Characteristics of deposit formation in scr system for varying temperature and flow rate of exhaust gases -a study using xrd

To mitigate the environmental pollution due to NOx emitted from exhaust of diesel engines, automobile manufacturers are adopting Selective Catalytic Reduction (SCR) system for modern automobiles. The reducing agent NH3 is generated by spraying Urea Water Solution (UWS). When exhaust temperature is low, the overdosing of UWS is necessary, but it results in deposits of urea and its by-products. The temperature and Reynolds number have significant effects on ammonia generation and urea deposits. In the present work, investigation is done for deposit formation considering temperature and flow rate as variables. The results show that the crystallanity of urea deposits tests done at open reactor vessel and in hot air test bench have shown difference with quantity and types of deposits. However, EDAX indicates urea as a major constituent in deposits at low exhaust temperatures.