Patent ID: 8813475

Claim:
A method for preventing choking of a urea injection nozzle in an after-run operation on an Selective Catalytic Reduction (SCR) system which supplies urea stored in a urea tank through a supply module, a urea injection nozzle and a urea line connecting the supply module and the urea injection nozzle, the method for preventing choking of a urea injection nozzle comprising: comparing a supply pressure within the supply module with a first predetermined pressure (Pa); open controlling the urea injection nozzle when the supply pressure in the supply module is higher than the first predetermined pressure (Pa) or repeating open/close controlling the urea injection nozzle when the supply pressure in the supply module is lower than the first predetermined pressure (Pa); applying pressure equilibrium which recovers pressure in the supply module; and stopping the after-run operation when the applying pressure equilibrium is completed.