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Use of ITM Membrane in Ammonia Syngas Production

IP.com Disclosure Number: IPCOM000019407D
Publication Date: 2003-Sep-12
Document File: 2 page(s) / 72K

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Abstract

Oxygen can be recovered from air at high temperatures by passing hot compressed oxygen-containing gas, preferably air, over non-porous, mixed-conducting ceramic membranes. These membranes, known in the art generically as ion transport membranes, utilize a pressure differential across the membrane to cause oxygen ions to migrate through the membrane. In addition to conducting the oxygen ions, these mixed-conductors allow electrons to move in the opposite direction for the formation of the oxygen ions on the feed side and oxygen molecules on the permeate side of the membrane. Membranes can be fabricated as tubes or flat plates that are arranged in modules for efficient contacting with hot compressed air. High-purity oxygen permeate and nitrogen-enriched non-permeate products are withdrawn from the modules. A class of ITM membranes that are not mixed-conducting materials can also be used in this application. In these cases, the oxygen ions are driven through the membrane by applying an external voltage potential to the membrane. A comprehensive review of ion transport membranes is given by J. D. Wright and R. J. Copeland in Report No. TDA-GRI-90/0303 prepared for the Gas Research Institute, September 1990.

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Use of ITM Membrane in Ammonia Syngas Production        

Oxygen can be recovered from air at high temperatures by passing hot compressed oxygen-containing gas, preferably air, over non-porous, mixed-conducting ceramic membranes. These membranes, known in the art generically as ion transport membranes, utilize a pressure differential across the membrane to cause oxygen ions to migrate through the membrane. In addition to conducting the oxygen ions, these mixed-conductors allow electrons to move in the opposite direction for the formation of the oxygen ions on the feed side and oxygen molecules on the permeate side of the membrane. Membranes can be fabricated as tubes or flat plates that are arranged in modules for efficient contacting with hot compressed air. High-purity oxygen permeate and nitrogen-enriched non-permeate products are withdrawn from the modules. A class of ITM membranes that are not mixed-conducting materials can also be used in this application. In these cases, the oxygen ions are driven through the membrane by applying an external voltage potential to the membrane. A comprehensive review of ion transport membranes is given by J. D. Wright and R. J. Copeland in Report No. TDA-GRI-90/0303 prepared for the Gas Research Institute, September 1990.

ITM membrane technology has potential applications in the ammonia production process. The initial steps in ammonia production take place in "primary" and "secondary" reformers. In the primary reformer, a natural gas feed stock is mixed with steam and reacts over a catalyst, yielding a synthesis gas mixture of primarily hydrogen and carbon monoxide. A fuel, such as natural gas, is combusted with air in a furnace to supply the heat for the endothermic reforming reactions. An additional reforming step in the secondary reformer completes the reaction by reacting the primary reformer synthesis gas, forced air, and steam over a second catalyst. The air supply not only sustains the reaction but also supplies the nitrogen necessary for ammonia synthesis. The secondary reformer effluent comprises a mixture of nitrogen, hydrogen, carbon monoxide, carbon dioxide, and steam suitable for further processing.

The ITM membrane will separate a heated air stream into an oxygen product and a nitrogen-rich byproduct. The oxygen will be used in the primary reformer to effect more efficient combustion of the fuel gas consumed by the reformer burners. This will allow the ammonia producer to maintain des...