Multilayer ceramic amperometric (MCA) NOx-sensors using titration principle

Abstract

The removal of nitrogen oxides from exhaust emissions of combustion processes containing substantial levels of oxygen is a challenging venture, especially in lean burn spark ignition and diesel engines for automobiles, trains and ships, and coal/oil-fired power stations. We have developed multilayer ceramic amperometric (MCA) NOx-sensors made of an oxygen ion conducting ceramic like yttrium stabilised zirconia using a new operation mode, the titration mode, which measures the consumption of hydrogen reducing NOx. The operation temperature is around 800°C which is controlled by an online impedance measurement. The integrated platinum heater is driven by a pulse width modulation. MCA NOx-sensors performed well under static and dynamic conditions. The titration mode was compared to a standard reduction mode where the nitrogen oxides are directly reduced electrochemi-cally. Both operation modes show O2-cross sensitivity.