US Patent Application No. 13/364,531, Engine aftertreatment system with exhaust lambda control




This technology is about an aftertreatment device for reducing nitrogen oxides (NOx), particulate matter (PM), hydrocarbon (HC), and carbon monoxide (CO) generated by a compression-ignition (CI) engine. In this device, lean exhaust air generated in the CI engine is converted to rich exhaust air, and energy used for the conversion is recycled using an energy recovery device. The result rich exhaust air then pass through an oxidation catalyst, where NOx is reduced with CO and HC. In regenerating a DPF, a pre-heater is positioned upstream from the energy recovery device for momentarily increasing dosing fuel temperature above a light-off temperature of a DOC when exhaust air temperature is low. After the DOC temperature is above its light-off temperature with dosing fuel being oxidized therein, the pre-heater is turned off. The exotherm released in oxidizing the dosing fuel can be partially recovered with an energy recovery device.

Uniqueness and benefits of this technology:
1. A device uses oxidation catalyst for reducing NOx emitted from a lean combustion engine. In the device, oxygen is removed first, and then NOx is reduced by HC and CO in exhaust gas.
2. In regenerating a DPF, two heating devices are used. One is a DOC in which dosing fuel is oxidized and exotherm is generated. The other one is a pre-heater, which is only used when exhaust temperature is low for lighting off the DOC.
3. Energy recovery devices are used in the after-treatment system for recovering heat energy released in oxidizing dosing fuel.


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