Process for recovering hydrogen and carbon dioxide

A process for producing hydrogen and capturing carbon dioxide from a hydrocarbon containing feed stream (16) in a hydrogen generation plant, the process comprising the steps of:

• a) optionally pre-reforming the hydrocarbon containing feed stream (16) in at least one pre-reformer (17) to form a pre-reformed gas stream (18);
• b) reforming the pre-reformed gas stream (18) in a steam methane reformer unit (19) to obtain a syngas stream (20);
• c) subjecting the syngas stream (20) to a shift reaction in a water gas shift reactor (21) to obtain a feed gas (15);
• d) subjecting the feed gas (15) to hydrogen purification in a process unit (0) to obtain a hydrogen product stream (23) and a hydrogen depleted process stream (1);
• e) withdrawing the hydrogen product stream (23) and using a portion of this hydrogen product stream (23) as a fuel for the steam methane reformer unit (19);
• f) optionally compressing the process stream (1) in a first compressor (2);
• g) cooling the process stream (1) in a heat exchanger (3) to a temperature equal to or less than −10° C.;
• h) separating and purifying the cooled process stream (1) in a carbon dioxide separation unit (4) to produce a carbon dioxide rich liquid stream (6) and a carbon dioxide lean non-condensable stream (5);
• i) withdrawing the carbon dioxide rich liquid stream (6) as a carbon dioxide product for further use;
• j) withdrawing the carbon dioxide lean non-condensable stream (5) from the carbon dioxide separation unit (4) and passing the carbon dioxide lean non-condensable stream (5) through a hydrogen selective membrane separation unit (7) to form a hydrogen rich permeate stream (8) with the remaining components in the carbon dioxide lean non-condensable stream (5) forming a hydrogen lean residue stream (9);
• k) passing the hydrogen lean residue stream (9) through a carbon dioxide selective membrane separation unit (10) to form a carbon dioxide enriched permeate stream (11) with the remaining components in the hydrogen lean residue stream (9) forming a carbon dioxide depleted residue stream (12);
• and
• I) optionally compressing the hydrogen rich permeate stream (8) in a second compressor (13) and recycling the hydrogen rich permeate stream (8) for use as a supplemental feed stream in the steam methane reformer (19), the water gas shift reactor (21) or the process unit (0) or as a fuel for the steam methane reformer (19), recycling the carbon dioxide enriched permeate stream (11) to the process stream (1) prior to the compressor (2) or within the compressor (2) between stages of compression or optionally compressing the carbon dioxide enriched permeate stream (11) and recycling the carbon dioxide enriched permeate stream (11) to be used in the carbon dioxide separation unit (4) and recycling the carbon dioxide depleted residue stream (12) to be used as a supplemental feed stream for the pre-reformer (17) or the steam methane reformer (19) or as both a fuel and a feed stream in the present process or in other processes.