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	Lean and rich combustion characteristics of LNT desulfation
	Fast lean-rich switching to achieve LNT desulfation

Because diesel emission standards are becoming  increasingly stringent, exhaust aftertreatment components have become essential parts of new engine emission control technologies. Diesel particulate filters (DPFs) are a certainty for particulate matter (PM) control and lean NOx traps (LNTs) are very likely going to be used for NOx control in light-duty applications.

A program to study lean NOx trap desulfation control began at Southwest Research Institute (SwRI) in an effort to find ways to effectively manage sulfur poisoning in LNT. 

Approach

One of the key issues for LNT operation is sulfur poisoning. Lean-burning engine exhaust contains certain quantities of SOx derived from fuel and lubricating oil. SOx is preferentially adsorbed over NOx and forms stable sulfates with the LNT storage materials. As a result, the LNT performance gradually declines because fewer storage sites are available for NOx adsorption.

Outcome

To release sulfur from LNT and restore the NOx adsorption capacity, desulfation must be performed. It requires high LNT bed temperature and rich A/F ratio condition. Precise temperature control over the desulfation event is desired. The minimum effective desulfation temperature (~625°C) must be achieved and the maximum allowable temperature (~700°C) must not be exceeded. Fast lean/rich switching was used to achieve LNT desulfation.

For more information about our powertrain control capabilities, or how you can contract with SwRI, please contact Jayant Sarlashkar at jsarlashkar@swri.org or (210) 522-5506.

powertraincontroltech.swri.org

| Engine and Vehicle R&D Department | Engine, Emissions & Vehicle Research Division | SwRI Home |

Southwest Research Institute^® (SwRI^®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

December 28, 2012