas stream (or the combined first gas stream if present) are introduced into a plurality of catalytic gasifiers.

8. The process of claim 7, wherein a single oxygen-blown gasifier supplies the first gas stream to the plurality of catalytic gasifiers.

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

10. The process of claim 1, wherein step (i) or step (l) is present.

11. The process of claim 1, wherein both steps (i) and (l) are present.

12. The process of claim 1, which is a once-through process.

13. The process of claim 1, wherein no carbon fuel-fired superheater is present.

14. The process of claim 1, wherein the second gas stream comprises at least about 20 mol % methane based on the moles of methane, carbon dioxide, carbon monoxide and hydrogen in the second gas stream.

15. The process of claim 1, wherein the second gas stream comprises at least 50 mol % methane plus carbon dioxide based on the moles of methane, carbon dioxide, carbon monoxide and hydrogen in the second gas stream.

16. The process of claim 1, wherein the remaining portion of the first gas stream is utilized to generate power and the aqueous makeup stream.

17. The process of claim 1, wherein the first gas stream further comprises particulates and at least a portion of the particulates is removed from the first gas stream prior to introduction of the first gas stream (or combined first gas stream if present) into the catalytic gasifier.

18. The process of claim 1, wherein at least a portion of the methane product stream is utilized to generate power.

19. The process of claim 1, wherein a solid char product is generated in step (f), which is passed to a catalyst recovery unit.

20. A gasifier apparatus for producing a plurality of gases from a catalyzed carbonaceous feedstock, the gasifier apparatus comprising:

(a) an oxygen-blown gasifier configured (1) to operate at a first temperature and a first pressure;

(2) to receive a first carbonaceous feedstock, an oxygen-rich gas stream, a recycle steam stream and, optionally, a first aqueous makeup stream, wherein the recycle steam stream comprises a first steam recycle stream and, optionally, a second steam recycle stream and a third steam recycle stream, and wherein the first aqueous make-up stream comprises one or both of water and make-up steam; and

(3) to generate a first gas stream comprising hydrogen, carbon monoxide and superheated team at a second temperature and a second pressure;

(b) optionally, an aqueous make-up stream feed configured (1) to provide a second aqueous makeup stream, and (2) to combine the second aqueous makeup stream with the first gas stream to generate a combined first gas stream at a third temperature and a third pressure, wherein the second aqueous makeup stream comprises one or both of water and makeup steam,

(c) a fluidized bed gasifier in communication with the oxygen-blown gasifier and, if present, the aqueous make-up stream line, the fluidized bed gasifier configured (1) to operate at a fourth temperature and a fourth pressure;

(2) to receive a catalyzed carbonaceous feedstock and the first gas stream (or combined first gas stream if present); and

(3) to exhaust a second gas stream comprising methane, carbon dioxide, hydrogen, carbon monoxide and hydrogen sulfide;

(d) a first heat recovery unit in communication with the fluidized bed gasifier to recover heat energy from the second gas stream and generate the first steam recycle stream;

(e) a sour shift reactor in communication with the first heat recovery unit to sour shift a portion of carbon monoxide in the second gas stream to generate a hydrogen-enriched second gas stream;

(f) a second heat recovery unit in communication with the sour shift reactor to recover heat energy from the sour shift reactor, the hydrogen-enriched second gas stream or both, and generate the second steam recycle stream;

(g) a gas bypass loop in communication with the first heat recovery unit to bypass the sour shift reactor;

(h) an acid gas remover unit in communication with the sour shift reactor and the gas bypass loop to remove at least a substantial portion carbon dioxide and at least a substantial portion of the hydrogen sulfide from the second gas stream and generate an acid gas-depleted third gas stream;

(i) a catalytic methanator in communication with the acid gas remover unit to react carbon monoxide and hydrogen from the acid gas-depleted third gas stream and generate a methane-enriched third gas stream;

(j) a third heat recovery unit in communication with the catalytic methanator to recover heat energy from the catalytic methanator, the methane-enriched gas stream or both, and generate the third steam recycle stream; and

(k) a recycle loop for recycling the first, second and third recycle steam streams to the oxygen-blown gasifier.