Patent ID: 8303930

Claim:
A process for recovering high purity gaseous hydrogen and high purity gaseous carbon dioxide, the process comprising the steps of: a) generating a hydrogen rich effluent that also contains carbon monoxide, carbon dioxide, methane and water from one or more hydrocarbon feed gases in a steam hydrocarbon reformer; b) treating the hydrogen rich effluent in a water gas shift reactor in order to further enrich the hydrogen rich effluent and also increase the carbon dioxide content in the hydrogen rich effluent thereby obtaining a water shift effluent, wherein said water shift effluent has a temperature of less than 50C and a pressure of between 200 psig and 600 psig; c) introducing the water shift effluent into a hydrogen pressure swing adsorption unit having two or more beds that contain one or more adsorbents that allow for the recovery of a high purity gaseous hydrogen stream and the adsorption of carbon dioxide, carbon monoxide, methane, water and the remaining hydrogen onto the adsorbents in the two or more beds; d) withdrawing the high purity gaseous hydrogen from the hydrogen pressure swing adsorption unit and passing this stream on for further use; e) depressurizing the two or more beds that contain the adsorbent in order to release the carbon dioxide, carbon monoxide, methane, water and the remaining hydrogen adsorbed thereto and produce a hydrogen pressure swing adsorption tail gas; f) withdrawing the hydrogen pressure swing adsorption tail gas from the hydrogen pressure swing adsorption unit and with the aid of a blower and introducing the hydrogen pressure swing adsorption tail gas into a vacuum swing adsorption unit that contains one or more beds of an adsorbent selected from zeolites, silica gels, activated alumina or mixtures thereof that are selective for carbon dioxide thereby allowing for the recovery of a high purity gaseous carbon dioxide by adsorption to the adsorbent and a first carbon dioxide lean gas stream that contains methane, hydrogen, carbon monoxide and the remaining carbon dioxide; g) allowing the first carbon dioxide lean gas stream to pass from the vacuum swing adsorption unit where it is recycled to the steam hydrocarbon reformer where it can used as makeup fuel gas in the steam hydrocarbon reformer; and h) vacuum desorbing the carbon dioxide from the adsorbent in the vacuum swing adsorption unit in order to produce a high purity gaseous carbon dioxide stream that may be passed on for further use.