Compliance with increasingly stringent regulatory requirements for the level of pollutant emissions from fossil fuels as a source of heat source in power engineering requires constant improvement of boiler-furnace equipment and energy equipment in general. The paper presents the results of a numerical study of the process of combustion, generation and conversion of gas pollutants for the theoretical justification and industrial verification of the possibility of creating a multi-fuel low-temperature swirl furnace that meets the requirements of environmental legislation. On the basis of the developed methods, algorithms and computer methods, a quantitative assessment of nitrogen oxide emissions during the technical re-equipment of the BKZ-210–140f boiler at the Kirov TPP-4 was performed, and their comparison with the experimental data obtained after the reconstruction was carried out. Calculated and industrial studies have proved that is possible to create and efficiently operate a multi-fuel low-temperature swirl furnace.