Chemical synthesis plant

1. A plant, said plant comprising:

a. a syngas stage, said syngas stage comprising a methanation section and/or a reverse water gas shift (rWGS) section, and an autothermal reforming (ATR) section; and

b. a synthesis stage,

said plant further comprising:

a first feed comprising hydrogen to the syngas stage;

a second feed comprising carbon dioxide to the syngas stage; and

a third feed comprising oxygen to the ATR section,

wherein said syngas stage is arranged to provide a syngas stream and feed said syngas stream to the synthesis stage, and

wherein the plant does not comprise an external feed of hydrocarbons,

wherein the syngas stage comprises a methanation section and/or a reverse water gas shift (rWGS) section, arranged upstream the autothermal reforming (ATR) section,

wherein the synthesis stage is arranged to convert said syngas stream into at least a product stream and a hydrocarbon-containing off-gas stream, and

wherein at least a portion of said hydrocarbon-containing off-gas stream or at least a portion of said product stream is fed to the syngas stage as a fourth feed comprising hydrocarbons, upstream of said ATR section and between said methanation section and/or said reverse water gas shift (rWGS) section and said ATR section.

2. The plant according to claim 1 , wherein the syngas stream is fed directly from the syngas stage to the synthesis stage.

3. The plant according to claim 1 , wherein the plant comprises a post-conversion section, located between said syngas stage and said synthesis stage, and a stream comprising CO 2 to said post-conversion section, arranged to be mixed with the syngas stream between the syngas stage and the post-conversion section.

4. The plant according to claim 1 , further comprising a fifth feed of steam to the syngas stage.

5. The plant according to claim 1 , wherein the syngas stage consists of a methanation section arranged upstream an autothermal reforming (ATR) section.

6. The plant according to claim 1 , wherein a part or all of the first feed is fed to the methanation section; and a part or all of the second feed is fed to the methanation section.

7. The plant according to claim 1 , wherein the methanation section comprises two or more methanation units.

8. The plant according to claim 1 , wherein the syngas stream at the inlet of said synthesis stage has a hydrogen/carbon monoxide ratio in the range 1.0-4.0.

9. The plant according to claim 1 , wherein the ratio of H 2 :CO 2 provided at the plant inlet is between 1.0-9.0.

10. The plant according to claim 9 , wherein the synthesis stage is a Fischer-Tropsch (F-T) synthesis stage and the H 2 :CO 2 -ratio at the plant inlet is in the range of 3.0-7.0.

11. The plant according to claim 1 , wherein the synthesis stage is a Fischer-Tropsch (F-T) stage arranged to convert said syngas stream into at least a hydrocarbon product stream and a hydrocarbon-containing off-gas stream in the form of an F-T tail gas stream.

12. The plant according to claim 1 , in which the synthesis stage comprises a methanol synthesis stage arranged to provide at least a methanol product stream and a methanol off-gas stream, and wherein at least a portion of said methanol off-gas stream is fed to the syngas stage.

13. The plant according to claim 1 , further comprising an electrolyser arranged to convert water or steam into at least a hydrogen-containing stream and an oxygen-containing stream, and wherein at least a part of said hydrogen-containing stream from the electrolyser is fed to the syngas stage as part or all of said first feed and/or wherein at least a part of said oxygen-containing stream from the electrolyser is fed to the syngas stage as part or all said third feed.

14. The plant according to claim 1 , comprising a sixth feed of hydrogen to the syngas stream, upstream the synthesis stage.

15. The plant according to claim 1 , wherein a part or all of the first feed is fed to the methanation section and/or reverse water gas shift (rWGS) section; and a part or all of the second feed is fed to the methanation section and/or reverse water gas shift (rWGS) section.

16. The plant according to claim 1 , wherein:

the syngas stage comprises a reverse water gas shift (rWGS) section arranged in parallel to said ATR section;

wherein at least a portion of the first feed and at least a portion of the second feed are arranged to be fed to the rWGS section and said rWGS section is arranged to convert said at least a portion of the first feed and at least a portion of the second feed to a first syngas stream;

wherein a third feed comprising oxygen is arranged to be fed to the ATR section;

wherein said ATR section is arranged to convert said third feed comprising oxygen and said fourth feed comprising hydrocarbons to a second syngas stream; and

wherein the first syngas stream from the rWGS section is arranged to be combined with the second syngas stream from the ATR section; and the combined syngas stream is arranged to be fed to the synthesis stage.

17. The plant according to claim 16 , wherein, before being combined with the first syngas stream, the syngas stream from the ATR section is arranged to provide at least a part of the energy required for the endothermic reaction in the rWGS section.

18. The plant according to claim 1 , wherein:

the syngas stage comprises a methanation section arranged in parallel to said ATR section;

wherein at least a portion of the first feed and at least a portion of the second feed are arranged to be fed to the methanation section and said methanation section is arranged to convert said at least a portion of the first feed and at least a portion of the second feed to a first syngas stream;

wherein a third feed comprising oxygen is arranged to be fed to the ATR section;

wherein said ATR section is arranged to convert said third feed comprising oxygen and said fourth feed comprising hydrocarbons to a second syngas stream; and

wherein the first syngas stream from the methanation section is arranged to be combined with the second syngas stream from the ATR section; and the combined syngas stream is arranged to be fed to the synthesis stage.

19. A method for producing a product stream, said method comprising the steps of:

providing a plant as defined in claim 1 ;

supplying a first feed comprising hydrogen to the syngas stage;

supplying a second feed comprising carbon dioxide to the syngas stage;

supplying a third feed comprising oxygen to the ATR section;

converting said first, second, and third feeds in said syngas stage to a syngas stream and feeding said syngas stream to the synthesis stage, wherein the syngas stage comprises a methanation section and/or a reverse water gas shift (rWGS) section, arranged upstream the autothermal reforming (ATR) section;

converting said syngas stream in said synthesis stage into at least a product stream and a hydrocarbon-containing stream; and

feeding at least a portion of said hydrocarbon-containing stream or at least a portion of said product stream to the syngas stage as a fourth feed comprising hydrocarbons, upstream of said ATR section and between the methanation section and/or the reverse water gas shift (rWGS) section and said ATR section.

20. The method according to claim 19 , in which the synthesis stage is a Fischer-Tropsch (F-T) stage arranged to convert said syngas stream into at least a hydrocarbon product stream and a hydrocarbon-containing off-gas stream in the form of an F-T tail gas stream.