Patent ID: 9617891
Date: 2017-04-11
CPC Classifications: F01N,Y02A,Y02T

Claim:
1. A urea backflow prevention apparatus of selective catalytic reduction (SCR) in an SCR system which injects a urea solution into an exhaust pipe, the urea backflow prevention apparatus comprising: a urea tank configured to store the urea solution; a nozzle configured to be installed in the exhaust pipe to inject the urea solution into the exhaust pipe; a supply pump configured to pump the urea solution; a suction line configured to connect the urea tank to the supply pump to supply the urea solution stored in the urea tank to the supply pump; a pressure line configured to connect the supply pump to the nozzle to deliver the urea solution pumped by the supply pump to the nozzle; a return line configured to connect the supply pump to the urea tank to return un-injected urea solution back to the urea tank; a backflow prevention line configured to connect the pressure line to the return line, wherein the backflow prevention line keeps pressures of the pressure line, the supply pump directly connected to the pressure line and the suction line indirectly connected to the pressure line equal to an atmospheric pressure after an operation of the SCR system ends; and a shut-off valve disposed on the backflow prevention line to open or close the backflow prevention line, wherein the shut-off valve opens the backflow prevention line after the operation of the SCR system is terminated and a urea collection is completed by operating the supply pump in a reverse direction.