Process and plant for producing pure hydrogen by steam reforming with low carbon dioxide emissions

A process for producing pure hydrogen by steam reforming of a feed gas containing hydrocarbons with reduced carbon dioxide emissions, comprising:

• (a) providing a feed gas stream containing gaseous or evaporated hydrocarbons,
• (b) introducing the feed gas stream heated to a steam reforming inlet temperature into a main reforming stage, converting the feed gas stream in the main reforming stage under steam reforming conditions in a multitude of reformer tubes filled with a solid, particulate reforming catalyst to a crude synthesis gas stream containing hydrogen, carbon monoxide, carbon dioxide and unconverted hydrocarbons, wherein the reformer tubes are disposed in a reformer furnace, the interior of which is heated by means of a multitude of burners, with formation of a steam reforming flue gas stream, and wherein the steam reforming conditions comprise the addition of steam to the feed gas containing hydrocarbons and the establishment of a defined steam/carbon ratio,
• (c) discharging the crude synthesis gas stream from the main reforming stage and introducing the crude synthesis gas stream into a first heat recovery apparatus, cooling the crude synthesis gas stream in the first heat recovery apparatus in indirect heat exchange with a first coolant stream, discharging the cooled crude synthesis gas stream from the first heat recovery apparatus,
• (d) introducing the cooled crude synthesis gas stream into a carbon monoxide conversion plant comprising at least one carbon monoxide conversion stage, converting the cooled crude synthesis gas stream introduced into the carbon monoxide conversion plant under carbon monoxide conversion conditions to a converted synthesis gas stream, discharging the converted synthesis gas stream that has been enriched in hydrogen and carbon dioxide and depleted of carbon monoxide compared to the crude synthesis gas stream,
• (e) introducing the converted synthesis gas stream into a second heat recovery apparatus, cooling the converted synthesis gas stream in the second heat recovery apparatus in indirect heat exchange with a second coolant stream, discharging the cooled converted synthesis gas stream from the second heat recovery apparatus,
• (f) introducing the cooled converted synthesis gas stream into a hydrogen enrichment apparatus that works by the principle of pressure swing adsorption, discharging a pure hydrogen product stream and at least one pressure swing adsorptionPSA tail gas stream from the hydrogen enrichment apparatus, wherein the at least one pressure swing adsorption tail gas stream comprises carbon monoxide, carbon dioxide and unconverted hydrocarbons,
• (g) introducing at least a portion of the at least one pressure swing adsorption tail gas stream into a first carbon dioxide separation apparatus, configured as an apparatus for cryogenic carbon dioxide capture, and discharging the following streams from the first carbon dioxide separation apparatus:
• (g1) a stream enriched in carbon dioxide compared to the pressure swing adsorption tail gas stream, which is discharged from the process as the first carbon dioxide-rich stream,
• (g2) a stream enriched in hydrogen compared to the pressure swing adsorption tail gas stream, which is recycled to process step (f),
• (g3) a cryogenic carbon dioxide captureCCC tail gas stream that has been depleted of carbon dioxide and hydrogen compared to the pressure swing adsorptionPSA tail gas stream and comprises carbon monoxide and unconverted hydrocarbons,
• (h) introducing at least a portion of the cryogenic carbon dioxide capture tail gas stream into at least one burner in the reformer furnace, burning the at least one portion of the at least one cryogenic carbon dioxide capture tail gas stream with combustion air and with a trim gas stream containing hydrocarbons, wherein the reformer tubes in the reformer furnace are heated and the steam reforming flue gas stream is formed, discharging the steam reforming flue gas stream from the reformer furnace,
• (i) introducing the steam reforming flue gas stream into a second carbon dioxide separation apparatus that works by means of a physical or chemical carbon dioxide separation process, discharging a carbon dioxide-depleted steam reforming flue gas stream from the second carbon dioxide separation apparatus, discharging a second carbon dioxide-rich stream.