Patent ID: 8397491

Claim:
An apparatus for introducing a reducing agent liquid into an exhaust gas of a combustion system, comprising: a storage tank storing a volume of reducing agent liquid and a volume of reducing agent gas, a delivery means for delivering the reducing agent liquid into the exhaust gas, a feed line disposed between the storage tank and the delivery means, a conveying pump disposed in the feed line and configured to convey the reducing agent liquid in a conveying direction from the storage tank to the delivery means, a venting line connecting the storage tank to the feed line at a location upstream of the conveying pump, the venting line opening into the storage tank at a venting line opening communicating with the volume of reducing agent gas in the storage tank, and an actuable venting valve disposed along the venting line and movable between an open and a closed position, wherein the delivery means is connected by a return line to the storage tank, and an actuable shut-off valve is disposed in the return line, the return line opening into the storage tank at a return line opening communicating with the volume of reducing agent gas in the storage tank, wherein during an emptying operation, the venting valve and the shut-off valve are both arranged in an open position to form an open circuit to empty the feed line of liquid reducing agent gas by a flow of the reducing agent gas facilitated by the conveying pump, the open circuit allowing a flow of the reducing agent from the storage tank, through the venting line via the open venting valve, through the conveying pump, through the return line and back into the storage tank via the open shut-off valve, and through the storage tank via the venting line opening and return line opening in the storage tank.