Systems and Methods for Improving Ammonia Synthesis Efficiency

• US 20100132259A1
• Filed: 12/03/2008
• Published: 06/03/2010
• Est. Priority Date: 12/03/2008
• Status: Active Grant

• Current Assignee: Kellogg Brown & Root LLC (KBR Incorporated)
• Original Assignee: Kellogg Brown & Root LLC (KBR Incorporated)
• Inventors: Haque, Israr Ul
• Granted Patent: US 8,617,270 B2
• Time in Patent Office: Days
• US Class Current: 48/62.R
• CPC Class Codes: C01B 2203/0233 the reforming step being a steam reforming step
• CPC Class Codes: C01B 2203/0261 containing a catalytic partial oxidation step [CPO]
• CPC Class Codes: C01B 2203/0283 containing a CO-shift step, i.e. a water gas shift step
• CPC Class Codes: C01B 2203/044 Selective oxidation of carbon monoxide
• CPC Class Codes: C01B 2203/0445 Selective methanation
• CPC Class Codes: C01B 2203/0475 the impurity being carbon dioxide
• CPC Class Codes: C01B 2203/068 Ammonia synthesis
• CPC Class Codes: C01B 2203/1241 Natural gas or methane
• CPC Class Codes: C01B 2203/146 At least two purification steps in series
• CPC Class Codes: C01B 3/025 Preparation or purification of gas mixtures for ammonia synthesis
• CPC Class Codes: C01B 3/382 Multi-step processes
• CPC Class Codes: C01B 3/384 the catalyst being continuously externally heated
• CPC Class Codes: C01B 3/48 followed by reaction of water vapour with carbon monoxide
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

Systems and methods for producing syngas are provided. In at least one specific embodiment, a hydrocarbon can be reformed in the presence of steam and one or more first catalysts in a first reaction zone to provide an effluent containing a portion of the hydrocarbon, carbon monoxide, carbon dioxide, and hydrogen at a first temperature. The first reaction zone can include one or more catalyst-containing tubes. The effluent can be indirectly heated from the first temperature to a second temperature. The effluent at the second temperature can be reformed in the presence of one or more oxidants and one or more second catalysts at conditions sufficient to provide a syngas comprising hydrogen, carbon monoxide, carbon dioxide, and less than about 5% mol, dry basis, methane. The syngas can be used to indirectly heat the effluent from the first temperature to the second temperature.

Claims

1. ) A method for producing syngas, comprising:

reforming a hydrocarbon in the presence of steam and one or more first catalysts in a first reaction zone to provide an effluent comprising a portion of the hydrocarbon, carbon monoxide, carbon dioxide, and hydrogen at a first temperature, wherein the first reaction zone comprises one or more catalyst-containing tubes;

indirectly heating the effluent from the first temperature to a second temperature; and

reforming the effluent at the second temperature in the presence of one or more oxidants and one or more second catalysts at conditions sufficient to provide a syngas comprising hydrogen, carbon monoxide, carbon dioxide, and less than about 5% mol, dry basis, methane, wherein the syngas is used to indirectly heat the effluent from the first temperature to the second temperature.

2. ) The method of claim 1, wherein the first temperature is about 700°

C. or more.

3. ) The method of claim 1, wherein the temperature of the syngas is about 990°

C. or more.

4. ) The method of claim 1, wherein the second temperature is about 850°

C. or more.

5. ) The method of claim 1, wherein the hydrocarbon comprises methane.

6. ) The method of claim 1, wherein the temperature of the syngas after indirectly heating the effluent from the first temperature to the second temperature is about 880°

C. or more.

7. ) The method of claim 1, wherein heat is indirectly exchanged from the syngas after the syngas is used to indirectly heat the effluent to a condensate to provide high pressure steam.

8. ) The method of claim 1, further comprising reacting the syngas in the presence of one or more third catalysts to convert at least a portion of the carbon monoxide in the cooled syngas to carbon dioxide to provide a converted syngas comprising 5% mol dry basis or less carbon monoxide.

