Patent ID: 8371113

Claim:
A mixing device for mixing urea with a gas, said urea being dissolved in a fluid, the device comprising a urea inlet and a gas inlet for feeding respectively urea and the gas into a mixing chamber of the mixing device, and an outlet for outlet of the mix of urea and gas from the mixing chamber, wherein at least the gas inlet for feeding gas into the mixing chamber is designed so that crystals deposited on selected surfaces of said inlet are removed from the surfaces during use of the mixing device, wherein the mixing device further comprises a valve in the gas inlet, and wherein removal of the crystals on selected surfaces of the gas inlet is provided by the valve comprised in the gas inlet, said valve being adapted to perform a reciprocating movement while the valve is pressurized so as to loosen urea crystals deposited in the mixing device, wherein the reciprocating movement is a vibration of the valve induced when the valve is pressurized and said vibration of the valve removes the deposited crystals.