Cleaning exhaust gases from combustion installations

In an exhaust gas cleaning system having a reagent tank supplying a dilute urea solution, a metering system downstream of said reagent tank for metering the dilute urea solution, and a supply and atomization device for feeding the dilute urea solution to a plant for treating the exhaust gases, the improvement comprising:

• the plant comprises a pyrolysation channel, a mixing channel downstream of the pyrolysation channel and a reaction channel downstream of the mixing channel;
• the supply and atomization device comprises first pipe means for transporting compressed air and a second pipe means within said first pipe means for transporting the aqueous urea solution wherein the second pipe means is spaced from the first pipe means, and an atomization nozzle for receiving the compressed air and aqueous urea solution for atomizing same into the pyrolysation channel;
• at least two cross-flow mixers located in the mixing channel at a spaced distance from each other;
• at least two catalyst means located within the reaction channel at a spaced distance, said at least two catalyst means comprises a reduction catalyst followed by an oxidation catalyst;
• and
• means for feeding the exhaust gas to the pyrolysation channel wherein the exhaust gas mixes with the atomized aqueous urea solution to form a mixture which passes sequentially through the mixing channel and the reaction channel where it contacts the at least two cross-flow mixers and the at least two catalyst means respectively.