There are presented flue gas cleaning technology with application Selective Non-Catalytic Reduction (SNCR) Join Stock Company "All-Russian Thermal Engineering Institute" together with Russian State University of Oil and Gas named after I.M. Gubkin carried out practical approvement of the best available technology on pulverized-coal-fired boiler P50-R of generating unit with capacity 330 MWt Kashira GRES. Obtained results demonstrated that the implemented technology of SCNR provides for regulatory level of Nitrogen oxides in flue gas, and helps provide, when applicable, more high degree of gas cleaning.