Methods and systems for producing and processing syngas in a pressure swing adsorption unit and making ammonia therefrom

• US 9,561,968 B2
• Filed: 08/05/2014
• Issued: 02/07/2017
• Est. Priority Date: 08/07/2013
• Status: Active Grant

• Current Assignee: Kellogg Brown & Root LLC (KBR Incorporated)
• Original Assignee: Kellogg Brown & Root LLC (KBR Incorporated)
• Inventors: Nahar, Akhil Jain, Singh, Shashi Prakash, Noe, Stephen Allen
• Primary Examiner(s): LANGEL, WAYNE A
• Application Number:
  US14/452,463
• Publication Number:
  US 20150044120A1
• Time in Patent Office: 917 Days
• US Class Current: 1/1
• CPC Class Codes: B01J 19/00 Chemical, physical or physico-chemical processes in general; Their relevant apparatus
• CPC Class Codes: C01B 2203/0233 the reforming step being a steam reforming step
• CPC Class Codes: C01B 2203/0283 containing a CO-shift step, i.e. a water gas shift step
• CPC Class Codes: C01B 2203/043 Regenerative adsorption process in two or more beds, one for adsorption, the other for regeneration
• 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 2203/068 Ammonia synthesis
• CPC Class Codes: C01B 2203/141 At least two reforming, decomposition or partial oxidation steps in parallel
• CPC Class Codes: C01B 2203/142 At least two reforming, decomposition or partial oxidation steps in series
• CPC Class Codes: C01B 2203/143 Three or more reforming, decomposition or partial oxidation steps in series
• 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 3/12 by reaction of water vapour with carbon monoxide
• CPC Class Codes: C01B 3/38 using catalysts
• CPC Class Codes: C01C 1/04 Preparation of ammonia by synthesis in the gas phasepreparation or purification of gas mixtures for ammonia synthesis C01B3/025
• CPC Class Codes: C01C 1/0405 from N2 and H2 in presence of a catalyst
• CPC Class Codes: C01C 1/0458 Separation of NH3 during purge gas treatment C01C1/0476
• CPC Class Codes: Y02P 20/129 Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

Methods and systems for making ammonia are provided. The method can include converting carbon monoxide in a first syngas to carbon dioxide to produce a shifted syngas. At least a portion of the carbon dioxide can be separated from the shifted syngas to produce a carbon dioxide-lean syngas. Carbon monoxide and/or carbon dioxide in the carbon dioxide-lean syngas can be converted to methane to produce a methanated first syngas. A second syngas can be separated to produce a purified second syngas and a waste gas. The methanated first syngas and the purified second syngas can be combined to produce an ammonia feedstock. The ammonia feedstock can have a hydrogen to nitrogen molar ratio of about 3.5:1 to about 2.5:1. At least a portion of the hydrogen and nitrogen in the ammonia feedstock can be reacted to produce an ammonia product.

Claims

1. A method for making ammonia, comprising:

converting a first syngas comprising carbon dioxide and about 8 mol % to about 20 mol % carbon monoxide to produce a shifted syngas comprising carbon dioxide and about 0.1 mol % to about 1 mol % carbon monoxide;

separating at least a portion of the carbon dioxide from the shifted syngas to produce a carbon dioxide-lean syngas;

converting at least a portion of the carbon monoxide, carbon dioxide, or both in the carbon dioxide-lean syngas to methane to produce a methanated first syngas having a hydrogen to nitrogen molar ratio of about 1.5;

1 to about 3.5;

1;

separating a second syngas comprising carbon dioxide and about 7 mol % to about 20 mol % carbon monoxide to produce a purified second syngas having a hydrogen to nitrogen molar ratio of about 2;

1 to about 50;

1 and a waste gas having a carbon monoxide concentration of about 0.2 mol % to about 60 mol %;

combining at least a portion of the methanated first syngas and at least a portion of the purified second syngas to produce an ammonia feedstock having a hydrogen to nitrogen molar ratio of about 2.5;

1 to about 3.5;

1; and

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

2. The method of claim 1, wherein the ammonia feedstock has a carbon monoxide concentration of up to about 0.1 mol %, and a carbon dioxide concentration of up to about 0.1 mol %.

