Methods of producing hydrogen and solid carbon
A method for producing hydrogen, includes heating a process feed gas stream, flowing the process feed gas stream into a first reaction zone, flowing the intermediate gas stream into a second reaction zone, removing the solid carbon product from the second reaction zone, removing the tail gas stream from the second reaction zone, and removing hydrogen from the tail gas stream. The process gas stream includes methane and steam. The first reaction zone contains a first catalyst, and at least a portion of the process feed gas stream is converted into an intermediate gas stream in the first reaction zone. The second reaction zone contains a second catalyst, and at least a portion of the intermediate gas stream is converted into a tail gas stream and a solid carbon product in the second reaction zone.
1. A method for producing hydrogen, the method comprising:
heating a feed gas comprising methane and steam;
flowing the feed gas into a first reaction zone containing a first catalyst, wherein at least a portion of the feed gas is converted into hydrogen, wherein the hydrogen forms a part of a first intermediate gas;
separating a portion of the hydrogen from the first intermediate gas to form a second intermediate gas;
flowing the second intermediate gas into a second reaction zone containing a second catalyst, wherein at least a portion of the second intermediate gas is converted into solid carbon and water;
removing the solid carbon from the second reaction zone;
removing a tail gas from the second reaction zone, the tail gas comprising hydrogen; and
removing hydrogen from the tail gas to form a hydrogen gas stream and a hydrogen-depleted tail gas stream.
2. The method according to claim 1 , wherein the second intermediate gas comprises carbon oxides and hydrogen.
3. The method according to claim 1 , further comprising recycling the hydrogen-depleted tail gas to the first reaction zone.
4. The method according to claim 1 , wherein heating the feed gas comprises counter flowing through at least one heat exchanger at least one of at least a portion of the feed gas with at least one of at least a portion of the tail gas and at least a portion of the hydrogen-depleted tail gas for heat recovery.
5. The method according to claim 1 , wherein heating the feed gas comprises combustion of a portion of the methane in the feed gas.
6. The method according to claim 5 , wherein combustion of a portion of the methane in the feed gas comprises adding oxygen to the feed gas under conditions in which only a portion of the methane will combust with the oxygen.
7. The method according to claim 1 , wherein at least a portion of the steam in the feed gas is formed by combustion of at least a portion of the methane in the feed gas.
8. The method according to claim 1 , further comprising:
forming a first feed gas comprising methane;
forming a second feed gas comprising steam; and,
combining the first feed gas and the second feed gas to form a feed gas comprising methane and steam.
9. The method according to claim 1 , further comprising:
forming a first feed gas comprising methane;
forming a second feed gas comprising steam;
recycling at least a portion of the tail gas; and
combining the first feed gas, the second feed gas, and the portion of the tail gas to form a feed gas comprising methane and steam.
10. The method according to claim 1 , wherein at least one of the first catalyst and the second catalyst comprises steel.
11. The method according to claim 1 , further comprising maintaining at least one of the first reaction zone and the second reaction zone at a pressure between about 0 MPa and about 30 MPa.
12. The method according to claim 1 , further comprising maintaining the temperature of at least one of the first reaction zone and the second reaction zone at a temperature between approximately 500° C. and approximately 1500° C.
13. The method according to claim 1 , wherein:
at least a portion of the methane and at least a portion of the water react in the first reaction zone to produce carbon monoxide, carbon dioxide, and hydrogen in the presence of the first catalyst;
flowing the second intermediate gas into a second reaction zone comprises flowing at least a portion of the carbon monoxide, at least a portion of the carbon dioxide, and at least a portion of the hydrogen produced in the first reaction zone to the second reaction zone; and
at least a portion of the carbon monoxide, carbon dioxide, and hydrogen in the second reaction zone react to form solid carbon and water in the presence of the second catalyst.
14. The method according to claim 1 , further comprising removing at least a portion of the water from at least one of the tail gas and the hydrogen-depleted tail gas.
15. The method according to claim 14 , further comprising recycling at least a portion of the water to constitute at least a portion of the steam in the feed gas.
16. The method according to claim 1 , further comprising injecting water or steam into the first reaction zone to supplement at least a portion of the steam in the feed gas.
17. The method according to claim 1 , further comprising:
heating the feed gas to a temperature above the boiling point of water at the pressure of the feed gas; and
injecting steam or water into the feed gas to form at least a portion of the steam in the feed gas.
18. The method according to claim 1 , further comprising:
condensing water vapor from the second intermediate gas before flowing the second intermediate gas into the second reaction zone; and
removing water from the second intermediate gas.
19. The method according to claim 1 , wherein at least one of the first catalyst and the second catalyst comprises an unsupported iron-based catalyst comprising iron not in the alpha phase.