| abstract |
A method of producing a carbon dioxide product stream (756) from a synthesis gas stream (18) formed within a hydrogen plant (1) having a synthesis gas reactor (10), a water-gas shift reactor (14), located downstream of the synthesis gas reactor to form the synthesis gas stream (18) and a hydrogen pressure swing adsorption unit (20) to produce a hydrogen product (22) recovered from the synthesis gas stream. In accordance with the invention, the carbon dioxide is separated from the synthesis gas stream in a vacuum pressure swing adsorption system (80) to produce a hydrogen-rich gas stream (76) and a crude carbon dioxide stream (82) and then purifying the crude carbon dioxide stream by a sub- ambient temperature distillation process thereby to produce the carbon dioxide product (756). A hydrogen synthesis gas feed stream (78) to the hydrogen pressure swing adsorption unit is formed at least in part from the hydrogen- rich stream. |