Adsorptive process for recovering nitrogen from flue gas

摘要

Nitrogen is economically recovered from the flue gas evolved in a hydrocarbon steam reforming furnace by hydrogenation of free oxygen therein and removal of carbon dioxide and other minor impurities from the flue gas by pressure swing adsorption with recovery of high purity nitrogen as unsorbed effluent. The process is utilized to highest advantage in the production of ammonia syngas wherein natural gas or other hydrocarbon feed is subjected to steam reforming in a fuel-fired furnace. The nitrogen obtained by purification of the flue gas is combined with the purified hydrogen separated from the reformate providing the syngas for conversion to ammonia. In a preferred embodiment, the steam reforming is carried out in two stages, the first stage being performed in a conventional fuel-fired steam reforming furnace to which a major portion of the fresh hydrocarbon feed is charged. The hot effluent from this first reforming stage is employed as the heating medium to support reforming of the remaining minor portion of the fresh feed by heat exchange therewith.