Method for the cleaning of flue gases from nitrogen oxides

This invention relates to the field of cleaning of flue gases and can be used for reducing nitrogen oxide emissions with combustion products from fuel burning units by means of high-temperature selective non-catalytic reduction of nitrogen oxides with the use of carbamide. The method of selective non-catalytic reduction of nitrogen oxides comprises the feeding of a previously prepared gas-vapor reducing mixture into the gas flue of a fuel burning unit at a temperature of the gases to be cleaned being from 700 to 1200°C, the gas-vapor reducing mixture being obtained in a high-velocity reactor, connected to the gas flue, during a time period of 0.5 to 5 sec by means of bringing a carbamide water solution into contact with superheated vapor under the pressure of 3 to 10 atm. The concentration of the carbamide water solution is from 20 to 40 by weight; the temperature of the superheated vapor is from 200 to 400°C; and water vapor, air, or flue gases are used as a carrier gas which arranges the reducing mixture within a flow of the gases to be cleaned uniformly. The invention makes it possible to simplify the process flowsheet of cleaning waste gases from nitrogen oxides, to increase the cleaning efficiency within a wide temperature range of the combustion products to be cleaned and also to considerably decrease the amount of the secondary pollutant, i.e. ammonia, in the cleaned gases.