Impacts on the Emissions Monitoring System (OBD) Due to the Use of Biodiesel and Higher NOx Emissions 2011-36-0101
Due to the independent operation of the NOx (Nitrogen Oxides) aftertreatment systems from the engine, the aim of the OBD system (OnBoard Diagnosis) is to guarantee the NOx and the Particulate Matter emissions stay within the emissions standards during all the vehicle useful life. In the case of heavy duty diesel vehicles, that use the SCR system (Selective Catalytic Reduction) as the NOx aftertreatment technology, the use of the NOx sensor in the exhaust pipe will be indispensable to control and to monitor the engine emissions.
In parallel with these advances in the engine embedded technology for reduction of emissions, it is also advancing the use of biofuels such as biodiesel, which appears as a renewable and clean alternative because it is derived from organic mass and results lower concentrations of some pollutant gases in the exhaust gas in comparison to the fossil fuel. But recent studies are indicating that the NOx is the unique gas that results higher concentration in the exhaust gas when the engine using biodiesel instead of conventional diesel.
Thus, using biodiesel, the vehicle will present a higher tendency of mistakes on emissions diagnosis by the OBD system, penalizing the vehicle user and damaging the progress of incentives for the biodiesel program.
The subject of this paper is to study the operation of the SCR aftertreatment system when using conventional diesel and biodiesel, to explore the characteristics of the NOx sensor and to analyze its behavior of NOx detection in real applications with the engine using biodiesel, presenting adequate solutions to adapt the entire system.