FIELD: cleaning of combustion products; applicable in heat and power engineering, chemical, metallurgical and other industries as applied to equipment provided with electrostatic precipitators. SUBSTANCE: ammonia or compounds liberating ammonia are introduced into high-temperature zone in amount exceeding the needed one for reducing oxides to provide for supply of ammonia concentration at inlet of electrostatic precipitator within the ranges needed in mixture containing in combustion products of sulfur trioxide for conditioning of gases subject to cleaning before electrostatic precipitator. With volumetric content in combustion products before electrostatic precipitator of sulfur trioxide of less than 3 ppm, it is additionally introduced into high- temperature zone, and its content is maintained at inlet of electrostatic precipitator within 3-70 ppm with ammonia-sulfur trioxide mole ratio of 0.3-1.5. EFFECT: reduced overall dimensions and costs of electrostatic precipitators. 4 cl
