NOx control via carbon sorbents and selective NOx recirculation

Andre  Boehman, Pennsylvania State University

NOx Control via Carbon Sorbents and Selective NOx Recirculation Treatment of NOx in lean exhausts has focused on either catalytic reduction or trapping combined with reduction. Some previous work by Daimler Benz has considered the possibility of trapping NOx and destroying it through recirculation of a concentrated NOx stream into the combustion chamber. However, trap materials they considered were not effective in exhausts containing sulfur. Recent developments in carbon sorbents have provided materials that can adsorb both NO and NO2, and competitively adsorb SO2 without adverse impact on NOx sorption capacity. Present work is focusing on incorporation of the carbon based sorbent in an on-engine NOx control system in combination with selective NOx recirculation in a diesel engine. Both the dynamics of sorption and desorption and the physical and chemical processes affecting the recirculated NOx are important topics for simulation. The dynamics of sorption and desorption may have a significant impact on the required carbon trap size and its on-vehicle collection efficiency. Modeling of the fate of recirculated NOx through the premixed and mixing controlled phases of combustion is important in understanding how to maximize the NOx destruction efficiency, and to develop injection strategies for the recirculated NOx.

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