Eaton Hybrid LNT/SCR System for 2010 NOx Emissions Requirements

22 August 2006

Eaton Corporation is developing an aftertreatment system that combines a fuel reformer catalyst with doser, Selective Catalytic Reduction system (SCR) and Lean NO_x Trap (LNT) technology to create an exhaust aftertreatment system capable of meeting 2010 EPA diesel emissions requirements without the need for a urea storage and injection system.

The fuel reformer generates a mixture of reformate gases (H₂ and CO) to improve LNT regeneration efficiency. During lean exhaust conditions, the LNT stores NO_x. During rich exhaust conditions (LNT regeneration), the LNT converts stored NO_x to nitrogen and produces ammonia.

This ammonia is stored by the downstream SCR catalyst and is used to convert remaining NO_x that slips past the LNT. NO_x reduction thus takes place in two stages: first by the LNT and second by the SCR catalyst, supported by ammonia from the LNT system.

The SCR NO_x reduction compensates for the loss in LNT performance over time due to fuel sulfur poisoning. Less frequent desulfation is required compared to an LNT-only system, according to Haoran Hu, who presented the system at DEER 2006.

Because the system does not require a urea storage and injection subsystem, it is also more space-efficient, according to Hu.

Essentially, Eaton has taken two NOx-reducing technologies, packaged them in a system that allows them to work together, and taken advantage of a naturally occurring chemical reaction to eliminate a major cost and logistics hurdle that exists for urea-based systems.

—Vishal Singh, Eaton marketing and business development manager for new technologies