Carbon monoxide production process optimized by SOEC

Abstract

The invention concerns a process for producing carbon monoxide (CO) from a feed stream comprising carbon dioxide (CO2) and natural gas and/or naphtha the process comprising a syngas generation step, a CO2 removal step and a CO purification step and the process further comprises an SOEC unit which produces CO from a CO2 stream, the process is especially suited for increasing the capacity of existing known CO production plants.

Claims

1. A process for producing carbon monoxide (CO) from a feed stream comprising carbon dioxide (CO2) and natural gas and/or naphtha, the process comprising a syngas generation step where a first syngas stream is generated from the feed stream through a steam reforming process, a CO2 removal step where at least a part of the CO2 is removed from the first syngas stream and the thereby generated CO2 recycle stream is recycled back to the syngas generation step, and a second syngas stream is generated in said CO2 removal step, and a CO purification step where CO is generated from the second syngas stream, wherein the process further comprises an SOEC unit which is fed by a CO2 stream, the SOEC unit generates CO which is fed back into the first syngas stream, thereby raising the CO concentration in the first syngas stream.

2. The process according to claim 1, wherein the CO2 stream which is fed to the SOEC unit is a recycle by-pass stream comprising at least a part of said CO2 recycle stream.

3. The process according to claim 2, wherein the SOEC unit comprises a compressor adapted to enable the CO2 recycle by-pass stream to overcome a pressure difference, through the SOEC unit, between the CO2 recycle stream and piping, wherein the CO2 recycle stream is fed back into the first syngas stream.

4. The process according to claim 3, wherein the SOEC unit comprises a pressure reduction valve downstream of the CO2 recycle stream to protect the SOEC unit from excess pressure.

5. The process according to claim 1, comprising a CO2 import stream which is fed to the syngas generation step.

6. The process according to claim 1, comprising a CO2 import stream which is fed to the SOEC unit.

7. The process according to claim 1, wherein the SOEC unit converts 5-99% of the CO2 fed to the SOEC unit to CO.

8. The process according to claim 1, wherein the SOEC unit converts 20-60% of the CO2 fed to the SOEC unit to CO.

9. The process according to claim 1, wherein the pressure of the first syngas stream is 2-25 Bar.

10. The process according to claim 1, wherein the pressure of the first syngas stream is 15-25 Bar.

11. The process according to claim 1, wherein the pressure of the CO2 recycle stream is 0-5 Bar.

12. The process according to claim 1, wherein the syngas generation step comprises hydrogenation, desulphurization, pre-reforming and reforming or any combination thereof of the feed stream.

13. The process according to claim 1, wherein the CO purification step comprises cryogenic or membrane CO purification.

Description

DESCRIPTION OF THE DRAWINGS

(1) The invention is further illustrated by the accompanying drawings showing examples of embodiments of the invention.

(2) FIG. 1 shows a diagram of the process according to an embodiment of the invention, and

(3) FIG. 2 shows a diagram of the process according to another embodiment of the invention.

POSITION NUMBERS

(4) 01. Feed stream 02. Syngas generation step 03. First syngas stream. 04. CO2 removal step. 05. CO2 recycle stream. 06. Second syngas stream. 07. CO purification step. 08. SOEC unit. 09. CO2 stream. 10. CO2 import stream. 11. Pressure reduction valve.

(5) The diagram in FIG. 1 shows the CO production process according to an embodiment of the invention. A feed stream, 01 comprising natural gas and/or naphtha feed is led to the syngas generation step, 02, where it is transformed to syngas by a catalytic reaction. The thereby generated first syngas stream, 03 is then led to the CO2 removal step, which generates a CO2 recycle stream which is recycled back into the feed stream by means of a CO2 recycle compressor and a second syngas stream, 06, which is passed further on to the CO purification step, 07 via the syngas dryer. A CO product stream is formed from the second syngas stream by the reaction taking place in the CO purification step.

(6) To increase the efficiency of this known process, an SOEC unit is added to the process, which generates CO from CO2. In the present embodiment, the SOEC unit is fed by at least a part of the CO2 recycle stream which is generated in the CO2 removal step. The CO generated in the SOEC is then fed back into the first syngas stream, thereby increasing the CO concentration of this stream and increasing the overall CO production capacity of the existing process. As the capacity of the existing process is increased, it may be feasible to apply a CO2 import stream, 10 to the system, which may be fed into the CO2 recycle stream. Accordingly the present invention is well suited for revamping existing CO-production plants, increasing their CO production capacity without major equipment replacement.

(7) In the embodiment of the invention according to FIG. 2, the SOEC unit is fed directly by the CO2 import stream. This embodiment may be advantageous as it requires a minimum of piping and revamping of the existing plant.