Catalytic selective reduction system with urea promotion, for diesel engine exhaust gas, has good cold start performance by upstream injection of electrically preheated aqueous solution in enhanced spray dispersion

摘要

Selective catalytic reduction system for purification of internal combustion engine exhaust gases, particularly diesel exhaust, comprises a feed pump (22) for transferring aqueous urea solution from a reservoir (21), through an electrical heater (23, 34) for preheating or even superheating, and a nozzle (24) for injecting it as finely dispersed spray into the gases upstream of a catalyst unit (26). An independent claim is included for injecting preheated aqueous urea solution as finely dispersed spray into exhaust gases upstream of a catalyst unit. The solution is 32.5% aqueous urea, preheated to 10-200[deg]C. The feed pump is required to provide a delivery pressure sufficient to prevent premature boiling of superheated solution in the heater.