Research on Urea-related Deposit in the Exhaust Pipe of SCR System

Abstract

At present, numbers of commercial vehicles equipped with SCR system have been observed to generate deposit on exhaust pipe wall after operation for a certain time. Deposits can be hardly dissolved in water and decomposed by heating. Once formed up, deposits are so hard to be cleaned that bringing significant influence on the SCR system and engine. In this paper, deposits in exhaust pipes for automotive diesel engines were studied by thermo-gravimetric (TG) analysis method. According to the TG results, we can see that inhibition of the polymerization reaction of HNCO to generate high polymer is the basic way to avoid deposits. Finally, we solve the deposit problem by leading the injector forward 2600 mm and wrapping the whole exhaust pipe with heat preservation material.