Deposit Formation in Urea-SCR Systems

Formation of urea injection related deposits in a heavyduty urea-SCR system was studied using an engine lab setup. The exhaust system was instrumented with thermocouples to track temperature changes caused by the liquid spray. Impact of operating parameters (exhaust and ambient temperature, urea solution injection rate) and system design modification (insulation, wiremesh insert) on the temperature profiles and deposit quantities was studied. Deposits were found in all tests conducted under typical exhaust temperatures. Deposition rate increased with lower exhaust and ambient temperature, and with higher injection rate. Mixer insulation and wiremesh upstream of the mixer reduced the deposits.