Methanol production process and system
A process and a system are disclosed for producing methanol from synthesis gas. The synthesis gas is a stream containing H 2 , CO, and CO 2 that is created using a nitrogen containing oxidant stream, such as air. The synthesis gas is then reacted through a conventional reactor system to create methanol. Unreacted synthesis gas is recycled back through the reactor system. The disclosed methanol production process can be mounted and operated on a seagoing vessel.
1. A process for producing methanol, comprising the steps of:
providing a synthesis gas stream comprising H 2 , CO, and CO 2 , and N 2 ; wherein the synthesis gas stream comprises at least about 6 mole % N 2 and wherein the synthesis gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO), which is less than about 1.80;
combining the synthesis gas stream with a hydrogen-rich gas stream to form a makeup gas stream;
combining the makeup gas stream with a recycle gas stream to produce a reactor feed stream;
introducing the reactor feed stream into a reactor system containing a methanol conversion catalyst; wherein a portion of the reactor feed stream is converted to methanol;
withdrawing a reacted gas stream from the reactor system;
separating the reacted gas stream into a crude methanol product stream and a gas stream;
splitting the gas stream into a recycle gas stream and a purge gas stream;
mixing the recycle gas stream with the makeup gas stream to form the reactor feed stream;
separating the purge gas stream into a fuel gas stream comprising CH 4 and N 2 and a hydrogen-rich stream comprising H 2 ; and
mixing the hydrogen-rich stream into the synthesis gas stream.
2. The process of claim 1 wherein the synthesis gas stream comprises at least about 8 mole % N 2 .
3. The process of claim 1 wherein the synthesis gas stream comprises at least about 20 mole % N 2 .
4. The process of claim 1 wherein the synthesis gas stream comprises at least about 35 mole % N 2 .
5. The process of claim 1 wherein the synthesis gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO), which is less than about 1.77.
6. The process of claim 1 wherein the synthesis gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO), which is less than about 1.73.
7. The process of claim 1 wherein the synthesis gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO), which is between about 1.34 and about 1.80.
8. The process of claim 1 wherein the makeup gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO), which is at least about 2.05.
9. The process of claim 1 wherein the makeup gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO), which is at least about 2.4.
10. The process of claim 1 wherein the makeup gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO), which is at least about 3.6.
11. The process of claim 1 further comprising the steps of:
providing an air stream having an oxygen content less than about 22%;
enhancing the oxygen content of the air stream to between about 28% and 94% oxygen thereby creating an enhanced oxygen stream;
providing a natural gas stream comprising methane; and
partially oxidizing the natural gas stream in an autothermal reformer using the enhanced oxygen stream to create a synthesis gas stream comprising H 2 , CO, and CO 2 and N 2 .
12. The process of claim 1 wherein the natural gas is converted to methanol on a seagoing vessel.
13. A process for producing methanol, comprising the steps of:
providing an air stream having an oxygen content less than about 22%;
enhancing the oxygen content of the air stream to between about 28% and 94% oxygen thereby creating an enhanced oxygen stream;
providing a natural gas stream comprising methane;
partially oxidizing the natural gas stream in an autothermal reformer using the enhanced oxygen stream to create a synthesis gas stream comprising H 2 , CO, and CO 2 and N 2 ;
combining the synthesis gas stream with a hydrogen-rich gas stream to form a makeup gas stream, wherein the synthesis gas stream composition remains substantially unchanged after exiting the autothermal reformer until combined with the hydrogen-rich gas stream;
combining the makeup gas stream with a recycle gas stream to produce a reactor feed stream;
introducing the reactor feed stream into a reactor system containing a methanol conversion catalyst; wherein a portion of the reactor feed stream is converted to methanol;
withdrawing a reacted gas stream from the reactor system;
separating the reacted gas stream into a crude methanol product stream and a gas stream;
splitting the gas stream into a recycle gas stream and a purge gas stream;
combining the recycle gas stream with the makeup gas stream to form the reactor feed stream;
separating the purge gas stream into a fuel gas stream comprising CH 4 , and N 2 and a hydrogen-rich stream comprising H 2 ; and
mixing the hydrogen-rich stream into the synthesis gas stream.
14. The process of claim 13 wherein the oxygen content of the air stream is enhanced to between about 28% and 70%.
15. The process of claim 13 wherein the oxygen content of the air stream is enhanced to between about 35% and 50%.
16. The process of claim 13 wherein the synthesis gas stream comprises at least about 6 mole % N 2 .
17. The process of claim 13 wherein the synthesis gas stream comprises at least about 8 mole % N 2 .
18. The process of claim 13 wherein the synthesis gas stream comprises at least about 20 mole % N 2 .
19. The process of claim 13 wherein the synthesis gas stream comprises at least about 35 mole % N 2 .
20. The process of claim 13 wherein the natural gas is converted to methanol on a seagoing vessel.
21. A process for producing methanol, comprising the steps of:
providing a synthesis gas stream comprising H 2 , CO, and CO 2 and N 2 ; wherein the synthesis gas stream comprises at least about 16 mole % N 2 and wherein the synthesis gas stream comprises H 2 , CO, and CO 2 in a ratio of (H 2 —CO 2 )/(CO 2 +CO) of about 1.73;
combining the synthesis gas stream with a hydrogen-rich gas stream to form a makeup gas stream;
combining the makeup gas stream with a recycle gas stream to produce a reactor feed stream;
introducing the reactor feed stream into a reactor system containing a methanol conversion catalyst; wherein a portion of the reactor feed stream is converted to methanol;
withdrawing a reacted gas stream from the reactor system;
separating the reacted gas stream into a crude methanol product stream and a gas stream;
splitting the gas stream into a recycle gas stream and a purge gas stream;
mixing the recycle gas stream with the makeup gas stream to form the reactor feed stream;
separating the purge gas stream into a fuel gas stream comprising CH 4 and N 2 and a hydrogen-rich stream comprising H 2 ; and
mixing the hydrogen-rich stream into the synthesis gas stream.