CATALYST AMMONIA STORAGE MEASUREMENTS USING RADIO FREQUENCY SENSING

Conference · Mon Jul 24 00:00:00 EDT 2017

DOI:https://doi.org/10.1115/ICEF2017-3572· OSTI ID:1477841

Aguilar, Jonathan; Sappok, Alexander; Ragaller, Paul; Atehortua, Jean; Liu, Xiaojin; Bromberg, Leslie

Motivated by increasingly strict NO_x limits, engine manufactures have adopted selective catalytic reduction (SCR) technology to reduce engine-out NO_x below mandated levels. In the SCR process, nitrogen oxides (NO_x) react with ammonia (NH₃) to form nitrogen and water vapor. The reaction is influenced by several variables, including stored ammonia on the catalyst, exhaust gas composition, and catalyst temperature. Currently, measurements from NO_x and/or NH₃ sensors upstream and downstream of the SCR are used with predictive models to estimate ammonia storage levels on the catalyst and control urea dosing. This study investigated a radio frequency (RF) -based method to directly monitor the ammonia storage state of the SCR catalyst. This approach utilizes the SCR catalyst as a cavity resonator, in which an RF antenna excites electromagnetic waves within the cavity to monitor changes in the catalyst state. Ammonia storage causes changes in the dielectric properties of the catalyst, which directly impacts the RF signal. Changes in the RF signal relative to stored ammonia (NH₃) were evaluated over a wide frequency range as well as temperature and exhaust conditions. The RF response to NH₃ storage, desorption, and oxidation on the SCR was observed to be well-correlated with changes in the catalyst state. Calibrated RF measurements demonstrate the ability to monitor the adsorption state of the SCR to within 10 % of the sensor full scale. The results indicate direct measurement of SCR ammonia storage levels, and resulting catalyst feedback control, via RF sensing to have significant potential for optimizing the SCR system to improve NO_x conversion and decrease urea consumption.

• Research Organization: Filter Sensing Technologies, Inc., Malden, MA (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
• DOE Contract Number: EE0007214
• OSTI ID: 1477841
• Report Number(s): ICEF2017-3572
• Resource Relation: Conference: ASME 2017 Internal Combustion Engine Division Fall Technical Conference ICEF2017 , Seattle, Washington, USA, October 15-18, 2017
• Country of Publication: United States
• Language: English