Patent ID: 8394174
Filing Date: 2013-03-12
Classification: C01B,Y02C

Abstract:
1. A process for recovering high purity gaseous hydrogen and high purity gaseous carbon dioxide comprising: a) generating a hydrogen rich effluent that also contains carbon monoxide, carbon dioxide, methane and water from one or more hydrocarbon feeds and 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 gas shift effluent; c) introducing the water gas 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 introducing the hydrogen pressure swing adsorption tail gas into a compressor in order to compress the hydrogen pressure swing adsorption tail gas; g) introducing the compressed hydrogen pressure swing adsorption tail gas into a carbon dioxide pressure swing adsorption unit that contains one or more beds of an adsorbent selected from activated carbon, silica gels, one or more zeolites or any combination thereof thereby allowing for the recovery of a secondary high purity gaseous carbon dioxide stream by adsorption of the carbon dioxide to the adsorbent and a secondary carbon dioxide lean gas stream; h) allowing the secondary carbon dioxide lean gas stream to pass from the carbon dioxide pressure swing adsorption unit into a membrane separation unit that includes one or more modules, each module having one or more membranes that are highly selective for hydrogen and carbon dioxide, said membranes having a residue side and a permeate side, the membrane allowing for the retention of methane and carbon monoxide to form a first membrane stream on the residue side of the membrane and the passing of carbon dioxide and hydrogen to the permeate side to form a second membrane stream on the permeate side of the membrane; i) recycling the first membrane stream to the feed gas of the steam hydrocarbon reformer unit with the aid of a second compressor or to the steam hydrocarbon reformer as makeup fuel; j) optionally recompressing the second membrane stream in a third compressor and recycling this compressed second membrane stream to the water gas shift effluent to be introduced into the hydrogen pressure swing adsorption unit or passing the second membrane stream to the hydrogen pressure swing adsorption tail gas to be compressed before being injected into the carbon dioxide pressure swing adsorption unit; and k) removing the carbon dioxide that is adsorbed onto the one or more beds of the carbon dioxide pressure swing adsorption unit by vacuum decompressing the one or more beds.