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Novel Application of Air Separation Membranes Reduces Engine NOx Emissions

Alternative to Exhaust Gas Recirculation that involves the nitrogen enrichment of intake air.

Argonne National Laboratory

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	Schematic representation of the air separation process through a membrane module</p>

Schematic representation of the air separation process through a membrane module

Technology Marketing Summary

Nitrogen oxide (NOx) emissions pose risks to human health, and so they need to be reduced. One very effective tool for reducing engine in-cylinder temperature and, hence NOx emissions (NOx is a strong function of temperature), is Exhaust Gas Recirculation (EGR). However, EGR has a number of inherent disadvantages that limit its long-term benefits: combustion contamination, greater control system complexity, application variability, materials and durability, decreased fuel economy, lubricant contamination, and increased PM emissions. To overcome these disadvantages, researchers at Argonne National Laboratory have developed an alternative to EGR that involves the nitrogen enrichment of intake air. Argonne pioneered the application of membranes in internal combustion engines. Argonne tested this technology on several platforms, including locomotives, vehicles, and power generators.


Nitrogen enrichment of intake air is an effective alternative to EGR without the imposed undesired consequences. Argonne researchers are using this mature technology, which involves selective permeation of gases using an Air Separation Membrane (ASM). Another method of reducing NOx emissions is achieved by after-treatment of engine exhaust. Depending on the combustion recipe adopted (rich burn or lean), different types of catalysts are implemented. For example, current diesel engines employ Urea SCR systems, while spark-ignited natural gas power generators employ three-way catalysts. After-treatment modules add significant cost to the system, compared to ASMs. Introduction of inert diluents, like nitrogen, into a fuel-air mixture slows down the reaction rates of participating chemical species, which eventually results in lower combustion temperatures and, hence, lower NOx. Since ASMs produce oxygen-rich and nitrogen-rich streams by passing air through them, the nitrogen-rich stream can be introduced into the engine to control NOx. Another major advantage of this ASM application is that existing engines can be retrofitted. The results of this work have triggered more in-depth study of ASM and its applicability to various engine configurations for both stationary and transportation applications. 


Using this technology could reduce NOx emissions by 70%, with just a 2% nitrogen enrichment of intake air. Extremely low NOx emissions can be realized by using membranes to improve air quality and to meet EPA standards. The ability to reduce combustion temperature is a related benefit. In addition, the technology is attracting international interest — major engine manufacturers in India have approached Argonne to consider potential collaboration and licensing agreements for our patent.

Applications and Industries
  • Automotive industry
  • Power Generation
  • Locomotives
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 7,455,046
Nitrogen enriched combustion of a natural gas internal combustion engine to reduce NO.sub.x emissions
A method and system for reducing nitrous oxide emissions from an internal combustion engine. An input gas stream of natural gas includes a nitrogen gas enrichment which reduces nitrous oxide emissions. In addition ignition timing for gas combustion is advanced to improve FCE while maintaining lower nitrous oxide emissions.
Argonne National Laboratory 11/25/2008
Patent 5,526,641
NO.sub.x reduction method
A method of reducing oxides of nitrogen (NO.sub.X) in the exhaust of an internal combustion engine includes producing oxygen enriched air and nitrogen enriched air by an oxygen enrichment device. The oxygen enriched air may be provided to the intake of the internal combustion engine for mixing with fuel. In order to reduce the amount of NO.sub.X in the exhaust of the internal combustion engine, the molecular nitrogen in the nitrogen enriched air produced by the oxygen enrichment device is subjected to a corona or arc discharge so as to create a plasma and as a result, atomic nitrogen. The resulting atomic nitrogen then is injected into the exhaust of the internal combustion engine causing the oxides of nitrogen in the exhaust to be reduced into nitrogen and oxygen. In one embodiment of the present invention, the oxygen enrichment device that produces both the oxygen and nitrogen enriched air can include a selectively permeable membrane.
Argonne National Laboratory 06/18/1996
Patent 6,055,808
Method and apparatus for reducing particulates and NO.sub.X emissions from diesel engines utilizing oxygen enriched combustion air
An emission control system for reducing total particulates and NO.sub.X emissions from the exhaust of a diesel engine includes an air supply system that supplies oxygen enriched air to an air intake of the engine. The air supply system may include a selectively permeable air separating membrane device for producing the oxygen enriched air. In order to effectively utilize the increase in the concentration level of oxygen in the intake air, the amount of fuel being supplied to the diesel engine also is increased at a minimum in proportion to the increased concentration level of oxygen in the intake air. The increase in the amount of such fuel being supplied to the diesel engine can be adjusted by an electronic fuel injection system used on such diesel engines. In addition, the electronic fuel injection system is used to retard the injection timing of the engine.
Argonne National Laboratory 05/02/2000
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
ANL-IN-92-066, 95-152, 98-061, 03-120, PrototypeAvailable02/05/201302/05/2013

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To: Elizabeth Jordan<>