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

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 %.