9. ) The method of claim 1, further comprising reacting the cooled syngas in the presence of a catalyst to convert at least a portion of the carbon monoxide in the cooled syngas to carbon dioxide to provide a converted syngas comprising 1% mol dry basis or less carbon monoxide;

separating at least a portion of the carbon dioxide from the converted syngas to provide a first hydrogen product comprising hydrogen, carbon monoxide, and carbon dioxide;

reacting at least a portion of the carbon monoxide and carbon dioxide in the first hydrogen product to provide a second hydrogen product comprising hydrogen, methane, and water; and

reacting at least a portion of the second hydrogen product with nitrogen in the presence of one or more third catalysts to provide an ammonia product.

10. ) The method of claim 1, further comprising reacting the cooled syngas in the presence of one or more third catalysts to convert at least a portion of the carbon monoxide in the cooled syngas to carbon dioxide to provide a converted syngas comprising 1% mol dry basis or less carbon monoxide;

reacting at least a portion of the carbon monoxide and the carbon dioxide in the first hydrogen product to provide a second hydrogen product comprising hydrogen, methane, and water;

separating at least a portion of the water from the second hydrogen product to provide a dried hydrogen product; and

reacting at least a portion of the dried hydrogen product with nitrogen in the presence of one or more third catalysts to provide an ammonia product

11. ) A method for producing syngas, comprising:

reforming a hydrocarbon in the presence of steam and one or more first catalysts in a first reaction zone to provide an effluent at a first temperature, wherein the temperature of the hydrocarbon and steam is monotonically increased to the first temperature;

indirectly heating the effluent at the first temperature to provide an effluent at a second temperature; and

reforming the effluent at the second temperature in the presence of one or more oxidants and one or more second catalysts to provide a syngas, wherein the syngas comprises hydrogen, carbon monoxide, carbon dioxide, nitrogen, and water, and wherein the syngas is used to indirectly heat effluent at the first temperature to the second temperature.

12. ) The method of claim 11, further comprising indirectly exchanging heat from the syngas to a condensate to provide high pressure steam;

and

converting at least a portion of the carbon monoxide in the syngas to carbon dioxide to provide a converted syngas comprising 1% mol dry basis or less carbon monoxide.

13. ) The method of claim 12, further comprising removing at least a portion of the carbon dioxide in the converted syngas to provide a lean syngas comprising 1% mol dry basis or less carbon dioxide and carbon monoxide;

converting at least a portion of any carbon dioxide, carbon monoxide, or both contained in the lean syngas to methane;

separating at least a portion of the water from the lean syngas;

separating at least a portion of the nitrogen in the lean syngas to provide an ammonia syngas having a hydrogen to nitrogen ratio of about 2.9;

1 to about 3.2;

1;

reacting at least a portion of the hydrogen and nitrogen in the ammonia syngas to provide an ammonia product.

14. ) The method of claim 11, wherein the first temperature is about 700°

C. or more.

15. ) The method of claim 11, wherein the temperature of the syngas is about 990°

C. or more.

16. ) The method of claim 11, wherein the second temperature is about 850°

C. or more.

17. ) A system for producing syngas, comprising:

a first reactor adapted to reform a hydrocarbon and steam in the presence of one or more first catalysts to provide an effluent at a first temperature;

a heat exchanger adapted to indirectly exchange heat from a syngas to the effluent at the first temperature to provide a cooled syngas and a second heated effluent; and

a second reactor adapted to reform the effluent at the second temperature in the presence of one or more oxidants and one or more second catalysts to provide the syngas, wherein the syngas comprises hydrogen, carbon monoxide, carbon dioxide, nitrogen, and water.

18. ) The system of claim 17, further comprising a second heat exchanger adapted to indirectly exchange heat from the cooled syngas to a condensate to provide high pressure steam.

19. ) The system of claim 17, further comprising a shift converter adapted to convert at least a portion of the carbon monoxide in the cooled syngas to carbon dioxide to provide a converted syngas;

and a separator adapted to selectively separate at least a portion of the carbon dioxide from the converted syngas to provide a syngas comprising 3% mol dry basis or less carbon monoxide and carbon dioxide.

20. ) The system of claim 19, further comprising an ammonia reactor adapted to react the hydrogen and nitrogen in the syngas to ammonia.