PROCESS FOR PRODUCING HYDROGEN AND METHOD OF RETROFITTING A HYDROGEN PRODUCTION UNIT

1 . A plant for the production of hydrogen, comprising:

a fired reformer containing a plurality of catalyst-containing reformer tubes and having a shell side to which fuel is fed, operable to produce a crude synthesis gas from a feed stream containing a hydrocarbon and steam;

an autothermal reformer arranged to be fed with an oxygen-containing gas and a crude synthesis gas from the fired reformer, operable to produce a reformed synthesis gas;

a water-gas shift unit arranged to be fed with a reformed synthesis gas recovered from the autothermal reformer, operable to produce a hydrogen-enriched gas;

a carbon dioxide removal unit arranged to be fed with a hydrogen-enriched gas from the water-gas shift unit, operable to produce a crude hydrogen stream and a carbon dioxide stream; and

a purification unit arranged to be fed with a crude hydrogen stream gas from the carbon dioxide removal unit, operable to produce a hydrogen product stream and an off-gas stream,

wherein the plant is arranged such that a portion of the crude hydrogen stream from the carbon dioxide removal unit and/or a portion of hydrogen product stream from the purification unit is fed as fuel to a shell-side of the fired reformer.

2 . The plant according to claim 1 , wherein the water-gas shift unit comprises a high-temperature shift stage followed by one or more medium-temperature shift stages and/or one or more low-temperature shift stages.

3 . The plant according to claim 1 , wherein the carbon dioxide removal unit operates by means of a physical wash system or a reactive wash system.

4 . The plant according to claim 1 , wherein the carbon dioxide removal unit operates by means of an amine wash system.

5 . The plant according to claim 1 , wherein the purification unit operates by pressure swing adsorption and/or temperature swing adsorption.

6 . The plant according to claim 1 , wherein the plant is arranged such that at least a portion of the off-gas stream is fed to the fired reformer feed stream.

7 . The plant according to claim 1 , wherein the plant is arranged such that the reformed synthesis gas from the autothermal reformer is used to produce high-pressure steam.

8 . A process for the production of hydrogen, comprising the steps of:

feeding a mixture of hydrocarbon and steam to a fired reformer containing a plurality of catalyst-containing reformer tubes to produce a crude synthesis gas;

feeding a fuel to the shell-side of the fired reformer to provide heat for the steam reforming reactions taking place in the catalyst-containing reformer tubes;

feeding the crude synthesis gas from the fired reformer to an autothermal reformer along with an oxygen-containing gas to produce a reformed synthesis gas;

feeding the reformed synthesis gas to a water-gas shift unit to produce a hydrogen-enriched gas;

feeding the hydrogen-enriched gas to a carbon dioxide removal unit and separating the hydrogen-enriched gas into a crude hydrogen stream and a carbon dioxide stream;

feeding the crude hydrogen stream to a purification unit and separating the crude hydrogen stream into a hydrogen product stream and an off-gas stream; and

feeding a portion of the crude hydrogen stream and/or a portion of hydrogen product stream as fuel to the shell-side of the fired reformer.

9 . The process according to claim 8 , wherein the process is carried out in a plant for the production of hydrogen, comprising:

a fired reformer containing a plurality of catalyst-containing reformer tubes and having a shell side to which fuel is fed, operable to produce a crude synthesis gas from a feed stream containing a hydrocarbon and steam;

an autothermal reformer arranged to be fed with an oxygen-containing gas and a crude synthesis gas from the fired reformer, operable to produce a reformed synthesis gas;

a water-gas shift unit arranged to be fed with a reformed synthesis gas recovered from the autothermal reformer, operable to produce a hydrogen-enriched gas;

a carbon dioxide removal unit arranged to be fed with a hydrogen-enriched gas from the water-gas shift unit, operable to produce a crude hydrogen stream and a carbon dioxide stream; and

a purification unit arranged to be fed with a crude hydrogen stream gas from the carbon dioxide removal unit, operable to produce a hydrogen product stream and an off-gas stream,

wherein the plant is arranged such that a portion of the crude hydrogen stream from the carbon dioxide removal unit and/or a portion of hydrogen product stream from the purification unit is fed as a fuel to a shell-side of the fired reformer.

10 . The process according to claim 8 , wherein the hydrocarbon in the mixture of hydrocarbon and steam comprises natural gas, associated gas, LPG, petroleum distillate, diesel, naphtha or mixtures thereof, a refinery off-gas, or a pre-reformed gas.