3. The method of claim 1, further comprising:

reforming a first hydrocarbon in the presence of steam to produce an effluent;

separating the effluent into a first effluent and a second effluent;

reforming the first effluent in the presence of an oxidant to produce a reformed effluent;

combining the reformed effluent with a second hydrocarbon;

reforming the combined reformed effluent and second hydrocarbon to produce the first syngas; and

reforming the second effluent to produce the second syngas.

4. The method of claim 3, wherein the combined reformed effluent and second hydrocarbon are reformed in a reforming exchanger to produce the first syngas, wherein the first syngas is at a temperature of about 700°

C. to about 900°

C.

5. The method of claim 1, wherein the second syngas is separated in a pressure swing adsorption unit having a typical hydrogen recoveries of about 60% to about 98%.

6. The method of claim 1, further comprising:

reforming a first hydrocarbon in the presence of steam to produce a first effluent;

reforming the first effluent in the presence of an oxidant to produce a reformed effluent;

combining the reformed effluent with a second hydrocarbon;

reforming the combined reformed effluent and second hydrocarbon to produce the first syngas; and

separating the syngas into the first syngas and the second syngas.

7. The method of claim 1, further comprising converting at least a portion of the carbon monoxide, carbon dioxide, or both contained in the purified second syngas to methane.

8. The method of claim 1, further comprising converting at least a portion of the carbon monoxide, carbon dioxide, or both contained in the purified second syngas to methane in a methanator.

9. The method of claim 1, wherein the first syngas is at a pressure of about 2,000 kPa to about 5,500 kPa.

10. The method of claim 1, further comprising:

separating a purge gas from the ammonia product and combining the purge gas with the second syngas prior to separating the second syngas.

11. A method for making ammonia, comprising:

converting a first syngas comprising carbon dioxide and about 8 mol % to about 20 mol % carbon monoxide to produce a shifted syngas comprising carbon dioxide and about 0.1 mol % to about 1 mol % carbon monoxide;

separating at least a portion of the carbon dioxide from the shifted syngas to produce a carbon dioxide-lean syngas;

converting at least a portion of the carbon monoxide, carbon dioxide, or both in the carbon dioxide-lean syngas to methane to produce a methanated first syngas having a hydrogen to nitrogen molar ratio of about 1.5;

1 to about 3.5;

1, and a carbon monoxide concentration of up to about 0.05 mol %;

separating a second syngas comprising carbon dioxide and about 7 mol % to about 20 mol % carbon monoxide to produce a purified second syngas having a hydrogen to nitrogen molar ratio of about 2;

1 to about 50;

1 and a waste gas having a carbon monoxide concentration of about 0.2 mol % to about 60 mol %;

combining at least a portion of the methanated first syngas and at least a portion of the purified second syngas to produce an ammonia feedstock having a hydrogen to nitrogen molar ratio of about 2.5;

1 to about 3.5;

1; and

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

12. The method of claim 11, wherein the first syngas has a hydrogen concentration of about 40 mol % to about 65 mol % and wherein the second syngas gas a hydrogen concentration of about 35 mol % to about 65 mol %.

13. The method of claim 11, wherein the at least a portion of the carbon monoxide present in the first syngas is converted to carbon dioxide in a first high temperature shift converter operated at a temperature of about 320°

C. to about 425°

C. and wherein the second syngas is separated in a pressure swing adsorption unit at a typical hydrogen recovery of about 70% to about 98%.

14. The method of claim 11, wherein the second syngas has a hydrogen concentration of about 35 mol % to about 65 mol %, a carbon monoxide concentration of about 7 mol % to about 20 mol %, and a carbon dioxide concentration of about 4 mol % to about 20 mol %, and

wherein the purified second syngas has a hydrogen concentration of about 75 mol % to about 99.5 mol %, a carbon monoxide concentration of up to about 0.25 mol %, and a carbon dioxide concentration of up to about 0.25 mol %.