Air Products and Chemicals, Inc.

Joseph P Bushinsky

David M Nicholas

Ravi Kumar

Wilbur C Kratz

Jeffrey Alan Hopkins

Thomas M Roden

Shoou-I Wang

Stephen P Goff

Nitin Madhubhai Patel

David Edward Guro

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 is 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.

Production of ammonia synthesis gas

A method is disclosed for producing ammonia synthesis gas by splitting a methane stream, combusting a portion of the methane with steam and oxygen-enriched air, converting a second portion of the methane with steam in a reformation heated by the combustion products of the first portion and combining the two portions for the water gas shift reaction followed by adsorptive separation of contained carbon dioxide.

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.

Adsorptive process for recovering nitrogen from flue gas

Substantially pure hydrogen and high purity carbon monoxide are produced and recovered from a methane-rich gas composition, such as natural gas, by subjecting such composition to steam reforming in a first stage at relatively mild conditions, followed by secondary oxidative reforming of the thus obtained primary reformate effecting conversion of residual methane therein to carbon oxides. The secondary reformate, comprised chiefly of hydrogen, CO, and CO.sub.2, is subjected to a novel sequence of operations for separation of these individual components. CO.sub.2 is first removed by solvent absorption, followed by selective adsorption for separation of CO from the CO.sub.2 -freed gas mixture with attendant recovery of hydrogen product of 98.sup.+ % purity as an unsorbed effluent. Trace to small amounts of undesired carbon monoxide in the thus recovered hydrogen product can be converted by catalytic methanation.

Production of hydrogen and carbon monoxide

Crude ammonia synthesis gas is obtained by primary steam reforming of a hydrocarbon gas mixture rich in methane, such as natural gas, followed by secondary reforming of the primary reformate with added air and shift conversion of the contained CO to CO.sub.2. The shift conversion product is first freed of contained CO.sub.2 by selective absorption in a novel PSA unit having an integrated B section for removal of remaining impurities such as carbon monoxide and methane, thereby providing as product a gas stream comprised of hydrogen and nitrogen in approximate 3:1 molar ratio accompanied by a small amount or argon derived from the air stream used in the secondary reforming step. Alternative embodiments are disclosed for removal of CO from the gas stream, before its entry into the NH.sub.3 conversion operation; any residual CO that might have slipped thorugh the absorbent bed of the B section is converted to CH.sub.4.

Purification of ammonia syngas

Separation and individual recovery of high purity hydrogen and carbon monoxide from a mixed gas stream containing these compounds in association with carbon dioxide and one or more minor components such as particularly methane, is achieved by pressure swing adsorption to remove contained carbon dioxide from the charged gas, and further treatment of the CO.sub.2 -freed gas product by a sequence of steps utilizing (a) pressure swing adsorption and (b) selective permeation through a series of semi-permeable membranes, which steps (a) and (b) are carried out in either order of sequence.

Production and recovery of hydrogen and carbon monoxide

Hydrogen and carbon monoxide are each separately recovered in high yield from a multicomponent gas stream containing these compounds together with carbon dioxide and a zero to minor amount of one or more gaseous components from the group consisting of nitrogen, methane, water vapor and C.sub.2 -C.sub.6 hydrocarbons, by a process wherein the multicomponent gas stream, such as that obtained by steam methane reforming, is initially treated in a pressure swing adsorption unit to remove water and CO.sub.2, and the obtained effluent freed of CO.sub.2 and water is then further subjected to (1) cryogenic fractionation to condense CO and to (2) hydrogen purification by selective adsorption (in either order) to recover high purity carbon monoxide and essentially pure hydrogen. The CO.sub.2 -laden adsorbent is regenerated by purging with a H.sub.2 O and CO.sub.2 -free waste gas stream from the hydrogen purification adsorbent bed or from the cryogenic fractionation or from both of these.

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Allentown, PA, United States of America

Joseph P Bushinsky