11 . The process according to claim 8 , wherein the hydrocarbon in the mixture of hydrocarbon and steam comprises natural gas.

12 . The process according to claim 8 , wherein the mixture of hydrocarbon and steam fed to the fired reformer has a ratio of 1.5 to 3.5 moles of steam per mole of hydrocarbon carbon.

13 . The process according to claim 8 , wherein the fuel to the shell-side of the fired reformer comprises at least 75% vol H2.

14 . The process according to claim 8 , wherein the fuel to the shell-side of the fired reformer comprises at least 95% vol H2.

15 . The process according to claim 8 , wherein the oxygen-containing gas is selected from air, oxygen-enriched air or oxygen.

16 . The process according to claim 8 , wherein the autothermal reformer is sized to provide essentially all of the hydrogen used as fuel in the fired reformer.

17 . The process according to claim 8 , wherein carbon dioxide recovered from the carbon dioxide removal unit is:

compressed and used for the manufacture of chemicals;

purified for use in the food industry or greenhouse applications;

sent to storage or sequestration; and/or

used in enhanced oil recovery processes.

18 . The process according to claim 8 , wherein the mixture of hydrocarbon and steam fed to the fired reformer includes at least a portion of the off-gas stream.

19 . A method of retrofitting an existing hydrogen plant, said existing hydrogen plant comprising:

a fired reformer containing a plurality of catalyst-containing reformer tubes and having a shell side to which fuel is fed, operable to produce a crude synthesis gas;

a water-gas shift unit arranged to be fed with a crude synthesis gas recovered from the fired reformer, operable to produce a hydrogen-enriched gas; and

a purification unit arranged to be fed with a hydrogen-enriched gas from the water-gas shift unit, operable to produce a hydrogen product stream and an off-gas stream;

the method comprising the steps of:

installing an autothermal reformer downstream from the fired reformer and upstream from the water-gas shift unit, arranged to be fed with an oxygen-containing gas and a crude synthesis gas from the fired reformer, operable to produce a reformed synthesis gas;

installing a carbon dioxide removal unit downstream from the water-gas shift unit and upstream from the purification unit, arranged to be fed with a hydrogen-enriched gas from the water-gas shift unit, operable to produce a crude hydrogen stream and a carbon dioxide stream;

providing means for feeding a crude hydrogen stream from the carbon dioxide removal unit to the purification unit; and

providing means for feeding a portion of the crude hydrogen stream from the carbon dioxide removal unit and/or a portion of the hydrogen product stream from the purification unit as fuel to the shell-side of the fired reformer.

20 . The method according to claim 19 , wherein the resulting retrofitted hydrogen plant for the production of hydrogen, comprises:

a fired reformer containing a plurality of catalyst-containing reformer tubes and having a shell side to which fuel is fed, operable to produce a crude synthesis gas from a feed stream containing a hydrocarbon and steam;

an autothermal reformer arranged to be fed with an oxygen-containing gas and a crude synthesis gas from the fired reformer, operable to produce a reformed synthesis gas;

a water-gas shift unit arranged to be fed with a reformed synthesis has recovered from the autothermal reformer, operable to produce a hydrocarbon-enriched gas;

a carbon dioxide removal unit arranged to be fed with a hydrogen-enriched gas from the water-gas shift unit, operable to produce a crude hydrogen stream and a carbon dioxide stream; and

a purification unit arranged to be fed with a crude hydrogen stream gas from the carbon dioxide removal unit, operable to produce a hydrogen product stream and an off-gas stream,

wherein the plant is arranged such that a portion of the crude hydrogen stream from the carbon dioxide removal unit and/or a portion of hydrogen product stream from the purification unit is fed as fuel to a shell-side of the fired reformer.

21 . The method according to claim 19 , wherein the method includes the step of installing a heat exchanger between the outlet of the autothermal reformer and the water-gas shift unit.

22 . The method according to claim 19 , wherein the method includes the step of installing a replacement or additional waste heat boiler.

23 . The method according to claim 19 , wherein the method includes the step of expanding the capacity of the water-gas shift unit.

24 . The method according to claim 19 , wherein the method includes the step of installing one or more medium- or low-temperature shift stages downstream from an existing high-temperature shift stage.

25 . The method according to claim 19 , wherein the method includes the step of converting an existing water-gas shift stage from axial flow to axial-radial or radial flow.