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

Patent metadata

Field	Value
Publication number	US-9561968-B2
Application number	US-201414452463-A
Country	US
Kind code	B2
Filing date	Aug 5, 2014
Priority date	Aug 7, 2013
Publication date	Feb 7, 2017
Grant date	Feb 7, 2017

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.

First claim

What is claimed is:

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 %.

Assignees

• Kellogg Brown & Root Llc

Inventors

• Singh Shashi Prakash
• Nahar Akhil Jain
• Noe Stephen Allen

Classifications

• Y02P20/52

  using catalysts, e.g. selective catalysts · CPC title

• C01B2203/0475

  the impurity being carbon dioxide · CPC title

• C01B2203/0445

  Selective methanation · CPC title

• C01B2203/0283

  containing a CO-shift step, i.e. a water gas shift step · CPC title

• C01B2203/047

  the impurity being carbon monoxide · CPC title