Simulating the Effect of Diesel Exhaust Gas Properties on NOx Conversion Efficiency of a Selective Catalytic Reduction System

Selective Catalytic Reduction (SCR) is one of the most efficient technologies to reduce NOx emissions in the exhaust gas of diesel engines. In the SCR system, urea solution is injected into the hot exhaust gas, chemically decomposed to ammonia as a reducing agent that reacts with NOx to form N-2 and H2O over the catalyst surface. However, for a specific SCR system, the NOx conversion efficiency depends on many factors such as exhaust gas temperature, exhaust gas flow rate, and ratio of NO2/NOx. This study aims to investigate the effect of some properties of diesel exhaust gas on the NOx conversion efficiency of an SCR system. The SCR system is designed for bus diesel engines and is modeled by using AVL Boost software. The results show that the NOx conversion efficiency increases as the temperature of the catalyst increases from 50 to 450 degrees C. The NOx conversion efficiency is inversely proportional to the exhaust gas flowrate. When the NO2/NOx ratio increases from 0 to 50% the NOx conversion efficiency increases gradually. Increasing the NH3/NOx ratio increases the NOx conversion efficiency, and the optimal value of the NH3/NOx ratio is 1.